Cardiovascular Physiology 2-3

Question 1

Electrocardiogram 3 leads

Answer 1

-/- right arm
+/+ left leg
+/- left arm

Question 2

P wave

Answer 2

Beginning of atrial contraction (systole), wave of depolarisation travels from the SA node towards the AV node

Question 3

QRS complex

Answer 3

Beginning of ventricular contraction, the time for depolarisation to spread. Covers the wave that would be atrial repolarisation.

Question 4

T wave

Answer 4

Ventricular repolarisation

Question 5

P-Q interval

Answer 5

The time for the electrical excitation of the atria to reach the ventricles, usually slows through the AV node due to thicker fibers. (0.16 sec normal).`

Question 6

Q-T interval

Answer 6

Duration of ventricular contraction (0.35 sec normal)

Question 7

Einthoven’s triangle

Answer 7

Heart at the center, 3 electrodes from arms to legs.

Question 8

Causes of cardiac arrhythmias

Answer 8

abnormalities in the rhythmicity conduction system of the heart:
- abnormal pacemaker activity
- ectopic pacemakers
- blocks
- abnormal pathways for impulses
- spontaneous generation of spurious impulses.

Question 9

Sound 1

Answer 9

Closure of the AV valves

Question 10

Sound 2

Answer 10

Closure of the pulmonary and aortic valves

Question 11

S3 and S4

Answer 11

Early ventricular filling and atrial contraction

Question 12

Atrial systole

Answer 12

From P-Q, atrial pressure remains low and ventricular pressure increases until the mitral valve closes.

Question 13

Ventricular systole

Answer 13

Isovolumic contraction as blood volume remains constant until the pressure is greater than that of the aorta, opening the aortic valve.

Question 14

Isovolumetric phases

Answer 14

Contraction - when the mitral valve has closed, until the aortic valve opens.
Relaxation - when the aortic valve closes, until the mitral valve reopens.

Question 15

Stroke volume

Answer 15

amount of blood pushed into systemic circulation by ventricular contraction.
EDV - ESV, usually = 70mL

Question 16

Cardiac output

Answer 16

= heart rate x stroke volume

Question 17

Ejection fraction

Answer 17

The fraction of blood that was ejected during cardiac systole.
= (EDV - ESV) / EDV ~ 50-70% but goes up with exercise.
Indicates cardiac contractility.

Question 18

Parasympathetic innervation of the SA/AV node

Answer 18

Sparse by releasing ACh on to muscarinic receptors.
Increases K efflux, and decreases Ca influx to HYPERPOLARISE the cell.

Question 19

Sympathetic innervation of the SA/AV node

Answer 19

Rich by release NE on to β1 adrenergic receptors.
Increases both NA and CA influx to DEPOLARISE the cell.

Question 20

Resting condition

Answer 20

Parasympathetic discharge dominates because ACh suppresses sympathetic activity and the release of NE from nearby nerve endings.

Question 21

Atropine

Answer 21

Muscarinic receptor antagonist - blocks parasympathetic effects and increases heart rate.

Question 22

Propranolol

Answer 22

β-adrenergic receptor antagonist that blocks sympathetic effects and decreases heart rate.

Question 23

Extrinsic control of cardiac output

Answer 23

Sympathetic innervation that increases[ both contractility and venous return.

Question 24

Frank-Starling law

Answer 24

Force (indicated by stroke volume) generated by cardiac muscle is proportional to initial length of the cardiac muscle fibers.

Question 25

Preload

Answer 25

Workload imposed on cardiac muscle before the heart begins to contract.

Question 26

Intrinsic control of stroke volume

Answer 26

Venous return is defined by the compression of veins by the skeletal muscle pump, and by breathing of the respiratory pump. This determines EDV which influences SV

Question 27

Extrinsic control of stroke volume

Answer 27

Sympathetic innervation of veins may increase constriction, increasing venous return and EDV, therefore affecting SV.

Question 28

Contractility

Answer 28

Ability of the cardiac muscle to contract and generate force for the pumping function.

Question 29

Influencers of contractility

Answer 29

More intracellular Ca2+ increase the force of contraction, catecholamines increase the transport of Ca2+ into the cell

Question 30

How do catacholamines mediate heart rate?

Answer 30

Phosphorylation sarcolemmal Ca2+ channels to increase flow, and bind to β1adrenergic receptors increasing phosphorylation of phospholamban and Troponin I to induce relaxation. Accelerates both contraction and relaxation of the heart.

Question 31

After load

Answer 31

Workload imposed on cardiac muscle after the contraction has begun, no effect on cardiac output.

Question 32

Heart failure

Answer 32

Cardiac output is insufficient to meet the needs of the body in the presence of normal venous return.

Question 33

Continuous myocardial oxygen demand

Answer 33

Heart constantly need ATP and is uses a wide range of substrates to use this, mostly using fatty acid oxidation 60%, and glucose oxidation 35-40%.

Question 34

Factors associated with myocardial oxygen demand

Answer 34

Wall stress, heart rate, contractility

Question 35

Factors associated with myocardial oxygen supply

Answer 35

o2 content, coronary blood flow (perfusion pressure, vascular resistance)

Question 36

Myocardial Ischemia

Answer 36

Depending on the site of the blockage, a wide range of tissues may be deprived of a blood supply.