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Year 1 Animal Physiology > 4. Musculoskeletal System > Flashcards

4. Musculoskeletal System Flashcards

Skeletal Muscle Smooth and Cardiac Muscle

1
Q

What are the four primary types of tissue?

A

Muscle, Nervous, Epithelial and Connective Tissue.

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2
Q

Describe the Function of Connective Tissue

A

Connects, Supports and Anchors various body parts and has relatively few cells dispersed within an abundance of extracellular material.

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3
Q

Give 2 examples of connective tissue.

A

Tendons, Bone and Blood

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4
Q

Describe the structure and function of Bone.

A

Comprises of mineralised collagen fibres embedded in an amorphous ground substance. Calcium gives strength and collagen gives flexibility. 30% organic and 70% inorganic.

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5
Q

Name the three types of muscle and their locations in the body.

A

Skeletal Muscle (in muscular system), Cardiac muscle (in heart) and smooth muscle (Appears throughout body as components of hollow organs and tubes.

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6
Q

Name the two ways muscles can be classified.

A

Striated or unstriated, and voluntary and involuntary.

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7
Q

Is Skeletal Muscle Unstriated and voluntary?

A

No its Striated and voluntary

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8
Q

Is Cardiac Muscle Striated and involuntary.

A

Yes

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9
Q

Is smooth muscle Striated and voluntary

A

No its Unstriated and Involuntary.

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10
Q

What is the function of contraction?

A

Allows movement of whole body or parts of the body, allows manipulation of external objects, allows contents to be propelled through various tubes and it allows emptying of contents of certain organs to external environment.

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11
Q

Describe the organisation of skeletal muscle.

A

Muscle made up of a number of muscle fibres lying parallel to one another and held together by connective tissue. It is multi nucleated, large, elongated and cylindrically shaped and fibres extend entire length of muscle

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12
Q

What two proteins make up myofibrils

A

Myosin (thick) and Actin (thin)

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13
Q

What does the A band represent?

A

Region which consists of thick filaments along with portions of thin filaments that overlap on both ends of thick filaments.

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14
Q

What does the H zone represent?

A

Region within the middle of A band where thin filaments don’t reach

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15
Q

What does the M line represent?

A

Extend vertically down centre of A band within mid-part of H zone

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16
Q

What does the I band represent?

A

Made of remaining bit of thin filaments that don’t project into A band

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17
Q

What is a Sarcomere?

A

Functional unit of skeletal muscle (found between two Z lines)

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18
Q

What is Titin?

A

A large, very elastic protein which entends in both directions from M line along length of thick filament to Z lines at opposite ends of sarcomere.

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19
Q

Name the two important roles of Titin.

A

Helps to stabilise site of thick filaments in relation to thin filaments and increases muscle’s elasticity by acting like a spring.

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20
Q

Describe the structure of Myosin.

A

Consists of two identical tail ends wrapped each other and two globular heads project out at one end. Tails oriented toward centre of filament and globular heads point outwards at regular intervals.

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21
Q

What is the role of the head of myosin?

A

Form cross bridges between thick and thin filaments.

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22
Q

What are the two important sites essential for contraction on crossbridges

A

Actin-binding site and Myosin ATPase site.

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23
Q

What shape are actin molecules?

A

Spherical

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24
Q

What do each actin molecule contain?

A

Special binding site for attachment with myosin cross bridges.

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25
Q

Name the two other proteins found on thin filaments.

A

Tropomyosin and Troponin.

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26
Q

What is the function and structure of Tropomyosin?

A

Thread-like molecules that lie end to end alongside the groove of actin spiral covering actin sites blocking interaction that leads to muscle contraction

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27
Q

What are Troponin three polypeptide units?

A

Troponin C, troponin I and troponin T

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28
Q

What is the role of Troponin?

A

Troponin stabilizes tropomyosin in blocking position over actin’s cross-bridge binding sites. When Ca2+ binds to troponin, tropomyosin moves away from blocking position. With tropomyosin out of way, actin and myosin bind, interact at cross-bridges. Muscle contraction results.

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29
Q

What is the effect of contraction on the sarcomere’s structure?

A

Thin filaments slide inward over stationary thick filaments toward middle of A band during contraction. As they slide inwards pull Z lines closer together.
All sarcomeres throughout muscle fiber’s length shorten simultaneously. Contraction is accomplished by thin filaments from opposite sides of each sarcomere sliding closer together between thick filaments.

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30
Q

The influx of which ion initiates contraction and where is it released from?

A

Ca2+ from the sacroplasmic reticulum

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31
Q

During the start of contraction, towards what does the myosin head swivel to?

A

Centre of Sarcomere

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32
Q

What does the binding of ATP to myosin cause?

A

It causes myosin to detach from actin.

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33
Q

What does the hydrolysis of ATP on myosin cause?

A

Transfer of energy to myosin head and reorients it.

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34
Q

What is needs for contraction to continue?

A

ATP needs to be avaliable and Ca2+ levels need to be high in sarcoplasm.

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35
Q

Name the two membranous structures in fibres that are important in linking excitation to contraction.

A

Sarcoplasmic reticulum and transverse tubules.

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36
Q

What is the structure of Sarcoplasmic Reticulum?

A

It consists of fine network of interconnected compartments surrounding each myofibril. Segments wrapped around each A band and each i band.

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37
Q

Describe the structure of T tubules.

A

Membranous perpendicular extensions of surface membrane run from surface of muscle cell membrane into central portions of the muscle fibre. Since membrane is continuous with surface membrane – action potential on surface membrane also spreads down into T-tubule.

38
Q

What does the spread of an action potential down a T tubule trigger?

A

Release of Ca2+ from sarcoplasmic reticulum into cytosol

39
Q

What is the function of Dihydropyridine receptors?

A

At rest, they block the Ca2+ channel preventing movement of Ca2+. At depolarisation, they move and let Ca2+ into cytosol.

40
Q

Define a Muscle.

A

A group of fibres bundled together and attached to bones.

41
Q

Which tissue covers muscle and divids it internally into bundles?

A

Connective Tissue

42
Q

What are tendons?

A

They attach muscle to bone.

43
Q

What two primary factors can be adjusted to accomplish gradation of whole-muscle tension?

A

Number of muscle fibres contracting within a muscle and tension developed by each contracting fibre.

44
Q

What sort of movement is produced from muscles that have fewer fibres per motor unit.

A

Produce Precise, Delicate movement.

45
Q

What does Asynchronous recruitment of motor units help?

A

it helps delay or prevent fatigue

46
Q

List the 4 factors influencing extent to which tension can be developed.

A

Frequency of stimulation, length of fibre at onset of contraction, extent of fatigue and, thickness of fibre.

47
Q

What is single twitch?

A

If a muscle fibre is restimulated after it has completely relaxed, the second twitch is the same magnitude as the first twitch.

48
Q

What is twitch summation?

A

If a muscle fibre is restimulated before it has completely relaxed, the second twitch is added on to the first twitch, resulting in summation

49
Q

What is tetanus?

A

If a muscle fibre is stimulated so rapidly that it doesn’t have an opportunity to relax at all between stimuli, a maximal sustained contraction known as tetanus occurs.

50
Q

Name the two main types of contraction.

A

Isotonic (tension remains constant as muscle changes length - can be concentric or eccentric) and isometric (constant length)

51
Q

What is the equation for moments of a lever?

A

Force x Perpendicular Distance from the Pivot

52
Q

Name a energy storage molecule for contraction?

A

Creatine - synthesised in liver from amino acids and phosphorylated to give phophorylcreatine. During exercise, this reaction can be reversed to form ATP from ADP.

53
Q

Does sprinting involve mostly aerobic or anaerobic respiration?

A

Anaerobic

54
Q

What is the importance of muscle fatigue?

A

It is a defence mechanism to protect muscle from reaching a point at which it can’t continue to produce ATP.

55
Q

What is central fatigue?

A

Happens when CNS can’t adequately activate motor neurones to working muscles.

56
Q

What are the 3 types of muscle fibres?

A

Slow-oxidative, Fast-oxidative and Fast-glycolytic fibres.

57
Q

What are spindles?

A

Groups of specialised muscle fibres known as intrafusal fibres. Lie within spindle-shaped connective tissue capsules parallel to extrafusal fibres. Each spindle has its own private efferent and afferent nerve supply. Play key role in stretch reflex.

58
Q

What are the two types of smooth muscle?

A

Visceral and Multi-unit

59
Q

What is the structure of smooth muscle?

A

Lack visible cross-striations, spindle-shaped cells with single nucleus. Cells usually arranged in sheets within muscle. No Z lines present. No troponin and tropomyosin doesn’t block cross-bridge binding sites. Light chains of proteins are attached to head of myosin molecule, near neck region.

60
Q

Name the 3 types of filaments of Smooth Muscle.

A

Thick myosin, thin actin and medium-size filaments (part of cytoskeletal framework supporting cell’s shape)

61
Q

What needs to happen to myosin to allow it to interact with actin in smooth muscle?

A

Myosin can only interact with actin when myosin is phosphorylated.

62
Q

Describe the arrangement of smooth muscle filaments.

A

Thick and thin filaments are at sight diagonal from side to side in smooth muscle cell (diamond shaped lattice) Myosin molecules arranged in thick filaments so cross-bridges present along entire length.

63
Q

Describe the initiation of contraction in smooth muscles.

A

Ca2+ binds to calmodulin which activates a kinase enzyme. This phosphorylates myosin activating myosin ATP-ase and hence myosin can interact with actin.
(Myosin is dephorpshorylated by myosin light chain phosphatase)

64
Q

Is there a T tubule system in smooth muscle?

A

No

65
Q

Describe the structure and give an example of a multi-unit smooth muscle.

A

Neurogenic, made form multiple discrete units - function independently (no gap junctions). Units must be separately stimulated by nerves to contract. Examples: Large arteries, large airways to lungs, Iris, Hair follicles.

66
Q

Describe the structure and give an example of a single-unit smooth muscle.

A

No nervous stimulation (myogenic), excited and contract as single unit, gap junctions present, contraction slow and energy efficient. Examples: Found in walls of hollow viscera, GI tract, blood vessels, uterus.

67
Q

What does it mean by Phasic SM?

A

Single unit smooth muscle that contracts in bursts, triggered by action potential that lead to increased cytosolic Ca2+

68
Q

What does it mean bu Tonic SM?

A

Single unit smooth muscle that often partially contracted at all times (relatively low resting potential). Doesn’t show the bursts of activity of phasic SM but varies in increments above or below usual tonic state.

69
Q

What are the factors influencing smooth muscle contractile activity?

A

Spontaneous depolarisation of cells, Signalling molecules (NTs from autonomic neurons and hormones), local changes in extracellular fluid, and stretch

70
Q

Can smooth muscle continue to develop tension even when considerably stretched?

A

Yes - Stress Relaxation Response.

71
Q

Describe the structure of cardiac muscle.

A

Found in walls of heart, similar striations to skeletal muscle. Fibres joined in branching network, Z-lines present. Cells joined at intercalated discs. Gap Junctions between cells, T tubule system and innervated by autonomic nervous system.

72
Q

What is the resting potential of cardiac muscle?

A

-90mV

73
Q

Does cardiac muscle fibres act as multiple units?

A

No, it is just one unit.

74
Q

What causes depolarisation in cardiac muscle?

A

Rapid movement of Na+ into muscle cells increasing the potential to +30mV

75
Q

What controls firing rate of cardiac muscle?

A

Sympathetic and parasympathetic nervous systems

76
Q

What is the threshold potential for cardiac muscle?

A

-70mV

77
Q

What causes repolarisation of cardiac muscles?

A

Fast flow of K+ out of cells.

78
Q

How long is plateau phase?

A

250ms

79
Q

What causes depolarisation of pacemaker cells?

A

Influx of Ca2+

80
Q

What causes repolarisation of pacemaker cells?

A

Movement of K+ out of cell

81
Q

What happens during prepotential?

A

Slow influx of Ca2+

82
Q

What is the resting potential, threshold potential and max potential of pacemaker cells?

A

Resting: -60mV
Threshold: -40mV
Max: 0mV

83
Q

How many beat/min are produced by SAN?

A

100-110beats/min

84
Q

What controls heart rate normally?

A

SAN

85
Q

If SAN loses function, what takes over the control of heart beat?

A

AVN

86
Q

What takes over if both SAN and AVN fail?

A

Purkinje Fibres

87
Q

What is the function of the plateau phase?

A

Prevents tetanus and summation.

88
Q

Does heart show plasticity?

A

Yes e.g. athetes heart can grow to allow more blood to be pumped through per pump.

89
Q

Name a muscle pathology

A

Myasthenia gravis, muscular dystrophy and natural wear and tear.

90
Q

Does a monosynaptic reflex involve the brain?

A

No (only one synapse)

91
Q

Give an example of monosynaptic stretch reflex.

A

Patellar reflex (leg jolt)

92
Q

List the dangers of steroids.

A

Stunted growth, hair changes, hypogonadism, roid rage, increased BP and LDL-cholesterol, liver toxicity, Increased risk of heart attack/stroke
DEATH

Year 1 Animal Physiology (9 decks)

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