3.1.2 Transport In Animals Flashcards
Explain the need for transport systems in multicellular animals.
Low SA:V
High metabolic rate and demand
Very active
-> diffusion is too slow to reach all cells before they die and not efficient enough to provide and rid of waste products
-> so transport system enable substances to be circulated at faster rate
What occurs in a single circulatory system? Explain an example.
Blood passes through heart once per circulation
E.g. Fish: heart pumps blood to gills for oxygen and then to rest of the body before returning to heart. 2 chambered heart.
What occurs in a double circulatory system? Explain an example.
Blood passes through heart twice per circulation.
E.g. mammals: right side of heart pumps blood to lungs, blood travels from lungs to left side, blood travels from left side to rest of body then back to the heart. 4 chambered heart.
Advantage of double circulatory system.
Maintains a higher blood pressure and average speed of flow, maintaining steep concentration gradient and efficient exchange of materials.
Describe a closed circulatory system and what animals have them.
Blood circulates within blood vessels. Vertebrates have them.
Describe an open circulatory system and which animals have them.
Blood is not contained in blood vessels, it also enters the body cavity. Some invertebrates have them, including insects.
Describe an insects circulatory system and why they can have an open one.
The heart extends along the thorax and abdomen. Haemolymph carries food, nitrogenous waste products and cells for disease defence. One main dorsal vessel, delivers to body cavity.
Gas exchange occurs in the tracheal system so doesn’t matter that steep diffusion gradients aren’t maintained and volume can’t be controlled/directed.
Function of arteries.
Carry blood away from the heart to tissues of the body.
Structure of arteries and how that leads to function.
Elastic fibres: withstand force of blood and stretch to take larger blood volume, stretch and recoil between contractions to even flow.
Endothelium: smooth so friction with blood is reduced, especially with pulse of blood.
Smooth muscle: strong to resist high blood pressure, contracts to reduce blood flow.
Collagen: prevents over-stretching.
Function of arterioles.
Link arteries to capillaries, important in regulating blood flow.
Structure of arterioles and how that leads to function
More smooth muscle but less elastin in walls due to little pulse surge
Can constrict and dilate to control flow of blood into individual organs
Vasoconstriction and vasodilation due to smooth muscle contracting and relaxing
Function of capillaries
Link arteriolar with venues
Exchange substance between tissue cells and blood
Structure of capillaries and how that leads to function
Large SA for diffusion of substances
Larger cross-sectional area than arterioles to slow rate of blood flow, more time for exchange of materials
Walls are one cell thick, thin layer for diffusion
Function of veins
Carry blood away from cells of body to the heart
Mostly carry dexoxygenated blood
Structure of veins and how that leads to function
Walls contain lots of collagen and little elastic fibre
Wide lumen and endothelium so blood flows easily
No pulse and low pressure
One-way valves to prevent back flow
Function of venules
Link capillaries with veins
Structure of venules
Thin walls, little smooth muscle
Components of the blood
Plasma
Erythrocytes
Platelets
White blood cells
Function of plasma
Carries: glucose; amino acids; mineral ions; hormones; large plasma proteins; red blood cells; white blood cells; platelets
Function of platelets
Fragments of large cells
Involved in clotting of blood
Function of RBC
Transport oxygen to cells
How is tissue fluid formed
Plasma proteins in the plasma give blood in capillaries a high solute potential (low water potential) compared to surrounding fluid
Water moves into blood by osmosis (oncotic pressure created)
But, blood has hydrostatic pressure due to blood surges
Hydrostatic pressure at arterial end of capillary is higher than oncotic pressure, tissue fluid is squeezed out of capillaries and fills spaces between cells
At venous end of capillaries, hydrostatic pressure falls as pulse is lost but oncotic pressure is the same and is higher than hydrostatic
Water moves back into capillaries by osmosis
What is tissue fluid
Plasma, without plasma proteins and red blood cells
What is lymph
Less oxygen and fewer nutrients than plasma and tissue fluid
Fatty acids
Describe the structure of the heart
4 chambers: right and left atrium, right and left ventricle
Muscular wall of left side of the heart is thicker than the right
Septum divides left and right sides of the heart
Describe the path of deoxygenated blood through the heart
Deoxygenated blood enters right atrium from vena cava
As blood flows in, pressure builds up until atrio-ventricular (tricuspid) valve opens to let blood into right ventricle
Atrium walls contract and all blood is forced into ventricle, before it contracts the tricuspid valve closes and prevents back flow
Right ventricle contracts and pumps blood through semilunar valves into pulmonary artery
Describe the path of oxygenated blood through the heart
Oxygenated blood from lungs enters left atrium from pulmonary vein
Pressure in atrium builds, bicuspid valve opens and ventricle fills with blood
Atrium contracts and forces all the blood into ventricle
Ventricle contracts (bicuspid valve closes) and pumps blood through semilunar valves into aorta and around the body
Describe the cardiac cycle
Diastole: heart relaxes, atria and ventricles fill with blood, pressure of blood increases as heart fills, minimum pressure in arteries
Systole: atrial systole then ventricular systole, pressure in heart increases dramatically and blood is forced out to lungs/body, maximum pressure in arteries, low pressure and volume in heart
Equation for cardiac output
Heart rate X stroke volume = cardiac output
What does myogenic mean
That the cardiac muscle can generate a heart beat without any other stimulation
Describe how the heart is initiated and coordinated
Wave of excitation begins in sino-atrial node (SAN)
Causes atria to contract, initiating heartbeat
Layer of non-conducting tissue prevents it passing to ventricles
Electrical activity picked up by atrio-ventricular node (AVN)
AVN has a delay (so atria have stopped contracting before ventricles), then stimulates the bundle of His made up of Purkyne fibres
Penetrate through septum between ventricles
Bundle of His splits and conducts wave of excitation to apex of heart
Purkyne fibres spread through walls of ventricles, spread of excitation triggers contraction of ventricles
Contraction of ventricles starts at apex to empty more efficiently
What is tachycardia
When heartbeat is very rapid, over 100bpm
What is bradycardia
Heart rate is slow, under 60bpm
What is an ectopic heartbeat
Extra heartbeats out of rhythm
What’s atrial fibrillation
Abnormal rhythm of the heart, irregular contractions of atria
Oxygen haemoglobin reaction
4 oxygens to one haemoglobin
Binds loosely and reversibly
Oxyhaemoglobin produced
What does partial pressure of oxygen mean
Oxygen concentration
How is oxygen taken up by Hb
Oxygen levels are low in capillaries in lungs, steep concentration gradient between RBCs and alveoli, oxygen diffuses in and binds to Hb
Once one oxygen binds, conformational change occurs and it is easier for next oxygen to bind
This maintains the steep diffusion gradient until all Hb is saturated
How is oxygen released from Hb
In body tissues, concentration of oxygen in cytoplasm lower than in RBCs
Oxygen diffuses out down concentration gradient
First oxygen released, conformational shape which makes it easier to remove rest of the O2
Explain oxygen dissociation curves
Show affinity of Hb for O2
Small change in partial pressure changes saturation significantly
Levels out because all haem groups are bound to oxygen
Small drop in oxygen levels means oxygen is released rapidly, enhanced by low pH in tissues compared to lungs
Explain the Bohr effect
Partial pressure of CO2 rises, Hb gives O2 up easier
Important because in active tissues, O2 given up more readily
And in lungs, oxygen binds easier
What is different about fetal Hb
Has higher affinity for oxygen than adult at each point on dissociation curve, so oxygen is removed from maternal blood when maternal oxygenated and fetal deoxygenated blood run close to each other in the placenta
Equation for transportation of CO2
CO2 + H2O -> H2CO3 -> H+ + HCO3-
Uses enzyme carbonic anhydrase as a catalyst
What are the different ways CO2 can be transported in the blood
5% dissolved in plasma
10-20% forms carbaminohaemoglobin
75-85% converted to hydrogen carbonate ions in cytoplasm of RBCs
Explain the chloride shift
Negatively charged hydrogen carbonate ions diffuse down a concentration gradient out of RBCs, chloride ions diffuse into RBCs, maintaining electrical balance
How is CO2 taken up into RBCs
Steep concentration gradient maintained for CO2 to diffuse from respiring tissues to RBCs
