Transport in Animals Flashcards
Give 5 reasons why specialist transport systems are needed
1) Metabolic demands of multicellular organisms are high
2) SA:V gets smaller as multicellular organisms get bigger
3) Hormones and enzymes need to be transported around the body
4) Food digested needs to be transported
5) Waste products of metabolism needs to be removed from cells and transported to excretory organisms
What are 3 key features of a circulatory system?
A liquid transport medium
Vessels
Pumping mechanism
What is a mass transport system?
Substances being transported in a mass of fluid with a mechanical mechanism for moving the fluid
What is an open body cavity called?
Haemocoel
Explain movement of transport medium in an open circulatory system
Transport medium pumped straight from heart into haemocoel
Transport medium under low pressure and comes into direct contact with cells
Exchange occurs
Transport medium returns to heart via open ended vessel
Where are open ended circulatory systems found?
Invertebrate animals
What is insect blood called?
Haemolymph
What does haemolymph carry and not carry?
Carries food, nitrogenous waste and cells involved with defence against disease
Explain the movement of blood in a closed circulatory system
Heart pumps blood around the body under pressure and quickly
Blood returns directly to heart
Substances leave and enter blood by diffusion through walls of blood vessels
What is a single circulatory system?
Blood travels through heart once for each complete circulation of the body
What does blood pass through before returning to heart in single closed circulatory system? What is the effect of this?
2 sets of capillaries, 1st exchanges O2 and CO2, 2nd different substances
Result of this= blood pressure drops significantly and so returns to heart slowly
What is a double circulatory system?
Blood pumps through heart twice for each complete circulation of the body
What are the 2 separate circulations of blood in a double system?
Blood from heart to lungs to pick up O2 and offload CO2, returns to heart
Heart to body
What do elastic fibres contain and do?
Composed of elastin
Stretch and recoil, providing vessel walls with flexibility
What does smooth muscle do?
Contracts or relaxes affecting size of lumen
What does collagen do?
Provides structural support to maintain shape and volume of the vessel
What do arteries carry? Give the 2 exceptions
Oxygenated blood away from the heart
Except: pulmonary artery (heart to lungs) and umbilical artery(foetus-placenta) which carries deoxygenated blood
What is the role of elastic fibres within the heart?
Withstand force of heart
Stretch to take larger volume
Recoil between contractions
Why is it important for arteries to recoil between contractions of heart?
To even out surges of blood and give a continuous flow
What do arterioles contain? Why?
Smooth muscle, no pulse but need to constrict and dilate to effect flow to organs
How do substances pass in and out of the capillaries?
Gaps between endothelial cells
Through capillary walls
Give 3 ways capillaries are adapted for their roles
Large surface area for diffusion
Total cross sectional area is smaller than the artery supplying it so flow is decreased, increasing time for exchange
Walls are single endothelial cell thick
What do veins carry? Give 2 exceptions
Veins carry deoxygenated blood back towards the heart
Exceptions: pulmonary vein(lungs-heart) and umbilical vein(placenta-foetus) which carry oxygenated blood
What is the structure of a vein?
Lots of collagen
Limited elastic fibre
Wide lumen
Smooth thin lining
What are the 3 major adaptions of veins to go against gravity?
One way valves to prevent backflow
Run through major muscles so when they contract the blood is forced up too
Breathing movements to force blood towards the heart
What does plasma contain?
Glucose
Amino acids
Hormones
Plasma Proteins
What is the role of albumin?
Maintains osmotic pressure of the blood
What is the role of fibrinogen?
Important in blood clotting
What is the role of globulins?
Transport and the immune system
What are platelets and what is their role?
Fragments of megakaryocytes found in red bone marrow
Involved in blood clotting
What 7 things does the blood have to transport?
Oxygen and CO2 to and from cells
Digested food from small intestine
Nitrogenous waste products from cells to excretory organisms
Chemical messages
Food molecules from storage compounds
Platelets to damaged areas
Cells and antibodies involved with the immune response
What are the 2 other roles of blood apart from transport?
Maintain steady body temperature
Minimises pH changes
How is tissue fluid formed?
Hydrostatic pressure creates a high pressure at arterial end
Water and small molecules forced out (not plasma proteins as they’re too big) through fenestrations in capillaries as hydrostatic pressure is greater than oncotic pressure
Gathers in interstitial space
What is oncotic pressure?
Tendency of water to move into the blood by osmosis
When does tissue fluid return to the blood? Why?
Venous end of capillaries
Oncotic pressure > hydrostatic pressure so 90% tissue fluid returns
What is lymph?
10% of fluid that doesn’t return with a high proportion of fatty acids and urea.
Where is lymph contained?
System of blind ended tubes called lymph capillaries which join to form larger vessels, returns to blood under subclavian veins
What do lymph nodes do?
Intercept bacteria and other debris from lymph
Give the equation of oxygen binding reversibly with haemoglobin
Hb +4O2 = Hb(O2)4
What is positive cooperativity?
Once one oxygen molecule binds to a haem group it causes a conformational change that makes it easier for next oxygen to bind
What does an oxygen dissociation curve plot?
Percentage saturation of haemoglobin against partial pressure of oxygen
What is the shape of an oxygen dissociation curve? Why?
Sigmoidal
High partial pressures-flattens as all haem groups bound to oxygen
Low partial pressures- steep due to positive cooperativity
Explain the Bohr Effect
As partial pressure of carbon dioxide rises, haemoglobin gives up oxygen more easily
Why is the Bohr Effect important?
Active Tissues with high proportion of haemoglobin, CO2 given up easily
Lungs where CO2 concentration is low oxygen binds easily
How is fetal haemoglobin adapted?
Has a higher affinity for oxygen than mothers so oxygen passes across the placenta from mother into the fetus
What are the 3 ways that carbon dioxide is carried in the blood?
Dissolved in plasma (5%)
Carbaminohaemoglobin (20%)
Hydrogen carbonate ions (75%)
Explain process of carbon dioxide converting to hydrogen carbonate ions
Carbon dioxide +water- carbonic anhydrase- hydrogen ions and hydrogen carbonate ions
Which enzyme catalyses the formation of hydrogen carbonate ions?
Carbonic anhydrase
Explain the chloride shift
Hydrogen carbonate ions move out of erythrocytes
Negatively charged chloride ions move into erythrocyte to maintain charge balance
What happens when the blood reaches the lungs where there is little CO2?
Carbonic anhydrase catalyses reverse reaction
Carbon dioxide and water formed
Hydrogen carbonate ions move back into erythrocytes and react with H+ ions to form more carbonic acid
CO2 diffuses out of lungs
Chloride ions move back to plasma
How does haemoglobin impact movement of CO2?
Prevents pH changes by absorbing free H+ions to form haemoglobinic acid
What is the heart made from?
Cardiac muscle which contracts and relaxes in a regular rhythm
What supplies the cardiac muscle with oxygen?
Coronary arteries
What is the heart surrounded by? Why?
Inelastic pericardial membranes which prevent the heart from over distending with blood
What is the role of the tendinous cords?
To prevent the valves from being turned inside out by pressure exerted when ventricle contracts
Explain what happens on the right side of the heart
Blood enters right atrium from vena cava
Pressure builds up
Atrioventricular valve opens
Blood passes into right ventricle
Atrium and ventricle filled, atria contracts forcing all blood into ventricle
Atrioventricular valve shuts to prevent backflow, ventricle starts to contract
Right ventricle contracts forcing blood out of semi lunar valves into pulmonary artery to lungs
Semi lunar valves shut
Explain what happens on the left side of the heart
Blood enters from pulmonary vein Pressure builds in left atrium Bicuspid valve opens Left ventricle fills Left atria contracts Blood forced into ventricle Bicuspid valve shuts Ventricle contracts Forces blood through semilunar valves into aorta
Why is the left side of the heart thicker?
Has to generate enough force to push blood around the body rather than just to the lungs which has more resistance
What is the septum? What is its role?
Inner dividing wall of the heart which prevents mixing of deoxygenated and oxygenated blood
What is the cardiac cycle?
The events of a single heartbeat
How long does the cardiac cycle last in humans?
0.8 seconds
What happens in diastole?
Heart relaxes
Atria and ventricles fill with blood
Volume and pressure increase
Pressure in arteries at minimum
What happens in systole?
Atria and ventricles contract
Pressure inside heart increases dramatically
Explain the changes in aortic pressure throughout the cardiac cycle
Rises when ventricles contract
Gradually falls
Recoil action at end of contraction causes small rise
Explain changes in atrial pressure throughout the cardiac cycle
Always relatively low
Increases when atria contracts
Falls when atrioventricular valve shuts and atria relaxes
Gradual increase in pressure when ventricles are contracting
Falls when atrioventricular valve opens in diastole
Explain changes in ventricular pressure during the cardiac cycle
Low to begin
Increases as ventricles fill with blood
Left atrioventricular valve closes, pressure rises dramatically during contraction
Pressures rises above aorta, forcing blood out
Pressure falls as ventricles relax
Explain change in ventricular volume during the cardiac cycle
Rises as atria contract
Falls suddenly when blood forced into aorta
Volume increases again during diastole
What sound does the heart make?
Lub-dub
What does the lub-dub sound signify?
Lub= atrioventricular valves shutting as ventricles contract Dub= blackflow closes semilunar valves in aorta and pulmonary artery as ventricles relax
What does it mean for the cardiac muscle to be ‘myogenic’?
Have its own intrinsic rhythm
Explain the process of a heartbeat
A wave of excitation begins at sino-atrial node
Causes atria to contract
Electrical activity picked up by atrioventricular node
AVN imposes slight delay
Stimulates ‘Bundle of His’
Wave passed through purkyne fibres which penetrate septum
Wave reaches apex of heart
Purkyne fibres spread through ventricle and wave causes contraction from apex upwards
Why does the AVN impose a slight delay?
To make sure that the atria have stopped contracting before the ventricles start contracting
Why does contraction start at the apex?
To allow for more efficient emptying of the ventricles
What does an electrocardiodiagram measure?
Electrical activity of the heart by detecting differences in your skin
What is tachycardia and when does it occur?
When the heartbeat is very rapid, over 100bpm
Occurs normally during exercise, fever, frightened or angry
How is serious tachycardia treated?
Medication or surgery to maintain electrical control of the heart
What is bradycardia and when does it occur?
When the heartbeat is very slow, below 60bpm, occurs when extremely fit
How is serious bradycardia treated?
Artificial pacemaker
What is an ectopic heartbeat?
An extra heartbeat out of the normal rhythm
What happens during atrial fibrillation?
Arrhythmia
Rapid electrical impulses in atria
Contract very fast
Heart doesn’t pump effectively as ventricle doesn’t fill
