circulatory system

Question 1

what does a closed double circulatory system mean

Answer 1

blood is contained within blood vessels and passes through the heart twice

Question 2

what is the journey of blood through the heart

Answer 2

vena cava
right atrium
right ventricle
pulmonary artery
pulmonary vein
left atrium
left ventricle
aorta

Question 3

describe the atria

Answer 3

thin walled, elastic chambers → receive blood from the veins

Question 4

describe the ventricles

Answer 4

thick walled muscular chambers → pump blood through arteries

Question 5

describe the valves in the heart

Answer 5

AV valve → separate atria and ventricles to prevent back flow
semi-lunar valve → separate ventricles and arteries

Question 6

describe the tendinous chords

Answer 6

inelastic connectivity tissue → prevents inversion of AV valves

Question 7

describe the septum

Answer 7

wall of tissue separating separate sides of heart

Question 8

describe the coronary arteries

Answer 8

provide heart with its own blood supply

Question 9

why is the left side of the heart thicker than the right

Answer 9

greater force → pumps blood further

Question 10

what is the cardiac cycle

Answer 10

the series of events that happens in one heart beat

Question 11

what happens in diastole

Answer 11

muscles relax
pressure in ventricles lower than arteries
SL close
atria fill, pressure increases, AV valves open
blood flows passively into ventricles

Question 12

what happens in atrial systole

Answer 12

atrial muscle contract
increasing pressure above ventricles
AV valves forced open
blood flows into ventricles

Question 13

what happens in ventricular systole

Answer 13

ventricles contract
increasing pressure
AV valves close, SL valves open
blood flows into arteries

Question 14

what is the formula for cardiac output

Answer 14

stroke volume x heart rate

Question 15

how is the heartbeat initiated and coordinated

Answer 15

1. initial electric stimulation originates in the SAN in right atrial wall → both atria contract
2. non conducting tissue between atria and ventricles directs impulse to AV node, delaying impulse until atria empties
3. excitation passes through bundle of His, down purkyne fibres, along the bottom of the heart
4. ventricles contract from the bottom up

Question 16

describe and explain the structure and function of arteries

Answer 16

carry blood away from heart to organs

thick muscular walls / narrow lumen → withstand high pressure

thick elastic tissue → stretch and recoil

Question 17

describe and explain the structure and function of veins

Answer 17

carry blood from organs to heart

large lumen / thin walls → low pressure

valves → prevent back flow

muscles sporadically contract → temporarily increase pressure

Question 18

describe and explain the structure and function of arterioles

Answer 18

carry blood from arteries to capillaries

relatively thicker muscle layer and thinner elastic layer → regulate blood flow to organs by vasoconstriction (narrowing lumen) or vasodilation

Question 19

describe and explain the structure and function of capillaries

Answer 19

connect arteries and veins / exchange substances

small diameter → low pressure slows down flow

numerous / branched → large SA

one cell thick → short diffusion pathway

pores → permeable → enable exchange of substances

Question 20

how is tissue fluid formed

Answer 20

at arteriole end of the capillary:

• high hydrostatic pressure forces water and dissolved substances out of blood, into cells, down a pressure gradient, into spaces between cells → tissue fluid
• proteins remain in blood, creating water potential between capillary and tissue fluid

at venule end of the capillary:

• loss of fluid leads to fall in hydrostatic pressure → water moves by osmosis into capillary down a water potential gradient

excess tissue fluid is drained away by lymphatic system → fluid returned to bloodstream

Question 21

describe and explain the structure and function of red blood cells

Answer 21

transport oxygen via haemoglobin around the body

bioconcave discs → increases SA:V ratio
no organelles → carry more haemoglobin
very small → short diffusion pathway

Question 22

describe and explain the structure and function of haemoglobin

Answer 22

binds to and transports oxygen around blood

a large, globular protein with a quaternary structure, made of 4 polypeptide chains

each subunit contains a haem group containing an iron ion

Question 23

what is cooperative binding

Answer 23

1. the binding of the first haem group with a molecule of oxygen changed the tertiary structure / 3D shape
2. uncovers a second haem group, making it more accessible to oxygen, increasing affinity
3. this increases affinity for subsequent molecules

this explores the sigmoidal shape of the oxygen dissociation curve

Question 24

what is bohr shift

Answer 24

higher partial pressure of CO2 = decrease in pH and tertiary structure = lower affinity for oxygen so unloads

ie respiring tissues during exercise

Question 25

compare high and low affinity haemoglobin

Answer 25

low pO2 environment → oxygen loads more readily in lungs → curve shifted left → haemoglobin more saturated at given pO2 high metabolic rate → haemoglobin unloads readily for respiration → curve shifted right → haemoglobin less saturated at given pO2

Question 26

what is atherosclerosis

Answer 26

build up of atheroma narrowing the lumen

Question 27

what are atheromas and how are they formed

Answer 27

fatty plaques 1. artery lining damaged by high blood pressure 2. inflammatory response triggers accumulation of white blood cells and lipids 3. build up forms atheroma → lumen narrows, blood flow restricted, pressure increases

Question 28

what happens if an atheroma ruptures

Answer 28

thrombosis / blood clot prevents blood flpw

Question 29

how do lack of exercise and high blood pressure increase the risk of heart disease

Answer 29

lack of exercise - sedentary lifestyle increases blood pressure high blood pressure - strain on arteries causing atherosclerosis

Question 30

what is oxyhaemoglobin

Answer 30

formed by the 4 molecules of oxygen that bind to the 4 haem groups

Question 31

what does a high affinity to oxygen mean

Answer 31

high affinity for oxygen, readily loading oxygen where concentration are high and dissociating where low

Question 32

what are the consequences to tissues and cells if a thrombosis forms

Answer 32

oxygen can’t be delivered to tissues and cells can’t undergo aerobic respiration

Question 33

what happens if the atheroma is in the coronary arteries

Answer 33

blockage means heart can’t get oxygen supply → myocardial infarction (heart attack)

Question 34

how is smoking a risk factor for heart disease

Answer 34

nicotine increases chance of blood clots → heart pumps faster increasing blood pressure carbon monoxide binds to haemoglobin reducing oxygen transport in blood

Question 35

how does diet increase the risk of heart disease

Answer 35

high saturated fats low unsaturated fats increase risk → increases blood cholesterol levels → atheroma / high salt increase risk by increasing blood pressure

Question 36

how do genetics and gender increase the risk of heart disease

Answer 36

genetics - alleles that increase cholesterol gender - low oestrogen levels in men → decreases HDL cholesterol