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Anatomy > muscle twitches > Flashcards

muscle twitches Flashcards

1
Q

muscle mechanics principles

A

same principles apply to contraction of a single muscle fiber and a whole muscle
Contraction produces tension, the force exerted on the load or object to be moved

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2
Q

Isometric contraction

A

no shortening; muscle tension increases but does not exceed the load

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3
Q

Isotonic contraction

A

muscle shortens because muscle tension exceeds the load

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4
Q

Motor unit

A

a motor neuron and all (a least four but up to several hundred) muscle fibers it supplies

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5
Q

smaller vs larger motor units

A

Small motor units in muscles that control fine movements (fingers, eyes)
Large motor units in large weight-bearing muscles (thighs, hips)

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6
Q

muscle twitch

A

Response of a muscle to a single, brief threshold stimulus

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7
Q

myogram

A

a graph of twitch tension development

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8
Q

three phases of a isometric twitch

A

latent period
period of contraction
period of relaxtion

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9
Q

latent period of twitch

A

events of excitation-contraction coupling

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10
Q

period of contraction of twitch

A

cross bridge formation; tension increases

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11
Q

period of relaxtion of twitch

A

Ca2+ reentry into the SR; tension declines to zero

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12
Q

Different strength and duration of twitches are due to

A

variations in metabolic properties and enzymes between muscles

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13
Q

motor unit in a muscle usually contract…

A

asynchronously (some turn off while others turn on) helps prevent fatigue unless load too big

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14
Q

Graded Muscle Responses

A

Variations in the degree of muscle contraction

Required for proper control of skeletal movement

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15
Q

graded muscle responses are graded by

A

Changing the frequency of stimulation

Changing the strength of the stimulus

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16
Q

A single stimulus results in

A

a single contractile response—a muscle twitch

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17
Q

Response to Change in Stimulus Frequency

A

Increase frequency of stimulus (muscle does not have time to completely relax between stimuli)

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18
Q

If another stimulus is applied before the muscle relaxes completely

A

then more tension results. This is temporal (or wave) summation and results in unfused (or incomplete) tetanus. (low stimulation frequency)

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19
Q

If stimuli are given quickly enough

A

fused (complete) tetany results

high stimulation frequency

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20
Q

Threshold stimulus

A

stimulus strength at which the first observable muscle contraction occurs

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21
Q

as stimulus strength is increased above threshold

A

Muscle contracts more vigorously

22
Q

Contraction force is precisely controlled by

A

recruitment (multiple motor unit summation), which brings more and more muscle fibers into action

23
Q

Size principle

A

motor units with larger and larger fibers are recruited as stimulus intensity increases

24
Q

what helps prevent fatigue

A

fibers are contracting asynchronously

25
Q

recruitment principle

A

Can control strength of contraction to meet the needs of the moment

26
Q

muscle tone

A

Constant, slightly contracted state of all muscles

Keeps muscles firm, healthy, and ready to respond

27
Q

muscle tone due to

A

spinal reflexes that activate groups of motor units alternately in response to input from stretch receptors in muscles

28
Q

Isotonic contractions two types

A

concentric contractions or eccentric contractions

29
Q

Concentric contractions

A

the muscle shortens and does work

30
Q

eccentric contractions

A

the muscle contracts as it lengthens

31
Q

isotonic contractions

A

Muscle changes in length and moves the load

32
Q

Isometric Contractions

A

The load is greater than the tension the muscle is able to develop
Tension increases to the muscle’s capacity, but the muscle neither shortens nor lengthens

33
Q

what is the only source used directly for contractile activities

A

ATP

34
Q

For contraction, Available stores of ATP are depleted in

A

4-6 seconds

35
Q

ATP is regenerated by three ways

A 
Direct phosphorylation of ADP by creatine phosphate (CP) (1st 14-16 seconds – turbo boost)
Anaerobic pathway (glycolysis) (30-40 seconds)
Aerobic respiration (95%)
36
Q

Anaerobic Pathway At 70% of maximum contractile activity

A

Bulging muscles compress blood vessels
Oxygen delivery is impaired
Pyruvic acid is converted into lactic acid

37
Q

Anaerobic Pathway lactic acid

A

Diffuses into the bloodstream
Used as fuel by the liver, kidneys, and heart
Converted back into pyruvic acid by the liver

38
Q

Aerobic Pathway

A

Produces 95% of ATP during rest and light to moderate exercise

39
Q

Aerobic Pathway fuels

A

stored glycogen, then bloodborne glucose, pyruvic acid from glycolysis, and free fatty acids

40
Q

short duration exercise 6 seconds

A

ATP stored in muscles is used first

41
Q

short duration exercise 10 seconds

A

ATP is formed from creatine phosphate and ADP

42
Q

short duration exercise 30-40 seconds to end of exercise

A

glycogen stored in muscles is broken down to glucose, which is oxidized to generate ATP

43
Q

prolonged duration exercise hours

A

ATP is generated by breakdown of several nutrient energy fuels by aerobic pathway. this pathway uses oxygen released from myoglobin or delivered in the blood by hemoglobin. when it ends, the oxygen deficit is paid back

44
Q

muscle fatigue

A

Physiological inability to contract

45
Q

muscle fatigue two types

A

nervous fatigue and metabolic fatigue

46
Q

Nervous fatigue

A

Nerve ion imbalance can’t send same intensity of signal anymore

47
Q

Metabolic fatigue

A

Either lack of fuel (ATP – very rare) or some metabolic waste product (lactic acidocis) interferes with calcium function in sarcomere

48
Q

Extra O2 needed after exercise for

A

Replenishment of (Oxygen reserves
Glycogen stores
ATP and CP reserves) and Conversion of lactic acid to pyruvic acid, glucose, and glycogen

49
Q

40% of the energy released in muscle activity is

A

useful for work

50
Q

how much energy in muscle activity is given off as heat

A

60%

51
Q

Dangerous heat levels are prevented by

A

radiation of heat from the skin and sweating

Anatomy (29 decks)

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