Ch26.6 Control Of Heart Beat

Question 1

What is heart beat controlled by

Answer 1

Pacemaker

Question 2

Pacemaker

Answer 2

Located in the right atrium

Sends a signal to the atria, which contract, and this then causes the ventricles to contracts

The brain can cause the pacemaker to speed up or slow down

Question 3

4 steps in heartbeat control

Answer 3

1. Pacemaker (SA node) signals to the atria to contract
2. Signal from SA node stimulates the AV node (located further down the right atrium)
3. AV node sends signal down the septum
4. Signal passed out to the walls of the ventricles, causing them to contract

Question 4

Other factors that affect heart beat control

Answer 4

-the brain and hormones change the rate at which the pacemaker operates

-excercise, temperature and emotion increase heart rate

-relaxation, sleep and alcohol decrease heart rate

Question 5

Stage 1 of heart beat

Answer 5

blood enters heart

-atria and ventricles are relaxed (diastole)
-blood enters atria
-all valves are closed

Question 6

Stage 2 heart beat

Answer 6

Blood is pumped from atria -> ventricles

-electrical impulses from pacemaker cause atria to contract (atrial systole)
-blood is pumped into ventricles
-bicuspid and tricuspid valves open
-vena cava and pulmonary veins close to stop blood entering atria
-semilunar valves remain closed

Question 7

Stage 3 heart beta

Answer 7

Blood leaves the heart

-atria relax
-impulses from AV node contract the ventricles (ventricular systole)
- blood is forced out of heart into pulmonary artery and aorta
-pressure closes bicuspid and tricuspid valves
-ventricles relax
-semilunar valves close
-vena cava and pulmonary veins open and cycle starts again

Question 8

Where is av node

Answer 8

In septum between right atrium and right ventricke