Muscle Study Questions

Question 1

What is the function of the ryanodine receptors?

Answer 1

to release Ca^{2+} into the cytosol from he SR in skeletal muscle cells

Question 2

What happens in myosin/actin’s location during skeletal muscle contraction?

Answer 2

actin filaments slide past myosin filaments shorting the distance between z disks

Question 3

Tetanic skeletal muscle tension is resulted from the sustained elevation of which molecule’s concentration?

Answer 3

Ca^{2+}

Question 4

What does the pre-stimulation length of the muscle (%Lo) represent in terms of myosin/actin interaction?

Answer 4

Number of myosin cross bridges interacting with the actin

Question 5

What are the differences between Type I (slow, red) fibers and Type II (fast, white) fibers?

Answer 5

Type 1 has more mitochondria, smaller diameter, more myoglobin, harder to get tired (fatigue), and lower glycolytic enzyme activity than type II

Question 6

What is the primary function of gap junctions between smooth muscle cells?

Answer 6

They allow the neighboring smooth muscle cells to communicate electronically

Question 7

What is the physiological result if the level of myosin light chain phosphorylation increases in smooth muscle?

Answer 7

The rate of actin-myosin cross bridge cycle increases. The maximum contraction force increases.

Question 8

Which of the following structures in smooth muscle motor unit releases neurotransmitters as neuromuscular junction does in skeletal muscle?

Answer 8

Varicosity

Question 9

What is the latch state in smooth muscle?

Answer 9

The cross bridge cycle is slowed down due to the myosin light chain dephosphorylation, but not completely stopped

Question 10

What are the similarities between smooth muscle and skeletal muscle contraction?

Answer 10

They both involve voltage dependent calcium channels, ATP consumption, myosin-actin interaction and Ca^{2+} release from SR

Question 11

What factors modulate smooth muscle contraction?

Answer 11

Autonomic nerves, circulating hormones, local signals from other cells, and electrical signals from other smooth muscle cells

Question 12

Why does the force of smooth muscle in blood vessel continually increase after the optimal length?

Answer 12

Passive stress from other tissues continually increase

Question 13

What are the sequence of events in smooth muscle cell contraction?

Answer 13

1) Increase in [Ca^{2+}]
2) Binding of Ca^{2+} to calmodulin
3) Activation of MLCK by Ca^{2+}/calmodulin complex
4) Phosphorylation of myosin light chain
5) Activation of myosin ATPase

Question 14

what factors regulate intracellular calcium of skeletal muscle?

Answer 14

L-type Ca^{2+} channel, calcium pump, ryanodine Receptor, and Na/Ca exchanger

Question 15

What are the differences in Skeletal, Smooth, and Cardiac muscle based on nucleus?

Answer 15

Skeletal muscle is multinucleate, Smooth is mono nucleated, and Cardiac is a mixture

Question 16

What are the differences in skeletal, cardiac, and smooth muscle in terms of automatic phase contraction?

Answer 16

only smooth muscle has automatic phase contraction

Question 17

What are the differences between skeletal, cardiac, and smooth muscle in terms of fatigue?

Answer 17

Only white fiber of skeletal muscle gets fatigue

Question 18

Is skeletal muscle innervated by sympathetic nervous system?

Answer 18

No. Innervated by motor neurons only.

Question 19

Does skeletal muscle always attach to bones?

Answer 19

No. Diaphragm and facial skeletal muscle are exceptions.

Question 20

What type of contraction occurs when myosin head binds to the same F-actin monomer during the cross bridge cycling?

Answer 20

Isometric contraction

Question 21

Why can airway allergies be treated with epinephrine?

Answer 21

Epinephrine activates B2 adrenergic receptor, which in turn activates cAMP signaling pathway, causes airway smooth muscle relaxation

Question 22

Can nerve stimulation induce smooth muscle relaxation?

Answer 22

yes, smooth muscle innervation regulates both contraction and relaxation

Question 23

In a single stimulated isotonic contraction, what changes in the shortness/time relationship curve when load is increasing?

Answer 23

1) latency of contraction increase
2) total shorten duration decrease
3) speed of contraction decrease
4) maximal shorten distance decrease

Question 24

the following measure total body water

Answer 24

D2O, HTO

Question 25

The following measure extracellular volume

Answer 25

1) Inulin
2) Mannitol
3) Radio-labeled Sodium
4) Radio-labeled sulfate

Question 26

The following measure blood volume

Answer 26

1) Radio-labeled iron

2) Cr^51

Question 27

The following measure plasma volume

Answer 27

1) RISA

2) T-1824 (Evan’s Blue)