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MSK 2.0 > Physiology > Flashcards

Physiology Flashcards

1
Q

what are skeletal muscle fibres organised into?

A

motor units

myofibrils and sarcomeres (Z-line to Z-line)

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2
Q

what does a motor unit consist of?

A

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

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3
Q

what are skeletal muscles controlled by?

A

somatic nervous system

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4
Q

how does the somatic nervous system reach skeletal muscle fibres?

A

neuromuscular junctions (ACh)

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5
Q

how are neuromuscular junctions formed?

A

axon of the motor neurone branches

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6
Q

what does the AP spread down in muscle fibres?

A

T-tubules

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7
Q

what are T-tubules?

A

extensions of the surface membrane

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8
Q

what are T-tubules in close apposition to?

A

lateral sacs of SR which contain Ca2+

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9
Q

role of Ca2+ in skeletal muscle fibre contraction

A

it binds to troponin on actin filaments leading to movement of tropomyosin to uncover the actin binding site

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10
Q

what binds to the uncovered actin binding site?

A

myosin cross bridges and ATP allows contraction

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11
Q

what is ATP used for in muscle contraction?

A

contraction of myosin attached to actin
release cross bridges
to take up Ca2+ in the SR

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12
Q

what does gradation of skeletal muscle tension depend on?

A
  • number of muscle fibres (motor unit recruitment helps prevent fatigue)
  • tension developed by each contracting fibre: stimulation, length (optimal is resting) and thickness
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13
Q

why can twitches be summated?

A

the AP is shorter than the duration of the muscle twitch

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14
Q

how are twitches summated

A

the skeletal muscle receives a second stimulation before it has time to completely relax, the responses are combined to produce greater tension

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15
Q

what happens if the skeletal muscle has no opportunity to relax?

A

tetanus is produced

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16
Q

two types of skeletal muscle contraction

A
  1. isotonic

2. isometric

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17
Q

describe isotonic muscle contraction

A

used for movement

muscle tension remains constant as muscle length changes

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18
Q

describe isometric muscle contraction

A

body posture

muscle tension develops at a constant muscle length

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19
Q

how is tension transmitted from muscle to bone?

A

via elastic components of muscle

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20
Q

list the metabolic pathways for ATP used by the muscle

A

creatine phosphate
oxidative phosphorylation
glycolysis

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21
Q

three types of muscle fibre

A
  1. slow oxidative type 1 fibres (slow twitch)
  2. fast oxidative type IIa fibres (intermediate)
  3. fast glycolytic type IIb (fast twitch)
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22
Q

describe slow twitch muscle fibres

A

prolonged low aerobic work using oxidative metabolism

abundance of mitochondria and myoglobin, resistant to fatigue e.g. walking

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23
Q

when are intermediate muscle fibres used?

A

moderate activity e.g. jogging

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24
Q

describe fast twitch fibres

A

use anaerobic metabolism

high intensity e.g. jumping

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25
Q

define reflex

A

stereotyped response to a specific stimulus

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26
Q

what kind of reflex is the stretch reflex?

A

monosynaptic spinal reflex

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27
Q

describe the stretch reflex

A
  • sensory receptor is muscle spindle (intrafusal fibres) that is activated by muscle stretch
  • firing in afferent neurone that have nerve endings called annulospiral fibres
  • efferent motor nerve supply are gamma motor neurones that adjust level of tension
  • synapse in spinal cord with alpha motor neurones
28
Q

two cases of intrinsic disease of muscle

A
  1. genetically determined myopathies

2. acquired

29
Q

examples of genetically determined myopathies

A

congenital
chronic degradation
abnormalities in muscle membrane ion channels e.g. myotonia

30
Q

examples of acquired intrinsic muscle disease

A

inflammatory
non-inflammatory
endocrine
toxins

31
Q

three types of joint

A
  1. fibrous (synarthrosis)
  2. cartilaginous (amphiarthrosis)
  3. synovial (diarthrosis)
32
Q

describe fibrous joints

A

bones united by fibrous tissue
no movement
e.g. adult skull

33
Q

describe cartilaginous joints

A

bones united by cartilage
limited movement
e.g. vertebrae

34
Q

describe synovial joints

A

bone separated by a cavity (containing synovial fluid) and united by fibrous capsule with the synovial membrane

35
Q

what does the synovial membrane contain?

A

vasculature
lymphatics
synovial cells (fibroblasts) that produce synovial fluid

36
Q

what are the articular surfaces of bone in a synovial joint covered with?

A

hyaline cartilage

37
Q

two types of synovial joint

A
  • simple= one pair of articular surfaces

- compound= more than one pair of articular surfaces

38
Q

how do the joints do their role of support and movement?

A 
stress distribution (load taken by muscles and tendons)
confer stability (synovial fluid allows sliding)
joint lubrication (cartilage interstitial fluid- synovial HA and lubrcin)
39
Q

functions of synovial fluid

A
  • lubricate joint and facilitate movement, reducing wear and tear
  • supply chondrocytes with oxygen and nutrients and remove CO2 and waste
40
Q

what is synovial fluid replenished by

A

synovial membrane

41
Q

structure of synovial fluid?

A

high viscosity due to presence of HA (mucin)

other components are derived from dialysis of blood plasma (mononuclear leucocytes)

42
Q

variation of synovial fluid viscosity with movement

A

rapid movement decreases viscosity

43
Q

functions of articular cartilage

A
  • low friction reducing wear and tear

- distributes contact pressure to subchondral bone

44
Q

what is the ECM in articular cartilage made up of?

A
  • water (70%): most near articular surface, decreases with age
  • collagen (20%): type II provides strength, decreases with age, 3D meshwork (type I is thicker and in linear bundles)
  • proteoglycan (10%): glycosaminoglycan (GAGs) e.g. chondroitin sulphate and keratin sulphate bound to a core protein linked to hyaluronan
45
Q

as cartilage is avascular what does the articular cartilage of synovial joints receive nutrients from?

A

synovial fluid replenish chondrocytes

46
Q

factors that affect replenishment of cartilage

A

catabolic: proteolytic enzymes and inhibition of proteoglycan synthesis (TNF-alpha and IL-1)
anabolic: stimulate proteoglycan synthesis and counteract IL-1 (TFG-beta and IGF-1)

47
Q

markers of cartilage degradation

A

serum keratin sulphate and type II collagen

48
Q

four ways a joint can go wrong?

A
  • excessive wear and tear= OA
  • synovial cell proliferation and inflammation= RA
  • deposition of crystals e.g. uric acid gout or calcium pyrophosphate pseudogout
  • inflammation of periarticular structures e.g. soft tissue rheumatism
49
Q

define pain

A

unpleasant sensory and emotional experience

50
Q

four distinct phases of pain

A
  1. transduction- translation of noxious stimulus into electrical activity at nociceptor
  2. transmission- propagation of pain signal as nerve impulses
  3. modulation- modification of pain transmission e.g. opioids
  4. perception- conscious experience e.g. behaviours
51
Q

describe nociceptors

A

these are primary sensory afferent neurones activated by noxious stimuli (mechanical, thermal or chemical)
they are first order neurones that relay information to second order neurones that ascend the spinal cord in the anterolateral system

52
Q

what is the anterolateral system comprised of?

A
  • spinothalamic tract= pain perception (location and intensity)
  • spinoreticular tract= autonomic responses e.g. fear and emotion
53
Q

where does the pain pathway terminate?

A

terminates in thalamus where a third order neurone relays to primary sensory cortex

54
Q

neurotransmitters between the first and second order neurones in the pain pathway

A

glutamate and peptides (substance P and neurokinin A)

55
Q

two types of nociceptors

A

A delta-fibres=mechanical/thermal nociceptors, thinly myelinated. mediate fast pain.
C-fibres= unmyelinated that respond to all noxious stimuli (polymodal). mediate slow pain

56
Q

three types of pain

A
  1. nociceptive
  2. inflammatory
  3. pathological
57
Q

describe nociceptive pain

A

normal response
adaptive
function to protect and avoid harmful stimuli

58
Q

describe inflammatory pain

A

activation of the immune system
variety of mediators cause hyperalgesia and allodynia
discourages contact and aids repair

59
Q

two types of pathological pain

A
  • neuropathic: damage to neural tissue e.g. compress neuropathies
  • dysfunctional e.g. no identifiable damage e.g. IBS
60
Q

define referred pain

A

pain felt in a site distant from origin. caused by convergence of visceral and skin afferents upon the same spinothalamic neurones

61
Q

two bands in the myofibril?

A

A-band and I-band

62
Q

what is the A-band made up of?

A

thick filaments with portion of thin filaments that overlap at the end

63
Q

what is the H-zone

A

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

64
Q

what does the I-band consist of?

A

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

65
Q

where is the M-line?

A

extends down the middle of the A-band

66
Q

what is the M-line in the centre of?

A

H-zone

67
Q

what is the Z-line to Z-line?

A

sacromere

MSK 2.0 (10 decks)

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