Chapter 12 (Part 4)

Question 1

with respect to motor units, what are two different ways to increase the strength of a muscle contraction?

Answer 1

1. stimulate more muscle fibers and larger muscle fibers
2. summation

Question 2

inside the muscle fiber, how does summation and tetanus increase muscle strength?

Answer 2

increase the firing rate.

higher AP frequency = more calcium = stronger contraction.

Question 3

why does higher AP frequency = more calcium = stronger contraction ?

Answer 3

higher AP frequency = calcium doesn’t have enough time to get completely pumped out = total amount of calcium is greater.

more calcium means more troponin, which means more tropomyosin is displaced.

when tropomyosin is displaced, the exposed binding sites can bind to actin, which means more cross-bridge cycling.

Question 4

during smooth muscle contraction, what does Ca+2 activate?

Answer 4

calmodulin, and ca-calmodulin kinase II

Question 5

what is the role of myosin light chain kinase in smooth muscle contraction?

Answer 5

activate myosin light chain

Question 6

what is the role of myosin light chain in smooth muscle contraction?

Answer 6

phosphorylation of MLC activates myosin ATPase, which leads to crossbridge cycling and muscle contraction

Question 7

how is a smooth muscle contraction terminated?

Answer 7

stop stimulating mechanoreceptors
calcium channels close
ca2+ atp-ase pumps ca2+ back into the ER
calmodulin can no longer remain activated
can’t activate more MLCK
stops new myosin light chain phosphorylation
existing myosin light chains must be de-phosph. to stop ATP hydrolysis altogether

Question 8

what is the specific function for creatine phosphate in skeletal muscle? why?

Answer 8

donate phosphate to ATP. you want max ATP rn!

Question 9

why doesn’t smooth muscle use creatine phosphate?

Answer 9

smooth muscle uses the ATP from ox phos

Question 10

why does creatine phosphate supplementation only have a limited positive effect on some types of physical activity?

Answer 10

you’re using max ATP for max. force, such as lifting weights or sprinting. useless for jogging/endurance

Question 11

change in creatinine level in urine or blood can be an indicator of?

Answer 11

problems with the kidneys

Question 12

what causes lactate to begin to build up under anaerobic conditions?

Answer 12

pyruvate has nowhere to go so lactic acid builds up

Question 13

why do you reduce pyruvate to lactic acid?

Answer 13

to make NAD to keep glycolysis going

Question 14

as the bicep muscle insertion point moves farther from the joint how does it affect the force required to curl a weight held in your hand?

Answer 14

easier to lift something that’s farther from the fulcrum

(load F1)(distance from fulcrum F1) = (load F2)( distance from fulcrum F2)