Transport in Animals Flashcards
Explain why multicellular organisms need a transport system
- large organisms, this increases the distance of the diffusion pathway and decreases the rate of diffusion. the outer cells will use up the supplies leaving inner cells without.
- more metabolic activity so needs a good supply of energy for movement (need to keep warm)
- small SA:V so need a specialised system
- large demand for oxygen and removal of waste products
- active
Define and draw single and double circulatory system
Single = blood flows through heart once for each circuit Double = blood flows through the heart twice for each circuit and has 2 circuits
What are the advantages of a double circulatory system?
Single = blood pressure drops at the capillaries so blood flows slowly so rate of delivery is limited Double = blood pressure can't be too high or will damage the capillaries in the lungs, but the heart can increase the pressure after in passed through the lungs, increasing blood flow
Define open circulatory system and the disadvantages of it
Blood flows freely through their body cavity carrying nutrients.
Blood pressure is low so blood flow is low
Circulation can be affected by body movements
Define closed circulatory system and the advantages of it
Blood flows through blood vessels often with a heart
Higher blood pressure so blood flow is quicker
More rapid delivery of oxygen/ nutrients
More rapid removal o CO2 and waste products
Independent of body movements
Describe how an insect pumps blood around its body
The heart is under the dorsal surface. Blood enters the heart via ostia (pores). Blood is pumped towards the head by peristalsis.
Draw an artery, vein and capillary and label them
Lumen, endothelium, elastic fibres, smooth muscle, collagen fibre should be included and organised into tunica interna, media and externa.
Describe the differences between function, transport and wall thickness in the blood vessels
Arteries
- carries oxygenated (expect the pulmonary artery) blood away from the heart to the rest of the body
- very thick to withstand the pressure
Veins
- carries deoxygenated blood (except the pulmonary vein) to the heart
- thin to allow low pressure
Capillaries
- exchange surface between blood and cells
- very thin for efficient exchange short diffusion distance
Describe the differences between the lumen, endothelium and elastic fibers in the blood vessels
Arteries
- lumen is relatively small to maintain pressure
- endothelium is folded to allow the lumen to expand as blood flow increases
- elastic fibres allow walls to stretch and recoil to change diameter (which is felt as a pulse) to maintain high blood pressure when the heart is at rest
Veins
- lumen is large to ease flow of blood
- endothelium contains a layer of cells
- elastic fibres are thinner layers and not needed as they aren’t used to reduce blood flow
Capillaries
- Lumen is very narrow so blood cells are squeezed to decrease the diffusion distance
- endothelium is only one layer of cells (leaky)
Describe the differences between the smooth muscle, collagen fibres and valves in blood vessels
Arteries
- smooth muscle can contract and constrict to change dimeter of the lumen
- collagen fibres gives strength to withstand high pressure
- no valves as pressure is so high
Veins
- thinner layers of muscle its not needed
- collagen fibres are thinner layers and not needed because blood isn’t transported at high pressure
- valves prevent back flow of blood in opposite direction (unefficient)
Capillaries
- no smooth muscle, collagen fibres or valves
What are arterioles and venules? Relate their structure to their function.
Arterioles are small vessles that distribute blood from arteries to capillaries. Smooth muscleis used to limit blood flow to certain areas so it can be redirected to other tissues.
Venules collect blood from capillary bed and lead to the veins.
Smaller than arteries and veins so change in pressure is more gradual.
Describe the differences between blood plasma, tissue fluid and lymph in cells, proteins and fats
Blood plasma - erthrocytes, leucocytes, platelets - hormones and plasma proteins - some fat transported in lipoproteins Tissue fluid - some white blood cells - some hormones - no fats Lymph - lymphocytes - some proteins - more fats especially near the digestive system
Describe the differences between blood plasma, tissue fluid and lymph in glucose, amino acids and oxygen
Blood plasma - 80-120 per 100cm3 - more - more Tissue fluid - less (absorbed by body cells) - less (absorbed) - less (absorbed) Lymph - less - less - less
Describe the differences between blood plasma, tissue fluid and lymph in carbon dioxide, hydrostatic and oncotic pressure
Blood plasma - little - high - more negative Tissue fluid - more (released from body cells) - low - less negative Lymph - more - low - less negative
Describe the formation of tissue fluid
At the arterial end of the capillary, hydrostatic pressure is high(er than Wp) therefore plasma moves out of the capillaries because pressure is higher inside than outside so moves down a pressure gradient
Plasma proteins are too large to pass through so stay in the plasma, lowering water potential so tissue fluid moves back into the capillaries at the venous end
Draw the pressures influencing movement of fluids during exchange at the capillaries
Drawing including labels of arteriole and venule end with arrows of hydrostatic and oncotic pressure with correct numbers. Arteriole end has a net of 1.2kPa and venule has net of -1.5kPa
Describe what lymph is and lymph nodes
Tissue fluid that has drained into the lymphatic system and returns back into the blood stream via the subclavian vein (chest). Lymph nodes are swellings found along the lymphatic system and filter bacteria and forgein material so phagocytes can engulf them
Draw the heart and label it
Should include, pulmonary artery and vein, the aorta, vena cava, artria and ventricles, the 4 valves, the ventricular septum and the tendious cords
Draw a table with the 3 heart chambers down the side and wall, pressure and explaintion across
Atria - thinnest - lowest - distance from atria to ventricle is small Right ventricle - thin - low - so that capillaries in the lungs aren't damaged and the blood is going a short distance to the lungs Left ventricle - thickest - high - distance is very long between heart and rest of body and high pressure to overcome the resistance of systemic circulation
Describe the 3 steps of dissections
- identify features
- cut into each ventricle and note the thickness with a ruler (using scissors is safer than a scalpel)
- cut upwards towards the atria to expose the atrio-ventricular valve. note the action of the valves and the role of the tendious cords
Describe cardiac muscle
- fibres that branch = cross bridges. - spread stimulus around the heart squeezing action
- mitochondria between myofibrils to supply energy during contraction
- separated by intercalated discs help synchronised pump
- cells are divided into sacromeres (contractile units)
Explain what happens during atrial systole (ventricular distole)
- Blood enters the atria and the pressure inside the atria increases (semi lunar valves are closed due to pressure in major arteries being higher than in ventricles)
- The pressure is higher in the atria than in the ventricle so the atrio-ventricular valves open
- The atria contracts pushing blood into the ventricles
Explain what happens during ventricular systole (atrial distole)
- Blood enters the ventricles and the pressure increases
- The pressure becomes higher in the ventricles than in the atria forcing AV valves to shut (prevent backflow)
- the closure is caused by a swirling action in blood around valves when ventricle is full
- during ventricular systole the pressure rises and blood starts to move upwards; this movement fills the valve pockets and keeps them closed (tendinous cords prevent them from turning inside out) - The pressure in the ventricles in higher than that of the major arteries so the semi lunar valves open
- Ventricles contract and blood is forced out into the ventricles
Explain what happens during distole
- The atria and ventricles are relaxed
- The pressure is higher in the major arteries so the semi-lunar valves close to prevent the backflow of blood
- as ventricles drop below pressure in major arteries the blood starts to flow back
- SL valves pushed closed by the blood collecting in the pockets of the valves (pulse) - Pressure is slightly higher in the atria than ventricles so AV valves open
- Blood flows passively into the ventricles from the atria
Draw the graph of pressure changes in the heart and label it
- Should show first section before AV valves close is atrial systole
- Shows that ventricular systole ends when the semi lunar valves shut
- Shows diastole
- Shows when all the valves open and close
- Label whcih line is aortic, ventricle and atrial pressure
Explain the trend in blood pressure at different parts of the blood system
- pressure fluctuates in the aorta because of diastole and systole (increase)
- pressure decreases as it moves further away from the heart because blood vessles branch into smaller vessles (cross sectional area increases)
- pressure lower at the capillaries only one cell thick so high pressure would cause them to burst (haven’t got elastic tissue)
- slow rate allows time for exchange
- pressure is very low at the veins so muscles around it and valves (prevent back flow) help the blood be pumped to the heart
Describe the contraction of the artria
- Cardiac muscle is myogenic
- the SAN initiates a wave of excitation in the right atrium
- It travels along the membranes, causing the cardiac muscle to contract
- This is atrial systole
Why can’t the wave of excitation move into the ventricles and why is this beneficial?
The tissue at the base of the atria is unable to conduct the wave of excitation so it can’t spread directly down the ventricle walls. At the top of the septum is the AVN node; this is the only route that can conduct the wave through the ventricles. It is delayed in the node this allows time for the atria to finish contracting and for blood to flow down into the ventricles before they begin to contract.
Describe the contraction of the ventricles
- The wave is carried away from the AVN and down specialised conducting tissue called the Purkyne tissue in the septum
- At the base of the septum teh wave spreads out over the walls of the ventricles
- As the wave spreads upwards from the apex it causes muscles to contract (ventricular systole)
- This pushes the blood up towards the major arteries at the top of the heart
Draw a section of a normal ECG and label
P wave (atrial stimulation) QRS waves (shows ventricular stimulation) T wave (shows diastole)
What kind of heart beats are there? Can you sketch some?
Sinus rhythm (normal)
Bradycardia (slow)
Tachycardia (fast)
Atrial fibrillation (atria beating more than ventricles no clear P wave seen)
Ectopic heartbeat (every third beat is early)
Describe the events when carbon dioxide enters a erythrocyte
- carbon dioxide reacts with water forming carbonic acid, this is catalysed by carbonic anyhydrase
CO2 + H2O = H2CO3 - dissociation of carbonic acid
H2CO3 = HCO3- + H+ - hydrogencarbonate ions diffuse into the plasma from the erythrocyte
- chlorise ions diffuse into erythrocyte from the plasma, called the chloride shift
- hydrogen ions are taken out by associating with haemoglobin to produce haemoglobinic acid HHb (acts as a buffer)
Explain the movement of plasma across a capillary at the venule and arteriol end
The oncotic pressure is smaller than the hydrostatic pressure at the arteriole end so tissue fluid moves out. The oncotic pressure is greater than the hydrostatic pressure at the venule end so tissue fluid moves into the capillary.
Explain what haemoglobin is
A protein with 4 sub units (quaternary) Each sub unit has polypeptide chain and a haem group. It consists of Fe2+. It can attract and hold an oxygen molecule. It has a high affinity for oxygen.
How do you calculate cardiac output?
How do you calculate heart rate from one heart beat?
Heart rate x stroke volume
60/time for one heart beat
Describe the role of haemoglobin (O2)
In the blood, O2 becomes associated with the haemoglobin. This takes oxygen out of solution and maintains a steep concentration gradient allowing more oxygen to enter the blood from the lungs and diffuse into the cells. Oxyhaemoglobin must release oxygen at tissues that are aerobically respiring (dissociation)
How does partial pressure of oxygen affect oxygen-haemoglobin binding?
As partial pressure of oxygen increases, the affinity of haemoglobin also increases, so oxygen binds to haemoglobin. This causes a conformational change and allows more oxygen molecules to enter the haemoglobin and associate with other haem groups easily. This occurs in the lungs (loading) .When partial pressure is low (respiring tissues), oxygen is released from haemoglobin.
What does the dissociation curve illustrate?
The change in haemoglobin saturation as partial pressure changes. As oxygen pressure rises, the diffusion gradient increases. The affinity increases due to the conformational change and this accounts for the steepness of the curve. The curve levels off.
Why is fetal haemoglobin different?
It has a higher affinity for oxygen therefore the dissocation curve is to the left of the adult curve. Fetal haemoglobin must be able to associate with oxygen where the pO2 is low enough to make adult haemoglobin release oxygen. In the placenta the tension is low - this reduces the O2 tension further. This means the oxygen from the mothers blood diffuses into the placenta. This reduces the oxygen tension within the mother’s blood and makes the maternal haemoglobin release more O2.
Descrbe what ways carbon dioxide is transported
5% is dissolved directly in the plasma
10% is combined directly with haemoglobin to form carbaminohaemoglobin
85% is transported as hydrogencarbonate ions
Describe the Bohr effect
- CO2 enters the RBC forming carbonic acid which dissociates to release hydrogen ions
- these hydrogen ions affect the pH of the cytoplasm making it more acidic
- pH can affect the tertiary structure of haemoglobin and thereby reduces the affinity of the haemoglobin for oxygen
- Hb is unable to hold as much O2 so it is released from the OHb to the tissues
Explain what causes fluctuation in pressure at the aorta
Systole increases pressure
Distole decreases pressure
Describe the pressure changes in the blood as it flows through the circulatory system from aorta to veins
Pressure drops as distance from heart increases
Pressure is constant in the veins
Greatest drop in pressure in the arteries
fluctuation decreases from aorta to arteries
no fluctuation in veins and capillaries
Explain what causes the change in pressure as blood flows from aorta to arteries and from arteries to capillaries
- Blood flows into a larger number of vessels (smaller)
- Cross sectional area in the arteries is greater than the aorta
- Cross sectional area of the capillaries is greater in the capillaries than in the arteries
- cross sectional area is larger
- reduced resistance to blood flow
Describe the roles of the SAN and the AVN
SAN is the pacemaker and initiates the heart beat + sends out wave of excitation over atria walls
AVN delays impulse and sends impulse down the septum
State how hydrostatic pressure is generated in the heart
contraction of ventricle walls
What immediately happens after the atrioventricular valves open?
The pressure in the ventricle is below the atrium
AV valve opens
Blood flows into the atrium and ventricle
Describe how the action of the heart is initiated and coordinated
- SAN initiates wave of excitation
- Wave spreads over atrial wall
- Atrial systole
- Synchronised contraction
- delay at AVN
- wave spreads down septum
- Purkyne fibres
- ventricles contract from apex
Why is there a delay between the excitation of the atria and the excitation of the ventricles?
- allow time for atria to fully contract
- allow time for atria to empty
- so ventricles don’t contract too early
Explain why the excitation wave is carried to the apex
- so ventricular contraction starts at the bottom
- to push blood upwards
- complete efficient emptying of the ventricles
Explain how substances like O2 and glucose enter the tissue fluid from the capillaries
- diffusion
- high concentration to a low conc/conc grad
- hydrostatic pressure in capillary higher than in tissue fluid
- fluid moves from high pressure to low pressure
- as fluid leaves glucose and O2 leave with fluid
Explain why tissue fluid cannot contain erythrocytes
- gaps (fenestrations) between the endothelium cells are too small
- too large
Describe and explain what happens to blood plasma at the artirole end
- plasma fluid moves out of capillary
- forms tissue fluid
- fluid moves down pressure gradient
- hydrostatic pressure greater than WP
- plasma proteins stay in capillaries
Why does the fetus haemoglobin have a higher affinity for oxygen?
So it can take blood from the maternal blood to survive and grow
Why does myoglobin have a higher affinity for oxygen?
Enables muscles to take oxygen from the blood, get extra blood during exercise
