mod 3

• Water transport from roots to leaves

  1. Water moved from soil to roots via osmosis
  2. H20 moves across symplast route via plasmodesmata (osmosis) and cytoplasm (diffusion) or apoplast route through cell wall and tension
  3. H20 blocked by casparian strip (made of suberin) forcing water to travel through symplast route (filters toxins)
  4. Water moves into endodermis
  5. H20 moves into xylem via osmosis, active transport of root pressure generation
• Ventilation in bony fish:

  1. Mouth opens expanding buccal cavity
  2. Increases volume and decreases pressure
  3. Water moves into buccal cavity down pressure grad
  4. Opercular cavity expands (valves shut)
  5. Increases volume and decreases pressure
  6. Water moves from buccal cavity into opercular cavity across gills
  7. Buccal cavity and opercular cavity constrict decreasing volume and increasing pressure
  8. Water pushes valves open so it leaves to surrounding
• Gas exchange insects:

  1. spiracles open when active to increase O2
  2. Moves down trachea lined with chitin to tracheoles
  3. Tracheoles allow for gaseous exchange to occur
  4. When respiration increases, the lactic acid increase causes wp to decrease so tracheal fluid moves out by osmosis allowing more diffusion to occur
• Ventilation in mammals when active:

  1. External intercostals contract causing ribcage to swing up and out
  2. This increases volume of thorax and decreases pressure
  3. Allows air to be inhaled and for o2 to diffuse into lungs
• Formation of tissue fluid:

  1. High hydrostatic pressure in the capillaries causes water and solutes to move out of the capillaries
  2. large molecules remain in the capillaries lowering the wp
  3. Towards the venule end, osmotic pressure is higher than hydrostatic pressure so water re-enters the capillaries
• The cardiac cycle:

  1. Atrial systole = artia contracts and forces av to open, blood flows to ventricles
  2. Ventricular systole = contraction of ventricles causes AV to close, and semi lunar valves to close allowing blood to leave ventricles
  3. Aortic pressure increases so semi lunar valves close to prevent backflow
  4. Diastole = elastic recoil of the heart lowers pressure inside heart chambers, relaxation
• Heart Contraction:

  1. SAN initiates electrical impulses to start atrial impulses
  2. Electrical impulse flows to AVN which delays the signal, allowing atria to contract and complete blood flow to ventricles fully
  3. Electrical impulse flows to a bundle of his which transmits an impulse from AVN to the apex
  4. Purkinje fibres speed impulses along the ventricles so ventricular systole can occur
• Water moves up a steam via:

  • root pressure = AT transports ions to xylem via the symplast route
  • Low w.p = hydrostatic pressure pushes water up xylem
  • capillary action = water can rise up against gravity
• Translocation:

  Mass loading

  1. companion cell transports H+ ions out via AT so there is high [H+] outside cc
  2. H+ and sucrose enter cc via co-transport and sucrose diffuses in STE via plasmodesmata

  Mass Flow:

  1. High sucrose conc in STE lowers wp
  2. H20 enters STE from xylem via osmosis and increases hydrostatic pressure
  3. Assimliates forced to region of low pressure up and down plant (sink cells)

  Phloem Unloading:

  1. sucrose diffuse from STE into cell sinks
  2. wp in STE increases so h2o goes back to xylem lowering pressure