Chapter 10

Question 1

Excitation-Contraction coupling?

Answer 1

sequence of events by which propagation of an action potential along the sarcolemma of fiber leads to mechanical events of contraction and development of tension

Question 2

What are the sequence of events in excitation-contraction coupling?

Answer 2

1. somatic (alpha) motor neuron is depolarized above its threshold of excitation, action potential propagated
2. ACh released at the junction
3. ACh crosses cleft, binds nicotinic receptors, depolarizes sarcolemma
4. wave of depolarization begins at junction and propagates in all directions of sarcolemma
5. depolarization enters T-tubule, enters interior of cell
6. Ryanodine receptors activated- release calcium from terminal cisternae into cytoplasm
7. calcium binds to troponin-C exposing active sites of actin

Question 3

4 Steps of the sliding filament theory?

Answer 3

1. activated myosin heads attach to the exposed active sites on actin filament
2. power stroke- ADP + Pi are released causing hinging of myosin neck, pulling actin
3. myosin attached strong to actin, new ATP binds myosin head, myosin detaches actin
4. ATP is broken down, energy stored in hinge of myosin

this cycle continues as long as Ca 2+ is present to bind to troponin-C and reveal the active sites

Question 4

Each myosin head acts ________.

Answer 4

independently

Question 5

How many actin filaments surround myosin?

Answer 5

6

Question 6

Function of sarcoplasmic reticulum calcium ATPase (SERCA pump)?

Answer 6

pumps Ca 2+ back into longitudinal tubules of sarco reticulum

Question 7

Function of Calcium ATPase?

Answer 7

breakdown ATP for energy required by SERCA

Question 8

What happens when levels of Ca 2+ in cytoplasm decrease?

Answer 8

Ca 2+ bound to troponin is released and tropomyosin slides back to it original position, blocking actin active sites

Question 9

Function of Na+/K+ ATPase?

Answer 9

break down ATP to reestablish cell balance of sodium and potassium

Question 10

in vitro?

Answer 10

experimentation outside of the body, like with skeletal muscle fibers

Question 11

in vivo?

Answer 11

experimentation of whole organism, within the living, force of contraction of intact whole muscle

Question 12

isotonic shortening contraction?

Answer 12

FC > FR

myosin heads pull actin over myosin filaments, moving Z lines inward, shortening I bands, H zones and sarcomeres

Question 13

isotonic lengthening?

Answer 13

FC

Question 14

isometric contraction?

Answer 14

FC = FR

length of fiber does not change

Question 15

Lengthening contraction produce _____ force than shortening.

Answer 15

more

Question 16

T/F

Shortening contractions cause microscopic damage to the fiber.

Answer 16

False

lengthening

Question 17

DOMS?

Answer 17

Delayed Onset Muscle Soreness

caused by microscopic damage to whole muscle due to lengthening

Question 18

T-tubules are located at the optimal location, which is ______. This allows for effective _____ __ ____.

Answer 18

A band to I band junction

effective release of Ca 2+

Question 19

Longitudinal tubules are ideally located near the ____ for the optimal ___ __ ____.

Answer 19

A band

reuptake of Ca 2+