Chapter 8- Transport In Animals Flashcards
Why do larger animals have circulatory systems?
Larger animals have increased distances between body parts. Development of specialised organs resulted in the need for transport systems for oxygen, nutrients and wastes.
What does a circulatory system consist of?
A heart ( a pump) Blood vessels performing different functions Blood
How do single-celled organisms and very small animals get their oxygen and nutrients?
By diffusion through their body surface because the distance the substances have to travel is small, so the slow speed of diffusion is not a problem.
Diffusion gradients are also favourable because these animals are small and have relatively low levels of activity; their demand for nutrients and oxygen is not great.
What factors affect the need for a transport system
Transport distance
Sa:V
Level of activity
How does the transport distance affect the need of a transport system
The larger the size of the organism, the further distance oxygen has to reach.
Diffusion is a slow process, so the time taken for oxygen to reach the innermost cells would be so long, that the cells would die before they received it.
How does the SA:V affect the need of transport system
Oxygen diffuses through the surface of the small animal, so the surface area is a measure of supply of oxygen.
Then number of cells (therefore the volume of the organism) is an indication of the demand for oxygen.
Larger animals have a smaller SA:V; therefore have a smaller rate of diffusion
How does the level of activity affect the need of a transport system
Large-sized animals tend to move more and also produce more waste. Therefore, these animals need a transport system to remove the waste and provide them with their needed nutrients and oxygen.
What are the two main models of circulatory systems?
Single
Double
What does the ‘single’ and ‘double’ refer to?
The number of times the blood passes through the heart in one complete circuit of the body
What are single circulatory system
Blood passes the heart only once in a single circuit of the body
There is only one atrium and one ventricle
Fishes have these:
Deoxygenated blood is pumped by the heart to the gills, where it absorbs oxygen and carbon dioxide is excreted.
From here, the blood travels to the rest of the body, passing through organs in capillaries from which it delivers oxygen, before returning to the heart.
What is a double circulatory system
Blood passes through the heart twice during each circuit of the body
Left-oxygenated blood
Right-deoxygenated blood
In general, the oxygenated blood that travels through an organ goes directly back to the heart AND NOT ANY OTHER ORGAN.
The only exception is the blood going to the gut, which then goes to the liver via the hepatic portal vein before returning to the heart.
Advantages of a double circulation
As blood travels through capillaries, its pressure and speed both drop.
In double circulatory system, the blood only goes through one capillary network before returning to the heart. Whereas in a single circulatory system, the blood goes through two networks.
Therefore the blood flowing through a double circulatory system, has a higher blood pressure and a higher average speed of flow, which in turn helps maintains the steeper concentration gradients and makes exchange of materials more efficient.
What is the difference between a closed and open circulatory system
Open- the blood flow is not restricted to only the blood vessels; the blood flows through the vessels as well as the body cavity
Closed- blood circulates throughout the entire body within the blood vessels
Example of an organism with an open system
Insects have only one main blood vessel, the dorsal vessel. This delivers blood (called haemolymph in insects) into the haemocoel (the body cavity).
The insects also have a tubular heart in their abdomen. The haemolymph bathes the organs and then re-enters the heart through opening with one-way valve called ostia when the heart relaxes.
Since the oxygen is delivered to an insect (and carbon dioxide is given out) through tracheae, it can work with such a haphazard circulatory system.
What is an aorta
This carries oxygenated blood to the whole body at a high pressure
What is a pulmonary artery
Carries deoxygenated blood to the lungs
What is a coronary artery
Supplies the heart with oxygenated blood, which sends branches across the surface
The muscular walls of the heart are so thick that a separate blood supply outside the heart is required
What is a coronary vein?
It delivers deoxygenated blood to the right atrium along with the superior and inferior vena cava
How does the blood flow through a mammalian heart?
Deoxygenated blood is passed on to the right atrium via the superior vena cava, inferior vena cava and the coronary vein.
Then this blood is passed onto the right ventricle through the tricuspid valves. The blood then flows to the pulmonary artery via the semilunar valves. The blood is then oxygenated in the lungs. This oxygenated blood then flows to the left atrium via the pulmonary vein. This then is passed onto the the left ventricle via the bicuspid valves. Next, the blood flows to the aorta through the semilunar valves. This blood is then pumped to the whole body except the lungs
Why is the wall of the left ventricle the thickest
This is because it pumps the blood to the entire body (except the lungs) at a high pressure.
The blood flow is a high pressure because the blood needs to travel a long distance in order to reach and transport oxygen to every cell.
Why is the wall of the right ventricle less thick?
Less muscle is required to pump blood through the pulmonary circuit; the blood pressure here is not high and the distance the blood needs to travel is also very short therefore less muscle is needed.
The pulmonary circuit has less resistance than the circuit from the left ventricle.
This is because the lung is a spongy organ, being full of air, and has fewer arterioles, which provide most of the resistance.
Why do the atrium have the thinnest walls?
These only pump blood to their adjacent ventricles therefore have a very short distance to cover.
What is the purpose of the tendons?
The ventricles produce considerable pressure when they contract, so the flaps of the atrio-ventricular valves are attached to the ventricle walls by tendons to prevent the valves being blown inside out.
What is the cardiac cycle
The heart beats and relaxes in a regular cycle
First stage of cardiac cycle
Both chambers are relaxed and the pressures are low.
First stage of the cycle
The atrium starts to contract, and the pressure in it increases. The increase is relatively small, because the atrium has relatively thin muscular walls. There is also a small increase in the pressure of the ventricle caused by the blood flowing into it.
The semi-lunar valves are shut.
Second stage of the cardiac cycle
The atrium relaxes and the ventricle starts to contract. When the pressure in the ventricle exceeds the pressure above in the atrium, the atria-ventricular valve is forced shut.
Third stage of the cardiac cycle
Continued contraction of the ventricle, which has a thick muscular wall, increases the pressure in the ventricle considerably. The small rise in the atrial pressure is due to the closed atria-ventricular valve bulging into the atrium and putting a little more pressure on the blood.
Fourth stage of the cardiac cycle
When the pressure in the ventricle goes above that of the aorta, the semi-lunar valves open and the blood flows into the aorta. This increases the pressure in the aorta.
Fifth stage of the cardiac cycle
The ventricles start to relax, and the pressure in it starts to decrease.
Sixth stage of the cardiac cycle
When the pressure in the ventricle drops below that of the aorta, the semi-lunar valves close.
Seventh stage of the cycle
When the pressure in the ventricle drops below that of the atrium, the atria-ventricular valve opens. Blood has been flowing into the atrium from the body, causing a gradual rise in pressure that is released when the valve opens and blood can flow into the ventricle.
Eighth stage of the cycle
When the blood flows into the aorta, its walls (which are highly elastic) stretch and expand. When the blood flow slows, the elastic tissue recoils and puts extra pressure on the blood. This gives the blood as extra ‘push’, which means that the blood still flows from the heart during the period when both the atrium and the ventricle are relaxed. This is passive elastic recoil. It is not a contraction.
Lub Dub
Lub- Tricuspid and bicuspid valves shutting (which makes the noise); simultaneously, the aortic and pulmonary valves opening
Dub- pulmonary and aortic valves shutting (which makes the noise); simultaneously, the tricuspid and bicuspid valves opening
Definition of myogenic
Cardiac muscles can contract without stimulation from outside nerves.
What is the autonomic nervous system
The part of the nervous system that controls involuntary activity (e.g heart rate, change in size of blood vessels, peristalsis).
It consists of two parts: the parasympathetic and sympathetic nervous systems, which have opposite effects.
How does the autonomic nervous system affect the heart rate
It can adjust the heart rate to suit different circumstances.
The parasympathetic nerves decrease the heart rate and sympathetic nerves increase it.
Where does the heartbeat originate from
A patch of specialised muscle tissue in the upper wall of the right atrium, called the sino-atrial node. This is also known as the pacemaker. The nodal tissue can generate electrical impulses when it contracts. The nerve impulses set off a wave of muscular contraction across both atria. Non-conductive tissue between the atria and ventricles prevents the spread of the impulse to the ventricles, except at the atria-ventricular node.
What happens at the AV node
This node delays the signal for a short time(which allows the atria to complete their contraction) and then sends an impulse into the ventricles.
What happens after the AV node
Because blood has to be forced out of vessels at the top of the heart, it is best if the contraction of the ventricles starts at the bottom and moves upwards. To do this the AV node sends the impulse down specialised muscle fibres known as bundle of His to the bottom of the ventricle. This impulse is then send back up via another set of muscle fibres, the Purkyne fibres. This causes contractions as the impulse moves up the walls of the ventricles.
What is electrocardiography (ECG)
Used to detect heart activity and identify certain problems.
Produces an electrocardiogram
What is the P wave of the electrodiagram
This is caused by the depolarisation of the atria, resulting in their contraction.
Depolarisation is the balancing or reversal of the electrical charges.
What does the QRS complex show of the electrodiagram
Results from the depolarisation (contraction) of the ventricles
What does the T wave of the electrocardiogram show
Repolarisation of the ventricles (causing relaxation)
What is cause of U wave in the ECG
Uncertain
What is tachycardia (tacky)
The heart beats too fast
The resting heart rate is above 100bpm
The peaks are too close together
What is Bradycardia (broad)
The heart is beating too slow
The peaks are far apart
The heart is beating less than 60 bpm
Ectopic Heart beat
The heart beats too early
Fibrillation
Heartbeat is irregular and has lost its rhythm. Severe fibrillation can cause death.
What is tissue fluid
A liquid medium through which substances are transported from the blood vessels to the surrounding cells. This fluid also bathes and surrounds the cell.
What is lymph
Excess tissue fluid in returned to the blood, by a third fluid, lymph.
Components of Blood
Red blood cells (erythrocytes)
Responsible for the transport of oxygen and also play a role in the transport of carbon dioxide. Carried out by haemoglobin.
White blood cells (leukocytes)
Different white blood cells have different roles
Platelets
Cell fragments important in clotting process
Plasma
Liquid medium of the blood, which transports dissolved substances (including amino acids, sugars, fatty acids, hormones and other proteins, clotting factors and carbon dioxide)
Components of tissue fluid and where does it come from
This is formed from the plasma when it leaves the blood and goes to the surrounding tissues.
It contains many of the solutes present in the plasma except larger proteins which cannot escape from the capillaries.
It contains some white blood cells but no red blood cells or platelets
These white blood cells actively squeeze themselves through
What is lymph and how is it formed
Out of the fluid (plasma) leaving the blood and forming tissue fluid, 90% is returned to the capillaries. The remainder is returned to the bloodstream as lymph, via the lymphatic system. Lymph is similar to tissue fluid but contains more white blood cells.
The white blood cells collect in large numbers in the lymph nodes to fight infections, so tend to more common in lymph compared to tissue fluid.
What is the lymphatic system
This is a network of vessels and organs that connect to the circulatory system.
Swellings called lymph nodes are found at intervals throughout the system, the tonsils, spleen and thymus gland are part of the lymphatic system. These contain lymphocytes (B and T cells). So lymph (which is essentially tissue fluid) flows through these nodes, collecting these cells on the way along with the antibodies produced by the plasma cells. So, when this flows back to the bloodstream, it has more white blood cells and proteins despite being very similar to tissue fluid.
Which factors affect the movement of fluid to and from the capillaries?
Hydrostatic pressure: for example, blood pressure. This tends to force fluid out.
Oncotic pressure gradient: this tends to draw water in by osmosis.
What happens at the atrial end of the capillary
When blood enters the capillary network, its hydrostatic pressure is relatively high; this overcomes the water potential gradient to force fluid through the capillary walls.
No blood cells or large protein molecules can leave because they are too large to fit through the small gaps of the capillary walls.
What happens at the venous end of the capillary
The water potential gradient is largely unchanged. The hydrostatic pressure is now decreased due to the water potential gradient.
As a result, water re-enters the blood. 90% returns and the rest 10% return to blood as lymph.
Name of haemoglobin attached to an oxygen atom
Oxyhaemoglobin
Name of haemoglobin not attached to an oxygen atom
Deoxyhaemoglobin
Definition of affinity
A natural attraction.
Definition of partial pressure
The pressure exerted by one component of a mixture of gases, usually expressed in mm Hg or kPa
How is oxygen transported
The affinity of haemoglobin increases with increasing partial pressure of oxygen in the surrounding.
How does haem bind to oxygen
When one haem group absorbs oxygen, it alters the structure of the haemoglobin molecule so that it becomes easier to absorb a second molecule and third molecules of oxygen.
The fourth one however has some difficulty because there is already so much oxygen taken, that it does not have enough space to bind to more.
The effect of affinity on the transport of oxygen
The higher the affinity to oxygen
The less oxygen that is dissociated at a particular pressure
What is the Bohr Effect
Increasing levels of carbon dioxide lower the affinity of haemoglobin for oxygen, so that even more oxygen is released.
Fetal Haemoglobin
Fetus gets its oxygen from the mother’s blood via the placenta.
Partial pressure of oxygen in the placenta is much lower than the partial pressure in the lungs.
A fetus has a higher affinity to oxygen and therefore dissociates much less at a lower partial pressure
Carbon dioxide transport
Carbon dioxide diffuses into the red blood cell
Reacts with water to produce carbonic acid (H2CO3)
This dissociates to HCO3- and H+ ions
HCO3- diffuses out of the cell, leaving the cell positively charged overall and very acidic (low pH)
H+ binds to Haemoglobin which simultaneously ‘kicks’ out the remaining oxygen out of the cell
