Topic 9

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  • Topic 9
    • Hormones
      • Endocrine System
        • Glands which produce hormones and distribute them into the bloodstream
          • attach to receptors
    • Chemical control in Plants
      • Giberellins
        • they act with auxin's to elongate cells in stem for growth; stimulate fruit development; break seed dormancy by activating amylase
      • Auxins
        • cell elongation activates H+ pumps so cell walls stretch; apical dormance auxin produced from main shoot inhibits lateral bud growth; root growth auxin promote this
      • Cytokinins
        • oppose action of auxin in apical dormancy,; promote lateral bud growth; promote cell division in growing points
    • Phytochrome and Photoperiodism
      • long day plants - short night critical, high conc of Pfr
      • short day plants - long night critical, low conc of Pfr
      • Photomorphogenesis - Pfr stimulates germination in some seed, red in daylight stimulates germination by converting Pr into Pfr
    • Mammalian Nervous System
      • Preipheral
        • Voluntary
        • Autonomic
          • Sympathetic
            • Increase
          • Parasympathetic
            • Descrease
      • Central
        • Brain
        • Spinal Cord
    • Central Nervous System
      • Cerebrum - initiates movement
        • Hypothalamus- temperature and osmore regulation
          • Medulla  Oblongata - controls breathing and heart rate
            • Cerebellum - controls balance and coordination of movement
    • Action Potential and Nerves
      • Action Potential
        • Sodium Ions entering during an action potential flow along inside the nerve fibre; the additional positive charge inside reduces the potential differences to the threshold level which opens voltage dependent sodium gates in the membrane
          • the refractory period makes sure the impulse only travels in one direction
      • Myelinated Nerve Fibres
        • Only the node of ranvier can depolarise the impulse jumps between nodes known as salutatory conduction, the myelin sheath decreases impulse times smaller
      • Synapses where impulses have to turn into chemical messenger s to get to the next nerve
      • Nicotine - increases heart rate and blood pressure
        • Lidocaine - an anaesthetic preventing the feeling of pain
          • Cobra Venom- causes paralysis and death
    • Kidney
      • Ornithine cycle produces urea
        • ultra-filtration occurs in the glomerulus, in the filtrate is glucose, water, urea and ions
          • Loop of henle = countercurrrent multiplier
            • Kangaroo rats have a long loof of henle
    • Thermoregulation
      • Ectotherms  - warm up using external sources
        • Endotherms - body heat gained from metabolism
    • Homeostasis
      • Maintenance of a Dynamic Equilibrium
        • pH - hydrogen bonds disrupted charge distribution of active sites change
        • Temp - change of rate of reaction of enzymes can affect stability of proteins
        • Water Potential - affects water content of cells too high causing swelling and bursting too low causes shrinking of cells
        • Positive Feedback
        • Negative Feedback
    • Eye
      • Acuity - the level of detail seen
        • Sensitivity - how little light is needed to cause an impulse
          • Rhodopsin - the light sensitive pigment found in rods that detects light ad initiates action potential (composed of opsin and retinal
            • Bleaching = rhodopsin turning into retinal and opsin
    • Heart
      • adrenaline causes an increase in the heart rate

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