COORDINATION

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  • Coordination
    • The nervous system
      • what does it do?
        • to detect a change in the environment.
        • to initiate a response.
      • The central nervous system
        • the brain and spinal cord
        • processes and initiates a response
      • the peripheral nervous system
        • pairs of neurones that stem from the spinal cord.
          • e.g. sensory and motor neurones.
        • they detect stimuli and connect  top an effector
    • STIMULI
      • a detectable change in the internal or external environment.
      • Reflex arc
        • the basis of involuntary actions fro protection
        • closely associated with conscious neural pathways.
          • via ascending and descending tracts in the spinal cord.
      • Hydra
        • simple organism
        • small number of stimuli
          • so a small number of effectors
            • EFECTORS ARE MUSCLES OR GLANDS
        • response is slow because
          • transmission is multi-directional
          • nervre net system
      • Picked up by receptor neurons in sensitive cells in the skin or high specialized organs such as the eye.
    • SPINAL CORD PHYSIOLOGY
      • Dorsal root ganglion
        • cell body within the dorsal root that receives information and sends it to the spinal cord
      • dorsal root
        • top of diagram
      • ventral root
        • bottom of diagram (or nearer to belly button)
      • white matter
        • contains mylelinated axons
      • grey matter
        • contains darkly staining cell bodies
      • central canal
        • fluid filled space
      • meninges
        • outside layers of the spinal cord
      • sensory neurone
        • enters spinal cord via the dorsal root
      • motor neurone
        • leaves via the ventral root and is connected to effectors
      • relay neurone
        • within the grey matter, connecting a sensory neurone and motor neurone
      • effector
        • muscle or gland
    • MAMMALIAN NEURONE
      • Physiology
        • dendrites
          • recieve impulse from many axons
        • dendron
          • carries information to the cell body
        • cell body
          • contains granular cytoplasm and nucleus.
          • ribosomes associated in Nissl granules
            • concerned with synthesis of neurotransmitters
        • nucleus
          • contains genetic information to code for neurotransmitters
        • axon
          • carries genetic information away from the cell body.
        • myelin sheath
          • fatty layer around neurone made from Schwann cells
        • nodes of ranvier
          • gaps in the myelin sheath allowing saltatory conduction.
      • SENSORY
        • cell body in middle
      • RELAY
        • unmyleinated
        • within grey matter
      • MOTOR
        • Cell body within dendrites
    • RESTING POTENTIAL
      • measured using
        • cathode ray oscilloscopes
        • microelectrodes
        • across giant axons from quid
      • usually negative values
        • -70mv
        • said to be polarised
        • inside of axon has a negative charge.
      • MAINTENANCE
        • pumps
          • sodium potassium pump
          • 2 K+ in for every 3Na+ out
        • channels
          • potassium channels remain open
            • so these ions can diiffuse out
          • sodium channels are closed
            • so these ions cannot move in
        • COO- groups and proteins
          • these keep the cytoplasm  of the axon negative.
        • Overall
          • 100x more permeable to K+ than Na+
            • K+ is high is concentration
              • so these positive ions diffuse out, polarising the membrane.
    • NERVE IMPULSE
      • Action potential
        • A change in the permability of Na+ in the membrane resulting in a voltage being generated.
      • DEPOLARISATION
        • suitable stimulus causes Na+ channels to open.
          • there is an influx of Na+ ions.
            • Creating a positive depolarisation of +40mv
        • REPOLARISATION
          • K+ ions flood our rapidly
            • HYPERPOLARISATION
              • there is an overshoot of K+ ions
                • the membrabe is -90mv
              • REFRACTORY PERIOD
                • The sodium- potassium pump restores ionic balance
                • importance of refractory period
                  • limits frequency of action potential generation.
                  • stops merging of impulses.
                  • undirectional impulse.
      • All or nothing law
        • The intensity of the stimulus
          • does not effect the size of the action potential
        • if the stimulus does not reach the threshold, a action potential will not be generated.
    • nerve transmission
      • PROPOGATION
        • depolarization is propagated across the membrane
          • by local currents stimulating the next area to become depolarised.
            • and repolarisation occurring right behind.
      • Myelination
        • speeds up transmission by
          • increasing the distance of which a local current can induce depolarisation.
            • as it jumps from node of ranvier to node.
              • SALTATORY CONDUCTION
      • the size of the axon also effects the speed of transmission.
        • the larger the diameter of the axon, the greater the velocity of impulse.
    • SYNAPSE
      • Physiology
        • Mitochondria
          • energy used to regenerate neurotransmitters
        • synaptic  knob
        • presynaptic membrane
        • synaptic vesicles
        • cleft
        • postsynaptic membrane
      • Transmission
        • chemical rather than electrical
        • depolarisation reaches the synaptic knob
          • causing Ca+ channels to open and a influx of Ca+ ions
            • causing synaptic vesicles to fuse with the presynaptic membrane and empty contents into cleft
              • neurotransmitter diffuse across the cleft and bind with receptor sites.
                • when both receptorsites per sodium gated ion is filled, the gate opens.
                  • causing an influx of sodium ions into the post-synaptic membrane
                    • depolarising the next dendron!
        • Neurotransmitters
          • noradrenaline and acetylcholine
            • acetylcholine breaks into
              • ethanoic acid
              • acetyl
              • by cholinesterase
          • broken down in teh synaptic cleft and diffuse back into pre-synaptic knob
            • ATP is needed to join components together and package them into esicles
              • this prevents
                • merging of impulses
                • limits the effect of an action potential
          • ORGANOPHOSPHATE FERTILISERS
            • imitate action of neurotramsitter
              • keeping sodium gated ions open and prolonging effect of impulse
            • could also inhibit enzyme action e.g. cholinesterase
            • at a neuromuscular junction-repeated firings could lead to a twitch
        • Functions
          • act s as a juntion- vesicles only in pre-synaptic membrane
            • one direction impulse
          • filters out low level stimli
            • protects from over stimulation
          • conveys impulse from one neurone to the next

Comments

8cburton

can you please get rid of your by4 stuff its just really confusing me and unthoughful of you. we did the exam 3 days ago goddamit stop holding onto things you have lost and move on

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