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M104 T2 > M104 T2 L11 > Flashcards

M104 T2 L11 Flashcards

1
Q

Why is ATP the direct fuel for contraction?

A

bc it supplies the ATPase activity of myosin

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2
Q

How does ATP support muscle contraction?

A

ATP utilisation increasing more than 100-fold in milliseconds

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3
Q

At rest, per kg of wet weight, how many mols of ATP is there in muscle?

A

approx. 5 mmol of ATP per kg of wet weight

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4
Q

During vigorous contraction, how long does the ATP stored in the muscle last for?

A

less than two seconds

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5
Q

In the short-term, by how much can muscle can increase its rate of production of ATP?

A

20-100 fold

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6
Q

What happens to glycogen stores in resting muscle?

A

glycogen stores are maintained/replenished

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7
Q

How do FAs provide E for resting muscle?

A

via oxidative metabolism of FAs

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8
Q

How is muscle metabolism enacted when exercise starts?

A

Glycogenolysis provides fuel source
there is an increase in o2 consumption for ox phos
there is increased blood flow to muscles due to local mediators (NO) and β-adrenergic stimulation of vascular smooth muscles

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9
Q

What two factors is the amount of E derived from glycolysis and ox phos dependent on?

A

the intensity and duration of the exercise

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10
Q

What is the process by which glycogenolysis is activated to provide the source of fuel in muscle metabolism?

A

glycogen is broken down via glycogen phosphorylase into G-1-P < G-6-P < pyruvate via glycolysis
the pyruvate enters into the mitochondria for the Kreb’s cycle for oxidative phosphorylation and the operation of the ETP to produce ATP

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11
Q

What is the relationship between an increase in ox phos and oxygen consumption?

A

increase in ox phos = an increased requirement in oxygen consumption
bc oxygen is required for the ETC as the final acceptor of e-s
so any increase in ox phos has to be matched by an increase in oxygen consumption

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12
Q

What is increased blood flow to muscles mediated by?

A

local mediators (nitrogen oxide) and β-adrenergic stimulation of vascular smooth muscles

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13
Q

What two enzymes control glycogen metabolism during exercise?

A

glycogen phosphorylase - controls mobilisation of glycogen (glycogen conversion to G-1-P) for use in glycolysis
glycogen synthase - drives the opposite reaction of glycogen synthesis

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14
Q

What is glycogen mobilisation controlled by in the contracting muscle?

A

increasing calcium ion levels in the cytoplasm of the muscle cell, levels of AMP and also by adrenaline

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15
Q

What is glycogen mobilisation controlled by in the contracting muscle?

A

increasing calcium ion levels in the cytoplasm of the muscle cell, levels of AMP and also by adrenaline

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16
Q

What is an increase in calcium ion concentration a signal for?

A

muscle contraction
activates glycogen phosphorylase IOT supply a fuel for ATP synthesis
stimulates the production of nitric oxide

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17
Q

What is the effect of stimulatating the production of nitric oxide on skeletal muscle blood flow?

A

vasodilation of the blood vessels
supplying the skeletal muscle cells
increasing blood flow

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18
Q

What percentage of cardiac output at rest and during extreme physical exertion is accounted for skeletal muscle?

A

20%, can ics to >80% during extreme physical exertion

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19
Q

What are the effects of coordinated, rhythmical contractions during extreme physical exertion?

A

enhances blood flow via the skeletal muscle pump mechanism

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20
Q

What is blood flow affected by?

A

adenosine

K+, CO2, H+ and NO

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21
Q

How are blood vessels vasodilated?

A

via stimulation of the b-2 adrenoreceptors
when they are stimulated by adrenaline
this leads to vasodilation

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22
Q

What is the effect of increasing adrenaline levels?

A

it promotes glycogen and lipid mobilisation

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23
Q

What is the effect of the low insulin:glucagon ratio during exercise?

A

promotes glycogenolysis & gluconeogenesis

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24
Q

What happens to different hormone levels during exercise?

A

increased adrenaline
decreased insulin
increased glucagon

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25
Q

What is the relationship between insulin and glucagon levels during exercise?

A

there is a very low insulin:glucagon ratio

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26
Q

What process does inhibit?

A

gluconeogenesis

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27
Q

Why is there no need for insulin for muscle glucose uptake?

A

bc muscle contraction activates Glut 4 even in the absence of insulin

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28
Q

What are the 3 systems for forming ATP in muscle? (ALO.vera)

A 
ATP-PC (anaerobic)
Lactic acid (anaerobic)
Oxygen system (aerobic)
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29
Q

What are the differences between the aerobic and anaerobic systems of forming ATP in muscle?

A

anaerobic - fast, few ATPs produced, limited amount

aerobic - slow, many ATPs produced, unlimited amount

30
Q

What are the three systems of forming ATP in muscle ranked fastest to slowest?

A

ATP-PC
Lactic acid
Oxygen system

31
Q

What fuel is required for the ATP-PC system of forming ATP in muscle?

A

Phosphocreatine

32
Q

What fuel is required for the Lactic acid system of forming ATP in muscle?

A

Glycogen

33
Q

What fuel is required for the Oxygen system of forming ATP in muscle?

A

Glycogen, fats, proteins

34
Q

In terms of aerobic metabolism, what are the advs and disadvs of carbohydrate oxidation?

A

has a higher power output but a lower capacity than fat oxidation

35
Q

What causes the accumulation of lactate?

A

If the increased rate of metabolism outstrips the oxygen supply, glycolysis can proceed anaerobically. Much less ATP is produced and lactate builds up
when pyruvate is formed faster than it can be oxidised, even if oxygen supply is sufficient

36
Q

What is lactate used by the liver for?

A

to regenerate glucose which can be transferred back to the muscle for E production

37
Q

When will lactic acid build up in muscle?

A

If there is insufficient blood flow through the muscle

38
Q

How does muscle maintain ATP levels?

A

glycogen

FAs from adipose tissue

39
Q

What is aerobic metabolism of glucose and FA oxidation dependent on?

A

an adequate oxygen supply to the muscle

40
Q

What is the relationship between Oxygen and FA oxidation?

A

Oxygen is necessary for any ATP production via fatty acid oxidation

41
Q

When does fatigue occur?

A

when the rate of ATP utilization exceeds its rate of synthesis

42
Q

What will cause a decline in force generated?

A

the accumulation of pyruvate and lactic acid in the contracting muscle will cause a decrease in muscle pH
Glycolysis inhibited by H+ from lactic acid

43
Q

What is the effect of Catecholamines?

A

they stimulate glycogen breakdown in muscle which is converted anaerobically to lactate

44
Q

What is Phosphocreatine converted into?

A

creatine with the transfer of Pi to ADP to form ATP

45
Q

What is the effect of blood vessels being compressed during sprinting?

A

the cells are isolated from the blood supply, making the muscles reliant on anaerobic E production from glycogen

46
Q

What happens to lactic acid levels during sprinting?

A

Large quantities are produced as glycolysis proceeds which the liver can use to maintain blood glucose levels via gluconeogenesis

47
Q

As the distance sprinted increases, the aerobic oxidation of glycogen makes up what % of the ATP required to support contraction?

A

30%

48
Q

From where might some of the oxygen required used to make the ATP required to support contraction come from?

A

oxymyoglobin in the muscle

49
Q

What substance is a major end product of glycogen metabolism?

A

Lactate

50
Q

What percentage of the ATP required comes from lactate during a middle distance run?

A

65%

51
Q

What is the relationship between the contribution of phosphocreatine to the ATP and increased distance sprinted during a middle distance run?

A

the contribution of phosphocreatine to the ATP required DECREASES as the distance INCREASES
At 800 metres it contributes 5%
At over 1500 metres, it contributes essentially zero

52
Q

What is muscle glycogen and glucose from the liver used for during the first 10 mins of a marathon?

A

to power muscles, mainly via glycolysis

53
Q

What is the effect of increased vasodilation in the muscles during the first 10 mins of a marathon?

A

it increases O2 supply increasing the aerobic glycogen utilisation and ATP production

54
Q

What is glycogen breakdown stimulated by during the first 10 mins of a marathon?

A

increased AMP and adrenalin release

55
Q

What are FAs mobilised by during the first 10 mins of a marathon?

A

by the release of adrenalin to allow liver to maintain blood glucose levels by the provision of E and the glycerol backbone

56
Q

By what processes is ATP generated 30 mins - 2hrs into a marathon?

A

oxidation of glucose and FAs

there is an increased reliance on FA oxidation over this longer timespan

57
Q

What substances are used to support glucose production by the liver 30 mins - 2hrs into a marathon?

A

Lactate, glycerol and muscle amacs

58
Q

What is needed to supply most of the needs for resting and for exercising muscle?

A

resting muscle - fats alone

exercising muscle - absolute requirement for some glucose

59
Q

What does FA breakdown during extended periods of exercise proceed on a continual background level of? What does this requirement for a background level of glucose metabolism increas with?

A

glucose metabolism

exercise intensity

60
Q

After two hours of a marathon, what percentage of liver glycogen is used?

A

about 90%

61
Q

After two hours of a marathon, how are insulin and glucagon levels affected?

A

Insulin levels remain very low

glucagon levels elevated

62
Q

After two hours of a marathon, what substance is produced?

A

Ketone bodies produced by the liver

63
Q

After two hours of a marathon, what can ketone bodies be used to generate?

A

may be used by muscle to generate ATP (in addition to FAs)

64
Q

What does the concept of “Hitting the wall” mean?

A

that exercise intensity (pace) drops because of a lack of available ATP

65
Q

What quantity of glycogen does a marathon require?

A

about 700g

66
Q

What quantity of glycogen do the muscles and liver usually contain?

A

only 500g

67
Q

After what distance of a marathon are glycogen stores largely depleted?

A

after 20 miles

68
Q

How is the body’s main source of E altered after glycogen stores run out 20 miles into a marathon?

A

the body switches to FAs as main source of E with little glucose metabolism

69
Q

During the process of Hitting the Wall, what percentage of sufficient ATP is generated by FA oxidation for maximum power output ?

A

50%

70
Q

How can prolonged high-intensity exercise lead to hypoglycaemia?

A

bc liver glucose output may fall below muscle glucose uptake

71
Q

What are the common symtoms of hypoglycaemia?

A

confusion, lack of cognitive function, lactic acidosis and exhaustion may occur (less likely with training)

M104 T2 (15 decks)

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