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and spinal cord. Both consist of
gray matterthat
contains the cell bodies of
the neurons and glia and white
mattercontaining the
highly myelinated axons. The
CNS is covered by a thick protective tissue known as the
meninges.
The
center of the spinal cord and brain is filled with
cerebrospinal fluid. This cushions the brain and nourishes
the CNS neurons as the circulatory system does not penetrate
the CNS. Fluid and serum components are filtered out of the
blood through the choriod plexus of the brain, circulate
through the spaces in the brain (ventricles) and central
canal of the spinal cord, and drain back into the veins. In
adults, the fluid filled spaces of the brain and spinal cord
are connected. During embryonic development of birds and
mammals, this connection temporarily closes, resulting in a
build-up of fluid in the brain which forces it to
expand.
The
major role of the spinal cord is to relay information to and
from the brain, where most of the processing and decision
making occurs. In addition, the spinal cord can integrate
the response to specific stimuli (reflexes). Sensory
information can be transferred directly to a motor neuron or
(more commonly) passes through at least one interneuron.
Usually, information is also sent simultaneously up to the
brain.
The
development of active predation is associated with the
evolution of the brain. Non-moving filter feeders don't
have to think much; successfully detecting and catching prey
requires the successful integration of a whole set of
data.
The
structure and function of the brain is beyond the scope of
Bio220.
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