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neurons 3.docx

3 Pages

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BIOL 1003
Elizabeth Nisbet

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Knowledge Of Transmitters Limited To Acetylcholine And Noradrenaline  Acetylcholine released by o motor neurones on to muscle cells o neurones in the parasympathetic division of the ANS (autonomic nervous system)  Noradrenaline is released in the sympathetic division of the ANS  //The international name for noradrenaline is now norepinephrine The Agonistic And Antagonistic Effects Of Chemicals On Synaptic Transmission  Agonists/antagonists are similar in shape to neurotransmitter o Fit into specific protein receptors of postsynaptic membrane  Agonists → same effect as neurotransmitter o Anatoxin produced by some algae and mimics effect of acetylcholine o Swallowing H2O contaminated with anatoxin causes continuous salvation in mouth  Antagonists block action of neurotransmitter o Prevent neurotransmitter from binding with their receptor sites o High blood pressure can be treated by drugs called β-blockers  Antagonist of adrenaline-receptors on membrane of muscle cells in heart o Curare blocks action of acetylcholine at the junction of nerves and muscles  Useful as a general muscle relaxant in patients undergoing major surgery Spinal Reflexes  Stimuli: Change in internal or external environment  Reflexes → automatic, same, fixed response to a stimulus o Dilating of pupils in dim light o Salvia production when tasting food o Withdrawing part of your body from a painful stimulus  Spinal reflex/Reflex arc is the nervous pathway of a reflex o Reflex arc involves spinal cord rather than brain (quicker action) o May involve brain  Control of muscles in iris  Tension in suspensory ligaments of eye o In-born but can be adapted through learning  Relay neurones carry impulses from reflex arc up ascending tracts in white matter to the brain  New relay neurones form in brain that stimulate motor neurone  They control e.g. muscles that control speech o Rapid and autonomic action o Large number of receptors, sensory, relay and motor neurones involved  Human spinal cord is a hollow tube of nervous tissue  31 pairs of spinal nerves enter and leave spinal cord o Grey matter contains unmyelinated neurones (responsible for grey colour)  Synapse of relay neurone with sensory and motor neurone o White matter contains myelinated neurones (appear white)  Motor and sensory neurones  Is made up of interneuronal axons (tracts) o Sensory neurones enter spinal cord via dorsal root (back)  Their cell bodies are in the dorsal root ganglion o Motor neurones leave the spinal cord via the ventral root (front) The Pathway and Adaptive Value of a Simple Spinal Reflex Involving 3 Neurones  Stimulus causes receptor to generate nerve impulse along SENSORY NEURONE o Moves along dendrite, dorsal root, to the cell body o Cell bod
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