Autonomic Nervous System Flashcards
autonomic nervous system controls
visceral functions (involuntary)
ANS activation occurs mainly from
hypothalamus, brainstem, and spinal cord
ANS divisions
- sympathetic
- parasympathetic
- enteric (GI function regulated independent from the two other divisions)
ANS activity is
a balance between sympathetic and parasympathetic
most target organs have innervation from
both sympathetic and parasympathetic
sympathetic nerves arise from
T1 to L2 segments of the spinal cord (thoracolumbar system)
sympathetic preganglionic neurons are located in
the intermediolateral horn of the spinal cord
sympathetic preganglionic fibers leave
with the ventral nerve roots and go into one of 22 pairs of ganglia in the paravertebral sympathetic chain
some sympathetic preganglionic neurons are __ level, but most travel ___
at the same
cephalad or caudal prior to synapsing
in the sympathetic chain, most preganglionic neurons synapse with
cell bodies of postganglionic fibers
most sympathetic postganglionic fibers exit the chain for
the target organs
sympathetic preganglionic are mostly __, __ fibers
myelinated
fairly slow B
sympathetic postganglionic are mostly __, __ fibers
unmyelinated
C
parasympathetic nerves arise from
cranial nerves III, V, VII, IX, and X and from the sacral spinal cord (craniosacral system)
parasympathetic- cranial III, V, VII, IX supply
the head
parasympathetic- cranial X (vagus)
75% of all parasympathetic NS fibers are supplying the thorax and abdomen
parasympathetic- sacral S2, S3 and sometimes S1, S4 supply
the pelvis
parasympathetic preganglionic fibers pass to
ganglia near or in target organs
parasympathetic postganglionic neurons are
short, due to their proximity to the target organ (contracting with those of sympathetic NS)
all preganglionic neurons release
acetylcholine (ACh)- cholinergic fibers
ACh release at preganglionic fibers activates
both SNS and PNS postganglionic fibers
PNS postganglionic fibers and some SNS fibers secrete
ACh (sweat glands and some blood vessels)
sympathetic NS postganglionic fibers release
norepinephrine
sympathetic NS postganglionic fibers release norepinephrine called
adrenergic fibers
other NTs of the ANS include
dopamine, vasoactive intestinal polypeptide (VIP), ATP, and neuropeptide Y
NTs are stored in
synaptic vesicles in nerve endings
norepinephrine is synthesized from
phenylalanine and tyrosine by series of enzymatic-controlled steps
enzymatic-controlled steps to synthesize norepinephrine
tyrosine-dopa-dopamine-norepinephrine-epinephrine
norepinephrine synthesized from phenylalanine and tyrosine may __ and has a slight __ action than ACh
circulate
longer (circulating 1/2 life of 2 minutes)
termination of action of norepinephrine synthesized from phenylalanine and tyrosine
- reuptake
- metabolism
- dilution
reuptake of norepinephrine synthesized from phenylalanine and tyrosine
80% back into postganglionic sympathetic nerve endings (reusable, can be blocked- cocaine)
metabolism of norepinephrine synthesized from phenylalanine and tyrosine
- monoamine oxidase
- catechol-O-methyltransferase (COMT)