Circulatory system

Question 1

What is the function of the circulatory system

Answer 1

Works to carry oxygen, nutrients and hormones to cell, whilst removing waste products such as carbon dioxide

Question 2

Does blood flow unidirectionally or bidirectionally

Answer 2

Unidirectionally

Question 3

WHat does it mean by ‘humans have a closed circulatory system’?

Answer 3

Physically separated from the rest of the body

Consists of vessels and pumps (heart acts as a driver of fluid around the body)

Question 4

What do arteries do

Answer 4

Carry blood away from the heart

Question 5

What do veins do

Answer 5

Carry blood towards the heart

Question 6

Whyy does blood flow continuously around the body

Answer 6

Because it needs to transport oxygen and other materials around the body

Question 7

What are the 3 main types of blood vessels

Answer 7

Arteries, veins and capillaries

Question 8

What do capillaries do

Answer 8

Capillaries are tiny blood vessels that transport blood, nutrients and oxygen to cells in your organs and body systems.

Question 9

What are the key differences between the three main types of blood vessels

Question 10

What is blood

Answer 10

Blood is considered a connective tissue made up of cellular elements, suspended in a fluid matrix. It makes up a quarter of ECF (blood and plasma)

It also acts as a buffer between cells and external environment

Question 11

What is the main blood composition

Answer 11

92% water
7% protein
1% dissolved organic molecules such as lipids, glucose

Question 12

What is erythropoiesis

Answer 12

Describes the process of blood formation

It is controlled by the glycoprotein erythropoietin (EPO) + some cytokines (which is largely produced by kidney)

Question 13

What is the trigger for EPO release

Answer 13

Hypoxia (low oxygen levels). If it is like this, it triggers the bone marrow to produce more red blood cells

Question 14

What is blood doping

Answer 14

It is used to improve athletic performance by artificially improving body’s ability to transport O2 to tissues/muscles

Question 15

What are 3 common methods of blood doping

Answer 15

Blood transfusions

Injection of EPO

Injection of synthetic O2 carriers

Question 16

What is the heart

Answer 16

It is the workhorse of the body. It generates a pressure to force blood continuously around the body. Composed predominantly of cardiac muscle

Question 17

Explain the nature of the electrical activity in the heart

Answer 17

The SA node can begin the depolarisation. This means that the right atrium and the left atrium starts to depolarise. this signal then has to travel to the AV node which delays the signal transfer, and ultimately delays the contraction of the ventricles until atrium is free of blood. The charge then carries through the bundles of his which shifts depolarisation to the bottom of the heart. These purkinje fibres then spread the depolarisation back up to the top of the heart and also causes a contraction of the ventricles to shift blood up (with aortic valves closed).

Question 18

Explain the process of the mechanical events of the heart

Answer 18

1) late diastole - both sets of chambers are relaxed and ventricles fill passively

2) Atrial systole - atrial contraction forces a small amount of additional blood into ventricles

3) Isovulmic ventricular contraction - first phase of ventricular contraction pushes AV valves closed but does not create enough pressure to open semilunar valves

4) Ventricular ejection - as ventricular pressure rises and exceeds pressure in arteries, the semilunar valves open and blood is ejected

5) Isovolumic ventricular relaxation - as ventricles relax, pressure in ventricles falls. Blood flows back into cusps of semilunar valves and snaps them closed

The process then repeats itself

Question 19

Explain the process of a red blood cell arriving at the right atrium through the heart

Answer 19

Red blood cells arrive in the right atrium through both the superior and inferior vena cava.

It then travels through the tricuspid valve into the right ventricle where it is then pumped through the semilunar valves to the pulmonary arteries which carry blood away from the heart to the lungs. The blood so far is deoxygenated

The oxygenated blood then returns from the lung through the pulmonary veins into the left atrium, which is then pumped through the bicuspid/mitral valve into the left ventricle. It is then pumped through the aortic semilunar valve towards the aorta which will then deliver oxygen rich blood to the rest of the body

Question 20

What is stroke volume

Answer 20

It is the volume ejected by the heart for each contraction

Question 21

Does our heart contract to maximum force? Why or why not

Answer 21

It rarely contracts to maximum force. At rest, after each beat, blood remains in the heart (around 65mL). This stops ventricular walls rubbing against each other as it can cause damage and also allows us to alter how much blood is ejected in the next heartbeat

Question 22

What is the formula for cardiac output

Answer 22

CO = SV x HR

Question 23

How can HR be altered by autonomic nervous system

Answer 23

By changes to depolarisation of autorhytmic cells

Question 24

What are the different blood vessels that the blood passes through, in decreasing blood pressure order

Answer 24

Aorta (highest pressure)
Arteries
Arterioles
Capillaries
Venules
Veins
Vena Cava (least pressure)

Question 25

What is the nature of blood flow in the body

Answer 25

From areas of high to low blood pressure

Question 26

Is the arterial system under high or low blood pressure

Answer 26

High blood pressure

Question 27

Is the venous system under high or low blood pressure

Answer 27

Low blood pressure

Question 28

What does systole mean

Answer 28

Pressure in arteries when heart has contracted

Question 29

What does diastole mean

Answer 29

Pressure in arteries when heart has fully relaxed

Question 30

What is the blood pressure normally given as?

Answer 30

x/y mmHg

where x is the systolic pressure
y is the diastolic pressure

Question 31

What is postural hypotension

Answer 31

It is when we don’t move our legs, and the blood thus cant return to the heart. This is because standing causes blood to “pool” in our feet.

If not enough blood is returning to the head, we faint to ‘rectify’ the problem

Question 32

What are the 3 main mechanisms of exchange in capillaries

Answer 32

Movement between endothelium (diffusion)

Transcytosis (endocytosis and exocytosis of some vesicles o create temporary channels for liquid to move out)

Bulk flow

Question 33

What is bulk flow

Answer 33

Bulk flow is the movement of a mass of fluid that is due to the presence of a pressure gradient.

Question 34

Why is fluid lost from blood to interstitium when exchange occurs in capillaries

Answer 34

This is mainly due to bulk flow. At the arterial end, there is a higher hydrostatic pressure in the capillary leading to greater fluid loss on that end. Meanwhile, at the venous end, due to a lower hydrostatic pressure and higher osmotic pressure, more fluid is absorbed into the capillary. However, overall, there is more fluid loss in the arterial end than fluid gain in venous end, leading to a net loss of fluid into the blood

Filtration: Dominant at the arterial end due to higher hydrostatic pressure in the capillary.
Reabsorption: Dominant at the venous end due to lower hydrostatic pressure and relatively higher osmotic pressure.

Question 35

What is the function of the lymphatic system in relation to the loss of fluid

Answer 35

Returns excess interstitial fluid and filters it before returning it back into the bloodstream

Question 36

What gives the pulsing sensation when we place our fingers to an artery

Answer 36

When the heart empties and blood is put into arteries, it is like a ‘wave’, causing the arteries to expand, thus pushing the blood further, and causing the pulsing sensation