Autonomic Nervous System Flashcards
what is the autonomic nervous system
the visceral motor division of the peripheral nervous system
*provides motor innervation to smooth muscle, cardiac muscle, and glands
2 divisions of ANS
1) sympathetic
2) parasympathetic
how can the CNS influence the ANS
1) sensory feedback from viscera (stretch, pressure, chemical changes, temperature, irritation)
2) higher cognitive influence (learned behaviors, memory, emotion, mood, fear, stress)
3) brainstem and spinal visceromotor centers
4) HYPOTHALAMUS***
two-neuron circuit: SYMPATHETIC nervous system
1) short pre-ganglionic neuron synapses in a ganglia in the sympathetic chain, with Ach onto a nicotinic receptor
2) long post-ganglionic neuron travels from sympathetic chain to effector organ, delivering norepinephrine onto an adrenergic receptor (alpha or beta)
two-neuron circuit: SYMPATHETIC to sweat glands
1) short pre-ganglionic neuron synapses in a ganglia in the sympathetic chain, with Ach onto a nicotinic receptor
2) long post-ganglionic neuron travels to sweat glands and delivers Ach onto a muscarinic receptor
one-neuron circuit: SYMPATHETIC to adrenal medulla
*pre-ganglionic neuron travels to the adrenal medulla and delivers Ach onto a nicotinic receptor, stimulating release of epi and norepi from the gland
two-neuron circuit: PARASYMPATHETIC nervous system
1) long pre-ganglionic neuron travels to its respective ganglion and delivers Ach onto a nicotinic receptor
2) short post-ganglionic neuron (often in the wall of the effector neuron) releases Ach onto a muscarinic receptor
what is the role of the ANS
maintains homeostasis of the body using antagonistic systems (parasympathetic and sympathetic)
role of the sympathetic nervous system
*fight or flight
*widespread / global
*works in concert with release of hormones from the adrenal gland
general examples of sympathetic responses
*pupil dilation (mydriatic pupil)
*increased cardiac output
*dilated airway
*regulates local blood flow (increased to skeletal muscle, decreased to GI tract)
*decreases release of digestive enzymes
*decreased blood flow to skin
*increased sweating
*stimulation of erector pili in skin
*control of micturition and defecation
*cooperates in human sexual response
role of the parasympathetic nervous system
*rest and digest / breed, read, and feed
*FOCAL response of separate targets that support behaviors
general examples of parasympathetic responses
*pupillary constriction (miotic pupil)
*decreased cardiac output (rate and pressure)
*decreased blood flow to skeletal muscles
*constriction of airway
*increased gut motility for digestion
*glandular secretion (NOT sweat glands)
*micturition and defecation
*cooperates in human sexual response
location of cell bodies of pre-ganglionic sympathetic neurons
lateral horn (intermediolateral cell column in spinal gray matter) of T1-L2
location of cell bodies post-ganglionic sympathetic neurons
1) paravertebral ganglia (sympathetic trunk)
2) superior, middle, and cervical ganglia
3) prevertebral ganglia
paravertebral ganglia
*ganglia regionally named and associated with each spinal nerve
*location of the majority of the cell bodies of post-ganglionic sympathetic neurons
prevertebral ganglia
*ganglia associated with visceral branches of the abdominal aorta
*celiac, superior mesenteric, and inferior mesenteric ganglia
white rami communicantes
*from spinal nerve for preganglionic axons to enter sympathetic trunk
*free to synapse or ascend or descend several segments before synapsing or leaving on splanchnic nerves without synapsing
gray rami communicantes
“on ramp” for post-ganglionic axons rejoining spinal nerve to innervate peripheral targets
splanchnic nerves
branches of sympathetic trunk innervating viscera in body cavities
(cardiac splanchnic nerves are post-ganglionic fibers going to the heart)
(abdominal splanchnic nerves are pre-ganglionic axons going to abdominal viscera)
cervical cardiac nerves
*preganglionic fibers arise from T1-T4 spinal segments and synapse in the cervical and upper thoracic chain ganglia
*postganglionic sympathetics descend from the cervical ganglia to the cardiac plexus and its subsidiaries
*descend to thorax and mingle with other axons in cardiac plexus
*target = heart
carotid plexus of sympathetic fibers to head
*postganglionic fibers are from neurons in superior cervical ganglion
*targets = sphincter of pupil, smooth muscle in upper lip, and sweat glands
location of cell bodies of preganglionic parasympathetic neurons
1) brainstem (CNs III, VII, IX, and X)
2) spinal cord segments S2-S4 (pelvic splanchnic nerves)
parasympathetics of CN III (oculomotor nerve)
*preganglionic PS neuron cell bodies = midbrain
*postganglionic PS neuron cell bodies = ciliary ganglion
*postganglionics follow V1
*target = pupillary sphincter muscle and ciliary muscle of the lens
*function = pupillary constriction & accommodation of lens for ‘near sight’
parasympathetics of CN VII (facial nerve)
1) tearing/lacrimation
-target = lacrimal gland
-preganglionic cell bodies = caudal pons
-postganglionic cell bodies = pterygopalatine ganglion
-follows V2 (short ciliary)
2) salivation
-target = submandibular and sublingual glands
-preganglionic cell bodies = caudal pons
-postganglionic cell bodies = submandibular ganglion
-follows V3
preganglionics of CN IX (glossopharyngeal nerve)
*target = parotid glands
*preganglionic cell bodies = rostral medulla
*postganglionic cell bodies = otic ganglion
*function = salivation
*follows V3
parasympathetics of CN X (vagus nerve)
*targets: cardiac muscle, smooth muscle of respiratory tract, smooth muscle and glands of GI tract from esophagus to transverse colon
*preganglionic cell bodies = medulla (dorsal vagal nucleus)
*postganglionic cell bodies = remote collateral ganglion IN OR NEAR WALL OF ORGAN
sacral parasympathetic outflow
*preganglionic neurons: S2-S4 intermediate gray matter
*postganglionic neurons: intramural ganglia
*responsible for parasympathetics starting at the splenic flexure (descending colon, sigmoid colon, rectum, lower urinary tract, including bladder & pelvic part of ureter, and reproductive organs)
