the heart beat

What is the automatic nervous system - what two divisions do they have - what relation do they have with eachother

Controls involuntary (subconscious) activities of internal muscles and glands

Sympathetic and parasympathetic

Antagonistic

If the heart an contract without external stimulation- it is described as what

Myogenic

Where is the SAN located and what is it and where is the AVN located

The sincoatrial nerve is located in the wall of the right atrium

From here the initial stimulus for contraction originates - determines the beat of the heart

AVN- lies between the atria

What are purkyne fibres nd the bundle of his

Specialised, rapid conducting cells in the heart’s ventricular walls and the bundle of his carry electrical signals down the centre of the heart

What part of the brain controls heart rate

The medulla oblongata

Which parts of the automatic nervous system speeds up or slows down heart rate- and what transmitters are released?

Parasympathetic - DECREASES HR - via releasing the acetylcholine neurotransmitter at their terminals

Sympathetic- INCREASES HR- via releasing the noradrenaline neurotransmitter at their terminals

Which type of receptors control responses to high CO2 levels and which control blood pressure

Chemoreceptors - respond to high CO2 levels

Baroreceptors - respond to changes in blood pressure

Where are both chemoreceptors and baroreceptors found

In the walls of the carotid artery and the walls of the aorta

Explain how the baroreceptors respond to changes in blood pressure

Describe the sequence of control for the basic heart rate

• a wave of electrical impulse spreads out from the SAN across both atria - causing them to contract (atrial systole)

• A layer of non conductive tissue (atrioventricular septum) prevents the wave crossing over to the ventricles

  • The impulse enters the AVN - which is delayed in order to allow full atrial emptying- and passes down the Bundle of His in the septum and into the Purkyne fibres

  • This causes ventricular systole - starting at the apex of the heart and spreading up over the ventricle walls (to make sure they are empty of blood and it has moved up into the arteries)

Describe the control by chemoreceptors