9.8

• The Sinoatrial node (SAN) is located within the wall of the right atrium.
• The Atrioventricular node (AVN) is located near the lower end of the right atrium in the wall that separates the two atria.
• The Sinoatrial node (SAN) initiates a wave of depolarisation (WOD) which spreads across both atria, this is known as atrial systole.
• A layer of fibrous, non-conducting tissue delays impulse while ventricles fill and valves close.
• The Atrioventricular node (AVN) conveys the WOD down the septum via the Bundle of His, which branches into Purkinje fibres along the ventricles.
• The Atrioventricular node (AVN) causes the ventricles to contract from the apex upwards.
• The Autonomic nervous system (ANS) is a system that controls the involuntary actions of glands and muscles, it is divided into two subdivisions: sympathetic and parasympathetic.
• The receptors involved in changing heart rate are located in the Autonomic nervous system (ANS), their location varies depending on the individual.
• Baroreceptors detect changes in blood pressure and send more impulses to the cardioinhibitory centre in the medulla oblongata.
• Chemoreceptors stimulate the release of acetylcholine, which decreases heart rate.
• Baroreceptors stimulate the release of noradrenaline, which increases heart rate and strength of contraction.
• More impulses to the SAN are sent via the sympathetic nervous system.
• Chemoreceptors detect a decrease in pH and send more impulses to the cardioacceleratory centre of the medulla oblongata.
• Chemoreceptors detect a decrease in blood pressure and send more impulses to the cardioinhibitory centre of the medulla oblongata.
• Baroreceptors detect changes in pH and send more impulses to the cardioacceleratory centre of the medulla oblongata.
• Chemoreceptors stimulate the release of noradrenaline, which increases heart rate and strength of contraction.
• More impulses to the SAN are sent via the parasympathetic nervous system.
• Baroreceptors stimulate the release of acetylcholine, which decreases heart rate.
• Chemoreceptors detect an increase in CO2 concentration and send more impulses to the cardioacceleratory centre of the medulla oblongata.