4.4 Circulation

Question 1

give 4 features of mass transport systems

Answer 1

• system of vessels that carry substances
• making sure substances move in the right direction
• moving materials fast to supply the needs of the organism
• suitable transport medium

Question 2

describe a single circulatory system

Answer 2

heart pumps deoxygenated blood to the organs of gas exchange, where blood takes in oxygen and gives up carbon dioxide at the same time
blood then travels to the rest of the body, giving up oxygen to cells before returning to the heart

Question 3

describe a double circulatory system

Answer 3

circulation that involves 2 systems; pulmonary and sytemic circulation

pulmonary circulation - deoxygenated blood travels from the heart to lungs and returns to heart as deoxygenated blood

systemic circulation - oxygenated blood leaves heart and flows around body, returning deoxygenated blood back to the heart

Question 4

give functions of the cardiovascular system

Answer 4

delivers materials needed by body cells
carries away waste products
carries hormones
forms part of the defense system
distributes heat

Question 5

describe function of plasma

Answer 5

transports food products, nutrients, hormones etc
maintains body temperature
acts as a buffer to pH changes
contains platelets

Question 6

describe what erythrocytes are

Answer 6

red blood cells
contain haemoglobin which binds to oxygen
no nucleus and biconcave shape gives a large sa:v ratio to aid oxygen diffusion and able to pack in more haemoglobin

Question 7

describe what leucocytes are

Answer 7

white blood cells
defend body against infection
several types: neutrophils, monocytes, eosinophils and lymphocytes

Question 8

give function of neutrophils and monocytes

Answer 8

engulf and digest pathogens by phagocytosis

Question 9

give function of eosinophils

Answer 9

involved in allergic reaction responses + protection against viruses and parasites

Question 10

give function of lymphocytes

Answer 10

natural killer cells
vital to immune system
formation of antibodies

Question 11

describe function of arteries and how it is adapted for the function

Answer 11

carries blood away from heart towards body cells.
has external layer of tough tissue
artery wall has elastic fibres and smooth muscle
smooth lining = easy blood flow
lumen is small = carries high pressure blood
lots of elastic fibres = stretches to accomodate high volumes of blood

Question 12

describe function of capillaries and how it is adapted for the function

Answer 12

branch between cells
small vessels
blood travels slow - more diffusion
blood is oxygenated
thin walls allow rapid diffusion (epithelial cells)

Question 13

describe function of veins and how it is adapted for the fucntion

Answer 13

carries blood back to the heart
carries low pressure blood
has a large lumen

Question 14

describe the events in the cardiac cycle

Answer 14

1. vena cava transports deoxygenated blood from the body to right atrum

2. right atrium fills with blood
tricuspid valves open
atrium contracts
blood enters right ventricles
semi-lunar valves prevent backflow

3. right ventricles contract
   blood flows into pulmonary artery
   travels to lungs
   tricuspid valves close
4. oxygenated blood enters left side of heart by pulmonary veins
   blood retuns to left atrium
   atrium contracts and blood flows into left ventricle
   bicuspid valves prevent backflow
5. left ventricle pumps blood into aorta
   aorta carried blood to rest of body

Question 15

describe the process of controlling the heart beat

Answer 15

1. heartbeat starts in sinoatrial node
   SAN sends impulses across atria walls causing them to contract
   annulus fibrosus (tissue between atria and ventricles) prevents impulse from spreading to ventricles - causes delay
2. impulses reach atrioventricular node
   impulse passed via Bundle of His to the ventricles
3. bundle of His splits into 2 branches
   impulse carried into Purkyne tissue
   carries impulse down septum + through ventricles
4. impulse causes ventricular contraction from apex upwards, squeezing blood out of the heart.

Question 16

give the equation of carbon dioxide dissolving in blood + reacting with water. name the enzyme controlling this reaction.

Answer 16

O2 (aq) + H2O « H2CO3 « HCO3- + H+

carbonic anhydrase controls the reaction

Question 17

where is most carbon dioxide carried?

Answer 17

• in solution in plasma
• combines with haemoglobin to form carbaminohaemoglobin
• transported in cytoplasm of red blood cells as hydrogencarbonate ions

Question 18

describe what happens in the blood when there is a high concentration of carbon dioxide

Answer 18

at high concentration of CO2, carbonic anhydrase catalyses the formation of carbonic acid

Question 19

describe what happens in the lungs when there is low concentration of carbon dioxide

Answer 19

at low CO2 concentration, carbonic anhydrase catalyses reverse reaction + frees carbon dioxide out of blood and into the lungs

Question 20

what ions are formed when carbonic acid dissociates?

Answer 20

H+ and HCO3- ions

Question 21

in the formation of blood clots, platelets release serotonin + thromboplastin. give the function of both.

Answer 21

serotonin- causes the smooth muscle of blood vessel to contract which cuts off blood flow to damaged area
thromboplastin - enzyme that leads to the formation of clots

Question 22

describe the blood clotting cascade

Answer 22

1. thrombocytes (platelets) stick to exposed collagen fibres, forming a plug.
   thrombocytes become activated + releasing clotting factors through thromboplastins
2. thromboplastins convert prothrombin (inactive plasma protein0 into thrombin (active plasma protein)
   requires Ca2+ and vitamin K
   catalysed by thrombokinase
3. thrombin catalyses the conversion of soluble fibrinogen into soluble fibrin
   fibrin forms a mesh that traps red blood cells and strengthens platelet plug, forming a clot
4. blood clot is eventually reabsorbed by fibrinolysis
   controlled by enzyme plasmin

Question 23

define atherosclerosis

Answer 23

condition in which yellow fatty deposits build up on arttey linings, causing them to narrow

Question 24

describe how an atheroma is formed

Answer 24

1. slight damage to endothelial cells lining the artery can lead to a build-up of lipids
2. blood platelets form a cap over the fatty plaque which narrows the artery
3. any further damages causes clot formation which can block the whole artery and have fatal consequences

Question 25

why does atherosclerosis usually occur in arteries?

Answer 25

blood in arteries flows fast under high pressure = more strain on endothelium lining in veins, pressure is low so damage is less likely

Question 26

describe the stages of atherosclerosis

Answer 26

1. body's inflammatory system begins + white blood cells arrive at site of damage cells accumulate chemicals from blood e.g cholesterol 2. this leads to an atheroma forming on endothelial lining 3. fibrous tissue + calcium salts build up around atheroma, forming a hardened plaque 4. hardened area means part of the artery wall hardens so it is less elastic than it should be

Question 27

what are the effects of atherosclerosis?

Answer 27

lumen of artery becomes smaller this increases blood pressure so it is harder to pump blood raised blood pressure = more endothelial damage = more plaques =increased blood pressure

Question 28

consequences of atherosclerosis

Answer 28

``` aneurysms raised blood pressure stroke angina myocardial infarction ```

Question 29

identify the non-modifiable risks of atherosclerosis

Answer 29

genes age gender

Question 30

identify the modifiable risk factors of atherosclerosis

Answer 30

``` smoking exercise weight stress diet ```