Transport In Animals

Question 1

Describe the role of SAN and AVN in coordinating the cardiac cycle

Answer 1

• SAN pacemaker initiates heart beat
• SAN send impulse wave of excitation over atria walls
• AVN delay impulse
• AVN send impulse down septum/ bundle of his / purkinje fibres

Question 2

Blood in arteris has High hydrostatis pressure.

State how this hydrostatic pressure is generated in heart

Answer 2

-Contraction of ventricle wall

Question 3

Single Circulatory System

Answer 3

Blood passes through the heart once for each circulation

Question 4

Closed circulatory system

Answer 4

The blood is maintained inside vessels

Question 5

Describe how the action of the heart is initiated and coordinated

Answer 5

🐙SAN initiates excitation
🐙Wave of excitation spreads over Atrial wall
🐙Atria Contract/atrial systole
🐙Contraction is synchronised
🐙AVN delay impulse down Septum
🐙Purkinje fibres ventricle contract from apex

Question 6

During the electrical stimulation of the heart, there is a short delay between the excitation of the Atria and excitation of the ventricles.

Answer 6

So ventricles do not contract before they are full

So ventricles do not contract before atria are empty

So atria have time to empty before ventricles start to contract

Question 7

The Purkyne tissues carries the excitation wave down the septum to the apex of the heart.
Explain why the excitation wave is carried to the APEX

Answer 7

So that ventricular contraction start at apex
To push blood upwards

Systole for contraction
Contract from apex
Force all blood out heart