Transport in animals Flashcards
1
Q
What is the need for specialised transport system?
A
- The metabolic demands of most multicellular animals are high (they needs lots of oxyegn and food, they produce lots of waste products) so diffusion over the long distances is not enough to supply the quantities needed
- The surface area to volume (SA:V) ratio gets smaller as multicellular organisms get bigger so the diffusion distances get bigger and for every unit mass or volume, there is less surface area available for exchange (to absorb or remove substances)
- Size of an organism => if cells in centre of organism are far from surface, diffusion rate to all cells is slow. Outer cells use up oxygen for metabolism meaning less is availble for the cells at the centre
- Molecules (e.g. hormones or enzymes) may be made in one place but needed in another
- Food will be digested in one organ system, but needs to be transported to every cell for use in respiration and other aspects of cell metabolism
- Waste prodyces of metabolism need to be removed from the cells and transported to excretory organs
2
Q
What is mass flow?
A
Movement of a fluid in bulk in one direction due to a hydrostatic pressure gradient
3
Q
What is hydrostatic pressure
A
The pressure that a fluid in a confined space (e.g. blood) exerts against the vessel walls
4
Q
What are the different types of circulatory systems?
A
- Open circulatory system
- Closed circulatory system (double or single)
5
Q
Where are open circulatory systems found?
A
Mainly in invertebrate animals, including most insects and some molluscs
6
Q
How does an open circulatory system work?
A
- There are no vessels to contain the transport medium, haemolymph
- Instead the blood is pumped straight from the heart into the body cavity, called the haemocoel
- In the haemocoel the haemolymph is being pumped at low pressure and circulation is slow
- The haemolymph comes into direct contact with the tissues, organs and cells of the insect
- This is where exchange takes place between the haemolymph and the cells
- The haemolymph returns to to the heart through an open-ended vessel
- The haemolymph circulates but steep diffusion gradients cannot be maintained for efficient diffusion
- There flow of haemolymph to a particular tissue cannot be controlled to meet changing demands
7
Q
What is the blood of insects called? And what does it transport?
A
- Haemolymph
- It transports food and nitrogenous waste products and the cells involved in defecne against disease (not carbon dioxide or oxygen)
8
Q
Describe the structure of an open circulartory system?
A
The body cavity is split by a membrane the heart extends along the length of the thorax and the abdomen of the insect
9
Q
How does a closed circulatory system work?
A
- Blood is enclosed in blood vessels and does not come directly into contact with the cells of the body
- The heart pumps blood at high pressure and rapidly
- Substances are exchanged between blood and cells/tissues/organs by diffusion through the walls of capillaries
- The amount of blood flowing to a particular tissue can be adjusted by widening or narrowing blood vessels
10
Q
In what animals are single closed circulatory systems found?
A
Fish and annelid worms
11
Q
How does a single closed circulatory system work?
A
- Blood passes through the heart once in each circulation
- Blood passes through two sets of capillaries before it returns to the heart
- In the first, it exchanges oxygen and carbon dioxide
- In the second set of capillaries, in the different organ system, substances are exchanged between the blood and the cells
- Passing through two sets of capillaries causes the blood pressure system to drop so the blood returns to the heart quite slowly
- This limits the efficiency of the exchange processes so the activity levels of animals with single closed circulations tends to be relatively low
12
Q
How are fishes an exception to single closed circulations being slow?
A
- They have a relatively efficient single circulatory system, which means they can be very active
- They have a countercurrent gaseous exchange mechaninsm in their gills that allows them to take a lot of oxygen from the water
- Their body weight is supported by the water in which they live and they do no maintain their own body temperature
- This greatly reduces the metabolic demands on their bodies and, combined with their efficient gasours exchange, explains how fish can be so active with a single closed circulatory system
13
Q
How does a single closed circulatory system work in a fish?
A
- The heart pumps deoxygenated blood to the gills where gases are exchanged
- Oxygenated blood leavse the gills and is transported directly to the rest of the body
- Deoxygenated blood returns to the heart
14
Q
In what animals are double closed circulatory systems found?
A
Birds and most mammals
15
Q
How does a double closed circulatory system work?
A
It involves two separate circulations:
- Deoxygenated blood is pumped from the heart to the lungs to pick up oxygen and unload carbon dioxide, and then returns to the heart
- Oxygenated blood flows through the heart and is pumped out to travel all around the body before returning to the heart again
16
Q
What is the definition of a double circulation?
A
Contains two separate circuits/sets of capillaries (pulmonary and systemic) and blood passes through the heart twice
17
Q
What are the advanatges of a double circulatory system over a single circulatory system?
A
- Sustains higher pressure over both exchange surfaces/capillaries (lungs and tissues)
- Pressure can be differentiated. Left side of the heart pumps at much higher pressure thn right. Blood pressure to pulmonary arteries is less than the pressure to systemic arteries
- Speed of flow => Double circulatory allows for more rapid flow to both sets of capillaries. This is important for endotherms (mammals and birds) as they have a high metabolic rate to maintain their temperature constantly high.
Single circulatory system: blood slowed by capillaries in gills. This is sufficient for ectotherms (eg fish) that
do not need to maintain their temperature constantly high.
18
Q
What are blood vessels composed of? And what are their function?
A
- Elastic fibres => these are composed of elastin and can stretch and recoil, providing vessel walls with flexibility
- Smooth muscle => contracts or relaxes which changes the size of the lumen
- Collagen => provides structural support to maintain the shape and volume of the vessel
19
Q
What is the diameter of the lumen of capillaries?
A
10µm
20
Q
How are the arteries adapted to their function?
A
- Wall is thick to withstand high pressure
- The lining of the artey (endothelium) is smooth so the blood flows easily over it
- Lumen is small to maintain high pressure
- Inner wall is folded to allow the lumen to expand as blood flow increases
21
Q
How are arterioles adapted to their function?
A
- They have more smooth muscle and less elastin in their walls than arteries, as they have little pulse surge
- Contraction of the smooth muscle will constrict the diameter of the arteriole which increases the resistence to flow and reduces the rate of blood flow
- They can constrict or dilate to control the flow of blood to regions of the body that are demanding more oxygen
22
Q
How are capillaries adapted to their role?
A
- They provide a very large surface area for the diffusion of substances into and out of the blood
- The walls are leaky. They allow blood plasma and disolved substance to leave the blood
- The total cross sectional area of the capillaries is always greater than the artierole supplying them so the rate of blood flow falls
- The relatively slow movement of blood though capillaries gives more time for the exchange of materials by diffusion between the blood and the cells
- The walls are a single endothelial cell thick, giving a very thing layer for diffusion
23
Q
What is the difference between elastic and muscular arteries?
A
- Elastic arteries are found near the heart and have more elastic tissue in the wall, in order to allow stretch and recoil (to their original length)
- This helps to even out flucutations in blood pressure created by the heart
- The elastic fibres enable them to withstand the force of the blood pumped out of the heart and stretch (within limits maintained by collagen) to take the larger blood volume
- Muscular arteries are found further from the heart and the walls contain more muscle tissue
24
Q
How are veins adapted to their function?
A
- The lumen is relatively large, in order to ease the flow of blood
- The walls have thinner layers of collagen, smooth muscle and elastic tissue than in artery walls. They do not need to stretch and recoil, and are not actively constricted in order to reduce blood flow
25
How are veins adapted to reducing backflow?
- The majority of the veins have one-way semilunar valves at intervals. When blood flows in the direction of the heart, the valves open so the blood can pass through. If the blood starts to flow backwards, the semilunar valves close to prevent this from happening
- Many of the bigger veins run between the big, active muscle in the body e.g arms and legs. When the muscles contract they squeeeze the veins, forcing the blood towards the heart. The valves prevent backflow when the muscles relax
- The breathing movements of the chest act as a pump. The pressure changes and the squeezing actions move blood in the veins of the chest and abdomen towards the heart
26
What is the function of the left ventricle?
Delivers oxygenated blood from the left side of the heart to the body via the aorta
27
What is the function of the right ventricle?
Delivers deoxygenated blood from the right side of the heart to the lungs via the pulmonary artery
28
What is the function of the left atrium?
Receives oxygenated blood from the lungs via the pulmonary vein
29
What is the function of the right atrium?
Receives deoxygenated blood from the body via the vena cava
30
What is the function of the aorta?
Takes oxygenated blood from the left ventricle to the body
31
What is the function of the pulmonary artery?
Takes deoxygenated blood from the right ventricle to the lungs
32
What is the function of the superior vena cava?
Delivers deoxygenated blood from the head and neck to the right atrium
33
What is the function of the inferior vena cava?
Delivers deoxygenated blood from the trunk and limbs to the right atrium
34
What is the function of the pulmonary vein?
Delivers oxygenated blood from the lungs to the left atrium
35
What is the function of the tricuspid valve?
Prevents backflow of blood from the right ventricle to right atrium during ventricular systole (contraction)
36
What is the function of the bicuspid valve?
Prevents backflow of blood from the left ventricle to left atrium during ventricular systole (contraction)
37
What is the function of the semilunar valve?
Prevents backflow of blood from aorta and pulmonary artery to ventricles during ventricular diastole (relaxation) due to the force of gravity
38
What is the function of the chordae tendinae?
Prevents atrioventricular valves from inverting during ventricular systole
39
What is the function of the papillary muscles?
Attach the chordae tendinae to the wall of the ventricles
40
What is the route of blood (starting from vena cava and ending at vena cava)?
Vena cava => right atrium => tricuspid valve => right ventricle => semilunar valve => pulmonary artery => lungs => pulmonary vein => left atrium => bicuspid valve => left ventricle => semilunar valve => aorta => body => vena cava
41
What is function of the coronary artery?
Supplies the heart (cardiac) muscle with oxygenated blood
42
What may occur of the coronary arteries becomes constricted?
- Reduces delivery of oxygen and nutrients e.g. fatty acids and glucose
- This could cause angina or a heart attack
43
What is the function of the septum?
- Allows you to have double circulatory system
- Separates two halves of the heart at the ventricle
- It ensures that the oxygenated blood in the left side of the heart and the deoxygenated blood in the right side are kept separate
44
Why are the walls of the left ventricle thicker than the walls of the right ventricle?
- The blood from the left ventricle is pumped out through the aorta and needs sufficient pressure to overcome the resistance of systemic circulation
- While the right ventricle only needds to overcome the resistance of the pulmonary circulation (because the lungs and heart are close together)
45
What is the cardiac cycle?
- The sequence of a events in one full heart beat which pumps blood around the body
- The events of the left and right side of the heart occur simultaneously
46
What is the average time taken for each cardiac cycle? And what is the averge bpm?
- 0.8s
- 75 bpm
47
What are the stages of the cardiac cycle?
- Atrial systole
- Ventricular systole
- (ventricular) Diastole
48
What occurs during atrial systole?
- Both left and right atria contract together => atrial systole
- The muscle in the walls is thin so only a small increase in pressure is created by the contraction
- Ventricles are relaxed => ventricular diastole
- This helps to push blood from the atria into the ventricles stretching their walls and ensuring they are full of blood
- The atrioventricular valves are pushed open by the blood in the atria
- Semilunar valves are closed
- P(at) > P(v)
- P(ao) > P(v)
49
What occurs during ventricular systole?
- Both left and right ventricles pump together
- Contraction of ventricles starts at the apex of the heart so blood is pushed upwards and towards the arteries => ventricular systole
- Atrioventricular (bicuspid & tricuspid) valves close due to rising pressure in the ventricles (this closure creates the 1st heart sound => 'lub')
- Semilunar valves are pushed open by blood from ventricles and is under high pressure
- Blood flows from left ventricle to aorta
- Blood flows from right ventricle to the pulmonary artery
- P(at) < P(v)
- P(ao/pa) < P(v)
50
What occurs during ventricular diastole?
- The muscular walls of all four chambers relax => atrial and ventricular diastole
- Elastic recoil causes the chambers to increase in volume allowing blood to flow in the veins
- The increased volume of blood and elastic recoil in the vessel walls of the aorta and the pulmonary artery cause an increase in pressure which closes the semilunar valves (this closure creates the 2nd heart sound => 'dub')
- As the ventricles relax, their pressure goes below the pressure in the atria
- Atrioventricular valves open
- Blood flows from atria into the ventricles due to gravity and relaxed state of ventricles
- The cycle repeats itself
- Pat > Pv
- Pao > Pv
51
How do you calculate cardiac output? And what are the unit?
cardiac output = stroke volume x heart rate
units: dm3/min
52
What is an ECG? And what does it stand for?
- ECG is a trace that records the electrical activity of the heart
- Stands for electrocardiogram
53
What is the conduction system?
Specialised tissue that intiates and coordinates the contraction of heart/cardiac muscle
54
What is meant by the cardiac muscle being myogenic?
- It has its own intrinsic rhythm at around 60 beats per minute (60bpm)
- Its rhythmic contractions arise from within the cardiac muscle tissue itself
- It doesn't require neural stimulation to contract
55
What is the average resting heart rate of an adult?
around 70bpm
56
What specialised tissue make up the conduction system?
- SAN (sinoatrial node)
- AVN (atrioventricular node)
- Bundle of His
- Purkyne fibres
57
Describe how the conduction system controls the cardiac cycle.
- Contraction starts at the sinoatrial node (SA node)
- The SA node is often referred to as the pacemaker
- A wave of electrical excitation begins, spreading over the walls of the atria, causing the atria to contract and intiating the heartbeat
- A layer/septum of non conducting tissue (found at the base of the atria) prevents the excitation passing directly to the ventricles
- The electrical activity from the SAN is picked up by the atrioventricular node (AVN)
- The wave of excitation is delayed in the AVN before stimulating the bundle of His
- After the short delay, the wave of exitation is carried away from the AVN
- The bundle of His splits into two branches of Purkyne fibres and conducts the wave of excitation to the apex of the heart
- The purkyne fibres runs doewn the interventriculae septum and spreads out through the walls of the ventricles on both sides
- The spread of excitation spreads out over the walls of the ventricles, starting from the apex
- This triggers the contraction of the ventricles
- Contraction starting at the apex allows more efficeint emptying of the ventricles
- This pushes the blood up towards the aorta and pulmonary artery at the top of the heart
58
Where is the SAN found?
Embedded in the wall of the right atrium close to the entry of the superior vena cava
59
Where is the AVN found?
At the top of the interventricular septum (the septum separating the two ventricles)
60
Why is the excitation in the AVN delayed?
This allows time for the atria to finish contracting and for the blood to flow down into the ventricles before they begin to contract
61
List out the movement of wave of excitation?
SA node -> atrium contract -> AV node -> bundle of His -> purkyne fibres -> ventricles contract -> period of relaxation
62
What is the bundle of His?
A bundle of conducting tissue made up of Purkyne fibres which penetrate through the septum between the ventricles
63
What is are the purkyne fibres?
Consists of specially adapted muscle fibres that conduct the wave of excitation from the AVN down the septum to the ventricles
64
How does an ECG work?
- It doesn't directly measure the electrical activity of your heart
- It measure tiny electrical differences in your skin, which result from the electrical activity of the heart
- This involves attaching a number of sensors to the skin
- The sensors on the skin pick up the electrical excitation created by the heart and convert this into a trace
65
Identify this trace (1)
Answer one revision card
66
Identify this trace (2)
Answer one revision card
67
Identify this trace (3)
Answer one revision card
68
Identify this trace (4)
Answer one revision card
69
Identify this trace (5)
Answer one revision card
70
What is tachychardia?
- When the heartbeat is very rapid, over 100bpm
- This is often normal, for instance when you exercise, if you have a fever, if you are frightened or angry
- If it is abnormal it may be caused by problems in the electrical control of the heart and may need to be treated by medication or by surgery
71
What is bradychardia?
- When the heart rate slows down to below 60bpm
- Many people have bradychardia because they are fit - training makes the heart beat more slowly and efficiently
- Severe bradycardia can be serious and may need an artificial pacemaker to keep the heart beating steadily
72
What is an ectopic heartbeat?
- Extra heartbeats that are out of 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 very frequent
73
What is atrial fribrilitation?
- This is any example of arrhythmia, which means an abnormal rhythm of the heart
- Rapid electrical impulses are generated in the atria
- They contract very fast (fribrilate) up to 400 times a minutes
- However, they do not contract properly and only some of the impulses are passed on to the ventricles, which contract much less often
- As a result the heart does not pump blood very effectively
74
Draw the trace of a healthy person. And label the waves.
Answer one revision card
75
What does the P wave represent on an ECG trace?
- Atrial systole
- Shows excitation of atria/atrial stimulation
76
What does the horizontal line between P and Q represent on an ECG trace?
- Delay at the AV node
77
What does the QRS complex represent on an ECG trace?
- Ventricular systole
- Shows excitation of ventricles/ventricular stimulation
78
What does the T wave represent on an ECG trace?
- Shows diastole
- Ventricles repolarising
79
What is hydrostatic pressure?
- The pressure that a fluid (e.g. blood) exerts when pushing against the walls of a vessel/container
- It is generated by the contraction of cardiac muscle in the heart
- Measured in kPa
80
What is filtration?
The movement of a fluid and its dissolved substances, through pores in capillary wall, due to the hydrostatic pressure generated by the heart
81
What is oncotic pressure?
- The tendency of water to move into the blood by osmosis as a result of the plasma proteins
- Measured in kPa
- It is about -3.3.kPa
82
Describe the process of exchange at the capillaries.
- At the arterial end, blood is under high hydrostatic pressure (at about 4.6kPa)
- It is higher than the oncotic pressure (-3.3kPa) so this results in the net movement of fluid from blood out of the tiny gaps in the capillary wall and fills the space between cells and is called tissue fluid
- The fluid that leaves the blood consists of plasma with dissolved nutrients and oxygen
- The red blood cells, platelets, plasma proteins and most of the white blood cells remain as they are too large to be pushed through gaps in capillary wall
- Exchange of substances by diffusion occurs between tissue fluid and body cells
- At the venous end, hydrostatic pressure falls (to about 2.3 kPa) as the volume of plasma have been reduced
- The oncotic pressure (-3.3 kPa) is now stronger than the hydrostatic pressure so water moves back into the capillaries by osmosis carrying watse substance e.g. carbon dioxide
- By the time blood returns to the veins, 90% of the tissue fluid is back in the blood vessels
83
What is the lymph?
The fluid held in the lymphatic system, which is a system of tubes that returns excess tissue fluid to the blood system
84
What is the lymphatic system?
A network of vessels, nodes and ducts that collect excess fluid from the blood, is part of the immune system and plays a role in absorbing fats from the intestines
85
How is the lymph formed?
- Formed from excess tissue fluid not reabsorbed into the blood capillaries
- Some tissue fluid is directed into another tubular system called the lymph system or lymphatic system
- This drains excess tissue fluid out of the tissues and returns it to the blood system in the subclavian vein in the chest
86
What is the lymph composed of?
- It is similar in composition to tissue fluid but has less oxygen and fewer nutrients
- It also contains fatty acids which have been absorbed into the lymph from the villi of the small intestine
- It also contains more lymphocytes
87
What is a lymph node?
Swellings found at intervals along the lymphatic system, which have an important part to play in the immune response
88
What is the function of the lymph node?
Intercept bacteria and other debris from the lymph, which are ingested by phagocytes found in the nodes
89
Where are major lymph nodes found?
- Neck
- Armpits
- Stomach
- Groin
90
What is the role of the lymph?
- To drain excess fluid from tissues
- To take cell debris and large particles/phagocytosed bacteria
- To store lymphocytes in lymph nodes for defence
- Lacteals of small intestine take up fatty products of digestion
91
How many molecules of oxygen can be carried by one molecule of Hb?
4
92
What is the equation for deoxyhaemoglobin becoming oxyhaemoglobin?
Hb + 4O2 ⇌ HbO8
deoxyhaemoglobin + oxygen ⇌ oxyhaemoglobin
93
What occurs during haemoglobin association?
- In the lungs (high oxygen levels, high partial pressure of oxygen – pO₂), haemoglobin associates (binds) with oxygen
- The haemoglobin becomes saturated at very high pO₂, as all the haem groups become bound
- Each haemoglobin molecule has four haem (Fe²⁺) groups, which can each bind to an oxygen molecule (O₂)
- As one oxygen molecule binds to a haem group, the molecule changes shape, making it easier for the next oxygen molecules to bind rapidly – this is called positive cooperative binding
- This happens in the alveoli, where oxygen diffuses into red blood cells and binds to haemoglobin to form oxyhaemoglobin (HbO₈)
- This is called loading tension
- This occurs because at a high pO₂ Hb has a high affinity for oxygen
Equation:
Hb + 4O2 ⇌ HbO8
94
What occurs during haemoglobin disassociation?
- In respiring tissues (low pO₂, high CO₂, lower pH), oxygen is released (dissociated) from oxyhaemoglobin
- At low pO₂, few haem groups are bound to oxygen, so haemoglobin does not carry much oxygen
- Cells need oxygen for aerobic respiration, so oxyhaemoglobin dissociates, releasing O₂ to the tissues
- Once the first oxygen molecule is released by the haemoglobin, the molecule changes shape and it becomes easier to remove the remaining oxygen molecules
- This occurs because at a low pO₂ Hb has a low affinity for oxygen
- This is called unloading tension
- The presence of carbon dioxide (CO₂) lowers the pH, causing haemoglobin to change shape and release oxygen more easily—this is known as the Bohr effect
95
What are the three different ways in which carbon dioxide is transported from tissues to lungs?
- 5% is dissolved in the plasma
- 10% is combined with haemoglobin to form a compound called carbaminohaemoglobin
- 85% is transported as hydrogencarbonate ions in the plasma
96
Describe the chloride shift at the tissues.
- The hydrogen carbonate ion diffuses out of the RBCs
- This maintains the reaction to the right
- As it is negatively charged, it is exchanged for chloride ions which enter the RBC to balance the charge
- This is called the chloride shift
- Carbonic anhydrase catalyses the reversible reaction between carbon dioxide and water to form carbonic acid
- The carbonic acid then dissociates to form hydrogen carbonate ions and hydrogen ions
CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-
97
Describe the chloride shift at the lungs.
- Hydrogen carbonate ions re-enter the RBCs (and chloride ions leave to balance the charge
- HCO3- are reconverted to CO2 by the action of carbonic anyhydrase
- Carbon dioxide diffuses out and enters the alveoli, maintaining the reaction to the left so CO2 is continually made
- Carbonic anyhydrase catalyses the breakdown of carbonic acid to carbon dioxide and water
H+ + HCO3- ⇌ H2CO3 ⇌ CO2 + H2O
98
What is the bohr effect?
- The effect of carbon dioxide concentration on the uptake and release of oxygen by haemoglobin
- For example, at a high partial pressure of carbon dioxide, haemoglobin gives up more oxygen
99
How does the bohr effect work?
- The protons are buffered by haemoglobin to prevent a change in the pH of the RBCs. This forms haemoglobinic acid
- The binding of the protons to the haemoglobin has an allosteric effect which changes the shape of the molecule
- Its affinity for oxygen is lowered so that oxygen is able to dissociate more easily at the tissues
- The greater the rate of aerobic respiration of cells, the more carbon dioxide produced by the tissues, the more oxygen dissociates and is delivered to the cells
100
Why is the bohr effect important in the body?
- In active tissues with a high partial pressure of carbon dioxide, haemoglobin gives up its oxygen more readily
- In the lungs where the proportion of carbon dioxide in the air is relatively low, oxygen binds to the haemoglobin molecules easily
