Pack 8 Mass Transport

Pack 8 Mass Transport

1. Red Blood Cells

   • Blood is a tissue
   • Adaptions for it's role:
     • No Nucleus = more space for haemoglobin
     • Bi-concave = higher SA:vol ratio
     • Flexible plasma membrane for squeezing
     • Selectively permeable
     • Contains haemoglobin

2. Haemoglobin

   • Transport of O2
     • Oxygen diffuses across the membrane of the red blood cwell and combines with Hb to form HbO8
     • Each four of the 4 iron containing haem groups picks up a molecule of oxygen, with a loose attachment
     • Oxygen dissociation curves
       • Haemoglobin has a high affinity for oxygen
       • Factors that must be kept the same:
         • Temp.
           • pH
             • Pressure
               • Vol. of blood
                 • Surface area
                   • Blood from the same person
       • Lungs are at the top, tissues are in the middle
       • Why is it S shaped?
         • Allostery. When an oxygen molecule attached to the iron in the first haem group, it causes the haemoglobin to change shape
           • The change in shape exposes the second iron and allows it to take up oxygen faster, this repeats for 3rd and 4th
       • The Bohr effect
         • CO2 has to be taken into consideration
         • If the curve moves to the left, there is a higher affinity and vice versa
           • Animals that don't have much oxygen available so they have a high affinity for oxygen
             • Where the O2 conc. is L-ow the ODC moves to the L-eft
               • Where the organism has a high R-espiration rate, the ODC moves to the R-ight
         • The Bohr effect makes HbO8 less efficient at holding oxygen
           • 1. Increase in exercise
             • 2.Increase in respiration
               • 3. Increase in muscle contraction and therefore ATP
                 • 4. Increase in carbon dioxide
                   • 5. CO2 is dissolved in blood
                     • 6. pH of blood lowers and denatures proteins
                       • 7. So a lower affinity for oxygen causes Hb to drop oxygen and pick up H+ ions
     • When oxygen picks up oxygen it is loaded
       • When it drops off oxygen in is called unloaded
   • Structure:
     • Quaternary structure
     • Conjugated protein
     • It's prosthetic group is Fe2+

3. Circulatory system of a mammal

   • Main features of a mass transport system:
     • 1. Suitable medium to carry materials
       • 2. A form of mass transport
         • 3. Closed system of tubular vessels
           • 4. A mechanism to move it
   • Requirements for a mass transport system:
     • 1. Mechanism to maintain mass flow in one direction
       • 2. A mean of controlling the flow to suit needs of organisms
         • 3. A mechanism for mass flow of water or gases
   • Mass Flow:
     • Movement together
     • At the same speed
     • In the same direction
     • Over large distances
     • Due to pressure differences
   • A double circulatory system passes through the heart twice in one circuit of the body
     • Advantages:
       • Oxygenated and deoxygenated blood don't mix
       • Gas exchange is maximised
       • Separate circuits can operate at different pressures
     • Atrio-ventricular valves between atrium and ventricle
       • Semi-lunar valves between ventricle and aorta/artery
   • Structure of the heart
     • Lies in the thorax with its apex tilted left
     • Covered by coelomic epithelium (pericardium)
     • Vena Cava enters right atrium and brings blood from the body
       • Pulmonary vein in the left atrium and bring blood from lungs
     • Left ventricle more muscular than right ventricle so it can give an increased pressure around the body
     • Tendons prevent atrio-ventricular valves turning inside out
     • Valves prevent backflow
     • Endothelium reduces friction
   • Risk factors of cardiovascular disease
     • A risk factor is something that increases the risk of disease
     • Smoking:
       • 2-6 time more likely to get disease
       • Carbon monoxide irreversible combines with Hb, less oxygen available increases blood pressure
       • Nicotine - stimulates production of adrenaline, increases blood pressure
     • High Blood pressure
       • Higher pressure in the arteries - heart has to work harder to pump blood into them
         • Aneurysm is more likely
       • To resist high pressure, the walls become thickened which restricts blood flow
     • Blood Cholesterol
       • High density lipoproteins
         • Moves cholesterol from tissue to liver for excretion
       • Low density lipoproteins
         • Moves cholesterol from liver to tissue
           • Can lead to atheroma
     • Diet
       • High levels of salt = raised blood pressure
       • High levels of saturated fats = more LD lipoproteins, so increase in cholesterol

4. The Cardiac Cycle

   • Diastole
     • Atria and ventricles relax and blood enters from the vena cava
   • Atrial systole
     • Both atria contract together, volume decreases, pressure increases, valves open blood moves into ventricle
   • Ventricular Systole
     • Both ventricles contract together whilst the atria relax, pressure increases above atria, atrioventricular valves close, semi-lunar valves open blood moves out
   • Valves will only open when the volume decreases and the pressure increases

5. Valves:

   • Prevent back flow of blood
   • Atrioventricular valves:
     • From atria to ventricle
       • High pressure against low pressure
         • Valves open
     • Semi lunar valves
       • Ventricle to aorta/vein
         • High pressure against low pressure
           • Valves open
       • Aorta/vein to ventricle
         • Low pressure against high pressure
           • Valves close
     • From ventricle to atria
       • Low pressure against high pressure
         • Valves close
   • Pocket valves are found in your veins, when veins squeezed by muscles it pushes blood to the heart

6. Cardiac Output

   • Cardiac output (dm^3min^-1) = Stroke volume (dm^3) x Heart rate (beats min^-1)

7. Blood Vessels and Their functions

   • Artery (and arterioles):
     • Tough outer later
       • Resists pressure
     • Thick muscle layer
     • Thick elastic layer
     • Thin inner lining
     • Narrow lumen
   • Veins:
     • Thin tough outer layer
     • Thin muscle layer
     • Thin inner lining
     • Wide lumen
   • Capillaries
     • Thin inner lining
     • Lumen
   • Layer and functions:
     • Tough fibrous outer layer
       • Resists pressure changes
     • Muscle layer
       • Contracts for controlling blood flow
     • Elastic layer
       • Stretch and recoil, even out blood pressure
     • Thin inner lining
       • Smooth to reduce friction
     • Lumen
       • Allows blood flow

8. Tissue Fluid

   • As the capillaries leak, small molecules and ions are forced out and form tissue fluid
   • Hydrostatic pressure forces fluid out of the capillary
     • Water potential draws the fluid back in
       • If water potential>hydrostatic pressure, tissue fluid moves in
     • If hydrostatic pressure>water potential, tissue fluid moves outward
   • Fluid that surrounds the cells of the body, it's composition is similar to blood plasma except it lacks proteins. It supplies nutrients to cells and removes waste products
   • Tissue fluid and the Lymph vessel
     • Not all tissue fluid has time to get back into the capillaries
       • Any excess tissue fluid absorbed by Lymph capillaries and reabsorbed into the venule by osmosis

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