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Biology IB HL - D4 The Heart Part 2
This deck covers key concepts related to the heart's function, including the cardiac cycle, heart sounds, and cardiac output. It is designed to help students understand the physiological processes and structures involved in heart function.
What is the role of the bundle of His?
The Bundle of His innervates Purkinje fibres in the ventricular wall, which causes the cardiac muscle to contract
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Key Terms
Term
Definition
What is the role of the bundle of His?
The Bundle of His innervates Purkinje fibres in the ventricular wall, which causes the cardiac muscle to contract
Why does the signal travel down the heart?
This sequence of events ensures contractions begin at the apex (bottom), forcing blood up towards the arteries
What happens after each contraction of the heart?
Heart Relaxation / Diastole
After every contraction of the heart, there is a period of insensitivity to stimulation (i.e. a refractory period)
What is the role of diastole? 2
This recovery period (diastole) is relatively long, and allows the heart to passively refill with blood between beats; This long recovery period also ...
What ensures one-way circulation of blood around the body?
The heart contains a number of heart valves which prevent the backflow of blood; This ensures the one-way circulation of blood around the body
What are the two sets of valves in the heart and their roles?
There are two sets of valves located within the heart:
Atrioventricular valves (tricuspid and bicuspid) prevent blood in the ventricles from flowing b...
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| Term | Definition |
|---|---|
What is the role of the bundle of His? | The Bundle of His innervates Purkinje fibres in the ventricular wall, which causes the cardiac muscle to contract |
Why does the signal travel down the heart? | This sequence of events ensures contractions begin at the apex (bottom), forcing blood up towards the arteries |
What happens after each contraction of the heart? | Heart Relaxation / Diastole
After every contraction of the heart, there is a period of insensitivity to stimulation (i.e. a refractory period) |
What is the role of diastole? 2 | This recovery period (diastole) is relatively long, and allows the heart to passively refill with blood between beats; This long recovery period also helps prevent heart tissue becoming fatigued, allowing contractions to continue for life |
What ensures one-way circulation of blood around the body? | The heart contains a number of heart valves which prevent the backflow of blood; This ensures the one-way circulation of blood around the body |
What are the two sets of valves in the heart and their roles? | There are two sets of valves located within the heart:
Atrioventricular valves (tricuspid and bicuspid) prevent blood in the ventricles from flowing back into the atria
Semilunar valves (pulmonary and aortic) prevent blood in the arteries from flowing back into the ventricles |
How are heart sounds made? | Heart sounds are made when these two sets of valves close in response to pressure changes within the heart |
What causes the first heart sound? (lubb) | The first heart sound is caused by the closure of the atrioventricular valves at the start of ventricular systole |
What causes the second heart sound? (dubb) | The second heart sound is caused by the closure of the semilunar valves at the start of ventricular diastole |
What is the cardiac cycle? | The cardiac cycle describes the series of events that take place in the heart over the duration of a single heart beat |
What is the cardiac cycle comprised of? | It is comprised of a period of contraction (systole) and relaxation (diastole) |
How can the cardiac cycle be mapped? | The cardiac cycle can be mapped by recording the electrical activity of the heart with each contraction |
What machine is used to map the cardiac cycle? | Activity is measured using a machine called an electrocardiograph to generate data called an electrocardiogram |
What are the 5 stages of an ECG? | P wave; PR interval; QRS complex; ST segment; T wave |
What is the P wave? | The P wave represents depolarisation of the atria in response to signalling from the sinoatrial node (i.e. atrial contraction) |
What is the QRS complex? | The QRS complex represents depolarisation of the ventricles (i.e. ventricular contraction), triggered by signals from the AV node |
What is the T wave? | The T wave represents repolarisation of the ventricles (i.e. ventricular relaxation) and the completion of a standard heart beat |
What is the role of the PR interval and ST segment? | Between these periods of electrical activity are intervals allowing for blood flow (PR interval and ST segment) |
What can be done with ECG's? | Data generated via electrocardiography can be used to identify a variety of heart conditions, including: |
What is Tachycardia and bradycardia? | Tachycardia (elevated resting heart rate = >120 bpm) and bradycardia (depressed resting heart rate = < 40 bpm) |
What are arrhythmias? | Arrhythmias (irregular heart beats that are so common in young people that it is not technically considered a disease) |
What are fibrillations? | Fibrillations (unsynchronised contractions of either atria or ventricles leading to dangerously spasmodic heart activity) |
What is cardiac output? | Cardiac output describes the amount of blood the heart pumps through the circulatory system in one minute |
What is the use of the cardiac output value? | It is an important medical indicator of how efficiently the heart can meet the demands of the body |
What is the equation for cardiac output? | There are two key factors which contribute to cardiac output – heart rate and stroke volume
Equation: Cardiac Output (CO) = Heart Rate (HR) × Stroke Volume (SV) |