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muscle contraction and function Flashcards

1
Q

3 types of muscle tissue in the body

A

skeletal, smooth and cardiac muscle

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2
Q

each muscle is an organ composed of what ?

A

skeletal muscle tissue, blood and other connective tissues

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3
Q

what is fascia and its role

A

layers of dense connective tissue which surround and separate each muscle

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4
Q

fascia extends and give rise to ?

A

tendons which are fused to the periosteum of bones

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5
Q

what is aponeuroses

A

when muscles are connected to each other by broad sheets of connective tissues

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6
Q

what is the layer of connective tissue around each skeletal muscle

A

facia blending with epimysium

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7
Q

does perimysium extend inward

A

yes it extends inwards from the epimysium

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8
Q

what does perimysium do

A

surrounds bundles of skeletal muscle fibres called fascicles within each muscle

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9
Q

what is endomysium

A

each muscle cell fibre covered by a connective tissue layer

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10
Q

Describing muscle fibre

A

is a single, long, cylindrical muscle cell which responds to stimulation by contracting

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11
Q

the name of the cell membrane of a muscle fibre is ?

A

sarcolemma

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12
Q

the cytoplasm of a muscle cell is? and what does it contain?

A

sarcoplasm and it contains many mitochondria and nuclei

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13
Q

sarcoplasm contains what apart from mitochondria and nuclei?

A

parallel myofibrils, which are active in muscle contraction

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14
Q

what protein thick filaments in myofibrils contain

A

protein myosin

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14
Q

what protein is contained in think filaments in myofibrils

A

protein actin, troponin and tropomyosin

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15
Q

what is the name given to organisation of the filaments producing bands

A

striations

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16
Q

why darker image appears in skeletal muscles striations

A

it appears darker because actin and myosin overlap A band
I band is lighter

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17
Q

what are myofibrils made up of?

A

small units Called sarcomere that are joined end to end

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18
Q

sarcomere extends from where?

A

Z line to the next

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19
Q

what are I bands made up of

A

I bands are light
made up of actin filaments which are anchored to the Z lines

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20
Q

what are A bands are made up of

A

A bands appear dark, and there is a overlapping of thick and thin filaments

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21
Q

what zone is in the centre of A band

A

the centre of A band is H zone and it consists of myosin filaments only

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22
Q

where is the M line

A

M line is in the centre of the H zone

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23
Q

M line consists of what?

A

M line consists of proteins that hold the myosin filaments in place

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24
Q

where is sarcoplasmic reticulum

A

beneath the sarcolemma of a muscle fibre lies a network of membraneous channels

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25
Q

SR Is a what of muscle

A

endoplasmic reticulum

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26
Q

describe T tubules

A

lies between 2 cisternae of the SR and are open to the outside of the muscle fibre

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27
Q

how SR and T tubules work together

A
  • by activating muscle contraction when fibre is stimulated
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28
Q

when skeletal muscle fibres contract

A

only when stimulated by a motor neuron

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29
Q

how synapses are created

A

each skeletal muscle fibre cell is functionally connected to the axon of a motor neuron

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30
Q

how neurons and muscle fibres communicate

A

by neurotransmitters which are released at synapse

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31
Q

how neurons communicate with the muscle fibre

A

neurotransmitters which released at synapses

32
Q

what do you call a synapse between motor neuron and a muscle fibre which regulates.

A

neuromuscular junction

33
Q

The cytoplasm of the distal end of the motor neuron contains what?

A

it contains numerous mitochondria and synaptic vesicles storing neurotransmitters

34
Q

motor end plate

A

it is specialised area in the muscle fibre membrane

35
Q

where sarcolemma tightly folded ?

A

in the motor end plate

36
Q

what motor end plate contains

A

it contains specific receptors for the neurotransmitter

37
Q

what happens when an electrical impulse reaches the end of the motor neuron axon?

A

synaptic vesicles release neurotransmitter into the synaptic cleft

38
Q

what is synaptic cleft

A

the gap between the membranes of the neuron and muscle fibre

39
Q

how muscle fibre contract

A

the neurotransmitter diffuses across the cleft and bind to the motor end plate and cause stimulation and muscle fibre contract

40
Q

what are the events involved in muscle contraction?

A

shortening of sarcomeres and pulling of the muscle against it attachments

41
Q

where is the pulling force exerted from?

A

by binding of myosin and actin molecules

42
Q

shortening of a muscle fibre results from where?

A

from actin and myosin filaments overlapping as they slide pass each other

43
Q

shortening of muscle fibres results in what?

A

it results in shortening of the entire muscle, which pulls on the skeleton to cause movement

44
Q

describe myosin

A

consist of two twisted strands, with globular heads projected outward along the strands

45
Q

how a thick filament is formed

A

by a group of myosin molecules

46
Q

what is actin

A

a globular protein arranged in twisted filaments ( a double helix) , containing myosin binding sites

47
Q

what are 2 proteins that are associated with the surface of actin molecules?

A

troponin and tropomyosin and all 3 proteins will form the thin filaments

48
Q

how cross-bridge is made according to the sliding filament model of muscle contraction?

A

during a muscle contraction, myosin head attaches to a binding site on the actin filament which forms a cross-bridge

49
Q

what does the binding between myosin to actin cause

A

it causes the head to bend, pulling an actin filament and moving it toward the centre of the sarcomere

50
Q

what happens when filaments increase their overlap?

A

the sarcomere shortens from both ends

51
Q

what happens when many sarcomeres shorten

A

at the same time muscle fibre shortens

52
Q

what happens when ATP is broken down

A

it causes the heads to return to the cocked position ready to bind to another actin binding site

53
Q

what is acetylcholine

A

is a neurotransmitter for skeletal muscle fibre contraction at the neuromuscular junction

54
Q

where is acetylcholine produced and stored

A

it is produced in motor neuron and stored in synaptic vesicles at the distal end of the neuron

55
Q

what does acetylcholine stimulate

A

muscle fibre

56
Q

where is acetylcholine released into

A

acetylcholine is released into synaptic cleft in the response to an impulse in the motor neuron

57
Q

what happens after muscle fibre impulse

A

the sarcoplasmic reticulum releases its stored calcium to the cytosol of the muscle fibre

58
Q

where the stored calcium released into

A

released into cytosol of the muscle fibre

59
Q

the high levels of calcium in the sarcoplasmic reticulum interacts with what?

A

with the troponin and tropomyosin molecules which move aside exposing the myosin binding sites on the actin filaments

60
Q

explain the events after nerve impulse stops and lead to relaxation of the muscle

A

first the enzyme acetylcholinesterase on the motor end plate rapidly decomposes the acetylcholine

secondly, calcium is returned to the sarcoplasmic reticulum, using ATP as an energy source

3rd ATP now binds to the myosin heads breaking the linkages between myosin and actin

finally the actin returns to its original position and the muscle relaxes

61
Q

what is a myogram

A

is the recording of an electrically stimulated muscle contraction

62
Q

definition of latent period

A

brief delay of between the stimulation and beginning of the contraction

63
Q

latent period is followed by?

A

by a period of contraction and a period of relaxation

64
Q

what is all or none response

A

when a muscle fibre contracts it contracts to its full extent

65
Q

muscle consist of a combination of both types:

A
  • fatigue resistant slow twitch fibres
    -fatigable fast twitch fibres
66
Q

describe partial tetany

A

when exposed to higher frequency of stimulation, relaxation time becomes very short

67
Q

describe complete tetanic contraction

A

if the frequency of stimulation is very high and the sustained contraction lacks any relaxation

68
Q

partial tetany occurs in the body what about complete tetany

A

no it can only be accomplished in a lab

69
Q

what is recruitment

A

an increase in the number of activated motor units within a muscle at higher intensities of stimulation

70
Q

summation and recruitment together can produce what

A

sustained contraction of increasing strength

71
Q

muscle tone is achieved by what?

A

a continues state of sustained contraction of a few motor units at a time within a muscle

72
Q

muscle tone is important for?

A

maintenance of posture

73
Q

types of smooth muscle cell

A
  • multiunit smooth muscle
    -visceral smooth muscle
74
Q

describe multi smooth muscle

A

in blood vessels and iris of the eye, fibres occur separately rather than sheets; stimulated by neurons and some hormones

75
Q

describe visceral smooth muscle

A

occurs in sheets and is found in the walls of hollow organs; these fibres can stimulate one another and display rhythmicity; these features accomplish peristalsis in tubular organs

76
Q

name similarities between smooth and skeletal muscle contraction

A
  • both involve reaction between actin and myosin
  • both are stimulated by membrane impulses, require an increase in calcium ions in the cells, and use ATP energy
77
Q

describe differences smooth and skeletal muscle contraction

A
  • both Ach and norepinephrine stimulate and inhibit Smooth muscle contraction while only Ach stimulates skeletal muscle

-hormones can stimulate or inhibit contraction of smooth muscle but not skeletal muscle

  • smooth muscle is slower to contract or relax

-

78
Q
A

Reproduction (8 decks)

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