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CARDIO > Heart > Flashcards

Heart Flashcards

1
Q

What are the layers of the heart? (6)

A 
Pericardium
Parietal pericardium
Pericardial space
Viseceral pericardium/ epicardium
Myocardium
Endocardium
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2
Q

What supplies parasympathetic stimulation to the heart?

A

Vagus nerve (CN X) (innervates atria)

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3
Q

What neurotransmitter is involved in the parasympathetic stimulation of the heart?

A

ACh (acetylcholine)

binds to muscarinic receptors

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4
Q

What does parasympathetic stimulation of the heart cause? (3)

A
  • Decreased heart rate
  • Decreased force of contraction
  • Decreased cardiac output
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5
Q

What supplies sympathetic stimulation to the heart?

A

Postganglionic fibres innervate the entire heart

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6
Q

What neurotransmitter and hormone are involved in the sympathetic stimulation of the heart?

A

Adrenaline

Noradrenaline

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7
Q

What does sympathetic stimulation of the heart cause? (3)

A
  • Increased heart rate
  • Increased force of contraction
  • Increased cardiac output
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8
Q

Where does the initial depolarisation signal arise from in the heart?

A

SA node (conducting-system cells) located in RA

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9
Q

Describe the path of depolarisation in the heart

A
  1. SA node
  2. AV node
  3. Bundle of HIS
  4. RBB/ LBB
    5 Purkinje fibres
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10
Q

What mechanisms allow atrial contraction to fully complete before ventricular depolarisation begins?

A

Propagation of AP through the AV node is relatively slow

Ring of non-conducting tissue separates atria and ventricles

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11
Q

What forms the majority of the thick filament?

A

Myosin

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12
Q

What is myosin comprised of?

A

Two heavy pp chains

Four light pp chains

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13
Q

What is the structure of myosin?

A

Two globular heads

Long intertwined tail

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14
Q

What do globular myosin heads contain?

A

ATP binding site

Actin binding site

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15
Q

What forms the majority of the thin filament?

A

Actin

tropomyosin and troponin

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16
Q

What is the structure of actin?

A

Two intertwined helical chains (made of polymerised actin monomers)

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17
Q

What is tropomyosin?

A

Long molecule that OVERLIES myosin binding sites on actin

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18
Q

What is troponin?

A

On Ca2+ binding, troponin changes shape, dislocating tropomyosin and exposing myosin binding sites on actin

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19
Q

What enables contraction to occur?

A

The movement of tropomyosin exposing myosin binding sites on actin

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20
Q

What is a sarcomere?

A

Two successive Z-lines

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21
Q

How is Ca2+ released in response to an AP in cardiac muscle?

A

Ca2+ enters through L-channels in T-tubules

Binds to ryanodine receptors on SARCOPLASMIC RETICULUM which releases more Ca2+

22
Q

How is Ca2+ released in response to an AP in skeletal muscle?

A

AP induces DHP receptors (in T-tubules) to pull open ryanodine receptors allowing Ca2+ release

23
Q

Why is the plateau phase important? (2)

A

Prevents tetany in case of recurrent stimuli

Allow the heart to fill (only happens during relaxation)

24
Q

Describe the 5 stages in generation of an AP in cardiac myocytes

A

0 - influx of Na+
1 - efflux of K+ through transient K+ channels
2 - influx of Ca2+ through L-type Ca2+ channels and efflux of K+
3 - efflux of K+
4 - Na+/K+ ATPase and open K+ channels

25
Q

Describe the 3 stages in generation of an AP in nodal cells

A

4 - declining K+ permeability, Na+ influx through F-type Na+ channels, Ca2+ influx through T-type Ca2+channels
0 - Ca2+ influx through L-type Ca2+ channels
3- L-type Ca2+ channels close, K+ channels open

26
Q

What are the main stages of AP generation (including relevant numbers)

A 
0 = depolarisation
1 = partial repolarsation
2 = plateau
3 = repolarisation
4 = reestablishing resting potential (polarised)
27
Q

Why is it the SA node that determines the pace of the heart?

A

SA nodal cells brought to threshold more rapidly than AV nodal cells, therefore, have a higher inherent depolarisation rate

28
Q

What does the P wave of an ECG show?

A

Atrial depolarisation

29
Q

What is shown by the PR interval?

A

Time taken for atria to depolarise and electrical activation to get through to AVN

30
Q

What does the QRS complex show?

A

Ventricular depolarisation

31
Q

What is shown by the T wave?

A

Ventricular repolarisation

32
Q

What does each small square represent on an ECG graph?

A

40ms (milliseconds)

33
Q

What does each big square represent on an ECG graph?

A

0.2s

34
Q

What occurs during systole?

A

Ventricular contraction

Blood ejection

35
Q

How long does systole last?

A

0.3s

36
Q

What occurs during diastole?

A

Ventricular relaxation

Blood filling

37
Q

How long does diastole last?

A

0.5s

38
Q

What is isovolumetric contraction? (3)

A

Pressure increases
Fixed volume
All valves are CLOSED

39
Q

Where is the tricuspid valve located? (what is it also known as?)

A

RA and RV

aka R atrioventricular valve

40
Q

Where is the bicuspid valve located? (what is it also known as?)

A

LA and LV

aka L atrioventricular valve, mitral valve

41
Q

What is isovolumetric relaxation? (3)

A

Pressure decreases
Fixed volume
All valves are CLOSED

42
Q

What is diastasis?

A

No net movement of blood into ventricles

Pressure between atria and ventricle equalises

43
Q

What is end-systolic volume?

A

Amount of blood remaining in ventricles after systole/ diastole
Aka preload

44
Q

What is end-diastolic volume?

A

Amount of blood remaining in ventricles after diastole

45
Q

What is preload?

A

Volume of blood in ventricles just before contraction

46
Q

What is afterload?

A

Arterial pressure the ventricles have to overcome during contraction

47
Q

What is Starling’s law? (5)

A 
Increase venous return 
Increase preload (EDV)
Increase sacromere stretch
Increase force of contraction
Increase SV and therefore CO (even if HR constant)
48
Q

What increases stroke volume? (3)

A

Increased preload
Increased sympathetic input
Decreased afterload

49
Q

Give examples of muscular arteries

A

Aorta

Pulmonary artery

50
Q

What 2 factors facilitate venous return?

A
  • Respiratory pump

- Skeletal muscle pump

CARDIO (3 decks)

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