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MSK > Physiology: muscles > Flashcards

Physiology: muscles Flashcards

1
Q

describe the physiological functions of skeletal muscles

A

maintain posture, respiratory movements, heat production, contribute to metabolism, voluntary movement

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2
Q

what are the 3 types of muscle

A

smooth, cardiac and skeletal

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3
Q

what muscle types are striated

A

cardiac and skeletal

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4
Q

what muscle type is unstriated

A

smooth

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5
Q

describe the structure of actin

A

thin filaments that appear as light bands

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6
Q

describe the structure of myosin

A

thick filaments that appear as dark bands

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7
Q

what are skeletal nerves innervated by

A

the somatic nervous system(voluntary)

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8
Q

what are the smooth and cardiac nerves innervated by

A

the autonomic nervous system(involuntary)

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9
Q

describe the initiation of contraction for skeletal and cardiac muscle

A 
skeletal = neurogenic(motor units)
cardiac = myogenic
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10
Q

what junction are involved in skeletal and cardiac muscles

A 
skeletal = neuromuscular junctions
cardiac = gap junctions
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11
Q

describe the excitation contraction coupling of skeletal muscle

A

Ca2+ entirely from sarcoplasmic reticulum

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12
Q

describe the excitation contraction coupling of cardiac muscle

A

Ca2+ from ECF and sarcoplasmic reitculum

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13
Q

what does the gradation of contraction of cardiac muscle depends on

A

extent of filling of the heart with blood(preload)- the Frank Starling mechanism

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14
Q

what is the neurotransmitter involved in neuromuscular junctions

A

Acetylcholine

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15
Q

what are skeletal muscle fibres(cells) organised into

A

motor units

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16
Q

what is a motor unit

A

a single alpha motor neuron and all the skeletal muscle fibres it innervates
allow simultaneous contraction of a number of muscle cells

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17
Q

describe how the number of muscle fibres per motor unit varies depending on function

A

fewer(~10) fibres = finer movements(eg eye)

hundreds to thousands fibres = power over precision(eg thigh)

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18
Q

what is structure contained in a muscle fibre(cell)

A

myofibril(specialised intracellular structure)

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19
Q

what is the functional unit of muscle cells(fibres)

A

sarcomeres

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20
Q

what protein molecules are found in myofibril in muscle cells(fibres)

A

myosin and actin

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21
Q

how long are skeletal muscle cells

A

usually extend the length of the muscle

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22
Q

describe how muscles are usually attached to the skeleton

A

by tendons

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23
Q

how are actin and myosin arranged in myofibril and what is this arrangement called

A

by alternating segments of thin(light) actin bands and dark(thick) myosin bands
called a sarcomere

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24
Q

what is the functional unit of any organ

A

the smallest component capable of carrying out all the functions of that organ

25
Q

what are sarcomeres found between, and what separates them

A

Z-lines, which connect the 2 thin filaments(actin) of adjoining sarcomeres

26
Q

what are the 4 zones of the sarcomere

A

H-zone, A-band, I-band, M-line

27
Q

describe the structure of the A-band of a sarcomere

A

made up of thick filaments along with portions of thin filaments that overlap in both ends of thick filaments

28
Q

describe the structure of the H-zone of a sarcomere

A

lighter area within middle of A-band where thin filaments don’t reach

29
Q

describe the structure of the M-line of a sarcomere

A

extends vertically down middle of A-band within the centre of H-zone

30
Q

describe the structure of I-band of a sarcomere

A

consists of remaining portion of thin filaments that do not project into A-band

31
Q

how is muscle tension produced

A

by actin(thin) molecules sliding on the thick(myosin) filaments

32
Q

what is force generation of a muscle dependant on

A

ATP-dependant interaction between the actin(thin) and myosin(thick) filaments

33
Q

what is ATP required for in muscles

A

contraction and relaxation

34
Q

what is CA2+ required for in muscles

A

to switch on cross bridge formation

35
Q

what is excitation contraction coupling

A

process by which surface action potential results in activation of contractile structures of muscle fibres

36
Q

when is Ca2+ released in skeletal muscle fibres

A

when the surface action potential travels spreads down the transverse (T)-tubules

37
Q

where is Ca2+ released from on skeletal muscles

A

lateral sacs of sarcoplasmic reticulum

38
Q

describe how Ca2+ allows for cross bridge formation

A

Ca2+ binds with troponin, which pulls the troponin-tropomyosin complex to the side exposing the cross bridge binding site

39
Q

what are the 2 primary factors in determining gradation of skeletal muscle tension

A

number of muscle fibres contracting within the muscle

and the tension developed by each contracting muscle fibre

40
Q

what is motor unit recruitment

A

when stronger contraction is achieved by simultaneous contraction of multiple motor units

41
Q

describe the process that helps to prevent muscle fatigue

A

asynchronous motor unit recruitment during submaximal contractions

42
Q

what does the tension developed by each contracting muscle fibre depend on

A

frequency of stimulation, summation of contractions, length of muscle fibres, thickness of muscle fibres

43
Q

describe the relative time of an action potential and a muscle twitch, and what this means

A

action potential much faster than a muscle twitch, therefore multiple action potentials can occur in one twitch

44
Q

describe what tetanus is

A

when a muscle fibre is stimulated so rapidly it doesn’t have time to relax in between contractions, results in a sustained contraction

45
Q

what type of muscle can’t be tetanised

A

cardiac muscle

46
Q

how does frequency of stimulation relate to strength of contraction

A

as frequency increases strength of contraction increase

47
Q

when is maximal tetanic contraction achieved

A

at optimal muscle length; at point of optimal overlap of thick filament and thin filament cross bridge binding sites

48
Q

how is muscle tension transmitted to the bone in skeletal muscle contraction

A

via stretching and tightening of connective tissue and tendons(elastic component)

49
Q

describe what an isotonic skeletal muscle contraction is and what its used for

A

muscle tension remains constant as muscle length changes

used for body movements and moving objects

50
Q

describe what an isometric skeletal muscle contraction is

A

when muscle tension develops at constant muscle length

used in supporting objects in fixed positions and maintaining postures

51
Q

what determines speed of contraction of skeletal muscles

A

activity of myosin ATPase

52
Q

what determines skeletal muscles resistance to fatigue

A

capacity to synthesise ATP

greater capacity = greater resistance to fatigue)

53
Q

how many types of skeletal muscle are usually found in each motor unit

A

one type

54
Q

what different metabolic pathways supply ATP in muscle fibres

A

oxidative phosphorylation, glycolysis, transfer of high energy phosphate from creatine phosphate to ADP

55
Q

what are the different types of skeletal muscle fibres

A

slow oxidative type I(slow twitch)
fast oxidative type IIa(intermediate twitch)
fast oxidative type IIx(fast twitch)

56
Q

describe function of slow twitch(slow oxidative type I) muscle fibres

A

used mainly for prolonged relatively low work aerobic activities

57
Q

describe function of intermediate twitch(fast oxidative type IIa) muscle fibres

A

use both aerobic and anaerobic metabolism and are useful in prolonged relatively moderate work activities

58
Q

describe the function of fast twitch(fast oxidative type IIx) muscle fibres

A

use anaerobic metabolism and are mainly used for short-term high intensity activities

MSK (11 decks)

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