D.4 Flashcards
What is a cardiac cycle?
A cardiac cycle is a series of events. From the beginning of one heartbeat to the beginning of the next. This is commonly referred to as one heartbeat.
On average, how many cardiac cycles are there per minute?
72
What is diastole?
When a chamber is relaxed, causing a decrease in pressure and allowing blood to fill the chamber
What is systole?
When a chamber contracts causing an increase in pressure and forcing blood out of the chamber through any available opening
What is a myogenic muscle contraction?
A muscle contraction that spontaneously contracts and relaxes without any control by the nervous system
What is the role of sinoatrial node (SA node)
Is a specialised tissue inside the right atrium, the acts as a pacemaker for the heart by sending out a signal that causes both atria to contract
What is the role of the atrioventricular node (AV node)?
It is another group of specialised tissues, located in the right atrium, and its job is to receive a signal from the SA node, and then relay the signal to the ventricles are causing them to contract
What is the consequence of the slight delay between the SA and the AV node?
It takes about .1 second for the AV node to relay the message to the ventricles
How does the brain control the heartbeat?
- Carbon dioxide accumulates in the blood.
- The medulla oblongata sensors the increased carbon dioxide levels
- the medulla oblongata sends a message through nerves to the SA node to increase the heart rate. Once the CO2 levels return to normal, the medulla oblongata send another message to the SA node to return to a resting heart rate.
What does the AV node send signals to the ventricles through?
Through specialised nerves, called Purkinje fibres, which carry the signal from the Aviino to the ventricle is causing them to contact
What does an ECG measure?
Measures electrical activity from SA node and AV nodes overtime
What does the P-wave in an ECG indicate?
The SA node has fired, causing the atria to contract
What does point Q on an ECG show?
The AV node has fired
What does the QRS complex on an ECG show?
The AV signal reaches the Purkinje fibres and the ventricles contract
What does the T-wave on an ECG show?
The AV node is re-polarising, and getting ready for the next cardiac cycle
What is atherosclerosis?
A buildup of materials or (plaque) in the arteries
What is plaque made up of?
Lipid cholesterol and calcium
What does a buildup of plaque do?
As it builds up in arteries, it causes them to be stiff and causes the lumen to become smaller. In some cases plaque can totally block the artery.
What happens when people have damaged or malfunctioning SA nodes?
An artificial pacemaker can be implanted in the chest to provide an electrical shock to the heart to replace the shop, normally provided by the SA node
How does a defibrillator help when someone is experience a heart attack?
It can shock the heart back into rhythm by resetting the electrical signals come in from the SA node
What is thrombosis?
A condition where a blood clot develops in one of the blood vessels
Why can blood clots be very dangerous?
They can travel to the brain and block a blood vessel (stroke) or to the lungs or to the coronary arteries (heart attack)
What is hypertension?
Higher than normal blood pressure
How does hypertension develop?
Hypertension normally develops of many years and it’s usually due to the narrowing of blood vessels from plaque because the blood volume is the same, but the diameter is smaller therefore the pressure increases
