Cardiovascular System (heart)

Question 1

Main components?

Answer 1

Heart (the pump)
High pressure distribution circuit (arteries)
Exchange vessels (capillaries)
Low pressure collection and return circuit (veins)

Question 2

Functions?

Answer 2

1. Circulate CO2 and O2
2. Providing cells with nutrients
3. removing waste products
4. stops bleeding after injury
5. helps regulate body temperature
6. transporting hormones
7. protecting body against disease

Question 3

What does the right heart do (simply)?

Answer 3

Receives deoxygenated blood returning from throughout the body, pumps the deoxygenated blood to the lungs to receive oxygen.
The right atrium receives the blood from the super and inferior vena cava, it goes through the tricuspid valve into the right ventricle which pumps the deoxygenated blood to the lungs via the pulmanory artery, passing through the pulmonic valve.

Question 4

What does the left heart do (simply)?

Answer 4

Receives oxygenated blood from the lung and pumps it back through the body. The left atrium receives blood from the lungs, it goes through the bicuspid/mitral valve into the left ventricle and pumps the oxygenated blood to the rest of the body via the aorta, through the aortic valve.

Question 5

What is systole and diastole?

Answer 5

Systole - contraction to pump out the blood.
Diastole - relaxation allowing it to be filled with blood.

Question 6

How is blood supplied to the left atrium?

Answer 6

Receives oxygen at the lungs, and travels to the left atrium via pulmonary veins.

Question 7

How is blood supplied to the right atrium?

Answer 7

Superior vena cava (upper body) and inferior vena cava (below the heart) into the right atrium - they’re pulmanory valves.

Question 8

How is blood taken from the right ventricle?

Answer 8

Leaves the right ventricle to the lungs via the pulmanory artery.

Question 9

How is blood taken from the left ventricle?

Answer 9

Oxygenated blood leaves the left ventricle via the aorta.

Question 10

What is the arterial system?

Answer 10

This is the high pressure tube system that propels oxygen rich blood to tissues. The aorta is the beginning. It leads to arteries which have a large lumen to handle the high blood pressure, so large volumes of blood can move through at once. They have a layer of smooth muscle allowing them to constrict and relax to regulate blood flow. Arteries branch to arterioles, then capillaries, then veins.
When the heart is systole, the pressure exerted on artery walls is increased.

Question 11

How is blood pressure calculated?

Answer 11

Cardiac output x total peripheral resistance (TPR)

Question 12

What are normal blood pressures that cause blood to be pumped from the heart?

Answer 12

systolic bp is usually 120mmHg. for blood to leave the ventricles, pressure within the LV have to exceed the pressure in the aorta. normal diastolic pressure is 80mmHg.

Question 13

How is mean arterial pressure calculated (MAP)?

Answer 13

1/3 systole + 2/3 diastole

Question 14

What is the structure and function of capillaries?

Answer 14

They are around 7-10 micrometres. They are one cell thick to allow for easy diffusion. In skeletal muscle, they are 2000-3000 per square millimetre in density. They have pre-capillary sphincters that regulate blood flow for metabolic requirements - the sphincters sit at the capillary origin. Their large surface area and low velocity blood flowing through makes it very efficient for diffusion.

Question 15

What is the structure and function of veins?

Answer 15

Deoxygenated blood travels through the veins after oxygen extraction at the capillaries. Blood flow velocity increases due to the larger lumen allowing more blood to flow through. veins contain valves to prevent black flow, the valves close due to muscle contraction.

Question 16

How is the heart muscle composed?

Answer 16

Cardiomyocytes make up the heart wall and divide the chambers. They are rod like cardiac muscle cells that contain proteins which generate force following excitation. Myocytes are connected via intercalated disks, it is important when a nerve signal activates the cardiomyocytes as it means it can spread to other cardiomyocytes so they can activate simultaneously.

Question 17

What is polarisation of the heart?

Answer 17

The interior of a cell is more negative than the exterior due to differenced in ion concentrations, this means cells are polarised. Contraction occurs due to depolarisation. Depolarisation is when positive ions flood into the negatively charges interior of the cell and cause it to be ‘less polarised’. The reason the positive ions flood into the cell is due to an active potential (electrical impulse) which will travel along the surface of the cardiomyocyte (sarcolemma) and alter its permeability - allowing NA+ and Ca++ to enter the cell. The cells resting internal is -90mV, when depolarisation occurs it reaches +10mV.

Question 18

How are actin and myosin causing the heart to beat?

Answer 18

Myosin heads interact with actin and pull it to the middle of the sarcomere, shortening the sarcomere and generating force, causing a contraction. This occurs due to a nerve signal activating a cardiomyocyte.

Question 19

What nodes are involved in initiating an action potential for contraction?

Answer 19

Sinoatrial node (SA) - specialised muscle tissue located in the top right of the right atrium, spontaneously depolarising and repolarising, spreading throughout the right atrium to the atrioventricular node.
Atrioventricular node (AV) - specialised muscle tissue located near the interatrial septum, receiving signals from the SA node, and following a delay, transmits AP to the ventricles.

Question 20

What is electromyography?

Answer 20

ECG - reading of the electrical activity from the heart, specifically the myocardium (heart muscle cells) which creates an electrical field throughout the body. Electrodes are places on the skin and detect the voltage change from the sequence of electrical events through the cardiac cycle.

Question 21

In an ECG, what does the P wave indicate?

Answer 21

Initiation of depolarisation of the atria when the SA node transmits a wave of depolarisation that spreads across the right and left atria.

Question 22

In an ECG, what does the PR segment indicate?

Answer 22

Completed depolarisation and thus contraction. Blood is pumped to the ventricles and the mitral valves close. The depolarisation reached the AV node and is delayed.

Question 23

In an ECG, what does the QRS complex indicate?

Answer 23

Initiation of depolarisation of the ventricles. Depolarisation travels through the bundle of his onto the right and left ventricles, causing ventricular systole. Simultaneously there is repolarisation of the atria.

Question 24

In an ECG, what does the ST segment indicate?

Answer 24

Completion of depolarisation of the ventricles, they contract.

Question 25

In an ECG, what does the T wave indicate?

Answer 25

Ventricular repolarisation begins. When it is complete and the ventricles are relaxed, this is the line on the bassline after T and before P.

Question 26

What is the equation for stroke volume?

Answer 26

This is blood ejected from the heart when it beats. It is the end diastolic volume - end systolic volume.

Question 27

What is the equation for ejection fraction?

Answer 27

this is the fraction of blood from the left ventricle that is ejected during systole. it is the stroke volume - end diastolic volume.

Question 28

What is the equation for Cardiac output L/min?

Answer 28

This is heart rate (bpm) x stroke volume (ml/beat)

Question 29

How does the autonomic nervous system regulate heart rate?

Answer 29

It acts unconsciously to regulate body functions. it is composed of two branches, sympathetic nervous system which implicates the ‘fight or flight response’; and the parasympathetic nervous system, implicating the ‘rest and digest response’.
they both elicit their responses via neurohormones.

Question 30

How does the sympathetic nervous system regulate heart rate?

Answer 30

When their neurohormones bind to the receptors on the target organ/ tissue, they INCREASE an activity. The neurohormone secreted from the sympathetic nervous system is norepinephrine, collectively known as catecholamines. These nerves innervate the SA and AV nodes to release norepinephrine - accelerating SA node depolarisation and making the heart beat faster.

Question 31

How does the parasympathetic nervous system regulate heart rate?

Answer 31

The primary neurohormone of the parasympathetic nervous system is acetylcholine. cardioinhibitory nerves innervate the SA and AV nodes to release acetylcholine and reduces SA depolarisation to slow the heart rate.

Question 32

What are the preload and afterload effects?

Answer 32

Preload - filling pressure in the ventricles is increased during diastole, this greater tension causes an increase in stroke volume. It is determined by the Frank Sterling Mechanism.
Afterload - during ventricular systole, the pressure of the ventricles must exceed the aortic pressure for ejection to occur. The resistance the ventricle must overcome to circulate the blood through the aorta is the afterload.

Question 33

What is the vascular network?

Answer 33

This is the range of vessels that blood travels through to get around the body. There are distribution and resistance vessels (aorta, large and small arteries), exchange vessels (capillaries and small venules), capacitance vessels (large venules, veins, vena cava).

Question 34

What is poiseuille’s law?

Answer 34

Blood flow = pressure gradient/ resistence

Question 35

How is the vascular system regulated (sympathetic)?

Answer 35

Sympathetic input into the arteries and arterioles causes vasoconstriction - decreasing the radius therefore increasing the resistance.

Question 36

How to baroreceptors regulate the vascular system?

Answer 36

They detect the amount of pressure in the arteries. They send signals to the medulla in the control centre. When a decrease in mean arterial pressure occurs, the baroreceptors detect this and send signals to the effectors to vasoconstrict and increase cardiac output.

Question 37

How does nitric oxide regulate vascular system?

Answer 37

In response to an increase arterial stress due to increased blood flow through the arteries and arterioles, NO is synthesised and released by the endothelial cells, reducing vasoconstriction and increasing vasodilation, therefore increasing blood flow.