2. Physiology

Question 1

What is the job of the cardiovascular system?

Answer 1

Transport of O2 and CO2
Nutrients
Metabolites
Hormones
Heat

Question 2

What controls the resistance to vascular beds?

Answer 2

Arterioles- elastic and have a contractile wall

As oppose to arteries which do not control vascular beds, they are more muscular in structure

Question 3

How much blood is stored in the venous system?

Answer 3

75%- used as capacitance vessels

Question 4

How do cardiac muscle cells communicate with one another?

Answer 4

Electrically connected via gap junctions
Physically connected by desmosomes
These form intercalated discs

Question 5

What controls the strength of contraction of the heart?

Answer 5

Calcium as it does not fully saturate troponin.

Question 6

How do pacemaker cells act a pacemaker?

Answer 6

They have unstable resting membrane potentials meaning they can spontaneously contract

Question 7

How does potassium effect the heart?

Answer 7

Hyperkalemia- fibrillation and heart block

Hypokalemia-decreased heart rate and force of contraction

Question 8

How does calcium effect the heart?

Answer 8

Hypercalceamia- increase HR and force of contraction

Hypocalcemia- decreased hr and force of contractions (calcium channel blockers)

Question 9

Where are pacemaker cells found?

Answer 9

Sino-atrial node
Atrio ventrocular node
Bundle of His/Perkinje fibres

Question 10

Explain the action potential of a pacemaker cell?

Answer 10

Sodium brings the cell to a threshold that opens the voltage gated calcium ion channels

This creates an action potential.

Potassium gated voltage channels occur at a higher level. This brings the voltage down and is the refractory period.

Question 11

What limb lead is used to interpret ECG’s?

Why?

Answer 11

SLL II- follows the line of maximal depolorisation when looking at conduction to the left leg in respect to the right arm.

Question 12

Explain the components of an ECG trace

Answer 12

P wave is caused by atrial depolorisation
QRS complex is caused by ventricular depolorisation
T wave is caused by ventricular repolorisation

Question 13

What is the normal timings of an ECG trace

Answer 13

PR interval- 0.12-0.2 sec
QRS- 0.08s
QT interval- 0.42sec

Question 14

What is the benefit of

• The augmented limb leads
• The precordial (chest) leads

Answer 14

augmented leads- gives you further information in the vertical plane

hows progression of the depolorisation on the front of the heart

Question 15

How do you calculate the rate of an ECG

Answer 15

Count the R waves over 30 large boxes

Question 16

What is this STEMI malarkey?

Answer 16

STEMI- ST elevated myocardial infarction- bad

NSTEMI- non ST elevated myocardial infarction

Question 17

What is meant by S1 and S2?

Answer 17

S1- blood hits atrioventricular valves

S2- blood hits semilunar valves

Question 18

What sound indicates mitral and tricuspid regurgitation or aortic/pulmonary stenosis

Answer 18

lub whoosh dub

Question 19

What sound indicates stenosis of mitral/tricuspid or regurgitation through the aortic/pulmonary valve

Answer 19

lub dub whoosh

Question 20

How does the sympathetic nervous system affect heart rate (be specific)

Answer 20

release noradrenlaine and adrenaline that acts on B1 receptors on the sinoatrial node

This increases heart rate

Question 21

How does parasympathetic system affect heart rate?

Answer 21

Vagus nerve releases acetyl choline which acts upon muscarinic receptors

This decreases heart rate

Question 22

How does end diastolic volume affect stroke volume?

Answer 22

Increases venous return therefore increasing stroke volume

Question 23

How is stroke volume affected by peripheral resistance?

Answer 23

If peripheral resistance increased then contractility increased, reducing the capacity for stroke volume

Question 24

What is stroke volume a synonym for?

Answer 24

Contractility

Question 25

How does the sympathetic system effect stroke volume?

Answer 25

Noradrenaline and adrenaline acts on B1 receptors
in the mycocytes

Gives stronger but shorter contractions

Question 26

How does the parasympathetic system effect stroke volume?

Answer 26

Little effect as the vagus nerve doesn’t innervate the ventricular muscle