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Systems final test > Unit 5- Skeletal muscles > Flashcards

Unit 5- Skeletal muscles Flashcards

1
Q

what are some characteristics of the muscle tissues

A

1)Transforms chemical energy into mechanical energy
2)Responsible for movement, size and shape changed of the organs and the whole body
3)Cells are called MOTORCYCLES OR FIBREs, as they are longer than thicker

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2
Q

what is excitability?

A

Ability to induce an action potential in response to a chemical stimulus

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3
Q

what is contractility?

A

refers to the ability of the muscles to perform mechanical work in response to a stimulus. It is what shortens the muscle fibers

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4
Q

what is extensibility?

A

ability of a muscle to be stretched without getting harmed

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5
Q

what is elasticity?

A

ability of the muscle fibres to return to their original state after shortening or stretching

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6
Q

what are the 3 types of muscles

A

1)Skeletal
2)smooth
3)Cardiac

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7
Q

what are skeletal muscles?

A

Arranged in the majority of the body’s voluntary muscle mass

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8
Q

What are cardiac muscle?

A

Involuntary, limited to the heart

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9
Q

What are smooth muscles?

A

Its cells that do not have transverse striations

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10
Q

what type of muscle cell is this?

A

Cardiac muscle cell

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11
Q

What type of skeletal muscle cell is this?

A

skeletal

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12
Q

what type of muscle cell is this?

A

Smooth muscle cell

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13
Q

what are t-tubules?

A

Transverse tubules in the sarcolemma (continuation of the membrane). They rapidly spread action potentials from the surface to the inside of the fiber.

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14
Q

what is the sarcoplasmic reticulum?

A

Widely extended. It pumps Ca2+ from the cytoplasm and store it inside.

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15
Q

what are myofibrils?

A

contractile elements of the skeletal muscle fibre. They are made of protein filaments or myofilaments.

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16
Q

What are the two proteins on the fibrils that allow for contractility?

A

Actin (Think filament)
Myosin (Thick filament)

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17
Q

What are the two proteins on the fibrils that allow for regulation?

A

Troponin
Tropomyosin

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18
Q

where is the sarcomere?

A
19
Q

where is the H band

A
20
Q

Where is the M line

A
21
Q

where is the Z-Disc

A
22
Q

Where is the A band

A
23
Q

Where is the I band

A
24
Q

What is the sarcolemma excitation stage of the electrical events?

A

An action potential is needed first to induce the contraction

25
Q

what is a contraction stage of electrical events?

A

the action potential triggers the contraction of myofibrils

26
Q

What is the relaxation stage for electrical events?

A

End of the process

27
Q

what is the end plate?

A

Specialized area of the sarcolemma that folds to the surrounding terminal part of the somatic axon

28
Q

what is the neuromuscular junction?

A

It is a synapse between the somatic motor neuron and the skeletal muscle fiber

29
Q

Explain the regulatory proteins of contraction in the relaxed stage and when calcium is released

A

Relaxed stage: Tropomyosin blocks the total attachment between the actin and myosin

Calcium: When calcium is released from the SR, It binds troponin. This makes tropomyosin shifts allowing the total attachment between actin and myosin

30
Q

What is “Rigor Mortis”

A

when several hours after death all the skeletal muscles reached a contracted and rigid state.

It is a contraction that occurs without action potential sor calcium release

this stiffness is caused by a total loss of ATP

31
Q

what is a motor unit?

A

Every muscle fiber that is controlled by the same axon

32
Q

what are some features of motor units?

A

1)The size of the motor unit is proportional to the accuracy of the movements developed by a muscle

2)The smaller the number of fibers in the motor unit the more accurate the movements developed by the muscle

3)the higher the amount of fibres in the motor unit the less accurate the movement developed by the muscle

33
Q

In a muscle contraction, what is the latency period?

A

Duration: 2ms
-Calcium si released from the SR

34
Q

In a muscle contraction, what is the contraction period?

A

Duration: 10 t0 100ms
-Calcium binds to troponin
-Sliding filaments

35
Q

In a muscle contraction, what is the relaxation period?

A

Duration: 10 to 100ms
-Calcium is pumped back into the SR

36
Q

In a muscle contraction, what is the refractory period?

A

Duration: 5ms for skeletal muscles
-The muscle cannot respond due to loss of excitability

37
Q

What are type 1 muscle fibers?

A

-Slow and fatigue-resistant
-smallest motor units,
-they develop weaker tension, but for a longer time

38
Q

what are type IIa muscle fibers?

A

-Fast and fatigue-resistant
-intermediate motor units
-They possess some aerobic capacity that allows them to develop stronger tension for a few minutes

39
Q

What are type IIx motor fibers?

A

-Fast but not resistant to fatigue
-biggest motor units
-controlled by phasic motor neruons
-they develop intense tension for short time due to the anaerobic metabolism

40
Q

What is the principle for the ALL OR NONE FOR MUSCLE CONTRACTION

A

When a motor neuron triggers an action potential, all the fibers of the motor unit are stimulated simultaneously.

When a muscle fiber is stimulated it either contracts with all the possible tension or does not contract at all.

41
Q

what are the two mechanisms that control the tension generated by a whole muscle?

A

1)Motor unit summation or recruitments
-to increase the intensity we stimulate more motor units (by size order I-IIa-IIx)

2)Frequency summation
-to increase the duration, we increase the frequency of the stimulation (number of action potential coming from the nerve)

42
Q

describe the phases of an action potential

A

Sure! Here’s a more concise summary of the action potential phases:

  1. Resting Potential The neuron is at about -70 mV, maintained by the sodium-potassium pump and leak channels.
  2. Depolarization: If the threshold (~ -55 mV) is reached, voltage-gated Na⁺ channels open, and Na⁺ floods in, making the cell more positive.
  3. Peak: The potential hits +30 to +40 mV. Na⁺ channels inactivate, stopping further Na⁺ influx.
  4. Repolarization: K⁺ channels open, K⁺ exits the cell, and the potential becomes negative again.
  5. Hyperpolarization: K⁺ channels close slowly, causing a temporary dip below resting potential.
  6. Return to Resting: The sodium-potassium pump restores the resting state.
43
Q

describe the formation of a cross bridge.

A

1)Calcium Release: Calcium ions (Ca²⁺) bind to troponin, causing tropomyosin to move and expose binding sites on actin.

2)Myosin Binding: The myosin head, energized by ATP, binds to the exposed site on actin, forming the cross-bridge.

44
Q

What are some factors that affect the generated muscle tension

A

1)Number of cross-bridges between actin and myosin
2)Muscle composition
3)Motivation
4)Contraction speed
5)Muscle length
6)Muscle optimal length
7)Biomechnaical aspects

Systems final test (4 decks)

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