Week 13: (D) Coupling and Skeletal Muscle Contraction

Question 1

What 2 Transporters can take Calcium out of the cytosol?

Answer 1

Na/Ca2+ exchanger

Ca2+ ion pump

Question 2

Where does the majority of Ca2+ in cytosol go and by what pump?

Answer 2

back to the SR

by a serca Ca2+ ATPases pump

Question 3

What inhibits re-uptake of Ca2+?

Answer 3

High conc of Ca2+ in the SR lumen

Question 4

What delays Ca2+ inhibition into SR?

Answer 4

binding to proteins in SR lumen

Question 5

What protein binds to Ca2+ to delay inhibition?

Answer 5

Casequestrin: cardiac and some smooth muscle
Calreticulin: high conc in skeletal muscle

Question 6

What happens when the cell is in full excitation (AP) of T-tubules/SR system?

Answer 6

causes Ca2+release, increase calcium= muscle contraction, Ca2+ in excess

Question 7

What happens after excitation?

Answer 7

SERCA Ca2+ pumps depletes Ca2+ again

Question 8

Does the contractile response lag behind the AP?

Answer 8

YES

because excitation contraction coupling must occur before cross bridge activity begins.

Question 9

What is the delay in contractions called?

Answer 9

latent period

Question 10

What is contraction time?

Answer 10

onset to peak contractile response

Question 11

when does contractile response end?

Answer 11

ends when lateral sacs have taken up all Ca2+ released in response to AP

Question 12

What are lateral sacs?

Answer 12

extended regions of the SR located on either side of the thin T-tubule

Question 13

How quick is re-uptake?

Answer 13

time consuming

Question 14

What is quicker the AP or the contractile response?

Answer 14

AP

Question 15

what is a twitch summation?

Answer 15

Muscle doesn’t have time to fully relax and second twitch is added on to the first

Question 16

What is tetanus?

Answer 16

Muscle fibres stimulated so rapidly it doesn’t have time to fully relax at all between stimuli
–>maximal sustained contraction

Question 17

What fibres have high ATPase activity?

Answer 17

Fast fibres

Question 18

What are the 3 types of fibre?

Answer 18

slow oxidative, fast glycolytic, fast oxidative

Question 19

Where is an example of where slow oxidative would be found?

Answer 19

muscles on the back of the leg, provide support

Question 20

Where is an example of where fast glycolytic would be found?

Answer 20

muscles of the arm, rapid forceful lifting movement

Question 21

How to improve oxidative capacity in skeletal muscle?

Answer 21

regular aerobic endurance exercise promotes metabolic changes within oxidative fibres
increase in mitochondria and no. of capillaries. Fibres do not change in size

Question 22

How to increase muscle hypertrophy?

Answer 22

Anaerobic, short-duration, high intensity resistance training leads to an increased diameter of fast glycolytic fibres (as a result of increased synthesis of actin and myosin).

Question 23

What can increase actin and myosin

Answer 23

Influence of testosterone (promotes synthesis of actin and myosin).

Question 24

Are slow and fast muscle fibres inconvertible?

Answer 24

Slow and fast fibres are not interconvertible.Whether a fibre is fast or slow twitch depends on the fibre’s nerve supply.

Question 25

What type of neurones supply slow twitch fibres?

Answer 25

motor neurons that exhibit a low-frequency pattern of electrical activity.

Question 26

What type of neurones supply fast twitch fibres?

Answer 26

innervated by motor neurons that display intermittent rapid bursts of electrical activity.

Question 27

What can decrease muscle atrophy?

Answer 27

• Disuse atrophy… nerve supply intact-prolonged bed confinement
• Denervation atrophy… occurs after the nerve supply is lost.