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BSMS 204- Theme 3 > Lecture 1- physiology of skeletal muscle contraction > Flashcards

Lecture 1- physiology of skeletal muscle contraction Flashcards

1
Q

How many Ca2+ bind to troponin C (TnC)?

A

4

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2
Q

what does tropinin C mean?

A

C=calcium binding

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3
Q

How many TnC bind in the heart muscle?

A

3

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4
Q

What is the result of Ca binding to troponin?

A

TnC changes confirmation

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5
Q

What does the conformational change in TnC to TnI and what is the result of this?

A

shut off TnI
tropomysin-troponin leaves F actin groove and unmasks the myosin binding site on actin
Next myosin head make cross bridges to actin- this breaks down ATP and pulls thin filaments

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6
Q

what is total TnI marker of and what is the cardiac TnI marker of?

A

total TnI- marker for total muscle breakdown

Cardiac TnI- marker for myocardial infarct

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7
Q

what causes the increase in force generation?

A

Increased overlap with thin and thick filaments

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8
Q

Explain the process of rigor mortis?

A

ATP depleted after death
muscles do not resequester Ca2+ in SR >INCREASING cytosolic Ca2+
Ca2+ allows crossbridge cycle contraction until ATP&creatine-P run out
No ATP=myosin stops just after the power stroke with myosin head still bound to actin

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9
Q

when does rigor mortis end?

A

when muscle tissues degrade- 3 days after death

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10
Q

Where is creatine found?

A

muscle fibres

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11
Q

what is creatine phosphorylated to and what is the function of this?

A

creatine phosphate

energy storage in the muscle

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12
Q

how is the energy stored in the creatine molecule?

A

high energy phosphate bonds

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13
Q

How can creatine phosphate help to restore ATP levels?

A

donates high energy phosphate to ADP restoring it ATP

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14
Q

which enzyme catalyses the ATP buffering and regeneration reaction?

A

creatine phosphokinase (CPK)

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15
Q

what is the CPK marker of in muscles?

A

muscle destruction

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16
Q

what are the two Ca2+ gradients?

A
  1. Extracellular Vs Cytosolic free Ca2+

2. SR vs Cytosolic free Ca2+

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17
Q

what is the general role of Ca2+?

A

triggers contraction

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18
Q

where does the most of the Ca2+ come from?

A

efflux of Ca2+ from the SR to cytoplasm provides most of the Ca2+

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19
Q

what is the effect of depolarisation of Ca2+ conc?

A

INCREASED

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20
Q

What is the function of Ryanodine receptor (RyR)?

A

In SR RELEASES Ca2+ from SR

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21
Q

What is the release from RyR triggered by?

A

voltage sensor on Ca2+ channel

22
Q

what is the role of the SERCA (Smooth endoplasmic Reticulum Calcium ATPase) and what else is required?

A

In SR memmbrane- SERCA pumps back Ca2+ into SR and required ATP

23
Q

what does excitation and contraction coupling mean?

A

the molecular mechanism for how the depolarisation of the plasma membrane leads to the release of Ca2+ into the cytoplasm followed by contraction.

24
Q

define a twitch and how does twitch end?

A

A single AP—–> Ca2+ release from SR—–> twitch

Ca2+ ions are rapidly pumped back into SR- end of twitch

25
Q

Define Tetany?

A

frequent AP—->insufficent Ca2+ resquesteration —->summation of contraction

26
Q

describe the two main types of muscle fibres and explain their properties?

A

SLOQ twitch- (type I- Red- oxidative small daim, has myoglobin and many mitochondria
FAST twitch- Type II- white, non-oxidative and wide diam)
Lower myoglobin and increased energy from glycolysis

27
Q

Explain how else the fibre type differ?

A
  1. aerobic vs anaerobic
  2. faster Ca reuptake (fast)
  3. Max tension produced
  4. fatigue resistance (slow)
28
Q

Explain the scale of muscle fibre types from slow (type I) to Fast (IIB)?

A

Type I -slow- sustained
IIA-
IIX
IIB- Fast- intermittent and precise

29
Q

why does muscles contain mixture of fibre types composition?

A

depends on the action of the muscle

30
Q

what does the proportion of muscle depend on?

A 
physical fitness
Inactive
moderately active
endurance athlete
anaerobic athlete
31
Q

Name three types of motor co-ordination?

A
  1. Motor units- recruitment &size principle
  2. Tetany
  3. Fusion of myocyte into long myofibres
32
Q

Define a motor unit?

A

A single alpha motor neuron and all muscle fibres it innervates

33
Q

explain how these motor units function and their fibre types?

A 
function as a single contractile unit of skeletal muscle 
ALL fibres in the single motor unit are the same type- Slow exidative etc
34
Q

In large muscles, a single motor neurone synapses with how many muscle fibres?

A

1000 fibres

35
Q

In small muscle, a single motor neuron synapses with how many muscle fibres?

A

2-3 muscle fibres

36
Q

what does type and function of the lower motor neuron determine?

A

muscle fibre

37
Q

Define- Isometric and isotonic in terms of force generation?

A

Isometric-generates a variable force while length of the muscle remains unchanged (iso-same metric length)
ISotonic- generates a constant force while the length of muscle changes

38
Q

what are the types of muscular force generation?

A

Concentric

Eccentric

39
Q

Explain the concentric and eccentric force generation with an example?

A

Concentric- force during contraction- tossing a ball into the air
Eccentric- force during muscle elongation- braking a car

40
Q

can both types of force generation occur in the same behaviour?

A

Yes

41
Q

what controls the force generation and what does it depend on?

A

proprioception- controls the force generation based on length and stretch of the muscle

42
Q

explain the difference between lower motor neuron disease Vs upper motor neuron disease?

A

LOWER-
weakness and muscle atrophy

UPPER-
Spasticity and hpertonic

43
Q

What is the function of stretch reflex?

A

controls muscle length

increases muscle force

44
Q

What does lack of patellar reflex mean?

A

Aka- westphal’s sign- may indicate damage to the femoral nerve

45
Q

what type of the muscle fibres are part of the stretch reflex?

A

sensory muscle spindle fibres which detect stretch and length and proprioception

46
Q

describe the location and properties of the spindle fibre?

A

spindle is parrallel to other muscle fibres
ipsilateral spinal reflex
monosynaptic

47
Q

describe the muscle spindle fibre?

A

3-12 intrafusal fibres

spindle- regulates relationship between muscle length and muscle contractility

48
Q

what is the role of gamma motor neurons?

A

increase sensitivity

49
Q

what does the absence of the Westphal’s sign mean?

A

receptor damage
femoral nerve damage
peripheral nerver disease

50
Q

Tendon Reflex function?

A

protects from overloading by decreasing the muscle force—–> dropping the load

51
Q

Explain the properties of tendon reflex?

A 
sensor
Golgi tendon organ
detects tension in series with muscle
in tendon- near the border with muscle
Disynaptic
Ipsilateral spinal reflex

BSMS 204- Theme 3 (5 decks)

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