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BMSC 207 > BMSC 207 Muscle 2 > Flashcards

BMSC 207 Muscle 2 Flashcards

1
Q

Muscle Fatigue

A

A decrease in muscle tension as a result of previous contractile activity that is reversible with rest.

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2
Q

2 types of Muscle Fatigue

A

Central Fatigue: Feeling of tiredness and a desire to cease Activity. Precedes Physiological Cell fatigue

Peripheral Fatigue: At the Neuromuscular Junction: Proposed ACh synthesis can’t keep up with neuron firing rate

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3
Q

Most Experimental evidence points to problems with excitation-contraction coupling:

A

At the T-Tubules
With repeated AP firing, K+ builds up in the T-tubules (extracellular space) changing the threshold for the APs in muscle fibres

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4
Q

Peripheral Fatigue (Within the Muscle Fibre: Accumulation theories)

A

Build up of Inorganic Phosphate, ADP, H+
Substances can act directly or indirectly to cause fatigue

Sarcoplasmic Reticulum - Reduced Ca2+ reuptake and release

Troponin C - Decreased Ca2+ sensitivity leading to decreased cross-bridge cycling

Myosin Head - Release of Pi and ADP during cross bridge cycle slowed by Sarcoplasmic accumulation

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5
Q

Slow Fibres

A

Contain myosin with slower ATPase activity (TYPE I)

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6
Q

Fast Fibres

A

Contain myosin with more rapid ATPase activity (Type II)

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7
Q

Oxidative Fibres

A

Fibres containing a large amount of mitochondria, Have a high capacity for aerobic metabolism.

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8
Q

Glycolytic Fibres

A

Fibres containing few mitochondria but an abundance of glycolytic enzymes and a large store of glycogen.

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9
Q

Slow-Oxidative Fiber (Type I)

A

Slow
Dark Red
Lots of Mitochondria
Dark cause of lots of Myoglobin
Aerobic
Long Contraction Duration
used for posture.

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10
Q

Fast Oxidative Glycolytic Fiber (Type IIA)

A

Intermediate
Red
Intermediate (Diverse)
Medium diameter
Contraction duration short
Fatigue resistant
Used for standing

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11
Q

Fast-Glycolytic Fiber (Type IIX)

A

Fast Speed
Light color (Pale)
Easily fatigued
Large Diameter
Few Mitochondria
Used for sprints, jumping.

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12
Q

Determinants of Muscle Force/Tension (Muscle Cell)

A
  • Fibre Diameter
  • Fatigability
  • Initial resting length
  • Frequency of activation
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13
Q

Determinants of muscle force/tension (Entire Muscle)

A
  • Number of Muscle cells activated
  • Number of motor units
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14
Q

How does Muscle length influence tension development?

A

By the degree of overlap between Actin and Myosin Filaments

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15
Q

Single Twitches

A

Muscle relaxes completely between stimuli
A single twitch DOES NOT represent the maximal force that a muscle fibre can develop.

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16
Q

Summation

A

Stimuli closer together do not allow muscle to relax fully.

Action potential occurs before the muscle fibre is allowed to relax.

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17
Q

Tetanus

A

A Maintained contractile response to repeated stimuli

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18
Q

Unfused Tetanus

A

Reaches steady state of contraction but stimuli are far enough apart that the muscle fibre slightly relaxes between stimuli

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19
Q

Fused Tetanus

A

The stimulation rate is fast enough that the fibre does not relax, instead it reaches maximum tension and remains there.

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20
Q

One way to increase tension developed by a single muscle fiber is to?

A

Increase the rate at which Action Potential occur in the fibre

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21
Q

Motor Neuron Pool

A

The group of all motor neurons innervating a single muscle.

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22
Q

What amount of input from upper motor neuron makes what size lower motor neuron reach threshold?

A

Small amount of input from upper motor neuron makes small diameter motor neuron reach threshold and fire AP

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23
Q

Can a small amount of input from upper motor neuron make a Large diameter motor neuron reach threshold

A

No

24
Q

Small Motor Neurons

A

Innervate the least number of (small diameter) muscle fibers (slow-oxidative) constituting small motor neurons

25
Q

Intermediate Motor Neurons

A

Tend to innervate an intermediate number of (medium diameter) muscle fibres (Fast-oxidative glycolytic) establishing intermediate sized motor units.

26
Q

Large Motor Neurons

A

Tend to innervate a large number of (large Diameter) muscle fibers (fast-glycolytic) making up large motor units.

27
Q

Asynchronous Recruitment

A

during submaximal contraction the CNS modulates firing rates of upper motor neurons to allow different motor units to maintain contraction in order to prevent fatigue

28
Q

Muscle Tension

A

The force tending to pull the attachment points of a muscle toward one another

29
Q

Isotonic Contraction

A

Muscle contracts, shortens and creates enough force to move the load.
- Creates force to generate movement

30
Q

Isometric contraction

A

The muscle contracts but does not shorten. The force cannot move the load
- Create force without moving a load.

31
Q

Concentric Contraction

A

Muscle shortens while generating force
(Bicep Curl)

32
Q

Eccentric contraction

A

Muscle lengthens while generating force
-Acts to decelerate the joint at the end

33
Q

Increasing Muscle Mass

A

Protein Synthesis > Protein Degradation.

34
Q

2 mechanisms by which muscle mass may be increased:

A

Hypertrophy: Increase in muscle diameter
Hyperplasia: Increase in number of muscle fibers

35
Q

Do humans go through Hyperplasia or hypertrophy?

A

Hypertrophy

36
Q

Myosatellite cells

A

In response to injury it is Involved in muscle repair may form new muscle fibers.

37
Q

Muscle Hypertrophy

A

Increase in size of sarcomeres and number of contractile proteins
Increased number of sarcomeres within a muscle length
Increased sarcoplasmic storage (glycogen)

38
Q

Studies show a greater rate of what type of muscle fibers?

A

Type II
Hypertrophy is Genetically predetermined.

39
Q

Skeletal Muscle Atrophy (When would it occur?)

A

Protein Degradation > Protein synthesis
Occurs due to:
- Immobilization
- Bed Rest
- Unloading

40
Q

Muscle Atrophy Disease

A

Cachexia - Weakness and/or wasting due to chronic disease

41
Q

Skeletal Muscle Reflexes

A
  • Involved in all movements
  • Receptors sense changes in joint movements, muscle tension and muscle length feed info into CNS and responds in 1 of 2 ways.
42
Q

2 ways CNS responds to muscle tension and muscle length

A
  • Muscle contraction is needed the CNS activates motor neurons to muscle fibres
  • If relaxation is needed sensory inputs activates inhibitory interneurons in CNS which inhibit activity in motor neuron.
43
Q

Monosynaptic Reflex

A

Has a single synapse between the afferent and efferent neurons.

44
Q

Polysynaptic Reflexes

A

Has two or more synapses. This somatic motor reflex has both synapses in the CNS

45
Q

Proprioceptors

A

Provide information into the CNS about the position of our limbs in space, movement, and the effort exerted by skeletal muscles

46
Q

Joint Receptors

A

These are found in the capsules and ligaments around the joints and are stimulated by mechanical distortion that accompany changes in the position of bones.

47
Q

Muscle Spindles

A

Small elongated stretch receptors scattered among and arranged parallel to skeletal muscle fibers.
- Sends information to the CNS about muscle length and changes in muscle length

48
Q

Muscle spindles made up of

A

Sensory neuron wrapped around intrafusal muscle fibers.
Extrafusal muscle fibers are regular muscle fibers innervated by alpha motor neurons

49
Q

Maintain resting muscle tone

A
  1. Extrafusal Muscle fibers at resting length.
  2. Sensory neuron is tonically active
  3. Spinal cord integrates function
  4. Alpha motor neurons to extrafusal fibres receive tonic input from muscle spindles
  5. Extrafusal fibers maintain a certain level of tension even at rest.
50
Q

Muscle Spindle Reflex - 3 stages

A

Addition of a load stretches the muscle and the spindles, creating a reflex contractions
a) Load added to muscle
b) Muscle and Muscle spindle stretch as arm extends
c) reflex contraction initiated by muscle spindle restores arm positions

51
Q

Muscle spindles Without gamma motor neurons

A

Muscle contraction cause the spindle firing rate to decrease
a) Alpha motor neuron fires.
b) Muscle contracts
c) Less stretch on center of intrafusal fibers.
d) Firing rate of spindle neuron decreases

52
Q

Alpha-gamma coactivation

A

Maintains spindle function when muscle contracts.

53
Q

Stages of Alpha-gamma Coactivation (3)

A
  1. Alpha motor neuron fires and gamma motor neuron fires.
  2. Muscle and intrafusal fibers both contract
  3. Stretch on centers of intrafusal fibers unchanged, Firing rate of afferent neuron remains constant
54
Q

Golgi tendon organ

A
  • Respond to muscle tension
    -Protects the muscle from excessively heavy loads by causing the muscle to relax and drop the load.
55
Q

Flexion reflexes

A

Pulls limbs away from painful stimuli

56
Q

Crossed Extensor Reflex

A

A flexion reflex in one limb causes extension in the opposite limb. The coordination of reflexes with postural adjustments is essential for maintaining balance

57
Q

Crossed extensor reflex

A
  1. Painful stimulus activates nociceptors
  2. Primary sensory neuron enters spinal cord and diverges
  3. One collateral activates ascending pathways for sensation (pain) and postural adjustment.
  4. Withdrawal reflex pulls foot away from painful stimulus

BMSC 207 (5 decks)

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