The structure and function of the heart
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Through what vessel does de oxygenated blood return to the right atrium?
Vena cava
What are the four chambers of the heart
• left and right atria • left and right ventricles
Explain the route of blood flow from it being brought back to the heart by the vena cava, to being pumped around the body by the aorta
• deoxygenated blood enters the right atrium via the vena cava • blood passes into right ventricle and leaves the heart through the pulmonary artery where it travels to the lungs to be oxygenated • oxygenated blood returns to heart via pulmonary veins • blood then flows from left atrium to left ventricle and out to the rest of the body via the aorta
Why is the left ventricle thicker than the right ventricle?
The left ventricle has to pump blood all around the body whereas the right ventricle only pumps blood to the lungs
What are the two types of valves found in the heart?
• Atrioventricular valves (AV) • Semi-lunar valves
where are the AV valves found and what is their function?
• found between the atria and ventricles • prevent back flow of blood from the ventricles to the atria
Where are the semi lunar valves found and what is their function?
• between right ventricle and pulmonary artery • between left ventricle and aorta prevent back flow of blood into the ventricles
what is heart rate?
number of heartbeats that occur per minute
What is the stroke volume?
The volume of blood pumped out of each ventricle per heartbeat
What is the cardiac output?
The volume of blood pumped out of each ventricle per minute
How is the cardiac output calculated?
CO= HR x SV CO= cardiac output HR= heart rate SV= stroke volume
What is the cardiac cycle?
the processes of systole and diastole which occur during one complete heartbeat
What occurs during diastole?
• period of relaxation for the heart - no contraction • blood returns to the atria • atrial pressure begins to be greater than ventricular pressure • blood begins to enter the ventricles
What occurs during atrial systole?
Atria contract and send remaining blood into the ventricles
What occurs during ventricular systole?
contraction of the ventricles pumps blood into the aorta and pulmonary artery
What part of the heart sets the heart rate?
Sino atrial node
Explain the pathway of an electrical impulse after it is produced by the SA node
• spreads across the muscle cells of the atria causing atrial systole • Impulse picked up at the atrioventricular node • Impulse passes from AVN to bundle of conducting fibres which divides into two branches • Impulse spreads to the ventricular muscle cells via these branches, leading to ventricular systole
Where is the Sino atrial node located?
The upper part of the wall of the right atrium
Where is the AV node located?
At the base of the atria
What can be used to record the electrical activity of the heart
An electrocardiogram (ECG)
Which part of the brain is involved in regulating the rate of the Sino atrial node?
The medulla
What are the two branches of the autonomic nervous system?
sympathetic and parasympathetic
What do the sympathetic and parasympathetic nervous systems do to the heart rate?
• sympathetic system increases heart rate • parasympathetic system decreases heart rate they are antagonistic of each other
What neurotransmitter do sympathetic nerves release to increase heart rate?
Noradrenaline