Skeletal + Cardiac Muscle

Question 1

What is the smallest functional unit of skeletal muscles?

Answer 1

Sarcomere

Question 2

What are the general steps in muscle contraction?

Answer 2

1. AP travels along motor nerve on muscle fiber 2. Nerve ending releases ACh 3. ACh activates ACh receptors. Receptor = ACh-gated sodium channel 4. Na+ enters the muscle cell, causing depolarization and action potential of the muscle cell 5. Muscle cell depolarization causes the sarcoplasmic reticulum to release Ca++ into the cytoplasm of the cell 6. Ca++ causes myosin & actin slide towards each other – contraction of muscle 7. Ca++ is pumped back into sarcoplasmic reticulum (contraction stops)

Question 3

What is thick filament composed of?

Answer 3

Myosin

Question 4

What is thin filament composed of?

Answer 4

Actin

Question 5

What are the steps in the sliding filament?

Answer 5

1. Myosin head attaches to actin 2. Myosin head pivots pulling the actin toward the center 3. Cross bridge detaches when ATP binds w/ myosin 4. Goes back to original spot when ATP is hydrolyzed

Question 6

What are the two kinds of muscle fatigue?

Answer 6

Metabolic + Nervous

Question 7

What is something that the heart has but not in the skeletal muscles?

Answer 7

Gap junctions known as Connexon

Question 8

Answer 8

A = Sarcomere

B = Z disc

C = H zone

D = I band

E = A band

F = M line

Question 9

During contraction, what changes in the muscle fibers?

Answer 9

I band get shorter, which shortens the sarcomere

Question 10

What acts as an elastic spring, participates in signaling for muscle enlargement and is the biggest protein in the body?

Answer 10

Titin

Question 11

1. When calcium is released from the SR, where does it bind to?
2. What is pulled aside as a result of that?
3. What is then exposed?
4. What happens next?

Answer 11

1. Troponin
2. Troponin-tropomyosin
3. Myosin-binding sites
4. Binding of cross-bridge occurs

Question 12

What wraps around the thin filament; covers the active site when the muscle is at rest; prevents interaction between myosin & actin?

Answer 12

Tropomyosin

Question 13

When Troponin complex attaches to tropomyosin, there are three kinds of troponin subgroups, what are they?

Answer 13

Troponin I, T, C

Question 14

What does Troponin I have an affinity to?

Answer 14

Actin

Question 15

What does Troponin T have an affinity to?

Answer 15

Tropomyosin

Question 16

What does Troponin C have an affinity to?

Answer 16

Calcium

Question 17

Exactly at the motor end plate, what kind of potential occurs?

Answer 17

Graded potential, if it reaches threshold -> moves Na+ to the side and initiates action potential

Question 18

What are the sources of Ca++ in the skeletal muscle?

Answer 18

SR

Question 19

What are the sources of Ca+ in the cardiac muscle?

Answer 19

Extracellular fluid + SR

Question 20

What are the differences in SR in the skeletal vs cardiac muscles?

Answer 20

Skeletal - developed

Cardiac l - moderatly developed