The Heart as a Pump Flashcards
Why does the heart have a double pump
2 ventricles which each supply different circulations
What is the systemic circuit
The blood vessels that transport blood to and from all the body tissues
What is the pulmonary circuit
Blood vessels that carry blood to and from the lungs
What does the right hand side of the heart do
Receives oxygen-poor blood from the body and pumps it to the lungs
What does the left hand side of the heart do
Receives oxygen-rich blood from the lungs and pumps it to the body’s tissues
Where is the heart located
In the mediastinum behind the sternum between the 2nd and 6th ribs and T5-T8
Where is the apex of the heart loacted
At the 5th intercostal space in the left mid-clavicular line
What is the heart surrounded by
A pericardium
What are the chambers of the heart
Right atrium -> right ventricle -> left atrium -> left ventricle
Describe the atria and their functions
Superior “receiving chambers”, blood from the veins enters the atria
What divides the two atria
The interatrial septum
Describe the ventricles and their functions
Inferior “pumping chambers”, thick muscular walls to increase the force of the pumping action
What divides the two ventricles
Interventricular septum
Why is the LV thicker than the RV
Because it forces blodo out against more resistance as the systemic circulation is much longer than the pulmonary circulatrion
Why are the atria thin
Because ventricular filling is done by gravity, requiring little atrial effort
What are the 3 tricsupid valves
Triscupid, pulmonary, aortic
What is the bicuspid valve
Mitral valve
What valve is between the RA -> RV
Tricuspid valve
What valve is between the LA -> LV
Mitral valve
What valve is between the RV-> pulmonary artery
Pulmonary valve
What valve is between LV -> aorta
Aortic valve
What are the atria -> ventricles valves called
Atrioventricular valves
What are the ventricles -> arteries valves called
Semilunar valves
Describe chordae tendineae in relation to their function
Have low tension when valves are open but high tension when valves are shut in order to ensure valves remain closed
Define heart beat
A single sequence of atrial contraction followed by ventricular contraction
What is normal heart rate
60-100 bpm
What is bradycardia
Slow heartbeat
What is tachycardia
Fast heartbeat
What are the two periods that make up the cardiac cycle
Diastole and systole
What is diastole
A period of relaxation where the heart fills with blood
What is systole
A period of contraction
What sounds does that heart make
Lub Dub
What is S1
“Lub”- closing of the atrioventricular valves at the start of ventricular systole
What is S2
“Dub”- closing of the semilunar valves at the end of ventricular systole
What is the resting HR of athletes
40-60 bmp
What is the sinoatrial node
The heart’s pacemaker
Describe the stages involved in a heartbeat
- From SA node excitation is spread across both atria via connective tissue
- Passes to atrioventricular node
- Conduction to AV node is slow and excitation to ventricles is delayed (0.1s), ensures filling of ventricles with blood
- Conduction through rest of heart is rapid- via bundle of His (atrioventricular bundle)
- Divides to supply LV RV via purkinjie fibres Purkinjie fibres spread excitation to ventricular myocytes (fast)
- Ventricles excite at the same time
What does an EGC do
Records the heart;s electrical activity. Excitation thorugh the heart is generated by small electrical currents in the ECF which is detected by electrodes on teh surface of the body which record small voltage changes
Describe an ECG
P wave- depolarisation of the atria (prior to contraction) triggers atria to contract.
QRS complex- ventricular depolarisation, triggers ventricles to contract (includes atrial repolarisation).
T wave- repolarisation of the ventricles
What factors affect the heart rate/ rhythm
Autonomic nervous system, Hormones, Activity, Pathology,
Which hormones affect heart rate/ rhythm
Adrenaline, noradrenaline, thyroid hormones
How does activity affect heart rate/ rhythm
Rest, exercise, stress etc.
How does coronary heart disease occur
In the coronary arteries. Atherosclerosis due to cholesterol and WBC’s result in coronary vessels becoming heard and stiff
What is angina
A result of 75% occlusion of at least one coronary artery, so lack of oxygen to the heart (hypoxic) when the heart needs to work harder during exercise. Can be stable/ unstable
How does a heart attack occur
Clotting factors and plaque result in a thrombus/ blood clot. The clot gets so big it blocks off the blood vessel or breaks off (embolisation). If embolisation occurs the clot floats downstream and blocks off a smaller vessel resulting in a heart attack.
What is requires within 20 minutes after a heart attack
Medication or intervention otherwise the heart muscle will die without oxygen
What is stroke volume
The amount of blood pumped by the LV of the heart in one contraction
What is cardiac output
It is a measure of the amount of blood pumped out of the heart in one minute
What does cardiac output equal?
CO= SV x HR cardiac output = stroke volume x heart rate
