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BL > BL S13 Muscle > Flashcards

BL S13 Muscle Flashcards

1
Q 
What do the following words mean:
Myalgia
Myasthenia 
Myocardium
Myopathy
Myoclonus
A
  • Muscle pain
  • Muscle weakness
  • Heart Muscle
  • Disease of muscle
  • Sudden muscle spasm.
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2
Q

What role does myoglobin play?
What type of muscle is it present in?
What is rhabdomyolysis and what clinical significance does it have in terms of myoglobin?

A

Transfers oxygen from haemoglobin to respiring muscle cells.
Striated muscle
The destruction of striated muscle cells.
Such muscle necrosis leads to myoglobinuria.

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3
Q

Distinguish between epimysium, endomysium and perimysium.

A
  • Endomysium is loose connective tissue that surrounds individual muscle fibres.
  • Perimysium surrounds a bundle of muscle fibres forming a fascicle.
  • Epimysium is a dense irregular connective tissue that surrounds multiple fascicles.
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4
Q

Limbs are divided into compartments delineated by _________.

What gives rise to compartment syndrome?

What is a fasciotomy?

A

fascia

Trauma in one of the compartments causes internal bleeding and exerts pressure on blood vessels, nerves and other compartments.

A procedure in which fascia is cut to relieve tension or pressure.

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5
Q

What are some symptoms and clinical signs of compartment syndrome?

A 
Deeps constant poorly localised pain.
Paresthesia - altered sensation 
Compartment is palpably tense and firm. 
Swollen / shiny skin with bruising. 
Prolonged capillary refill time.
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6
Q

What is an extrinsic muscle?

A

A muscle that lies superficially on a structure.

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7
Q

What muscle in the tongue allows for it to be stuck out?

Damage to what nerve can cause deviation of the extended tongue?

What can be said about how the skeletal muscles of the tongue terminate?

A

Geniohyoid muscle

Hypoglossal nerve damage

Terminate via interdigitation with the collagen and extracellular matric of their surrounding connective tissue.

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8
Q

What factors account for the multidirectional mobility of the tongue?

A

Plasticity and strength of the connective tissue
+
multidirectional orientation of the muscle fibres

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9
Q

Give 4 features of skeletal muscle.

What causes the striations seen in skeletal muscle?

A

Striated
Long fibres
Multinucleate
Periphery nuclei

Dark A bands and lighter I bands.

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10
Q

What is muscle atrophy and why does it occur?

A

Muscle atrophy is the decrease in the mass of a muscle and results from rate of destruction of myocytes being greater than the rate at which they are replaced.

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11
Q

How does disuse atrophy occur?

Why is power of the muscle lost?

A

Occurs from:

  • Bed rest
  • Sedentary behaviours
  • Limb immobilisation for long periods.

Loss of protein - reduces diameter of fibre - loss of power.

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12
Q

How does denervation atrophy occur?

What are some symptoms?

A

Lesions in motor neurones supplying the fibre

Weakness
Flaccidity of muscle

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13
Q

What is hypertrophy and muscular hypertrophy?

What happens to a muscle when it becomes hypertrophied?

A

Hypertrophy is the enlargement of cells / muscle cells.

More contractile proteins into the fibre increasing fibre diameter.

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14
Q

What are some metabolic changes that can be seen in hypertrophied muscle?

A

Increased:

  • Glycolytic activity
  • Mitochondrial activity
  • Glycogen stores
  • Blood supply to muscle
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15
Q

How can stretching and immobilisation affect muscle length and why?

A

Stretching increases muscle length and immobilisation decreases muscle length.

Stretching more sarcomeres are added
Immobilisation - sarcomeres disappear

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16
Q

What are the defining features of the following:

  • M Line
  • H Band
  • A Band
  • I Band
  • Z Line

What is the region from one Z line to the next called?

A 
M line - myosin + myomesin 
H band - myosin only 
A band - myosin and actin 
I band - Actin only 
Z line - alpha actinin only

Sarcomere.

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17
Q

Describe the structure of an actin filament.

Describe the structure of a myosin filament.

A

Many G-actin units join form 2 F-actin chains which coil around each other.
Tropomyosin coils around the 2 F-actin chain
Troponin complexes attached at intervals along this structure.

Aggregates of myosin molecules
Each myosin molecule has 2 heads and a tail
Attached at myosin tails by myomesin.

18
Q

What are the roles of titin and nebulin?

What are the roles of myomesin and C protein?

What can the M line bind?

A

Act as molecular ruler for sarcomere assembly.

Myomesin and C protein cross link myosin and M band region of titin.

Creatine kinase

19
Q

Describe the sliding filament model.

A

Myosin head starts in high-energy configuration - ADP and Pi attached to head which is attached to the actin forming a cross bridge.
ADP and Pi released - power stroke - myosin head pivots moving acting filament towards M line.
ATP attaching to head causes head to detach - low-energy configuration.
ATP hydrolysed - ADP and Pi attached head cocks - cross bridge reformed.

20
Q

What is a motor unit?

Each ______ innervated by one neurone but one ________ may _______ many fibres.

A

A motor unit consists of an alpha motor neurone and the muscle fibres it innervates.

Fibre, neurone and innervate

21
Q

What can be said about muscle fibres within a motor unit?

What relationship is there between number of of fibres a motor unit innervates and type of contraction?

A

Same contractile type - slow or fast contracting.

Fewer fibres - more fine control
More fibres - more power

22
Q

Define proprioception

What is an intrafusal muscle fibre?

What is an extrafusal muscle fibre?

A

The sense of the relative positioning of one’s own body parts.

A specialised skeletal muscle fibre that detect the amount and rate of change in the length of a muscle.

Standard skeletal muscle fibre that contact allowing for skeletal movement.

23
Q

How many neurones are intrafusal muscle fibres aka spindle fibres innervated by and what are there names?

What are the roles of these neurones?

How are muscle spindles walled off from the rest of the muscle?

A

1 sensory and one motor neurone.
Gamma motor neurone keep the fibres taught.
Alpha Ia neurone relays rate of change of muscle length to CNS
Alpha II neurone promised position sense.

By a collagen sheath.

24
Q

What are the 5 features of cardiac muscle?

What do intercalated discs do?

A 
Branched
Intercalated discs
Mono or bi nucleate
Striated 
Centrally positioned nuclei

Allow for electrical and mechanical coupling with adjacent cells.

25
Q

What are the 2 ways in which cardiac tissue can increase in size?

A

Hyperplasia and hypertrophy

26
Q

Naturietic Hormones are ______ hormones synthesised by heart, _____ and other organs.

What are they released by the heart in response to?

A

Atrial and Ventricular distension usually in repose to heart failure

27
Q

What are the main physiological actions of naturietic hormones?

Normal heart secrete very small amounts of ANP, elevated levels suggest what?

A

Decreasing blood volume
Decreasing systemic vascular resistance.

Left ventricular hypertrophy, congestive heart failure (hypervolemic state) and mitral valve disease.

28
Q

What is the difference in where ANP and BNP are synthesised?

What so elevated levels of BNP and NT-pro-BNP suggest?

A

ANP - atrial myocytes
BNP - ventricular myocytes and brain

Increased LV filling pressure and dysfunction.

29
Q

Describe the effects of ANP and BNP.

A

Decrease renin levels which in turn decreases levels of Ang II and Aldo.
Decreased levels of Ang II and action of ANP and BNP cause vasodilation decreasing blood pressure.
ANP and BNP increase GFR leading to natrieusis and diuresis.
Decreased AngII and Aldo also lead to this.
Natrieusis and diuresis decrease blood volume and blood pressure.

30
Q

What is troponin used as a clinical marker of and what forms of troponin are assayed?

Is the quantity of troponin released proportional to the degree of the damage?

A

Cardiac ischaemia
I and T troponin

No.

31
Q

What had CK been used to diagnose?

Is the CK level increase proportional to the size of the infarct?

A

MI

Yes

32
Q

What can cause a CK concentration rise?

A 
Intramuscular injection.
Vigorous exercise 
Falling - elderly 
Rhabdomyolysis - striated muscle breakdown. 
Muscle dystrophy 
Acute kidney injury.
33
Q

Purkinje fibres are modified myocytes, what is there role?

A

Carry APs from AV node around ventricular walls.

34
Q

Describe how the wave of excitation travels around the heart.

A

Starts at SAN
Around atrial walls to AV node
Delayed here - allow for atrial contraction
Pass through bundle of his into the interventricular septum.
Bundles divide into right and left branches
Travel to apex and from there purkinje fibres carry signal around ventricular walls.

35
Q

What are some features of purkinje fibres?

A 
Large cells
Abundant glycogen 
Spare myofilaments
Extensive gap junctions
Rapid conduction
36
Q

What are 3 structural features of smooth muscle?

What can be said about contraction of smooth muscle?
Does this type of contraction require more or less ATP?

A

Spindle shaped
Central nucleus
No striations

Slow and sustained

37
Q

How is smooth muscle arranged?

What stimuli does it respond to?

A

Sheets, bundles or layers.

Nerve signals, drugs hormones or local concentration of blood gases.

38
Q

Where is smooth muscle usually found and what is its function there?

Name some places it is found.

A

Forms a contractile wall of a passageway or cavity

Allows for modification of the cavity volume and lumen size.

Vascular structures
Respiratory GI and genitourinary tract.

39
Q

What is smooth muscle clinically significant in?

A 
Asthma
Detrusor muscle instability 
Dysmenorrhea 
Artherosclerosis 
Abnormal gut motility
40
Q

What are 2 types of modified smooth muscle cells?

What are there functions?

A

Myoepithelial cells - form basket work around secretory units of exocrine glands.

Myofibroblasts - sites of wound healing
Make collageous matrix but can contract wound.

41
Q

How do they 3 muscle types repair themselves?

A
  • Skeletal muscle - cant divide but regenerate via mitosis of satellite cells - hyperplasia
    Satellite cells can also fuse with existing muscle cells - hyper trophy
  • Cardiac muscle - cant regenerate
  • Smooth muscle - retains mitotic activity therefore divide to form new cells.
42
Q

What happens when cardiac muscle becomes damaged?

A

Fibroblasts invade and lay down scar tissue.

BL (12 decks)

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