Nervous Control of the Cardiac Cycle

Question 1

what is the nervous system

Answer 1

the system whereby the brain and central nervous system send signals to muscles to tell them when to contract

(the heart is a muscle)

Question 2

what are the four main sections of the electrical impulse pathway

Answer 2

electrical impulses are passed in this order

• SA node
• AV node
• bundle of his
• purkinje fibres

Question 3

where is the SA Node

Answer 3

on top of the right atrium near the vena cava

Question 4

where is the AV node

Answer 4

along the septum near atria

Question 5

where is the bundle of his

Answer 5

along the septum

Question 6

where are the purkinje fibres

Answer 6

branch out around the outside of the muscular heart

Question 7

what is SA node short for

Answer 7

sinoatrial node

Question 8

what is the function of the SA node

Answer 8

‘the heart’s natural pacemaker’

triggers atrial systole (contraction)

Question 9

what iss AV node short for

Answer 9

atrioventricular node

Question 10

what is the AV node’s function

Answer 10

slows down the contraction of the ventricles (for a tenth of a second) to assure contraction occurs at the right time

Question 11

what is the function of the bundle of his

Answer 11

conducts electrical impulse from the central part of the heart to the base of the ventricles

Question 12

what is the function of the purkinje fibres

Answer 12

conducts electrical impulse back up the ventricle walls

Question 13

what are the steps of the cardiac cycle

Answer 13

1. atrial systole (both atria contract and blood is pushed into ventricles)
2. iso-volumetric contraction (pressure increases, valves are pushed through)
3. ventricular ejection (both ventricles contract, blood ejects into arteries)
4. iso-volumetric relaxation (pressure decreases, valves close)