Lecture 15 Somatic Motor & ANS

Question 1

Somatic motor effectors

Answer 1

skeletal muscles

efferent division of the PNS

Question 2

Autonomic effectors

Answer 2

cardiac muscle, smooth muscle, glands, adipose tissue

Question 3

Somatic motor division

Answer 3

somatic motor neurons activate skeletal muscles

voluntary (mostly): control of movement posture, breathing

Question 4

Somatic Motor Pathway

Answer 4

one motor neuron pathway from CNS to muscle(effector)
motor neuron cell bodies located in the ventral gray horn of spinal cord
axons travel through spinal nerves
axon terminals located at the neuromuscular junction

Question 5

3 components of the neuromuscular junction

Answer 5

axon terminal of motor neuron
synaptic cleft
motor end plate

Question 6

neuromuscular junction

Answer 6

ACh into the synaptic cleft
nicotinic cholinergic receptors at the motor end plate
binding of ACh open cations channels -> strong EPSP->
exceeds threshold -> muscle AP

Question 7

Autonomic Division (ANS)

Answer 7

involuntary control of autonomic effectors (visceral organs, blood vessels, etc.)
activated by the hypothalamus, pons&medulla, and spinal cord (autonomic reflexes)
two motor neuron pathway from CNS to effectors: preganglionic and postgagnlionic

Question 8

Autonomic division ganglionic fibers

Answer 8

preganglionic fibers from CNS to autonomic ganglia

postganglionic fibers from autonomic ganglion to target organ

Question 9

2 Divisions of the ANS

Answer 9

sympathetic - fight or flight

parasympathetic- rest and digest

Question 10

Dual innervation of sympathetic and parasympathetic

Answer 10

to target organs, usually antagonistic (opposite)
both systems are active, but parasympathetic dominates during normal maintenance states; sympathetic system dominates during short term stress, exercise, cold, drop in BP

Question 11

ANS organization

Sympathetic Division

Answer 11

thoracolumbar outflow
short preganglionic, long postganglionic fibers
ganglia located in sympathetic chain and collateral ganglia
adrenal medulla is functionally part of the sympathetic division

Question 12

In the sympathetic division what do postganglionic neurons secrete

Answer 12

norepinephrine (NE) as the neurotransmitter at target cells

Question 13

Adrenal medulla’s role in the sympathetic division

Answer 13

stimulated directly by preganglionic sympathetic fibers
secretes the hormones epinephrine (E) and norepinephrine (NE)
only stimulated by sympathetic response

Question 14

where do the preganglionic fibers in the sympathetic division arise from?

Answer 14

the thoracic and lumbar spinal cord

Question 15

Where do the short preganglionic fibers go to in the sympathetic

Answer 15

go to sympathetic ganglia close to the spinal cord

Question 16

Parasympathetic division

Answer 16

carinosacral outflow (preganglionic arise from cranial and sacral regions)
long preganglionic, short postganglionic fibers
post ganglionic neurons secrete acetylcholine (ACh) as the neurotransmitter at target cells
terminal ganglia located in or near target organs

Question 17

Vagus nerbe (cranial nerve X)

Answer 17

is the major parasympathetic nerve to visceral organs

Question 18

ANS neurotransmitter and receptors

preganglionic fibers

Answer 18

ACh-> nicotinic cholinergic receptors

sympathetic and parasympathetic

Question 19

Postganglionic fibers

sympathetic

Answer 19

E, NE -> adregergic receptors
most target cells use NE as the neurotransmitter
E is the hormone released form the adrenal medulla
alpha-adrenergic receptors
beta-adrenergic receptors

Question 20

alpha-adrenergic receptors

Sympathetic

Answer 20

a1 -> constriction of blood vessels

G-protein couples receptors, activate phospholipase C second messenger pathway

Question 21

beta-adrenergic receptors

sympathetic

Answer 21

B1-> stimulates heart
B2-> bronchodilation
G protein couple receptors, activate cAMP second messenger pathway

Question 22

postganglionic fibers

parasympathetic

Answer 22

ACh-> muscarinic cholinergic receptors

G-protein coupled receptors, open or close K+ channels (excitatory or inhibitory)

Question 23

Sympathetic causes

Answer 23

increase heart rate and contractability (B1)
inhibits digestive tract motility and secretion (a, B2)
vasoconstriction in peripheral blood vessels (a, some B2)
vasodilation in skeletal muscles
bronchiole dilation (B2)
pupil dilation (a)
mobilization of energy reserves (glycogen and lipids)

Question 24

Parasympathetic causes

Answer 24

decrease in heart rate (no effect on contractility) (B1)
stimulates digestive tract motility and secretion (a,B2)
no effect on blood vessels
bronchiole constriction (B2)
pupil constriction (a)
no metabolic effects