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BDS1 > Muscle > Flashcards

Muscle Flashcards

1
Q

What are the 4 tissue types?

A

Epithelial, connective, nervous, muscle

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2
Q

What are the 3 types of muscle?

A

Skeletal, cardiac, smooth

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3
Q

Function of skeletal muscle

A

contract to produce movement of skeleton (attached to bone)

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4
Q

Function of cardiac muscle

A

Movement/Pumping of blood through cardiovascular system

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5
Q

Function of smooth muscle

A

movement of substance through visceral, hollow organs

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6
Q

What are the 3 ways of classifying muscle?

A
  • by the way it is controlled whether it is the somatic (voluntary) or autonomic (involuntary) NS
  • structure (striated or not)
  • Muscle type - cardiac, skeletal, smooth
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7
Q

When can skeletal muscle contraction be subconscious?

A

For maintaining posture/balance

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8
Q

What is an alternative name for skeletal muscle cells?

A

Fibres

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9
Q

Structure of muscle fibres

A

elongated, cylindrical, multinucleated cells containing myofibrils made of repeating units of myofilaments

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10
Q

Where are the nuclei located in a muscle fibre?

A

Around peripheral edge (no space else where)

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11
Q

Why is an individual skeletal muscle an organ?

A

Composed of multiple tissue types. Mainly skeletal muscle tissue but also nervous tissue, blood vessels, connective tissues.

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12
Q

What is the name of the dense irregular connective tissue encasing each muscle?

A

Epimysium

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13
Q

Function of the epimysium

A

Separates muscle from other tissues and organs

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14
Q

How is muscle tissue arranged?

A

Arranged into bundles (fascicles) of muscle fibres

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15
Q

What is the name of a bundle in skeletal muscle?

A

Fascicle (pl. fasciculi)

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16
Q

What is the perimysium?

A

Loose connective tissue that encases each fascicle

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17
Q

What is the name of the loose connective tissue that encases each muscle fibre?

A

Endomysium

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18
Q

Function of endomysium

A

Separates individual muscle fibres from their neighbours

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19
Q

Function of tendon

A

Helps to transfer the force of the muscle contraction to bone

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20
Q

What is a tendon formed from?

A

The epimysium, perimysium and endomysium come together at the tapered end of a muscle to form a tendon. Gives a very strong attachment to bone

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21
Q

Where do blood vessels and nerves exist in skeletal muscle?

A

Spread through connective tissue (epimysium, perimysium, endomysium). Each muscle fibre has its own blood supply.

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22
Q

What feature gives the striated appearance in skeletal muscle?

A

The arrangement of the numerous myofibrils which have a repeating pattern of myosin and actin (myofilaments)

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23
Q

What are myofibrils?

A

Tubular structures that make up the majority of muscle fibres. Myofibrils are composed of repeating protein units called myofilaments (actin and myosin)

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24
Q

What are the two types of myofilaments?

A

Actin and myosin

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25
Q

What is the cytoskeleton present in all cells formed from?

A

Actin and myosin (different arrangement in muscle fibres - specialised for contraction)

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26
Q

What is actin?

A

Thin myofilament that forms light bands

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27
Q

What is myosin?

A

Thick myofilament that forms dark bands

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28
Q

How are myofibrils divided into sarcomeres?

A

By Z lines which bisect the light bands (actin anchored to Z lines)

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29
Q

What are sarcomeres?

A

The contractile units of skeletal muscle

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30
Q

How does muscle contract?

A

When the muscle fibre is excited, actin slides over myosin by the sliding filament model causing the shortening of the sarcomeres and therefore the myofibril shortens.

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31
Q

What is the I band composed of?

A

Actin filaments only. Bisected by Z line

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32
Q

What is the A band composed of?

A

Myosin and overlapping actin filaments

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33
Q

What is the H band composed of?

A

Myosin filaments only

34
Q

What is the name of the mechanism that causes sarcomeres to contract?

A

Sliding filament mechanism

35
Q

What happens to a sarcomere when the muscle fibre contracts?

A

I bands shorten, H bands shorten, A bands stay constant, more overlapping of myosin and actin, Z lines move closer together.

36
Q

Which neurones innervate skeletal muscle fibres?

A

Somatic motor neurones

37
Q

What is a motor unit?

A

A single motor neurone together with all the muscle fibres it innervates.

38
Q

What is a neuromuscular junction?

A

The synapse which connects a motor neurone and muscle fibre

39
Q

What is excitation-contraction coupling?

A

the transduction of an action potential to a muscle contraction

40
Q

What are the steps of excitation-contraction coupling?

A
  1. action potential in motor neurone converted to acetylcholine at neuromuscular junction
  2. detected by receptors on sarcolemma
  3. depolarisation (Na+ influx) spreads down T tubules to SR triggering an action potential in muscle fibres
  4. Ca2+ released from SR and binds to troponin
  5. contraction
41
Q

What is the sarcolemma?

A

the plasma membrane of skeletal muscle cells

42
Q

What are T-tubules

A

Invaginations of the sarcolemma into the sarcoplasm which wrap around myofibrils and are continuous with the extracellular space

43
Q

What is the sarcoplasmic reticulum?

A

modified smooth endoplasmic reticulum that stores concentrated Ca2+ (when muscle fibre relaxed)

44
Q

What is the function of T-tubules and the sarcoplasmic reticulum?

A

Support synchronous contraction of sarcomeres

45
Q

What are special adaptation of muscle fibres?

A

Modified sarcolemma with pores and T tubules. Modified sarcoplasmic reticulum. Arrangement of myofilaments (actin and myosin) in myofibrils.

46
Q

Where is cardiac muscle found?

A

Only in the heart

47
Q

Which branch of the nervous system controls cardiac muscle?

A

Autonomic

48
Q

Structure of cardiac muscle cells (cardiomyocytes)

A

Striated, elongated, branched, cylindrical cells with 1-2 nuclei.

49
Q

Why is cardiac muscle striated?

A

Similar arrangement of myofibrils as skeletal muscle.

50
Q

What are the 3 layers of the heart wall?

A

Pericardium, myocardium, endocardium

51
Q

What is the pericardium?

A

The outer supporting fibrous connective tissue layer of the heart wall

52
Q

What is the myocardium?

A

The (thick) layer of cardiac muscle tissue

53
Q

What is the endocardium?

A

Inner, single layer of endothelial cells

54
Q

By what name is the endocardium known as in the rest of the cardiovascular system?

A

Endothelium

55
Q

What is the name of cardiac muscle cells?

A

Cardiomyocytes

56
Q

Which type of connective tissue supports the rich capillary network in the cardiac muscle?

A

Reticular connective tissue

57
Q

What are intercalated disks?

A

specialised intercellular junctions containing desmosomes and gap junctions that allow depolarisation to spread through cardiomyocytes.

58
Q

What is the function of gap junctions?

A

Allow ions and signals to pass freely between cells

59
Q

Similarities between cardiac and skeletal muscle

A

sarcomeres, T-tubules, sarcoplasmic reticulum, numerous mitochondria, glycogen and lipid granules (energy), contraction via sliding-filament mechanism

60
Q

What is the name of the specialised cardiac muscle cells that initiate and distribute contractions to cardiomyocytes?

A

The conducting system

61
Q

What is meant by cardiac muscle cells acting as a syncytium?

A

All cells work in a single unit due to connection via intercalated disks

62
Q

Differences between skeletal and cardiac muscle

A
  • cardiac muscle is under autonomic control while skeletal muscle is under somatic control
  • in cardiac muscle, Ca2+ leaks slowly from SR
  • skeletal muscle doesn’t have conducting system, instead each fibre is innervated by motor neurone
  • intercalated disks
63
Q

How do the cells in the SAN set the basic heart rhythm?

A

Pacemaker cells undergo spontaneous depolarisation due to slow leaking of Ca2+ from SR

64
Q

What is the sequence of the conducting system of the heart?

A
  • initiated by pacemaker cells in sinoatrial node
  • contraction of LA and RA
  • depolarisation reaches atrioventricular node
  • travels to atrioventricular Bundle of His
  • to Purkinje fibres
  • relayed to cardiac muscle fibres
  • cardiomyocytes contract
65
Q

How is the rate of the inherent heart rhythm modulated?

A

Autonomic nervous stimulation and hormonal stimulation

66
Q

Where is smooth muscle located?

A

Lining hollow, visceral organs

67
Q

Function of smooth muscle

A

to propel lumen contents e.g. bolus in peristalsis

68
Q

Structure of smooth muscle cell - shape, nuclei, striation

A

elongated, spindle-shaped cells with tapered ends. Single centrally located nuclei. Non-striated (no sarcomeres)

69
Q

Layers of the oesophagus

A

epithelium, lamina propria, muscularis mucosae, submucosa, muscularis propria (inner circular layer, outer longitudinal layer), adventitia

70
Q

What is the name of the two layers of smooth muscle surrounding the submucosa in the oesophagus?

A

Muscularis propria (inner circular, outer longitudinal)

71
Q

Why are the 2 layers of muscularis propria at right angles?

A

The inner layer constricts the lumen while the outer layer shortens the tract length - specialised for peristalsis

72
Q

Where is the parasympathetic ganglia located in the oesophagus?

A

Between the 2 layers of smooth muscle making up the muscularis propria

73
Q

Function of the parasympathetic NS on the oesophagus

A

Regulates intensity of peristalsis

74
Q

How are actin and myosin arranged in smooth muscle cells?

A

Criss-cross lattice

75
Q

How is actin anchored to the cytoplasm and cell membrane of smooth muscle cells?

A

Via dense bodies

76
Q

Function of dense bodies

A

Attach adjacent smooth muscle cells together to transmit the contractile forces through the tissue. Anchor actin to cytoplasm and plasma membrane.

77
Q

Location of myosin in smooth muscle cell

A

Distributed throughout cytoplasm

78
Q

What is desmin?

A

An intermediate filament found in smooth muscle cells that help to anchor actin and allow myosin to slide over it which is aided by dense bodies

79
Q

How does a smooth muscle cell change shape when contracted?

A

Elongated -> shortened and globular

80
Q

How does smooth muscle differ in speed of contraction and energy consumption compared to skeletal and cardiac muscle.

A

Contract more slowly. Uses less energy

BDS1 (24 decks)

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