ECG

Question 1

what percentage of deaths in the US are due to coronary disease?

Answer 1

50%

Question 2

what is the action of the right atrium and ventricle?

Answer 2

pump venous blood from vena cavae to the pulmonary circulation

Question 3

what is the action of the left heart?

Answer 3

pump blood from pulmonary system to high pressure systemic circulation

Question 4

what allows the heart to continue to beat even after all nerves are cut

Answer 4

specialized pacemaker cells

Question 5

what are the three types of cardiac tissue

Answer 5

1. myocardium (atrial and ventricular)
2. specialized tissue of the conduction system
3. inert exoskeleton that electrically separates atrial and ventricular myocardium

Question 6

characteristics of myocardium

Answer 6

connection between two muscle cells occur at z line called intercalated disk - action potential travels easily between cells because of this (functional syncytium

Question 7

what makes up the conduction system in the heart

Answer 7

system of excitation and rapid conduction of depolarization thru heart (s-a node, a-v node, bundle of his, bundle branches, and purkinje network)

Question 8

what is the purpose of the exoskeleton

Answer 8

prevents depolarization from spreading cell to cell directly from atrial to ventricle - wave of depolarization to spread from atrial to ventricle is through A-V node to bundle of his

Question 9

define prepotential

Answer 9

unstable resting membrane potential of pacemaker tissue causes slow depolarization between action potentials

Question 10

what happens between the prepotential stage and a slow response action potential

Answer 10

gradual influx of sodium and calcium ions - and possible slow efflux of potassium from cell all leads to gradual increase of membrane potential until threshold