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MSK > Physiology > Flashcards

Physiology Flashcards

1
Q

What are the physiological functions of skeletal muscles?

A 
Maintenance of posture
Purposeful movement in relation to external environment
Resp movements
Heat production 
Contribution to whole body metabolism
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2
Q

Which muscles are striated?

A

Skeletal and cardiac

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3
Q

Which muscles are involuntary?

A

Cardiac muscle

Smooth muscle

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4
Q

What nerves innervate skeletal muscles?

A

Somatic nervous system

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5
Q

What nerves innervate cardiac and smooth muscle cells?

A

Autonomic nervous system

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6
Q

How are skeletal muscles initated and propagated for contraction?

A

Neurogenic intiation of contraction
Motor units
Neuromuscular junction present
NO gap junctions

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7
Q

How are cardiac muscle cells initiated and propagated for contraction?

A

Myogenic (pacemaker potential)
NO neuromuscular junction
Gap junctions present

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8
Q

What is the neurotransmitter at the neuromuscular junction in skeletal muscle cells?

A

Acetylcholine

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9
Q

What is a motor unit?

A

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

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10
Q

What determines the number of muscles fibers per motor unit?

A

Depends on the functions served by the muscle e.g. muscles which serve fine movements such as external eye muscles, muscles of facial expression and intrinsic band muscles have fewer fibres per motor unit

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11
Q

What makes up a sarcomere?

A

Actin (thin and light)

Myosin (thick and dark)

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12
Q

What is the Z line?

A

Connection of actin filaments of 2 adjoining sarcomeres

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13
Q

What is the A band?

A

Myosin filaments along with portions of actin filaments that overlap both ends of myosin filament

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14
Q

What is the H zone?

A

Lighter area within the middle of the A band where actin filaments dont reach

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15
Q

What is the M line?

A

Extends vertically down the centre of the H zone

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16
Q

What is the I band?

A

Consists of remaining portion of actin filaments that do not project into the A band

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17
Q

What is excitation contraction coupling?

A

Process whereby the surface action potential results in activation of the contractile structures of the muscle fibre

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18
Q

When will calcium be released from the lateral sacs of the SR?

A

When the surface action potential spreads down the transverse T tubules

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19
Q

What is a T-tubule?

A

Extensions of the surface membrane that dip into the muscle fibre

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20
Q

What is the action of calcium in muscle contraction?

A

When relaxed, the cross binding site on actin is covered by the troponin-tropomyosin complex
When Ca binds with troponin, it pulls the troponon-tropomyosin comples aside to expose the cross-bridge binding site

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21
Q

Where is calcium derived from in skeletal muscle contraction?

A

Sarcoplasmic reticulum

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22
Q

What is ATP needed for in skeletal muscle contraction?

A

Needed during muscle contraction to power cross bridges

Needed during relaxation to release cross bridges and to pump calcium back into the sarcoplasmic reticulum

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23
Q

What two factors determine the gradation of skeletal muscle tension?

A

Number of muscles fibres contracting within the muscle

Tension developed by each contracting muscle fibre

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24
Q

What is motor unit recruitment?

A

A stronger contraction can be achieved by stimulation of more motor units

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25
Q

When is asynchronous motor unit recruitment help utilised?

A

Sub-maximal contractions to help prevent muscle fatigue

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26
Q

What does tension in contracting muscle fibres determined by?

A

Frequency of stimulation and summation of contractions
Length of muscle fibre
Thickness of muscle fibre

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27
Q

How can tetanus be achieved in skeletal muscle?

A

If a skeletal muscle is stimulated rapidly, it does not have time to relax and therefore a maximal sustained contraction occurs

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28
Q

What does muscle fibre length have to do with achieving maximal tetanic contraction?

A

When the muscle is at optimal length, the cross bridges on myosin filaments overlap with the cross binding sites on actin filaments

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29
Q

When is skeletal muscle at its optimal length?

A

At rest

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30
Q

What is isotonic contraction in skeletal muscle?

A

Used for body movements and moving objects

This is when muscle tension remains constant as the muscle length changes

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31
Q

What is isometric contraction?

A

Used for supporting objects in a fixed position and maintaining body posture
This is when muscle tension develops at a constant muscle length

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32
Q

What are the differentiating factors between different types of skeletal muscle?

A

Enzymatic pathways for ATP synthesis
Resistance to fatigue - muscle fibres with greater capacity to synthesize ATP are more resistant to fatigue
The activity of myosin ATPase

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33
Q

Will motor units have muscle fibres of the same type?

A

Yes

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34
Q

Why does muscle contraction require ATP?

A

During muscle contraction, ATP is split by myosin ATPase to power cross-bridging stroking
During relaxation, ATP is needed to pump Ca2+ back into the SR’s lateral sacs

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35
Q

How can ATP be acquired in skeletal muscle?

A

Transfer of high-energy phosphate from creatine phosphate to ADP
Oxidative phosphorylation (muscle glycogen stores of glucose and fatty acids in blood)
Anaerobic glycolysis

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36
Q

What are the different types of skeletal muscle fibres?

A

Slow-oxidative (type 1)
Fast-oxidative (type 2a)
Fast-glycolytic (Type 2x)

37
Q

When are slow oxidative type 1 muscle fibres used?

A

Slow twitch fibres

Used for prolonged, low work aerobic activities e.g. maintenance of posture and walking

38
Q

When are fast oxidative type 2a fibres used?

A

Used in aerobic and anaerobic metabolism

Useful in prolonged, moderate work activities such as jogging

39
Q

When are fast glycolytic type 2x fibres used?

A

Anaerobic metabolism

Useful in short-term high intensity activities such as jumping

40
Q

What is a reflex?

A

A stereotyped response to a specific stimulus

41
Q

What is a stretch reflex?

A

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

42
Q

What is the sensory receptor in muscle fibres?

A

Muscle spindle that is activated via muscle stretch

43
Q

What will stretching of the muscle spindles cause?

A

Afferent neurones

44
Q

Where do afferent neurones synapse?

A

In the spinal cord with alpha motor neurones (efferent limb of the stretch reflex) which innervate the stretch muscle

45
Q

What is the other name for muscle spindles?

A

Intrafusal fibres

46
Q

What is the other name for ordinary muscle fibres?

A

Extrafusal fibres

47
Q

What are the sensory nerve endings in muscle spindles called?

A

Annulospiral fibres

48
Q

What is the efferent neurone that supplies muscle spindles?

A

Gamma motor neurone

49
Q

What are some symptoms of muscle disease?

A

Muscle weakness
Myotonia
Myalgia
Muscle stiffness

50
Q

What are some useful investigations in regards to neuromuscular disease?

A 
Electromyography
Nerve conduction studies
Muscle enzymes (CK)
Inflammatory markers (CRP, PV)
Muscle biopsy
51
Q

What are some genetic causes of intrinsic muscle disease?

A

Congenital myopathies
Chronic degeneration (muscular dystrophy)
Myotonia

52
Q

What are some acquired myopathies?

A

Inflammatory (polymyositis)
Non-inflammatory (fibromyalgia)
Endocrine myopathies (cushings, thyorid)
Toxic myopathies (alcohol, statins)

53
Q

What are the different types of joints?

A

Synovial
Fibrous
Cartilaginous

54
Q

What is a fibrous joint?

A

Connects bones by fibrous tissue

Doesn’t allow movement

55
Q

What is an example of a fibrous joint?

A

Joint in the skull sutures

56
Q

What is a catillaginous joint?

A

Bones united by cartilage

Allows limited movement

57
Q

What are some examples of cartilaginous joints?

A

Intervertebral discs
Pubic symphsis
Part of the sacroiliac joints
Costochondral joints

58
Q

What is a synovial joint?

A

Bones separated by a cavity and united by a fibrous capsule (and other extra-articular structures e.g. ligaments, tendons and burase)

59
Q

What is contained within the synovial membrane?

A

Vascular connective tissue with capillary networks and lymphatics
Contains fibroblasts which produce synovial fluid

60
Q

What is the physiological function of joints?

A

Structural support

Purposeful motion

61
Q

What are the roles of joints during purposeful movement?

A

Stress distribution
Confer stability
Joint lubrication

62
Q

How do joints confer stability?

A

Shape of the articular component
Ligaments provide a second major stabilising influence
Synvovial fluid acts as an adhesive seal that freely permits sliding motion between cartilaginous surfaces

63
Q

How do joints provide lubrication?

A

Cartilage interstitial fluid
Synovium derived hyaluronic acid
Synovium dervied lubricin

64
Q

What are the functions of synovial fluid?

A

Lubricates joint
Facilitates joint movement
Helps minimise wear-and tear
Aids in nutrition of articular cartilage
Supplies chondrocytes with oxygen and nutrients

65
Q

What causes synovial fluid to have a high viscosity?

A

Presence of hyaluronic acid produced by synovial cells

66
Q

How does the viscosity and elasticity of synovial fluid change during joint movement?

A

Rapid movement = decreased viscosity and increased elasticity

67
Q

What will happen to synovial fluid in osetoarthritis?

A

The elasticity and viscosity of the fluid will not change

68
Q

What is the WBC count in synovial fluid?

A

<200 WBC/mm of which polymorphs are usually <25/mm

69
Q

When will the synovial fluid WBC count increase?

A

In inflammatory and septic arthritis

70
Q

What will cause synovial fluid to turn red?

A

A traumatic synovial tap

Haemorrhagic arthritis

71
Q

What are the characteristics of normal synovial fluid?

A 
High viscosity
Colourless
Transparent clarity
<200 WCC
<25 polymorphs
72
Q

What are the charcteristics of inflammatory synovial fluid?

A 
Low viscosity 
Straw/yellow colour
Translucent clarity
2000-75,000 WCC
>50 polymorphs
73
Q

What are the characteristics of septic synovial fluid?

A 
Variable viscosity
Variable colour
Opaque clarity
>100,000 WCC
>75 polymorphs
74
Q

What are the different zones to an articular cartilage?

A

Superficial zone
Middle zone
Deep zone
Calcified zone

75
Q

What type of cartilage makes up the articular cartilage?

A

Hyaline cartilage

76
Q

What makes up the ACM in articular cartilage?

A

70% water
20% type 2 collagen
GAGs 10%

77
Q

What is the function of water in hyaline cartilage?

A

Content decreases with age

Maintains the resilience of the tissue and contributes to the nutrition and lubrication system

78
Q

What is the function of collagen in hyaline cartilage?

A

Mainly type 2 which decreases with age
Maintains the cartilage architecture
Provides tensile stiffness and strength

79
Q

What is the function of proteoglycan in hyaline cartilage?

A

Highest conc in middle and deep zones
Composed of GAGs
Responsible for the compressive properties associated with load bearing

80
Q

What synthesises, degrades and organises the ECM of articular cartilage?

A

Chondrocytes

81
Q

How do chonrocytes degrate the ECM?

A

Metalloproteinase proteolytic enzymes - collagnase and stomelysin

82
Q

What effect do catabolic factors have on cartilage matrix turnover?

A

Stimulate proteolytic enymes and inhibit proteoglycan synthesis: Produce TNF-alpha and IL-1

83
Q

What effect do anabolic factors have on cartilage matrix turnover?

A

Stimulate proteolgycan synthesis and conteract effects of IL-1
Produde tumour growth factor and insulin-like growth factor

84
Q

What are markers of cartilage degredation?

A

Serum and synovial keratin sulphate (increased levels = cartilgae breakdown)
Type 2 collagen in synovial fluid (increased levels indicate cartilage breakdown)

85
Q

What condition is described as synovial cell proliferation and inflammation?

A

RA

86
Q

What condition is described as deposition of salt crystals in a joint?

A

Gouty arthritis

87
Q

What condition is described as injury and inflammation to periarticular structures?

A

Tendonitis

88
Q

What is the difference between gout and pseudogout?

A

Needle shaped uric acid crystals - gout

Thomboid shaped calcium pyrophosphate crystals - pseudo-gout

MSK (34 decks)

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