peripheral nerves
the brain, the spinal cord and the peripheral nervous system work together as a communication system.
spinal cord
continuation of the brain stem
17 inches long and extends from the foremen magnum to the level of the first lumbar vertebrae
gray matter
central- canal- opening or hold that extends the entire length of the spinal cord
white matter
composed primarily of myelinated axons
asending tracts
carry information from the periphery, up the spinal cord and toward the brain
(a sensory tract)
depending tract
carries information from the brain, down the spinal cord, and toward the periphery
(motor tracts)
decussation
the crossing over from one side to the other
the spinal cord serves three main functions
sensory pathway, motor pathway, and reflex center
motor pathway
spinal cord provides a pathway for information coming from the brain and going to the periphery
reflex center
the spinal acts as a major reflex center.
involuntary response to a stimulus
patellar or knee jerk reflex
in response to a tap on you're kneecap , your lower leg quickly and involuntarily pops up
pupillary reflex
regulates the amount of light that enters the eye
baroreceptor reflex
when blood pressure changes, these reflexes cause the heart and blood vessels to respond in a way that restores blood pressure to normal
peripheral nervous system nerves
- sensory nerves- composed only of sensory neurons
- motor nerves- composed only of motor neurons
- mixed neurons- contains both sensory and motor neurons
cranial nerve: Olfactory
a sensory nerve that carries information from the nose to the brain
concerned with the sense of smell
cranial nerve: II optic nerve
sensory nerve that carries visual information from the eye to the brain
cranial nerve: III oculomotor
primarily a motor nerve that causes contraction of the extrinsic eye muscles, thereby moving the eyeball in the socket
cranial nerve: IV trochlear
primarily a motor nerve that innervates one of the extrinsic muscles of the eyeball, helps move the eyeball
cranial nerve: V trigeminal
carry information regarding touch, pressure and pain from the face, scalp, eye and teeth to the brain
cranial nerve: VI abducens
primarily a motor nerve, controls eye movement by innervating only one of the extrinsic eye muscles
cranial nerve: VII facial
the nerve of facial expressions that allows us to smile, frown and make other faces
cranial nevre: vestibulocohlear
carries information for hearing and balance from the inner ear to the brain
cranial nerve: IX glossopharyngeal
carries taste sensations from the posterior tongue to the brain
associated with gag reflex
cranial nerve: X vagus
a mixed nerve that innervates the tongue, pharynx, larynx, and many organs in the thoracic and abdominal cavities
cranial nerve: XI accessory
primarily a motor nerve that supplies the sternocleidomastoid and the trapezius muscles
cranial nerve: XII hypoglossal
primarily a motor nerve that controls movement of the tongue
31 Pais of spinal nerves emerge from the spinal cord and they are:
- 8 pairs of cervical nerves
- 12 pairs of thoracic nerves
- 5 pairs of lumbar nerves
- 5 pairs of sacral nerves
- 1 pair of coccygeal nerves
plexuses
points where nerve fibers converge together
three major nerve plexuses
- cervical plexus
- brachial plexus
- lumbosacral plexus