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A-Level Biology > 3.1.2 > Flashcards

3.1.2 Flashcards

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1
Q

Why are transpirt systems needed?

A

To transport oxygen and nutrients to the sites where they are needed and to remove waste products from the cells

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2
Q

Single celled vs multicellular organisms

A

Single celled - processes like diffuision endocytosis osmosis etc can supply everything cell needs to import/export
However as organism gets bigger the distances between the cells and outside of body increases - diffusion would be too slow to meet the demands of the organism

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3
Q

Why are specialised transpirt systems needed?

A

Metabolic demands of most multicellular animals are high - lots of oxygen and food snd produce a lot of waste
SA:V is very small as organism is big so surface area available to absorb and remove susbstances also becomes relative,y smaller
Molecules like hormones and enzymes may be made in one place and needed in another
Food needs to be transported for use in respiration and cell metabolism
Waste products of metabolism beed to be transported to excretory organs

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4
Q

What are circulatory systems?

A

Specialised systems which carry gases, nutrients and waste products around the body
They have a liquid transport medium - blood
They have vessels that carry the fluid
They have a pumping mechanism to move the fluid

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5
Q

What is a mass transport system?

A

When sushtances are transported in a mass of fluid with a mechanism for moving the fluid around the body - can be either open or closed

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6
Q

What is an open circulatory system?

A

There are very few vessels to contain the transport medium - pumped straight from the heart and floods the organs/body cavity - this is called the haemocoel. In the haemocoel the blood is under low pressure wnd comes into direct contact with tissues where exchange takes place between transport medium and the cells ; returns to heart through an open-ended vessel.
INSECTS

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7
Q

How does the open-ended circulatory system work with insects?

A

Found mainly in invertertebrate animals - in insects gas exchange takes plwcd in tracheal system. Insect blood is called haemolymph which only translirgs food and nitrogenous waste and the cells that fight disease (oxygen and carbon dilxide part of tracheal system). Body cavity is split by a membrane with heart extending along thorax and abdomen - haemolymoh circulates but steep diffusion gradients cannit be maintained for efficient diffusion therefore insects cannot control flow of haemolymph to a particular tissue to meet varied demands

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8
Q

What is a closed ciruclatory system?

A

Blood is enclosed in blood vessels not in direct contact with tissue cells - blood is pumped around under pressure due to the heart and blood returns directly to the heart. Substances leave and enter the blood by diffusion through blood vessels

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9
Q

Vessels in closed circulatory system

A

Amount of blood flowing to a particular tissue can be adjusted by widening/narrowinf blood vessels (muscle tissue/elastin) and most closed systems contain a blood pigment that carries the respiratory gases - they are found in many echinoderms (starfish/sea urchins), mammals (veterbrate griups), cephalopod molluscs (squid and octopods) and earthworms (annelid worms)

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10
Q

Single closed circulatory system

A

Found in fish and annelind worms - blood flows through the heart and is pumped out to travel all around the body before returning to the heart. Blood only travkes once through the heart for each complete circulation of the body

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11
Q

How does blood flow in a single closed circulatory system?

A

Blood passes through 2 sets of capillaries - exchanges oxygen snd carbon dioxide (gills) and then exchanges substances at different organ systems. As a result of passing through these 2 sets of narrow vessels, blood pressure drops slightly thus limits the efficiency of exchange so blood returns to heart quite slowly. Sctivity levels of animals with single closed circulations tend to be relatively low

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12
Q

Why are fish different?

A

They have a relatively efficient single circulatory system meaning they can be very sctive. They have a countercurrent gaseous eschange mechanism in their gills that allows continual diffusion. They do not sctively maintain their own temperature. Their body weight is supported by the water. This greatly reduces the metabolic demand of their bodies and combined with efficient gas eschange surface - fish can be very sctive with a single closed circulatory system

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13
Q

Structure of fish circulatory system

A 
1 atrium
1 ventricle
Capillaries in gills
Capillaries in rest of the body
Repeat
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14
Q

When are double circulatory system needed?

A

When birds and mammals are very actuve and mainatin their own body temperature - most efficient system for transporting susbstances around the body

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15
Q

How does double corculatory system work?

A

2 stages

1) Blood is pumped from heart to lungs to pick up oxygen and unload carbon dioixde and rhen returns to heart (PULMONARY CIRCULATION)
2) Blood flows through heart and is pumped out to travel around the body back to heart (SYSTEMATIC CIRCULATION)

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16
Q

Summary of double ciruclatory system

A

Blood travels through the heart twice for each circuit of the body. Each smaller circuit to the lungs and to rhe body only passes through 1 capillary network so hfih pressure is maintained with fast flow of blood

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17
Q

3 liquids that make up circuiation of the body

A

Blood
Tissue fluid
Lymph

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18
Q

What does blood contain?

A

Plasma which carries a wide variety if other components like disolved glucose, amino acids, mineral ions, hormones and proteins like albumin, fibrinogen and globulins

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19
Q

Albumin fibrinogens globulins

A

Albumin - importsnt for maintaining osmotic potential
Fibrinogen - blood clotting
Globulins - transport and immune system

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20
Q

What cells does plasma carry?

A

Red blood cells which arry oxygen fo the cells
White blood cells
Platelets

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21
Q

What are platekets?

A

Fragments of large cells called megakaryocytes found in red bone marrow and are involved in clotting mechanisms

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22
Q

Plasma composition in blood?

A

On,h makes up 55% by volume - much of that volume is water ; only RBCs and Plasma involved in transport functions of the blood

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23
Q

Functions of blood in the bkdy?

A

Transport oxygen to and CO2 from respiring cells
Digested food from small intestine
Nitrogenous waste prodycs from cells to exceetory organs
Chemical messages (hormones)
Food molcules
Platelets to damaged areas
Cells and antibodies involved in immume response
ACTS AS A BUFFER minimising ph changes
MAINTAINS BODY TEMPERATURE

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24
Q

How does blood pass through capillaries?

A

Susbstanc2 dissolved in plasma can pass through the fenestrations in the capillsry walls with the exception of large plasma proteins - these proteins ALBUMIN have a osmotic pressure giving blood in capillaries a high solute potential (thus low water porential) comparied with surrounding fluid

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25
Q

Oncotic pressure?

A

As a result of low water potential in capillaries - water has a tendency to move into the blood in the capillaries from the surrounding fluid via osmosis - tendency of water to move intk the blood is termed oncotic pressure and is about -3.3kPa

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26
Q

What happens at rhe arterial end of rhe capillary?

A

As blood flows through arterioles into capillaries they are under pressure from surge of blood from heart contraction - this high HYDROSTATIC PRESSURE is more than the oncotic pressure thus fluid is forced out of the capillaries. This fluid fills the spaces between the cells and is called tissue fluid. Tissue fluid has the same composition as plasma but withiut red blood cells and proteins - diffusion takes place between the blood and the cells through the tissue fluid ; INCLUDES OXYGEN AND CARBON DIOXIDE

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27
Q

What happens at rhe venous end

A

The balance of forces change. Oncotic pressure remains the same at 3.3 but hydrostatic pressure falls as fluid is moved out - thus oncotic pressure wins and water moves back into the capillaries so by the time blood returns to veins ; 90% of the tissue fluid is back im the blood vessels.

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28
Q

Lymph

A

10% of tissue fluid that leaves the blood vessels drains into a system of blind ended tubes called lymph capillaries. Lymph is the same as plasma and tissue fluid but less oxygen and less nutrients - it also has fatty acids which have been absorbed into the lymph from the villi of the small intestine

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29
Q

What do the lymph capillaries do?

A

They join up to form larger vessels and the fluid is transported through them by squeezing body muscles - one way valves like those in valves prevent back flow and eventually the lymph returns to the blood, flowing into the right and left subclavian veins.

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30
Q

Lymph nodes?

A

Along lymph vessels are the lymph nodes - lymphocytes build up in the lymph node when necessary and produce antibodies which are then passed into the blood. The nodes also intercept bacteria and other debris from the lymph which are ingested by phagocytes found in the nodes - PLAYS A MAJOR ROLE IN THE DEFENCE MECHANISMS IF THE BODY

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31
Q

Enlarged lymph nodes

A

Are a sign that the body is fighting off an invading pathogen - this is why the doctors often examine the neck, armpits, stomach or groin of their patients - these are the sutes of some of the major lymph nodes (lymph glands)

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32
Q

Arteriole end

A

Blood coming into capillaries from the heart

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33
Q

Veinius end

A

Blood to the heart

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34
Q

LOOK AT PAGE 184 DIAGRAM

A

LOOKED 😂

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35
Q

How many pumps in the heart?

A

2 pumps - deoxygenated blood flows into the right side of the heart which pumps it in the lungs. Oxygenated blood from the lungs returns to the left side of the heart which pumps it to the body - the blood from these two sides does not mix

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36
Q

Why does the heart not fatigue?

A

Made of cardiac muscle which contracts and relaxes in a regular rhytm - does not need to rest as the coronarharteries supply the cardiac myscle with the oxygenated blood it needs to keep comtractingand relaxing all the time

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37
Q

How does the heart prevent an overflow of blood?

A

Surrounded by inelastic pericardial membranes which help prevent the heart from over-distending with blood

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38
Q

Left atrioventricular valve

A

Bicuspid

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39
Q

Right atrioventricular valve

A

Tricuspid

40
Q

Where are carotid arteries?

A

Above the aorta - 3 arteries protruding from top

41
Q

Flow of blood through deoxygenated pump

A

Enters the right atrium from both the superior snd inferior vena cava at low pressure (vein) - atria have thin walls so as blood flows in the tricuspid valve opens to allow blood to pass into the right ventricle. When both atrium and ventricle are full the atrium contracts forcing all the blood into the ventricle and stretching its walls.
As right ventricle begins to contract the tricuspid valve is closed to prevent backflow into the attium ; tendinuous cord makes sure the valves are not turned inside out by pressure exerted when the ventricle contracts. The ventricle contracts and pushes the deoxygenated blood through the semi-lunar valves into the pulmonary artery which takes it to the capillary bed in the lungs for gaseous exchange. Semi lunar valves prevent backflow into the heart

42
Q

Flow of blood through left pump

A

Oxygenated blood enters the left atrium from the pulmonary vein ; as pressure builds, bicuspid valve opens between left atrium and left ventricle so ventricle is filled with oxygenated blood. Then atrium contracts forcing all the blood imto left ventricle ; bicuspid valve closes and left ventricle contracts pumping oxygenated blood through the semilunar valves into aorta and around the body

43
Q

Why is the muscular wall on the left thicker than that on the right?

A

Lungs are close to the heart so the right sude if the heart has to pump the blood a relatively short distance and only has to overcome the resistance of pulmonary circulation. Left side has to produce suffiecient force to overcome resistance of aorta and arterial systems of the whole body and move blood under pressure to all the exteremities of the body

44
Q

What is the septum?

A

Inner dividing wall of the heart which prevents the mixing of oxygenated and deoxygenated blood ; right and left side fill and empty together

45
Q

What is the cardiac cycle?

A

The events in a single heartbeat which lasts about 0.8 seconds in a human adult

46
Q

Diastole

A

The heart relaxes - the atria and then the ventricles fill with blood ; volume and pressure of the blood in the heart build as the heart fills but the pressure in arteries is minimum

47
Q

Systole

A

Atria contract first followed by ventricular systole ; pressure inside thejewrt increases dramatically and blood is forced out of the right to the lungs and from the left to main body circulation. Blood pressure in artieries is at a high atthe end of systole and in the heart it is at a low

48
Q

Aortic pressure

A

Rises when ventricles contract as blood is forced imto aorta
Gradually falls but never less than 12kPa because od elastaxitiy fod walls which creates a recoil action to deliver blood constantly to tissues
Recoil produced a temporary rise in pressure at the start of the relaxation phase

49
Q

Atrial pressure

A

Always relatively low because walls of atrium are thin can cannot create much force ; highest when they sre contravting but drops when the bicuspid valve closes and its walls relax. Then gradial increases when atria fill uo with blood and then a slight drop again when left AV valve opens and some blood moves into the ventricle

50
Q

Ventricular pressure

A

Low at first but rises as atria contract and fils with blood - left AV valves close and pressure rises dramatically as the thick muscular walls of the ventricle contract ; as pressure > aorta then blood is forced into aorta past semilunar valves and pressure falls as the ventricles empty and the walls relax

51
Q

Ventricular volume

A

Rises as the atria contract and the ventricles fill with blood, and then drops suddnely as blood is forced out into the aorta when the semilunar valve opens. Volume increases again as the ventricles fill with blood.

52
Q

Heart sounds

A

Made by blood pressure closing the heart valves - lub-dub. The first sound comes as the blood is forced agaijst the AV-valves as the ventricles contract (close bicupsid and
tricuspid). The “duh” comes from the backflow of blood in the aorta and pulmonary artyrry which closes the semi-lunar valves as ventricles relax.

53
Q

What type 9f muscle is cardiac muscle?

A

Myogenic - has its own intrinsic rhythm at around 60bpn ; prevents bod6 wastung resources maintaining the basic heart rate. Average resting heart rate of an adult is higher at 70bpm due to factors like exercise and stress

54
Q

What is the SAN?

A

Pacemaker - initiates the heartbeat by producing a wave of electrical excitation which causes both of the atria to contract followed by the ventricles as a result of the AVN delay

55
Q

Role of SAN?

A

Wave of excitation begins in the SAN, causing the atria to contract and so initiating the heartbeat. A layer of non-conducting tissue prevents the excitation passing directly to the ventricles
A BAND HORIZONTALLY SEPARATING THE ATRIA AND VENTRICLES

56
Q

AVN role

A

Picks up the electrical activity from SAN (wave of depolarisation) ; imposes a slight delay before stimulatin the bundle of His, a bundle of conducting tissue made up of Purkyne Fibres which penetrate through thr septum between the ventricles

57
Q

Why is there a delay during the AVN?

A

This delay of 0.09 seconds ensures that the atria have ejected their blood into the ventricles first before the ventricles contract. Called a refractory period

58
Q

Where is the excitation then sent?

A

Through the bundle of His which splits into two branches and conducts the wave of excitation to the apex (bottom) of the heart. At the apex, the Purkyne fibres spread out through the walls of the ventricles on both sides - this triggers the contraction of the ventricles from the bottom, allowing more efficient emotying to push up the aorta and pulmonary artery

59
Q

Key thing aboutelectrical cardiac cycle?

A

MAKES SURE THAT ATRIA HAVE STOPPED CONTRACTING BEFORE VENTRICLES START

60
Q

What is an ECG?

A

Records the electrical activity of the heart/spread of electical excitation through the heart - it measures tiny electrical differences in your skin ehich is as a result of the electrical sctivity of the heart

61
Q

How are ECG’s carried out?

A

Eletcrodes are stuck to clean skin (oils/dirt/dry epithelial cells impede electrical flow) to get good contact needed for reliable results. ECGs are then used to diagnose heart problems ; if someone is having a heart attack recognisable changes happen in electrical activity of the heart which can be used to diagnose the problem and treat it quickly

62
Q

How much is each box of time on an ECG?

A

0.2 seconds

63
Q

Y-axis on ECG

A

mV

64
Q

P-wave

A

Inital small wave ; depolarization of atria causing contraction in response to SA node

65
Q

QRS complex

A

Depolarization of ventricles triggers main pumping contraction
Q wave = depolarisation of the septum
R wave = depolarization of main mass of ventricles thus it is the lagrest wave
S is final depolarization at apex of heart
ATRIAL RELAXATION IS DISGUISED IN TH8S WAVE

66
Q

T wave

A

Ventricular repolarization - ventricles begin to relax and pressure drops ; when it falls below atria then blood moves from atria into the ventricles via the AV valves

67
Q

When heartbeat is very rapid - over 100bpm

A

Tachycardia ; when exercising or if you habe a fever/fight or flight. If abnormal then treated wirh medication or by surgery

68
Q

When heart rate slows down to below 60bpm

A

Bradycardia - trsining makes heart beat slower and more efficiently ; severe bradycardia can be more seeious and may need an artificial pacemaker to keep the heart beating steadily

69
Q

Ectopic heart beat?

A

Extra heartbeats that are out if normal rhythm (extra systole) ; most people have at least one a day however when they are very frequent they can be linked to serious conditions

70
Q

Atrial fibrillation

A

Arrhythmia - abnormal rhythm of the heart. Rapid electrical impulses generated in the atria and fibrillate very quickly but they do not contract properly and only some of the impulses are passed on to the ventricles which contract much less often thus heart does not pump blood very effectively

71
Q

Specialised roles of erthrocytes

A

Transport of oxygen from the lungs to the cells of the body by the erthrocytes - also involved in removal of CO2 from the cells and transport to lungs for gaseous exchange

72
Q

Erthrocytes biconcave shape

A

Large SA:V ratio than a sphere ; thus increasing the rate of diffusion of gases. It also helps them pass throuh narrow capillaries as they are flexibke - this slows down rate of RBC flow so they pass through one at a time to maximise the time for diffusion

73
Q

How are erthrocytes formed?

A

Continuously in bone marrow - by the time they enter circulation they have lost their nuclei which maximises the amount of haemoglobin that fits into cells

74
Q

What is haemoflobin?

A

Red pigment that carries oxygen and also gives them their colour ; very large globular conjugated protein made up of 4 polypeptide chains ; each haemoglobin molecule can bind to 4 oxygen molecules

75
Q

How many haemoglobin molecules in each red blood cell?

A

300 million

76
Q

Oxygen and haemoglobin

A

Binds loosely to haemoglohin forming oxyhaemoglobin - this is a reversible reaction
Hb + 4O2 ->

77
Q

Describe levels of oxygen in erthrocytes in capillaries in the lungs

A

Partial pressure of oxygen in the cells is relatively low - this makes a steep concentration gradient between the erthrocytes and the lungs - oxygen then moves into the cells and binds to the haemoglobin

78
Q

What is special about haemoglobin?

A

As soon as one O2 binds to the a haem group the molecule changes shape making it easier for the next oxygen molecule to bind - this is called POSITIVE COOPERATIVITY. Because all the oxygen is bind to haemoflogin, the free oxygen concentration in the erythrocyte is low and this maintains a steep diffusion gradient until all the haemoglobin is saturated with oxygen.

79
Q

Describe oxygen levels in blood newr the tissue?

A

Concentration of oxygen in cytoplasm of body cells is lower than in the erthrocytes - as a resulr, oxygen moves out of the erthrocytes down a concentration gradient. Again once the first oxygen molecule is released by haemoglobin the molecule changes shaoe to make it essier to remove the remaining oxygen molecules

80
Q

Oxygen dissociation curve

A

Percentage saturation haemoglogin in the blood is plotted against the partial pressure of oxygen. It shows theaffinity of haemoglobin for oxygen

81
Q

How to link positive cooperativity with the curve?

A

A very small change in partial pressure of oxygen makes a significant difference to haemoglovin saturation levels due to the idea of it being easier to add more O2 molecules after the furst has changed its shape

82
Q

Why does curve level out at highest partial pressure?

A

Because all the hawm groups are bound to oxygen because all the haem groups are bound to oxygen so haemoglovin issaturated and cannot take up any more

83
Q

Relstively small drop in oxygen levels in the respiring tissues

A

Oxygen is released rapidly from the haemoglohin to diffuse into the cells - this is enhanced by relatively low pH in the tissues compared with the lungs

84
Q

Partial pressure

A

Mixture of gases = overall pressure
Each gas = contrubhtes to a part of that pressure
In a spriometer - partial pressure of oxygen decreases
Partial pressure of carbon dioxide decreases
Partial oressuee of nitrogen stays the same
Going up a mountain pressure decreases - proportion of gases psrtial pressure remains the same

85
Q

When you are not sctive?

A

Demand is low and only 25% of oxygen carried in RBCs is released to body cells - rest acts as a reservoir

86
Q

Effect of carbon dioxide

A

As partial pressure of CO2 rises - haemoglogin guves up poxygen more easily. THE AFFINITY TO RETAIN OXYGEN REDUCES. - this is known as the Bohr effect and is a shift to the right

87
Q

Effects of the Bohr Shift

A

The sctive tissues with a high partial pressure of carbon dioxide haemoglobin gives up its oxygen more readily for respiration
In the lungs where the proprtion of carbon dioxide is low, oxygen binds to the haemoglobin molecules easily

88
Q

Fetal haemoglobin

A

Detus is completely dependent on mother - pxygenated blood runs close to deoxygenated fetal blood in the placenta. If the blood of the fetus had thesame affinith for oxygen as blood of the mother then little oxygen would be transferred to the blood of the fetus. However, feta, haemoglovin has a higher affinity for oxygen than adult haemoglovin at eacn point along the chrve so it removes oxygen from the maternal blood as they move past

89
Q

3 ways carbon dioxide is transported from the tissues to the lungs

A

5% disolved in plasma
10% - 20% combines with polypeptide chains of haemoglobinto form carbaminohaemoglobin
75-85% is converted to HCO3- ions in the cytoplasm of RBCs

90
Q

Equation when carbon dioxide reacts with H2O

A

CO2 + H2O ->

91
Q

Rates of this reaction?

A

In blood plasma this is very slow however in the cytoplasm of the red blood cells theresre high levels of the enzyme carbonic anhydrase. This catalyses the reversible reaction between CO2 and H2O to form carbonic acid

92
Q

Dissociation of Carbonic acid?

A

HCO3- ions move out of the erghrocytes into the plasma via diffusion and negatively charged chloride ions move in to maintain the electrical balance of the cell. This is known as the chloride shift

93
Q

How do the erthrocytes maintain concentration gradient?

A

By converting CO2 into H2CO3 ions, they maintain a steep concentration gradient doe carbon dioxide to diffuse from the respiring tissues into the erthrocytes

94
Q

When blood reaches lungs?

A

Low concentration of CO2 - high concentration of O2 - carbonic anhydrase catalyses reverse reaction to break down carbonic acid into carbon dioxide and water.
HCO3- ions diffuse back into the erthrocytes and react with H+ to form carbonic acid. When this is broken down into CO2 - there is a high concentration of CO2 IN RBCS (thus plasma) and therefore it diffuses out of blood into the lungs to be breathed out. Cl- ions diffuse out of RBCs to maintain electrochemical gradient - back into plasma

95
Q

What role does haemoglobin play?

A

Acts as a buffer and prevents changes in the pH by accepting free H+ ions in a feversible resction to form haemoglobinic acid

A-Level Biology (37 decks)

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