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Phys, pharm > The heart > Flashcards

The heart Flashcards

1
Q

What is the protective fluid filled sac around the heart ?

A

The pericardium

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2
Q

What does right atria receive?

A

Deoxygenated systemic venous return

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3
Q

Function of right ventricle

A

Pushes blood to pulmonary circulation for oxygenation

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4
Q

What does the left atrium receive?

A

Oxygenated blood from pulmonary circulation

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5
Q

Function of left ventricle

A

Pumps oxygenated blood under high pressure to brain and body

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6
Q

Name what attaches atrioventricular valves to the cardiac wall

A

Chordae tendinea
Papillary muscles

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7
Q

Structure of the heart wall

A
  1. epicardium
  2. myocardium
  3. endocardium
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8
Q

Function of epicardium

A

Reduces friction with pericardial fluid + coronary blood

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9
Q

Specialisation of myocardium

A

Encased in collagen fibres

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10
Q

Specialisation of endocardium

A

Smooth muscle

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11
Q

Function of a conducting cell

A

Rapidly spread action potentials

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12
Q

Name the heart conducting cells

A

Purkinje system
Sinoatrial node
AV node
Bundle of his
Atrial internodal tracts

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13
Q

Function of contractile cells

A

Ap leads to contraction causing generation of force or pressure

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14
Q

What is a myocyte?

A

Muscle cells in the heart

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15
Q

What are the 5 stages of a cardiac action potential?

A

0 - Upstroke of action potential
1- Rapid depolarisation
2- Plateau phase
3- Repolarisation
4- Electrical diastolic phase

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16
Q

What are the 4 time dependent and voltage gated currents?

A

Na+
Ca+
K+
Pacemaker current

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17
Q

Describe the Na+ current

A

Rapid depolarising phase
Ap in atrial and ventricular muscle and purkinje fibres

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18
Q

Which is the largest current in the heart?

A

Na+ current

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19
Q

Describe Ca+ current

A

Rapid depolarising phase
SAN, AVN
Triggers contraction in all cardiomyocytes

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20
Q

Describe K+ current

A

Repolarises all cardiomyocytes

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21
Q

Describe the pacemaker current

A

Pacemaker activity of SAN, AVN and purkinje fibres

22
Q

How does an action potential propagate in cardiac cells?

A

Synchronised ventricular contraction
Depolarisation flows from one cell to another (syncytium) via gap junctions

23
Q

What is a myocardium?

A

A branched muscle fibre cell connected by intercalated discs

24
Q

Describe the cell structure of a myocardium

A

Intercalated disk is part of the sarcolemma
Gap junctions
Desmosomes anchor fibres together

25
Q

What are t tubules formed from?

A

Deep invaginations in the sarcolemma

26
Q

Describe the events after T tubule depolarisation

A

T tubule depolarisation triggers calcium release in the cell core (near z line)
Calcium is released from sr
Actin and myosin are able to interact and a large instantaneous force occurs

27
Q

What is a dyad?

A

Sarcoplasmic reticulum and T tubules

28
Q

What is coupled to an L type T tubule Ca2+ channel?

A

Ca2+ release in cardiomyocytes and VSMC

29
Q

What is a T type Ca2+ channel coupled to ?

A

Pacemaker and conducting cells

30
Q

What does Cytosolic calcium activate?

A

Activates a channel on the sarcoplasmic reticulum which causes calcium induced calcium release

31
Q

What is the effect of a global increase in calcium concentration?

A

Calcium binds troponin C and releases troponin I which inhibits actin

32
Q

What is the cardiac depolarisation sequence?

A

SAN depolarisation is spontaneous ->
AP propagates from left to right side of the heart (rate of 60-100/min) via gap junctions->
Reaches AVN ->
Fibrous AVN ring prevents the signals from propagating AVN tissue ->
AP is passed to ventricular muscle (via HIS purkinje fibre system)

33
Q

What is the primary pacemaker in the cardiac depolarisation sequence?

A

SAN

34
Q

What is the secondary pacemaker in the cardiac depolarisation sequence?

A

AVN

35
Q

Where in the heart is the sinoatrial node?

A

In the right atrium

36
Q

Where in the heart is the atrioventricular node?

A

In the right atrium

37
Q

Describe the cardiac cycle

A
  1. Atrial systole
  2. Isovolumetric ventricular contraction
  3. Rapid ventricular ejection
  4. Reduced ventricular ejection
    5 . Isovolumetric ventricular relaxation
  5. Rapid ventricular filling
  6. Reduced ventricular filling
38
Q

What happens in Atrial systole?

A

Atria are depolarised
Mitral and tricuspid valves open
Ventricles further fill
Contraction causes an increase in p

39
Q

What happens in isovolumetric ventricular contraction?

A

Ventricular p > atrial p
Purkinje fibres electrical activation cause ventricular contraction causing large increase in p
Mitral/tricuspid valve closes

40
Q

What happens in rapid ventricular ejection?

A

Ventricular p > aortic p
SLV opens
Stroke volume ejection
Ventricular volume decreases
Atrial p increases

41
Q

What happens in reduced ventricular ejection?

A

Final blood ejection from ventricles due to contraction
Ventricular repolarisation as ventricular p decreases
Arterial volume decreases

42
Q

What happens in isovolumetric ventricular relaxation?

A

Occurs when ventricles are fully repolarised Ventricles relax causing ventricular p decrease
Ventricular p > arteriole p
All valves are closed
Ventricular volume remains constant
Atrial p increases
Arteriole v decreases

43
Q

What happens in rapid ventricular filling?

A

Atrial p > ventricular p
Mitral and tricuspid valves open
Blood enters the ventricles from atria

44
Q

What happens in reduced ventricular filling?

A

Remaining blood enters the ventricle

45
Q

What does an ECG measure?

A

The movement of external portion of ions

46
Q

What does the P wave show?

A

Atrial depolarisation

47
Q

What does the PR interval show?

A

AVN conduction as it reflects initial depolarisation of atria to ventricles

48
Q

What does QRS show?

A

Depolarisation of ventricles

49
Q

What does T wave show?

A

Repolarisation of ventricles

50
Q

What does atrial tachycardia display on ECGs?

A

P wave masks T wave due to speed

51
Q

What does atrial fibrillation display on ECGs?

A

P wave isn’t presented

52
Q

How does ventricular fibrillation display on ECGs?

A

No sequenced filling of ventricles so no sequenced pattern

Phys, pharm (31 decks)

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