Transport in animals:

• Need for transport systems:

  High metabolic demands

  • produce lots of waste and need lots of materials, so diffusion over long distances is not enough to supply the quantities needed

  SA:V

  small SA:V in large multicellular organisms, so diffusion distances get bigger and the amount of substances which need to be diffused across also increases

  Molecules are made in one place but used in another

  hormones, enzymes

  Food is digested then moved for use elsewhere

  • glucose -> every cell for respiration

  Waste products need removing by excretory organs
• Different types of circulatory systems:

  Circulatory systems

  • carry useful reactants and products + waste products and hormones around the body
  • Have a liquid transport medium (blood)
  • Have essential vessels that the transport medium moves through
  • Have a pumping mechanism
• Different types of circulatory systems:

  Open

  • very few vessels
  • Transport medium moved straight from heart to body cavity (cavity= haemocoel)
  • Transport medium is under low pressure in body cavity
  • Transport medium comes into direct contact with tissues and is exchanged
  • Transport medium returns to heart through open ended vessel
  • Eg in insects
• Different types of circulatory systems:

  Closed

  • blood is enclosed in vessels and does not directly contact the cells of the body
  • Heart pumps blood around body at high pressure and returns to the heart
  • Substances leave and enter the blood by diffusion through the walls of the blood vessels
  • Vessels can widen/ narrow to change the blood supply to an area
• Different types of circulatory systems:

  Single

  • blood flows from heart to body to heart — travels only once

  Double

  • blood passes through heart twice in a complete circuit
  • heart -> lungs -> heart to body
• Structure:

  Arteries

  • elastic fibres- withstand force of blood being pushed out, stretch to take in larger blood volume. Recoil between pumps of heart
  • Smooth muscle- streghth + contract and relax to increase/decrease blood flow
  • Collagen - protect
  • Narrow lumen- maintain high pressure

  Arterioles

  • more muscular - contract to cut off blood flow to specific organs so more blood can reach muscles
  • Less elastic fibres
• Structure:

  Capillaries

  • 1 cell thick - short diffusion pathway
  • Large SA:V

  Venules

  • large lumen, few elastic fibres
  • No muscular layer due to low pressure movement

  Veins

  • very low pressure blood
  • Thin muscular layer
  • Lots of collagen, very little elastin, wide lumen, smooth thin lining
  • Have valves to prevent back flow
• Formation of tissue fluid from plasma:

  When blood passes through capillaries, some plasma leaks out of the gaps in the capillary to surround the cells of the body - leads to tissue fluid formation

  • Tissue fluid- contains fewer proteins than plasma as this is too large to fit through the gaps in capillary walls
  • Exchange of substances between cells and blood happens via tissue fluid
• Formation of tissue fluid from plasma:

  Tissue Fluid Formation

  • hydrostatic pressure - pressure exerted by a fluid (blood) - blood pressure
  • Oncotic pressure- the osmotic pressure exerted by plasma proteins within a blood vessel (plasma proteins lower the water potential in he blood vessel, so water moves into the blood vessel by osmosis)
• Tissue fluid from plasma:

  Lymph

  • some tissue fluid doesn't return to capillaries, but drains into lymph capillaries becoming lymph
  • Lymph has less O2 and fewer nutrients. It also contains fatty acids which enter from villi in small intestine
  • Lymph moves due to contraction of body muscles (movement), has veins to prevent back flow.
  • Lymph nodes along lymph vessels have a build up of lymphocytes when necessary and produce antibodies
  • Lymph nodes intercept bacteria etc which are digested by lymphocytes
  • Swollen lymph nodes = sign of infection
• Tissue fluid formation from plasma:

  Arteriole end:

  • High hydrostatic pressure (~4.6)
  • Oncotic pressure ~3.3
  • Hydrostatic > Oncotic
  • Net flow of fluid out of capillary - tissue fluid forms

  Venous end:

  • Lower hydrostatic pressure (~2.3)
  • Oncotic pressure ~3.3
  • Hydrostatic < Oncotic
  • Net flow of fluid in to capillary - tissue fluid returns in
• Cardiac cycle: right side d

  Systole- contract

  • when muscles contract, volume in chamber decreases, so pressure increases
  • When pressure behind valve is greater than pressure in front of valves, valve opens

  Artriole systole

  • deoxy blood enters the right atrium through the vena cava
  • atria contract, volume decreases, pressure increases
  • increase in pressure causes AV valves to open
  • blood forced into ventricles
  • causes pressure in ventricles to increase slightly as they take in an increased volume of blood
• Cardiac cycle: RIGHT SIDE

  Ventricular diastole

  • ventricles are relaxed, fill with blood

  Ventricular systole

  • ventricular walls contract, volume decreases, pressure increases
  • pressure in front of AV valve is greater than pressure behind AV valve, so AV valve closes, preventing the back flow of blood
  • Semi lunar valves open — deoxygenated blood forced into the pulmonary artery
  • As this happens atrial diastole occurs, so atriums fill with blood
• Cardiac cycle: LEFT SIDE

  AT the same time:

  • Oxygenated blood from the pulmonary vein enters left atrium
  • Pressure increases
  • AV valves open allowing blood to flow into the left ventricles.
  • When both the atrium and ventricle is full, atrium contracts forcing all the oxygenated blood into the left ventricle
  • Left ventricles contracts pumping blood through the semi luna vales into the aorta and AV are shut to prevent back flow.
• Cardiac output:

  Heart rate- heart beats per minute

  Stroke volume- the volume of blood pumped out of the left ventricle during 1 cardiac cycle

  Cardiac output = heart rate x stroke
• Heart action initiation and coordinated:

  Myogenic - the heart beats without an external stimulus

  Sinoatrial node (SAN)

  1. SAN Initiates a wave of depolarisation causing the atria to contract
  2. Depolarisation is carried to atrioventricular node (AVN) - delays the stimulation
  3. AVN stimulated and passes stimulation along the bundle of his (bundle of purkyne fibres)
  4. Bundle of his penetrates through the septum
  5. Bundle of his splits into 2, takes wave of excitation to the apex of heart
  6. Excitation spreads through apex and muscles contract from bottom
• EEG traces:

  P wave- atriole systole

  QRS- ventricular systole

  T wave- ventricular diastole

  • used in diagnostics

  1. Tachycardia:

  • too fast
  • Over 100 bpm

  2. Bradycardia

  • too slow

  • Below 60 bpm

  3.Ectopic heartbeat

  • beats too early then followed by a pause

  4.Atrial fibrillation

  • abnormal rhythm
  • Can be fatal
• Role of haemoglobin when transporting O2:

  When the first O2 binds, the haemoglobin molecules undergoes a conformational change, making it easier for each successive O2 to bind - cooperative binding
• Role of haemoglobin when transporting CO2:


  3 ways of transport

  1. some CO2 dissolves in the blood plasma and is transported in solution
  2. CO2 binds to haemoglobin -> carbaminohaemoglobin
  3. Most CO2 is transported as hydrogen carbonate ions (HCO3-)
• Role of haemoglobin when transporting CO2:

  Formation of hydrogen carbonate ions

  • CO2 diffuses into red blood cells
  • CO2 combines with H2O to form H2CO3 (catalysed by carbonic anhydrase)
  • CO2 + H2O ,<=> H2CO3
  • H2CO3 dissociates readily

  H2CO3 <=> HCO3- + H+

  • H ions combine with haemoglobin -> haemoglobin acid, so the H+ ions don't lower the pH of the red blood cell - so haemoglobin acts as a buffer
  • HCO- (ions) diffuse out of the RBCs into plasma, where they are transported in solution
• Role of haemoglobin when transporting CO2:

  Chloride shift

  • when H2CO3 -> H+ + HCO3- (carbonic anhydrase)
  • HCO3- are transported out of the RBCs and Cl- move into the RBC
  • Cl- moving in prevents the RBCs from becoming positively charged due toH+ building up
• Oxygen dissociation curve:

  Difficult for the 1st O2 to binds, so binding occurs slowly- small gradient at start off graph

  • 1st O2 binds, haemoglobin changes shape so it is easier for next haemoglobin to bind. Therefore speed of binding increases - steep curve in middle of graph. Cooperative binding

  • at end, there is a shortage of remaining binding sites so it is difficult for final O2 to bind, so graph levels off
• Oxygen dissociation curve:

  • at low pO2 haemoglobin has low affinity for O2- therefore does not pick upO2 from oxygen depleted cells (eg respiring cells).
  • At medium pO2- oxygen binds easily to haemoglobin and becomes saturated quickly
  • At high pO2- haemoglobin has high affinity for O2 as most haem groups already hold an O2 molecule