Central nervous system
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
impulse.
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
movement.
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.