Chapter 11: The Nervous System Flashcards
how many pairs of spinal nerves do humans have?
31 pairs
cervical nerves
8 (C1-C8)
thoracic nerves
12 (T1-T12)
lumbar nerves
5 (L1-L5)
sacral nerves
5 (S1-S5)
coccygeal nerves
1 (Co)
cauda equina
formed by descending roots of lumbar, sacral, and coccygeal nerves
what type of nerves are spinal nerves?
mixed, except first pair (motor)
how does each spinal nerve split?
into a dorsal & ventral root inside the vertebral column
posterior (dorsal) root
- sensory
- posterior root ganglion
posterior root ganglion
contains cell bodies of sensory neurons whose axons conduct impulses from peripheral body parts into spinal cord
anterior (ventral) root
- motor
- axons of motor neurons whose cell bodies are in the spinal cord
spinal nerve
- union of anterior & posterior roots
- mixed
- 4 branches
4 spinal nerve branches (outside spinal cord)
- meningeal
- posterior branch/ramus
- anterior branch/ramus
- visceral (only thoracic & lumbar)
nerve plexuses
complex network forms by anterior rami (branches) of spinal nerves
where are nerve plexuses NOT located?
T1-T12; instead the anterior rami become intercostal nerves
3 nerve plexuses
- cervical
- brachial
- lumbosacral
cervical plexus
- formed by anterior rami of C1-C4 spinal nerves
- deep in neck
- supply muscles & skin of neck
- C3-C5 contribute to phrenic nerves, which transmit motor impulses to diaphragm
why are C3, C4, & C5 nerves important?
they contribute to phrenic nerves, which transmit motor impulses to diaphragm
brachial plexus
- formed by anterior branches C5-T1
- deep in shoulders
- 5 branches
5 branches of brachial plexus
- musculocutaneous
- ulnar
- median
- radial
- axillary
musculocutaneous
supply muscles of anterior arms & skin of forearms
ulnar & median
supply muscles of forearms & hands, skin of hands
radial
supply posterior muscles of arms & skin of forearms & hands
axillary
supply muscles & skin of anterior, lateral, & posterior arms
lumbosacral plexus
- formed by anterior branches of L1-S4 roots
- lumbar=abdomen, sacral=pelvic
- contain obturator, femoral, & sciatic
obturator
motor impulses to adductors of thighs
femoral
motor impulses to muscles of anterior thigh & sensory impulses from skin of thighs & legs
sciatic
supply muscles & skin of thighs, legs, & feet; largest & longest nerve of the body
ANS
autonomic nervous system
ANS characteristics
- part of PNS
- functions w/o conscious effort
- controls visceral activities
- homeostasis
- regulates smooth & cardiac muscles, glands
- helps respond to stress
- prepares body for exercise
how to sensory nerve fibers transmit signals?
from viscera & skin to neural centers in CNS
how to motor impulses travel?
along 2 efferent nerve fibers which synapse in ganglia outside CNS
how do muscles & glands respond to these signals & impulses?
contracting, secreting, or being inhibited
2 divisions of ANS
parasympathetic & sympathetic
sympathetic
fight or flight
parasympathetic
rest & digest
autonomic nerve fibers
- all of the neurons are motor
- somatic motor paths link the CNS & skeletal muscle fibers via 1 neuron
- autonomic motor paths contain 2 neurons
2 neurons associated with autonomic motor pathways
preganglionic & postganglionic
preganglionic fibers
- axons of preganglionic neurons
- neuron cell bodies in CNS
postganglionic fibers
- axons of postanglionic neurons
- neuron cell bodies in ganglia
- extend to visceral effector
sympathetic division is also called..
thoracolumbar (T1-L2)
where do preganglionic fibers originate? (sympathetic)
in spinal cord, leave via ventral roots, leave spinal nerves through white rami, & enter sympathetic chain (paravertebral) ganglia
what makes up sympahetic trunk?
sympathetic chain ganglia & fibers that conenct
where do sympathetic chain ganglia lie? (sympathetic)
some close to viscera & some further away from viscera
parasympathetic division is also called…
craniosacral
where do preganglionic neurons originate? (para)
brainstem & S2-S4 spinal nerves
where do preganglionic fibers extend from? (para)
cranial or sacral nerves to terminal ganglia (near or in visceral organs)
where are preganglionic fibers in head also included?
- oculomotor
- facial
- glossopharyngeal
where are preganglionic fibers in thorax & abdomen also included?
vagus nerve, which contains 75% of all parasympathetic fibers
what is the job of preganglionic fibers of sacral region?
carry impulses to pelvic viscera