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MSK SB > Physiology > Flashcards

Physiology Flashcards

1
Q

what are the 3 types of muscles

A

skeletal
cardiac
smooth

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2
Q

which type of muscles are striated

A

skeletal

cardiac

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3
Q

striation can be visualised under a microscope as alternating dark and light bands - what causes the colour

A

dark - myosin

light - actin

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4
Q

what nervous system supplies each type of muscle

A

skeletal - somatic (voluntary control)

smooth and cardiac - autonomic (involuntary)

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5
Q

what are the physiological functions of skeletal muscles

A 
maintenance of posture
movement
respiratory movements
heat production
whole body metabolism
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6
Q

skeletal muscle fibres are organised into motor units - what is a motor unit

A

single alpha motor neuron and all the skeletal muscle fibres it innervates

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7
Q

muscles which serve fine movements have more fibres per motor unit - true or false

A

false

they have fewer fibres per motor unit

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8
Q

why is there fewer fibres per motor unit in muscles involved in fine movements

A

precision more important than power

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9
Q

when power is more important than precision, how many fibres are in a muscle per motor unit

A

hundreds to thousands

e.g. thigh muscles

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10
Q

what is the functional unit of skeletal muscles

A

sarcomere

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11
Q

which type of muscles has gap junctions - cardiac or skeletal

A

cardiac

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12
Q

where does the skeletal muscle get calcium from

A

entirely from sarcoplasmic reticulum

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13
Q

where does cardiac muscle get calcium from

A

ECF and sarcoplasmic reticulum

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14
Q

what is excitation contraction coupling

A

process whereby the surface action potential results in activation of the contractile mechanisms of the muscle fibre

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15
Q

in skeletal muscle, when is calcium released from the lateral sacs of the SR

A

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

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16
Q

steps to contraction of muscle

A

1 - ACh released by axon of motor neurone and binds to receptor
2- AP generated in response and moves down T tubules of muscle cell
3 - AP in T tubule triggers calcium release from SR
4 - calcium ions released from lateral sacs bind to troponin on actin filaments
5 - tropomyosin moved aside to uncover cross-bridge binding sites on actin
6 - myosin cross bridges attach to actin filaments toward centre of sacromere (powered by ATP)
7 - calcium taken up by SR when there is no longer a AP
8 - when calcium no longer bound to troponin, tropomyosin moves to block actin binding site again.
Contraction ends

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17
Q

there is continuity of cytoplasm between nerve and skeletal muscle cells - true or false

A

false

there is NO continuity

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18
Q

what is the transmitter at neuromuscular junctions

A

ACh

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19
Q

what triggers the release of Ca2+ from lateral sacs of SR

A

spread of AP down the T-tubules

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20
Q

what does muscle fibre contain

A

myofibrils

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21
Q

what are myofibrils composed of

A

thin and thick protein
thin - actin (lighter)
thick - myocin (darker)

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22
Q

what are actin and myocin arranged as

A

sacromeres

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23
Q

where is the sarcomere found

A

between two Z lines

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24
Q

what are the 4 zones of sarcomere

A

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

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25
Q

what is the A band

A

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

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26
Q

what is the H zone

A

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

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27
Q

what is the M-line

A

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

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28
Q

what is the I-band

A

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

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29
Q

how is muscle tension produced

A

sliding of actin filaments on myosin filaments

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30
Q

what is required for muscle movement

A

ATP - for contraction and relaxation

Ca2+ - to switch on cross bridge formation

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31
Q

how does calcium switch on cross bridge formation

A

Ca2+ binds to troponin. This results in repositioning of
troponin-tropomyocin
complex to uncover the cross bridge binding sites on actin

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32
Q

when is the actin binding site covered by the troponin-tropomyosin complex

A

when muscle fibres are relaxed

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33
Q

what is required for a stronger contraction

A

stimulation of more motor units

- motor unit recruitment

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34
Q

what helps prevent muscle fatigue

A

a synchronous motor unit recruitment during sub maximal contractions

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35
Q

what factors are responsible for tension developed by each contracting muscle fibre

A
  • freq of stimulation and summation of contractions
  • length of muscle fibres at the onset of contraction
  • thickness of muscle fibre
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36
Q

what is the basic physiological rule in skeletal muscles

A

the duration of AP is much shorter than the duration of resulting twitch
therefore possible to summate stronger contractions through repetitive fast stimulation

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37
Q

what is tetanus

A

muscle fibre is stimulated so rapidly that it does not have time to relax at all between stimuli it reaches a maximal sustained contraction

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38
Q

why can cardiac muscle not be tentanised

A

due to a long refractory period

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39
Q

what is it called when a skeletal muscle is stimulated once and why is it useless

A

single contraction is called twitch

produces little tension which is not useful for meaningful skeletal muscle activity

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40
Q

how can the response be amplified

A

second stimulation before it has had time to completely relax

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41
Q

how can tension developed by skeletal muscle increase

A

increasing frequency of stimulation

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42
Q

how is a sustained and much stronger contraction produced

A

skeletal muscle is stimulated very rapidly with no opportunity to relax between stimuli

43
Q

when can maximal tetanic contraction be achieved

A

when muscle is at optimal length before onset of contraction

44
Q

what does developed tension depend on

A

initial length of skeletal muscle fibre

45
Q

the resting length of a skeletal muscle is NOT its optimal length - true or false

A

false

it is

46
Q

what are the two types of skeletal muscle contraction

A

isotonic

isometric

47
Q

what is isotonic contraction

A

used for body movements and for moving objects

muscle tension remains constant as the muscle length changes

48
Q

what is isometric contraction

A

used for supporting objects in fixed position and for maintaining body posture
muscle tension develops at constant muscle length

49
Q

what is the rule for the velocity of muscle shortening

A

The velocity of muscle shortening decreases as the load increases

50
Q

what is the stretch reflex

A

the simplest monosynaptic spinal reflex

negative feedback that resists passive change in muscle length to maintain optimal resting length of muscle

51
Q

what is the pathway of the stretch reflex

A

sensory receptor i.e. muscle spindle activated by muscle stretch.
Increase firing in the afferent neurones
Synapse in the spinal cord with the alpha motor neurones (efferent limb)
Innervate the stretched muscle

52
Q

what needs to happen for the stretch reflex to happen

A

the antagonist muscle must relax

53
Q

what spinal segment and peripheral nerve are responsible for the knee, ankle, biceps, brachioradialis and triceps jerk

A 
Knee - L3,L4 - Femoral Nerve
Ankle - S1,S2 - Tibial nerve
Biceps - C5-C6- Musculocutaneous nerve
Brachioradialis - C5-C6- Radial nerve
Triceps - C6,C7 - Radial nerve
54
Q

what are muscle spindles and where are they found

A

collection of specialised muscle fibres that have sensory nerve endings
found within belly of muscles are run parallel to ordinary muscle fibres

55
Q

when does the discharge from the muscle spindles increases

A

when the muscle is stretched

56
Q

what supplies the muscle spindles

A

gamma motor neurones
adjust level of tension in the muscle spindles to maintain their sensitivity when the muscle shorten during muscle contraction

57
Q

what are the main differences between different types of skeletal muscles

A

the enzymatic pathways for ATP synthesis
resistance to fatigue (muscles with greater capacity to synthesis ATP are more resistant to fatigue)
activity of myosin ATPase

58
Q

what are the metabolic pathways suppling ATP in muscle fibres

A

Glycolysis
Oxidative phosphorylation
Transfer of high energy phosphate from creatine phosphate to ADP

59
Q

what are the 3 types of muscle fibres

A

Type I - slow oxidative
Type IIa - fast oxidative
Type IIx - fast glycolytic

60
Q

what are Type I muscle fibres used for

A

a.k.a slow-twitch fibres

prolonged relatively low work aerobic activities e.g. maintenance of posture, walking

61
Q

what are Type IIa muscle fibres used for

A

a.k.a intermediate-twitch fibres
used for both aerobic and anaerobic metabolism in prolonged relatively moderate work
e.g. jogging

62
Q

what are Type IIx fibres used for

A

a.k.a fast twitch fibres
anaerobic metabolism and used for short term high intensity activities
e.g. jumping

63
Q

what is the pathway of innovation for skeletal muscles

A

Myelinated motor neurone&raquo_space;> unmyelinated branches&raquo_space;> each branch innervates an individual skeletal muscle cell within a muscle (neurone + no. of fibres = motor unit) &raquo_space;> multiple fine branches

64
Q

what do the multiple fine branches end with

A

terminal bouton that forms a chemical synapse with the neuromuscular junction

65
Q

what are the 3 types of joint

A

synovial
fibrous
cartilaginous

66
Q

what are fibrous joints

A

bones united by fibrous tissue
doesn’t allow movement
e.g. skull

67
Q

what are cartilaginous joints

A

bones united by cartilage
allow limited movement
e.g. intervertebral discs, pubic symphasis

68
Q

what are synovial joints

A

bones separated by a cavity and united by a fibrous capsule lined by synovial membrane

69
Q

what does the synovial membrane contain

A

synovial cells (fibroblasts) which produce synovial fluid

70
Q

what is the difference between simple and compound synovial joints

A

simple - one pair of articular surfaces

compound - more than one pair of articular surfaces

71
Q

functions of synovial fluid

A 
lubricates joint
facilitates joint movements 
minimise wear and tear of joints
aids nutrition of articular cartilage 
supplies the chondrocytes with oxygen and nutrients and removes CO2 and waste product
72
Q

why does synovial fluid have a high viscosity

A

due to presence of hyaluronic acid produced by synovial cells

73
Q

what is rapid movement associated with in reference to synovial fluid

A

decreased viscosity
increased elasticity
these properties become defecting in diseased joints e.g. OA

74
Q

when would synovial fluid be red instead of colourless

A

hemorrhagic arthritis

75
Q

when would the WBC count increase in synovial fluid

A

inflammatory and septic arthritis

76
Q

what is hyaline cartilage composed off

A

ECM predominantly of water, type II collagen and proteoglycans

77
Q

where is proteoglycan found in cartilage and what is it composed of

A

highest conc in middle and deep zone

composed of glycosaminoglycan

78
Q

what synthesis and degrades ECM

A

Chondrocytes

79
Q

articular cartilage has a rich blood supply - true or false

A

false

is avascular; receives nutrients and O2 from synovial fluid

80
Q

when would joint disease occur

A

rate of ECM degradation exceeds the rate of its synthesis

81
Q

what are the catabolic and anabolic factors of cartilage matrix turnover

A

catabolic - Stimulate proteolytic enzymes and inhibit proteoglycan synthesis. e.g. Tumour necrosis factor (TNF)-α and Interleukin (IL)-1
Anabolic - Stimulate proteoglycan synthesis and counteract effects of IL-1 e.g. Tumour growth factor (TGF)-β and Insulin-like growth factor (IGF)-1

82
Q

what are markers of cartilage degradation

A

type II collagen in synovial fluid

serum and synovial keratin sulphate

83
Q

where do the terminal (bouton) synapse

A

the endplate region of skeletal muscle fibres

84
Q

what is the pre-synaptic process of skeletal muscle

A
  • choline transported into terminal by choline transporter
  • ACh synthesised in cytosol from choline and acetyl CoA by enzyme CAT
  • stored in vesicle
85
Q

what happens in cell once AP arrives

A

depolarisation and opening of voltage-activated calcium channels
thus allowing entry of calcium to the terminal causing vesicles to fuse with presynaptic membrane

86
Q

what happens after vesicles fuse with presynaptic membrane

A

ACh diffuses into the synaptic cleft to activate post synaptic nicotinic ACh receptors in the endplate region

87
Q

what is the post-synaptic process

A

opens central gate with two molecules of ACh - allows Na to enter (influx) and potassium to exit (efflux)
influx of sodium greater than efflux of potassium

88
Q

what does the greater influx of sodium cause

A

depolarisation known as the end plate potential

89
Q

what is a miniature endplate potential (m.e.p.p)

A

electrical response to one quantum of transmitter, due to activation of nicotinic ACh receptors at the end plate

90
Q

in what fashion does the e.p.p. elicit a response

A

all or none propagated AP

91
Q

what does the e.p.p trigger

A

opening of voltage activated sodium channels causing a muscle action potential

92
Q

how does the muscle AP cause contraction

A

by the release of Calcium from intracellular stores

93
Q

how is the action of ACh terminated

A

by AChE

hydrolyses ACh to choline (picked up by choline transporter) and acetate (diffuses from synaptic cleft)

94
Q

what are the 3 types of pain

A

nociceptive, inflammatory, pathological

95
Q

nociceptive pain caused by nociceptive receptors has a low threshold - true or false

A

false

has high threshold provoked only by intense stimuli

96
Q

what does a trigger of the nociceptive receptors/pain cause

A

withdrawal reflex (moving hand away from something hot)

97
Q

why do we have inflammatory pain

A

caused by immune system
discourages physical contact
discourages movement
promotes repair

98
Q

how is pathological pain differ form inflammatory pain

A

no protective function

results from abnormal nervous system function

99
Q

what are the subtypes of nociceptor

A

Aδ-fibres are mechanical/thermal nociceptors that are thinly myelinated
C-fibres are nociceptors that are unmyelinated

100
Q

which type of fibre response to fast and ‘first’ pain

A

Aδ-fibres

101
Q

3 types of stimuli

A

mechanical, thermal or chemical

102
Q

how is the amplitude of generator potential graded in pain

A

proportional to stimulus intensity

103
Q

outline of neurogenic inflammation

A

1 - peptides (SP and CGRP) released from free nerve endings due to damage/trauma
2 - SP causes vasodilation, release of histamine from mast cells
3 - CGRP induces vasodilation
4 - primary + secondary hyperalgesia and allodynia

MSK SB (15 decks)

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