Key Area 6- Structure and Function of the Heart Flashcards
What are the four chambers of the heart?
. Right atrium
. Right ventricle
. Left atrium
. Left ventricle
What are the four vessels of the heart?
. Vena cava
. Pulmonary artery
. Pulmonary vein
. Aorta
What are the four valves of the heart?
. Right atrio-ventricular valves
. Right semi-lunar valves
. Left atrio-ventricular valves
. Left semi-lunar valves
What is the pathway of blood through the heart?
. Vena cava (blood returning from the body)
. Right atrium
. Right atrio-ventricular valves
. Right ventricle
. Right semi-lunar valves
. Pulmonary artery
. LUNGS ( site of gas exchange)
. Pulmonary vein
. Left atrium
. Left atrio-ventricular valve
. Left ventricle
. Left semi-lunar valve
. Aorta
. Blood to the body
Why the wall of the left ventricle thicker than the wall of the right ventricle?
Because the left ventricle has to pump blood to the whole body, whereas the right ventricle only has to pump blood to the lungs
What do AV valves prevent?
They prevent the back flow of blood from ventricles to atria
What do SL valves?
They prevent the back flow of blood into the ventricles from the pulmonary and aorta arteries
What is a systole?
The SL valves open during ventricular allowing blood into the arteries
What is a diastole?
The SL valves close when arterial pressure exceeds ventricular pressure, and the muscle relaxes
What is the formula for cardiac output?
Cardiac output (CO) = Heart Rate (HR) x Stroke Volume (SV)
What is heart rate (Pulse)?
The number of heartbeats that occurs per minute
What is stroke volume?
The volume of blood expelled by each ventricle on contraction. (The stronger the contraction, the greater the stroke volume)
What is cardiac output?
The volume of blood pumped out of a ventricle per minute (It can be determined by heart rate and stroke volume hence formula)
What is the cardiac cycle?
The pattern of contraction (systole) and relaxation (diastole) shown by the heart during one complete heartbeat
What is the average cardiac cycle?
0.8 seconds, which is based on a heart rate of 75 beats per minute
What happens during diastole?
. The blood returning to the atria flows into the ventricle and is under high pressure in the arteries
. This causes the SL valves to close, preventing the back flow of blood
. Pressure in the atria and ventricles is lowered by the relaxation of the cardiac muscles
. The coronary arteries fill during diastole
What happens during artrial systole?
. It transfers the remainder of the blood through the AV valves to the ventricles
. Blood under low pressure flows into the atria from the pulmonary veins and vena cava
. As the atria fill, the pressure of blood against the AV valves pushes them open therefore blood leaks into ventricles
.The atria walls contract, forcing blood into ventricles
.The SL valves remain closed
What happens during ventricular systole?
. It closes the AV valves and pumps the blood out through the SL valves to the aorta and pulmonary artery
. The ventricles contract from the bottom of the heart upwards, increasing the pressure in the ventricles
. Blood is pushed through the arteries
. The pressure of the blood against the AV valves closes them, preventing back flow
What is responsible for the heart sounds heard with a stethoscope?
The opening and closing of the AV and SL valves
What brings about the sequence of events that occurs during each heartbeat?
The activities of sino-atrial node (SAN)/ pacemaker and the conducting system of the heart
Where is the SAN/pacemaker located?
In the wall of the right atrium
What sets the rate at which the cardiac muscle contracts?
The auto-rhythmic cells of the SAN/pacemaker
What is the first step of the cardiac conducting system?
. The timing of the cardiac muscle cell contraction is controlled by the impulses from the SAN spreading through the muscle cells in the all of the two atria causing them to contract simultaneously (atrial systole)
What is the second step of the cardiac conducting system?
. The impulses are then picked up by the atrio-ventricular node (AVN) which is loated in the centre of the heart
What is the third step of the cardiac conducting system?
. The 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 ensures that ventricle systole occurs slightly later than atrial systole, which allows for the ventricles to fill completely before they contract
What is the fourth step of the cardiac conducting system?
. The timing of cardiac cells contracting is controlled by the impulse from the SAN/pacemaker spreading through the ventricles.
Where is the heartbeat originated and what is it regulated by?
It originates in the heart but is regulated by both nervous and hormonal control
What can these impulses in the heart generate?
They generate currents that can be detected by an electrocardiogram (ECG)
What can the electrical activity of the heart generate?
Tiny currents that can be picked up by electrodes placed on the skin surface. This is shown in an ECG
What is the P wave in an ECG?
The electrical activity during atrial systole, the electrical impulses spreading over the atria from the SAN
What is the QRS wave in an ECG?
The electrical activity during ventricular systole, the electrical impulses passing through the ventricles
What is the T wave in an ECG?
The ventricular repolarisation; end of systole. The electrical recovery of the ventricular walls.
What is the Q-T interval in an ECG?
The contraction time of the ventricles contracting
What is the T-P interval in an ECG?
The filling time for the ventricles to relax and fill with blood, diastole.
What regulates the rate of the SAN and how?
The medulla of the brain and it regulates it through the antagonistic (working oppositely) action of the autonomic nervous system (ANS)
How does the cardio-accelerator centre send its nerve impulses?
Via sympathetic nerves to the heart
How does the cardio-inhibitor centre send its nerve impulses?
Via parasympathetic nerves
What do sympathetic nerves release?
Noradrenaline which increases heart rate
What do parasympathetic nerves release?
Acetylcholine which decreases heart rate
What is blood pressure?
The force that is exerted by blood against the walls of the blood vessels
What is blood pressure measured using?
A sphygomomanometer, in units of millimetres of mercury (mmHg)
What happens to blood pressure during ventricular systole?
It increases. The pressure of blood in the aorta rises to a maximum (120mmHg)
What happens to blood pressure during ventricular diastole?
It decreases. The pressure of blood in the aorta drops to a minimum (80mmHg)
What is the normal blood pressure?
120/80mmHg
What is the first step in measuring blood pressure (using a sphygmomanometer)?
The cuff is inflated until it stops blood flow in the artery
What is the second step in measuring blood pressure?
The cuff is allowed to deflate gradually. The blood starts to flow (detected by a pulse) at systolic pressure
What is the third step in measuring blood pressure?
More air is released from the cuff. The blood flows freely through the artery (and a pulse is not detected) at diastolic pressure.
What is hypertension?
The prolonged elevation of blood pressure when at rest, such as above 140/90mmHg
What is hypertension a major risk of?
Coronary heart disease, strokes etc. These have a relatively high incidence later in life.
Hypertension is commonly found in people that are?
Overweight, not taking enough exercise, eating a diet high in saturated fat or total fat, eating too much salt and under continuous stress.
