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MSK 2.0 > Physiology > Flashcards

Physiology Flashcards

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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
define reflex
stereotyped response to a specific stimulus
26
what kind of reflex is the stretch reflex?
monosynaptic spinal reflex
27
describe the stretch reflex
- 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
two cases of intrinsic disease of muscle
1. genetically determined myopathies | 2. acquired
29
examples of genetically determined myopathies
congenital chronic degradation abnormalities in muscle membrane ion channels e.g. myotonia
30
examples of acquired intrinsic muscle disease
inflammatory non-inflammatory endocrine toxins
31
three types of joint
1. fibrous (synarthrosis) 2. cartilaginous (amphiarthrosis) 3. synovial (diarthrosis)
32
describe fibrous joints
bones united by fibrous tissue no movement e.g. adult skull
33
describe cartilaginous joints
bones united by cartilage limited movement e.g. vertebrae
34
describe synovial joints
bone separated by a cavity (containing synovial fluid) and united by fibrous capsule with the synovial membrane
35
what does the synovial membrane contain?
vasculature lymphatics synovial cells (fibroblasts) that produce synovial fluid
36
what are the articular surfaces of bone in a synovial joint covered with?
hyaline cartilage
37
two types of synovial joint
- simple= one pair of articular surfaces | - compound= more than one pair of articular surfaces
38
how do the joints do their role of support and movement?
``` stress distribution (load taken by muscles and tendons) confer stability (synovial fluid allows sliding) joint lubrication (cartilage interstitial fluid- synovial HA and lubrcin) ```
39
functions of synovial fluid
- lubricate joint and facilitate movement, reducing wear and tear - supply chondrocytes with oxygen and nutrients and remove CO2 and waste
40
what is synovial fluid replenished by
synovial membrane
41
structure of synovial fluid?
high viscosity due to presence of HA (mucin) | other components are derived from dialysis of blood plasma (mononuclear leucocytes)
42
variation of synovial fluid viscosity with movement
rapid movement decreases viscosity
43
functions of articular cartilage
- low friction reducing wear and tear | - distributes contact pressure to subchondral bone
44
what is the ECM in articular cartilage made up of?
- 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
as cartilage is avascular what does the articular cartilage of synovial joints receive nutrients from?
synovial fluid replenish chondrocytes
46
factors that affect replenishment of cartilage
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
markers of cartilage degradation
serum keratin sulphate and type II collagen
48
four ways a joint can go wrong?
- 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
define pain
unpleasant sensory and emotional experience
50
four distinct phases of pain
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
describe nociceptors
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
what is the anterolateral system comprised of?
- spinothalamic tract= pain perception (location and intensity) - spinoreticular tract= autonomic responses e.g. fear and emotion
53
where does the pain pathway terminate?
terminates in thalamus where a third order neurone relays to primary sensory cortex
54
neurotransmitters between the first and second order neurones in the pain pathway
glutamate and peptides (substance P and neurokinin A)
55
two types of nociceptors
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
three types of pain
1. nociceptive 2. inflammatory 3. pathological
57
describe nociceptive pain
normal response adaptive function to protect and avoid harmful stimuli
58
describe inflammatory pain
activation of the immune system variety of mediators cause hyperalgesia and allodynia discourages contact and aids repair
59
two types of pathological pain
- neuropathic: damage to neural tissue e.g. compress neuropathies - dysfunctional e.g. no identifiable damage e.g. IBS
60
define referred pain
pain felt in a site distant from origin. caused by convergence of visceral and skin afferents upon the same spinothalamic neurones
61
two bands in the myofibril?
A-band and I-band
62
what is the A-band made up of?
thick filaments with portion of thin filaments that overlap at the end
63
what is the H-zone
lighter area in the middle of the A-band where thin filaments don't reach
64
what does the I-band consist of?
remaining portion of thin filaments that do not project in A-band
65
where is the M-line?
extends down the middle of the A-band
66
what is the M-line in the centre of?
H-zone
67
what is the Z-line to Z-line?
sacromere

MSK 2.0 (10 decks)

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