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BodyLog * > S5 Muscles > Flashcards

S5 Muscles Flashcards

1
Q

Which muscles are striated?

A

Skeletal and cardiac muscles

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2
Q

Which muscles have myoglobin?

A

Skeletal and cardiac muscles

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3
Q

Which muscles have an involuntary response?

A

Smooth and cardiac muscle

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4
Q

What are the layers of connective tissue in skeletal muscle?

A

Endomysium (surrounding muscle fibres)

Perimysium (surrounding each fascicles)

Epimysium (around the while muscle)

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5
Q

What does movement of the skeletal muscle depend on?

A

The direction of the muscle fibre contraction

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6
Q

How do the skeletal muscles of the tongue end?

A

End in interdigitations

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7
Q

Where are the nuclei positioned in skeletal muscle cells?

A

At the edges (peripheral)

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8
Q

Sarcomere structure:

A

Layers of myosin and actin filaments.

M line - line down centre
H band - area that is only myosin in middle
A band - length of myosin 
Z lines - ends of sarcomere
I band - actin only on ends
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9
Q

What are type 1 slow twitch fibres?

A 
Slow oxidative fibres. 
Have a rich capillary supply.
Smaller diameter of fibres
Use aerobic respiration
Have lots of myoglobin, mitochondria and cytochromes.
Red in colour.
Fatigue resistant.
Used for endurance activities e.g standing/walking.
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10
Q

What are type 2A fast twitch fibres?

A 
Fast oxidative glycolysis fibres.
Have a rich capillary supply.
Larger diameter of fibres.
Use aerobic respiration.
Have lots of myoglobin, mitochondria (slightly less) and cytochromes.
Red/pink in colour.
Moderate fatigue resistant.
Assist type 1 and 2B activities e.g standing/walking if type 1 needs help.
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11
Q

What are type 2B fast twitch fibres?

A 
Fast glycolytic fibres.
Have a poor capillary supply.
Larger diameter of fibres.
Use anaerobic respiration.
Have less myoglobin, mitochondria and cytochromes.
White in colour.
Fatigue quickly.
Used for strength/anaerobic type activities e.g jumping/running/sprinting also used last if need help with standing/walking
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12
Q

What two things does continued muscle contraction depend on?

A

Calcium ions and amount of ATP

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13
Q

What energy store do slow twitch muscle fibres use?

A

Fatty acid stores

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14
Q

What energy store do fast twitch muscle fibres use?

A

Glycogen stores

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15
Q

How many nuclei do cardiac muscles have and where are the nuclei positioned?

A

Can have 1 or 2 per cell.

Positioned centrally.

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16
Q

What can you find between adjacent cells in cardiac muscle fibres?

A

Intercalated discs

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17
Q

What do intercalated discs do?

A

Used for electrical and mechanical coupling of adjacent cells.
Contain gap junctions

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18
Q

What is the structure of cardiac muscles?

A

Striated and branched

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19
Q

What are ANP granules and what do they look like on a micrograph

A

ANP is atrial natriuretic peptide, it is released by the atria during heart failure (congestive heart failure). They work to reduce the arterial pressure by decreasing blood volume and systematic vascular resistance.

Look like black blobs on micrograph

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20
Q

What is hypertrophy?

A

Enlargement of cells

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21
Q

What is hyperplasia?

A

Multiplication of cells

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22
Q

What is atrophy?

A

Shrinking of cells

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23
Q

How does the conducting system in the heart work (what is the order a signal travels in)?

A
  1. Sinoatrial node
  2. Atrioventricular node
  3. Down bundle of His
  4. Into purkinje fibres
24
Q

What are purkinje fibres and what do they have?

A

Purkinje fibres are large cells that conduct action potentials rapidly which allows ventricles to contract simultaneously.

They have:

  1. Adbundant glycogen
  2. Sparse myofibrils
  3. Extensive gap junction sites
25
Q

What is the structure and shape of smooth muscle?

A

Spindle-shaped (fusiform) - sheets/bundles/layers containing lots of cells and have caveolae (invaginations)

26
Q

Where is the nucleus in smooth muscle and do they have 1 or more?

A

One central large nucleus

27
Q

Do smooth muscles rely on actin and myosin?

A

Yes, but the contractions are slower, last longer and need less ATP

28
Q

What is the usual role of smooth muscle?

A

Modify volume - form contractile walls of passageways or cavities

E.g. in GI, respiratory and urinalysis tracts

29
Q

As the smooth muscle is involuntary, it can cause disorders, for example:

A
  1. High blood pressure
  2. Painful menstruation
  3. Asthma
  4. Irritable bowel syndrome
  5. Incontinence
30
Q

What is smooth muscle like in the gut?

A

Muscularis externa - circular and then longitudinal layers of muscle

31
Q

How is smooth muscle innervated?

A

Innervated by the autonomic nervous system. NT are released from varicosities into a wide synaptic cleft.

32
Q

Is repair of skeletal muscle possible?

A

The cells can’t divide but they can regenerate by the mitotic activity of satellite cells - hyperplasia occurs.

Satellite cells can also fuse with existing muscle cells to increase mass - hypertrophy.

33
Q

What are satellite cells?

A

Muscle stem cells

34
Q

Is repair of cardiac muscle possible?

A

Cells can’t regenerate. After damage, fibroblasts lay down scar tissue.

35
Q

Is smooth muscle repair possible?

A

Cells retain their mitotic activity and can form new cells.

E.g in the pregnant uterus - muscle wall undergoes hyperplasia and hypertrophy.

36
Q

Do smooth muscle have sarcomere and troponins?

A

No

37
Q

How are cardiac muscles innervated?

A

Through t-tubules depolarised from by the neuromuscular junction

38
Q

What is myasthenia gravis?

A

It is an autoimmune disease in which the person’s own antibodies block the Ach receptors. Invaginations in the end plate (sarcolemma) are reduced so there is reduced transmission. Leads to muscle weakness.

39
Q

What is compartment syndrome?

A

When trauma occurs in a compartment of a limb, it could lead to internal bleeding which exerts pressure on blood vessels and nerves.

Can lead to compartment syndrome - deep localised pain, paesthesia, swelling.

40
Q

Do healthy muscles ever fully relax?

A

No, retain the muscle tone - makes muscles ready to react and this improved with exercise

41
Q

When does muscle remodelling occur?

A

It is continual

42
Q

What happens when destruction of muscle outweighs replacement?

What happens when replacement outweighs destruction?

A

Atrophy

Hypertrophy

43
Q

How does muscle hypertrophy occur?

A

Overstretching - A and I bands can no longer engage.

New muscle fibrils are produced or new sarcomeres are added in the middle of existing sarcomeres (makes it longer)

44
Q

How does muscle atrophy occur?

A

Could be due to:

  1. Disuse (bed rest, age, sedentary behaviour)
  2. Surgery (denervation of muscle)
  3. Disease (muscular dystrophies)

Due to a loss of protein leads to reduced fibre diameter so loss of muscle power

45
Q

How long does it take for nerve regeneration to muscle tissues?

A

3 months

46
Q

4 clinical issues related to muscle dysfunction?

A
  1. Duchenne muscular dystrophy
  2. Rhabdomyolysis
  3. Myocardial infarction
  4. Botulism and organophosphate poisoning
47
Q

What is duchenne muscular dystrophy?

A

Inherited on x-chromosome (recessive) - mutation of dystrophin gene

Muscle cells are replaced with adipose tissue

48
Q

What does the absence of dystrophin lead to?

A
  1. Excess Ca2+ taken up by muscle cells
  2. Ca2+ taken up by mitochondria
  3. Water taken up with Ca2+
  4. Mitochondria burst
  5. Muscle cells burst (rhabdomyolysis)
  6. Creatine kinase and myoglobin levels high in blood
49
Q

What is creatine kinase?

A

It is an enzyme that is use to convert creatine into creatine phospahate and vice-versa (it acts as an energy store).

50
Q

How can creatine kinase be used clinically?

A

Can be measured to diagnose a heart attack (however now use troponin I as a measure).

It is released into the blood when damage to muscles occur.

51
Q

How are troponin assays used to measure myocardial damage?

A

Troponin I and T can be used to detect cardiac ischaemia

52
Q

What does botulism toxin do?

How is it used clinically and cosmetically?

A

Blocks neurotransmitter release at the motor end plate, leads to non-contractile state of skeletal muscle.

Clinically - to treat muscle spasms
Cosmetically - to treat wrinkles

53
Q

What are organophosphates? And how do they poison us?

A

They are pesticides.

They inhibit the normal function of Ach esterase. Means Ach in the cleft isn’t broken down (stays bound to receptors in sarcolemma).
Leads to SLUDGE (muscarinic receptors) and MTWTF (nicotinic receptors)

54
Q

What does SLUDGE stand for?

A 
Salivation
Lacrimation
Urination
Defecation
GI cramping 
Emesis
55
Q

What does MTWTF stand for?

A 
Muscle cramps
Tachycardia
Weakness
Twitching
Fasciculations

BodyLog * (16 decks)

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