3.2 TRANSPORT IN ANIMALS

Question 1

What are transport systems required for?

Answer 1

Transport systems required for:
-high metabolic demands = more o2 needed, more waste products produced
-SA:V ration decreases as organisms get bigger, SA to absorb/remove nutrients decreases
-enzyme and hormone transport
-food transport = transport of nutrients
-waste product removal

Question 2

What is mass transport?

Answer 2

Mass transport is the transport system where substances are transported in a mass of fluid
-transport system in animal is called circulatory system
= multicellular can either have an open or closed circulatory system
= components = heart (pump), blood (transport medium), blood vessels (interconnecting vessels)

Question 3

What is an open circulatory system?

Answer 3

Open circulatory system: (spiracles)
-few vessels - organs bathed directly
-haemolymph (interstitial fluid)
-haemocoel (insect body cavity)
-body movements help circulate haemolymph
-mainly insects and some molluscs
-blood doesn’t carry o2 or co2
-transports food and nitrogenous waste and cells for defence against disease
-heart extends length of thorax and abdomen

Question 4

What is a closed circulatory system?

Answer 4

Closed circulatory system:
-blood = confined to vessels
-heart = pumps blood into vessels which branch off and infiltrate organs
-chemical exchange between blood and interstitial fluid and cells
-widespread among animals
-two types = closed and double

Question 5

What is a single closed circulatory system?

Answer 5

Single closed circulatory system:
-heart has 2 chambers - atrium and ventricle
-blood passes heart once in complete circuit
-blood passes from atrium to ventricle
-blood leaves heart and travels through 2 capillary beds
-one where o2 and co2 are exchanged
-one where substances are exchanged between blood and cells
-blood pressure drops substantially as it travels through capillary bed
-blood flow back to heart is slow
-as animals muscles contract and relax, pace of circulation increases

Question 5

What is a single closed circulatory system?

Answer 5

Single closed circulatory system:
-heart has 2 chambers - atrium and ventricle
-blood passes heart once in complete circuit
-blood passes from atrium to ventricle
-blood leaves heart and travels through 2 capillary beds
-one where o2 and co2 are exchanged
-one where substances are exchanged between blood and cells
-blood pressure drops substantially as it travels through capillary bed
-blood flow back to heart is slow
-as animals muscles contract and relax, pace of circulation increases

Question 6

What is a double closed circulatory system?

Answer 6

Double closed circulatory system:
-2 circuits, 2 pumps
-pulmonary circuit
-right side of heart delivers o2 poor blood to capillaries of gas exchange tissue
-o2 into blood and co2 out of blood
-o2 enriched blood leaves gas exchange tissue and enters left side of the heart

Question 7

What is a systemic circuit?

Answer 7

Systemic circuit:
-left side of heart delivers o2 rich blood to capillary beds in organs and tissues
-o2 and co2 and nutrients are exchanged
-o2 poor blood returns to right side of the heart

Question 8

What are the advantages of open and closed systems?

Answer 8

Advantages:
open - lower hydrostatic pressure associated with open, means there is less energy expenditure
closed- relatively high blood pressure, effective delivery of o2 and nutrients for larger and more active animals

Question 9

Why are possession of large body size and high metabolic rate related to the possession of an efficient circulatory system?

Answer 9

-larger body = smaller SA:V
-less SA to absorb o2 and nutrients directly
-higher metabolic rate = more o2 needed = more waste products produced
-efficient circulatory system needed

Question 10

What are the major components of blood vessels?

Answer 10

Blood vessels:
-elastic fibres = composed of elastin and can stretch and recoil, provides cells with flexibility
-smooth muscle = contracts and relaxes changing size of lumen
-collagen = provides structural support to maintain the shape and volume of the lumen

Question 11

What arteries?

Answer 11

Arteries:
-carry blood away from heart
-mostly oxygenated blood (except pulmonary artery and umbilical artery)
-elastic fibre, smooth muscle and collagen
-elastic fibres withstand force of blood (elastic limit maintained by collagen)
-elastin fibres can also recoil between contractions to give a continuous flow of blood
-lining of the artery (tunica intima) is smooth

Question 12

What are arterioles?

Answer 12

Arterioles:
-link arteries to capillaries
-contain more smooth muscle and less elastin
-constrict and dilate in process called vasoconstriction an vasodilation = controls volume of blood that enters into capillary beds in individual organs

Question 13

What are capillaries?

Answer 13

Capillaries:
-microscopic blood vessels
-form dense networks in bodily tissues
-found between arterioles and venules
-narrow lumens (only allow one red blood cell through at a time)
-substances are exchanged through their single celled endothelial walls
-large SA for diffusion

Question 14

What are venules?

Answer 14

Venules:
-link capillaries to veins
-have very thin walls with just a smooth little muscle
-several venules join to form a vein

Question 15

What are veins?

Answer 15

Veins:
-blood moves from venules to veins
-carry blood to heart
-usually carry deoxygenated blood (except pulmonary vein and umbilical vein)
-blood pressure in veins very low
-walls contain a lot of collagen and very little elastin fibre
-have a large lumen
-lining of vein (endothelium) is smooth
-have several adaptations to transport the low-bp against gravity
-most veins have a one-way valve = prevent backflow of blood
-large veins located close to muscles = help force blood upwards upon contraction
-breathing movements of the chest act as a pump, squeezing actions push blood towards the chest

Question 16

What is the distribution of blood around the body?

Answer 16

Distribution of blood:
-54% in veins = needed to carry blood to heart, contain valves to prevent backflow of blood

artery - arteriole - capillary - venule - vein

Question 17

What is tissue fluid?

Answer 17

Tissue fluid:
-the liquid the surrounds the cells, allowing for transport between blood and cells
-formed as a result of interplay of hydrostatic pressure and osmosis (oncotic pressure)
- same composition as plasma, just without red blood cells and plasma proteins
- diffusion takes place between the blood and cells through tissue fluid

Question 18

What is hydrostatic pressure?

Answer 18

Hydrostatic pressure is pressure created by the contraction of the left ventricle (4.6kPa). the hydrostatic pressure decreases with distance with the force of the heart to about 2.3kPa

Question 19

What is oncotic pressure?

Answer 19

Oncotic pressure:
-there is a high concentration of solutes in the blood (due to bloods composition of plasma proteins such as albumin), therefore, the water potential inside the blood vessels is lower than outside the capillaries. therefore, the net movement of water is always into the capillary. the oncotic pressure of water into the blood is 3.3kPa

Question 20

What is the mechanism for hydrostatic and oncotic pressure?

Answer 20

Hydrostatic and oncotic pressure:
hydrostatic > oncotic = net flow out of capillary to form tissue fluid
hydrostatic < oncotic = net flow into capillary (90% returned)
-not all fluid passes back into capillaries
-however, the excess output needs to be collected to avoid tissue swelling
-net excess is drained into the vessels of the lymphatic system

Question 21

What is lymph fluid?

Answer 21

Lymph fluid:
-lymph passes through the lymphatic system and drains back into the circulatory system (at subclavian vein)
-contains lymphocytes
-lymph nodes intercept pathogens and are the place lymphocytes collect
-lymphocytes are part of the immune system and help filter out foreign material through the lymph
-when tissue fluid cannot be drained via lymph vessels = oedema

Question 22

What is the mechanism of the heart?

Answer 22

Mechanism of heart:
right side =
deoxygenated blood enters the right atrium through the superior/inferior vena cava at a low pressure. as blood fills the right atrium, slight pressure builds up and the tricuspid valve opens to allow blood to flow into the right ventricle. when both the atrium and the ventricle are filled with blood, the right atrium contracts, forcing all blood into the right ventricle and stretching the ventricle walls. as the right ventricle starts to contracts, the tricuspid valve closes, preventing any backflow. when the right ventricle contracts fully , deoxygenated blood is pumped through the semilunar valves into the pulmonary artery, which transports it to the capillary bed of the lungs. semilunar valves close to prevent backflow into the heart.

left side =
oxygenated blood enters left atrium through the pulmonary vein from the lungs. as pressure in the atrium builds up, the bicuspid valve opens so the left ventricle also fills with blood. when both the atrium and ventricle are full, the atrium contracts, forcing all oxygenated blood into the left ventricle. left ventricle then contracts and pumps oxygenated blood through semilunar valves into the aorta and around the body. as the ventricle contracts, tricuspid valves closes, preventing any backflow of blood. walls of left ventricle are much thicker to withstand the high pressure of pumping pressure to the entire body.

Question 23

What is the cardiac cycle?

Answer 23

The cardiac cycle is the events of a single heart beat, which lasts about 0.8 seconds in a human adult
1. atrial systole
2. ventricular systole
3. diastole
- during systole, the atria contract (atrial), closely followed by the ventricles (ventricular). the pressure inside the heart increases dramatically and blood is forced out of the right side of the heart to the lungs and from the left side to the main body. the volume and pressure of the blood in the heart are low at the end of systole and the blood pressure in the arteries is at a maximum
- in diastole, the heart relaxes. the atria and then the ventricles fill with blood. the volume and pressure of the blood in the heart build as the heart fills, but the pressures in the arteries is at a minimum

Question 24

Sounds of heart.

Answer 24

Sounds of heart:
-sound of heartbeat can be heard through a stethoscope and is made by blood pressure closing the heart valves
-electrocardiograms can be used to measure the spread of electrical activity in the heart
- lub = AV valves shut
- dub = semi-lunar valves shut

Question 25

What is cardiac output?

Answer 25

Cardiac output is the amount of blood the heart pumps through the circulatory system in a minute

Question 26

What is stroke volume?

Answer 26

Stroke volume is the amount of blood pumped by the left ventricle of the heart in one contraction

Question 27

What is heart rate?

Answer 27

Heart rate is the number of beats per unit of time

Question 28

How do you calculate cardiac output?

Answer 28

Cardiac output = stroke volume x heart rate

Question 29

What is myogenic?

Answer 29

Myogenic is a property of cardiac muscle. it’s contraction is initiated within the muscle itself, not by impulses from a nerve

Question 30

Nodes and bundles.

Answer 30

Nodes and bundles:
-sino-atrial node (SAN) = natural pacemaker, initiates atria to contract, therefore initiating the heartbeat
-atrioventricular node (AVN) = delays the impulse and sends the wave of excitation down the bundle of his
-bundle of his = bundle of conducting tissue made of purkyne fibres that penetrate through the septum between the ventricles

Question 31

What is the electrical coordination of the heartbeat?

Answer 31

Electrical coordination of heartbeat:
1. 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
2. the electrical activity from the SAN is picked up by the AVN, which imposes a slight delay before stimulating the bundle of His, a bundle of conducting tissue made up of fibres (purkyne fibres) which penetrate through the septum between ventricles
3. the bundle of His splits into two branches and conducts the wave of excitation to the apex of the heart
4. at the apex, the purkyne fibres spread out through the walls of ventricles on both sides. the spread of excitation triggers the contraction of the ventricles, starting at the apex. contraction starting at the apex allows more efficient emptying of the ventricles
* the way in which the wave of excitation spreads through the heart from the SAN, with AVN delay makes sure that the atria have stopped contracting before the ventricles start

Question 32

What are electrocardiograms?

Answer 32

Electrocardiograms:
-measure electrical differences in skin (electrodes) as a result of electrical activity of the beat
- measure of the spread of electrical excitation through the heart as a way of recording what happens as it contracts
-p wave = electrical activity of atrial systole
-QRS wave = electrical activity of ventricular systole
-t wave = ventricular diastole
- normal adult resting heart rate is 70 bpm

Question 33

How does hb carry o2?

Answer 33

Carrying o2:
-around 30 million hb per rbc
-each subunit has 1 haem group (fe)
-each haem group binds to 1 o2
-when o2 binds to hb it becomes oxyhaemoglobin = process of gaining o2 is called loading, hb + 4o2 = hb(o2)4
- each hb can bind to 4 o2 molecules

Question 34

What is oxygen affinity?

Answer 34

Oxygen affinity:
-a measure of how easily the haem group can bind to o2
-hb shows positive cooperativity
-as o2 binds to hb, it causes the neighbouring chains to take shape, making it easier to bind (increases hb’s affinity to o2)

Question 35

Loading and partial pressure.

Answer 35

Loading and partial pressure:
-ability for hb to load with o2 depends on partial pressure
-all gases exert a pressure. total pressure is pressure of all gases in an area
-partial pressure of o2 is the force exerted by the o2 molecules in the air
-therefore partial pressure is proportional to concentration of that gas
-o2 tension means the partial pressure of o2 within plasma
-higher partial pressure of o2 in alveoli so hb loads to o2
-lower partial pressure of o2 in tissue so hb unloads o2

Question 36

Oxygen dissociation curve.

Answer 36

Oxygen dissociation curve:
-s shaped
1. difficult to load o2 at low pp. but it allows for rapid unloading of o2
2. after first successful collision of o2 and haem group, the shape of neighbouring polypeptide chains changes, increasing the hbs affinity leading to rapid loading = positive cooperativity
3. due to high pp of o2 there are frequent collisions between o2 and hb. if o2 collides with a non-saturated haem group loading will occur

at the high po2 in the lungs the hb in rbcs is rapidly loaded with o2. equally, a small drop in o2 levels in respiring tissues means o2 is released rapidly from hb. this effect is enhanced by low pH in tissues compared with in the lungs. when not active, only about 25% of the o2 carried in rbcs is released to body cells. rest acts as a reservoir for when the body needs it

Question 37

Transporting o2.

Answer 37

Transporting o2:
-hb helps transport co2 and buffers the blood
-3 main pathways
1. only about 5% of co2 is transported in blood plasma
2. 10-20% forms carbaminohaemoglobin inside rbc
3. 85% goes directly into the rbc and undergoes a series of reactions co2 + h20 - h2co3 (carbonic acid)
= carbonic acid dissociates into H+ ions which combine with hb to form haemoglobnic acid - process causes hb to release o2 to cells, hb acts as a buffer and stops H+ altering cells pH
= carbonic acid dissociates gp hco3- hydrocarbonate ions which diffuse out of blood plasma and from the plasma chloride ions diffuse back into the rbc to maintain the charge of the cell (chloride shift)
= co2 to h2co3 maintains the concentration gradient for co3 in the rbc

Question 38

What is Bohr shift?

Answer 38

Bohr shift is the decrease in the affinity of hb for o2 in the presence of co2

Question 39

How does Bohr shift work?

Answer 39

How Bohr shift works:
- in active tissues, with a high pco2, hb gives up its oxygen more readily
- in the lungs where the proportion of co2 in the air is low, o2 binds to hb molecules easily
- as pco2 increases, oxygen dissociation curve shifts to the right
- co2 can be transported to the lungs by being dissolved in plasma (5%), combine with amino groups to form carbaminohb (10-20%), and converted to HCO3- in cytoplasm of rbcs (75-85%)
CO2 + H2O = H2CO3 = HCO3- + H+
- in plasma this happens slowly, in cytoplasm of rbc there are high levels of carbonic anhydrase, which catalyses the reaction
- HCO3- moves out of rbcs into plasma by diffusion and Cl- move into rbcs, which maintains the electrochemical balance of cells = chloride shift
- by converting CO2 to HCO3- rbc maintains a steep concentration gradient for CO2 to diffuse into rbcs from tissues
- reaction reversed when blood reaches the lungs, Cl- leaves
- hb acts as a buffer and prevents changes in pH by accepting free H+ ions in a reversible reaction to form haemoglobnic acid

Question 40

Why does more respiration happen in muscle cells?

Answer 40

Muscles - more aerobic respiration for ATP - more co2 = more carbonic acid = more H+ ions = more o2 as H+ displaces o2

Question 41

What is fetal haemoglobin?

Answer 41

Fetal hb:
-has a higher affinity for o2 than adult hb
-oxygenated blood from placenta runs close to deoxygenated blood from fetus
-fetal haemoglobin combines more readily with o2 so it is then able to remove o2 straight from the placenta
- fetus is completely dependent on the mother supplying it oxygen
- oxygenated blood from the mother runs close to the placenta
- low po2 in placenta, so fetal hb needs higher affinity for oxygen otherwise it would gain little or no o2 from the mothers blood

Question 42

Fetal vs adult hb.

Answer 42

Fetal vs adult hb:
-fetal hb good at taking in o2 = 2 alpha chains, 2 gamma chains
-fetal hb must be replaced with adult hb as it holds onto o2 and struggles to release it

Question 43

What are the functions of the blood?

Answer 43

Functions of the blood:
transport of
- oxygen to and carbon dioxide from the respiring cells
- digested food from the small intestine
- nitrogenous waste products from the cells to the excretory glands
- chemical messages (hormones)
- platelets to damaged areas
- cells and antibodies involved in the immune response
. also contributes to maintenance of a steady body temp and acts as a buffer, minimising pH changes

Question 44

How is tissue fluid formed?

Answer 44

Tissue fluid formation:
1. substances dissolved in plasma can pass through fenestrations in capillary walls, except large plasma proteins.
2. plasma proteins, especially albumin, have an oncotic effect. they give the blood in capillaries relatively high solute potential (and so a low water potential) compared with the surrounding fluid. as a result, water has a tendency to move into the blood in capillaries, which is known as oncotic pressure
3. however, as blood flows through the arterioles into the capillaries, it is still under pressure from the surge of blood that occurs every time the heart contracts, which is known as hydrostatic pressure
4. at the arteriole end of the capillary, hydrostatic pressure forcing fluid out of the capillaries is 4.6kpa, which is higher than the oncotic pressure. this means fluid is squeezed out of the capillaries, which then fills spaces between cells and is known as tissue fluid

5. then, as blood moves through the capillaries towards the venous system, the balance changes and hydrostatic pressure falls to 2.3kpa, which is now less than the oncotic pressure
6. this forces water to move back into the capillaries by osmosis as it reaches the venous end
7. by the time blood returns to the veins, 90% of tissue fluid is back in blood vessels

Question 45

How is lymph fluid formed?

Answer 45

Lymph fluid formation:
1. 10% of tissue fluid does not return to the capillaries, and this 10% drains into a system of blind-ended tubules called lymph capillaries, where it is known as lymph
2. lymph capillaries join up to form up larger vessels
3. lymph fluid is transported by the squeezing of the body muscles, one way valves prevent the backflow of blood
4. eventually lymph returns to the blood, flowing into the right and left subclavian veins

Question 46

How is o2 carried to cells?

Answer 46

Carrying o2:
- when erythrocytes enter capillaries in lungs they o2 levels in cells are low which makes a steep concentration gradient between the inside of erythrocytes and the air in the alveoli
- o2 moves into rbcs and binds to hb
- the arrangement of the hb molecules binds to a haem group, the molecule changes shape, making it easier for the next o2 molecule to bind = positive cooperativity
- steep diffusion gradient is maintained until all hb is saturated with o2
- when blood reaches the body tissues, the situation is reversed. the conc of o2 in the cytoplasm of body cells is lower than inside rbcs
- as a result o2 moves out down conc gradient
- once first o2 molecule is released by hb, the molecules then changes shape and it is easier for more o2 to detach from hb

Question 47

What are the properties of cardiac muscle?

Answer 47

Properties of cardiac muscle:
- makes up heart which contracts and relaxes in a regular rhythm
- does not get fatigued and need to rest like skeletal muscle
- coronary arteries supply the cardiac muscle with the oxygenated blood it needs to keep contracting and relaxing all the time
- heart is surrounded by inelastic pericardial membranes, which help prevent the heart over-distending with blood
- myogenic so it has its own intrinsic rhythm and prevents the body wasting resources to maintain the heartbeat

Question 48

What is tachycardia?

Answer 48

Tachycardia is when the heartbeat is very rapid, usually over 100bpm. This is often normal when exercising, if having a fever, or are scared of angry. If it is abnormal it may be caused by problems in the electrical control of the heart.

Question 49

What is bradycardia?

Answer 49

Bradycardia is when the heart rate slows down to below 60bpm. Many people have bradycardia because they are fit. Severe bradycardia can be serious and may need an artificial pacemaker to keep the heart beating steadily.

Question 50

What is an ectopic heartbeat?

Answer 50

An ectopic heartbeat is when there are extra beats out of the normal rhythm. Most people have at least one a day. They are usually normal but they can be linked to serious conditions when they are frequent.

Question 51

What is atrial fibrilation?

Answer 51

Atrial fibrilation is an example of an arrythmia (abnormal rhythm of the heart). rapid electrical impulses are generated in the atria. They contract very fast (fibrilate) up to 400 times a minute. However, they don’t contract properly and only some impulses are passed on to the ventricles, which contract much less often. As a result, the heart does not pump blood very effectively.

Question 52

What is blood pressure?

Answer 52

Blood pressure:
- the blood travels through the arterial system at pressures that vary as the ventricles contract
- the blood pressure is also affected by the diameter of the blood vessels themselves
- narrowing the arteries is one way in which the body affects and controls local blood flow, but permanent changes can cause severe health problems

Question 53

What effects do the components of tobacco smoke have on the cardiovascular system?

Answer 53

Tobacco smoke contains nicotine (which is a highly addictive substance) and carbon monoxide. Nicotine increases the stickiness of platelets which may cause the blood to clot inside the body. Nicotine also induces the release of the hormone adrenaline, which constricts arterioles and causes a reduced blood flow to vital organs and respiring tissues. Carbon monoxide irreversibly binds to haemoglobin, reducing the oxygen carrying capacity of the blood.