3.6.1.3 Control of Heart Rate Flashcards
Where is the sinatorial node found?
At the connection of the right atrium and the superior vena cava
Where is the atrioventricular node found?
Between the walls of the two ventricles next to the semi lunar valves
What can be increased or decreased in the heart?
The heart rate
The force of ventricular contractions
The stroke volume
What does the sinatorial node do?
Causes the heart to speed up or slow down
Causes the atria to contract
What does the atrioventricular node do?
Carries impulses from the sinatorial node down to the bottom of the heart
Ventricles contract from the base
What determines the speed of the heart?
Receptors which detect activity
What connects with the sinatorial node?
The brain
What are the receptors involved in controlling the heart rate?
Chemoreceptors: detect changed in the pH due to increasing carbonic acid
Stretch receptors in the muscles
Stretch receptors which monitor blood pressure
What are the two receptors connecting the heart and the brain?
Vagus and accelerans
What is the process of controlling heart rate?
A wave of electrical excitation spreads out from the sinatorial node across both atria, causing them to contract
A layer of non conductive tissue between the atria prevents the wave from crossing to the ventricles
The wave of excitation enters the atrioventricular node which lies between the atria
The atrioventricular node, after a short delay, conveys a wave of electrical excitation between the ventricles along a series of specialised muscle fibres called Purkyne tissue which makes up a structure called the bundle of His
The bundle of His conducts the wave through the atrioventricular septum to the base of the ventricles, where the bundle branches into smaller fibres
The wave of excitation is released from the Purkyne tissue, causing the ventricles to contract quickly at the same time, from the bottom of the heart upwards
