PHGY 210 Lecture Notes - The Fluid, Living Brain, Dorsal Root Of Spinal Nerve

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31 Jan 2013
The Central Nervous System
o Consists of the parts of the nervous system encased in bone: the brain and the spinal
o Three parts of the brain are common to all mammals: the cerebrum, the cerebellum,
and the brain stem
o The Cerebrum
Rostral-most and largest part of the brain
It is split down the middle into two hemispheres; separated by the deep sagittal
The right hemisphere receives information and controls the left side of the
body; the left hemisphere receives information and controls the right side of the
o The Cerebellum
Lies behind the cerebrum
It contains as many neurons as both cerebral hemispheres combined
It is primarily a movement control center with extensive connections to the
cerebrum and spinal cord
Left side of the cerebrum is concerned with the left side of the body and the
same applies to the right portion.
o The Brain Stem
The remaining part of the brain
Forms the stalk from which the cerebral hemispheres and the cerebellum sprout
A complex nexus of fibers and cells that in part serves to relay information from
the cerebrum to the spinal cord and cerebellum; and vice versa
Also the site where vital functions are regulated (e.g. breathing, consciousness,
and the control of body temp.)
Considered the most primitive part of the mammalian brain but also the most
important to life
o The Spinal Cord
Encased in a bony vertebral column and is attached to the brain stem
Is the major conduit of info from skin, joints, and muscles of the body to the
brain and vice versa
It communicates with the body via the spinal nerves (part of PNS).
Each spinal nerve attaches to the spinal cord by means of two branches:
the dorsal root and the ventral root
The Peripheral Nervous System
o Has two parts: the somatic PNS and the visceral PNS
o The Somatic PNS
All the spinal nerves that innervate the skin, the joints, and the muscles that are
under voluntary control are part of this PNS
The somatic motor axons (command muscle contraction) derives from motor
neurons in the ventral spinal cord
The cell bodies of the motor neurons lie within the CNS, but their axons are
mostly in the PNS
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