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Body Logistics > Lecture: 11 Muscle Tissue > Flashcards

Lecture: 11 Muscle Tissue Flashcards

1
Q

Compare and contrast cardiac & smooth muscle (3 points).

A 
C+S= 1 contractile unit 
C+S= central nuclei
C+S= Act as syncytium (multiple cells fused as 1)
C+S= Myocytes communicate via gap junctions
C+S= indirect nerve-muscle communication 
C= striated (sarcomeres)        S= not striated
C= troponins 1+2           S= no troponins
C= specialised electrical conduction cells (purkinje)
C= 1/2 nuclei        S= only 1 nucleus
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2
Q

Compare and contrast cardiac & skeletal muscle (3 points).

A

C+S= both striated
C+S= both contain myoglobin
C+S=both have T tubules

C= sarcomere contractile unit  S=slow/fast twitch contractile unit
C= direct nerve-muscle communication      S=indirect
C= central nuclei     S= peripheral 
C= few T tubules     S= many T tubules
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3
Q

Compare and contrast smooth & skeletal muscle (3 points).

A

Both= both have actin and myosin

SK= striated   SM= not striated
SK= troponin    SM= no troponin
SK= Myb            SM= no Myb
SK= peripheral nuclei    SM= central nuclei
SK= voluntary   SM= involuntary
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4
Q

Which of the 3 types of muscles are striated?

A

Skeletal and cardiac

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5
Q

Which of the 3 muscles uses indirect nerve-muscle communication?

A

Cardiac and smooth

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6
Q

What is myoglobin and compare it to haemoglobin?

A

A red protein similar to a singular subunit of Hb and has a higher affinity for solely O2.

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7
Q

What is myoglobinaemia and what are the consequences of it?

A

High Myb blood levels due to muscle necrosis or rhabdomyolysis. Too much Myb causes renal damage as this can block the glomerulus since the kidney is supposed to remove it from blood. Causes tea-coloured urine.

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8
Q

When is myoglobin (Myb) used instead of Hb?

A

Myb stores O2 for when needed in anaerobic conditions. The higher affinity of O2 means it can more easily bind to O2.

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9
Q

What are the muscular equivalents of…

  1. Cell membrane
  2. Cytoplasm
  3. SER
  4. Mitochondria
A
  1. Sarcolemma
  2. Sarcoplasm
  3. Sarcoplasmic reticulum
  4. Sarcosome
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10
Q

What is a sarcomere?

A

Contractile unit of cardiac and smooth muscle where 1 unit is between 2 adjacent Z lines.

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11
Q

What does the skeletal hierarchal muscle structure consist of?

A

Muscle–>Fascicles–>Muscle fibre/cell/myocyte—> Myofibrils

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12
Q

If the muscle striations are vertical, in which direction will the muscle contract?

A

Imagine the striations are the z lines. During contraction the z lines move closer together, resulting in lateral contraction.

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13
Q

What are the connective tissues surrounding the structures of the muscle?

A

Epimysium around muscle; perimysium around fascicles; endomysium around fibres

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14
Q

Name 3 muscle shapes in terms of muscle movement direction.

A

Convergent Parallel
Unipennate Fusiform
Bipennate Circular

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15
Q

What is created at the point of origin?

A

Tension

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16
Q

Where is tension created (in terms of anatomy)?

A

Point of origin

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17
Q

What is created at the insertion tendon point?

A

Movement

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18
Q

Where is movement created (in terms of anatomy)?

A

Insertion tendon point

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19
Q

What is an extrinsic muscle and give an example?

A

Part of the muscle where the origin is further from the movement and typically has insertions in bone/cartilage. Eg: tongue geniohyoid muscle.

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20
Q

What is an intrinsic muscle and give an example?

A

Completely contained in an organ or contained in the part that it acts on: typically muscle attached to muscle. Eg: vertical or transverse muscles of tongue.

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21
Q

Describe the dark band of sarcomeres.

A

Mostly myosin band called A band and found between I bands.

22
Q

Describe the light band of sarcomeres.

A

Actin band called I band and found between A bands.

23
Q

What happens in a muscular contractile unit during contraction?

A

Sarcomere shortens.
Z lines come closer together.
Myosin and actin slide over each other.
M line doesn’t move.

24
Q

What is the H band of sarcomeres?

A

Part of the A band where there is no actin at all.

25
Q

What are the 2 contractile units of skeletal muscles?

A

Fast and slow twitch muscles

26
Q

What type of catabolic processes do slow twitch fibres rely on?

A

Slow oxidative processes like oxidative phosphorylation.

27
Q

What type of catabolic processes do fast twitch fibres rely on?

A

Fast glycolytic processes

28
Q

Give 5 differences between fast and slow twitch fibres.

A

F= white colour S= Red colour
F= few mitochondria S= Many mitochondria
F= few cytochromes S= many cytochromes
F= poorer blood supply S= richer blood supply
F=fast contraction speed S=slow contraction speed
F= short contractions S= longer contractions
F= larger fibre diameter S= smaller fibre diameter
F= lots ATP/few CO2 S= few ATP/ lots CO2
F= running, jumping S= walking, standing

29
Q

Which muscle do you find intercalated discs and what do they do?

A

Cardiac muscle. They allow electrical signals and ions to pass cell to cell; connect adjacent cells to form a bigger, syncytium-like cell.

30
Q

Why is cardiac muscle not considered true syncytium tissue?

A

Cardiac muscles are originally individual myocytes. They only act like syncytial tissue due to intercalated discs interacting with other cells: hence multiple cells acting as 1 larger cell.

31
Q

What happens when an intercalated disc breaks/separates between 2 muscle cells?

A

The myocyte is going to die and fibroblasts will fill the space with connective tissue; leaving a scar.

32
Q

What is an intercalated disc?

A

Made of gap junctions, tight junctions, desmosomes, adherence junctions that attach myocytes together into branches.

33
Q

What does the heart release during heart failure?

A

ANP (atrial natriuretic peptide) and BNP (brain natriuretic peptide)

34
Q

When is ANP released?

A

During congestive heart failure

35
Q

When is BNP released?

A

During left ventricular hypertrophy or bicuspid/mitral valve disease.

36
Q

How do ANP and BNP reduce heart failure?

A

Both hormones work to reduce BP in the heart by decreasing blood vol. and vascular resistance.
This is done by increasing more fluid into kidneys’ collecting duct so less water goes to the blood vol.

37
Q

Briefly give an overview of the heart conducting system.

A
  1. SAN signals via Bachmann bundles.
  2. Signal causes atrial systole and stimulates AVN.
  3. AVN sends impulse down septum and reaches purkinje fibres.
  4. Cause ventricular systole from the bottom up.
38
Q

Why is it important for the atria and ventricles to not contract simultaneously?

A

This allows ventricles to fill up fully with blood before systoles so more blood is pumped out of the heart at once.

39
Q

How are purkinje fibres adapted to their function?

A

Lots of glycogen and intercalated cells!!! Electricity can move rapidly due to many gap junctions (in intercalated discs) so ventricles contract simultaneously.

40
Q

What clinical problems can occur due to involuntary muscles and why?

A

Painful menstruation IBS
Hypertension Incontinence (bladder)
Asthma

Involuntary muscle can have a mind of its own.

41
Q

What can happen if there is Ca2+ ions in the muscle for a prolonged period of time?

A

Ca2+ are required for muscle contraction so having it in muscles for a long time means that the contraction will last a longer time. Too long could lead to cell damage.

42
Q

Which of the 3 mature muscle types repair itself?

A

Cardiac adult = not really as stem cells from bone marrow- instead fibroblast divide and lay down scar tissue.

Cardiac children= can due to retaining fetal myotubules

Skeletal= need satellite cells mitosis so differentiates into skeletal then hyperplasia or hypertrophy + fusing with existing cells.

Smooth= very well as retain mitotic ability

43
Q

A patient is diagnosed with multisystemic SM dysfunction syndrome where they have GI problems, a weak bladder and respiratory infections. Which structure of muscle tissue is unique to SM and could be responisble?

A

The fact that actin and myosin filaments assemble on the dense bodies during contraction.

44
Q

A 5 yrs boy has a small tear in his calf muscle (falling off his bike) and is told to rest so the muscle can regenerate. Which MSK repair mechanism is likely to take place?

A

Muscle satellite cells can proliferate then differentiate into myofibres.

45
Q

If a patient comes is and has a suspected MI, their plasma troponin would be monitored. Which troponin(s) would be a clinical marker and describe how long they would remain in the blood for.

A

Troponin I+T (not C) would be released over the next 7 days where you have a very sudden increase then a gradual decline.

46
Q

A healthy person’s muscle I band is 1.0μm and their A band is 1.5μm. During contraction, their sarcomeres shorten by 10%. How long would the A band be now?

a) 0.45μm
b) 0.90μm
c) 1.00μm
d) 1.35μm
e) 1.50μm

A

e) 1.50μm

When striated muscle fibres contract, sarcomeres shorten and the z-lines come closer together. However, A and I bands don’t shorten because they slide over each other.

47
Q

A 15yrs boy has ptosis (drooping eyelids) and other symptoms of myasthenia gravis. Which structure in a normal neuromuscular junction would be missing from this patient?

A

Endplate invaginations which is where ACh receptors are inserted.

48
Q

2 people are discussing the mechanism of striated muscle contractions. Which primary contraction event is caused by Ca2+ ions?

A

Ca2+ interacts with the troponin-tropomyosin complex so a conformational change occurs within the complex to reveal the myosin binding site on G-actin.

49
Q

A boy is diagnosed with Duchenne muscular dystrophy which is caused by a dystrophin protein mutation. Describe how the mutation causes this condition.

A

X-linked recessive condition that affects the dystrophin protein. This protein usually inserts into the sarcolemma but the mutated protein doesn’t do that. Resulting in: poor balance, strange gait, shoulders and back are held posterior to the midline.

50
Q

A farmer uses a organophosphate pesticide without proper protective equipment. Consequently, he presents in a state of delirium, GI cramps and MSK fasciculations (involuntary twitches). Which component of the neuromuscular junction is affected?

A

Organophosphates bind and inactivate ACh esterase in the neuromuscular junction. As a result, ACh is degraded by this enzyme: which results in these signs and symptoms.

51
Q

After undergoing surgery, the patient is given succinylcholine as part of their anaesthetic regimen. However, they develop symptoms of hyperthermia due to an unrecognised gene mutation. Which part of the contraction pathway is likely to be defective in the this patient?

a) sarcolemma
b) sarcoplasmic reticulum
c) transverse tubule
d) ryanodine receptor (RyR1)
e) dihydropyridine receptor (DHPR)

A

d) ryanodine receptor (RyR1)

Mutations in the RyR1 can cause malignant hypothermia.
Since the patient has hyperthermia, there is probably a mutation in this receptor as it concerns internal temperature.

Body Logistics (13 decks)

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