Transport in Animals
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- Created by: LBCW0502
- Created on: 28-12-16 17:28
Why do animals needs specialised transport systems?
High metabolic demands, multi-cellular organisms have a small SA:Vol ratio, hormones/digested food/waste products need to be transported
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Describe the features of a circulatory system (3)
They have a liquid transport medium that circulate around the system (blood). They have vessels that carry the transport medium. They have a pumping mechanism to move the fluid around the system
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What is a mass transport system?
Substances are transported in a mass fluid with a mechanism for moving the fluid around the body
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Describe the features of an open circulatory system
Very few vessels to contain transport medium, pumped straight from heart to body cavity (haemocoel) under low pressure. Transport medium comes into direct contact with tissues/cells (exchange takes place). Transport medium returns to heart
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In which organisms are open-ended circulatory systems found?
Invertebrate animals, including insects and molluscs
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Where does gas exchange take place in an insect?
In the tracheal system
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What is haemolymph?
Insect blood which doesn't carry oxygen or carbon dioxide but transports food and nitrogenous waste products and cells involved in defence agains disease
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What is a disadvantage of open circulatory system?
The haemolymph circulates but steep diffusion gradients cannot be maintained for efficient diffusion, so the amount of haemolymph flowing to a particular tissue cannot be varied to meet changing demands
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Describe the features of a closed circulatory system (1)
Blood is enclosed in blood vessels/not in contact with cels, heart pumps blood under pressure quickly and blood returns directly to the heart. Substances leave/enter blood by diffusion through walls of blood vessels
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Describe the features of a closed circulatory system (2)
The amount of blood flowing to a particular tissue can be adjusted by widening or narrowing blood vessels. Most closed circulatory systems contain a blood pigment that carries the respiratory gases
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In which organisms are closed circulatory systems found?
Many different animal phyla, including echinoderms (sea urchins and starfish), cephalopod molluscs, including octopods, squid, annelid worms (common earthworm) and all vertebrate groups including mammals
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Describe the features of a single closed circulatory system
Found in fish and annelid worms. Blood flows though the heart and is pumped out to travel all around the body before returning to the heart. Blood travels only once through the heart for each complete circulation of the body
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What happens when blood passes through the first set of capillaries?
Exchanges oxygen and carbon dioxide
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What happens when blood passes through the second set of capillaries?
In the different organ systems, substances are exchanged between the blood and cells
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What happens to the blood pressure when blood passes through these two sets of capillaries?
Blood pressure decreases and returns to the heart slowly. This limits the efficiency of the exchange processes so the activity levels of animals with single closed circulations tend to be relatively low
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Describe the single circulatory system in fish
Efficient system (can be active). Have a countercurrent gaseous exchange mechanism in their gills (large oxygen uptake). They don't need to maintain temperature due to being in water
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Describe the features of a double closed circulatory system
Blood is pumped from the heart to the lungs to pick up oxygen and unload carbon dioxide and then returns to the heart. Blood flows through the heart and is pumped out to travel all around the body before returning to the heart again
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Name the two circulation systems in a double closed circulatory system
Pulmonary circulation and systemic circulation
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In which organisms are double closed circulatory systems found?
Birds and mammals
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Why is the double closed circulatory system the most efficient system for transporting substances around the body?
Blood travels twice through the heart for each circuit of the body. Each circuit - to the lungs and to the body - only passes one capillary network, which means a relatively high pressure and fast flow of blood can be maintained
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What are the components of blood vessels? (3)
Elastic fibres (stretch and recoil - flexibility), smooth muscle (contacts/relaxes to change size of lumen) and collagen (provides structural support to maintain shape and volume of vessel)
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What do the arteries carry?
Oxygenated blood (under high pressure)
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What does the pulmonary artery carry?
Deoxygenated blood
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What are the artery walls composed of?
Equal amounts of elastin and smooth muscle and little collagen
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What is the significance of elastin fibres in the artery walls?
Enables arteries to withstand force of blood pressure out of heart and stretch (within limits maintained by collagen) to take larger volume. In between contractions, elastic fibres recoil and return to original length -even out surges/continuous flow
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What is the significance of smooth endothelium?
Allows blood to flow easily
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Describe the features of arterioles
The link arteries and capillaries. They have more smooth muscle and less elastin in their walls compared to arteries (little pulse surge). Involved in vasoconstriction and vasodilation
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What is vasoconstriction?
Smooth muscle in arterioles contract to constrict vessel and prevent blood flowing into a capillary bed
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What is vasodilation?
Smooth muscle in the wall of an arteriole relaxes, blood flows through into the capillary bed
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What are capillaries?
Microscopic blood vessels that link the arterioles with the venules. They form an extensive network through all the tissues of the body
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Describe the features of the capillary
Small lumen (erythrocytes travel single file). Substances exchanged between tissue cells and blood. Gaps between endothelial cells that make up capillary walls in most areas of the body are large. Substances pass out of capillaries into fluid
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Describe the capillaries in the central nervous system
Have very tight junctions between cells
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Describe the content of the capillaries
Blood entering the capillaries from arterioles is oxygenated. By the time it leaves capillaries for venules, it has less oxygen and more carbon dioxide (deoxygenated)
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Describe the content of blood in the lungs and in the placenta
Contain deoxygenated blood entering the capillaries and oxygenated blood leaving in the venules
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Describe the adaptations of capillaries (3)
Provide very large SA for diffusion, total cross-sectional area of capillaries is greater than the arteriole supplying them (slow movement of blood allows more time for exchange). Walls are a single endothelial cell thick (thin layer for diffusion)
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What do veins carry?
Deoxygenated blood (pulmonary vein carries oxygenated blood)
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What is the inferior vena cava?
One of the main blood vessels which carries deoxygenated blood from lower parts of the body to the heart
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What is the superior vena cava?
One of the main blood vessels which carries deoxygenated blood from the head and upper body to the heart
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Why do veins not have a pulse?
The surges from the heart pumping are lost as the blood passes through the narrow capillaries (veins hold a large reservoir of blood)
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Compare the blood pressure in veins and arteries
Blood pressure in veins is very low compared with the pressure in arteries
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Why do medium-sized veins contain valves?
To prevent the back flow of blood
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Describe the walls of the veins
Contains lost of collagen and little elastic fibre (wide lumen and smooth endothelium so blood flows easily)
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Describe the features of venules
Links the capillaries with the vein. Have very thin walls with just a little smooth muscle
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What are the adaptations of veins (3)
One-way valves, bigger veins un between big/active muscles. When the muscle contract they squeeze the vein to force blood towards the heart. Breathing movements of the chest act as a pump. Pressure changes move blood in the veins towards teh heart
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Give examples of substances in the blood
Glucose, amino acids, mineral ions, hormones, large plasma proteins, albumin, fibrinogen, globulins, platelets and erythrocytes
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What are platelets?
Fragments of large cells (megakaryocytes found in red bone marrow) - involved in clotting mechanism of the blood
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What colour is blood plasma?
Yellow
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What are the functions of the blood?
Transport oxygen, carbon dioxide, digested food, nitrogenous waste products, chemical messages, food molecules from storage compounds, platelets to damaged areas and cells/antibodies involved in immune response. Maintains body temperature/is a buffer
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What happens when substances dissolved in plasma pass through fenestrations in the capillary walls?
Large plasma proteins remain in the capillaries - leading to a high solute concentration (osmotic effect). Water moves into the blood in capillaries from surrounding fluid
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What is osmotic pressure?
The tendency of water to move into the blood by osmosis (-3.3 kPa)
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What is hydrostatic pressure?
Pressure from the surge of blood that occurs every time the heart contracts
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What is tissue fluid?
Fluid which fills the spaces between cells. It has the same composition as the plasma without the red blood cells and plasma proteins. Diffusion takes place between blood and cells through tissue fluid
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How do you calculate filtration pressure?
Hydrostatic pressure - oncotic pressure
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What is the lymph?
10% of liquid that leaves blood vessels drains into a system of blind-ended tubes called lymph capillaries. It has a similar composition to plasma and tissue fluid but has less oxygen and fewer nutrients. It contains fatty acids absorbed from villi
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Do lymphs contain one-way valves?
Yes
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Describe the features of lymph nodes
Lymphocytes build up in the lymph node when necessary and produce antibodies (passed into blood). Lymph nodes intercept bacteria and other debris, which are ingested by phagocytes found in nodes
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What do enlarged lymph nodes suggest?
The body is fighting off an invading pathogen (doctors examine neck, armpits, stomach or groin in patients - sites of major lymph nodes/lymph glands)
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Describe the features of erythrocytes
Biconcave shape (large SA), no nucleus (more room for haemoglobin), short life (120 days in bloodstream)
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Describe the features of haemoglobin
Red pigment which carries oxygen (gives colour), large globular conjugated protein made up of 4 peptide chains with iron (haem prosthetic group). Each Hb can bind to 4 oxygen molecules
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What is positive cooperativity?
As soon as one oxygen molecule binds to a haem group, the molecule changes shape, making it easier for the next oxygen molecules to bind
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What do oxygen dissociation curves show?
The affinity of haemoglobin for oxygen
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What is partial pressure also known as?
Concentration (e.g. partial pressure of oxygen)
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Describe and explain the oxygen dissociation curve?
A low pO2, few haem groups are bound to oxygen, so Hb doesn't carry much oxygen. At higher pO2, more haem groups bond (easier for more oxygen to be picked up). Hb becomes saturated as all haem groups become bound
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Describe the Bohr effect
In active tissues with a high partial pressure of carbon dioxide, Hb gives up oxygen more readily. In the lungs (low proportion of CO2) oxygen binds to Hb molecules easily
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Why does foetal haemoglobin have a higher affinity for oxygen compared to adult haemoglobin?
If the blood of a foetus had the same affinity for oxygen, then little oxygen will be transferred to the foetus
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Describe the ways carbon dioxide is transported from tissues to lungs
Carried dissolved in plasma, combines with amino groups in polypeptide chains of Hb to form carbaminohaemoglobin. Converted into hydrogen carbonate ions in erythrocytes
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Describe chloride shift
Carbon dioxide diffuses into the erythrocyte. Carbon dioxide reacts with water in the presence of carbonic anhydrase to form carbonic acid. Carbon acid dissociates to form hydrogen ions and hydrogen carbonate ions. HCO3 ions move out and Cl- ions in
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What is the advantage of carbon dioxide being converted in hydrogen carbonate ions?
Maintains a steep concentration gradient for carbon dioxide to diffuse from the respiring tissues into erythrocytes
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What happens when blood reaching the tissue has a low concentration of carbon dioxide?
Carbonic anhydrase catalyses the reverse reaction to produce CO2 and H2O. HCO3- ions diffuse back into RBCs and react with H+ to form more H2CO3. This is broken down to release free CO2 (diffuses out of blood/into lungs). Cl- diffuses out RBCs
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How does haemoglobin act as a buffer?
Prevent change in pH by accepting free hydrogen ions in a reversible reaction to form haemoglobinic acid
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Which side of the heart contains deoxygenated blood?
Right side (pumped to lungs)
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Which side of the heart contains oxygenated blood?
Left side (pumped to the body)
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Which type of muscle is the heart made of?
Cardiac muscle
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What is the function of the coronary artery?
Supply the cardiac muscle with oxygenated blood it needs to keep contracting and relaxing all the time
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Which type of membranes surrounds the heart?
Inelastic pericardial membranes - help prevent the heart from over-distending with blood
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What are the four chambers of the heart?
Right atrium, right ventricle, left atrium, left ventricle
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Do the atria than thin or thick muscular walls?
Thin
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Name the valves in the heart
Atrio-ventricular valves (bicuspid, tricuspid) and semi-lunar valves
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What is the function of the valves?
To prevent the back-flow of blood
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Through which blood vessel does deoxygenated blood enter the right atrium?
Superior vena cava (upper body and head) and inferior vena cava (lower body)
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Through which blood vessel does oxygenated blood enter the left atrium?
Pulmonary vein
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Through which blood vessel does deoxygenated blood leave the right ventricle?
Pulmonary artery
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Through which blood vessel does oxygenated blood leave the left ventricle?
Aorta
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What is the function of the tendinous cords?
To make sure the valves are not turned inside out by the pressured exerted when the ventricles contract
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Why is the muscular wall of the left side of the heart thicker than that of the right?
The right side pumps blood at a short distance (to the lungs) and only has to overcome resistance of pulmonary circulation. The left side needs to produce sufficient force to overcome resistance of aorta/arterial systems and move blood under pressure
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What is the septum?
The inner dividing wall of the heart which prevents the mixing of deoxygenated and oxygenated blood (right and left side of the heart fill and empty together)
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How long does the cardiac cycle last for (in seconds)?
0.8 seconds
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Describe diastole
Heart muscle relaxes. Atria and then ventricles fill with blood. Volume and pressure of blood in the heart increases as heart fills, but pressure in arteries is at a minimum
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Describe atrial systole and ventricular systole
Pressure inside the heart increases and blood is forced out of the right side of the heart to the lungs and from the left side to main circulation. Volume/pressure are low at the end (blood pressure in arteries at minimum)
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Describe the two sounds of a heartbeat
'lub-dub'
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What is the reason for the first heart beat?
Blood is forced against atrio-ventricular valves as ventricles contract
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What is the reason for the second heart beat?
Back flow of blood closes the semilunar valves in the aorta and pulmonary artery as the ventricles relax
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Why is the cardiac muscle myogenic?
It has its own intrinsic rhythm at around 60bpm which prevents the body wasting resources maintaining the basic heart rate
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What is the average resting heart rate?
70bpm (varies depending on exercise, excitement, stress)
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Explain the process of the basic rhythm of the heart (1)
A wave of electrical excitation beings in the sino-atrial node, causing the atria to contract (initiates heart beat). A layer of non-conducting tissue prevents excitation passing directly to the ventricles
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Explain the process of the basic rhythm of the heart (2)
The electrical activity from the SAN is picked up by the atrio-ventricular node. This imposes a slight delay before stimulating the bundle of His (conducting tissue- Purkyne fibres) which penetrate through septum between ventricles
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Explain the process of the basic rhythm of the heart (3)
Bundle of His splits into two branches and conducts the wave of excitation to the apex of the heart
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Explain the process of the basic rhythm of the heart (4)
At the apex the Purkyne fibres spread out through walls of the ventricles on both sides. The spread of excitation triggers contraction of ventricles, starting at the apex. Contraction starting at the apex allow more efficient emptying of the ventricl
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Why is the a delay of excitation at the AVN?
To ensure that the atria have stopped contracting before the ventricles start
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What is an electrocardiogram?
You can measure the spread of electrical excitation through the heart as a way of recording what happens as it contracts. This is the record of electrical activity of the heart. ECG doesn't measure electrical activity directly but tiny differences
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How are tiny electrical differences in the skin (resulting from the electrical activity of the heart) detected?
Electrodes are stuck painlessly to clean skin to (good contract/reliable results). Signal from each of the electrodes is fed into a machine which produces in ECG. ECGs can be used to diagnose a problem/treat it fast
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What is tachycardia?
Very rapid heart beat (over 100 bpm). This is normal for exercise/fever or when you are frightened/angry. If it is abnormal it may cause problems in electrical control of heart (treat with medication/surgery)
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What is bradycardia?
Slow heart rate (below 60bpm). People who are fit/training have this condition (heart beats slowly/efficiently). Severe bradycardia is treated with an artificial pacemaker to keep heart beat steady
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What is an ectopic heart beat?
Extra heart beats that are out of the normal rhythm. Most people have at least one a day. They are usually normal but can be linked to serious conditions when they are frequent
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What is atrial fibrillation? (1)
This is an example of arrhythmia (abnormal rhythm of heart beat). Rapid electrical impulses are generated in the atria. They contract fast (fibrillate) up to 400 times a minute
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What is atrial fibrillation? (2)
Atria don't contract properly and only some of the impulses are passed onto the ventricles, which contract less often. Hence, the heart does not pump blood very efficiently
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Other cards in this set
Card 2
Front
Describe the features of a circulatory system (3)
Back
They have a liquid transport medium that circulate around the system (blood). They have vessels that carry the transport medium. They have a pumping mechanism to move the fluid around the system
Card 3
Front
What is a mass transport system?
Back
Card 4
Front
Describe the features of an open circulatory system
Back
Card 5
Front
In which organisms are open-ended circulatory systems found?
Back
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