Haemodynamics

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  • Created by: Labake
  • Created on: 28-12-16 18:04
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  • Haemo-dynamics
    • Dynamic, adjustable networks of blood vessels affected by chemicals
    • Affects cardiac output and workload
      • Sympathetic input (fight or flight)= higher cardiac output
        • Uses Adrenaline hormone and Noradrenaline neuro-transmitter
        • Mechanism
          • Pre-ganglionic neurones release acetylcholine to synapse
            • Activates nicotinic acetylcholine receptors on post-ganglionic neurones
              • Post-ganglionic neurones release noradrenaline
                • Noradrenaline= increase in BP, heart rate, glyco-genolysis, vasodilation to skeletal muscles and GI relaxation
                  • Affects a1, a2, B1 and B2 adreno- receptors
      • Para-sympathetic input= lower cardiac output
    • Vessel Structure
      • Veins= Endothelium, thin smooth muscle and connective tissue
      • Arteries= Endothelium, thick smooth muscle (HIGH PRESSURE) and connective tissue
      • Sympathetic= Increase in smooth muscle tone = vaso-constriction
        • Greater flow resistance in smaller vessels
          • Increased venous pressure and cardiac filling
            • Large veins constrict to fill atria faster and oppose the reduced volume
      • Flow auto-regulation
        • After a pressure surge- stretch gated receptors increase muscle tone to maintain SAME FLOW by increasing resistance
      • Compliance
        • Measure of vessel stretching ease due to pressure
          • High compliance= veins with thin stretchy walls
          • Low compliance = arteries with thick rigid walls

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