Structure and function of the heart Flashcards
Describe blood flow on the heart
The left and right ventricles pump the same volume of blood through the aorta and pulmonary artery.
describe cardiac output and its formula
Cardiac output is the volume of blood pumped through each ventricle per minute.
Cardiac output is determined by heart rate and stroke volume.
CO = HR x SV
describe diastole
During diastole, blood returning to the atria flows into the ventricles. In diastole the pressure in the arteries closes the semi- lunar valves.
Systole
Atrial systole transfers the remainder of the blood through the atrio-ventricular (AV) valves to the ventricles.
Ventricular systole closes the AV valves and pumps the blood out through the semi-lunar (SL) valves to the aorta and pulmonary artery.
Describe the SAN
The heartbeat originates from the heart itself. The auto-rhythmic cells of the sino-atrial node (SAN) or pacemaker, located in the wall S of the right atrium, set the rate at which the heart contracts.
The timing of cardiac muscle contraction is controlled by impulses from the SAN spreading through the atria causing atrial systole.
Describe the AVN
Impulses from the SAN travel to the (atrio-ventricular node) 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.
Describe ECGs
Impulses in the heart generate currents that can be detected by an a electrocardiogram
How does the medulla control the heart
The brain’s medulla regulates the rate of the sino-atrial node through the antagonistic action of the autonomic nervous system (ANS).
What does the sympathetic nerve do
releases noradrenaline which increases heart rate
what do parasympathetic nerves release
acetylcholine which decreases heart rate
Describe blood flow
Blood pressure is a measure of the force that your heart uses to pump blood around your body.
Blood pressure changes through the aorta during the cardiac cycl Pressure increases during ventricular systole and decreases during diastole
Describe how a sphygmomanometre detects blood pressure
An inflatable cuff stops blood flow, in the artery and deflates gradually.
The blood starts to flow (detected by a pulse) at systolic pressure The blood flows freely through the artery (and pulse not detected at diastolic pressure.
A typical blood pressure reading for a young adult is 120/80 mmHg.
describe hypertension
Hypertension is high blood pressure. A reading of 140/90 mmHg would be considered high blood pressure. Hypertension is a majo risk factor for many diseases including coronary heart disease.
