Physiology (conduction Of The Heart)

Question 1

What does the SAN do and what does it cause ?

Answer 1

• The Sino Atrio Node (SAN) is the heart’s pacemaker and sends out an electrical impulse
• causes the stria to contract

Question 2

What happens when the atria contracts ?

Answer 2

forces the blood into the ventricles

Question 3

What does the AVN do ?

Answer 3

It sends out a second electrical impulse

Question 4

What does the second impulse do and what does it cause ?

Answer 4

• travels down to the Bundle of His, which delays the impulse for 0.1s
• this causes the atria to empty of blood

Question 5

What are the two stages of the heart ?

Answer 5

• systolic
• Diastolic

Question 6

When does the diastolic phase occur ?

Answer 6

• when the heart relaxes after contraction
• the atria passively fills with blood
• the ventricle passively fills with blood because of the increase in pressure in the atria

Question 7

What occurs during the systolic phase ?

Answer 7

• The heart contracts
• the increase in pressure in the atria forces the blood into ventricles.
• the increased pressure in the ventricles forces the blood to the body (aorta) and the lungs

Question 8

What are the 3 mechanisms of venous return ?

Answer 8

• Muscle pump
• one-way valve
• respiratory pump

Question 9

How does the muscle pump help venous return ?

Answer 9

This is where the muscles contract, which squeezes the
veins and force the blood towards the heart

Question 10

How do one way valves help venous return ?

Answer 10

Veins contain one-way valves that prevent the back flow of
blood

Question 11

How does respitory pump help with venous return ?

Answer 11

The chest size increases, which squeezes the veins and
forces the blood back towards the heart

Question 12

What does the impulse that’s delayed for 0.1 second do ?

Answer 12

• travels down to the Purkinjie fibres
• which cause the ventricles to contract
• This forces blood out of the heart.