KA6 - The Structure And Function Of The Heart Flashcards
What type of blood does the left side of the heart pump and where does it pump it to?
The left side of the heart pumps oxygenated blood to the body cells
What type of blood does the right side pump and where does it pump it to?
The right side of the heart pumps deoxygenated blood to the lungs
Name the 8 chambers of the heart
Right ventricle Right atrium Vena cava Pulmonary artery Aorta Pulmonary vein Left atrium Left ventricle
State the names of the 2 valves and where they are found in the heart
AV valves are found between the atria and ventricles.
Semi lunar valves are found at the exit to the aorta and pulmonary artery.
Why is the human circulatory system referred to as a double system?
Because it has the pulmonary circuit and the systemic circuit
What is the pulmonary circuit?
The pulmonary circuit carries deoxygenated blood from the right ventricle to the lungs and returns oxygenated blood to the heart
What is the systemic circuit?
The systemic circuit carries oxygenated blood from the left ventricle to the aorta to the rest of the body and returns deoxygenated blood to the heart.
What is heart rate?
The number of times a heart beats in one minute measure in beats per minute
What is stroke volume?
The volume of blood ejected by each ventricle during contraction measured in millilitres
What is cardiac output?
The volume of blood pumped by each ventricle per minute
How is cardiac output calculated?
CO = HR XSV
What are the 3 stages in the cardiac cycle?
- Aerial and ventricular diastole
- Atrial systole
- Ventricular systole
What is meant by systole ?
Contraction of the heart
What is meant by diastole?
Relaxation of the heart
Explain atrial and ventricular diastole
During this stage all chambers of the heart are relaxed and filling with blood.
The AV valves are open and the semi lunar valves are closed.
Blood returning to the atria flows into the ventricles.
Explain atrial systole
During this stage, both atria contract.
The remaining blood in the atria is forced into relaxed ventricles through the open AV valve.
Explain ventricular systole
AV valves close preventing back flow of blood into atria.
Ventricles contract.
Blood pumped out of the heart, through semi lunar valves into the aorta and pulmonary artery.
Semi lunar valves close when pressure in arteries exceeds pressure in ventricles. This prevents the back flow of blood into the ventricles.
Cardiac cycle begins again.
Describe pressure changes during the cardiac cycle
Pressure is highest during ventricular systole
Explain the sound of a heartbeat
The opening and closing of the AV and semi lunar valves creates the sound of the heart which are heard with a stethoscope
What does the conducting system of the heart ensure?
That the heart contracts in a coordinated manner
What 2 nodes are involved in the conducting system of the heart?
Sino atrial node(SAN)
Atrio ventricular node(AVN)
Where is the SAN located?
The top wall of the right atrium
Where is the AVN located?
The centre of the heart
Explain the sino atrial node
The SAN sends out electrical impulses which are carried through the muscular walls of both atria. These impulses cause atrial systole.
Explain the atrio ventricular node
The impulses from SAN travel to and are passed on to another node within the heart, the AVN.
Impulses from the AVN then travel down fibres in the central wall of the heart. The impulse then splits and travels up the left and right ventricles causing them to contract simultaneously, ventricular systole.
What is an electrocardiogram?
Impulses in the heart generate currents that can be detected by an electrocardiogram.
In an electrocardiogram, what is the P wave?
The P wave corresponds to a wave of excitation spreading over the atrial walls causing atrial systole.
In an electrocardiogram, what is the QRS wave?
The QRS wave corresponds to a wave of excitation spreading over the ventricle walls causing ventricular systole
In an electrocardiogram, what is the T wave?
The T wave corresponds to electrical recovery of the ventricles
What is the function of the medulla in the conducting system?
The medulla regulates the rate of SAN through antagonistic action of the autonomic nervous system
What is the autonomic nervous system?
The autonomic nervous system varies the rate at which the heart contracts.
What are the 2 antagonistic beaches involved in the autonomic nervous system?
Sympathetic pathway
Parasympathetic pathway
What is the sympathetic pathway?
Sympathetic nerves release noradrenaline which increases heart rate
What is the parasympathetic pathway?
Parasympathetic nerves release acetylcholine which decreases heart rate
What is blood pressure?
Blood pressure is the force exerted by blood against walls of blood vessels
What does blood pressure do during the cardiac cycle?
Changes the aorta
What is used to measure blood pressure?
A sphygmomanometer in mmHg
What happens to blood pressure during ventricular systole and diastole?
Blood pressure increases during ventricular systole and decreases during diastole
What is a typical blood pressure reading for a hound adult?
120/80mmHg
What are the two values used to measure blood pressure?
Systolic BP
Diastolic BP
Explain how a sphygmomanometer is used
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 a pulse is not detected) at diastolic pressure.
What can hypertension cause?
Hypertension is a major risk factor for many diseases including coronary heart disease.
