Smooth Muscle Physiology

Question 1

What are the two types of smooth muscle and what are their characteristic differences

Answer 1

Multi-unit - 1 N to 1 M. Which allows for finer motor control

Unitary - 1N. To multiple muscles which allows for a group contraction through gap junctions

Question 2

SM does not use what

Answer 2

Troponin

Question 3

Define the characteristics of multi-unit SM

Answer 3

Fibers operate individually and are innervated by a single N.

Question 4

Define the characteristics of unitary smooth muscle

Answer 4

Visceral muscle
Works together as a unit
Contains gap junctions

Question 5

What type of Myosin heads are found in SM

Answer 5

Type II B

Question 6

What binds actin (thin filaments) to the muscle cell walls

Answer 6

Dense bodies/adherens junctions

Question 7

The myosin heads in unitary SM have what type of directionality

Answer 7

Bi-directionality

Question 8

Cycling of myosin cross-bridges is faster or slower than in skeletal muscle

Answer 8

Slower

Question 9

Define the latch mechanism

Answer 9

STP affinity is lower on myosin heads, which allows them to be attached for longer periods of time to the light chains and thus produce a more continuous, low force contraction

Question 10

What allows Ca into the cell cytosol for use in contraction

Answer 10

IP3-Gated Ca release channels and ryanodine for SR

Ca(L) or Ca LGC (hormone activation) from extracellular fluid

Question 11

What does Ca bind to in the cell to begin activation of the steps to contraction

Answer 11

Calmodulin

Question 12

How does Ca exit the cell when it is done with it

Answer 12

SERCA - sarco/endoplasmic reticulum Ca-ATPase (pumps Ca back into SR)

Na/Ca antiporter

Sarcolemmal Ca-ATPase

Question 13

What does CaM activate within the cell and what does this do

Answer 13

MLCK which phosphorylates MLC which allows for Myosin and actin binding

Question 14

The contraction strength is proportional to what

Answer 14

The Ca level

Question 15

What is the regulatory step of SM contraction and why

Answer 15

CaM because it uses ATP

Question 16

What removes the phosphate group from MLC to allow for relaxation

Answer 16

MLCPhosphatase

Question 17

Define varicosities

Answer 17

Neuroxmitter release sites for smooth muscle

Question 18

Define NE/E effects for SM

Answer 18

Excitatory or inhibitory depending on the organ

Question 19

Define Ah effect for SM

Answer 19

Contraction is direct effect

Relaxation is indirect effect

Question 20

Define ANG II effect on SM

Answer 20

Contraction

Question 21

Define adenosine effect on SM

Answer 21

Relaxation

Question 22

Define NO effect on SM

Answer 22

Inhibitory and relaxation

Question 23

What is thew RMP of SM

Answer 23

-50 to -60 mv

Question 24

AP only occurs in what type of smooth muscle though what

Answer 24

Unitary through gap junctions

Question 25

What are the spike potentials in SM AP caused by

Answer 25

Hormones, neuroxmitters, stretch receptors

Question 26

What are the slow waves of SM caused by

Answer 26

Oscillating Ca influx Ca(L) and K efflux

Question 27

What are the plateaus in SM caused by

Answer 27

Neuroxmitters and stretch receptors