B7.010 Prework: Autonomic Nervous System Basics Flashcards
sympathetic nervous system
thoracolumbar outputs
- preganglionic fibers terminate in ganglia (paravertebral chains)
- postganglionic sympathetic fibers innervate peripheral tissues
adrenal medulla
modified sympathetic ganglion
receives sympathetic preganglionic inputs and releases epi and NE into the blood
parasympathetic nervous system
craniosacral outputs
- preganglionic fibers terminate in parasympathetic ganglia
- postganglionic fibers originate in ganglia and innervate organs
enteric nervous system
walls of GI system
myenteric and submucous plexi
received preganglionic PNS and postganglionic SNS inputs
general function of the ANS
largely autonomous
-not under conscious control
concerned primarily with visceral functions
-CO, blood flow, digestion
afferent sensory inputs drive activity (baroreceptors)
output through reflex arcs of varying size and complexity
SNS components
fight or flight thoracolumbar intermediolateral cell column major ganglia (cervical / mesenteric) adrenal medulla
PNS components
rest and digest craniosacral cranial nerves: III (oculomotor) VII (facial) IX (glossopharyngeal) X (vagus)
ANS innervation of blood vessels
SNS only
ANS innervation of most organ systems
mixed autonomic tone
GI and GU more PNS
PNS nerve structure/ orientation
1:1 preganglionic: postganglionic nerves
more specific
long preganglionic and short postganglionic nerves
ganglia close to targets
SNS nerve structure/ orientation
1:10 preganglionic: postganglionic nerves
more diffuse
short preganglionic and longer postganglionic nerves
ANS receptor types
within ganglia of PNS and SNS, muscarinic receptors
postganglionic SNS mostly adrenergic, some dopamine (renal vascular) and muscarinic (sweat glands)
postganglionic PNS mostly muscarinic
central integration of ANS
midbrain and medulla
integration of information from sensory inputs and higher CNS influence
output by SNS, PNS, and endocrine system are integrated
PNS production of energy conservation
major underlying tone at most end organs (except vasculature)
slowing of the heart and stimulation of digestive activity
SNS recruitment in stress
brief discharges with functional outcomes
cardiac stimulation
increased blood glucose
cutaneous vasoconstriction
function of autonomic reflexes
control cardiovascular homeostasis
main variable is MAP
-if MAP is lowered, compensatory reactions are stimulated by the SNS (increased peripheral resistance, tachycardia)
-if MAP is raises, compensatory reactions are stimulated by the PNS (bradycardia, more limited than SNS)
where are ACh receptors
all preganglionic efferent autonomic fibers
somatic motor fibers to skeletal muscle
most PNS postganglionic and a few SNS postganglionic fibers
NANC neurons
use NO as a neurotransmitter
parasympathetic, postganglionic neurons
where are NE receptors
most postganglionic sympathetic fibers
a few sympathetic fibers release ACh
adrenal medullary cells
analogous to postganglionic sympathetic neurons
release a mixture of epi and NE
PNS effects on the eye
contraction of iris sphincter (miosis)
contraction of ciliary muscle (accommodation)
facilitates aqueous humor outflow
PNS effects on cardiovascular system
reduce peripheral vascular resistance
direct effect is to slow heart rate
releases NO to relax smooth muscle
PNS effects on respiratory system
contracts smooth muscle of bronchial tree
stimulates secretion of glands
exacerbates asthma
PNS effects on GI tract
increases secretions (salivary, gastric, pancreatic, intestinal)
increases peristaltic activity
-contraction of longitudinal muscle
-relaxation of sphincters
PNS effects on GU tract
contracts detrusor muscle
relaxes trigone and sphincter muscles
promotes voiding
PNS effects on secretory glands
stimulation of thermoregulatory sweat glands
production pathway of NE
conversion of tyrosine to DOPA is rate limiting -tyrosine hydroxylase DOPA converted to dopamine -DOPA carboxylase dopamine converted to NE -dopamine beta hydroxylase release is calcium dependent Uptake 1 transports catecholamines back into neuron (recycles)
SNS effect on blood vessels
a receptors increase arterial resistance (pressure)
B2 receptors relax venous smooth muscle (capacitance)
-skin and splanchnic predominantly a, skeletal muscles more B2 (localization produces shift in blood flow from skin/gut to muscle if necessary)
renin secretion stimulated by B receptors > longer term control of MAP
SNS effects on heart
B1 receptor activity dominates
-activation results in increased Ca2+ influx in cardiac cells (positive inotropy and chronotropy)
AV conduction velocity increased
refractory period decreased
SNS effect on resp tract
relaxation of bronchial smooth muscle (B)
contraction of blood vessels (a) of upper resp mucosa can relieve nasal congestion
SNS effect on GI tract
sphincter smooth muscle relaxation (B)
longitudinal cell contraction (a)
decreased PNS drive on enteric system
SNS effect on GU tract
contraction of bladder base, urethral sphincter (a)
relaxation of bladder wall smooth muscle (B)
-promotes urinary retention
SNS effect on exocrine glands
a receptors on apocrine (stress) glands
-driven by SNS activity
-sweating on palms, brow, upper lip
M receptors on thermoregulatory sweat glands
-driven by cholinergic SNS activity
-sweating on body surface for evaporative cooling
SNS effects on the eye
contraction of radial pupillary dilator muscles (a)
-produces mydriasis
increase aqueous humor secretion from ciliary epithelium (B)
metabolic effects of SNS
shifts metabolism toward energy liberation and usage increases lipolysis enhances glycogenolysis increases glucose release increases insulin secretion
dry mouth
reduced SNS/PNS excitatory innervation
swallowing difficulty
reduced PNS mediated motility
airway obstruction
PNS constriction due to loss of SNS dilation
heart rate disturbances
SNS loss = brady
PNS loss = tachy
gastric disturbances
SNS loss = hypermotility
PNS loss - hypomotility
constipation
PNS loss
fecal incontinence
SNS loss
erectile dysfunction
PNS loss
ejaculatory dysfunction
SNS loss
urinary retention
PNS loss
urinary incontinence
SNS loss
pupil constriction
SNS loss
pupil dilation
PNS loss
loss of sweating
loss of SNS cholinergic
orthostatic hypotension
inadequate SNS contraction of vasculature of lower extremities
