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What is a synapse? 6.5.6

What is a synapse? 6.5.6. A junction that permits a neuron to pass a signal, electrical or chemical, to another cell Electrical Synapses Two neurons are close together , with gap junctions An impulse travels from one membrane to the next Causes a ction p otential in the second neuron

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What is a synapse? 6.5.6

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  1. What is a synapse?6.5.6 • A junction that permits a neuron to pass a signal, electrical or chemical, to another cell • Electrical Synapses • Two neurons are close together , with gap junctions • An impulse travels from one membrane to the next • Causes action potential in the second neuron • Electrical are faster than chemical

  2. Synapses (cont.) • Chemical Synapses • Action potential causes change in membrane permeability for Calcium Ions (Ca2+ ) 2. As a result, Ca2+ flows into the synaptic knob 3. This causes exocytosis of a transmitter substance in vesicle 4. This neurotransmitter diffuses across synaptic cleft and attaches to receptors in post-synaptic membrane

  3. Chemical cont. • In excitatory synapse, the receptor sites change configuration – open Na+ channels • Causes action potential in neuron • In inhibitory synapse – configuration change in receptors opens the K+ and Cl- channels • K+ moves our Cl- moves in • Increases polarisation of the neuron and increases distance from threshold value

  4. After post-synaptic membrane has been affected, enzymes break down neurotransmitter • Acetyl cholinesterase changes acetylcholine into choline and ethanoic acid • These diffuse into synaptic knob and are absorbed and recycled into acetylcholine • This is a common neurotransmitter found in all synapses in nervous system • Noradrenalin is found in synapse in sympathetic nervous system • Dopamine and serotonin are found in brain

  5. 6.5.7 • Endocrine System • Consists of endocrine glands which produce hormones and secrete them into the blood • Endocrine grand are ductless glands • Do not release products into a duct • Instead secrete into blood (transports to body)

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