Week 13: (D) Coupling and Skeletal Muscle Contraction Flashcards

1
Q

What 2 Transporters can take Calcium out of the cytosol?

A

Na/Ca2+ exchanger

Ca2+ ion pump

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2
Q

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

A

back to the SR

by a serca Ca2+ ATPases pump

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3
Q

What inhibits re-uptake of Ca2+?

A

High conc of Ca2+ in the SR lumen

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4
Q

What delays Ca2+ inhibition into SR?

A

binding to proteins in SR lumen

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5
Q

What protein binds to Ca2+ to delay inhibition?

A

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

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6
Q

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

A

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

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7
Q

What happens after excitation?

A

SERCA Ca2+ pumps depletes Ca2+ again

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8
Q

Does the contractile response lag behind the AP?

A

YES

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

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9
Q

What is the delay in contractions called?

A

latent period

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10
Q

What is contraction time?

A

onset to peak contractile response

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11
Q

when does contractile response end?

A

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

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12
Q

What are lateral sacs?

A

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

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13
Q

How quick is re-uptake?

A

time consuming

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14
Q

What is quicker the AP or the contractile response?

A

AP

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15
Q

what is a twitch summation?

A

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

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16
Q

What is tetanus?

A

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

17
Q

What fibres have high ATPase activity?

A

Fast fibres

18
Q

What are the 3 types of fibre?

A

slow oxidative, fast glycolytic, fast oxidative

19
Q

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

A

muscles on the back of the leg, provide support

20
Q

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

A

muscles of the arm, rapid forceful lifting movement

21
Q

How to improve oxidative capacity in skeletal muscle?

A

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

22
Q

How to increase muscle hypertrophy?

A

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).

23
Q

What can increase actin and myosin

A

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

24
Q

Are slow and fast muscle fibres inconvertible?

A

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

25
Q

What type of neurones supply slow twitch fibres?

A

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

26
Q

What type of neurones supply fast twitch fibres?

A

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

27
Q

What can decrease muscle atrophy?

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