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Physiology > Muscle Physiology > Flashcards

Muscle Physiology Flashcards

1
Q

5 Functions of Muscles

A
  1. Body Movement
  2. Stability
  3. Movement of substances within the body
  4. Heat production
  5. Regulation of organ volume via sphincters
    (MMSHV)
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2
Q

Functional Characteristics of Muscles (4)

A 
Excitability (responsiveness or irritability)
Contractility
Extensibility
Elasticity
(ECEE)
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3
Q

3 Types of muscle

A

Smooth, Cardiac, Skeletal

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4
Q

Specialized intercellular junction when cardiac cells meet. It allows muscle action potential to spread rapidly from one cell to another.

A

Intercalated discs

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5
Q

3 layers of connective tissue found in skeletal muscles.

A

Endomysium, Perimysium, Epimysium

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6
Q

At the end of the muscle, the connective tissue layers come together and form a ____. It connects the muscle to the bone.

A

Tendon

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7
Q

Hundreds of long, cylindrical structure that makes up the skeletal muscle fibre. Each of this contains bundles of threadlike proteins called filaments.

A

Myofibril

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8
Q

2 types of filaments

A

Thin and thick filaments

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9
Q

Filaments that is made up of a protein called actin - hence actin filament.

A

Thin filament.

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10
Q

Filaments that is made up of a protein called myosin - hence myosin filament.

A

Thick filament.

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11
Q

Myosis takes up about ___ of protein within skeletal muscles.

A

2/3

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12
Q

The actin and myosin filaments in each myofibril are arranged into repeated units caled _____. It is the working unit of a skeletal muscle.

A

Sacromeres

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13
Q

The signal form the nervous system travels to the muscle via ____.

A

motor neuron

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14
Q

The link between the neuron and the skeletal muscle occurs at a junction called the ____.

A

neuromuscular junction

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15
Q

At the neuromuscular junction, the neuron terminal is separated from the muscle fibre by a gap called the ______.

A

synaptic cleft

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16
Q

The neuron carries a signa (AP-electric current) to the neuron terminal which causes it to release a chemical called NT. The NT crosses the synaptic cleft and is taken up by the skeletal muscle membrane. The excitation caused in the muscle, when it takes up the NT, makes the muscle _____.

A

contract

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17
Q

The muscle works in conjuction with the bone like a ____ system.

A

lever

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18
Q

A muscle whose contraction is mainly responsible for flexion.

A

Prime Mover (i.e., bringing 2 bones close together)

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19
Q

A muscle that opposes the action of the prime mover.

A

Antagonist

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20
Q

The relatively stationary of skeletal muscles.

A

Origin

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21
Q

The point at which a muscle attaches to a bone a produces movement opposite from its stationary origin.

A

Insertion

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22
Q

Anchors the muscle to the connective tissue covering of a skeletal muscle or the fascia of the other muscles.

A

Tendons or aponeurosis

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23
Q

Each muscle is served by at least ____ nerve which contains axons of a hundreds of motor neurons.

A

ONE

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24
Q

Each muscle fibre is innervated by an ____.

A

axon terminal

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25
Q

The force exerted on an object by the contraction of a group of muscle fibres.

A

Muscle tension

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26
Q

The force exerted on the contracting muscle.

A

Load

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27
Q

True or false?

the muscle may or may not shorten when it contracts.

A

True

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28
Q

What stimulant causes skeletal muscles to contract?

A

Ach by motor neurons

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29
Q

The contraction of muscle requires that ___ binds to molecules on the myofibrils.

A

Ca++

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30
Q

The Ca++ that binds to the myofibril is released when the electric current traveling from the muscle membrane reaches the ______.

A

muscle fibre

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31
Q

The presence of the released Ca++ and ATP causes thick and thin filaments to ____ over each other.

A

slide

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32
Q

The movement of filaments causes formation of _____. The formation causes the skeletal muscle to shorten, hence, the muscle is contracted.

A

cross bridges

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33
Q

Thhis theory states that during contraction of striated muscle, the thin filaments slide past the thick filament, that is, the actin and myosin filaments slide pass each other.

A

Sliding Filament Theory of Contraction

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34
Q

In relaxed striated muscle fibres, the thin and thick filaments overlap only at the ends of the ___ band.

A

A band

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35
Q

When the muscle fibre is stimulate by nerve impulses, the head of the myosis latches on to the _________ on the actin molecule to commence the sliding of filaments.

A

myosin binding site

36
Q

Cross-bridge attachments are formed and broken with the help of ___ and ____. This event occurs in all the sarcomeres at the same time resulting in the shortening of the muscle.

A

Ca++ and ATP

37
Q

Skletal muscles are stimulated by motor neurons of what system?

A

Somatic Nervous System

38
Q

The cell bodies and axons of motor neurons are located in the ____ or ____.

A

Brain or spinal cord

39
Q

The axons form tracts which leave the CNS and make contact with the muscles at ________.

A

neuro-muscular junctions.

40
Q

Each muscle fibre has one neuro-muscular junction located _____ along the fibre.

A

mid-way

41
Q

The axon terminal and the muscle fibre are separated by the synaptic cleft which is filled with a gel-like substance made up of ____ and _____.

A

glycoprotein and collagen fibres

42
Q

The axon terminals contain vesicles with ____.

A

Ach

43
Q

the through-like part of muscle fibre’s plasma membrane (sarcolemma) that help from the neuromuscular junction.

A

motor end plate

44
Q

AP travels via motor neuron axons to the axon terminals.Once at the axon terminal, the AP causes Ca++ gates on the sarcolemma to open. Ca++ moves into the axon terminal bind to the vescicle and causes the vesicle to migrate axon terminal membrane. The Ach is released by the axon terminal into the synaptic cleft.
- The Ach molecules migrate across the gap and bind to the motor end plate, then an electric event is triggered in the sarcolemma. Ach in the junction and that on receptors are quicly broken down by acetylcholinesterase (Ach-ase) present in the gap. The breakdown of Ach stops the action in the junction and the contration of muscles.

A

Nerve Stimulus in Muscles

45
Q

Composition of Ach

A

Acetic acid + choline (blood vessels)

46
Q

Disorder of the neuromotor junction. Leads to muscle weakness and fatigue.

A

myasthenia gravis

47
Q

events in a single stimulation of muscle fibre. (6)

A
  1. AP moves down the t-tubule.
  2. Sarcoplasmic reticulum releases Ca+
  3. Ca++ diffuses onto actin filament.
  4. Filaments slide pass each other.
  5. Sarcoplasmic reticulum reuptake Ca++
  6. Muscle relax
48
Q

2 Types of Muscle Contraction

A
  1. Muscle Twitch and Summation

2. Graded Muscle Response

49
Q

Abnormal muscle response to stimuli.

  • Rapid contraction and relaxation of a muscle fibre or group of muscle fibres.
  • Response seen as a result of a single AP from a motor neuron.
  • Begins from latent period where muscle tension is beggining and increased, and is followed by a period of contraction where actin-myosin cross-bridges are active. A period of relaxation follows the contraction period which is characterized by the re=uptake of Ca++ in SR. Muscle remains constant throughout.
A

Twitching

50
Q

Muscle respond to a single nerve stimulus. Muscles usually contract in response to a series of AP not just one.

A

Muscle Twitch

51
Q

If the frequency of nerve stimulation is increased so that one stimulus arrives before the preceding contraction phase is over, the tension produced in the muscle will be greater than that created by a single twich and the contraction is greater.

A

Summation or adding of contraction occurs

52
Q

Normal muscle response is usually smooth and varies in stregth as the conditions require. This type of response is called _______.

A

Graded Muscle Response

53
Q

Two categories of Graded Muscle Response

A
  1. The more rapid the firing of the motor neurons, the greater the muscular force of contraction by continued release of Ca++.
  2. If the intensity of the stimulus to a muscle increases, then the number of muscle fibres responding to the stimulus increases. And as the number of contracting fibres in the muscle increases, the force of contraction of the muscle increases.
54
Q

Process in which If the intensity of the stimulus to a muscle increases, then the number of muscle fibres responding to the stimulus increases. And as the number of contracting fibres in the muscle increases, the force of contraction of the muscle increases.

A

Recruitment or multiple motor unit summation.

55
Q

If the frequency of stimulation of the muscles increases suffieciently a state is reached where the muscle relaxation disappears and the contraction fuse to produce a sustained contraction called ____.

A

complete tetanus

56
Q

The level of stimulation which causes the first contraction to occur.

A

Threshold stimulus

57
Q

The level of stimulation which causes ALL THE FIBRES in a muscle contract.

A

Maximal stimulus

58
Q

A muscle that is starting to contract after a long period of relaxation will have a contracting force of about 1/2 the strength of later contractions.
This may be explained by the fact that only small amounts of Ca++ is released intracellularly at first; but as more and more stimulation occurs more and more Ca++ is released resulting in stronger and stronger contraction. This is the basis for warm up activities before rigorous muscle exercise.

A

treppe

59
Q

The ongoing baseline activity of a muscle or muscle group. In the case of skeletal muscles, it represents a partial contraction of the muscle(s). It is brought about the spinal cord reflex to keep muscle firm, healthy and ready for respond. It doesn’t produce active movement.

A

Muscle Tone

60
Q

Sustained partial contraction of muscles that maintains posture. It is brought about by the asynchronic contraction of small numbers of muscle fibres producing tautness rather than movement.

A

Tonic Contraction

61
Q

A decrease of muscle tone or resistance to stretch.

A

Flaccidity (flabbiness)

62
Q

Increase muscle tone that accompanies higher nerve lesions such as stroke and Parkinsons disease. It is cause by a decrease in transmission of nerve impulses down inhibitory corticospinal tract.

A

Spasticity

63
Q

Muscle contraction in which there is no appreciable shortening of the muscle. It occurs when a muscle tries to move a load which is greater than the force of muscle can produce.

A

Isometric contraction

64
Q

Muscle contraction in which the muscle shortens in length and move one bone closer to another. Hence, contraction produces movement and reduces the angle between bones and joint. Once sufficient tension develops to move the load the tension in the muscle remains unchanged. The contraction begins when the internal tension builds to the point that it overcomes the resistance.
IN OTHER WORDS; THE MUSCLE SHORTENS, MOVES THE LOAD, AND MAINTAINS ESSENTIALLY THE SAME TENSION FROM THEN ON.

A

Isotonic Contraction

65
Q

Sustained contraction. Result from the frequency of muscle stimulation to its maximum point where further summation of tension cannot occur.

A

Tetanus

66
Q

The process by which a number of muscle fibres are made to contract simultaneously. To increase force developed in a muscle, a number of fibres in the muscle must contract simultaneously. This is accomplished when many neurons are activated by the CNS so that there is a large increase in the number of motor units activated.

A

Recruitment

67
Q

The only energy source that muscle can use for contraction. It is required by the muscles to provide energy for cross-bridge movement, actin-myosin detachment and pumping of Ca++ back to the SR. Hence, it used source must be quickly replenished.

A

ATP

68
Q

ATP broken down.

A

ATP = ADP + P + energy

69
Q

3 mechanisms for regeneration of ATP

A
  1. Direct phosphorylation of ADP by Creatine Phosphate
  2. Anaerobic Mechanism
  3. Aerobic Respiration
70
Q

ATP regeneration mechanism that involves the use of enzyme creatine kinase. Muscle cells store 4-5 times more creatine phosphate (a high energy molecule) than ATP. When ATP levels in a working muscle are depleted the following chemical reaction occurs to restore ATP; if but for a short time:
Creatine Phosphate + ADP = Creatine + ATP

A

Direct phosphorylation of ADP by Creatine Phosphate

71
Q

When stored ATP and ATP from creatine phosphorylation are depleted, the muscle turns to anaerobic glycolysis for production of ATP.

  • This process is conducted both in the presence and absence of O2 but it doesnt require O2 for the ATP production.
  • The process begins when the glucose from the blood or glucose obtained from the breakdown of glycogen enters into glycolysis in the cells cytosol. A molecule of glucose produces 2 ATP anf pyruvic acid lactic acid. The lactic acid produces is released into the blood. The lactic acid is subsequently picked up bu the heart, liver or kidney cells and used as a source of energy.
A

Anaerobic Mechanism

72
Q

About 95% of ATP used for muscle activity comes from this process which occurs in the fibres mitochondria. Within the mitochondria, pyruvic acid, fatty acids, and amino acids are used to produce ATP. Oxygen is required.

A

Aerobic respiration

73
Q

If exercise continues and is vigorous enough, _____ is used to produce the ATP.

A

muscle glycogen

74
Q

After about 30 minutes of vigorous exercise _____ becomes the major source of energy..

A

Fatty acids

75
Q

2 sources of oxygen by muscles

A
  1. O2 that diffuses into the muscle fibre from the blood

2. O2 stored in the muscle in myoglobin.

76
Q

Both myoglobin and ____ are oxygen binding proteins. They bind oxygen when it is plentiful and release it when its scarce.

A

Hemoglobin

77
Q

Aerobic respiration provides ATP for as long as is requred provided _____ and _____ are available. 38 ATP net gain per glucose..

A

O2 and nutrients

78
Q

2 consequences of muscle activities

A
  1. Muscle fatigue

2. Ionic imbalance

79
Q

State of physiologic inability of muscle to respond to stimuli.
- Physiologic cause has not been identified but it appears that ATP depletion leads to a state where actin-myosin cross-bridges which are formed are unable to break, hence a state of continuous contraction (contracture) ensues. (e.g. writers camp)

A

Muscle Fatigue

80
Q

________ build up in a muscle appears to cause muscle aches, tired muscles but not physiologic fatigue.

A

Lactic Acid

81
Q

Consequence of muscle activity that is because of AP activity. K+ is lost from the cell and tend to remain in the fluid of the T-tubule, thus blocking the release of Ca++. Na+ remains in the cell as the Na+/K+ pump is unable to remove it quickly. Intense exercise over short duration may produce fatigue due to this.

A

Ionic Imbalance

82
Q

The extra amount of oxygen that the body must take in to replace that used up in a vigorous exercise.
- O2 must be repaid to the Hb in the blood and from the myoglobin. The muscle consume extra oxygen after exercise because they are warmer and have higher metabolic rate. In addition, extra O2 is required to metabolize lactic acid produces by skeletal muscle anaerobic activity. Hence it can be paid by rapid breathing after exercise ends.

A

Oxygen debt

83
Q

2 types of muscle fibres categorized on their speed of contraction.

A
  1. Slow-twitch (Type 1) fibre

2. Fast-twitch (Type 2) fbre

84
Q

Type of muscle fibres categorized on their speed of contraction.
- adapted for anaerobic respiration. They have rich blood supply, mitochondria, and myoglobin. These fibres are found in the soleus muscles.

A
  1. Slow-twitch (Type 1) fibre
85
Q

Type of muscle fibres categorized on their speed of contraction.
- thicker and have less amount of blood vessel and mitochondria and myoglobin. They produce lactic acid because they have a store of glycogen. These fibres are found in the extrocular muscles of the eye.

A
  1. Fast-twitch (Type 2) fbre
86
Q

This has a mixture of both type 1 and 2 fibres.

A

Gastrocnemius

87
Q

A large iron-containing red pigment protein which binds the oxygen.

A

Myoglobin

Physiology (9 decks)

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