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msk > physiology > Flashcards

physiology Flashcards

1
Q

which muscles are striated

A

skeletal
cardiac

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2
Q

what are motor units

A

single alpha motor neurone and all the skeletal muscle it innervates

> skeletal muscle fibres are organised into motor units

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3
Q

how many muscle fibre cells in a motor unit

A

depends on the functions served by the skeletal muscle ie strength or precision

> muscles which serve fine movements eg external eye muscles or muscle of facial expression have fewer intrinsic fibres than muscles that need power ie vastus medialis

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4
Q

what is a functional unit

A

sarcomere is the functional unit of skeletal muscle

-the smallest component capable of performing all the functions of that organ

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5
Q

functions of skeletal muscle

A

posture
movement
breathing
heat prod.
whole body metabolism

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6
Q

3 types of muscle tissue

A

skeletal
cardiac
smooth

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7
Q

what is the ‘voluntary’ muscle

A

skeletal

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8
Q

how can striation be visualised

A

myosin and actin filaments

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9
Q

what innervates skeletal

A

somatic -

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10
Q

what innervates cardiac and smooth

A

-

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11
Q

initiation and propagation of skeletal muscle

A

neurogenic
motor units
neuromuscular junction present
No gap junctions

calcium comes entirely from sarcoplasmic reticulum

> no continuity of cytoplasm between nerve and skeletal muscle cells

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12
Q

initiation and propagation of cardiac muscle

A

myogenic
no neuromuscular junction
gap junctions present

calcium comes from ECF and sarcoplasmic reticulum

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13
Q

what is a myofibril

A

specialised intracellular structure involved in contraction and is organised into sarcomeres

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14
Q

how many bands does the sarcomere have

A

4 bands :
A band
H zone
M line
I band

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15
Q

what is excitation contraction coupling

A
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16
Q

where is calcium released from in skeletal muscle fibres

A

lateral sacs of sarcoplasmic reticulum

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17
Q

why is calcium required

A

to switch on cross bridge formation
-it is the link between excitation and contraction
-is entirely derived from sarcoplasmic reticulum in skeletal muscles

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18
Q

what is the difference between actin myosin / excitation /calcium contraction in cardiac muscle and skeletal muscle

A

?

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19
Q

what is skeletal muscle contraction initiated by

A

neurogenic initiation

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20
Q

what is the transmitter at the neuromuscular junction

A

acetylcholine

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21
Q

why is ATP needed

A

contraction: to power cross bridges

relaxation:
release cross bridges and to pump Ca back into sarcoplasmic reticulum (rigor mortis)

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22
Q

what are the two influences that act on tension developed by skeletal muscle

A

-the no of muscle fibres contracting
-the tension developed by each contracting muscle fibres

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23
Q

how does frequency of stimulation and summation of contractions brings about increased tension in skeletal muscle

A
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24
Q

describe the two primary types of skeletal muscle contraction

A
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25
Q

what can develop at optimum muscle length

A

maximum muscle tension

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26
Q

what is a reflex action

A

stereotyped response to a specific stimulus

they are the simplest form of coordinated movement

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27
Q

why might you get impairment of muscle function

A

intrinsic muscle disease
neuromuscular junction disease
pathology of lower motor neurons
disruption of input to motor nerves

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28
Q

what allows for simultaneous contraction of a number of muscle fibres

A

motor units

28
Q

what allows for simultaneous contraction of a number of muscle fibres

A

motor units

29
Q

how might a stronger contraction be achieved

A

motor unit recruitment

30
Q

what helps prevents muscle fatigue during sub maximal contraction

A

asynchronous motor unit recruitment

31
Q

what are the factors affecting tension developed by each contraction muscle fibre

A

-thickness
-length of muscle fibre
-frequency of stimulation and summation

32
Q

twitch summation and tetanus in skeletal muscle

A
33
Q

what happens when skeletal muscle is stimulated once

A

a single contraction called a twitch is produced

34
Q

what happens when skeletal muscle receives a second stimulation before it had time to completely relax

A

the second response is much greater…

35
Q

T or F : the resting length of skeletal muscle is the optimal length

A

T

36
Q

what are the 2 types of skeletal muscle contraction

A

isotonic = muscle tension remains constant as the muscle length changes, useful for body movements and moving objects

isometric = muscle tension develops at constant muscle length , useful in supporting objects in fixed position and for maintaining body posture

37
Q

what are the main differences between skeletal muscle fibres

A
  1. enzymatic pathways for ATP synthesis
  2. resistance to fatigue (muscle fibres with greater capacity to synthesise ATP are more resistant to fatigue)
  3. activity of myosin ATPase - this determines the speed at which energy is made available - the speed of contraction
38
Q

how many types of fibres does a motor unit usually have

A

one

39
Q

the three types of skeletal muscle fibres

A

slow oxidative - slow twitch ie walking , aerobic
fast oxidative - intermediate twitch ie aerobic and anaerobic , jogging
fast glycolytic - fast twitch ie sprinting , anaerobic

40
Q

why are neural pathways for reflexes important

A

can help to localise lesions

41
Q

the stretch reflex

A

negative feedback mechanism
that resists p

passive changes in muscle length to maintain optimal resting length of muscle

helps maintain posture

the sensory receptor is the muscle spindle and is activated by muscle strength

stretching the muscle spindle increases firing in the afferent neurons

42
Q

where do the afferent neurons synapse

A

in the spinal cord

43
Q

intrafusal vs extrafusal

A
44
Q

what are muscle spindles

A

collection of specialised muscle fibres

45
Q

causes of intrinsic muscle disease

A

genetically determined myopathies :
congenital
chronic degeneration - dystrophy
abnormalities in muscle membrane ion channels - myotonia

acquired :
inflammatory
non-inflammatory
endocrine
toxic - alcohol

46
Q

symptoms of muscle disease

A

muscle weakness / tiredness
stiffness
-

47
Q

useful investigation

A

creatinine kinase
nerve conduction studies
inflammatory marker
biopsy
EMG

48
Q

what are the joints of the body

A

synovial
fibrous
cartilaginous

49
Q

do fibrous joints allow movement

A

doesn’t allow movement

50
Q

do cartilaginous joints allow movement

A

allow limited movement ie intervertebral discs , pubic symphysis

51
Q

features of the synovial joints

A

the bones are separated by a cavity - filled with synovial fluid -
and united by a fibrous capsule

52
Q

what is the inner aspect of fibrous capsule (of synovial joints) lined with

A

synovial membrane

53
Q

what is the synovial membrane

A

vascular connective tissue (with capillary networks and lymphatics)

-contains synovial cells (fibroblasts) which produces the synovial fluid

  • about 60um thick in the human knee
54
Q

what is a simple synovial joint

A

one pair of articular surfaces ie metacarpophalangeal

55
Q

what is a compound synovial joint

A

more than one pair of articular surfaces eg elbow joint

56
Q

purposeful function of joints

A

stress distribution

confer stability

joint lubrication ie cartilage interstitial fluid

57
Q

synovial fluid features

A

> continuously replenished and absorbed by synovial membrane ie not a static pool

> has a high viscosity - due to presence of hyaluronic acid produced by the synovial cells

> viscosity and elasticity varies with joint movement

58
Q

what happens to viscosity and elasticity in rapid movements

A

viscosity decreases
elasticity increases

59
Q

what happens to synovial fluid when in a traumatic synovial tap (and also in haemorrhagic arthritis)

A

turns red

60
Q

what should normal synovial fluid look like

A

clear colourless and viscous

normally has less than 200WBC

61
Q

what does synovial fluid look like from a severely inflamed joint

A

thin and opaque

62
Q

main functions of articular cartilage

A

prevents wear and tear - low friction lubricated gliding surfaces

distributes contact pressure to subchondral bone

the composition of the cartilage ECM and interaction between the fluid and solid phase of the cartilage determines the mechanical properties of cartilage

63
Q

structural properties of articular cartilage

A

> elastic and sponge like - usually hyaline

> covers articular surfaces of bones

> has special ECM made predominantly of water and collagen , also proteoglycans

water: maintains resiliency of tissues and contribute to the nutrition and lubrication system

collagen: provides tensile stiffness and strength

proteoglycan: provides compressive properties associated with load bearing

64
Q

specialised ECM of articular cartilage

A

synthesised, organised and degraded by chondrocytes

avascular - so has poor healing

in normal joints the rate at which the ECM is degraded doesn’t exceed the rate at which it is replaced
(joint disease can occur if the rate of ECM degradation exceeds the rate of its synthesis)

65
Q

catabolic factors of ECM synthesis

A

they stimulate proteolytic enzymes and inhibit proteoglycan synthesis

66
Q

what may go wrong in a joint

A

cartilage and synovial composition and function deteriorate with age and repeated wear and tear giving rise to osteoarthritis

synovial cell proliferation and inflammation > arthritis

deposition of salt crystals

injury and inflammation to periarticular structures cause soft tissue rheumatism

67
Q

anabolic factors of ECM synthesis

A

stimulate proteoglycan synthesis and counteract effects of interleukin-1

msk (24 decks)

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