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SPSC 3275 > Neuromuscular Physiology > Flashcards

Neuromuscular Physiology Flashcards

1
Q

What are the two essential components of a muscle and what is their function

A

Contractile proteins (protein filaments): these are responsible for creating tension in the muscle

Connective tissues: these are responsible for taking that tension and transferring it into joint movements (musculoskeletal movements)

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2
Q

What are the 5 components of connective tissues

A
  • Epimysium: tissue surrounds a muscle
  • Perimysium: tissue surround muscle fassicles
  • Endomysium: tissues surround and separate each muscle fibre in a fassicle
  • Sarcolemma: a membrane surrounding each muscle fibre
  • Basement membrane: surrounds the sarcolemma
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3
Q

What are transverse tubules

A

Channels that are extensions of the sarcolemma that transmit action potentials from the sarcolemma to the terminal cisternae

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4
Q

What are the terminal cisternae

A

Terminal cisternae are enlarged areas of the sarcoplasmic reticulum that surround transverse tubes and store calcium

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5
Q

What is the sarcoplasmic reticulum

A

A network of tubular channels that surround myofibrils

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6
Q

T or F: muscle cells are multinucleated

A

True

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7
Q

Describe saltatory conduction

A

The alternating sequence of both myelin sheath and nodes of ranvier which allow nerve impulses to jump from node to node very quickly. Every time the action potential jumps over, it depolarizes, repolarizers and hyperpolarizes.

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8
Q

Outline the components of a motor unit and what a motor unit is

A

A motor unit consists of a motor neuron, its axon (tail), and the muscle fibres it attaches to/controls

A motor unit is an individual motor neuron and the specific muscle fibres it innervates

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9
Q

What is/ are the components of a motor neuron pool

A

A motor neuron pool is the collection of motor neurons that innervate a single muscle

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10
Q

What are the types of neurons

A

Upper motor neurons: originating in the motor cortex crossing over in the spinal cord allowing for contra-lateral control (right brain controls left body)

Inter neurons: inter neurons in the spinal cord connect upper motor neurons to lower ones and sensory neurons to lower ones acting as a relay, relaying the signal from one neuron to the next

Lower motor neurons: in the spinal cord and extend peripherally to innervate muscles

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11
Q

Outline the components of the neuromuscular junction

A

Terminal end bulb

Synaptic cleft

Motor end plate

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12
Q

Describe what happens at the neuromuscular junction to produce muscle action/movement/contraction

A

An action potential reaches the terminal and bulb, depolarizing it and opening a voltage gated calcium channels. Calcium enters the terminal and bulb and triggers. The release of acetylcholine from precynaptic vesicles to diffuse into the synaptic cleft where they bind to nicotine receptors on the motor end plate. This opens neurotransmitter, gated sodium channels, causing sodium to enter the motor and plate depolarizing the motor end plate. As the sarcolemma becomes depolarized the T-tubules become depolarized causing the action potential to travel down to the sarcoplasmic reticulum. The depolarization of the sarcoplasmic reticulum opens voltage gates calcium channels and the terminal cisternae release calcium letting calcium into the sarcoplasm and bind to troponin causing muscle action by the calcium pulling tropomyosin out of the way for cross bridges to form

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13
Q

What is cholinesterase

A

An enzyme which degrades acetylcholine within 5ms of its release from synaptic vesicles

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14
Q

Describe depolarization

A

This is caused when sodium ions rush into a tissue with the opening of voltage, gated sodium channels

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15
Q

Describe repolarization

A

This is caused by the closing of sodium ion channels and the opening of potassium ion channels

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16
Q

Describe hyper polarization

A

This occurs due to an excessive potassium channels and potassium efflux from the cell

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17
Q

What is the role of calcium, acetylcholine, sodium, and potassium in excitation

A

Calcium: floods, the sarcoplasm, and binds to troponin

Sodium: after moving from the extracellular space it changes the membrane potential

Acetylcholine: binds to nicotinic receptors

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18
Q

Describe cross bridge cycling in phases

A

In phase 1 myosin heads are at rest and there is ATP present within

In phase 2, ATPase in the myosin head gets activated when calcium floods the sarcoplasm performing a hydrolysis action and cleaves ATPase into ADP plus a phosphate molecule

In phase 3 calcium pulls, tropomyosin out-of-the-way and the myosin head, then binds to act in creating a cross bridge

In phase 4, the ADP plus P are released from the myosin head, pulling the act and towards the middle line creating tension

At the end, a new molecule of ATP binds to the myosin head, causing the active and myosin disassociate

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19
Q

What are the conduction speeds of motor neurons?

A

All motor neurons have different speeds, the diameter of the motor neuron is directly related to the conduction speed. For example, type 2X motor neuron fires have the fastest conduction speed due to larger size and width.

20
Q

Describe motor unit recruitment

A

Motor unit recruitment refers to the number/amount of motor units that are recruited/firing in different muscle actions. The number of motor units recruited depends on things such as the intensity, force, and speed of a muscle action.

21
Q

Describe the size principal

A

This principal states that motor units are recruited/used from smallest and size to largest in size, depending on the intensity of the muscle action

Smaller motor neurons have a low threshold requirement which requires small degrees of neural drive in order to fire and vice versa for type two

22
Q

Describes all or none principle

A

This principal states that when a Moto unit fires, all the muscle fibres of that motor unit will fire/contract simultaneously

23
Q

What is the difference between a motor unit and a motor neuron pool?

A

A motor unit is a single motor neuron and the muscle fibre controls

A motor neuron pool is a group of neurons that control a single muscle

24
Q

Describe rate code

A

Simply, rate code is the frequency of motor units firing. The frequency of action potentials being fired.

If the motor unit fires after the muscle has returned to a relaxed state, then the magnitude of the next muscle twitch will be the same as the first twitch

25
Q

What is known as a sustained muscle contraction produced by a maximal frequency rate of motor unit firing

A

Tetanus

26
Q

What is the smallest unit of muscle contraction and occurs in a single nerve impulse?

A

A muscle twitch

27
Q

Define central fatigue

A

Central fatigue are processes in the CNS that reduce neural drive (muscle force production). This fatigue is harder to recover from intakes more time to do so.

It could also be systemic that if you experience upper body fatigue, it could affect the lower body and vice versa

28
Q

Define peripheral fatigue

A

Peripheral fatigue or processes that occur at or distal to the neuromuscular junction that has suppressed muscle action (muscle force production). Anything within the muscle fiber. Very easy to recover from.

29
Q

Explain the reflex action initiated by muscle spindles, and Golgi tendon organs

A

Muscle spindles, which are in the muscle belly, initiate contraction of the muscle that is being stretched and the opposing muscle to relax

Golgi tendon organs, which are at the junction between the muscle and the tendon, detect muscle tension/force and trigger a relaxation response. When tension in the muscle is too high (autogenic rehibition).

30
Q

What is the length tension relationship?

A

This is the capacity to form cross bridges at different muscle length. For example, at resting length for the biceps, which is around 90°, there’s the highest potential for cross bridges, meaning that at this length the bicep can produce the most force. As the muscle lengthens, passive tension increases from titin

31
Q

What is the force velocity curve?

A

As concentric contractions increase in velocity/speed we produce less force and vice versa for E centric contractions

32
Q

What is passive tension and active tension produced from

A

Passive tension is produced from titin

Active tension is produced from actin and myosin

33
Q

List some neuromuscular adaptations

A

In increased central Drive
Increased motor synchronization
Decreased threshold potential
Increased motor unit firing rate
Decreased sensitivity of GTO
Increased sensitivity of muscle spindles

34
Q

What types of training would stimulate neuromuscular adaptations?

A

Any, but it really comes down to intensity and duration

35
Q

Define hypertrophy

A

The enlargement of a tissue/muscle so it gets heavier and bigger

36
Q

Which muscle type has the greatest capacity for hypertrophy?

A

Fast twitch, especially type 2X has the greatest capacity for hypertrophy

37
Q

What is the difference between myofibrillar and sarcoplasmic hypertrophy

A

Myofybrillar hypertrophy is an increase in the protein content of a muscle fiber. A muscle fibre can have an increase in my files or an increased quantity in protein filaments of a mop file. These processes will cause the muscle to making the muscle appear bigger.

Plasmic hypertrophy is an increase in the volume of plasmic fluid a temporary increase in muscle size from in simple terms of workout pump

38
Q

What are the three stimuli for hypertrophy?

A

Mechanical stimuli: mechanical tension refers to the force generated during a muscle action stimulates hypertrophy through mechanotransduction

Metabolic stimuli

Muscle damage: the disruption of the sarcomere and refers to micro trauma.

39
Q

Explain the response in muscle damage

A

There was a release of inflammatory mediators known as cytokines and chemokines. recruited macrophages then come to remove the damaged muscle and secrete growth factors (IGF – one). Myogenic satellite stem cells between the sarcolemma and basement membrane, then become active in response to the inflammation to reproduce, fusing to existing cells or making new myofibrils among themselves, which provides the precursor needed for muscle repair which repair stronger and bigger to withstand more weight/outside forces.

40
Q

Do you have to be big to be strong?

A

No, an increase in strength can occur without hypertrophy, but muscular strength cannot occur without neural adaptions

41
Q

Define sarcopenia

A

Sarcopenia can be defined as age related loss of muscle mass and its function.

42
Q

Outline two mechanisms of sarcopenia

A

Atrophy, which is when muscle fibres decrease in size shrinking the muscle. This is a decrease in PCA (physiological cross-sectional area).

Muscle fibre loss, which is the process of muscle fibres becoming deviated the neuromuscular junction slowly diminishes/disappears

43
Q

Define and describe anabolic resistance

A

Anabolic resistance can be thought of as the diminished ability of the muscle to respond to anabolic stimuli such as protein intake, or anabolic exercise

44
Q

What is the difference between denervation and reinnervation

A

Denervation is when motor neurons slowly remove themselves when those muscles are not being used. An example of this is use it or lose it.

Ration is the formation of new motor neurons. For example, fast which muscle fibres are not used so they become denervated. Those motor neurons pass down to the type one fibres so new branches/axon tails are produced connecting to the new muscle

45
Q

What are the recommended activity levels for someone, my age by the government?

A

A minimum of 150 minutes of moderate to vigourous aerobic physical activities

Strength training at least two times a week with major muscle groups

7 to 9 hours of adequate sleep (set bedtime and wake up times)

46
Q

How is muscle mass regulated?

A

By a balance of protein, synthesis and protein breakdown with the two major environmental influences being food, intake, and physical activity

47
Q

List some preventative measures for sarcopenia

A

Early intervention

Resistance training

High-quality protein source intake

SPSC 3275 (3 decks)

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