Muscle Types

Question 1

2 differences between muscle types

Answer 1

1. Excitation-contraction coupling

2. Arrangement of contractile elements

Question 2

3 characteristics of skeletal m.

Answer 2

1. Alpha-motor neuron
2. All mm. cells contract but no cell to cell communication
3. Neurogenic

Question 3

3 characteristics of cardiac m.

Answer 3

1. Contracts on own (no need for innervation)
2. Has cell-cell comm. via intercalated ducts
3. Myogenic

Question 4

4 characteristics of smooth m.

Answer 4

1. No distinct motor endplate (but can be innervated)
2. Cell-cell comm. via gap junction
3. Neurons, hormones, stretch, local factors
4. Myogenic

Question 5

AP of skeletal m.

Answer 5

Lasts 1-2 msec, 8 msec before onset of contraction

Question 6

AP of cardiac m.

Answer 6

Lasts 200-300 msec, 10-15 msec before onset of contraction

Question 7

AP of smooth m.

Answer 7

Lasts 1-2 msec (similar to skeletal), 200 msec before onset of contraction → slow to contract and relax

Question 8

Cardiac m. plateau is associated with?

Answer 8

1. Decreased K permeability

2. Increased Ca permability

Question 9

2 steps of skeletal m. AP

Answer 9

1. Increased permeability to Na (influx)

2. Increased permeability to K (outflow)

Question 10

3 steps of cardiac m. AP

Answer 10

1. Increased permeability to Na (influx)
2. Decreased permeability to K followed by increased permeability
3. Increased permeability of Ca (influx is slower and sustained)

Question 11

Cardiac m. AP: Na

Answer 11

Response speed: fast

Function: initial depol.

Question 12

Cardiac m. AP: K

Answer 12

Response to depol: closes

Response speed: fast

Functions: maintain plateau, repolarization

Question 13

Cardiac m. AP: Ca

Answer 13

Response speed: slow

Function: maintains plateau, prolongs contraction

Question 14

What is unique about cardiac m.?

Answer 14

Ca-induced Ca release

Question 15

How does “Ca-induced Ca release” in cardiac m. work?

Answer 15

Ca influx produces release of Ca from SR via Ca-release channel

Question 16

3 steps of smooth m. EC coupling

Answer 16

1. Ca binds to calmodulinn
2. Calmodulin activates myosin light-chain kinase

HALP don’t understand the last step

Question 17

What’s weird about smooth m.

Answer 17

1. No Z-line to Z-line

2. Shortening can occur to much higher degree than in skeletal m.