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Cardiology > Cardiac Physiology > Flashcards

Cardiac Physiology Flashcards

1
Q

What is stroke volume?

A

The amount of blood pumped out of the ventricle in one beat

End diastolic volume- end systolic volume

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2
Q

Preload

A

Forces applied before contraction- aka the filling volume or venous return

Preload increases cardiac
Output

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3
Q

Afterload

A

Resistance to ventricular contraction- dictates the amount of work that must be done

Afterload decreases cardiac output

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4
Q

What factors determine cardiac output?

A

Preload (increases)
Contractility (increases)
Afterload ( decreases)

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5
Q

What influences blood pressure?

A

Cardiac output

Systemic vascular resistance (vasoconstriction or vasodilation)

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6
Q

Ejection fraction

A

% of blood in a ventricle that is expelled in one contraction

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7
Q

Isovolumetric contraction

A

When the heart is contracting with no change in volume- ie before any valves open. Also happens as isovolumetric relaxation

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8
Q

Approach to ECG

A 
Rate- Brady, tachy, normal
Rhythm- regular, irregular, 
P waves- present? Same? Connected to QRS
PR interval
QRS
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9
Q

P wave means….

A

Atria is depolarizing

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10
Q

PR interval means…

A

AV node is depolarizing

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11
Q

QRS means…

A

Ventricles are depolarizing

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12
Q

T wave means

A

Ventricles are repolarizing ( goes in opposite direction)

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13
Q

What is the role of calcium in cardiac action potentials?

A

Depolarization opens voltage gated calcium channels
Ca influxes into the cell
Triggers further release of stored calcium from sarcoplasmic reticulum
Ca binds troponin, exposes myosin binding sites on actin
After contraction actively transported OUT by SERCA

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14
Q

What is the normal path of blood though the heart?

A 
Right atrium
Right ventricle
Pulmonary artery to lungs
Pulmonary veins from lungs
Left atrium 
Left ventricle
Aorta (brachiocephalic trunk, common carotid, left subclavian)
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15
Q

What is the order of normal conduction in the heart?

A

Sinus node to AV node to bundle of his to left and right bundle branches to Purkinje fibres

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16
Q

What is axis?

A

The average direction of electrical activity through the heart-

Look at lead one and aVF- should both be positive if normal left axis is present

17
Q

What are the determinants of myocardial oxygen supply?

A
  1. Coronary anatomy ( any stenosis?)
  2. Coronary perfusion pressure
  3. Heart rate
  4. Oxygen content of blood
18
Q

What determines myocardial oxygen demand?

A
  1. Heart rate (faster=higher)
  2. Pressure (more wall tension=more demand)
  3. Radius (more wall tension=more demand)
19
Q

When does LV myocardial perfusion occur?

A

Occurs in diastole because pressure gradient will drive flow then

20
Q

What types of end organ receptors do parasympathetic nerves have?

A 
Nicotinic
Muscarinic (5 types)

Activated by actylcholine

21
Q

What end organ receptors does the sympathetic nervous system have?

A

Adrenoreceptors- alpha or beta

Respond to noradrenaline

22
Q

What types of nervous receptors are on the heart and what effects do they have?

A

Muscarinic type 2: bradycardia

Adrenoreceptor beta 1: tachycardia

23
Q

What nerve receptors are in the airways and how do they work?

A

Muscarinic 3: promotes broncocontstriction

Beta 2: responds to CIRCULATING adrenalin, bronchodilation

24
Q

Characteristics of the sympathetic nervous system?

A
  1. Long post-ganglionic neuron
  2. Noradrenaline as signal at neuromuscular junction
  3. Binds to adrenoreceptors- alpha or beta subclasses
25
Q

Characteristics of the parasympathetic nervous system?

A
  1. Very short post-ganglionic neuron
  2. Acetylcholine as signal
  3. Binds to nicotinic or muscarinic receptors
26
Q

What types of receptors are on the heart and what functions do they elicit when stimulated?

A
  1. Muscarinic type 2 (M2): bradycardia

2. Beta-1 (B1): tachycardia

27
Q

What types of receptors are in the airways and what functions do they elicit when stimulated?

A
  1. M3: cause airway CONSTRICTION

2. B2: cause relaxation (BLOOD noradrenaline)

28
Q

What is an isoelectric lead?

A

One in which the charge is travelling PERPENDICULARLY.

Small but equal up down deflection

29
Q

What defines:

  1. Right axis deflection?
  2. Left axis deflection?
  3. Extreme axis deflection?
A
  1. down in 1, up in aVF
  2. Down in II and up in I
  3. Down in aVF and 1
30
Q

Which direction does the wave of depolarization travel?

A

Inside to outside- from endocardium to epicardium

31
Q

Why is LBBB important to identify?

A
  1. Typically associated with some form of heart disease

2. Can interfere with identification of MI etc

Cardiology (20 decks)

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