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Pons

Gist

The pons is a crucial part of the brainstem (linking the cerebrum to the cerebellum and spinal cord) that manages unconscious functions like breathing, sleep cycles, and relaying sensory/motor signals, containing nerve pathways and nuclei for facial sensation, hearing, balance, and other head/face functions, and is also the name of a popular dictionary/translation service. 

The main function of the pons, a part of the brainstem, is to act as a relay station, connecting the cerebrum and cerebellum, and controlling vital functions like breathing, sleep cycles, facial expressions, and relaying sensory/motor signals for hearing, taste, balance, and movement coordination. It helps regulate arousal, fine motor control, and maintains equilibrium, essentially bridging communication between different parts of the brain and the body for essential processes.

Summary

Pons is the portion of the brainstem lying above the medulla oblongata and below the cerebellum and the cavity of the fourth ventricle. The pons is a broad horseshoe-shaped mass of transverse nerve fibres that connect the medulla with the cerebellum. It is also the point of origin or termination for four of the cranial nerves that transfer sensory information and motor impulses to and from the facial region and the brain. The pons also serves as a pathway for nerve fibres connecting the cerebral cortex with the cerebellum.

The pons, while involved in the regulation of functions carried out by the cranial nerves it houses, works together with the medulla oblongata to serve an especially critical role in generating the respiratory rhythm of breathing. Active functioning of the pons may also be fundamental to rapid eye movement (REM) sleep.

Details

The pons (from Latin pons, 'bridge') is the part of the brainstem that, in humans and other mammals, lies inferior to the midbrain, superior to the medulla oblongata, and anterior to the cerebellum.

The pons is also called the pons Varolii ('bridge of Variolus'), after the Italian anatomist and surgeon Costanzo Varolio (1543–1575). The pons contains neural pathways and nerve tracts that conduct signals from the brain down to the cerebellum and medulla, as well as pathways that carry the sensory signals up into the thalamus.

Structure

The pons in humans measures about 2.5 centimetres (0.98 in) in length. It is the part of the brainstem situated between the midbrain and the medulla oblongata. The horizontal medullopontine sulcus demarcates the boundary between the pons and medulla oblongata on the ventral aspect of the brainstem, and the roots of cranial nerves 6, 7, and 8 emerge from the brainstem along this groove. The junction of pons, medulla oblongata, and cerebellum forms the cerebellopontine angle. The superior pontine sulcus separates the pons from the midbrain. Posteriorly, the pons curves on either side into a middle cerebellar peduncle.

A cross-section of the pons divides it into a ventral and a dorsal area. The ventral pons is known as the basilar part, and the dorsal pons is known as the pontine tegmentum.

The ventral aspect of the pons faces the clivus, with the pontine cistern intervening between the two structures. The ventral surface of the pons features a midline basilar sulcus along which the basilar artery may or may not course. There is a bulge to either side of the basilar sulcus, created by the pontine nuclei that are interweaved amid the descending fibres within the substance of the pons. The superior cerebellar artery winds around the upper margin of the pons.

Vasculature

Most of the pons is supplied by the pontine arteries, which arise from the basilar artery. A smaller portion of the pons is supplied by the anterior and posterior inferior cerebellar arteries.

Development

During embryonic development, the metencephalon develops from the rhombencephalon and gives rise to two structures: the pons and the cerebellum. The alar plate produces sensory neuroblasts, which will give rise to the solitary nucleus and its special visceral afferent (SVA) column; the cochlear and vestibular nuclei, which form the special somatic afferent (SSA) fibers of the vestibulocochlear nerve, the spinal and principal trigeminal nerve nuclei, which form the general somatic afferent column (GSA) of the trigeminal nerve, and the pontine nuclei, which relay to the cerebellum.

Basal plate neuroblasts give rise to the abducens nucleus, which forms the general somatic efferent fibers (GSE); the facial and motor trigeminal nuclei, which form the special visceral efferent (SVE) column; and the superior salivatory nucleus, which forms the general visceral efferent fibers (GVE) of the facial nerve.

Nuclei

A number of cranial nerve nuclei are present in the pons:

* mid-pons: the principal sensory nucleus of trigeminal nerve (5)
* mid-pons: the motor nucleus for the trigeminal nerve (5)
* lower down in the pons: abducens nucleus (6)
* lower down in the pons: facial nerve nucleus (7)
* lower down in the pons: vestibulocochlear nuclei (vestibular nuclei and cochlear nuclei) (8)

Function

Functions of these four cranial nerves (5–8) include regulation of respiration; control of involuntary actions; sensory roles in hearing, equilibrium, and taste; and in facial sensations such as touch and pain, as well as motor roles in eye movement, facial expressions, chewing, swallowing, and the secretion of saliva and tears.

The pons contains nuclei that relay signals from the forebrain to the cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture.

Within the pons is the pneumotaxic center consisting of the subparabrachial and the medial parabrachial nuclei. This center regulates the transition from inhalation to exhalation.

The pons is implicated in sleep paralysis, and may also play a role in generating dreams.

Clinical significance

Central pontine myelinolysis is a demyelinating disease that causes difficulty with sense of balance, walking, sense of touch, swallowing and speaking. In a clinical setting, it is often associated with transplant or rapid correction of blood sodium. Undiagnosed, it can lead to death or locked-in syndrome.

Additional Information

Your pons is a part of your brainstem, a structure that links your brain to your spinal cord. It handles unconscious processes and jobs, such as your sleep-wake cycle and breathing. It also contains several junction points for nerves that control muscles and carry information from senses in your head and face.

Your pons is the second-lowest section of your brainstem, just above your medulla oblongata. It forms a key connection between your brain above it and your medulla oblongata and spinal cord below it.

Your pons is a key merging point for several of your cranial nerves, which are nerves with direct connections to your brain. Those nerve connections are vital, helping with several of the senses on or in your head, plus your ability to move various parts of your face and mouth.

Function:

What is the function of the pons?

Your pons is a part of your brainstem, which links your brain to your spinal cord. That makes your pons a vital section of your nervous system, providing a route for signals to travel to and from your brain. Several neurotransmitters in your pons facilitate brain function, particularly sleep.

Key jobs

Your pons handles several important jobs on its own.

* It influences your sleep cycle. Your pons sets your body’s level of alertness when you wake up.
* It manages pain signals. Your pons relays and regulates the signals that give you the sensation of pain from anywhere in your body below your neck.
* It works with other brain structures. Your pons is a key connection point to your cerebellum, another key part of your brain that handles balance and movement. It also works cooperatively with other parts of your brainstem that manage your breathing.

Cranial nerve connections

In addition, your pons contains several key junctions for four of your 12 cranial nerves, which are nerves that directly connect to your brain. Your cranial nerves (which use Roman numerals for their numbering) that connect to the pons are:

* Trigeminal nerve (Cranial Nerve V): Your trigeminal (try-gem-in-all) nerve provides the sense of touch and pain for your face and controls the muscles you use for chewing.
* Abducens nerve (CN VI): Your abducens (ab-DO-sens) nerve is one of the muscles that control eye movement. Damage to this nerve can cause double vision (diplopia).
* Facial nerve (CN VII): This nerve controls most of your facial expressions and your sense of taste from the front of your tongue.
* Vestibulocochlear nerve (CN VIII): Your vestibulocochlear (vest-ib-you-lo-co-klee-ar) nerve branches into your vestibular nerve and cochlear nerve. Your vestibular (vest-ib-you-lar) nerve gives you your sense of balance. Your cochlear (co-klee-ar) nerve gives you your sense of hearing.

How does it help with other organs?

Your pons helps with other organs by relaying sensory input and directly controlling some of your body’s unconscious processes. Those include your sleep-wake cycle and your breathing. Your ability to feel pain is also something your pons handles, and that sensation of pain can help you react to limit or prevent injuries.

Anatomy:

Where is the pons located?

Your pons is one of the lowermost structures in your brain, located near the bottom of your skull. It’s just above your medulla oblongata, which then connects to your spinal cord through the opening at the bottom of your skull.

What does it look like?

Your pons is a beige or off-white color. Its shape is much like the upper stem of a branch of cauliflower.

How big is it?

Pons’ dimensions are:

* Height: 1.06 inches tall (27 millimeters [mm]).
* Width: 1.49 inches (38 mm).
* Depth: 0.98 inches (25 mm).

What is it made of?

Like the rest of your brain and nervous system, your pons consists of various types of nervous system cells and structures. The nuclei (the plural term for “nucleus”) are nerves or clusters of brain cells that have the same job or connect to the same places.

Making up the nuclei are the following types of cells (with more about them below):

* Neurons: These cells make up your brain and nerves, transmitting and relaying signals. They can also convert signals into either chemical or electrical forms.
* Glial cells: These are support cells in your nervous system. While they don’t transmit or relay nervous system signals, they help the neurons that do.

Neurons

Neurons are the cells that send and relay signals through your nervous system, using both electrical and chemical signals. Each neuron consists of the following:

* Cell body: This is the main part of the cell.
* Axon: This is a long, arm-like part that extends outward from the cell body. At the end of the axon are several finger-like extensions where the electrical signal in the neuron becomes a chemical signal. These extensions, called synapses, lead to nearby nerve cells.
* Dendrites: These are small branch-like extensions (their name comes from a Latin word that means “tree-like”) on the cell body. Dendrites are the receiving point for chemical signals from the synapses of other nearby neurons.
* Myelin: This thin, fatty layer surrounds the axon of many neurons and acts as a protective covering.

Neuron connections are incredibly complex, and the dendrites on a single neuron may connect to thousands of other synapses. Some neurons are longer or shorter, depending on their location in your body and what they do.

Glial cells

Glial (pronounced glee-uhl) cells have many different purposes, helping develop and maintain neurons when you’re young and managing how the neurons work throughout your entire life. They also protect your nervous system from infections, control the chemical balance in your nervous system and create the myelin coating on the neurons’ axons. Your nervous system has 10 times more glial cells than neurons.

Medulla Oblongata

Gist

The medulla oblongata is the lowermost part of the brainstem, connecting the brain to the spinal cord and controlling vital involuntary functions like breathing, heart rate, and blood pressure, while also relaying sensory/motor signals and housing nuclei for several cranial nerves (IX-XII). It acts as a crucial relay station for nerve tracts, coordinates automatic reflexes (coughing, swallowing, vomiting), and is where motor signals cross over from one brain hemisphere to the opposite body side. 

The medulla oblongata's main function is controlling vital, involuntary life processes like breathing, heart rate, and blood pressure, while also managing reflexes such as swallowing, sneezing, coughing, and relaying signals between the brain and spinal cord. It acts as a crucial bridge, managing automatic functions essential for survival and coordinating basic bodily responses. 

Summary

The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (involuntary) functions, ranging from vomiting to sneezing. The medulla contains the cardiovascular center, the respiratory center, vomiting and vasomotor centers, responsible for the autonomic functions of breathing, heart rate and blood pressure as well as the sleep–wake cycle.[2] "Medulla" is from Latin, ‘pith or marrow’. And "oblongata" is from Latin, ‘lengthened or longish or elongated'.

During embryonic development, the medulla oblongata develops from the myelencephalon. The myelencephalon is a secondary brain vesicle which forms during the maturation of the rhombencephalon, also referred to as the hindbrain.

The bulb is an archaic term for the medulla oblongata. In modern clinical usage, the word bulbar (as in bulbar palsy) is retained for terms that relate to the medulla oblongata, particularly in reference to medical conditions. The word bulbar can refer to the nerves and tracts connected to the medulla such as the corticobulbar tract, and also by association to those muscles innervated, including those of the tongue, pharynx and larynx.

Details

Medulla oblongata is the lowest part of the brain and the lowest portion of the brainstem. The medulla oblongata is connected by the pons to the midbrain and is continuous posteriorly with the spinal cord, with which it merges at the opening (foramen magnum) at the base of the skull. The medulla oblongata plays a critical role in transmitting signals between the spinal cord and the higher parts of the brain and in controlling autonomic activities, such as heartbeat and respiration.

The medulla is divided into two main parts: the ventral medulla (the frontal portion) and the dorsal medulla (the rear portion; also known as the tegmentum). The ventral medulla contains a pair of triangular structures called pyramids, within which lie the pyramidal tracts. The pyramidal tracts are made up of the corticospinal tract (running from the cerebral cortex to the spinal cord) and the corticobulbar tract (running from the motor cortex of the frontal lobe to the cranial nerves in the brainstem). In their descent through the lower portion of the medulla (immediately above the junction with the spinal cord), the vast majority (80 to 90 percent) of corticospinal tracts cross, forming the point known as the decussation of the pyramids. The ventral medulla also houses another set of paired structures, the olivary bodies, which are located laterally on the pyramids.

The upper portion of the dorsal medulla forms the lower region of the fourth ventricle (a fluid-filled cavity formed by the expansion of the central canal of the spinal cord upon entering the brain). Similar to the spinal cord, the fourth ventricle is surrounded by white matter on the outside, with the gray matter on the inside. The dorsal medulla also is the site of origin for the last seven cranial nerves, most of which exit the medulla ventrally.

The medulla consists of both myelinated (white matter) and unmyelinated (gray matter) nerve fibres, and, similar to other structures in the brainstem, the white matter of the medulla, rather than lying beneath the gray matter, is intermingled with the latter, giving rise to part of the reticular formation (a network of interconnected neuron clusters within the brainstem). Neurons of the reticular formation play a central role in the transmission of motor and sensory impulses. Those in the medulla carry out complex integrative functions; for example, different functional centres specialize in the control of autonomic nervous activity, regulating respiration, heart rate, and digestive processes. Other activities of neurons in the medulla include control of movement, relay of somatic sensory information from internal organs, and control of arousal and sleep.

Injuries or diseases affecting the middle portion of the medulla may result in medial medullary syndrome, which is characterized by partial paralysis of the opposite side of the body, loss of the senses of touch and position, or partial paralysis of the tongue. Injuries or disease of the lateral medulla may cause lateral medullary syndrome, which is associated with a loss of pain and temperature sensations, loss of the gag reflex, difficulty in swallowing, vertigo, vomiting, or loss of coordination.

Additional Information

Understanding the medulla oblongata is crucial for comprehending how our nervous system functions. This part of the brainstem plays a vital role in regulating essential bodily processes that keep us alive.

Its significance lies not only in its fundamental responsibilities but also in its intricate connections with various neural pathways and organs.

Anatomical Structure

The medulla oblongata, nestled at the base of the brainstem, serves as a bridge between the brain and the spinal cord. Its location is strategic, allowing it to act as a conduit for neural signals traveling to and from the brain. This positioning is not merely incidental; it underscores the medulla’s role in integrating and relaying information essential for bodily functions.

Structurally, the medulla is composed of both white and gray matter. The white matter consists of myelinated nerve fibers that facilitate rapid signal transmission, while the gray matter contains neuronal cell bodies that process and relay information. This dual composition enables the medulla to perform its complex regulatory tasks efficiently. The presence of various nuclei within the gray matter further enhances its ability to manage diverse physiological processes.

One of the most notable features of the medulla is the presence of the pyramids, which are two longitudinal ridges on its anterior surface. These pyramids house the corticospinal tracts, which are crucial for voluntary motor control. The decussation, or crossing over, of these tracts occurs in the lower medulla, explaining why each hemisphere of the brain controls the opposite side of the body. This anatomical arrangement is fundamental for coordinated motor function.

In addition to the pyramids, the medulla contains several other important structures, such as the olive, a prominent bulge on its lateral aspect. The olive is involved in motor learning and coordination, highlighting the medulla’s role in fine-tuning motor activities. The inferior olivary nucleus within the olive sends fibers to the cerebellum, further integrating motor control and sensory information.

Cardiovascular Regulation

The medulla oblongata’s role in cardiovascular regulation is profound, given its responsibility for maintaining stable heart function and blood pressure. At the core of this regulation is the cardiovascular center, a cluster of neurons embedded within the medulla. These neurons continuously process input from baroreceptors and chemoreceptors located in blood vessels, which monitor changes in blood pressure and chemical composition, respectively.

Upon receiving this sensory information, the medulla orchestrates a response through the autonomic nervous system. It can either activate the sympathetic nervous system to increase heart rate and constrict blood vessels, or engage the parasympathetic nervous system to slow down the heart rate and dilate vessels. This dynamic interplay ensures that the body can adapt to various demands, such as physical exertion or rest, maintaining homeostasis.

The medulla’s regulatory function extends to the vasomotor center, which specifically targets blood vessel diameter. By adjusting vascular tone, the medulla helps control systemic vascular resistance, thus influencing blood pressure. The coordination between heart rate and vascular resistance is crucial for effective circulation, ensuring that tissues receive adequate oxygen and nutrients while removing metabolic waste.

Neurotransmitters play a pivotal role in these processes. For example, norepinephrine released from sympathetic nerve endings causes vasoconstriction, while acetylcholine from parasympathetic fibers induces vasodilation. This biochemical precision allows the medulla to fine-tune cardiovascular responses with remarkable accuracy.

Respiratory Control

The medulla oblongata’s influence on respiratory control is both intricate and indispensable. Within its depths lie the dorsal and ventral respiratory groups, clusters of neurons that play a central role in the rhythmic generation of breathing. These neural networks receive input from peripheral chemoreceptors that detect changes in blood oxygen, carbon dioxide levels, and pH, allowing the medulla to adjust breathing patterns in response to the body’s metabolic demands.

The dorsal respiratory group primarily manages the basic rhythm of breathing by sending signals to the diaphragm and intercostal muscles, prompting them to contract and draw air into the lungs. This rhythmic activity is modulated by the ventral respiratory group, which becomes particularly active during periods of heightened respiratory demand, such as exercise or stress. By coordinating these neural signals, the medulla ensures that ventilation matches the body’s needs, maintaining optimal gas exchange.

An additional layer of complexity is introduced through the interaction between the medulla and the pons, another brainstem structure that fine-tunes the breathing process. The pons contains the pneumotaxic and apneustic centers, which influence the medullary respiratory groups to adjust the rate and depth of breaths. This collaboration between the medulla and the pons enables a smooth transition between inhalation and exhalation, preventing erratic breathing patterns.

Reflex Centers

The medulla oblongata’s role in managing reflex actions is a testament to its evolutionary sophistication. Reflexes are automatic responses to stimuli, essential for survival, and the medulla houses several crucial reflex centers that handle these involuntary actions with remarkable precision. These centers are responsible for orchestrating complex reflexive activities, such as coughing, sneezing, swallowing, and vomiting, which protect the body from harm and facilitate essential functions.

Take, for example, the swallowing reflex. When food or liquid contacts the pharynx, sensory receptors send signals to the swallowing center in the medulla. This initiates a highly coordinated sequence of muscle contractions, ensuring that the bolus is safely transported from the mouth to the esophagus, bypassing the respiratory tract. This reflexive action prevents aspiration and safeguards the airway, illustrating the medulla’s critical role in basic yet vital processes.

Equally fascinating is the medulla’s involvement in the vomiting reflex. When noxious substances are detected in the stomach or bloodstream, the chemoreceptor trigger zone (CTZ) in the medulla activates the vomiting center. This leads to a complex series of motor responses, including the contraction of abdominal muscles and the relaxation of the lower esophageal sphincter, resulting in the expulsion of harmful contents. This protective mechanism exemplifies the medulla’s ability to rapidly respond to potential threats, maintaining internal stability.

Cranial Nerve Interaction

The medulla oblongata also plays a significant role in the functionality of cranial nerves, specifically those that emerge directly from this part of the brainstem. These nerves are integral to sensory and motor functions that span various regions of the head and neck, forming a crucial communication network between the brain and peripheral structures.

Among the cranial nerves, the glossopharyngeal (IX) and vagus (X) nerves are particularly noteworthy. They are involved in a myriad of functions, from taste sensation to the regulation of visceral organs. The glossopharyngeal nerve is responsible for transmitting sensory information from the pharynx and the back of the tongue, while also contributing to the control of swallowing. The vagus nerve, often dubbed the “wanderer,” extends its influence far beyond the head and neck, reaching into the thoracic and abdominal cavities. It is essential for autonomic control over heart rate, gastrointestinal peristalsis, and respiratory rate, reflecting the medulla’s extensive reach in maintaining physiological balance.

The hypoglossal nerve (XII) is another key player, emerging from the medulla to innervate the muscles of the tongue. This nerve is vital for articulating speech and facilitating the complex process of mastication. Through these cranial nerve interactions, the medulla oblongata exerts a considerable influence on both voluntary and involuntary activities, demonstrating its vast regulatory capabilities. The integration of these nerves underscores the medulla’s role as a central hub for essential life-sustaining functions.

Q: What do you get if you cross a dog with a daisy?
A: A colli-flower.
* * *
Q: Where do vegetables grow up?
A: Cauli-fornia.
* * *
Q: What did the husband do after forgetting his wife's birthday?
A: Cauliflower shop!
* * *
Q: What water yields the most beautiful cauliflower garden?
A: Perspiration!
* * *

Cerebellum

Gist

The cerebellum, Latin for "little brain," is a crucial part of the brain located at the back, beneath the cerebrum, vital for coordinating movement, balance, posture, and motor learning, essentially fine-tuning commands from the motor cortex to ensure smooth, precise actions by detecting and correcting "motor errors". It receives sensory info and motor plans, compares intended movement with actual execution, and sends corrective signals, influencing everything from walking and talking to complex tasks, with damage leading to coordination loss and slurred speech. 

The cerebellum, Latin for "little brain," is a crucial part of the hindbrain located at the back of the head, primarily responsible for coordinating voluntary movements, balance, posture, and motor learning, ensuring smooth, precise actions by fine-tuning signals from the cerebrum and brainstem; it's also increasingly recognized for roles in cognition, emotion, and social behavior. 

Summary

The cerebellum (pl.: cerebella or cerebellums; Latin for 'little brain') is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as it or even larger. In humans, the cerebellum plays an important role in motor control and cognitive functions such as attention and language as well as emotional control such as regulating fear and pleasure responses, but its movement-related functions are the most solidly established. The human cerebellum does not initiate movement, but contributes to coordination, precision, and accurate timing: it receives input from sensory systems of the spinal cord and from other parts of the brain, and integrates these inputs to fine-tune motor activity. Cerebellar damage produces disorders in fine movement, equilibrium, posture, and motor learning in humans.

Anatomically, the human cerebellum has the appearance of a separate structure attached to the bottom of the brain, tucked underneath the cerebral hemispheres. Its cortical surface is covered with finely spaced parallel grooves, in striking contrast to the broad irregular convolutions of the cerebral cortex. These parallel grooves conceal the fact that the cerebellar cortex is actually a thin, continuous layer of tissue tightly folded in the style of an accordion. Within this thin layer are several types of neurons with a highly regular arrangement, the most important being Purkinje cells and granule cells. This complex neural organization gives rise to a massive signal-processing capability, but almost all of the output from the cerebellar cortex passes through a set of small deep nuclei lying in the white matter interior of the cerebellum.

In addition to its direct role in motor control, the cerebellum is necessary for several types of motor learning, most notably learning to adjust to changes in sensorimotor relationships. Several theoretical models have been developed to explain sensorimotor calibration in terms of synaptic plasticity within the cerebellum. These models derive from those formulated by David Marr and James Albus, based on the observation that each cerebellar Purkinje cell receives two dramatically different types of input: one comprises thousands of weak inputs from the parallel fibers of the granule cells; the other is an extremely strong input from a single climbing fiber. The basic concept of the Marr–Albus theory is that the climbing fiber serves as a "teaching signal", which induces a long-lasting change in the strength of parallel fiber inputs. Observations of long-term depression in parallel fiber inputs have provided some support for theories of this type, but their validity remains controversial.

Details

Your cerebellum is part of your brain that helps coordinate and regulate a wide range of functions and processes in both your brain and body. While it’s very small compared to your brain overall, it holds more than half of the neurons (cells that make up your nervous system) in your whole body.

What is the cerebellum?
Your cerebellum is a part of your brain located at the back of your head, just above and behind where your spinal cord connects to your brain itself. The name “cerebellum” comes from Latin and means “little brain.”

For centuries, scientists believed your cerebellum’s job was to coordinate your muscle movements. Advances in technology have shown that your cerebellum does much more than that. There’s much that scientists are still trying to understand about the cerebellum, including all the ways it works with the rest of your nervous system.

What’s the difference between the cerebellum and cerebrum?

Your cerebellum is a small part of your brain located at the bottom of this organ near the back of your head. Your cerebrum is the largest part of your brain and includes parts above and forward of the cerebellum.

Function:

What does the cerebellum do?

Scientists started analyzing the cerebellum more than 200 years ago by studying people or animals with cerebellum damage. They found people with this kind of damage usually had trouble keeping their balance while standing or walking, or they’d have trouble reaching for objects because their hands would miss an object they were trying to pick up.

Over time, scientists started finding evidence that cerebellum damage could have other effects. They found that damage could make it harder or for a person to learn new words or skills. Damage to your cerebellum can interfere with judging the size of or distance from objects. It can also affect your sense of timing. As an example, people with damage to their cerebellum may have trouble repeatedly tapping their fingers, causing them to tap too soon or too late from beat-to-beat.

Advances in technology have done even more to improve experts’ understanding of the cerebellum. Now, scientists can image a person’s brain activity while that person does a certain task. What scientists have found (so far) is that different parts of your cerebellum are more active depending on what you’re doing at the time. They’ve also found that your cerebellum plays a role in emotions and how you make decisions.

Can you live without a cerebellum?

There are cases of people born with cerebellar agenesis, which is being born without a cerebellum. This condition is extremely rare. Many people with it have only minor effects. They can walk and have lives that are more or less like anyone else’s. Others have severe symptoms and will need constant medical care for their entire life.

People can also survive injuries or diseases that damage their cerebellum, but it’s common for them to have long-term or permanent issues.

What are some interesting facts about the cerebellum?

Neurons are specialized cells that make up your nervous system, including your brain, spinal cord and all of your nerves. Your cerebellum is only about 10% of your brain in terms of how much space it takes up. However, it holds about half of all the neurons in your entire body.

Your cerebellum is also incredibly compact. The brain tissue that makes up your cerebellum is a sheet folded up like an accordion. Laid flat, it would be a little over 3 feet long and 4 inches wide (1 meter by 10 centimeters).

Anatomy:

Where is the cerebellum located?

Your cerebellum is inside of your head, at about the same level as your ears. In relation to the rest of your brain, it’s at the very bottom and sits just above where your neck meets your skull.

What does it look like?

Your cerebellum forms a half-circle shape around your brain stem, which connects your brain to your spinal cord. It has a series of horizontal grooves from top to bottom.

What color is it?

Your cerebellum is a pinkish-gray color.

How big is it?

The average adult cerebellum is about 4.5 inches (11.5 centimeters) wide. In the middle, it’s between 1 inch and 1.5 inches (3 centimeters - 4 centimeters) tall. On the sides, it’s between 2 inches and 2.5 inches (5 centimeters - 6 centimeters) tall.

How much does it weigh?

The average adult cerebellum weighs between 4.8 ounces and 6 ounces (136 grams - 169 grams).

Conditions and Disorders:

What are the common conditions and disorders that affect this body system or organ?

Any condition that can affect your brain can affect your cerebellum. Some major examples include:

* Ataxia (this is both a symptom and a group of diseases).
* Congenital disorders (conditions you have at birth, such as Chiari malformation).
* Immune and inflammatory conditions (an example of this is multiple sclerosis).
* Genetic disorders (conditions you have at birth that you inherited from one or both parents, such as Wilson’s disease).
* Infections (these can happen because of bacteria, viruses, parasites and fungi).
* Vitamin deficiencies and nutrition problems (such as low vitamin B12 levels).
* Stroke.
* Cancer.
* Cerebellar agenesis (being born without a cerebellum at all).

Common signs or symptoms of conditions affecting your cerebellum?

Many symptoms can happen with conditions affecting your cerebellum. Some of the most common symptoms include:

* Dysarthria: Problems with your cerebellum can affect your ability to speak clearly.
* Ataxia: This is a loss of coordination. It can make you clumsy, causing balance problems or trouble using your hands for common tasks.
* Dizziness.
* Paralysis: This can affect various parts of your body.
* Shaking or tremors: Loss of muscle coordination can cause parts of your body, especially your hands, to shake.
* Vision problems: Your cerebellum plays a role in controlling your eyes and how your brain processes what you see. Conditions that affect your cerebellum can cause double vision (diplopia) or other problems.

Common tests to check the health of the body organ?

Many types of tests can help diagnose conditions that affect your cerebellum, including:

* Blood tests (these can look for anything from immune system problems to toxins and poisons, especially certain metals like copper).
* Genetic testing.
* Magnetic resonance imaging (MRI).
* Spinal tap (lumbar puncture).

Common treatments for the body organ?

The treatments for conditions that affect your cerebellum depend entirely on the conditions themselves. They can range from antibiotics for bacterial infections to radiation and chemotherapy for brain tumors. There’s no one-size-fits-all for treating problems that affect your cerebellum.

The cerebellum is located at the base of the brain, under the cerebrum and posterior to the spinal cord. The cerebellum is relatively small, but it is neuron-rich, containing over 50% of the brain’s neurons in a dense cellular layer, called the cerebellar cortex.

Functions of the Cerebellum

The cerebellum plays a vital role in function and mobility. Traditionally known functions of the cerebellum include:

* motor movement regulation, including gait coordination and maintenance of posture
* balance control
* control of muscle tone and voluntary muscle activity
* motor learning

There is also growing research on the cerebellum's role in emotion and cognition, specifically with visual-spatial memory, the creation of generative grammar into the structure of the brain, and the conscious ability to manipulate cause-and-effect relationships.

The cerebellum makes fine adjustments to motor actions. Four principles important to cerebellar processing have been identified.

* Feedforward processing
* Divergence and convergence
* Modularity
* Plasticity

Anatomical Position

The cerebellum is located at the back of the brain, immediately inferior to the occipital and temporal lobes, and within the posterior cranial fossa. It is separated from the occipital and temporal lobes by the tentorium cerebelli, a tough layer of dura mater. It is posterior to the pons. The fourth ventricle separates the pons from the cerebellum.

Cerebellar Structure

The cerebellum has two hemispheres. These hemispheres are connected by the vermis, a narrow midline area. The cerebellum receives input and transmits output via a limited number of cells. It is divided into thousands of independent modules, all with a similar structure.

The cerebellum is made up of grey matter and white matter:

* grey matter: located on the surface of the cerebellum. The grey matter forms the cerebellar cortex. It is tightly folded (i.e. convoluted to increase its surface area) and is divided into three layers: the molecular layer (external); the Purkinje cell layer (middle); and the granular layer (internal). There are two types of neurons in the molecular layer: the outer stellate cell and the inner basket cell.
* white matter: located below the cerebellar cortex. Four cerebellar nuclei (dentate, emboliform, globose, and fastigial nuclei) are embedded in the white matter.

The cerebellum can be subdivided in the following ways: (1) anatomical lobes, (2) zones and (3) functional divisions.

Additional Information

Cerebellum is the section of the brain that coordinates sensory input with muscular responses, located just below and behind the cerebral hemispheres and above the medulla oblongata.

The cerebellum integrates nerve impulses from the labyrinths of the ear and from positional sensors in the muscles; cerebellar signals then determine the extent and timing of contraction of individual muscle fibres to make fine adjustments in maintaining balance and posture and to produce smooth, coordinated movements of large muscle masses in voluntary motions.

Like the cerebrum, the cerebellum is divided into two lateral hemispheres, which are connected by a medial part called the vermis. Each of the hemispheres consists of a central core of white matter and a surface cortex of gray matter and is divided into three lobes. The flocculonodular lobe, the first section of cerebellum to evolve, receives sensory input from the vestibules of the ear; the anterior lobe receives sensory input from the spinal cord; and the posterior lobe, the last to evolve, receives nerve impulses from the cerebrum. All of these nerve impulses are integrated within the cerebellar cortex. Three paired bundles of nerve fibres relay information to and from the cerebellum—the superior, middle, and inferior peduncles—which connect the cerebellum with the midbrain, pons, and medulla, respectively.

Functionally, the cerebellar cortex is divided into three layers: an outer synaptic layer (also called the molecular layer), an intermediate discharge layer (the Purkinje layer), and an inner receptive layer (the granular layer). Sensory input from different types of receptors is conveyed to specific regions of the receptive layer, which is made up of numerous small nerve cells that project axons into the synaptic layer. There the axons excite the dendrites of the Purkinje cells, which in turn project axons to portions of the four intrinsic nuclei (known as the dentate, globose, emboliform, and fastigial nuclei) and upon dorsal portions of the lateral vestibular nucleus. Most Purkinje cells use the neurotransmitter GABA and therefore exert strong inhibitory influences upon the cells that receive their terminals. As a result, all sensory input into the cerebellum results in inhibitory impulses’ being exerted upon the deep cerebellar nuclei and parts of the vestibular nucleus. Cells of all deep cerebellar nuclei, on the other hand, are excitatory (secreting the neurotransmitter glutamate) and project upon parts of the thalamus, red nucleus, vestibular nuclei, and reticular formation.

Injuries or disease affecting the cerebellum usually produce neuromuscular disturbances, in particular ataxia, or disruptions of coordinated limb movements. The loss of integrated muscular control may cause tremors and difficulty in standing.

Q: What do you call a vegetable with a sense of humor?
A: Carrot Top.
* * *
Q: Why did the Ukrainian turn his carrot around?
A: He wanted to start the orange revolution!
* * *
Q: What did the rabbit say to the carrot?
A: It's been nice gnawing you.
* * *
Q: What's a vegetable's favourite casino game?
A: Baccarrot!
* * *
Q: What does the Carrot priest say at church?
A: "Lettuce Pray".
* * *

Blood Plasma

Gist

Blood plasma is the pale yellow, liquid component of blood, making up about 55% of its volume, primarily water (92%) carrying vital proteins (like albumin, globulins, clotting factors), nutrients, hormones, electrolytes, and waste products, serving to transport blood cells, maintain fluid balance, regulate pH, and support immunity and clotting. It's essential for transporting substances throughout the body and is a key source for life-saving medicines. 

Blood is a specialized body fluid. It has four main components: plasma, red blood cells, white blood cells, and platelets. The blood that runs through the veins, arteries, and capillaries is known as whole blood—a mixture of about 55% plasma and 45% blood cells.

Summary

Blood plasma is a light amber-colored liquid component of blood in which blood cells are absent, but which contains proteins and other constituents of whole blood in suspension. It makes up about 55% of the body's total blood volume. It is the intravascular part of extracellular fluid (all body fluid outside cells). It is mostly water (up to 95% by volume), and contains important dissolved proteins (6–8%; e.g., serum albumins, globulins, and fibrinogen), glucose, clotting factors, electrolytes (Na+  Ca2+  Mg2+, HCO3−, Cl− , etc.), hormones, carbon dioxide (plasma being the main medium for excretory product transportation), and oxygen. It plays a vital role in an intravascular osmotic effect that keeps electrolyte concentration balanced and protects the body from infection and other blood-related disorders.

Blood plasma can be separated from whole blood through blood fractionation, by adding an anticoagulant to a tube filled with blood, which is spun in a centrifuge until the blood cells fall to the bottom of the tube. The blood plasma is then poured or drawn off. For point-of-care testing applications, plasma can be extracted from whole blood via filtration or via agglutination to allow for rapid testing of specific biomarkers. Blood plasma has a density of approximately 1,025 kg/{m}^{3} (1.025 g/ml). Blood serum is blood plasma without clotting factors. Plasmapheresis is a medical therapy that involves blood plasma extraction, treatment, and reintegration.

Fresh frozen plasma is on the WHO Model List of Essential Medicines, the most important medications needed in a basic health system. It is of critical importance in the treatment of many types of trauma which result in blood loss, and is therefore kept stocked universally in all medical facilities capable of treating trauma (e.g., trauma centers, hospitals, and ambulances) or that pose a risk of patient blood loss such as surgical suite facilities.

Details

Blood flows like a liquid because of plasma. And that isn’t the only thing that makes it important. Plasma also carries proteins and chemical compounds that keep you alive and your body working properly. You can also donate plasma, and it can be used to help others in a variety of ways.

Plasma is the liquid part of your blood. This fluid makes up a little over half of your blood’s total volume. Other blood cells — like red blood cells, white blood cells and platelets — mix in with the plasma, which carries them to every corner of your body.

Plasma is about 92% water. Proteins (antibodies, coagulation factors, albumin and fibrinogen) make up another 7% of it. The other 1% is hormones, vitamins, water, salt, enzymes and other important compounds.

Function:

What does plasma do?

Plasma has several jobs that make it vital to your survival:

* Carrying red blood cells to your lungs so they can pick up oxygen and release carbon dioxide
* Maintaining blood pressure so blood vessels stay open, making circulation possible
* Delivering water, hormones, nutrients, electrolytes and proteins to parts of your body that need them
* Helping regulate your body temperature
* Carrying immune cells “on patrol” and delivering them to deal with threats like infections
* Carrying proteins that your body uses for inflammation, to clot blood and to repair damage
* Removing waste products to your liver or kidneys so your body can get rid of them

Think of plasma like a river, and everything it carries like boats. Without enough plasma, it’s like a river with a water level that’s too low. It can’t flow or carry those boats — and their vital cargo —where they need to go.

Anatomy:

Where does plasma come from?

Plasma doesn’t really come from a specific place. Instead, it forms when water in your body combines with electrolytes you absorb through your digestive tract. Some of the important proteins that go into plasma come from specific organs or places, though. They include your:

* Bone marrow
* Degenerating, older blood cells
* Liver
* Spleen

Once those proteins combine with the electrolyte-rich liquid, you have plasma.

What does plasma look like?

Plasma is a pale, yellowish or straw-colored liquid when you separate it from red blood cells, white blood cells and platelets.

Your plasma can be different colors if you have a condition that affects what’s in the plasma. For example, if you have red blood cells breaking down (hemolysis), your plasma might look pinkish. If you have high bilirubin levels and jaundice from a liver condition, your plasma may look greenish or brownish.

What percentage of blood is plasma?

In general, your blood is about 55% plasma. That number can vary a little, depending on your sex or medical conditions you have.

How do you separate plasma from the other components of blood?

You can separate blood components, including plasma, using a tool called a centrifuge. This machine spins a tube full of blood very fast. That creates a gravity-like effect that pulls heavier red blood cells to the bottom of the tube. Atop the red blood cells is a whitish layer of platelets and white blood cells. And above that whitish layer is the plasma.

Additional Information

The liquid portion of the blood, the plasma, is a complex solution containing more than 90 percent water. The water of the plasma is freely exchangeable with that of body cells and other extracellular fluids and is available to maintain the normal state of hydration of all tissues. Water, the single largest constituent of the body, is essential to the existence of every living cell.

The major solute of plasma is a heterogeneous group of proteins constituting about 7 percent of the plasma by weight. The principal difference between the plasma and the extracellular fluid of the tissues is the high protein content of the plasma. Plasma protein exerts an osmotic effect by which water tends to move from other extracellular fluid to the plasma. When dietary protein is digested in the gastrointestinal tract, individual amino acids are released from the polypeptide chains and are absorbed. The amino acids are transported through the plasma to all parts of the body, where they are taken up by cells and are assembled in specific ways to form proteins of many types. These plasma proteins are released into the blood from the cells in which they were synthesized. Much of the protein of plasma is produced in the liver.

The major plasma protein is serum albumin, a relatively small molecule, the principal function of which is to retain water in the bloodstream by its osmotic effect. The amount of serum albumin in the blood is a determinant of the total volume of plasma. Depletion of serum albumin permits fluid to leave the circulation and to accumulate and cause swelling of soft tissues (edema). Serum albumin binds certain other substances that are transported in plasma and thus serves as a nonspecific carrier protein. Bilirubin, for example, is bound to serum albumin during its passage through the blood. Serum albumin has physical properties that permit its separation from other plasma proteins, which as a group are called globulins. In fact, the globulins are a heterogeneous array of proteins of widely varying structure and function, only a few of which will be mentioned here. The immunoglobulins, or antibodies, are produced in response to a specific foreign substance, or antigen. For example, administration of polio vaccine, which is made from killed or attenuated (weakened) poliovirus, is followed by the appearance in the plasma of antibodies that react with poliovirus and effectively prevent the onset of disease. Antibodies may be induced by many foreign substances in addition to microorganisms; immunoglobulins are involved in some hypersensitivity and allergic reactions. Other plasma proteins are concerned with the coagulation of the blood.

Many proteins are involved in highly specific ways with the transport function of the blood. Blood lipids are incorporated into protein molecules as lipoproteins, substances important in lipid transport. Iron and copper are transported in plasma by unique metal-binding proteins (transferrin and ceruloplasmin, respectively). Vitamin B12, an essential nutrient, is bound to a specific carrier protein. Although hemoglobin is not normally released into the plasma, a hemoglobin-binding protein (haptoglobin) is available to transport hemoglobin to the reticuloendothelial system should hemolysis (breakdown) of red cells occur. The serum haptoglobin level is raised during inflammation and certain other conditions; it is lowered in hemolytic disease and some types of liver disease.

Lipids are present in plasma in suspension and in solution. The concentration of lipids in plasma varies, particularly in relation to meals, but ordinarily does not exceed 1 gram per 100 ml. The largest fraction consists of phospholipids, complex molecules containing phosphoric acid and a nitrogen base in addition to fatty acids and glycerol. Triglycerides, or simple fats, are molecules composed only of fatty acids and glycerol. Free fatty acids, lower in concentration than triglycerides, are responsible for a much larger transport of fat. Other lipids include cholesterol, a major fraction of the total plasma lipids. These substances exist in plasma combined with proteins of several types as lipoproteins. The largest lipid particles in the blood are known as chylomicrons and consist largely of triglycerides; after absorption from the intestine, they pass through lymphatic channels and enter the bloodstream through the thoracic lymph duct. The other plasma lipids are derived from food or enter the plasma from tissue sites.

Some plasma constituents occur in plasma in low concentration but have a high turnover rate and great physiological importance. Among these is glucose, or blood sugar. Glucose is absorbed from the gastrointestinal tract or may be released into the circulation from the liver. It provides a source of energy for tissue cells and is the only source for some, including the red cells. Glucose is conserved and used and is not excreted. Amino acids also are so rapidly transported that the plasma level remains low, although they are required for all protein synthesis throughout the body. Urea, an end product of protein metabolism, is rapidly excreted by the kidneys. Other nitrogenous waste products—uric acid and creatinine—are similarly removed.

Several inorganic materials are essential constituents of plasma, and each has special functional attributes. The predominant cation (positively charged ion) of the plasma is sodium, an ion that occurs within cells at a much lower concentration. Because of the effect of sodium on osmotic pressure and fluid movements, the amount of sodium in the body is an influential determinant of the total volume of extracellular fluid. The amount of sodium in plasma is controlled by the kidneys under the influence of the hormone aldosterone, which is secreted by the adrenal gland. If dietary sodium exceeds requirements, the excess is excreted by the kidneys. Potassium, the principal intracellular cation, occurs in plasma at a much lower concentration than sodium. The renal excretion of potassium is influenced by aldosterone, which causes retention of sodium and loss of potassium. Calcium in plasma is in part bound to protein and in part ionized. Its concentration is under the control of two hormones: parathyroid hormone, which causes the level to rise, and calcitonin, which causes it to fall. Magnesium, like potassium, is a predominantly intracellular cation and occurs in plasma in low concentration. Variations in the concentrations of these cations may have profound effects on the nervous system, the muscles, and the heart, effects normally prevented by precise regulatory mechanisms. Iron, copper, and zinc are required in trace amounts for synthesis of essential enzymes; much more iron is needed in addition for production of hemoglobin and myoglobin, the oxygen-binding pigment of muscles. These metals occur in plasma in low concentrations. The principal anion (negatively charged ion) of plasma is chloride; sodium chloride is its major salt. Bicarbonate participates in the transport of carbon dioxide and in the regulation of pH. Phosphate also has a buffering effect on the pH of the blood and is vital for chemical reactions of cells and for the metabolism of calcium. Iodide is transported through plasma in trace amounts; it is avidly taken up by the thyroid gland, which incorporates it into thyroid hormone.

The hormones of all the endocrine glands are secreted into the plasma and transported to their target organs, the organs on which they exert their effects. The plasma levels of these agents often reflect the functional activity of the glands that secrete them; in some instances, measurements are possible though concentrations are extremely low. Among the many other constituents of plasma are numerous enzymes. Some of these appear simply to have escaped from tissue cells and have no functional significance in the blood.