Unit 2 - ANS A&P Flashcards
makes up the CNS
- spinal cord
- medulla oblongata
- pons
- midbrain
- thalamus
- cerebral hemisphere
included in cerebral hemisphere
- cerebral cortex
- subcortical white matter
- basal nuclei
peripheral nervous system consists of:
spinal and cranial nerves (except CN2) present outside CNS
ultimate responsibility of ANS
ensure physiologic integrity of cells , tissues ,and organs througout the entire body despite challenges from external environment
ANS division that accounts for miosis and eye accommodation
PNS
3 divisions of the ANS
- Sympathetic
- Parasympathetic
- Enteric divisions
which anatomic part of the nervous system is surrounded and covered by meninges?
central nervous system
which type of muscle does NOT receive ANS signals?
skeletal
ANS division responsible for artery tone
SNS
CV effects of SNS stimulation
- increased cardiac force, rate, conduction, excitability
- constriction and dilation of coronary arterioles
pulmonary effects of PNS
bronchial smooth muscle contraction
pulmonary effects of SNS stimulation
relaxation of bronchial smooth muscle
eye effects of SNS stimulation
- mydriasis (pupil dilation)
- ciliary muscle relaxes (far vision)
peripheral neurotransmitters of autonomic efferents
- ACh
- NE
- Epi
peripheral NT of somatomotor efferents
ACh
target organ(s) of somatomotor efferents
skeletal muscle
nerve fiber classification of preganglionic autonomic efferents
lightly myelinated B fibers
nerve fiber classfication of postganglionic autonomic efferents
nonmyelinated c fibers
nerve fiber classification of somatomotor efferents
heavily myelinated A-alpha fiber
moderately myelinated A-gamma fibers
control system of autonomic efferents
- primarily unconscious, involuntary control
- independent with hormonal control
control system of somatomotor efferents
- primarily conscious, voluntary control
- unrelated to hormonal control
neuron routes involved from spinal cord to target in somatic efferent pathways
1
neuron routes involved from spinal cord to target in ANS efferent pathways
2
schema for anatomic organization of ANS
origin → route to relay → relay → distribution → effector (target)
2 synonyms for efferent
motor, outflow
3 structures that comprise brainstem
- medulla
- pons
- midbrain
(mesencephalon)
2 synonyms for afferent
sensory, inflow
pathway assoc. with short preganglionic and long postganglionic fibers
SNS efferent pathways
SNS origin
preganglionic nerve cell body (soma)
characteristic feature of ANS
its efferents emerge as myelinated fibers from spinal cord or brain (CNS), are interrupted in course by synapse in a peripheral ganglion, and are then relayed for distribution as fine, nonmyelinated fibers to their effectors
nerve fiber classification of preganglionic neurons
lightly myelinated B fibers
nerve fiber classification of postganglionic neurons
unmyelinated C fibers
nerve fiber classification of A-alpha motor neurons
heavily myelinated, large fibers
nerve fiber classification of A-gamma motor neurons neurons
modestly myelinated, thinner fibers
where do sympathetic preganglionic neurons arise
thoracolumbar region
T1-L2
where are cell bodies of preganglionic sympathetic fibers located
lateral hord of spinal cord grey matter, specifically within intermediate (IML) nucleus
where does the IML lie
Rexed’s lamina 7
where do parasympathetic preganglionic neurons travel
CN 3, 7, 9, 10 and sacral roots S2-S4
which division of the ANS is called the craniosacral system
parasympathetic
origin of the somatomotor division
ventral horn of the spinal cord
location of cell bodies of alpha and gamma motor neurons
Rexed’s laminae 8 and 9
where do axons of preganglionic SNS neurons leave the spinal cord
segmental level at which their cell bodies are located
what forms the white rami
preganglionic symapthetic axons exiting from ventral root
why are white rami white
preganglionic fibers are lightly myelinated B fibers and myelin imparts a white color
why are grey rami grey
axons are nonmyelinated - these areas contain nerve cell bodies, which are grey
where do white rami exist and why
only at T1-L3, where all preganglionic SNS fibers originate from
what is a nerve plexus
network of afferent and efferent nerve fibers from different spinal nerves
somatic nerve plexuses
- cervical
- brachial
- lumbar
- sacral
visceral nerve plexuses
- cardiac
- abdominal aortic
- hypogastric
where are spinal levels gray rami found
all spinal cord levels
reflex characterized by increased HR in response to increased right atrial volume
example
Bainbridge
ex- autotransfusion during childbirth
enzyme that deactivates cAMP
phosphodiasterase
preganglionic fibers in SNS vs PNS
PNS
- preganglionic: long, myelinated, B-fiber, releases ACh
- postganglionic: short, unmyelinated, C-fiber, releases ACh
SNS
- pre: short, myelinated, B-fiber, releases ACh
- post: long, unmyelinated, C-fiber, releases NE
origin of efferent SNS pathways
T1-L3
cell bodies arise from IML region of spinal cord (rexed’s lamina 7)
where do efferent SNS fibers exit
ventral nerve roots
where do efferent SNS preganglionic fibers synapse with postganglionic fibers
in paired sympathetic ganglia (mass effect)
origin of efferent PNS pathways
CN 3, 7, 9, 10
S2-S4
where do preganglionic fibers synapse with postganglionic fibers in craniosacral division
near or in each effector organ (precise control of each organ)
innervation of adrenal medulla
no postganglionic innervation
preganglionic axon takes a straight shot to adrenal medulla
sympathetic chain ganglia pairs
- 3 cervical (superior, middle, inferior)
- thoracic 11-12
- lumbar 3-5
- sacral 3-5
- single coccygeal
what is the stellate ganglion
combination of inferior cervical ganglion & T1 ganglion
only splanchnic nerves to carry PNS fibers
pelvic splanchnic nerves
function of splanchnic nerves
deliver preganglionic SNS fibers to prevertebral delay ganglia and plexuses distribute postganglionic fibers
the intermediolateral nucleus lies within which of Rexed’s lamina
7
white rami are found only at spinal cord levels:
T1-L2/L3
which ganglia are sites for sympathetic synaptic relays
sympathetic chain ganglia & prevertebral ganglia
what is a ganglion
a peripheral collection of nerve cell bodies (soma)
3 thoracic splanchnic nerves
- greater
- lesser
- least
which plexus may be blocked for relief of pain due to chronic pancreatitis
celiac plexus
how do somatic sympathetic groups generally travel to effectors
via spinal nerves
where do preganglionic SNS neurons to adrenal medulla arise in spinal cord
IML T4-T12
where do ALL preganglionic sympathetic neurons arise from?
T1-L3
what is the largest sympathetic plexus
celiac
ganglia that are sites for sympathetic synaptic relays
sympathetic chain ganglia
prevertebral ganglia
ganglion of spinal segment T1-2
superior cervical
provides SNS innervation to colon, urinary bladder, reproductive organs
lumbar sphanchnic nerves
what do postganglinoic axons of lesser splanchnic nerves innervate
GI tract, kidneys, bladder, reproductive organs
where do postganglionic fibers from cervical ganglia distribute
structures in head, neck, heart, lungs
what forms the greater splanchnic nerve
a group of visceral SNS preganglinoic nerves from T5-T9/10 that traverse the sympathetic trunk ganglia
function of greater splanchnic nerve
synaptic relays in the celiac and superior mesenteric ganglia
from there, postganglionic fibers are distributed to upper GI via prevertebral plexuses
plexus with distribution to smooth muscle of esophagus
cardiac plexus