Week 6 Flashcards
central nervous system
brain
spinal cord
peripheral nervous system
nerves connecting CNS to the rest of the body
somatic PNS
body
conscious
visceral PNS
guts
not conscious
somatic motor (GSE)
nerves that innervate voluntary muscles (myotomes)
general somatic efferent
somatic sensory (GSA)
nerves that carry conscious sensations from the body wall (dermatomes) back to CNS; specifically pain, temperature, touch, and proprioception
general somatic afferent
visceral motor (GVE)
nerves are part of the autonomic division of the CNS. these nerves are subdivided into two kinds: General Visceral Efferent
sympathetic
parasympathetic
sympathetic
innervates involuntary structures in the body wall (glands, smooth muscle) and viscera
parasmpathetic
innervates visceral structures only
visceral sensory (GVA)
nerves carry unconscious sensations and conscious sensations
general visceral afferent
what are most nerves in the body
multipolar nerurons
multipolar nueron
most common in the brain and spinal cord
3+ dendrites and one long axon
example of multipolar nueron
large motor neurons of the ventral horn of the spinal cord
bipolar neuron
two processes arise form the cell body. One process ends in dendrites, the other (an axon) end in terminals in the CNS. always related to sensory functions
example of bipolar neuron
retinal bipolar cells
cochlear cells
vestibular ganglia
pseudo-unipolar neuron
A single neurite arises from the cell body and divides into two branches. One branch projects to the periphery, the other projects to the CNS; both branches have the structural and functional characteristics of an axon.
example of pseudo-unipolar neuron
sensory cells in the dorsal root ganglia
nerves
collection of axons of neurons
sheathed bundles of axons
neuron
individual cells that relay information
why are neurons packaged together in a nerve
so they can travel together to reach similar destinations
what part of the CNS does most of the communicating with most of the body
spinal cord
gray matter
more cell body
butterfly shape
where do nerves coming from the body go
to the nervous system
white matter
more myelinated axons
meninges
layers of tissues surrounding spinal cord and brain
dura mater (spinal mater)
subdural space
thicket and most durable
arachnoid mater
subarachnoid space
thin layer of spider web like structure
layers of tissue around brain outside to inside
dura mater
arachnoid mater
pia mater
pia mater
very thin translucent layer that directly overlies spinal cord and brain
important thing to know about subdural and subarachnoid space
cerebrospinal fluid lives in subarachnoid space
cerebrospinal fluid
surrounds the spinal cord
helps to protect and to facilitate
spinal nerves
paired nerves come off spinal cord
these nerves head to the rest of the body
1 nerve pair at each vertebra
intervertebral foramen
hole spinal nerves go through
between pedicle
spinal cord segments
31 segments
each segment is a section of cord (grey and white matter) related to a pair of spinal nerves
segmented in function, not appearance
parts of spinal cord to know
conus medullaris
filum terminale
cauda equina
myotomes
segmental blocks of muscles innervated by a spinal segment
dermatomes
stripes of skin innervated by individual spinal segments
important dermatoes
nipple- T4
ubillicus- T10
fingertips- C6-T1
toes- L5-S1
shoulder dermatomes
C3-4
middle finger dermatoes
C7
armpit
T3
dorsal root ganglia
where sensory nerves live
actual cell bodies of the neurons
ventral horn (grey matter)
multipolar somatic motor neurons
visceral motor (GVE) function
to maintain at a constant level the internal environment of the body by regulation of involuntary functions
what do both sympathetic and parasympathetic systems composed of
two neuron arcs
each arc has a preganglionic neuron and a postganglionic neuron
where are parasympathetic neurons located
cranial nerves III, VII, IX, X
S2-S4
where are sympathetic neurons located
T1-L2
sympathetic nervous system
fight or flight
activated in stressful situations, basic function is to increase energy expenditure
examples of sympathetic nervous system
increase in blood flow to skeletal muscle
increase in heart rate, blood pressure, and blood sugar level
pupillary dilation
effects of sympathetic nervous system
widespread because one sympathetic preganglionic axon synapses on many postganglionic neurons
results in a cascade of postganglionic activation
where does the sympathetic nerve pathway start
in intermediolateral column of T1-L2 spinal cord segments
3 basic pathways for sympathetic innervation, depending on what is being supplied
1- visceral body structures in the body wall: arrector pili muscles, sweat/sebaceous glands, peripheral blood vessels
2- thoracic organs (heart, lungs)
3- abdominopelvic organs (stomach)
pathway for sympathetic innervation to body wall
intermediolateal column between T1-L2- preganglionic nerve
down ventral horn
down ventral root
through spinal nerve
down ventral ramus
down white ramus communicans- postganglionic nerve
preganglionic nerve is going to synapse onto postganglionic nerve- activates
postganglionic nerve through grey ramus communicans
up to and through ventral ramus
through series of nerves to body wall
pathway for sympathetic innervation to thoracic organs (only in T1-T4)
IML
down ventral horn
up the ventral root to spinal nerve
down ventral ramus
down white ramus communicans synapse onto postganglionic neuron
nerves leave sympathetic ganglion together
runs straight to wherever its going
pathway for sympathetic innervation to abdominal organs (T5-L2)
IML
down ventral horn
up ventral root to spinal nerve
through ventral ramus
down white ramus communicans into sympathetic ganglion
preganglionic fibers leave sympathetic ganglion together in splanchnic nerve
heads to one of the ganglia that are found on top of the aorta inside abdomen to synapse on postganglionic nerve
then travels from that ganglion to target organ
parasympathetic nervous system function
to conserve and restore body energy
rest and digest
examples of parasympathetic activation
decrease in heart rate
relaxation of sphincter muscles in the gastrointestinal tract
what of the effects of parasympathetic activation
localized and last for a short time because a single parasympathetic preganglionic fiber may only synapse on one or two postganglionic nuerons
what does the parasympathetic function in opposition of
sympathetic system
where are preganglionic neurons located for parasympathetic nervous system
brainstem
sacral spinal cord IML (S2-S4)
where are postganglionic cell bodies located
in 4 dissectible ganglia in the head/neck region, otherwise in the wall of target organ
Visceral pain (GVA)
sensations are not consciously recognized EXCEPT for visceral pain
always uncomfortable or painful, but dull and poorly locailzed
stimuli for visceral pain
ischemia
inflammation
distention or stretching
sustained smooth muscle contraction (cramping)
not stimuli for visceral pain
cutting
crushing
burning
visceral sensation (GVA)
The cell bodies of visceral sensory neurons lie in dorsal root ganglia T1–L2, scattered between the somatic sensory cell bodies
The peripheral processes of their axons, after entering the spinal nerve, distribute to visceral structures by running alongside the sympathetic pre- and post-ganglionic axons for those structures, no matter how complicated that path might be. If you know the path of sympathetic innervation to a structure, you know the path of visceral sensory innervation in reverse, just without synapse
exception for visceral sensation
pathways for distention and most autonomic reflexes follow parasympathetic back to CNS