3.2 Transport in Animals

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Who do small organisms not require circulatory systems
They are small enough and have a small enough SA:v ratio to rely on diffusion alone
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What features will an effective transport system have?
A fluid/medium to carry nutrients O2 and take away waste, a pump to create P to push fluid, specialised exchange surfaces, tubes/vessels to carry fluid by mass flow, two circuits
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What is an open circulatory system and what is an example?
Where the transport fluid does not stay contained in vessels but instead leave and ooze through tissues, insects use it
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What are some disadvantages of open circulatory systems?
Low blood pressure so slow blood flow, blood flow affected by body movements or lack of, meaning organisms have to keep moving to ensure blood flow
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What two types of closed circulatory systems can you have and whats the difference, with examples?
Single: blood goes through heart once e.g. fish and Double: Two separate circuits, one picks up O2 other brings it round body e.g. humans
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What is a closed circulatory system?
Blood stays inside blood vessels at all times
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What are the disadvantages of a single closed circulatory system?
The BP has to drop to pass through delicate capillaries e.g. in gills, meaning slow flow for rest of body so rate at which O2/nutrients delivered and waste taken away is slowed
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Why is it suitable for organisms such as fish to have single circulatory systems despite it's disadvantages?
Fish not as metabolically active as organisms such as mammals, ectotherm rather than endotherm, don't require as much E in general so single circulatory system is suitable for their needs
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What are the advantages of the double circulatory system?
BP remains low+safe in pulmonary circuit to avoid damage to delicate capillaries but can then increase BP to rest of body to deliver/remove substances quicker
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Why do mammals need a double circulatory system to meet their needs?
Need more E as they are active endotherms to generate own body heat and supply O2 for respiring active tissues
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What is the function of the arteries and what are they made up of?
To transport blood quickly at high P away from heart, thick walls made up of elastic fibres, smooth muscle+collagen, relatively small lumen to keep BP high, thick walls to handle the P
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What are the function of the arterioles?
Smaller vessels the arteries branch into as they get closer to tissues they are supplying, smooth muscle so can contract to control blood flow
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What are the capillaries and what is their structure like?
Smallest of all blood vessels, takes blood as close as possible to respiring cells to allow rapid transport of substances, very narrow lumen nearly same as 1 RBC, single-celled walls, leaky walls so plasma+substances can leave/enter blood
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What are veins and what are they made up of?
Carry blood back to the heart at lower BP so walls not as luck, larger lumen, collagen smooth muscle elastic fibre thinner walls, contain valves to prevent backflow
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What are venules and what are their function?
Collect blood from capillary bed to flow back into veins, thin smooth muscle elastic fibres and collagen walls
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What is plasma and what types of substances are present in it?
Liquid part of the blood, many dissolved substances e.g. O2, CO2, minerals, glucose, amino acids, hormones, plasma proteins, erythrocytes, various WBCs (leucocytes) and platelets
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What is tissue fluid and what types of substances are present in it?
Similar to blood plasma but does not contain most of the cells found in plasma + any of the plasma proteins
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What is lymph and what types of substances are present in it?
Fluid present in lymphatic system, similar to tissue fluid but more lymphocytes as they get produced at lymph nodes
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How is tissue fluid formed and what gets left behind in the blood?
At arterial end of capillary, high hydrostatic P, fluid gets forced out through tiny capillary pores, substances too large e.g. cells + proteins don't get pushed through
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What happens to the tissue fluid at the venous end of the capillary?
Most it returns to the capillary where P lower, carrying CO2 + wastes but 10% directed into different tubular system called lymphatic system to pass through lymph nodes and then drain into subclavian vein to return to blood system
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What is the name of the muscle that makes up the heart and the vessels that supply it with blood?
Cardiac muscle and coronary arteries covering heart surface to supply oxygenated blood to itself
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Where does deoxygenated blood from the blood flow?
Into heart from vena cava in right atrium, flows through atrioventricular valve into right ventricle, flows out right side of heart through semi-lunar valves into pulmonary artery to the lungs to get oxygenated
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Once blood gets oxygenated in the lungs, where does it flow?
Into left atrium from pulmonary vein, through atrioventricular valve into left ventricle, flows out left side through semi-lunar valves into aorta to rest of body
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What is the series of P changes occurs in one heartbeat and what are it's stages?
The cardiac stages: Diastole, atrial systole and ventricular systole
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Describe cardiac diastole
All chambers of the heart are relaxed, P higher in the arteries than the ventricles so the semi-lunar valves close. Blood flows into the atria.
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Describe atrial systole
Both of the atria contract at the same time, P is higher in the atria than the ventricles so the atrioventricular valves open, allowing blood into the ventricles
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Describe ventricular systole
Both of the ventricles contract at the same time, P inside ventricles higher than atria and arteries leaving heart, causing atrioventricular valves to close and semi-lunar valves to open, meaning blood leaves through arteries
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What does myogenic mean?
It means that the heart can initiate it's own contractions
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What area of the heart initiates a contraction and how does it do this?
The sinoatrial node (SAN) by generating waves of excitation (WOE), acts as the hearts pacemaker
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Describe how atrial contraction takes place
SAN produces a WOE, spreads down walls of atria (along muscle tissue membrane), causing contraction, stops at the base as it is unable to conduct
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What happens to the wave of excitations after triggering atrial systole before triggering ventricular systole?
The atrioventricular node (AVN) at the top of the inter ventricular septum is the only route the WOE can take, and here it gets delayed, allowing atria to finish contracting and all blood to flow into ventricles
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Describe how ventricular contraction takes place
After short delay at AVN, WOE travels down specialised Purkyne tissue down interventricular septum until heart apex and then travels up ventricle walls, meaning contraction happens from bottom to top so blood properly pushed out into arteries
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What type of graph does a electrocardiogram produce and how does it do this?
ECG trace, plotting by measuring electrical activity of the heart. P wave = excitation of atrial walls QRS complex = ventricle walls excitation and T wave = recovery waves of ventricles i.e. diastole
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What is the name of the protein responsible for carrying oxygen around the body and what is it's structure?
Haemoglobin, 4 polypeptide chains with a haem prosthetic group (Fe2+ ion) for each chain with a high affinity for O2. Each chains holds 1 O2 so each Hb holds 4 O2
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What is the relationship between partial pressure of oxygen and haemoglobin's affinity for oxygen
At low O2 partial pressures, Hb does not readily associate with O2 but at higher O2 partial pressures there is a higher chance of O2 combining so it does, making it easier for the next 3 to combine due to a conformational change
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What are the three ways CO2 is transported in the blood
Carried directly in solution, as hydrogen carbonate ions that diffuse into blood plasma or directly combine w/ Hb to form carbaminohaemoglobin
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What does CO2 once it diffuses from the plasma into erythrocytes?
Combines w/ water to form weak acid (carbonic acid) catalysed by carbonic anhydrase, dissociates into H+ and HCO3- ions. HCO3- ions diffuse out of RBCs into plasma
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What happens to the H+ that builds up in RBCs as carbonic acid dissociates into H+ and HCO3-?
As they reduce pH they have to be removed, they associate with haemoglobin to produce haemoglobinic acid, Hb acting as a buffer
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What is foetal haemoglobin like compared to adult haemoglobin?
Higher affinity for O2 as it gets it's blood from the mother which has to supply her own body before it reaches placenta, so can receive O2 more readily
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Briefly describe the Bohr affect
As CO2 forms H2CO3 inside RBCs which dissociates into H+, lowering pH, affects tertiary structure and reduces O2 affinity, meaning it releases O2 into respiring tissues
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Card 2

Front

What features will an effective transport system have?

Back

A fluid/medium to carry nutrients O2 and take away waste, a pump to create P to push fluid, specialised exchange surfaces, tubes/vessels to carry fluid by mass flow, two circuits

Card 3

Front

What is an open circulatory system and what is an example?

Back

Preview of the front of card 3

Card 4

Front

What are some disadvantages of open circulatory systems?

Back

Preview of the front of card 4

Card 5

Front

What two types of closed circulatory systems can you have and whats the difference, with examples?

Back

Preview of the front of card 5
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