Central nervous system

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Human Anatomy
Chapter 16
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Describe the difference between the primary sensory areas of the cerebrum and their
corresponding association areas.

The primary sensory regions of the cerebral cortex receive impulses initiated from
peripheral sensory receptors. For example, the primary auditory area receive impulses from the
cochlea that convey the pitch and loudness of a sound. The auditory association areas allow
multiple neuronal circuits to compare and integrate incoming impulses. Simultaneously,
previously inactive neural circuits are re-activated resulting in coordination of memory,
interpretation and execution of cognitive or motor action plans. In this example, would allow one
to give meaning to words spoken by another.


Briefly describe the three types of cerebral white matter and their functions.

Commissures connect corresponding gray areas of the right and left hemispheres,
association fibers connect neuron to neuron in the same hemisphere, and projection fibers
connect the cerebrum to distal/caudal regions of the brain and spinal cord and vice versa.


Describe the structure and functions of the thalamus.

The thalamus makes up most of the diencelphalon and encloses much of the third
ventricle. The right and left half are connected by the interthalamic adhesion. Overall, the
thalamus processes and relays impulses to and from the cerebral cortex. There are about 12
different major nuclei, and their functions vary. Some are relay nuclei for sensory impulses to the
rest of the brain; these include nuclei that receive and pass on impulses from the retina of the eye
and the cochlea of the inner ear. All sensory imoulses that are relayed to the cerebrum are routed
through the thalamus; thus, the thalamus is a "relay center." It can also be thought of as a sensory
impulse filter, because it may amplify or diminish the "strength"/frequency of the original


Briefly identify the role of the following structures in controlling voluntary skeletal
movement: cerebellum, primary motor cortex, premotor cortex, pyramidal tracts, inferior olivary
nucleus, and cerebral and cerebellar peduncles.

The premotor cortex and primary motor cortex of the frontal lobe of the cerebrum
sequence and coordinate voluntary contraction of skeletal muscles. Pyramidal neurons of the
cortex relay impulses to specific muscle groups. These pyramidal tracts (axons) descend through
the brain stem and continue down the spinal cord. However, in the midbrain, these tracts will
pass through the cerebral peduncles, which will simultaneously relay descending impulses to the
cerebellum. Then the superior cerebellar peduncles will direct impulses in the reverse direction,
back toward the pre-motor cortex of the cerebrum. At the same time the cerebellum also receives
proprioceptive sensory information via the inferior olivary nucleus of the medulla, and it
compares actual body movements to the intended movement generated by the cerebrum. The
cerebellum is responsible for constantly refining the actual movement to achieve the intended


Describe the three meninges of the brain.

The dura mater is the outer membrane and is extremely thick and inelastic. It is
composed of two layers around the brain. The outermost layer, the periosteal layer, is continuous
with the periosteum of the skull bones. The innermost layer of the dura mater is the meningeal
layer. The dura mater has three distinct regions the falx cerebri, the falx cerebelli, and the
tentorium cerebelli. The middlemost meninges is the arachnoid mater. Supporting trabeculae
from the arachnoid layer raise this membrane above the innermost layer—the pia mater. In the
space between these two deeper meninges, the subarachnoid space, circulates cerebrospinal fluid
(CSF). The most delicate membrane is the pia mater, which adheres tightly to the cortical surface
of the brain, covering every sulcus and gyrus. This inner meninges is also the carrier of
microscopic blood vessels.