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HUMAN NERVOUS SYSTEM - Coggle Diagram
HUMAN NERVOUS SYSTEM
THE NEURONE
MAIN TYPES
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MOTOR (EFFERENT) NEURONE
FROM INTERNEURONE TO EFFECTOR (MUSCLE, GLAND)
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THE NERVE IMPULSE
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PROCESS
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NEURONE MEMBRANE IS POLARIZED (INTERIOR +ve CHARGED, EXTERIOR -ve CHARGED)
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WHEN STIMULUS, NEURONE MEMBRANE BECOMES MORE PERMEABLE TO Na+ THAN K+
Na+ PASS THROUGH MEMBRANE, INSIDE BECOMES +ve OUTSIDE BECOMES -ve
NEURONE IS DEPOLARIZED, ACTION POTENTIAL IS CREATED
ACTION POTENTIAL LASTS FOR 2 MS, Na+ STOPS FLOWING OUT & K+ FLOWS OUT
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CHARACTERISTICS
ALL OR NOTHING LAW
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SIZE OF STIMULUS AFFECTS FREQUENCY OF IMPULSE, NOT SIZE NOR SPEED OF IMPULSE
REFRACTORY PERIOD
FOLLOWING AN IMPULSE, FURTHER STIMULUS CANNOT GENERATE A SECOND IMPULSE FOR AT LEAST 1 MS
ABSOLUTE REFRACTORY
LASTS FOR 1 MS, NEW IMPULSE CANNOT BE PROPAGATED
RELATIVE REFRACTORY
LASTS FOR 5 MS, NEW IMPULSE CAN PROPAGATE IF STIMULUS IS MORE INTENSE THAN NORMAL THRESHOLD
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THE SYNAPSE
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SYNAPTIC KNOB CONTAINS LOTS OF MITOCHONDRIA & SYNAPTIC VESICLES CONTAINING NEUROTRANSMITTERS (EG. ACETYLCHOLINE, NORADRENALINE)
MECHANISM
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PRESYNAPTIC MEMBRANE BECOMES MORE PERMEABLE TO Ca2+, Ca2+ FLOW INTO SYNAPTIC KNOB
CAUSES SYNAPTIC VESICLES TO FUSE WITH PRESYNAPTIC MEMBRANE, DISCHARGING NEUROTRANSMITTER INTO SYNAPTIC CLEFT
NEUROTRANSMITTER DIFFUSES ACROSS SYNAPTIC CLEFT, BINDS WITH RECEPTOR PROTEINS ON POSTSYNAPTIC CLEFT
POSTSYNAPTIC MEMBRANE BECOMES MORE PERMEABLE TO Na+, DEPOLARISES POSTSYNAPTIC MEMBRANE
IMPULSE IS GENERATED, TRAVELS DOWN AXON OF POSTSYNAPTIC MEMBRANE
ACETYLCHOLINE IS HYDROLYSED BY ACETYLCHOLINESTERASE,
NORADRENALINE IS HYDROLYSED BY MONOAMONIOXIDASE
HYDROLYSED MOLECULES REABSORBED INTO SYNAPTIC KNOB, RESYNTHESISED AND REUSED AS NEUROTRANSMITTERS