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Body Logistics > Muscle > Flashcards

Muscle Flashcards

1
Q

What shape is smooth muscle?

A

Spindle-shaped (thinner at the ends and fatter in the middle)

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2
Q

List the 3 skeletal muscle types.

A

Red
White
Intermediate

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3
Q

Do red or white fibres have a wider diameter in skeletal muscle?

A

White fibres

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4
Q

How many subunits does myoglobin have?

A

1 subunit

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5
Q

What type(s) of muscle is myoglobin present in?

A

Skeletal muscle
Cardiac muscle
(Not smooth muscle)

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6
Q

What enzymes are apparent in white muscle fibres? How does this compare to red muscle fibres?

A

In red muscle fibres there are high amounts oxidative enzymesof but a low amount of ATPases. The opposite is true in white muscle fibres; there are low amounts of oxidative enzymes, but high amounts of ATPases

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7
Q

Describe the vascularisation, myoglobin count, mitochondria count, and rate of contraction in red muscle fibres and white muscle fibres.

A

Red muscle fibres are highly vascularised, have high amounts of myoglobin, high amounts of mitochondria, and contract at a much slower/weaker rate.
Conversely, white muscle fibres are poorly vascularised, have low amounts of myoglobin, low amounts of mitochondria, and contract at a much higher/stronger rate.

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8
Q

Do white muscle fibres fatigue more slowly or quickly in comparison to red muscle fibres?

A

White muscle fibres fatigue more quickly than red muscle fibres

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9
Q

What is the perimysium?

A

Connective tissue that surrounds fascicles of muscle fibres, that contain nerves and blood vessels

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10
Q

Which subunit of troponin does Ca2+ bind?

A

TnC

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11
Q

What is the sarcolemma?

A

The plasma membrane of a muscle cell

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12
Q

What is the A band? What is the I band?

A

The A band is the area composed of the length of the myosin filament - the I band is the area where actin filament is not overlapped by any myosin filament

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13
Q

When does disuse atrophy occur?

A

When a muscle is used less than previously, causing it to atrophy (decrease in size)

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14
Q

What neurotransmitter is used at the neuromuscular junction? On what surface do they bind receptors?

A

Acetylcholine, on the surface of the sarcolemma

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15
Q

Where abouts are nuclei positioned in cardiac muscle fibres? How does this differ in skeletal muscle fibres?

A

In cardiac muscle cells nuclei are positioned centrally - this is different to skeletal muscle cells where they are positioned peripherally

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16
Q

What promotes the dissociation of O2 from haemoglobin/myoglobin?

A

Respiration produces carbonic acid (or lactic acid in anaerobic respiration) which decreases the pH of the surrounding tissue - these acidic conditions promote dissociation of O2

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17
Q

What is the difference between hypertrophy and hyperplasia?

A

Hypertrophy is the enlargement of a singular cell, while hyperplasia is the multiplication of a cell

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18
Q

Define myalgia, myasthenia, and myoclonus.

A

Myalgia - muscle pain
Myasthenia - muscle weakness
Myoclonus - sudden spasm of the muscle

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19
Q

What is the function of ANP and BNP?

A

They are released by the heart to reduce blood volume in order to reduce high blood pressure putting considerable strain on the heart

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20
Q

What is a sarcomere?

A

The basic unit of striated muscle tissue

21
Q

What is the difference between cardiac and skeletal muscle fibres?

A

Myofibrils are not present - instead, myofilaments (actin and myosin) form huge masses within the cardiac fibre - perimysium does not surround the myofilaments to form myofibrils

22
Q

What is the sarcolemma, sarcoplasm, and the sarcoplasmic reticulum?

A

The plasma membrane, the cytoplasm, and the endoplasmic reticulum found in muscle fibres

23
Q

Other than colour, how do red and white muscle fibres differ on a histology slide?

A

Red muscle fibres are narrower, while white muscle fibres are wider

24
Q

Do red fibres contract quickly or slowly? How does this mean they utilise energy?

A

Red fibres contract slowly, and as such are designed to utilise energy for longer

25
Q

Where are nuclei located in skeletal muscle?

A

At the periphery

26
Q

Which structure is composed of the myosin and actin filaments?

A

A myofibrils

27
Q

What does muscle hypertrophy describe?

A

An increase in the diameter of a muscle fibre, and increased metabolic changes in the cell, such as more mitochondria and greater blood flow

28
Q

In a muscle fibre, where do mitochondria lie?

A

Mitochondria lie in between the myofibrils

29
Q

What is a fascicle composed of?

A

A fascicle is composed of muscle fibres, which are composed of myofibrils, which are composed of myofilaments (actin and myosin)

30
Q

What can be used as a marker for cardiac ischaemia?

A

Troponin

31
Q

Where is creatine kinase seen?

A

There are elevated levels in the blood she heart muscle is damaged

32
Q

Describe the structure of myosin.

A

A myosin filament contains many myosin molecules, which have a rod-like tail from which 2 heads protrude - a myosin filament contains many myosin molecules

33
Q

What structure does an actin filament form?

A

A helix

34
Q

In which zone are the actin filaments devoid of heads?

A

H band

35
Q

What structure reinforces the actin helix? What other molecule is attached to this molecule?

A

Tropomyosin coils around the actin helix, reinforcing it - a troponin complex is attached to each tropomyosin molecule

36
Q

What happens to tropomyosin when Ca2+ levels rise within the muscle fibre?

A

Ca2+ binds the TnC component of troponin, which induces a conformational change in tropomyosin, which removes it from the myosin binding site on the actin helix - this then allows the myosin head to bind actin and cause isle contraction

37
Q

What is rigor conformation?

A

This denotes that a lack of ATP causes the myosin head to remain fixed to the actin molecule - this is seen in rigor mortis

38
Q

How does ATP act on myosin? What does hydrolysis of the ATP molecule cause?

A

It causes it to uncouple from the actin filament - hydrolysis shifts the myosin back into its original conformation where it binds the actin filament again

39
Q

How does an action potential in skeletal muscles cause Ca2+ release?

A

Acetylcholine binds nicotinic acetylcholine receptors on the sarcolemma of a muscle fibre - this instigates an action potential, via Na+ entry into the muscle fibre - this action potential travels along the sarcolemma and down T-tubules, where it changes their conformation at terminal cisternae - these then release Ca2+ from the sarcoplasmic reticulum

40
Q

What is a terminal cisternae?

A

Enlarged areas of the sarcoplasmic reticulum that surround the T-tubules - these regions secrete Ca2+ into the sarcoplasm, eliciting muscle contraction

41
Q

Where are nuclei positioned in cardiac muscle fibres? How many are there per fibre?

A

Nuclei are positioned centrally in cardiac muscle fibres, and there are usually 1-2 nuclei per muscle fibre

42
Q

What is endomysium? What is perimysium?

A

The endomysium is a layer of connective tissue that surrounds each muscle fibre/cell - the perimysium is the layer of connective tissue that surrounds each muscle fascicle (which itself is composed of several muscle fibres)

43
Q

Which muscle type are intercalated discs found? What do they replace, and what is their function?

A

Intercalated discs are found in cardiac muscle - they replace Z bands, and have gap junctions for electrical coupling, and adherens-type junctions to anchor the actin filaments

44
Q

Which muscle tissue is associated with diads? Which muscle tissue is associated with triads?

A

Cardiac muscle is associated with diads - skeletal muscle is associated with triads

45
Q

Where is ANP synthesised, stored, and released?

A

Atrial myocytes in response to distension

46
Q

How do ANP and BNP reduce blood pressure?

A

They increase the kidneys glomerular filtration rate, lowering the blood volume, and inhibit renin production from the kidney, inhibiting the cascade that would lead to angiotensin II - this causes vasodilation which contributes to the lowering of blood pressure

47
Q

Do smooth muscle fibres contain T-tubules?

A

No

48
Q

List 2 types of modified smooth muscle cells, and what their function is.

A
  • myoepithelial cells - surround glands and assist contraction for secretion
  • myofibroblasts - prominent in wound contraction at sites of wound healing

Body Logistics (13 decks)

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