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Physiology > Chapter 9: Muscular System > Flashcards

Chapter 9: Muscular System Flashcards

1
Q

What are the three types of muscle tissue?

A

Skeletal, smooth, cardiac

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2
Q

Characteristics of skeletal muscle

A

-multinucleated
-many mitochondria
-transverse tubules
-myofibrils and sarcomeres
-sarcolemma
-sarcoplasm
-sarcoplasmic reticulum

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3
Q

Sarcolemma

A

Plasma membrane
-contains T tubules

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4
Q

Transverse (T) tubules

A

Aid in muscle contraction; associated with sarcolemma

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5
Q

Sarcoplasm

A

Cytoplasm

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6
Q

Sarcoplasmic reticulum

A

Smooth ER

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7
Q

Myofibrils

A

Functional unit of muscle fibre
-composed of thin and thick filaments in cylindrical bundles

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8
Q

What is the function of a myofibril?

A

Gives skeletal and cardiac muscle their characteristic striated appearance

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9
Q

Thick filaments

A

Composed of myosin

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10
Q

What composes a myosin molecule?

A

Two large, intertwined polypeptide heavy chains

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11
Q

What forms a cross bridge?

A

Globular heads at the end of myosin heavy chains

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12
Q

What is the function of a cross bridge?

A

Makes contact with thin filament

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13
Q

What is the function of the two light chains on the globular heads of myosin?

A

Inherent ATP-ase activity
-one attaches to the thin filament, one attaches to ATP

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14
Q

Thin filaments

A

Composed of actin, nebulin, troponin, tropomyosin

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15
Q

What in the thin filament serves as the binding site for myosin?

A

Actin molecules

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16
Q

Tropomyosin

A

Blocks myosin binding site on actin filament
-rod shaped molecule composed of two intertwined polypeptides

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17
Q

Troponin

A

Regulates Ca2+
-composed of three subunits (I, T, C)
-holds tropomyosin in its blocking position

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18
Q

Sarcomere

A

Thick and thin filaments together
-from z band to z band

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19
Q

Terminal cisternae

A

Enlarged regions on SR that contains a large amount of Ca2+

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20
Q

Calsequestrin

A

Binding protein in terminal cisternae, helps hold a lot of calcium

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21
Q

What lies between terminal cisternae of adjacent segments of SR?

A

T-tubule

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22
Q

Contraction

A

Refers to actin fibres sliding past myosin fibres

23
Q

What always follows a contraction force?

A

Relaxation

24
Q

Motor unit

A

Motor neuron and all the skeletal muscle fibres it innervates

25
Q

Describe the axon of a motor neuron.

A

Myelinated, largest diameter

26
Q

Neuromuscular junction

A

Axon terminal junction of motor endplate

27
Q

Motor end plate

A

Muscle fibre plasma membrane lies directly under the terminal portion of the axon

28
Q

What is one factor of all neuromuscular junctions?

A

All are excitatory.

29
Q

Function of acetylcholinesterase

A

Breaks down ACh

30
Q

Describe troponin and tropomyosin in a resting muscle fibre.

A

Block the interaction of cross-bridges with the thin filament

31
Q

What happens when Ca2+ binds to troponin?

A

Induces a shape change, relaxes inhibitory grip on tropomyosin, moves away from myosin binding site

32
Q

Dihydropyridine (DHP) receptor

A

Modified voltage-sensitive Ca2+ channel on T-tuble

33
Q

Ryanodine recpetor

A

Protein embedded in SR that forms Ca2+ channel

34
Q

Sliding filament mechanism

A

Generative force behind muscle contraction; involves overlapping thick and thin filaments within each sarcomere

35
Q

In the shortening of a sarcomere during a muscle contraction, is there a change in length of the filaments?

A

Thick and thin filaments do not change length, only their amount of overlap

36
Q

Cross bridge

A

Forms between actin and myosin due to Ca2+ increase

37
Q

What is released from myosin when cross bridges bind to actin?

A

ADP and Pi, producing angular movement

38
Q

How do cross bridges on myosin dissociate from actin?

A

ATP binds to myosin, breaking linkage to actin

39
Q

How is the myosin cross bridge reenergized after cross bridge to actin dissociates?

A

ATP binds to the cross bridge

40
Q

Tension

A

Force exerted on an object by contracting a muscle

41
Q

Load

A

Force exerted on a muscle by an object

42
Q

Twitch

A

Mechanical response of muscle fibre to a single action potential

43
Q

Latent period

A

Period of time between action potential and onset of contraction

44
Q

Contraction time

A

Beginning of tension development at the end of latent period to peak tension

45
Q

Relaxation time

A

Peak tension until tension declines to 0

46
Q

Isometric contraction

A

When a muscle develops tension but does not shorten or lengthen; supports load in constant position

47
Q

Isotonic contraction

A

Contraction in which the muscle changes length while the load on the muscle remains constant

48
Q

How is it possible that a second action potential can be initiated during a period of mechanical activity?

A

action potential lasts 1-2 ms, but the twitch last for 100+ ms

49
Q

Summation

A

Increase in muscle tension from successive action potentials occurring during a phase of mechanical activity

50
Q

Tetanus

A

Maintained contraction in response to repetitive stimulation

51
Q

Fused tetanus

A

Full muscle contraction

52
Q

Unfused tetanus

A

Sporadic stimulus

Physiology (8 decks)

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