Practise heart questions by identifying chambers, valves and vessels, interpreting cardiac-cycle pressure graphs and tracing SAN, AVN and Purkyne conduction.
Control of heartbeat is myogenic. This means the electrical activity controlling the rhythm of a regular heartbeat begins in the heart muscle itself.
Atrial fibrillation (AF) is an abnormal heart rhythm that causes rapid and irregular contractions of the atria. Untreated cases of AF can lead to a stroke.
A stroke is caused when a small blood clot, often forming in the left atrium, is carried by the blood to the brain where it blocks a small artery and leads to brain damage.
List all of the structures through which a blood clot in the left atrium must travel to reach the blood vessels supplying the brain.
The structures must be listed in the correct sequence.
A common cause of AF is when a small group of muscle cells in the wall of the left atrium starts to send out electrical impulses to the surrounding heart muscle cells.
Explain how the control of heartbeat by the sinoatrial node can be disrupted by AF , resulting in rapid and irregular atrial contractions.
In a double circulatory system, blood passes through the heart twice in one complete circuit of the body. The complete circuit consists of the pulmonary circulation and the systemic circulation.
Fig. 4.1 is a diagram of a vertical section through the mammalian heart. The differences in the thickness of cardiac muscle in the walls of the four chambers of the heart are shown.
Fig. 4.1
Explain, with reference to their functions, the difference in the thickness of the walls of the left ventricle and right ventricle of the heart.
During one cardiac cycle:
- blood enters the heart from the lungs and from the rest of the body
- blood leaves the heart to be transported to the lungs and to the rest of the body.
One phase of the cardiac cycle is ventricular diastole (ventricular relaxation). A number of events occur in the heart during this phase.
Outline and explain the events that occur in the heart during ventricular diastole.
Blood arriving in the lungs from the heart is oxygenated as it passes through the pulmonary capillaries.
Sickle-shaped red blood cells are present in a person with sickle cell anaemia. These cells have a very high quantity of abnormal (sickle cell) haemoglobin and take up and transport less oxygen than red blood cells containing normal haemoglobin.