3.1.2 Transport in animals Flashcards
Explain the need for transport systems in multicellular animals:
multicellular animals relatively big so harder to supply cells with everything they need
- LOW SA : V RATIO
- HIGH METABOLIC RATE
also lots of mammals are very active
- larger no. of cells respiring quickly so need constant supply of glucose and oxygen
to make sure that every cell has a good enough supply need transport system
Describe the single circulatory system
blood only passes through the heart once for each complete circuit of the body
Describe the double circulatory system
blood passes through the heart twice for each complete circuit of the body
Describe the circulatory system in fish
single closed circulatory system
the heart pumps blood to the gill (to pick up oxygen) and then on through the rest of the body (to deliver the oxygen) in a single circuit
Describe the circulatory system in mammals
double closed circulatory system
heart is divided down the middle
- the right side of the heart pumps blood to the lungs (to pick up oxygen)
- from the lungs it travels to the left side of the heart which pumps it to the rest of the body
- when blood returns to the heart it enters the right side again
blood to lungs = pulmonary system
blood to body = systemic system
Advantages of the mammalian double circulatory system?
the heart can give the blood an extra push between lungs and the rest of the body.
- blood travels faster
so oxygen delivered to tissues more quickly
Describe the closed circulatory system
the blood is enclosed inside the blood vessels
- the heart pumps blood into arteries, these branch out into millions of capillaries
- substances like oxygen and glucose diffuse from the blood into capillaries into the body cells, but the blood stays inside the blood vessels as it circulates
- veins take the blood back to the heart
Describe the open circulatory system
blood isn’t enclosed in vessels all the time
instead, it flows freely through the body cavity
- the heart is segmented. it contracts in a wave starting from the back, pumping the blood into a single main artery
- that artery opens up into the body cavity
- the blood flows around the insect’s organs, gradually making its way back into the heart through a series of valves
eg. insects
the circulatory system supplies the cells with nutrients and transports things like hormones around the body
doesn’t supply cells with oxygen, this is done by the tracheal system
Function of arteries
carry blood from the heart to the rest of the body
all arteries carry oxygenated blood except the Pulmorary artery which takes deoxygenated blood to the lung
Structure of arteries
Thick and muscular walls - have elastic tissue to stretch and recoil as the heartbeats - which helps maintain the high blood pressure
Inner lining (endothelium) is folded - allowing the artery to expand - helps maintain high blood pressure
Function of arterioles
arteries branch into arterioles
they control the amount of blood flowing into tissues
Structure of arterioles
much smaller than arteries
less elastic tissue than arteries
have a layer of smooth muscle allowing them to expand or contract
Function of capillaries
arterioles branch into capillaries
substances like glucose and oxygen are exchanged between cells and capillaries
Structure of capillaries
smallest blood vessel
cell wall only one cell thick so adapted for efficient diffusion
Function and structure of venules
capillaries connect to venules
venules have very thin walls that can contain some muscle cells
they join together to form veins
Function of veins
veins take blood back to the heart under low pressure
all veins carry deoxygenated blood, except pulmonary veins which can carry oxygenated blood from lungs to heart
Structure of veins
wider lumen than arteries
very little elastic or muscle tissue
have valves to stop the blood flowing backwards
blood flow through veins is helped by contraction of the body muscles surrounding them
What is tissue fluid?
the fluid that surrounds cells in tissues
cells take in oxygen and nutrients from the tissue fluid and release metabolic waste into it
What is tissue fluid made from?
made from substances that leave the blood plasma
eg. oxygen, water and nutrients (no red blood cells) or big proteins as too large to be pushed through capillary walls)
How is tissue fluid formed?
In a capillary bed (the network of capillaries in an area of tissue) substances move out of the capillaries into the tissue fluid, by PRESSURE FILTRATION:
- at the start of the capillary bed, nearest the arteries, HYDROSTATIC pressure INSIDE capillaries is HIGHER than the hydrostatic pressure in the tissue fluid
- this difference in pressure forces fluid out of the capillaries and into spaces around the cells, forming tissue fluid - as fluid leave, the hydrostatic pressure REDUCES in the CAPILLARIES so hydrostatic pressure is much LOWER at the END of the CAPILLARY BED (nearest the venules)
- there is another form of pressure at work, ONCOTIC pressure. This is generated by plasma proteins present in capillaries which LOWER the WATER POTENTIAL
at the VENULE END the WATER POTENTIAL in capillaries LOWER than in tissue fluid (due to fluid loss from capillaries and high oncotic pressure) so some WATER RE-ENTERS capillaries from the tissue fluid at the venule end by osmosis
Formation of Lymph
excess tissue fluid drains into the lymph vessels (not all of it re-enters capillaries at venule end)
- the smallest lymph vessels are the lymph capillaries
- excess tissue fluid passes into lymph vessels, once inside called lymph
- valves in the lymph vessels stop the lymph going backwards
- lymph gradually moves towards the main lymph vessels in the thorax (chest cavity)
- here it is returned to the blood, near the heart
What is the Lymphatic system?
extra tissue fluid eventually gets returned to the blood
it is like a drainage system made up of lymph vessels
What is in blood?
red blood cells
white blood cells
platelets
proteins
water (lower water potential than tissue fluid and lymph)
dissolves solutes
What is in tissue fluid?
very few white blood cells
very few proteins
water (higher water potential than blood)
dissolves solutes
What is in lymph?
white blood cells (most white blood cells are in lymph system and only enter tissue fluid when there’s an infection)
proteins - only antibodies
water (higher water potential than blood)
dissolves solutes
What is the cardiac cycle?
an ongoing sequence of contraction and relaxation of the atria and ventricles that keep blood continuously circulating round the body
the volumes of the atria and ventricles change as they contract and relax, altering the pressure in each chamber
this causes valves to open and close, which directs the blood flow through the heart
What are the three stages of the cardiac cycle?
- ventricles relax, atria contract (atrial systole)
- ventricles contract, atria relax (ventricular systole)
- ventricles relax, atria relax (diastole)
cardiac cycle - 1. ventricles relax, atria contract (atrial systole)
the ventricles are relaxed
the atria contract - decrease vol. and increase pressure
- this pushes blood into the ventricles through the atrioventricular valves
- there is slight increase in ventricular pressure and vol. as ventricles receive ejected blood from contracting atria
cardiac cycle - 2. ventricles contract, atria relax (ventricular systole)
the atria relax
the ventricles contract (decrease vol.) increasing pressure.
- the pressure becomes higher in the ventricles than the atria, this forces the atrioventricular valve shut to prevent backflow
- the high pressure in the ventricles opens the semi-lunar valves, blood os forced out into the pulmonary artery and aorta
cardiac cycle - 3. ventricles relax, atria relax
the ventricles and atria both relax
the higher pressure in the pulmonary artery and aorta causes the semi-lunar valves to close, prevents backflow
the atria fill with blood (increasing their pressure) due to the higher pressure in the vena cave and pulmonary vein.
as the ventricles continue to relax, their pressure falls below pressure in the atria
this causes atrio-ventriclar valves to open and blood flows passively into the the ventricles from the atria
the atria contract and the whole process begins again
What is cardiac output?
the vol. of blood pumped by the heart per minute
How do you work out cardiac output?
cardiac output = heart rate x stroke volume
measured in cm^3 min^-1
What is heart rate?
the number of beats per minute
What is stroke volume?
the vol. of blood pumped during each heartbeat in cm^3
How is heart actions initiated and coordinated?
cardiac muscle is myogenic - it can contract and relax without receiving signals from nerves
this pattern of contractions controls the regular heartbeat
initiated and coordination of regular heart beat
- the process starts with sino-atrial node (SAN) in the right atrium
- the SAN is like a pacemaker - its sets the rythmn of the heart beat by sending out regular waves of electrical activity to the atrial walls
- this causes the right and left atria to contact at the same time
- a band of non-conducting collagen tissue prevents the waves of electrical activity from being passed directly from the atria to the ventricles
- instead, these waves of electrical activity are transferred from the SAN to the atrio-ventriclar node (AVN)
- the AVN is responsible for passing the waves of electrical activity on to the bundle of His
- but there is a slight delay before the AVN reacts to make sure venticles contract after the atria have empties - the bundle of His is a group of muscle fibres responsible for conducting the waves of electrical activity o the finer muscle fibres in the right and left ventricle walls called the Purkyne Fibres
- the Purkye tissues carries the waves of electrical activity into the muscular walls of the right and left ventricle, causing them to contract simultaneously from the bottom up
what is an electrocardiograph?
a doctor can check someone’s heart function using an electrocardiograph
its a machine that records the electrical activity of the heart
the heart muscle depolarises (loses electrical charge) when it contracts it repolarises (regains charge) when it relaxes
an electrocardiograph records these changes in electrical charge using electrodes places on the chest
Draw an electrocardiograph
P-wave - caused by contraction (depolarisation) of the atria
QRS complex - the main peak of the heart beat caused by contraction of the ventricles
T-wave - due to relaxation of the ventricles
electrocardiograph - what does the height of the wave mean?
the height of the wave indicates how much electrical charge ispassing through the heart
- a bigger wave means more electrical charge so for P and R waves a bigger wave means a stronger contraction
what is tracycardia?
when the heart beat is too fast (at rest)
shows heart isnt pumping blood effectively
120bpm
what is bradycardia?
when heart beat is too slow
below 60bpm
What is an ectopic heartbeat?
when there is an extra heartbeat
caused by earlier contraction of the atria or early contraction of the ventricle
(occasional ectopic heartbeats in a healthy person don’t cause a problem)
What is fibrillation?
a really irregular heartbeat
the atria or ventricles completely lose their rhythm and stop contacting properly
can result in anything from chest pain to lack of pulse to death
How is oxygen carried around the body?
as oxyhaemoglobin
Why can red blood cells carry oxygen?
red blood cells contain haemoglobin
hb is a large protein made up of 4 polypeptide chains
each chain has a haem group which contains iron
hb has a high affinity for oxygen - each molecule can carry four oxygen molecules
(in the lungs oxygen joins to the iron in hb to form oxyhb)
Hb + 4O2 < —-> HbO8
What does Haemoglobin saturation depend on?
the partial pressure of Oxygen
- this is a measure of oxygen concentration
- the greater the conc. dissolved in cells the higher the partial pressure
Explain how Partial pressure of oxygen affect haemoglobin saturation
oxygen loads onto Hb to form oxyHb where there’s a high pO2
eg. alveoli
oxyHb unloads its oxygen where there’s a lower pO2
eg. respiring cells
What is the Bohr effect?
when more CO2 is present (high pCO2) more oxygen is released from the blood
because
the lower the saturation of Hb with O2, the more O2 is released
(dissociation curve shifts right)
Why is the Bohr effect good?
respiring cells produce CO2, which raises pCO2, increasing the rate of oxygen unloading
its means cells have more oxygen during activity
How is CO2 removed from the body? (long version)
- most of the CO2 from respiring cells diffuses into red blood cells
- here it reacts with water to form carbonic acid
- this is catalyzed by the enzyme carbonic anhydrase
(about 10% of CO2 binds directly to Hb and is carried to the lungs) - carbonic acid dissociates —-> H+ ions + hydrogencarbonate (HCO3-) ions
- this increase in H+ ions causes oxyHb to unload its oxygen so that Hb can take up H+ ions
- this forms haemoglobinic acid (stops H+ ions decreasing cell’s acidity) - The HCO3- ions diffuse out of the rbc and are transported into the blood plasma
- to compensate for loss of HCO3-, chloride (Cl-) ions diffuse into rbc - chloride shift - to maintain balance of charge between rbc and plasma - when blood reaches the lung the low pCO2 causes some of the HCO3- and H+ to recombine into CO2 and water
- CO2 then diffuses out into the alveoli and is breathed out
How is CO2 removed from body? (short version)
- most of the CO2 from respiring cells diffuses into red blood cells
- CO2 + H2O —-> carbonic acid
- catalyzed by carbonic anhydrase - carbonic acid dissociates —-> H+ ions + hydrogencarbonate (HCO3-) ions
- H+ ions conc. increases = oxyHb unloads oxygen = Hb can take up H+ ions
- forms haemoglobinic acid (stops H+ ions decreasing cell’s acidity) - HCO3- ions diffuse out of the rbc (transported into the blood plasma)
- chloride shift Cl- ions into rbc, to maintain balance of charge between rbc and plasma - when blood reaches the lungs low pCO2 causes some of the HCO3- and H+ to recombine into CO2 and water
- CO2 then diffuses out into the alveoli and is breathed out
what does an oxygen dissociation curve show?
how saturated the haemoglobin is with oxygen at any given partial pressure
Shape of oxygen dissociation curve? why?
S-shaped
because;
when Hb combines with the first O2 molecule its shape alters in a way that makes it easier for other molecules to join too
when Hb becomes saturated harder for molecules to join
as a result curve has a steep bit in the middle where its v. easy for O2 to join and shallows at each end where its harder
Does fetal haemoglobin have a higher affinity for oxygen than adult Hb?
Yes
oxygen dissociates curve shifts left
Why does fetal Hb need a higher affinity for O2 than adult Hb?
the fetus gets its oxygen from the mother’s blood across the placenta
by the time the mother’s blood reaches the placenta its oxygen saturation has decreased (used by mother’s cells)
for the fetus to get enough oxygen to survive its Hb has to have a higher affinity for oxygen (so it takes up enough)
if its Hb has the same affinity for oxygen as adult Hb its blood wouldn’t be saturated enough
