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Human Anatomy & Kinanthropometry > Week 2 - Muscle > Flashcards

Week 2 - Muscle Flashcards

1
Q

Microscopic appearance of SKELETAL muscle

A

Long cylindrical fibre

Many peripherally located nuclei

Unbranched

Striated

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2
Q

Microscopic appearance of SMOOTH muscle

A

Fibre thickest in middle

Tapered at each end

1 centrally positioned nucleus

Not striated

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3
Q

Microscopic appearance of CARDIAC muscle

A

Branched

Cylindrical fibre

1 centrally located nucleus

Interacalated discs join neighbouring fibres

Striated

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4
Q

Fibre diameter for skeletal muscle

A

Very large

10-100 micrometers

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5
Q

Fibre diameter for cardiac muscle

A

Large

10-20 micrometers

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6
Q

Fibre diameter for smooth muscle

A

Small

3-8 micrometers

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7
Q

Connective tissue components for skeletal muscle

A

Endomysium

Perimysium

Epimysium

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8
Q

Connective tissue components for cardiac muscle

A

Endomysium

Perimysium

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9
Q

Connective tissue components for smooth muscle

A

Endomysium

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10
Q

Which muscle types have contractile proteins organised into sarcomeres?

A

Skeletal

Cardiac

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11
Q

Sarcoplasmic reticulum for muscle types

A

Skeletal - Abundant

Cardiac - Some

Smooth - Very little

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12
Q

Which muscle fibre type doesn’t have T tubules?

A

Smooth muscle

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13
Q

Where is the source of Ca2+ for contraction in skeletal muscle?

A

Sarcoplasmic reticulum

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14
Q

Where is the source of Ca2+ for contraction in cardiac muscle?

A

Sarcoplasmic reticulum

+

Interstitial fluid

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15
Q

Where is the source of Ca2+ for contraction in smooth muscle?

A

Sarcoplasmic reticulum + interstitial fluid

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16
Q

What are the regulator proteins for contraction in each of the muscle types?

A

Skeletal - Troponin + tropomyosin

Cardiac - Troponin + tropomyosin

Smooth - Calmodulin + myosin light chain kinase.

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17
Q

Contraction regulation for skeletal muscle

A

Acetylcholine released by somatic motor neurones

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18
Q

Contraction regulation for cardiac + smooth muscle

A

Acetylcholine + norepinephrine released by autonomic motor neurones

+ several hormones

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19
Q

Define the origin point

A

Proximal attachment that usually remains stationary during contractions

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20
Q

Define the insertion point

A

Distal attachment that usually moves towards the other during contraction.

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21
Q

Define myology

A

Scientific study of muscles

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22
Q

What are the functions of muscular tissue

A

Producing body movements

Stabilising body positions

Storing + moving substances w/in the body

Generating heat.

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23
Q

FUNCTIONS OF MUSCULAR TISSUE

Explain stabilising body positions

A

Skeletal muscle contractions stabilise joints + maintain body positions.

Postural muscles contract continuously when you are awake.

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24
Q

FUNCTIONS OF MUSCULAR TISSUE

Explain Storing + moving substances w/in the body

A

Storage is accomplished by sustained contractions of sphincters.

Temporary storage of food in stomach or urine in urinary bladder is possible due to smooth muscle sphincters closing off the outlets of these organs.

Cardiac muscle contractions of the heart pump blood through the bv of the body.

Contraction + relaxation of smooth muscle in the walls of bv help adjust bv diameter = regulating the rate of blood flow.

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25
Q

FUNCTIONS OF MUSCULAR TISSUE

Explain Generating heat.

A

As muscular tissue contracts, it prod. Heat = thermogenesis.

Involuntary contractions of skeletal muscles, shivering, can ⬆️ rate of heat prod.

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26
Q

What 4 properties enable muscular tissue to function + contribute to homeostasis

A

Electrical excitability

Contractility

Extensibility

Elasticity

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27
Q

Define electrical excitability

A

= Ability to prod APs when responding to certain stimuli.

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28
Q

What are the 2 main types of stimuli that trigger APs?

A

Autorythmic electrical signals arising in the muscular tissue itself

Chemical stimuli i.e neurotransmitters, hormones or even local changes in pH.

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29
Q

Define contractibility

A

Ability of muscular tissue to contract forcefully when stimulated by an AP.

Contraction = generates tension while pulling on its attachment points.

If this is great enough to overcome the resistance of the object, the muscle shortens + movement occurs.

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30
Q

Extensibility

A

Ability of muscular tissue to stretch (w/in limits) w.out being damaged.

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31
Q

Elasticity

A

Ability of muscular tissue to return to its original length + shape after contraction or extension.

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32
Q

Subcutaneous layer / hypodermis

A

Separates muscle from skin

Composed of:

  • areolar connective tissue
  • adipose tissue.
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33
Q

What is the purpose of the Subcutaneous layer / hypodermis

A

Pathway for nerves, bv + lymphatic vessels to enter + exit muscles.

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34
Q

What does the adipose tissue in the Subcutaneous layer / hypodermis store + do?

A

Most bodys TG

Serves as an insulating layer

Protects muscles from physical trauma.

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35
Q

Describe the fascia

A

Dense sheet of irregular connective tissue

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36
Q

What does the fascia allow?

A

free movement of muscles

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37
Q

What are the 3 layers of connective tissue extending from the fascia to protect + strengthen skeletal muscle

A

Epimysium

Perimysium

Endomysium

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38
Q

Epimysium

A

Outer layer, consists of dense irregular connective tissue

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39
Q

Perimysium

A

Sheath of connective tissue surrounding a bundle of muscle fibres.

40
Q

Endomysium

A

Penetrates the interior of each fascicle + separates each muscle fibre from 1 another.

41
Q

What accompanies each nerve that penetrates a skeletal muscle?

A

Generally an artery + 1 or 2 veins

42
Q

Somatic motor neurones

A

Neurones that stimulate skeletal muscle to contract.

Axon extends from brain or spinal cord to a group of skeletal muscle fibres.

43
Q

Sarcolemma

A

Plasma membrane of a muscle cell.

44
Q

Describe Transverse (T) tubules

A

Invaginations in the sarcolemma that tunnel in towards the centre of each muscle fibre.

——Muscle AP travels along sarcolemma + through T tubules, quickly spreading throughout the muscle fibre. —

45
Q

What are T tubules filled with?

A

Interstitial fluid due to being open to the outside of the fibre.

46
Q

What is the sarcoplasm?

What does it contain?

A

Cytoplasm of a muscle fibre.

Glycogen + myoglobin

47
Q

Myoglobin

A

Muscle protein that binds to O2.

Releases O2 when needed by the mit. For ATP prod.

48
Q

Myofibrils

A

Contractile organelles of skeletal muscle.

About 2 micrometers in diameter

Extend the entire length of a muscle fibre.

49
Q

Sarcoplasmic reticulum (SR)

A

Fluid-filled system of membranous sacs that encircle each myofibril.

50
Q

What are terminal cisterns?

What do they store? When do they release it?

A

Part of the SR.

Store Ca2+

Release when an AP travels down T tubules.

51
Q

Thin filaments

A

8nm in diameter

1-2 micrometers long

Composed of Actin.

52
Q

Thick filaments

A

16nm in diameter

1-2 micrometers long

Composed of Myosin.

53
Q

Z discs

A

Narrow, plate-shaped regions of dense protein material.

Separate sarcomeres.

54
Q

A band

A

Darker middle part of a sarcomere, extends the entire length of the thick filaments.

55
Q

I band

A

Thin filaments only

Z-disc passes through the centre of each I band.

56
Q

H zone

A

Centre of each A band containing only thick filaments.

57
Q

M line

A

Region in the centre of H zone that contains proteins holding thick filaments together at centre of sarcomere.

58
Q

What are the 3 kinds of proteins in myofibrils?

A

Contractile

Regulatory

Structural

59
Q

Regulatory muscle proteins

A

Help switch the contraction process on + off

60
Q

What are the 2 types of contractile proteins

A

Myosin

Actin

61
Q

What are the 2 binding sites on each myosin head?

A

Actin-binding site

ATP-binding site. (Also functions as an ATPase).

62
Q

Motor proteins

A

Pull various cellular structures to achieve movement by converting chemical energy in ATP —> mechanical energy of motion = prod. force.

63
Q

Describe relaxed muscle + myosin relation

A

Tropomyosin covers myosin binding sites on actin so myosin can’t bind to it.

64
Q

What happens when Ca2+ ions bind to troponin?

A

Troponin undergoes a conformational change = moves tropomyosin AWAY from myosin-binding sites on actin + contraction begins as myosin binds to actin.

65
Q

What happens to the width of A band during contraction?

A

Remains unchanged

66
Q

What happens to the ind. lengths of thick + thin filaments during contraction?

A

Remain unchanged.

67
Q

What happens at the onset of muscle contraction?

A

SR releases Ca2+ into sarcoplasm.

Ca2+ binds to troponin.

68
Q

What are the 4 stages of the contraction cycle in the sliding filament theory?

A
  1. ATP Hydrolysis
  2. Attachment of myosin to actin
  3. Power stroke
  4. Detachment of myosin from actin
69
Q

What is excitation-contraction coupling

A

Seq. of events that links excitation to contraction.

70
Q

Where does excitation-contraction coupling occur?

A

At the triads of the skeletal muscle fibre.

71
Q

Define triad

A

Consists of a T tubule + 2 opposing terminal cisterns of the SR.

72
Q

Whats at a triad?

A

T tubule + terminal cisterns mechanically linked together by 2 groups of integral membrane proteins.

73
Q

TRIAD

What are the 2 groups of integral membrane proteins?

A

Voltage gated Ca2+ channels

Ca2+ release channels

74
Q

Voltage gated Ca2+ channels

A

Located in the T tubule membrane.

Arranged as tetrads.

Main role - to serves as voltage sensors that trigger the opening of the Ca2+ release channels.

75
Q

Where are Ca2+ release channels

A

In terminal cisternal membrane of SR.

76
Q

What happens to the Ca2+ release channels when a skeletal muscle fibre is at REST

A

Part extended into sarcoplasm is blocked by a cluster of voltage-gated Ca2+ channels.

= Preventing Ca2+ from leaving the SR.

77
Q

What happens to the Ca2+ release channels when a skeletal muscle fibre is EXCITED

A

An AP travels along T tubule, voltage-gates Ca2+ channels detect the change in voltage + undergo conformational change.

= Ca2+ release channels open.

78
Q

What happens once Ca2+ release channels are open?

A

Lots of Ca2+ flow from SR —> sarcoplasm around thick + thin filaments.

== Ca2+ conc. in sarcoplasm ⬆️.

Ca2+ combines w/ troponin to undergo conformational change = tropomyosin moves away from the myosin-binding sites on actin.

Once binding sites are free, myosin heads bind to them to form cross-bridges + muscle fibres contract.

79
Q

Terminal cisternal membranes of the SR also contain Ca2+ + ATPase pumps, what do they do?

A

Use ATP to constantly transport Ca2+ from sarcoplasm into the SR.

80
Q

What happens after last AP has propagated through the T tubules?

A

Ca2+ release channels close

81
Q

What does the length-tension relationship indicate?

A

That the forcefulness of muscle contraction depends on the length of the sarcomeres w/in a muscle before contraction begins.

As the sarcomeres of a muscle fibre are stretched to a longer length, the zone of overlap shortens + fewer myosin heads can make contact w. thin filaments.

So, the tension the fibre prod. ⬇️.

82
Q

What happens when a fibre is stretched to 170% of its optimal length?

A

No overlap between the thick + thin filaments.

= No contraction as none of the myosin heads can bind to the think filaments so the tension is 0.

83
Q

What are the types of muscle fibre/fascicle arrangement

A

Parallel

Fusiform

Circular/orbital

Triangular

Pennate

84
Q

Parallel muscle fibre arrangement

A

Fibres run in straight line from origin to insertion.

Typically quite flat in shape.

85
Q

Fusiform muscle fibre arrangement

A

Muscle belly has a bulbous shape to it.

Considered as a subcategory to parallel as fibres run from origin to insertion points.

86
Q

Circular/orbital muscle fibre arrangement

A

Fibres run in a circular direction.

87
Q

Triangular muscle fibre arrangement

A

One end of muscle comes into single focal point but other end is quite broad.

Fibres fan out to create triangular shape.

88
Q

What are the types of Pennate muscle fibre arrangement

A

Uni

Bi

Multi

89
Q

Which muscle type is subject to the greatest amount of stretching?

A

Smooth muscle

90
Q

What in the muscle limits the range of extensibility + keeps it w/in the contractile range of muscle cells?

A

The connective tissue

91
Q

What does the fascia do?

A

Supports + surrounds muscles + other organs of the body.

Carries nerves, bv + lymphatic vessels + fills spaces between muscles

92
Q

What can T tubules ensure?

A

That an AP excites ALL parts of muscle fibre simultaneously

93
Q

Uni pennate muscle fibres

A

Fibres run at angle to midline of muscle + all in 1 direction.

94
Q

Bi pennate muscle fibres

A

Has central tendon running through middle of muscle.

Fibres converge from either side onto the middle of the muscle. - 2 direction in which muscle fibres run.

95
Q

Multi pennate muscle fibres

A

Fibres converge into centre of muscle from different directions.

Human Anatomy & Kinanthropometry (27 decks)

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