mass transport

Created by: ava.scott
Created on: 04-04-16 12:47

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MASS TRANSPORT
- SINGLE PRINCIPLE
  - rate of flowthrough a system= how hard being pushed x *** easy it flows through
  - OHMS LAW
    - Flow= pressure x conductance
      - in physiology, conductance is nearly always altered.
        As PO2 is determined by nature.
    - flow = pressure/ resistance
- consequences of metabolism
  - CH2O + O2 >> CO2 + H2O + ENERGY
    - CO2 is dangerous, because of its acidic tendencies!
      - CO2 + H2O >> HCO3- + H+
    - Lots of energy lost as heat energy, which can be dangerous if allowed to accumulate.
  - For small organism
    - Krogh: radius less than 1mm, diffusion will satisfy
    - oxygen gradient for diffusion needed is equal to the square of the radius of the organism.
      - 2x radius= 4x gradient
  - For large organism
    - Mass transport systems are needed to distribute o2,co2, nutrients and heat.
    - BIG ADVANTAGES
      - Speed
        McMahon and Bonner 1983
        found that the greater the length of an organism
        the greater the maximum speed they could travel
        Important for human hunting; jogging is more efficient that preys stop and start between walk and run.
        the less it cost them to transport 1kg 1km
        
        the greater the mass of an organism
        the less it cost them to transport 1kg 1km
      - strength
      - mechanical efficiency
        McMahon and Bonner 1983
        found that the greater the length of an organism
        the greater the maximum speed they could travel
        Important for human hunting; jogging is more efficient that preys stop and start between walk and run.
        
        the greater the mass of an organism
      - intelligence
- KROGHS ANIMAL PRINCIPLE
  - RENAL FUNCTION
    - giant nephron of kangaroo rat
  - MEMBRANE AND ACTION POTENTIAL
    - giant axon of the squid
  - POLYMERASE CHAIN REACTION
    - Bacteria from hydrothermal vents have heat-resistant polymerase
  - AUDITORY LOCATION
    - owl
  - EXERCISE PHYSIOLOGY
    - humans
  - 1929
- Factors promoting conductance
  - of gas across capillary walls
    - solubility of oxygen in and across membrane
    - extreme thiness of membrane
      - 0.5um (wavelength of visible light!)
    - extremely large surface area
      - 70ml of blood across 80m2 in human lung
    - low velocity of blood in capillaries
      - maintained by recruitment and distension.
  - Content
    - the number of molecules per unit volume
      - will not equilibriate (e.g. between alveoli and blood)
        blood has greater content than air, allowing O2 to diffuse up its concentration gradient
  - partial pressure
    - the summed activity of all oxygen molecules.
      - will equilibriate between two areas
- Volume flow of O2 in humans
  - OVERALL PUSH= Partial pressure gradient of oxygen from atmosphere to mitochondria
    - From lung (convection to diffusion across alveoli)
      - to blood (convection)
        to tissues (diffusion into and across)
    - danger spots: heart and lung
  - OXYGEN CASCADE
    - 150mmHG (PO2) in air
      - 100mmHG (PO2) in alveoli
        95mmHG(PO2) in arterial blood
        drops through systemic capillaries to venous blood, tissues and mitochondria.
  - AIR V WATER
    - O2 Content
      - water has 30x that of water
    - density
      - air has 1/100th of that of water
    - viscosity
      - air has 1/60th of that of water
      - air:blood viscosity
        1/180
        so heart limits exercise (works 180x harder than lungs!)
- Pulmonary conductance
  - achieved by
    - intercostal muscles and diaphragm expanding and elastically recoiling thorax.
  - alveolar PO2 must be less than that on inspired PO2.
    - added O2 (inspiration) removed o2 (metabolism)
      - VO2= (PIO2- PAO2) X VA
        doubling VA will half the difference between PIO2 and PAO2.
  - Lung anatomy
    - spongey
    - mainly air transvered by alveoli membranes
    - alveolar membranes are extremely thin, and contain a single file of RBC
      - exposed to two alveoliar pockets
  - Equilibriation
    - oxygen move svery easily from alveoli to blood, creating a quick equilibriation time
      - blood velocity can increase up to 3x, and equilibiration will still be met
    - HB dissocation curve
      - Enhances PO2 gradients where it is needed
        the greater the PO2 gradient, the greater the oxygen content of the blood
- PRESSURE
  - Blood floes DOWN the pressure gradient
    - biggest drop in?
      - arterioles due to smooth vascular muscle reducing conductance
- REGULATING BLOOD FLOW
  - ORGANS
    - Isolated (unnervated) organs control their own blood flow. the greater the metabolism of tissue, the more relaxed arterioles are.
      - arterioles expandwith metabolic products,
  - HEART
    - Automnaticatically pumps what it receives from summed vascular beds
      - good for heart transplant patients, who have no innervation.
  - Relfex neural repsonses
    - can override local demands if the body demands it
      - e.g. arterial baroreceptors in carotid sinus
        sense blood pressure and miantian is constancy
        
        particularly concerned with cerebral perfusion.
    - always sensory, limb, central processor andmotor limb, all in CNS

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mass transport

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