CVS SEM1

Question 1

What is an ECG?

Answer 1

A graphical representation of electrical potential difference changes against time of the myocardium throughout the cardiac cycle

Question 2

Where do you place the 6 chest electrode leads for an ECG?

Answer 2

V1- 4th IC space, right sternal edge
V2- 4th IC space, left sternal edge
V3- equidistant between V2-V4
V4- 5th IC space, midclavicular line
V5- equidistant between V4-V6, horizontal with V4
V6- midaxillary line on the same height as V4

Question 3

What are the components of the ECG complex?

Answer 3

P Q R S T and U

Question 4

What does the P wave signify?

Answer 4

Atrial contraction via depolarisation of both atria

Question 5

What’s the QRS complex?

Answer 5

This signifies the depolarisation and therefore contraction of the ventricles, so it’s when electrical activity spreads through the AVN, the bundle of His and the Purkinje fibres.

Question 6

What’s the first negative deflection?

Answer 6

The Q wave

Question 7

What’s the first positive deflection?

Answer 7

The R wave

Question 8

What’s the second negative deflection?

Answer 8

The S wave

Question 9

Does the absence of Q, R or S indicate arrhythmia?

Answer 9

No

Question 10

What’s the QT interval of an ECG?

Answer 10

Ventricular depolarisation and repolarisation

Question 11

What’s the ST segment?

Answer 11

An isoelectric segment between the end of QRS and the start of the T wave.

Question 12

What does elevated ST segment by more than 1mm indicate?

Answer 12

Myocardial infarction

Question 13

What does depressed ST segment by more than 1mm indicate?

Answer 13

Ischaemia

Question 14

What’s the ABC for emergency medicine?

Answer 14

A-airways
B-breathing
C-circulation

Question 15

What’s the SOCRATES checklist for patients presenting with chest pain?

Answer 15

Site
Onset
Character
Radiation
Association
Time
Exacerbating/ relieving
Severity

Question 16

What does myogenic mean?

Answer 16

Can generate electrical activity and contraction without the need for nerves

Question 17

Where are action potentials generated without nervous stimulation?

Answer 17

The sinoatrial node

Question 18

What’s phase 0 of myocyte contraction?

Answer 18

VGCC’s open and Ca2+ influxes into presynaptic terminals, causing depolarisation

Question 19

What’s If?

Answer 19

An ion channel specific to the sinoatrial node- a hyperpolarisation-activated Na+ channel

Question 20

What’s phase 3 of myocyte contraction?

Answer 20

Activation of VGKCs, leading to K+ movement out of the cell (efflux) down its concentration gradient, causing repolarisation

Question 21

What’s phase 4 of myocyte contraction?

Answer 21

An Na+ influx-induced depolarising slope via If

Question 22

What’s phase 2?

Answer 22

The plateau phase, where myocytes are refractive and so cannot fire more APs. This means there’s no twitching and 1 action potential will only produce 1 contraction, which is essential for proper ejection

Question 23

What’s the neurology behind increase in heart rate?

Answer 23

Noradrenaline released from sympathetic nerves acts at beta1-adrenoreceptors to have positive chronotropic and inotropic effects

Question 24

What’s the neurology of decrease in heart rate?

Answer 24

Acetylcholine is released from parasympathetic nerves and acts at M2 receptors on the SAN cells to have negative chronotropic effects

Question 25

What’s the composition of RBC membranes?

Answer 25

40% lipid, 50% protein, 10% carbohydrate

Question 26

What are the 3 layers of the RBC membrane?

Answer 26

Outer hydrophilic layer
Central hydrophobic layer
Inner hydrophilic layer

Question 27

What are the 4 functions of the membrane of RBCs?

Answer 27

Provide shape and structure to maintain the optimum surface area : volume ratio for efficient respiratory exchange
Provide deformability and elasticity so RBCs can pass through microvessels
Regulates intracellular cation concentration
Acts as the interface between the cell and its environment via membrane surface receptors