Nervous System Flashcards
neuron
a functional cell of the nervous system
multipolar neurons
cell body is located where input excitation occurs
unipolar neurons
cell body is located along axon in spinal ganglion
nerve
bundle of axons ensheathed by supporting cells and enveloped by connective tissue
root
nerve adjacent to CNS, enveloped by meninges (dorsal and ventral roots in vertebral canal)
ganglion
localized site where a nerve is enlarged due to a collection of cell bodies
spinal ganglia
contain unipolar cell bodies on dorsal root of spinal nerve
autonomic ganglia
contain multipolar cell bodies that innervate viscera
CNS
central nervous system
brain and spinal cord
PNS
peripheral nervous system
12 pairs of cranial nerves attached to brain
36 pairs of spinal nerves attached to spinal cord
what combines to form the spinal nerve?
the dorsal and ventral roots
where is the spinal nerve located?
within the intervertebral foramen dorsal to the intervertebral disc
dorsal root
afferent (sensory) axons and the site of the spinal ganglion
ventral root
efferent axons that innervate muscle and glands
what are the four primary branches of the spinal nerve?
- meningeal branch
- ramus communicans
- ventral branch
- dorsal branch
meningeal branch of spinal nerve
small sensory branch to meninges
ramus communicans (branch of spinal nerve)
connects to sympathetic trunk and innervates viscera
ventral branch of spinal nerve
largest, innervates hypaxial muscle and becomes lateral and ventral cutaneous nerves
dorsal branch of spinal nerve
has medial and lateral branches
innervates epaxial muscles
becomes dorsal cutaneous nerves
afferent fiber types
sensory
associated with receptors and unipolar cell bodies in spinal ganglia
GSA
general somatic afferent
sensory receptors in skin, muscle, tendon, and joints
GVA
general visceral afferent
sensory receptors in viscera
efferent fiber types
motor
innervates muscles and glands
cell bodies located in spinal cord or some autonomic ganglia
SE
somatic efferent (motor) innervates skeletal muscle
VE
visceral efferent
innervates glands, cardiac and smooth muscle
ANS
autonomic nervous system, operates on subconscious level
visceral efferent pathway of 2 multipolar neurons with first cell body in CNS and second in autonomic ganglion (sometimes visceral afferent included as well though has only 1 neuron in pathway)
cutaneous innervation of neck
dorsal cu. n. from dorsal branch of spinal nerve and ventral cu. n. from ventral branch of spinal nerve
cutaneous innervation of thorax
dorsal cu. n. from dorsal branch of spinal nerve
lateral and ventral cu. n. from ventral branch of spinal nerve
cutaneous innervation of limbs
named cutaneous branches of regional nerves from brachial or lumbosacral nerve plexuses
cutaneous innervation of the face
named branches of cranial nerves (from brain)
cutaneous innervation of abdomen
dorsal cu. n. from dorsal branch of spinal nerve
lateral cu. n. from ventral branch of spinal nerve
what creates the nerve plexus of each limb?
there are multiple myotomes per muscle so the ventral branches of different spinal nerves combine to form regional nerves which innervate a single muscle
preganglionic neuron (VE)
cell body in CNS, synapses in autonomic ganglia
releases acetylcholine
postganglionic neuron (VE)
cell body in autonomic ganglia, axon innervates smooth muscle, cardiac muscle, and glands
releases acetylcholine or norepinephrine
sympathetic division of ANS
distributed across whole body
preganglion in thoracolumbar spinal cord
adrenergic (releases norepinephrine/noradrenalin)
“fight or flight” function
parasympathetic division of ANS
distributed in viscera and head
preganglion in sacral spinal cord and brainstem
cholinergic (releases acetylcholine)
routine visceral functions
vagus nerve (parasympathetic pathway)
cranial nerve X
innervates thoracic and abdominal viscera
preganglion branches travel to organs, synapse at terminal ganglia in organs, postganglia travel in submucosal and myenteric plexuses to target
sacral spinal cord (parasympathetic pathway)
innervates pelvic viscera Very Soon, Very Soon, Pee Pee preganglion: Ventral root, Spinal nerve, Ventral branch, Sacral plexus, Pelvic nerve synapse: Pelvic plexus or organ postganglion: branches to pelvic viscera
Common beginning of Sympathetic pathways
V S R S
ventral root, spinal n., ramus communicans, sympathetic trunk
sympathetic pathway of head region
AC / C / C
ansa subclavian, cervical sympathetic trunk, cranial cervical ganglion, plexuses follow carotid artery
sympathetic pathway of neck region
C / VRC
cericothoracic ganglion, vertebral n., rammi communicantes, cervical spinal n.
sympathetic pathway of body wall, limbs, and tail
S / RS
sympathetic trunk ganglion, rammi communicantes, spinal n.
sympathetic pathway of thoracic viscera
2 GANG / CAV 2 ganglia (cervicothoracic and middle cervical), cardiosympathetic trunk from ansa subclavian, branches run along vagus n.
sympathetic pathway of abdominal viscera
S / C CCM / A
splanchnic n., celiac g., cranial and caudal mesenteric g., plexuses on abdominal arteries
sympathetic pathway of pelvic viscera
LS / CM / HPP
lumbar splanchnic n., caudal mesenteric g., hypogastric n., pelvic plexus, pelvic viscera
