Unit 2- The Heart Flashcards
Describe the cardiac cycle
- Diastole, blood returning to the atria flows into the ventricles.
- Atrial systole transfers the remainder of the blood through the AV valve.
- Ventricular systole closes the AV valves and pumps the blood out through the SL valves to the aorta and pulmonary artery.
What causes the sound of the heart (lub-dub)?
The opening and closing of the AV and SL valves.
What is systole.
The contraction of the heart muscle. Blood is forced out the chambers.
What is diastole?
The relaxation of the heart muscle. The chambers fill with blood.
What is the SAN?
It is the pacemaker, that initiates each heartbeat, located in the wall of the right atrium. Sets the rhythm at which the heart contracts.
Describe the cardiac conduction system.
- The timing of cardiac muscle cell contraction is controlled by impulses from the SAN spreading through the atria causing atrial systole.
- They then travel to the AVN, located in the centre of the heart.
- Impulses from the AVN travel down fibres in the central wall of the heart and then up through the walls of the ventricles causing ventricular systole.
- This is followed by diastole.
Describe the role of the medulla in the cardiac conducting system.
The medulla regulates the rate of the SAN through the ANS through either a sympathetic nerve or a parasympathetic nerve.
What does a sympathetic nerve do? S for stress!
A sympathetic nerve releases noradrenaline which increases heart rate.
What does a parasympathetic nerve do? P for peace!
A parasympathetic nerve releases acetylcholine, and decreases heart rate.
What machine measures heart rate?
ECG. (Electrocardiogram).
What is the typical blood pressure for a young adult?
120/80 mmHg.
What is high blood pressure?
Hypertension, a major risk factor for many diseases including coronary heart disease.
