ANS/ENS/Smooth Muscle

Question 1

What is the difference between skeletal muscle and smooth muscle?

Answer 1

• Smooth muscle has no striations
• smooth muscle organizes thin and thick filaments differently
• contraction uses different mechanisms

Question 2

How does smooth muscle organize its thin and thick filaments?

Answer 2

• thin: anchored to the plasma membrane by dense bodies

- thick: scattered in the cytoplasm and can bind to multiple thin filaments

Question 3

How does smooth muscle produce a longer contraction than skeletal muscle?

Answer 3

• calcium binds to calmodulin and causes several enzyme reactions that activate myosin/actin

Question 4

What are the two subtypes of smooth muscle?

Answer 4

• Multi-unit: each muscle cell is excited by the release of NT from effector neurons
• visceral: muscle cells are connected by gap junctions so all the connected cells can be excited at once

Question 5

What are pacesetter cells?

Answer 5

Produce regular contractions even when NT is not present

Question 6

What is agonistic innervation?

Answer 6

If one division has a particular effect on an organ, the other system will have the opposite

Question 7

What does the PNS/SNS do to the diaphragm?

Answer 7

• SNS: dialates airways

- PNS: constricts airways

Question 8

What effect does the PNS/SNS have on the intestines?

Answer 8

PNS: increases smooth muscle contractions
SNS: decreases smooth muscle contractions

Question 9

How does the PNS and SNS work together in sexual response?

Answer 9

PNS: arousal
SNS: orgasm

Question 10

What are the disynaptic pathways of the autonomic efferent nerves?

Answer 10

One on the effector cell, and one within the autonomic ganglia of the PNS

Question 11

Where are the preganglionic neurons of the SNS and PNS located?

Answer 11

SNS: gray matter of the thoracic and superior lumbar spinal cord
PNS: brain stem and sacral spinal cord

Question 12

What does the sympathetic chain allow?

Answer 12

All’s the entire division to be activated at once

Question 13

What is the difference in pre/post-ganglionic length of axon between the two divisions?

Answer 13

PNS: long pre, short post, meaning that the ganglia are within or near the target organ
SNS: short pre, long post, meaning that the ganglia are farther away from the target organ and mostly in the chain

Question 14

What NTs do the PNS and SNS release? What does this allow for?

Answer 14

PNS: NE/E
SNS: ACh

They can be activated at the same time because they involve different receptors on the same cell

Question 15

What determines if a NT is excitatory or inhibitory?

Answer 15

The receptor protein

Question 16

What are M1 and M2 receptors?

Answer 16

M1: activation (excitatory metabotropic)
M2: inactivation (inhibitory metabotropic)

Question 17

How does the ANS activate the digestive system?

Answer 17

Synapse mostly onto neurons of the ENS (not effector cells)

Question 18

What is a long visceral reflex?

Answer 18

Sensory neuron synapses on neurons within the CNS, and preganglionic neurons are activated/inactivated (like somatic)

Question 19

What is a short visceral reflex?

Answer 19

Does not involve signals being sent to the CNS

- stimulus—sensory neuron—autonomic ganglion—postganglionic neuron— peripheral effector

Question 20

What is an example of a long and short visceral reflex?

Answer 20

Long: pupils contract in response to light
Short: chyme entering the intestines causes inhibition of further stomach secretion, and stimulates pyloric sphincter