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UofG Medicine Question Bank 2020 > Muscle > Flashcards

Muscle Flashcards

1
Q

What is muscle fatigue?

A

Inability to maintain power output, however this is reversible

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2
Q

How does fatigue impact force, shortening velocity, and relaxation rate?

A

All decline

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3
Q

How does rapid onset fatigue impact recovery in comparison to slow onset fatigue?

A

Rapid recovery for rapid onset

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4
Q

What can cause peripheral fatigue?

A

Downstream of neuromuscular fatigue

  1. Failure of excitation coupling -> T-Tubules fail formation of action potential due to excess potassium-> sarcoplasmic reticulum activation is weaker, less Ca
  2. Hydrogen (produced following contraction) can compete with Ca for binding to troponin, resulting in slowed Ca activation, and slowed contraction due to less cross bridging
  3. More ions being present (H, ADP, and Pi) can slow the reuptake of Ca by the sarcoplasmic reticulum, reducing recovery time following contraction, and preventing the stimulation of a second contraction
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5
Q

What is central fatigue?

A

Within the central nervous system upstream of neuromuscular junction.
Cortex isn’t capable of creating drive to turn muscles ‘on’

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6
Q

How would you differentiate between central and peripheral fatigue?

A

Stimulate the muscle directly, if there is a reduction in force, then fatigue is peripheral, if the muscle responds appropriately, fatigue is central

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7
Q

What restricts exercise before entering into cardio and respiratory problems? Touch on nerves present in muscles.

A

Fine afferent nerves contain 2 different sensory fibres; ergoreceptors (how hard muscle is working) and mechanoreceptors (local stretch and tearing).
As you use muscle, receptors project centrally to allow cardio and resp areas to respond appropriately.
They also project to cortex to reduce cortico-excitability which keeps the central motor drive in line with the peripheral capacity to deliver forces.
Cortex tires as the muscle tires.

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8
Q

How do muscle twitches change during voluntary contraction and relaxation?

A

They are the same size during relaxation. During relaxation following voluntary contraction, we can see twitch amplitude is reduced.
During contraction, twitching is not noticeable

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9
Q

Why does short, high intensity muscle contraction cause a reduction in force?

A

High action potential firing rate, lots of potassium release with lack of blood flow due to contraction results in more potassium in T tubules, it causes sustained depolarization of T tubules and inability to respond to innervation.
Peripheral fatigue results as well as a weakened force
Recover is rapid (due to sodium-potassium pumps and diffusion)

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10
Q

Can muscle fatigue be a failure of ATP reduction?

A

Nope, intracellular ATP levels are almost always constant.

Muscle goes into rigor if it runs out of ATP, not fatigue.

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11
Q

During muscle fatigue, are there any changes in muscle ion levels?

A

ADP, Pi, and H+ all increase.

This can impair calcium fluxes and force delivery at cross bridges

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12
Q

How do ion levels (H, Pi, and ADP) within skeletal muscle impact muscle contraction?

A

They all inhibit Ca release and reuptake into the sarcoplasmic reticulum.
This impacts force, speed of shortening, and relaxation.
H competes with Ca for troponin

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13
Q

During short duration, high power events, how is energy supplied?

A

ATP is regenerated by breakdown of creatine phosphate

Both makes ATP and removes ADP.

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14
Q

How is energy supplied during long duration exercise?

A

Lipid metabolism begins after 90% of initial glycogen has been used.
Lipid metabolism slows re-phosphorylation of ADP in Krebs cycle

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15
Q

What types of motor units does long duration exercise use? Include type of respiration and fuel source.

A 
Type 1 (slow fatigue resistant units)
Aerobic, carb and lipid metabolism
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16
Q

What types of motor units does moderate duration exercise use? Include type of respiration and fuel source.

A

Type 1 and 2 (slow and fast fatigue resistant units)

Aerobic, fuel mix uses more carbs

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17
Q

What types of motor units does short duration exercise use? Include type of respiration and fuel source.

A

All units active
Aerobic/anaerobic
carb dependent. Inefficient at glycolytic metabolism

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18
Q

What type of muscle growth does strength training cause?

A

Hypertrophy of 2X and 2A muscle fibres

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19
Q

What type of muscle growth does endurance training cause?

A

No demands for more strength
Hypertrophy of type 1 fibres, 2x declines, 2A response is variable
Reduction in body weight

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20
Q

What muscle fibres are good at lipid metabolism?

A

Type 1

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21
Q

What are the phases of muscle strength gain?

A

Neural gains are rapid and come first (first 4-6 weeks)
Hypertrophy of muscle begins at about 12-15 weeks.
Connective tissue therefore has time to strengthen

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22
Q

What changes does enhances in endurance have?

A

Turns up aerobic metabolism
Better regional perfusion, improved CV performance, O2 delivery, cardiac output , regional flow, higher capillary density, blood volume, etc.
Hypertrophy in type 1 fibres.

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23
Q

What is the process of hypertrophy in muscle?

A

First, new contractile filaments added laterally to existing myofibrils
Then fibril splitting (bigger fibrils split longitudinally causing hypertrophy of the fibre, not hyperplasia)

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24
Q

How can a person initiate more force during muscle contraction?

A
  1. More complete activation of muscle
  2. More activation of agonist muscles
  3. More effective in inactivating antagonist muscles
25
Q

What structures form a muscle cell?

A

Have multiple myoblasts fusing to form a muscle cells, which is surrounded by perimysium.

26
Q

What is a motor unit?

A

Single motor neuron, and all its muscle fibres it innervates
Functional units of muscle control
Muscle may contain many motor units (especially large ones)
Motor units can hold 1000s of muscle fibers

27
Q

How does motor unit numbers relates to function?

A

Fine, specific function will mean higher numbers of motor units to increase motor control of that muscle

28
Q

When classifying motor units, what classification properties are linked with tonic muscle?

A

Aerobic
Slow contracting
Red in colour,
Oxidative muscle

29
Q

When classifying motor units, what classification properties are linked with phasic muscle?

A

Pale
More glycolytic
Faster contracting
faster fatiguing

30
Q

What are the 3 main types of motor units?

A 
Slow fatiguing (1, S)
Fast fatigue resistant (2A, FFR)
Fast Fatiguing (2B, 2X, FF)
31
Q

What determines the type of muscle fiber a muscle cell will become?

A

Genetics contributes to amounts of muscle (ie. less myostatin activity will lead to more muscle)
Pattern of muscle use (basic muscle type is fast fatiguing due to atrophy experiments)

32
Q

Does type of training impact the type of muscle fiber that will devlope?

A

No, it changes the type of muscle fiber that is hypertrophy-ing

33
Q

What early and late changes are seen with strength training?

A

Early: better motor unit activation, less antagonistic activation, improved glycolytic metabolism,
6 weeks: FF fiber hypertrophy

34
Q

What muscle fiber changes are seen with endurance training?

A

Enhanced oxidative metabolic profile, increased mitochondria, improved oxygen supply, more myoglobin, S and FFR fiber hypertrophy

35
Q

How do elite athletes (sprinter vs marathoner) influence the percentage of type 1 vs type 2 muscle fibers found in the skeletal muscle?

A

Minorly increase the ideal fiber type for their particular activity.
Marathon may have 55-65% type 1 (as opposed to normal 55%)
Sprinter may have 60-75% type 2 (as opposed to normal 45%)

36
Q

How does slowed calcium release during muscle fatigue directly impact muscle contraction?

A

Less effective calcium release will slow the contraction

Calcium needs to bind troponin to initiate cross bridging and shortening of sarcomere

37
Q

How does slow calcium recovery during muscle fatigue impact muscle contraction?

A

Less effective calcium recovery will slow recovery of muscle

38
Q

How does slowed/reduced T tubule activation during muscle fatigue occur, and how does it impact muscle contraction?

A

More potassium in T tubules causes sustained depolarization of T tubules and inability to respond to innervation.
Slows muscle contraction

39
Q

How do myelinated and unmyelinated peripheral nerves differ in terms of function?

A

Unmyelinated- pain, thermal sensitivity

myelinated- Touch, vibration, motor

40
Q

When dividing a peripheral nerve via cross-section, what can you see?

A

Epineurium surrounding nerve
Fasciculi of nerve which are surrounded by perineurium. Fascicles/perineurium sit within the epineurium.
Within fasciculi contain different axons of nerves which may be myelinated.
Blood vessels are found within perineurium and epineurium.

41
Q

How can you evaluate extent of spinal innjury?

A

Voluntary, sensory, reflex responses

Use ASIA scale

42
Q

What is the ASIA Scale?

A

A scale which helps assess degree of spinal cord injury by evaluating sensory/motor abilities.

43
Q

Does a reflex pathway contain an upper motor neuron?

A

No.

44
Q

What helps to keep the tendons and vessels in place during flexion and extension of the wrist?

A

Extensor (dorsal carpal/posterior annular ligament) Retinaculum - Dorsal surface of hand
Flexor (anterior annular/transverse carpal ligament) Retinaculum - Over anterior carpels

45
Q

What forms the roof and floor of the carpal tunnel?

A

Roof- flexor retinaculum (attaches to hamate/pisiform, and scaphoid/trapezium)
Floor- Concave arch of carpal bones which are covered by extrinsic palmar ligaments

46
Q

How many flexor tendons of the hand are there?

A

9
1 for flexor pollicis longus
4 for flexor digitorum superficialis
4 for flexor digitorum profundus

47
Q

What structures pass through the carpal tunnel?

A

Median nerve
Flexor tendons
Vascular Synovium

48
Q

What is non-prehensile movements of the hand?

A

Pushing and hitting

49
Q

What is prehensile movements of the hand?

A

Grasp and grip

fundamental movement of the hand and thumb

50
Q

What differentiates intrinsic and extrinsic muscles of the hand?

A

Intrinsic- belly sits inside of palm and more tuned for fine movement
Extrinsic- belly of muscle sits outside of palm and is used in more crude movement

51
Q

What are the flexor extrinsic muscles of the hand?

A 
Superficial: 
Flexor digitorum superficialis
Palmaris Longus 
Deep:
Flexor digitorum profundus
flexor pollices longus
52
Q

What are the extensor extrinsic muscles of the hand?

A 
Superficial:
Extensor digitorum communis (radial nerve)
extensor digiti minimi (radial nerve)
Deep:
Extensor indicis (radial nerve)
53
Q

What are the extrinsic muscles of the thumb?

A

Extensor pollicis longus
Extensor pollicis brevis
Flexor pollicis longus (anterior)
Abductor pollicis longus

54
Q

What are the thenar eminence intrinsic muscles of the fingers and the innervation?

A

Abductor pollices brevis
Flexor pollices brevis,
Opponens pollices
(all median innervation)

55
Q

What are the hypothenar eminence intrinsic muscles of the fingers and the innervation?

A

Abductor digiti minimi,
Flexor digiti mini,
Opponens digiti minimi
(all ulnar)

56
Q

What are actions of the Lumbrical intrinsic muscles of the fingers, how many are there, and the innervation?

A

4 deep muscles,
flex a metacarpal phalangeal joints and extending the IP joint
(median/ulnar nerve)

57
Q

What are actions of the interossi intrinsic muscles of the fingers, how many are there, origin, and the innervation?

A

4 dorsal:
Origin between metacarpal bones, aid in abduction of digits 2,3,3,4, ulnar nerve
3 palmer:
Metacarpals origin to phalanx 2,4,5 insertion
Adduct fingers, ulnar nerve

58
Q

Why doesn’t the 5th digit have a dorsal interossi intrinsic muscle?

A

It has abductor digiti minimi to perform abduction

59
Q

What is the snuff box and what forms the borders of it?

A

Triangular deepening on dorsal, radial hand
Floor- scaphoid and trapezium
Medial Border- Extensor pollicis longus
Lateral Border- Extensor pollicis brevis and abductor pollicis longus
Proximally- Radial styloid process
Distally- 1st carpometacarpal joint

UofG Medicine Question Bank 2020 (42 decks)

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