transport animals Flashcards
1
Q
What is a transport system?
A
The system that transports required
substances around the body of an
organism
2
Q
Why are specialised transport
systems needed in
multicellular animals?
A
• High metabolic demands (need lots of O2 and food & produce lots of waste products) so diffusion over long distances isn’t enough to supply the quantities needed • SA:V ratio gets smaller as multicellular organisms get bigger, so the amount of surface area available to absorb or remove substances gets relatively smaller • 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 products of metabolism need to be removed from the cells and transported to excretory organs
3
Q
What is a circulatory system?
A
The transport system of an animal • Liquid transport medium that circulates around the system (blood) • Vessels that carry the transport medium • Pumping mechanisms to move the fluid around the system
4
Q
What is a mass transport
system?
A
A transport system where
substances are transported in a
mass of fluid
5
Q
What is an open circulatory
system?
A
A circulatory system with a heart but few vessels to contain the transport medium. • Transport medium is pumped straight from the heart into the body cavity (haemocoel) , then it comes into direct contact with the tissues and the cells • This is where exchange takes place between the transport medium and the cells • Transport medium returns to the heart through an open-ended vessel • Mainly found in invertebrate animals inc. insects and molluscs
6
Q
Describe the circulatory
system in insects
A
• Insect blood = haemolymph; it doesn’t carry O2 or CO2, it transports food and nitrogenous waste products & cells involved in defence against disease • Body cavity is split by membrane and the heart extends along the length of the thorax and abdomen • The haemolymph circulates, but steep diffusion gradient cannot be maintained for efficient diffusion • Amount of haemolymph flowing through a particular tissue can’t be varied to meet changing demands
7
Q
What is a closed circulatory
system?
A
A circulatory system where the blood is enclosed in blood vessels and does not come into direct contact with the cells of the body beyond the blood vessels • Amount of blood flowing to a particular tissue can be adjusted by widening or narrowing of blood vessels • Contain a blood pigment that carries the respiratory gases • Found in many different animal phyla including: echinoderms, cephalopod molluscs, annelid worms and vertebrate groups (including mammals)
8
Q
What is a single closed
circulatory system?
A
A circulatory system where the blood flows through the heart and is pumped out to travel all around the body before returning to the heart • Blood passes through 2 sets of capillaries before it returns to the heart • 1st: Exchanges O2 and CO2 • 2nd: In the different organ systems, substances are exchanged between the blood and the cells • Due to passing though these 2 sets of very narrow vessels, blood pressure in the system drops, and so the blood returns back to the heart slowly • Limits efficiency of the exchange processes, so the activity of animals tends to be relatively low
9
Q
Explain how fish can be so
active with a single closed
circulatory system
A
• Low metabolic demands on their bodies and efficient gaseous exchange • Body weight is supported by water they live in and they don’t maintain their own body temperature • Countercurrent gaseous exchange mechanism in their gills that allows them to take lots of O2 from water
10
Q
What is a double closed
circulatory system?
A
A circulatory system where the blood travels twice through the heart for each circulation of the body. Most efficient system for transporting substances around the body and involves 2 separate circulations • 1st: Blood is pumped from the heart to the lungs to pick up O2 and unload CO2, and then returns to the heart • 2nd: Blood flows through the heart and is pumped out to travel all around the body before returning to the heart again Each circulate only passes through one capillary network, meaning that a high pressure and fast flow of blood can be maintained
11
Q
Describe the following components found in some blood vessels: 1. Elastic fibres 2. Smooth muscle 3. Collagen
A
1. Composed of elastin and can stretch and recoil, providing vessel walls with flexibility 2. Contracts or relaxes, which changes the size of the lumen 3. Provides structural support to maintain the shape and volume of the vessel
12
Q
Describe the roles of arteries
A
Carry blood away from the heart to the tissues of the body • Carry oxygenated blood • EXCEPT in the pulmonary artery, which carries deoxygenated blood from the heart to the lungs, and the umbilical artery (during pregnancy) which carries deoxygenated blood form the foetus to the placenta • Blood in arteries is under higher pressure than blood in the veins
13
Q
Describe the structure of
arteries
A
Artery walls contain elastic fibres, smooth muscle and collagen. The outer layer of an artery (endothelium) is smooth so the blood flows easily over it Wall consists of 3 layers: • Inner layer (tunica intima) consists of a thin layer of elastic tissue which allows the wall to stretch (within limits maintained by collagen) to take the larger blood volume, and then recoil to help maintain blood pressure • Middle layer (tunica media) consists of a thick layer of smooth muscle • Outer layer (tunica adventitia) is a relatively thick layer of collagen and elastic tissue. This provides strength to withstand the high pressure, and recoil to maintain the pressure
14
Q
What happens to the elastic
fibres in between the
contractions of the heart?
A
The elastic fibres recoil ad return to their original length, helping to even out the surges of blood pumped from the heart to give a continuous flow
15
Q
Describe the structure of
arterioles
A
• Arterioles link the arteries and the capillaries • Have more smooth muscle and less elastin in their walls than arteries, as they have little pulse surge • Can constrict or dilate to control the flow of blood into individual organs • Vasoconstriction: when the smooth muscle in the arteriole contracts, it constricts the vessel and prevent blood flowing into a capillary bed • Vasodilation: when the smooth muscle in the wall of an arteriole relaxes, blood flows into the capillary bed
16
Q
What are capillaries?
A
Microscopic blood vessels that link the arterioles with the venues, forming and extensive network through all the tissues of the body. They have very thin walls and allow the exchange of materials between the bloc and tissue fluid
17
Q
How are capillaries adapted for
their role?
A
• Provide a very large surface area for the dissuasion of substances into and out of the blood • Walls are 1 endothelial cell thick, giving a very thin layer for diffusion • Total cross sectional area of the capillaries is always greater than the arteriole supplying them so the rate of blood flow falls • Slow movement of blood through capillaries gives more time for exchange of materials by diffusion between the blood and the cells • Lumen is very narrow so red blood cells squeeze against the walls as they pass through, helping the transfer of O2 as it reduces diffusion path to the tissues. Also increases resistances and reduces rate fo flow • Walls are leaky allowing blood plasma and dissolved substances to leave the blood
18
Q
Describe the roles of veins
A
• Carry blood away from the cells of the body towards the heart • They carry deoxygenated blood • EXCEPT pulmonary vein (carries oxygenated blood from the Lins to the heart), and umbilical vein (carries oxygenated blood from the placenta to the foetus)
19
Q
Describe the structure of veins
A
• Walls have lots of collagen, relatively little elastic fibre and the vessels have a wide lumen smooth endothelium to ease blood flow • Thinner layers of collagen, smooth muscle and elastic tissue than in artery walls (because they don’t need to stretch and recoil and are not actively constricted in order to reduce blood flow) • Contain valves to help the blood flow back to the heart and prevent it flowing in the opposite directions
20
Q
How is blood kept flowing in
the right direction in veins?
A
• As walls are thin, veins can be flattened by the action of surrounding skeletal muscle • Contraction of the surrounding skeletal muscle applies pressure to the blood, forcing the blood to move along in a direction determined by the valves
21
Q
Do veins have a pulse?
A
No. The surges from the heart
pumping are lost as the blood
passes through the narrow
capillaries.
22
Q
Describe venules
A
• They link the capillaries with the veins • They have very thin layers of muscle and elastic tissue outside the endothelium, and a thin outer layer of collagen • Several venules join to form a vein
23
Q
What are the adaptations of
veins to overcome the problem
of transporting blood under
low pressure?
A
• Most veins have one way valves at intervals (flaps or inholdings of the inner lining of the vein) that only open when blood flows in the direction of the heart • Many of the bigger veins run between the big active muscles in the body; when the muscles contract, they squeeze the veins, forcing blood towards the heart • Breathing movements of the chest act as a pump. The pressure changes and squeezing actions move blood in veins of the chest and abdomen towards the heart
24
Q
What does blood consist of?
A
• Plasma (55%) - main component; yellow fluid containing many dissolved substances and carrying blood cells • Red blood cells (erythrocytes) • White blood cells (leucocytes) • Platelets - fragments of large cells called megakaryocytes, and they are involved in the clotting mechanism of the blood • Dissolved glucose, amino acids, mineral ions, hormones • Large plasma proteins
25
Q
Describe 3 plasma proteins
A
• Albumin - important for maintain the osmotic potential in the blood • Fibrinogen - important in blood clotting • Globulins - involved in transport and the immune system
26
Q
What are the functions of the
blood?
A
Maintenance of a steady body temperature • Acts as a buffer, minimising pH changes Transport of: • O2 to, and CO2 from, the respiring cells • Digested food from the small intestine • Nitrogenous waste products from the cells to the excretory organs • Hormones • Food molecules from storage compounds to the cells that need them • Platelets to damaged areas • Cells and antibodies involved in the immune response
27
Q
What is oncotic pressure?
A
The tendency of water to move into the blood in the capillaries from the surrounding fluid by osmosis as a result of the plasma proteins (which gibe the blood in the capillaries a low water potential) • - 3.3 kPa
28
Q
What is hydrostatic pressure?
A
The pressure created by water in an enclosed system. As blood flows through the arterioles into the capillaries, it is still under pressure every time the heart contacts. This is hydrostatic pressure • 4.6 kPa at arterial end • 2.3 kPa at venous end
29
Q
What is tissue fluid?
A
The solution surrounding the cells of multicellular animals. Similar to blood plasma, but doesn’t contain most of the cells found in blood, nor does it contain plasma proteins Diffusion takes places between the blood and the cells through the tissue fluid
30
Q
Describe the formation of
tissue fluid
A
• At the arterial end, hydrostatic pressure is higher than oncotic pressure attracting water in by osmosis, so fluid is squeezed out of the capillaries • This fluid fills the spaces between the cells and is called tissue fluid
31
Q
What happens as blood moves
through the capillaries towards
the venous system?
A
The balance of forces changes • Hydrostatic pressure falls to 2.3kPa in the vessels, as fluid has moved out and the pulse is lost • Oncotic pressure is now stronger than hydrostatic pressure, so water moves back into the capillaries by osmosis • By the time blood returns to veins, 90% of the tissue fluid is back in the blood vessels
32
Q
What is lymph?
A
Modified tissue fluid that is collected in the lymph system • 10% of the liquid that leaves the blood vessels drains into lymph capillaries • Similar in composition to plasma and tissue fluid, but has less O2 and fewer nutrients • Contains fatty acids absorbed from villi in the small intestine
33
Q
How is fluid in lymph vessels
transported?
A
• Through the squeezing of body muscles • One-way valves (like in veins) prevent back flow • Eventually lymph returns to the blood, flowing into the right and left subclavian veins
34
Q
Describe the lymph nodes
A
• Found along the lymph vessels • Lymphocytes build up here when necessary and produce antibodies which are then passed into the blood • Also intercept bacteria and debris from the lymph, which are ingested by phagocytes found in the nodes • Major sites: neck, armpits, stomach, groin
35
Q
What are enlarged lymph
nodes a sign of?
A
That the body is fighting off an
invading pathogen
36
Q
Describe haemoglobin (in terms of transporting oxygen)
A
Very larger globular conjugated protein made up of 4 peptide chain, each with a Fe2+ containing haem group which is said to have a high affinity for oxygen • The Fe2+ ion can attract and hold a single O2 molecule • 300 million haemoglobin molecules in each red blood cell, and each can bind to 4 O2 molecules
37
Q
What is the reaction for oxygen
binding with haemoglobin?
A
Hb + 4O2 ⇌ Hb(O2)4
haemoglobin + oxygen ⇌ oxyhaemoglobin
38
Q
Describe how oxygen is
carried by erythrocytes
A
1. In the lungs, O2 moves into the erythrocytes and binds with the haemoglobin 2. Arrangement of haemoglobin molecule means that as soon as one O2 molecule binds to a haem group, the molecule changes shape, making it easier for the next O2 molecules to bind (known as positive cooperativity) 3. O2 is bound to the haemoglobin so, free O2 concentration in the erythrocyte stays low and steep diffusion gradient is maintained until all of the haemoglobin is saturated with O2 4. When blood reaches body tissues, O2 moves out of the erythrocytes down a concentration gradient 5. Once the first O2 molecule is released by the haemoglobin, the molecule changes shape, and it becomes easier to remove the remaining O2 molecules
39
Q
What is an oxygen dissociation
curve?
A
Graph showing the relationship between oxygen and haemoglobin at different partial pressures of oxygen (pO2) • They show the affinity of haemoglobin for oxygen
40
Q
Describe the oxygen
dissociation curve graph
A
• A very small change in the pO2 in the surrounds makes a significant difference to the saturation of the haemoglobin with O2 because once the first O2 is added, change in shape of molecule means other O2 are added rapidly • Curve levels out at highest pO2s because all the haem groups are bound to O2 so the haemoglobin is saturated
41
Q
What is the effect of partial
pressure on the movement of
oxygen in the body?
A
• High pO2 in the lungs means that the haemoglobin in erythrocytes is rapidly loaded with O2 • Relatively small drop in respiring tissues means O2 is released rapidly from the haemoglobin to diffuse into the cells • This effect is enhanced by relatively low pH in tissues compared with the lungs
42
Q
How much of the O2 carried in
erythrocytes is released into
the body cells when you’re not
very active?
A
• Only 25%
• The rest acts as a reservoir for
when the demands of the body
increase suddenly
43
Q
What is the effect of carbon
dioxide?
A
At high partial pressures of CO2, haemoglobin gives up oxygen more easily. This is known as the Bohr effect • Bohr shift on oxygen dissociation curve = shift to the right Important in the body because as a result: • In active tissues with high pCO2, haemoglobin gives up its O2 more readily • In the lungs where the proportion of CO2 in the air is relatively low, O2 bids to the haemoglobin molecules easily
44
Q
What is the difference between
fetal and adult haemoglobin
and why?
A
Fetal haemoglobin has a higher affinity for oxygen than adult haemoglobin at each point along the dissociation curve • Foetus completely depends on its mother to supply it with oxygen • Mother’s oxygenated blood runs close to the deoxygenated fetal blood in the placenta • If fetal blood had the same affinity for O2 as the blood of the mother, the little or no O2 would be transferred to the blood of the foetus • Fetal haemoglobin has a higher affinity for O2, so it removes O2 from the maternal blood as they move past each other • Fetal haemoglobin on oxygen dislocation curve = shift to the left
45
Q
What are the 3 ways in which
carbon dioxide is transported?
A
• 5% is dissolved in the plasma • 10-20% is combined with the main groups in polypeptide chain of haemoglobin to form a compound called carbaminohaemoglobin • 75-85% is converted into hydrogencarbonate ions (HCO3-) in the cytoplasm of red blood cells
46
Q
What happens when CO2
diffuses into red blood cells?
A
It combines with water to form a weak acid called carbonic acid. This reaction is catalysed the enzyme carbonic anhydrase CO2 + H2O ⇌ H2CO3 The carbonic acid then dissociates to release H+ and HCO3- ions H2CO3 ⇌ HCO3- + H+
47
Q
What happens to the HCO3-
and H+ ions next?
A
Hydrogencarbonate ions (HCO3-) • Diffuse out of the red blood cell into the plasma • Chloride shift - charge in the red blood cell is maintained by the movement of chloride ions (Cl-) from the plasma into the red blood cell Hydrogen ions (H+) • Build of of these could cause the contents of the red blood cell to become very acidic • Taken out of solution by associating with haemoglobin to produce haemoglobinic acid (HHb) • The haemoglobin is acting as a buffer (a compound that maintains a constant pH)
48
Q
What is the benefit of
converting the carbon dioxide
into hydrogencarbonate ions?
A
Carbon dioxide must be removed from the body or it makes the blood dangerously acidic .Since carbon dioxide is quickly converted into bicarbonate ions, this reaction allows for the continued uptake of carbon dioxide into the blood down its concentration gradient
49
Q
What happens when the blood
reaches the lung tissue?
A
• Relatively low concentration of carbon dioxide • Carbonic anhydrase catalyses the reverse reaction, breaking down carbonic acid into CO2 and water • HCO3- ions diffuse back into the erythrocytes and react with H+ ions to form more carbonic acid • When this is broken down by carbonic anhydrase it releases free CO2, which diffuses out of the blood into the lungs • Cl- ions diffuse out of the erythrocytes back into the plasma down an electrochemical gradient
50
Q
Describe the Bohr effect
A
Effect an increasing concentration of CO2 has on haemoglobin • CO2 enters erythrocytes forming carbonic acid, which dissociates to release H+ ions • H+ ions make pH of cytoplasm more acidic • Acidity alters tertiary structure of haemoglobin and reduces the affinity of it for O2 • Haemoglobin is unable to hold as much O2, and O2 is released from the oxyhemoglobin to the tissues • Respiring tissues = more CO2, so more O2 will be released
51
Q
Why is the Bohr effect
important?
A
It results in more O2 being released where more CO2 is produced in respiration, which is what muscle need for aerobic respiration to continue
52
Q
Describe the flow of blood
through the right side of the heart
A
Deoxygenated blood 1. Enters the right atrium from the superior and inferior vena cave at relatively low pressure 2. As blood flows in, slight pressure builds up until the AV valve opens to let blood pass into the right ventricle 3. When both the atrium and ventricle are filled with blood, the atrium contracts, forcing all the blood into the right ventricle and stretching the ventricle walls 4. As right ventricle starts to contract, AV valve closes, preventing back-flow of blood 5. Tendinous cords make sure that the valves are not turned inside out by the pressures exerted when the ventricle contracts 6. Right ventricle contracts fully and pumps oxygenated blood through the semilunar valves into the pulmonary artery, which transports it to the capillary beds of the lungs. Semilunar valves prevent back-flow of blood into the heart.
53
Q
Describe the flow of blood
through the left side of the heart
A
Oxygenated blood 1. Enters the left atrium from the pulmonary vein 2. As pressure in the atrium builds, the AV valve opens, so the ventricle also fills with blood 3. When both the atrium and ventricle are full, the atrium contracts, forcing all the blood into the left ventricle 4. The left ventricle then contracts and pumps oxygenated blood through semilunar valves into the aorta and around the body 5. As the ventricle contracts, the AV valve closes, preventing any back flow of blood
54
Q
How are the following chambers adapted for the blood pressure they handle? 1. Atria 2. Right ventricle 3. Left ventricle
A
Atria • Muscle of atrial walls is very thin • These chambers do not need to create much pressure • Function is to receive blood from veins and push it into ventricles Right Ventricle • Thicker walls than atria • Needed to pump blood out heart • Pumps deoxygenated blood to the lungs, which are beside the heart, so blood doesn’t travel very far • Alveoli in the lungs are very delicate and could be damaged by very high blood pressure Left Ventricle • Walls 2 or 3 times thicker than RV • Blood from LV pumped out aorta so needs enough pressure to overcome the resistance of systemic circulation
55
Q
What is the cardiac cycle?
A
The events of a single heartbeat
(which lasts about 0.8 seconds in a
human adult), composed of diastole
and systole
56
Q
What happens in diastole?
A
• The heart relaxes • The atria and then the ventricles fill with blood • Volume and pressure of blood in the heart builds as the heart fills, but the pressure in the arteries is at a minimum
57
Q
What happens in systole?
A
• The atria contract (atrial systole) followed by the ventricles (ventricular systole) • Pressure inside the heart increases dramatically and blood is forced out of the right side of the heart to the lungs, and from the left side to the main body circulation • Volume and pressure of the blood in the heart are low at the end of systole • Blood pressure in the arteries is at a maximum
58
Q
Describe pressure changes
during the cardiac cycle
A
Aortic pressure (brown) • Rises when ventricles contract as blood is forced into the aorta • Then gradually falls but never below 12 kPa, as the elasticity of its wall creates a recoil action • Recoil produces a temporary rise in pressure at the start of the relaxation phase Atrial pressure (pink) • Always relatively low because thin walls of the atrium can’t create much force • Highest when they are contracting, but drops when the left AV valve closes and its walls relax • Atria then fill with blood leading to a gradual build-up of pressure • Slight drop when left AV valve closes and some blood moves into the ventricle Ventricular pressure (yellow) • Low at first, but gradually increases as the ventricles fill with blood as the atria contract • Left AV valves close and pressure rises dramatically as thick walls of ventricle contract • As pressure rises above aortic pressure, blood is forced into the aorta past the semilunar valves • Pressure falls as the ventricles empty and the walls relax Ventricular volume (green) • Rises as atria contract and ventricles fill with blood, then drops suddenly as blood is forced out into the aorta when the semilunar valve opens • Volume increases again as the ventricles fill with blood
59
Q
Describe the sounds of the
heartbeat
A
• Made by blood pressure closing the heart valves • Two sounds of a heartbeat are described as “lub-dub” • 1st sound is when blood is forced against the AV valves as ventricles contract • 2nd sound is when a back flow of blood closes the semilunar valves in the aorta and pulmonary artery as the ventricles relax
60
Q
Why is cardiac muscle said to
be ‘myogenic’?
A
It has its own intrinsic rhythm at around 60 bpm. • Prevents the body wasting resources to maintain basic heart rate • Average resting heart rate of an adult is 70 bpm because other factors also affect heart rate (e.g. exercise, excitement and stress) • Basic rhythm of the heart is maintained by a wave of electrical excitation
61
Q
How is the basic rhythm of the
heart maintained?
A
1. A wave of electrical excitation begins in the pacemaker area called the SAN, causing atria to contract and so initiating the heartbeat. Layer of nonconducting tissue prevents excitation passing directly to the ventricles 2. Electrical activity form the SAN is picked up the the AVN, which imposes a slight delay before stimulating the bundle of His ( a bundle of conducting tissue made up of Purkyne fibres) which penetrate through the septum between the ventricles 3. bundle of His splits into 2 branches and conducts the wave of exception to the apex of the heart 4. At the apex, the Purkyne fibres spread out through the walls of the ventricles on both sides, Spread of excitation triggers contracting of ventricles, starting at apex. Starting here allows more efficient emptying of the ventricles
62
Q
What is the importance of the
delay is the spread of the
excitation from the SAN to the
AVN?
A
Ensures that the atria have stopped
contracting before the ventricles
start
63
Q
What is an electrocardiogram
(ECG)?
A
A technique for measuring tiny changes in the electrical conductivity of the skin that result from the electrical activity of the heart. This produces a trace that can be used to analyse the health of the heart
64
Q
What is tachycardia?
A
• Heartbeat is very rapid; >100 bpm • Normal during exercise, fever, fear or anger • If abnormal, may be caused by problems in electrical control of heart • Treated by medication or surgery
65
Q
What is bradycardia?
A
• Heart rate slows down < 60 bpm • Common in people who are fit - training makes heart beat more slowly and efficiently • Severe bradycardia can be serious and may need an artificial pacemaker
66
Q
What is ectopic heartbeat?
A
• Extra heartbeats that are out of normal rhythm • Most people have at least 1 a day • Usually normal but can be linked to serious conditions when they are frequent
67
Q
What is atrial fibrillation (example of
arrythmia)?
A
• Abnormal rhythm of the heart • Rapid electrical impulses generated in atria so they contract very fast and not properly • Only some of impulses passed to ventricles, which therefore contract less often, so heart doesn’t pump blood effectively
