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SFI Test 2 > Skeletal Muscle Physio II > Flashcards

Skeletal Muscle Physio II Flashcards

1
Q

What is an Isotonic contraction?

A

Muscle changes length, keeping a constant tension

Can be concentric or eccentric

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2
Q

What is a concentric contraction?

A

Muscle decreases length against opposing load, i.e. lifting weight up

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3
Q

What is an eccentric contraction?

A

Muscle increases in length as it resists load, i.e. pushing something down

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4
Q

What is an isometric contraction?

A

Muscle does not shorten and tension builds up

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5
Q

What is the amount of active tension generated dependent on and why?

A

Muscle length

Depends on the number of crossbridges that are able to form

Too long - too little cross bridges

Too short - actin filaments push on each other, distorting the filaments and weakening cross bridges

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6
Q

What is the optimal length?

A

The length of muscle where maximum force is generated

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7
Q

What is passive tension?

A

Tension generated by the structure of the muscle fiber itself, caused by resistance of muscle’s elasticity to stretch

Also called preload

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8
Q

What is total tension?

A

Sum of active and passive tension

Generated when muscle is stimulated to contract at different preloads

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9
Q

What is active tension?

A

Generated by the contractile process

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10
Q

What is the force-velocity relationship?

A

As you increase the load, the velocity decreases

Velocity is determined by the active tension generated

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11
Q

What are type I fibers?

A

Slow-twitch, slow myosin ATPase

Loaded with mitochondria - use ox phos

Rich in myoglobin

Resistant to fatigue

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12
Q

What are type IIa fibers?

A

Fast-twitch, fast myosin ATPase

Loaded with mitochondria

Use ox phos and glycolysis

Rich in myoglobin

moderately fatigue-resistant

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13
Q

What are type IIb fibers?

A

Fast-twitch, fast myosin ATPase

Rich in glycogen

Depend on glycolysis

Fatigue easily

Low in myoglobin

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14
Q

What is a motor unit?

A

Group of muscle fibers innervated by the same motor neuron

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15
Q

What is the innervation ratio?

A

Number of fibers innervated by a motor unit

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16
Q

What is a Type I motor unit?

A

Innervate Type I muscle fibers

Few muscle fibers innervate - small IR

Slower-conducting

Fine, graded movements

17
Q

What is a Type II motor unit?

A

Innervate Type II muscle fibers

More muscle fibers innervate - large innervation ratie

Faster-conducting

Coarse movments

18
Q

What are two ways that the tension of the entire muscle can be increased via motor units?

A

Recruitment- increasing number of motor units (Slow
–> fast)

Summation - increasing frequency of individual motor unit firing

19
Q

What is fatigue?

A

Decline in the ability of muscle to generate force

Glycogen and creatine phosphate stores depleted

ATP levels do not decrease substantially

20
Q

What factors could cause fatigue?

A

Decreased motor neuron firing

Decreased oxygen

Impaired Ca release from sarcoplasmic reticulum

21
Q

What happens to motor units in aging?

A

Decrease in total number

Increase in number of fibers/motor unit

22
Q

What occurs to muscles with aging?

A

Atrophy - decrease in muscle mass

Decrease in max force and power of contraction

Decrease in total number of fibers

Decrease in number of mitochondria

23
Q

What is sarcopenia?

A

Decrease in muscle mass and strength

Fewer satellite cells

24
Q

Describe muscular dystrophy.

A

Progressive skeletal muscle weakness, defects in muscle proteins, and death of muscle cells and tissue

Major forms are Duchenne and Becker’s

Both involve defects in dystrophin

25
Q

How does a defect in dystrophin cause muscular dystrophy?

A

Lead to instability of the sarcolemma which leads to damage of muscle during contractions

26
Q

Describe myopathy

A

Primary symptoms muscle weakness, but cramps, stiffness, and spasms can occur

Causes: congenital, genetic abnormalities in mitochondria, mutations in glucose metabolizing genes

Prognosis varies

27
Q

What is Cachexia?

A

“Wasting Syndrome”

Loss of weight, muscle atrophy, fatigue, weakness and loss of appetite

Seen in patients with chronic diseases

Similar to sarcopenia

28
Q

What is myostits?

A

Inflammation of the muscles

Results in muscle weakness and pain, particularly in trunk

Caused by injury, infection or autoimmune disease

29
Q

What is Rhabdomyolysis?

A

Breakdown of muscle fibers resulting in the release of muscle fiber contents, particularly myoglobin, into the circulation

Can cause kidney damage (muscle contents release)

Most common causes are crush injury, overexertion, alcohol abuse, statins, and toxins

30
Q

What is Malignant hyperthermia?

A

Defects in RYR1 channel that causes it to channel to open more easily and close more slowly

Activated by certain anesthetics and muscle relaxers

Leads to uncontrolled release of Ca

Muscles contract abnormally, leading to rigidity and heat production

SFI Test 2 (9 decks)

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