7.3 Control of Heart Rate Flashcards
What does it mean that the heart muscle is myogenic?
It can contract without external nervous stimulation.
What is contraction of cardiac muscle initiated by?
Initiated by small changes in the electrical charge of cardiac muscle cells.
When cells have a slight positive charge on the outside what are they said to be?
Polarised.
When a charge is reversed in a cell what is this called?
Depolarised.
What happens when there is a change in polarity?
A wave from cell to cell and caused the cells to contract.
Where does depolarisation start?
Sinoatrial node (SAN).
Where is the sinoatrial node?
Located in the wall of the right atrium, beneath the opening to the superior vena cava.
What is the Sinoatrial node also known as?
A pacemaker.
What does SAN do?
Generates an electrical impulse which spreads across the right and left atria causing them to contract at the same time.
Where does the impulse also travel to after the atria?
To the Atrioventricular node (AVN)
After it reaches the atrIoventricular node (AVN) where is the impulse conducted to?
The ventricules after a delay.
Why is the impulse delayed?
The delay ensures that the atria have finished contracting, and that the ventricules have filled with blood before they contract.
After this delay where does the signal reach? What do they do?
Purkyne Fibers. Large muscle fibres that conduct impulses rapidly to the apex (tip) of the ventricles.
What is the Bundle of His?
Right and left bundles of fibers.
What do the Purkyne Fibres do in the ventricles?
Divide into smaller brances and penetrate the ventricular muscle. The brances carry the impulse to the inncer cells of the ventricles and spreads.
