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[AMS] Fundamentals of Body Structure > BL - Muscle > Flashcards

BL - Muscle Flashcards

1
Q

What is the prefix used to denote muscle?

A

“My-“ eg myalgia, myasthenia

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2
Q

What is the prefix used to denote a components of a muscle?

A

“Sarco-“ eg sarcolemma

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3
Q

What are the three major categories of muscle?

A

Skeletal (striated), cardiac (striated), smooth (non-striated).

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4
Q

What are the three types of skeletal muscle fibre?

A

Red, intermediate and white.

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5
Q

Which type of skeletal muscle fibre is the largest?

A

White, then intermediate, then red is the smallest.

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6
Q

Give some differences between red and white muscle fibres.

A

Red have rich vascularisation and myoglobin content, numerous mitochondria, slow/weak contraction and fatigue slowly. White is opposite. Intermediate is intermediate.

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7
Q

Which type of skeletal muscle has more neuromuscular junctions?

A

White

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8
Q

What is the difference in enzyme content between red and white muscles?

A

Red is rich in oxidative enzymes and poor in ATPase, white is poor in oxidative enzymes but rich in ATP-ase.

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9
Q

What is myoglobin?

A

Red protein containing haem which functions as an oxygen storing molecule. Structurally similar to haemoglobin subunit.

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10
Q

Which muscle types contain myoglobin?

A

Skeletal and cardiac - not smooth.

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11
Q

What conditions make haemoglobin more likely to give up oxygen to myoglobin?

A

Low pH - active muscles produce CO2 which dissolves and lowers pH, causing oxygen to be transferred.

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12
Q

What is a perimysium?

A

Connective tissue carrying nerves and blood vessels that surrounds a fascicle.

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13
Q

What is the plasmalemma of a muscle cell called?

A

Plasmalemma

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14
Q

What is it known as when muscles are destroyed?

A

Atrophy

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15
Q

What is it known as when muscles are remodelled?

A

Hypertrophy

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16
Q

How and when would disuse atrophy occur?

A

Loss of protein leads to reduced fibre diameter and loss of power. Occurs due to bed rest, limb immobilisation, sedentary behaviour.

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17
Q

Give two reasons other than disuse for atrophy to occur.

A

Age and denervation.

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18
Q

How does hypertrophy lead to increase in muscle size?

A

More contractile proteins, so increase in fibre diameter.

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19
Q

Gove some examples of metabolic changes that occur due to hypertrophy?

A

Increased enzyme activity for glycolysis, more mitochondria, more stored glycogen, increased blood flow.

20
Q

True or false - muscle length is increased by frequent stretching?

A

True, due to addition of sarcomeres. The converse is also true.

21
Q

What are the thin muscle filaments called?

A

Actin

22
Q

What are the thick muscle filaments called?

A

Myosin

23
Q

What are skeletal muscles composed of?

A

Fascicles -> muscle fibres (cells) -> myofibrils -> myofilaments (actin and myosin)

24
Q

What can a troponin assay be used for?

A

Can be measured as a marker for cardiac ischaemia, as is released from ischaemic cardiac muscle within an hour. Must measure within 20 hours.

25
Q

What is creatine kinase?

A

An enzyme released into the blood by damaged skeletal muscle and brain.

26
Q

What is the role of calcium in muscle contraction?

A

Increased amounts of ionic calcium bind to troponin causing a conformational change which moves tropomyosin away from actin’s binding sites, so binding can begin.

27
Q

Describe the sequence of muscle contraction

A
  • myosin cross bridge attaches to actin myofilament
  • myosin head pivots and bends as it pulls the actin filament, sliding it towards the M line
  • new ATP attaches to myosin head, cross bridge detaches
  • ATP splits to ADP and Pi causing myosin head to cock.
28
Q

Summarise events leading to contraction of skeletal muscle.

A
  • nerve impulse arrives an NM junction and stimulates release of Ach causing depolarisation
  • Na+ enters cell and T tubules are depolarised, causing conformation change.
  • Ca2+ enters sarcoplasm from terminal cisternae and binds to TnC subunit of troponin.
  • Contraction occurs.
29
Q

A picture of muscle in LS shows striations, centrally positioned nuclei, intercalated discs and branching. What type of muscle is it?

A

Cardiac

30
Q

What is the difference between the tubule placement in skeletal muscle compared with cardiac muscle?

A

In skeletal muscle they are on the Z bands rather than with the A-I bad junction.

31
Q

What are the two ways that muscles can increase in size?

A

Hypertrophy (enlargement of individual cells) or hyperplasia (multiplication of cells)

32
Q

What is a heart muscle cell also known as?

A

A cardiomyocyte

33
Q

What are natriuretic peptides?

A

Peptide hormones synthesised by the heart, brain and other organs. Their release is often stimulated by heart failure. Their function is to reduce arterial pressure.

34
Q

How do natriuretic peptides reduce arterial pressure?

A

Decreasing blood volume and systemic vascular resistance.

35
Q

When might a patient have elevated levels of ANP?

A

Hypervolemic states which occur in congestive heart failure.

36
Q

What can BNP and NT-pro-BNP be used for?

A

They are sensitive, diagnostic markers for heart failure in patients.

37
Q

What is the function of Purkinje fibres?

A

They transmit action potentials to the ventricles from the atrioventricular node.

38
Q

Give some features of Purkinje fibres.

A

Large cells with abundant glycogen, sparse myofilaments and extensive gap junction sites

39
Q

True or false - smooth muscle does not contain T tubules?

A

True, it also does not contain sarcomeres. It is not striated so no banding is present.

40
Q

What are myoepithelial cells?

A

Stellate cells forming a network around secretory units of exocrine glands, where they contract to aid secretion.

41
Q

What is the function of myofibroblasts?

A

Produce collagenous matrix at wound healing sites and contract to draw wound together.

42
Q

Can cardiac muscle be repaired?

A

No, following damage fibroblasts lay down scar tissue

43
Q

Can skeletal muscle cells repair themselves?

A

They cannot divide but tissue can regenerate using mitosis in satellite cells, which can also fuse with existing muscle cells to increase mass.

44
Q

Can smooth muscle regenerate?

A

Yes - smooth muscle cells retain their mitotic activity and can form new smooth muscle cells.

45
Q

Give some examples of diseases caused by smooth muscle dysfunction.

A

Asthma, irritable bowel syndrome, primary hypertension, detrusor instability

46
Q

What are the three indicators of muscle injury?

A

Creatine kinase , myoglobinuria, troponin

47
Q

What is the significance of “fixed” mottling?

A

It does not change when pressed, so the change is irreversible

[AMS] Fundamentals of Body Structure (19 decks)

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