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PHPY 302 > Muscular System > Flashcards

Muscular System Flashcards

1
Q

What is the primary function of the muscular system?

A

Transform chemical energy into mechanical energy.

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2
Q

What can mechanical energy produce?

A

Equilibrium, force, work, transport, and heat

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3
Q

Describe skeletal muscle (What is it attached to, used for, how fast is it, voluntary or involuntary)

A

It is attached to the bone by tendon
It is used for locomotion and to maintain balance
It has quick responses
It is controlled voluntarily (excluding reflexes)

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4
Q

Describe cardiac muscle (What is it attached to, used for, how fast is it, voluntary or involuntary)

A

It is attached to blood vessels
It is involved in blood circulation
It has a slower response time than skeletal muscle
It is involuntary

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5
Q

Describe smooth muscle (What is it attached to, used for, how fast is it, voluntary or involuntary)

A

It is attached to the wall of organs and blood vessels
It is involved in blood pressure, digestion, bladder control, and respiration
It requires the slowest response time
It is involuntary

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6
Q

Which muscles are uninucleated and which are multinucleated?

A

Smooth and cardiac are uninucleated

Skeletal is multinucleated

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7
Q

How does a muscle become multinucleated?

A

During embryonic development many myoblasts fuse to form one skeletal muscle fiber

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8
Q

What controls involuntary muscle contraction?

A

The autonomic nervous system and the endocrine system

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9
Q

What controls voluntary muscle contraction?

A

The somatic nervous system

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10
Q

Which kinds of muscle have pacemaking capabilities?

A

Smooth muscle and cardiac muscle

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11
Q

What does excitability mean?

A

The ability to respond to stimuli by producing action potentials

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12
Q

What is the stimulus that leads to action potentials in the three types of muscle?

A

In cardiac and smooth muscle the stimulus is electrical and initiated by pacemaker cells
In skeletal muscle the stimulus is chemical and occurs in the neuromuscular junction where acetylcholine is released as a neurotransmitter

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13
Q

What is contractibility of muscle?

A

The ability of muscular tissue to contract forcefully when stimulated by action potentials

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14
Q

What impacts the force of muscle contraction?

A

The velocity of muscle fiber shortening

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15
Q

What is tension?

A

Muscle contraction without muscle shortening

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16
Q

What is extensibility of muscle?

A

The ability of muscular tissue to stretch within limits without being damaged

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17
Q

What limits the range of muscle extensibility to keep it within functional range?

A

Connective tissues

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18
Q

What is elasticity of muscle?

A

The ability of muscular tissue to return to its original shape after contraction or extension.

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19
Q

What does titin do?

A

Provides elasticity to muscles

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20
Q

What is adaptability of muscle?

A

The ability of muscles to undergo hypertrophy or atrophy in their adult form

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21
Q

Describe slow-twitch oxidative fibers (how fast do they use ATP, how fast do they contract, how do they get ATP, how much endurance do they have)

A

The rate of ATP breakdown is the slowest
Muscle shortening is slow
ATP production is aerobic
High endurance and resistance to fatigue

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22
Q

Describe fast-twitch oxidative fibers (how fast do they use ATP, how fast do they contract, how do they get ATP, how much endurance do they have)

A

The rate of ATP breakdown is faster than slow-twitch
Muscle shortening is faster than slow twitch
ATP production is aerobic
Moderate endurance and resistance to fatigue

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23
Q

What is creatine phosphate?

A

A reservoir for the storage of ATP in fast-twitch oxidative fibers and fast-twitch glycolytic fibers

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24
Q

Describe fast-twitch glycolytic fibers (how fast do they use ATP, how fast do they contract, how do they get ATP, how much endurance do they have)

A

Rate of ATP breakdown is the fastest
Muscle shortening is the fastest
ATP production is anaerobic
Low endurance and resistance to fatigue

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25
Q

What are the four main events in excitation-contraction coupling?

A
  1. Acetylcholine is released from somatic motor neuron
  2. Acetylcholine initiates an action potential in the muscle fiber
  3. Action potential travels along the sarcolemma in the T-tubules and triggers Ca release from the SR
  4. Ca binds with TnC and initiates muscle contraction
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26
Q

What ends muscle contraction?

A

The return of calcium from the cytosol to the SR through sarco-endoplasmic reticulum calcium ATPase (SERCA)

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27
Q

Where do all three types of muscle originate during embryonic development?

A

The somatic mesoderm

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28
Q

What was the coelomic graft model?

A

A section of hindlimb of a chicken was moved to the coelom where there is no neural input to determine if fiber type is determined by cell lineage or if external influences played a role

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29
Q

What are satellite cells?

A

Muscle stem cells which are found inbetween the basal lamina and the plasma membrane. They are normally inactive, but can activate in response to injury or exercise to fuse to muscles and repair them

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30
Q

What was the difference observed between avian/rodent satellite cells and mammalian satellite cells?

A

Avian and rodent satellite cells became muscle cells of the tissue they were isolated from (fast or slow). They are considered heterogeneous.
Mammalian satellite cells
transform into either form (fast and slow) depending on which muscle needs them. They are considered homogeneous.

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31
Q

What role do nerves play in determining if muscles are fast or slow?

A

Whichever nerve type a muscle is attached to it will respond accordingly. A slow muscle that is attached to a fast nerve will become a fast muscle

32
Q

How do the patterns of electrical activity differ in fast and slow muscles?

A

Type one motor units (slow) receive high amounts of impulses in low frequencies
Type two motor units (fast) receive low amounts of impulses in higher frequencies

33
Q

Why can’t we do in vivo experiments of slow to fast muscle transformation regarding electrical activity?

A

We can not minimize enough of the background impulses to give type one (slow) motor units the same conditions as type two (fast)

34
Q

What did the hind limb suspension study discover?

A

Action potential activity is of little importance to preventing muscle atrophy. The force generation of the muscles is what prevents atrophy.

35
Q

How is fiber size regulated?

A

Regulating the number of nuclei, the rate of protein synthesis, and the rate of protein degredation

36
Q

What is myostatin?

A

A member of the trans-transforming growth factor B superfamily. It plays a major role as an inhibitor of muscle growth.

37
Q

What is Insulin-like growth factor 1?

A

A growth factor supplied mainly by the liver which is regulated by IGF-binding proteins. It promotes hypertrophy in adult animals by increasing myotube diameter, suppressing proteolysis, and stimulating protein synthesis.

38
Q

What does testosterone do?

A

Increases muscle hypertrophy by increasing satellite cell proliferation

39
Q

What is the motor end plate?

A

A structure where axonal branches of a motor neuron form contact to a group of target muscle fibers within a single motor unit through presynaptic buttons

40
Q

What are presynaptic buttons?

A

Depressions of muscle fiber are where swellings from the presynaptic motor neurons of the axonal branches are

41
Q

What is the primary synaptic cleft?

A

The synaptic button that occupies a depression

42
Q

What is the secondary synaptic cleft?

A

The sarcolemma of the muscle fiber that forms the infolding deep junctional fold

43
Q

What kind of synapse is the neuromuscular junction?

A

Chemical

44
Q

Where do the synaptic vesicles that carry acetylcholine come from?

A

They are derived from the neuronal soma and are transported via anterograde to the neuromuscular junction

45
Q

How do the synaptic vesicles attach to the presynaptic terminal?

A

They have vesicular docking proteins which attach to the membrane docking proteins

46
Q

What degrades acetylcholine to stop the signal?

A

Acetylcholinesterase hydrolyses acetylcholine into choline and acetyl CoA. The choline is reused to form acetylcholine by choline acetyltransferase

47
Q

What three things are required for axonal transport?

A

Axonal cytoskeleton, motor proteins, and the hydrolysis of ATP

48
Q

What is anterograde?

A

Axonal transport that is kinesin-mediated. Cargo is carried from the soma to the axon terminal

49
Q

What is retrograde?

A

Axonal transport that is dynein-mediated. Cargo is carried from the axon terminal to the soma

50
Q

What is rabies?

A

A neurotropic virus from the bite of a rabid animal. It binds to ACh receptors and replicates. It is transported via anterograde to the salivary glands where it can be transmitted via bite.

51
Q

What is tetanus?

A

A protease produced by the vegetative spore of Clostridium tetani bacteria. It produces a neurotoxin which uses retrograde to enter the CNS and blocks the release of inhibitory mediators. This can cause spasm contraction.

52
Q

What is shingles?

A

It is caused by the virus varicella zoster and causes painful skin rashes and blisters. It enters the nerve body via retrograde and is activated via anterograde when the infected person is stressed

53
Q

What is curare?

A

It comes from various plant extract alkaloid. It binds to the acetylcholine receptor and prevents binding to the nicotinic acetylcholine receptors on the postsynaptic membrane. This can produce muscle paralysis.

54
Q

What is botulinum toxin?

A

An exotoxin from clostridium botulinum which prevents the release of acetylcholine at the presynaptic terminal. This can produce muscle paralysis and dysfunction of the ANS.

55
Q

What is myasthenia gravis?

A

An autoimmune disease with antibodies against acetylcholine receptors. This prevents the binding of acetylcholine to the postsynaptic membrane and causes muscle weakness.

56
Q

What is lambert-eaton myasthenic syndrome?

A

An autoimmune disease with antibodies against the voltage gated Ca channels on the presynaptic terminal. This reduces the influx of Ca and can cause muscle weakness.

57
Q

What are muscle cramps?

A

The sudden onset of painful, involuntary squeezing or contraction of the muscle. There is often a palpable hard knot in the muscle.

58
Q

Why is there a palpable hard knot in the muscle?

A

This is an indication of ATP depletion, because the myosin will be bound to the actin until the ATP binds to it

59
Q

How can you speed up the relief of a cramped muscle?

A

Stretching the affected muscle or contraction of the antagonist muscle

60
Q

What does the presence of creatine kinase in a cramped muscle mean?

A

This is usually indicative of injury to muscle tissue or metabolic damage, which suggests the degree of contraction can be excessive.

61
Q

What triggers exercise associated muscle cramps?

A

Sweat loss leading to dehydration and pH disturbances

Thermal strain

62
Q

What is suspected to cause muscel cramps?

A

Involuntary repetitive high frequency firings of the motor neuron which innervates the cramping motor unit

63
Q

Where do muscle twitches during muscle cramps originate?

A

The peripheral nerve, meaning they have somatic origin

64
Q

Why is pregnancy associated with muscle cramps?

A

The physical distortion of the neuromuscular junction as a byproduct of the fluid retention and joint laxity could be the cause

65
Q

Why are endocrine disorders associated with muscle cramps?

A

Cooler extremities and hypoadrenalism (induces electrolyte imbalance

66
Q

Why are liver disease and cirrhosis associated with cramps?

A

Related to the decrease in intravascular volume and edema due to the decreased production of albumin

67
Q

What is the threshold for cramps?

A

The minimum frequency of electrical stimulation required to induce a cramp

68
Q

What occurs in idiopathic cramps?

A

Motor units fire at unusually rapid rates, however their firing decreases after the initial burst

69
Q

What are muscle spindles?

A

Stretch receptors that can be found in the capsules of the extrafusal muscle fibers

70
Q

What do alpha motor neurons innervate?

A

Extrafusal muscle fibres

71
Q

What do gamma motor neurons from the CNS innervate?

A

Intrafusal muscle fibers. They control their contraction

72
Q

What do tonically active sensory neurons do?

A

Send information to the spinal cord and synapse directly on alpha motor neurons

73
Q

How does the negative feedback of muscle spindles occur?

A

Stretching of extrafusal muscle also stretches the muscle spindle
Increased afferent signals to the spinal cord increases the efferent output through the alpha motor neurons and causes muscle contraction as the firing rate of afferent neuron decreases

74
Q

Why do we have a stretch reflex?

A

To prevent damage from overstretching

75
Q

Where are cramps likely originated?

A

Have a peripheral neurogenic origin, meaning there is spinal involvement

76
Q

How does stretching muscles assist with cramping?

A

This increases the afferent signal frequency to the spinal cord through the spindle sensory neuron which leads to an increase in the frequency of efferent signals to the muscle. This will lead to muscle fatigue and eventually relaxation

PHPY 302 (4 decks)

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