Autonomics-Karius Flashcards
Simple reflex arc in skeletal muscle
stimulus–>afferent neuron to spinal cord–>synapse on efferent neuron–>skeletal contraction
What do sympathetic and parasympathetic systems have in common?
Both have 2 synapses, processing occurs in hypothalamus
#1 preganglionic cell body in CNS terminates in peripheral ganglion #2 postganglionic cell body in ganglion terminates on target organ
Parasympathetic
Synapse #1: ACh released in ganglion to activate nAChR #2: short postsynaptic neuron releases ACh on muscarinic AChR
Sympathetic
Synapse #1: ACh released in ganglion to act on nAChR #2: long postsynaptic neuron releases norepinephrine on adrenergic receptor
alpha constricts, beta relaxes
Difference between synapse in skeletal muscle vs autonomic system
Skeletal muscle: NMJ has receptors immediately across from it
Autonomic: postganglionic neurons have varicosities similar to presynaptic NMJ, ligand-gated receptors on target organ are more spread out
M1 receptor
Gq–> increase intracellular Ca++
increase secretion of salivary glands and stomach acid
M2 receptor
Gi decreases cAMP, hyperpolarizes d/t effect on K (more leaving the cell, inside become less excitable and more negative)
slow heart rate at SA node
M3 receptor
Gq–>increase intracellular Ca++
contract smooth muscle, secrete exocrine glands
increase sweat glands are the only exception (sympathetic)
alpha-1 receptor
Gq–>increase intracellular Ca++
decrease K+ efflux
vasoconstriction to increase BP glycogenolysis gluconeogenesis lipolysis reduce glandular secretions contract muscle of iris-->dilate pupil
alpha-2 receptor
Gi–> decrease cAMP
increase K+ efflux, decrease Ca++ influx
contract GI sphincters increase glucagon decrease insulin dilate blood vessels increase clotting
beta-1 receptor
Gs-->increase cAMP increase HR at SA node increase strength of contraction to increase BP at ventricular muscle lipolysis decrease salivary gland secretion
beta-2 receptor
Gs relax smooth muscle of bronchioles relax GI and urinary/repro smooth muscle relax vascular smooth muscle glycogenolysis relax ciliary muscle-->flatten lens to see at distance
ex: Albuterol
beta-3 receptor
Gs
lipolysis in white adipose tissue
heat production in brown adipose tissue
Sympathetic activation responses
Dilate iris of eye
Relax ciliary muscles for far vision
Reduce glandular secretion
Increase HR and contraction strength
Constrict or dilate blood vessels (receptor dependent)
Dilate bronchi
Decrease GI motility and increase sphincter fxn
Increase sweat gland, lipolysis, glycogenolysis and gluconeogenesis
can synapse on adrenal medulla instead of ganglion–> ACh on nAChR–>Epinephrine from chromaffin cells
Parasympathetic activation responses
constrict iris contract ciliary muscles for near vision increase glandular secretion decrease HR constrict bronchi increase GI motility, decrease sphincter function
No action on blood vessels, heart muscle, sweat glands, liver or adipose tissue
