transport in animals exam questions Flashcards
State the meaning of the following terms:
- single circulatory system
- double circulatory system
- open system
- closed system
[4 marks]
Single Circulatory System - blood passes through the heart once for each circulation/cycle of the body
Double Circulatory System - blood passes through the heart twice for one complete circuit
Open System - blood is not always contained in vessels e.g. a heart that pumps blood like fluid called haemolymph through short vessels and into a large cavity called the haemocoel
Closed System - the blood is maintained inside vessels
Explain three reasons why mammals need a circulatory system whilst unicellular organisms do not [4]
SIZE
* Mammals are larger
* Cells deep in body
* But you need to get materials to all parts
* And diffusion would be too slow
ACTIVITY
* Mammals more metabolically active
* Need a rapid supply and removal of waste
SA:V Ration
* Large animals have a smaller surface area:volume ratio
* Diffusion alone would not be effective/would be too slow
List three reasons why a large, multicellular animal, such as a mammal needs a transport system. [3]
- Low/small surface area to volume ration
- Diffusion too slow/distance to great
- To supply enough oxygen/nutrients
- To prevent CO2/waste product building up
- Active
What is the function of the coronary artery [1 mark]
- Supply oxygen/nutrients to the heart muscle for aerobic respiration
- Remove carbon dioxide/waste
Explain why the wall of the left ventricle is thicker than the wall of the left atrium [4 marks]
- Need more muscle - to create more force
- To create higher pressure
- As has to pump blood against greater resistance/friction
- Also left ventricle pumps blood further - to all parts of the body (systemic circulation)
Explain why it is important that the two sides of the heart are completely separated [2 marks]
- Stops oxygenated and deoxygenated blood mixing
- Ensures oxygenated blood gets to the body while deoxygenated blood to lungs
- It also allows different pressures to be maintained on each side
- There would be a possible drop in blood pressure if there was a hole present
Explain the advantage of the ventricles contracting from the bottom upwards [1 mark]
- Allows the ventricles to empty completely
- This is because aorta and pulmonary artery are found at the top
Explain how pressure changes in the heart bring about the closure of the atrioventricular (bicuspid) valve [3]
- Ventricular systole (contraction of ventricle wall)
- Raises ventricular pressure
- When the pressure in ventricle is higher than atrial pressure
- It pushes valve shut
- Chordae tendinae prevents inversion
Describe how the action of the heart is initiated and coordinated [5]
- SAN initiates excitation
- Wave of excitation spreads over atrial wall/muscle
- This results in atrial systole (contraction of atria)
- In synchronization
- A short delay occurs at AVN
- Band of non-conducting collagen prevents excitation carrying straight on
- and then excitation spreads down septum
- through bundle of His and Purkyne fibres
- This results in the ventricles contracting from apex/bottom upwards
What is the advantage of the slow rate of conduction through the AVN [2 marks]
- Delays contraction of ventricles
- Until of the atria have contracted completely filling the ventricles
Suggest one advantage of the high rate of conduction in the Purkyne fibres which carries impulses through the walls of the ventricles [1 mark]
Causes the rapid contraction of ventricles together
How would cutting the nerve connections from the brain to the SAN affect the heart? [1 mark]
- It wouldn’t as the Heart is myogenic
- SAN initiates beat
- SAN generates impulses that cause contraction.
Describe how an artificial pacemaker regulated heart activity [2 marks]
- Supplies electrical impulses to the heart
- Replaces action of damages conducting tissue
- Provides regular electrical impulses
Describe the role of the Atrioventricular node in the production of the heart beat [1 mark]
- Produces electrical impulses in response to electrical activity from the SAN
- Causes a time-delay
- Passes on electrical activity from the SAN to the bundle of His
Describe the role of the Bundle of His [1 mark]
Carries electrical impulses from AVN to purkyne fibres extremely quickly
Describe the role of the purkyne fibres [1 mark]
This cause contraction of ventricles from the base simultaneously
The beating of the heart is myogenic
Explain what this means [2 marks]
- SAN/sinoatrial node (starts each beat)
- Beats initiated by the heart
- Doesn’t need stimulation by nerve/nerve impulses to contract/beat
During the electrical stimulation of the heart, there is a short delay between the excitation of the atria and excitation of the ventricles. Explain why the delay is essential. [2]
- To allow time for the atria to fully contract
- To allow time for atria to empty/ventricles to fill
- So that ventricles do not contact too early
The Purkyne tissue carries the excitation wave down the excitation wave down the septum to the apex of the heart. Explain why the excitation wave is carried to the apex. [2
- So that ventricular contraction starts at apex/base
- To push blood upwards - towards arteries
- Complete/efficient emptying of ventricles.
Describe how the structure of an artery is related to its function [6]
1) The artery has a narrow lumen
- to help maintain pressure
2) The artery has a generally thick wall
- to prevent bursting and withstand pressure
3) The wall is made up of three layers tunica intima, tunica media and tunica externa
Tunica Intima
* This is a smooth endothelium
* Made up of squamous epithelium
* Smoothness helps reduce friction
Tunica Media
* Elastic fibres- allows stretching to help prevent bursting and withstand and maintain pressure
* Collagen fibres - provide strength
* Smooth muscle - help maintain pressure (vasoconstriction)
Tunica Externa
* Mainly collagen fibres
* Some elastic fibres
Describe how the structure of a vein is related to its function [6 marks]
1) The artery has a relatively large lumen - helps accommodate large volumes of blood
2) Veins have valves - help prevent back flow and allow blood to move towards heart
3) The wall is made up of three layers tunica intima, tunica media and tunica externa
Tunica Intima
* This is a smooth endothelium
* Made up of squamous epithelium
* Smoothness helps reduce friction
Tunica Media
* Thin but does have muscle and elastic tissue (less than artery)
* As only needs to withstand low pressure
* Also allows skeletal muscle to squeeze veins
Tunica Externa
* Mainly collagen fibres (less than artery) - provides strength
State ways in which the wall of an artery is different from the wall of a vein [2 marks]
- Arteries have no valves
- Arteries have thick layer of smooth muscle and elastic tissue (tunica media)
- Arteries have more collagen (tunica externa)
Blood in arteries has a high hydrostatic pressure. State how this hydrostatic pressure in the heart is generated [1 mark]
Contraction of ventricle wall (ventricular systole)
Explain why the hydrostatic pressure of the blood drops as blood moves away from the heart [2 marks]
1) Arteries stretch and expand
2) There is more vessels
3) There is loss of fluid/plasma from capillaries
Explain how the structure of capillaries enables them to carry out metabolic exchange efficiently [5 marks]
- Thin wall (one cell thick) - creates a short pathway for easy diffusion
- Smooth endothelium - creates reduced friction/resistance and smooth flow
- Small gaps - allows nutrients out
- Narrow diameter - only one red blood cell can flow at a time (reduced rate of flow). This slows blood flow so substances can diffuse in and out
Describe and explain how the wall of an artery is adapted to both withstand and maintain high hydrostatic pressure [5 marks]
To withstand pressure:
* Wall is thick
* Thicker layer of collagen
* This provides strength
* Elastic fibers - allow it stretch to accommodate pressure
To maintain pressure:
* Elastic tissue
* To cause recoil and return to original size
* Thick layer of smooth muscle
* This constricts lumen/artery
Explain why it is important that the pressure changes as blood flows from the aorta to the capillaries [2 marks]
- Capillary is thin/only one cell thick
- High pressure would burst damage capillary
- This could result in odema
Describe how red blood cells are adapted to their function [8 marks]
- Contains Haemoglobin - to carry oxygen
- Flexible/elastic/stretchy/change shape - this allows red blood cells to fit/squeeze into capillaries
- Biconcave - gives increased surface are relative to its volume (for diffusion). Also means haemoglobin never far from cell surface
- No nucleus - to maximise room hemoglobin
- Lack of organelles (e.g. endoplasmic reticulum) increased room for Hb
- Small (about 7µm in diameter) - about the same size as a capillary
Explain two advantages of keeping blood inside vessels [2 marks]
- Maintain higher blood pressure
- Increase rate of flow
- Flow can be diverted (e.g vasoconstriction)
Describe and explain how substances that are dissolved in the blood plasma, such as oxygen or glucose enter the tissue fluid from the capillaries [3 marks]
- Diffusion
- From high concentration to a low concentration
- Pressure in the capillary high
- Capillary wall leaky
- Fluid forced out of capillary - down a pressure gradient
- As the fluid moves out glucose and oxygen leave with the plasma
How does the composition of tissue fluid differ to blood plasma? [4 marks]
- Does not contain red blood cells (erythrocytes) - they are too large
- Does not contain plasma proteins - they are too large
- Does contain white-blood cells
- Does contain oxygen, glucose and mineral ions
What is oedema? [1 mark]
build up of tissue fluid causing a swelling in the tissues
Suggest what could happen in tissues if a persons drainage of tissue fluid was inefficient [2 marks]
- Fluid collects in tissues
- This will result in tissue swelling
- This is called oedema
- Especially dangerous in lungs (pulmonary oedema)
Explain why tissue fluid does not contain erythrocytes [2 marks]
- Gaps between endothelial cells are too small
- Erythrocytes too large/cannot change shape
- to fit through gaps/fenestrations
Describe the role of haemoglobin in transporting oxygen around the body [3 marks]
- has a high affinity for oxygen
- oxygen binds to haemoglobin in lungs
- forms oxyhaemoglobin
- oxygen released in tissues where needed (where respiration is occurring)
Describe how the production of carbon dioxide during respiration leads to a higher concentration of hydrogen ions in the blood. [3 marks]
- Carbon dioxide reacts with water
- To give carbonic acid
- Carbonic acid acts as a catalyst
- Carbonic acid then dissociates releasing H+ and HCO3- ions
Describe how haemoglobin acts to reduce the concentration of hydrogen ions in the blood [4 marks]
Hydrogen ions combine with haemoglobin
Forms haemoglobinic acid
The blood contains hydrogen carbonate ion (HCO3 - ) Describe how these ions are formed in the blood [3 marks]
- Carbon dioxide diffuses into red blood cells
- Carbon dioxide reacts with water
- To form carbonic acid
- Catalysed by Carbonic anhydrase
- Carbon acid then dissociates to give H+ and HCO3
Outline the benefits of the Bohr shift to actively respiring tissue [3 marks]
- Actively respiring tissue needs/requires more oxygen
- For aerobic respiration - to release more energy
- More CO2
- Causes more oxygen to be released
- As less haemoglobin available to combine with oxygen
Explain why the curve for fetal oxyhaemoglobin is to the left of the curve for adult oxyhaemoglobin [3 marks]
- Placenta has low pO2
- Adult haemoglobin will release O2/dissociate in placenta
- Fetal haemoglobin has higher affinity for oxygen
- Fetal haemoglobin is still able to take up some oxygen in the placenta
Explain why it is essential that the fetus has a different type of haemoglobin from the adult [4 marks]
- To allow fetus to gain oxygen from maternal blood
- Across placenta
- Partial pressure of oxygen is similar in the fetal and maternal parts of the placenta
- Fetal haemoglobin has a higher affinity for oxygen
- Oxygen is required for aerobic respiration
Explain why the change from fetal to adult hameoglobin seen in the diagram above is essential after birth [2 marks]
- Affinity of fetal haemoglobin would be too high
- Would not release oxygen readily enough
- Adult females will need difference with their fetuses in due course.
Describe what would be likely to happen to people who move to a high altitude if their red blood cells did not increase [4 marks]
- Haemoglobin becomes less saturated with oxygen
- Altitude sickness
- Results in hypoxia (shortage of oxygen to tissues)
- Dizzinenss/weakness
- Eventually result in death/coma
Explain why a large multicellular organism like a tree needs a water transport system whilst Chlamydomonas does not.
distance in tree is greater;
not all tissues / cells in contact with water
diffusion too slow
Chlamydomonas has large surface area:volume
Why is the left ventricle thicker than right ventricle and atria?
provides more pressure/force to pump blood around body;
Overcome the resistance of systemic circulation
longer distance compared with distance right ventricle/atrium
Why do larger organisms require transport system?
larger organism= smaller SA:V
distance is too great
diffusion is too slow
Insufficient rate of exchange of oxygen/co2
more metabolically active
What causes the rise and fall in pressure in the arteries?
cardiac muscle cause ventricles to contract/relax
peaks coincides, with, systole (contraction)
troughs coincide, with, diastole (relaxation)
stretch-recoil effect
Why is the pressure much lower by the time it enters capillaries?
Capillaries are further away from the heart
Less stretch and recoil effect
There is more resistance to flow
Total volume of capillaries is much greater
Why is it important to have low pressure by the time it reaches capillaries?
only one cell thick
lack of elasticity
high pressure damages its walls
slower flow rate gives sufficient time for exchange to occur
Explain how the blood in veins is returned to the heart
valves prevent backflow
Contraction of surrounding muscles helps transport blood
*large lumen = little resistance
gravity effect
*negative pressure in chest
Purkyne tissue function
They branch down and across the walls of ventricles
conduct waves of excitation
so contracts from apex upwards
*Both ventricles contract together
What happens when there’s lack of oxygen to the brain?
Less oxygen reach brain
Reduced aerobic respiration
Undergoes anaerobic respiration
lactic acid builds up -> migraines
Why must the fetal Hb be different from adult Hb?
Fetal Hb has higher affinity for oxygen
Able to obtain some oxygen from placenta where the partial pressure is lower
Maternal Hb releases oxygen in placenta
maintain diffusion gradient
Why must the fetal Hb change to adult Hb when born?
oxygen would not be released readily enough
affinity of fetal haemoglobin would be too high;
adult (females) will need difference with
their fetuses in due course;
Impact of fibrillation
contractions are not coordinated
less blood, leaves heart / goes to lungs / goes to body;
cells / heart muscle deprived of oxygen;
Chambers not full so blood pumped at low pressure
Why is it important that the steepest part of oxygen dissociation curve is between 2-5kpa?
2-5 kpa at muscle tissues which require lots of oxygen
*a drop in Po2 gives large drop in saturation
So release lots of oxygen for respiration
How does exercising muscle tissue bring changes in the dissociation curve?
More respiration = more energy released as heat
Body temperature rises
(Curve shifts to right)
More o2 released from Hb
Describe how the structure of an artery relates to its function
Narrow lumen = maintains high pressure
Thick wall= stop bursting/ withstand
Collagen layer = provides strength and prevents it from bursting
elastic tissue= stretch and recoil to even the surges of pressure
smooth endothelium = reduce friction
Suggest why the system shown for the frog ( partial circulation) may be less effective at supplying the body tissues with oxygen
Mix of deoxygenated and oxygenated blood
not fully oxygenated
still carrying carbon dioxide
lower pressure
Features of capillaries and its role in exchange
Thin wall= short diffusion pathway
Smooth endothelium=reduced friction
Pores=Allows nutrients to pass through
Narrow diameter= RBCs squeeze through so short diffusion distance
Total SA is large= more exchange
Differences between tissue fluid and blood
TISSUE FLUID
no RBCs (don’t say Hb)
no plasma proteins
no platelets
fewer WBCs
not in vessels
What happens if the drainage into lymphatic system was insufficient?
Tissue fluid builds up in tissues -> swells
Oedema
What is partial pressure?
Concentration of oxygen in atmosphere
(Proportion of atmospheric pressure produced by oxygen)
Describe what would be likely to happen to people who move to high altitude if their red blood cell counts did not increase.
haemoglobin is less saturated with oxygen
altitude sickness;
hypoxia
dizziness / headaches
brain damage / lung damage / oedema in these
organs
What is a vascular system
system of transport vessels in animals and plants
Why is the delay at AVN important?
-allow time for atria to fully contract
-allow time for atria to empty/ ventricles to fill
-so that ventricles dont contract too early
How is the wall of artery adapted to MAINTAIN pressure?
-Elastic fibre
-stretch and recoil
-thick smooth muscle cause narrow lumen
How is the wall of artery adapted to WITHSTAND pressure?
-thick layer of collagen
-provides strength
-folded endothelium
-no damage to endothelium as wall can stretch
Advantages of keeping blood in vessels
-maintains high pressure
-increases flow rate
-blood can be diverted
Describe how the action of the heart is initiated and coordinated
-SAN initiates a wave of excitation
-which spreads over the atrial walls
-atrial systole
-contraction is synchronised
-delay at AVN
-excitation spreads down the septum
-purkyne fibres
-ventricles contract from apex
Why does the hydrostatic pressure of blood drop further away from heart?
More vessels
larger total cross sectional area
reduced resistance to flow
loss of fluid from capillaries
Double circulation advantages
1) more efficient supply of oxygen to tissues
2) helps to sustain high pressure
3) less resistance to flow
4) easier to return to heart
5) more rapid circulation
