Communication and Homeostasis 

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  • Communication and Homeostasis
    • Maintaining the internal environment of cells
      • Tissue Fluid
      • Excretion
      • pH
      • Temperature
      • Cell Signalling
        • Hormonal System
          • Endocrine - A gland that secretes hormones directly into the blood capillaries
          • Exocrine - A gland that secretes hormones into a duct
          • Slow
          • Long term
        • Neuronal System
          • Short term
          • Rapid Response
    • Homeostasis
      • Keeping internal conditions constant despite external conditions
        • Temperature
        • Glucose
        • pH
        • Carbon Dioxide
        • Water potential of the blood
        • Concentration of ions in the blood
        • Blood pressure
      • Negative Feedback
        • Optimum Conditions
          • Change from Optimum Conditions
            • Effector works to restore optimum conditions
              • Optimum Conditions
                • Change from Optimum Conditions
                  • Effector works to restore optimum conditions
        • Positive Feedback
          • Optimum Conditions
            • Change from Optimum Conditions
              • Effector reacts to increase the change
        • Endotherms
          • Relies on external sources of heat to regulate body temp.
            • Advantages
              • Energy from food can be used for growth
              • Needs to eat less regularly
            • Disadvantages
              • Inactive in colder temperatures
                • Vulnerable
              • May be incapable of activity during winter
        • Endotherms
          • Uses internal sources of heat, heat generated from metabolism, to maintain body temp.
          • Advantages
            • Activity in all weather
            • Ability to inhabit cold habitats
            • Constant body temp.
          • Disadvantages
            • Significant amount of energy from food is used to generate heat energy
            • More food required
            • Less energy from food used for growth
      • The Nervous System
        • Sensory Receptors
          • Sensory Neurones
            • Features of Neurones
              • Motor Neurones
              • Gated ion channels in csm
              • Na+/K+ pumps in csm
              • Potential difference across csm
              • Surrounded by a myelin sheath
              • Contain dendrites connected to other neurones
          • Motor Neurones
          • Relay Neurones
        • Resting Potentials
          • Inside of cell is negative compared to outside
            • 3 Na+ ions out for every 2 K+ ions in
            • Csm is permeable to K+ ions
            • Large organic anions in the neurone
            • -60 mV
            • Polarised
        • Action Potential
          • Depolarisation -50mV
            • Voltage gated Na+ channels open
              • Na+ diffuse into cell down concentration gradient
                • +40 mV
                  • Na+ channels close, K+ channels open
                    • K+ diffuse out of neurone down concentration gradient
                      • Repolarisation
                        • Hyperpolarisation
                          • Refractory Period
                            • Action Potential
                              • Depolarisation -50mV
                                • Voltage gated Na+ channels open
                                  • Na+ diffuse into cell down concentration gradient
                                    • +40 mV
                                      • Na+ channels close, K+ channels open
                                        • K+ diffuse out of neurone down concentration gradient
                                          • Repolarisation
                                            • Hyperpolarisation
                                              • Refractory Period
                                                • Allows cell to recover after AP
                                    • Local Currents
                                      • Na+ diffuse into cell
                                        • High concentration of Na+ at this point
                                          • Na+ diffuse away from point of entry
                                            • Movement of charged particles = local current
                                              • Increased concentration of Na+ cause voltage gated channels to open
                                                • Local Currents
                                                  • Na+ diffuse into cell
                                                    • High concentration of Na+ at this point
                                                      • Na+ diffuse away from point of entry
                                                        • Movement of charged particles = local current
                                                          • Increased concentration of Na+ cause voltage gated channels to open
                              • Allows cell to recover after AP
          • Myelin Sheath
            • Impermeable to ions
              • Saltatory Conduction
                • Nodes of Ranvier
                  • Myelin Sheath
                    • Impermeable to ions
                      • Saltatory Conduction
                        • Nodes of Ranvier
                        • Protects neurone from activity of surrounding neurone
                          • Increased rate of conduction
                      • Schwann Cells
                      • Increased rate of conduction
                • Protects neurone from activity of surrounding neurone
                • Schwann Cells
          • Synapses
            • Action Potential
              • Ca2+ channels open
                • Ca 2+ diffuse into cell
                  • Vesicles containing neurotransmitter move to csm
                    • N.T diffuses across cleft
                      • N.T binds to receptors on postsynaptic membrane
                        • Na+ channels open
                          • Action Potential
                            • Ca2+ channels open
                              • Ca 2+ diffuse into cell
                                • Vesicles containing neurotransmitter move to csm
                                  • N.T diffuses across cleft
                                    • N.T binds to receptors on postsynaptic membrane
                                      • Na+ channels open
              • Cholinergic Synapse
                • Acetlycholine
                  • Acetylcholinesterase
              • Summation
              • Acclimatisation
              • One Direction
              • Reflex Arc

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