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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
Define Tetany?
frequent AP---->insufficent Ca2+ resquesteration ---->summation of contraction
26
describe the two main types of muscle fibres and explain their properties?
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
Explain how else the fibre type differ?
1. aerobic vs anaerobic 2. faster Ca reuptake (fast) 3. Max tension produced 4. fatigue resistance (slow)
28
Explain the scale of muscle fibre types from slow (type I) to Fast (IIB)?
Type I -slow- sustained IIA- IIX IIB- Fast- intermittent and precise
29
why does muscles contain mixture of fibre types composition?
depends on the action of the muscle
30
what does the proportion of muscle depend on?
``` physical fitness Inactive moderately active endurance athlete anaerobic athlete ```
31
Name three types of motor co-ordination?
1. Motor units- recruitment &size principle 2. Tetany 3. Fusion of myocyte into long myofibres
32
Define a motor unit?
A single alpha motor neuron and all muscle fibres it innervates
33
explain how these motor units function and their fibre types?
``` function as a single contractile unit of skeletal muscle ALL fibres in the single motor unit are the same type- Slow exidative etc ```
34
In large muscles, a single motor neurone synapses with how many muscle fibres?
1000 fibres
35
In small muscle, a single motor neuron synapses with how many muscle fibres?
2-3 muscle fibres
36
what does type and function of the lower motor neuron determine?
muscle fibre
37
Define- Isometric and isotonic in terms of force generation?
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
what are the types of muscular force generation?
Concentric | Eccentric
39
Explain the concentric and eccentric force generation with an example?
Concentric- force during contraction- tossing a ball into the air Eccentric- force during muscle elongation- braking a car
40
can both types of force generation occur in the same behaviour?
Yes
41
what controls the force generation and what does it depend on?
proprioception- controls the force generation based on length and stretch of the muscle
42
explain the difference between lower motor neuron disease Vs upper motor neuron disease?
LOWER- weakness and muscle atrophy UPPER- Spasticity and hpertonic
43
What is the function of stretch reflex?
controls muscle length | increases muscle force
44
What does lack of patellar reflex mean?
Aka- westphal's sign- may indicate damage to the femoral nerve
45
what type of the muscle fibres are part of the stretch reflex?
sensory muscle spindle fibres which detect stretch and length and proprioception
46
describe the location and properties of the spindle fibre?
spindle is parrallel to other muscle fibres ipsilateral spinal reflex monosynaptic
47
describe the muscle spindle fibre?
3-12 intrafusal fibres | spindle- regulates relationship between muscle length and muscle contractility
48
what is the role of gamma motor neurons?
increase sensitivity
49
what does the absence of the Westphal's sign mean?
receptor damage femoral nerve damage peripheral nerver disease
50
Tendon Reflex function?
protects from overloading by decreasing the muscle force-----> dropping the load
51
Explain the properties of tendon reflex?
``` 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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