Anatomy And Physiology

Anatomy Physiology



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The human brain is composed of four anatomical structures.  These are:  The brainstem and the cerebellum and the diencephalon in addition to the cerebrum.  The brainstem is in turn divided into three structures.  These are: the pons and the medulla in addition to the midbrain.  cranial nerves of the brain originate in different parts of the brainstem and supply different parts of the body with sensory and motor innervation. 


The most important part of the diencephalon is the hypothalamus which is a neuroendocrine structure that is located below the thalamus and above the pituitary gland.  It is connected with this gland through the pituitary stalk.  The hypothalamus has many functions.  One of them is to control the secretion of hormones by the pituitary gland through secreting hormones that regulate the fuction of this gland.   In addition to this important function the hypothalamus has several other functions such as regulating emotional and behavioral expressions.  It does this function along with the limbic system.  The other parts of the diencephalon being the epithalamus and the thalamus. 


The cerebellum is located at the posterior aspect of the brain and is separated from the cerebrum by a membranous structure that is called cerebellar tentorium.  The cerebellum has an important function in the body of coordinating the movement of the muscles.  Disorders of the brain which involve the cerebellum can be manifested by movement disorders such as ataxia and gait disorders.  This function of the cerebellum is shared with other structures in the brain which have similar function to that of the cerebellum. 


This structure of the brain is called the basal ganglia.  It has also important function in controlling muscles movements in the body.  There are several disorders in the body which involve the damage to the basal ganglia.  Examples include Parkinson's disease which is manifested by the deficiency of the hormone dopamine that is secreted by specialized cells in the basal ganglia.  Dopamine is an inhibitory neurotransmitter that its deficiency in the body leads to repetitive movement of muscles in the body especially the arms.


Huntington chorea is another neurological disorder which involves damage to the basal ganglia in the brain.  The cerebrum is the part of the brain that is connected with the brainstem. It contains both sensory as well as motor neurons that receive and give information for the body organs.  The motor cortex for example sends motor information to skeletal muscles in the extremities.  Paralysis in the body in the region of the hands for example can be the result of a damage to the cortex of the cerebrum in its motor area in the opposite direction to the involved hand.  It can also be the result of damage to the upper part of the spinal cord in its motor area.   Paralysis or gait problems in the legs can be the result of a disorder in the motor cortex of the cerebrum in the opposite side to the site of paralysis. It can also be due to damage in the spinal cord in its lumbar region in the motor area.    


The brain has spaces within its structures that are called ventricles. There are in the brain four such ventricles that communicate with each other through canals that are called foramina.  These ventricles are referred to as the lateral ventricles in which there are two of them.  In addition there are other two ventricles that are called the third and fourth ventricles.  Within these ventricles there is a transparent liquid which is called the cerebrospinal fluid.  This liquid functions to support the brain against trauma by absorbing the shock. 


The fluid also provides the cells of the brain with nutrients such as glucose.  The liquid is produced by special type of cells in the lateral ventricles which are called the choroid plexus. These are located in the lateral ventricles but also in other ventricles to a minor degree.  The lateral ventricles are the major site of cerebrospinal fluid production.  This fluid drains into the blood sinuses in the brain using structures in the subarachnoid space that are called arachnoid villi.  Problems in draining this fluid to the blood sinuses can lead to the accumulation of this fluid in the brain.  This leads in turn to elevated pressure of the cerebrospinal fluid in the ventricles.  This condition is called hydrocephalus and is mostly due to the improper drainage of this fluid in the arachnoid villi in the subarachnoid space.

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