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29.2 Neurons KEY CONCEPT The nervous system is composed of highly specialized cells. 29.2 Neurons Neurons are highly specialized cells. • A neuron has three parts. – cell body has nucleus and organelles 1 Cell body 29.2 Neurons Neurons are highly specialized cells. • A neuron has three parts. – cell body has nucleus and organelles – dendrites receive impulses 2 dendrites 29.2 Neurons Neurons are highly specialized cells. • A neuron has three parts. – cell body has nucleus and organelles – dendrites receive impulses – axon carries impulses 3 axon 29.2 Neurons • Neurons have other structures to transmit signals. – Schwann cell---has myelin sheath on outside 4 29.2 Neurons • Neurons have other structures to transmit signals. – Synapse-area b/n 2 neurons 5 synapse 6 Axon terminal 29.2 Neurons Neurons receive and transmit signals. • Resting potential means no signal is being transmitted. – more Na+ outside of cell – more K+ inside of cell – Cell is negatively charged 29.2 Neurons • An action potential is a moving electrical impulse. – It is generated by a stimulus. – Na+ enters, and cell becomes positively charged. – K+ leaves, and area of positive charge moves. area of detail 29.2 Neurons • A chemical signal passes between neurons. – Impulse reaches terminal. impulse 29.2 Neurons • A chemical signal passes between neurons. – Impulse reaches terminal. impulse 29.2 Neurons • A chemical signal passes between neurons. – Impulse reaches terminal. – Neurotransmitters released into synapse. – Neurotransmitters stimulate next cell. synapse impulse neurotransmitter vesicles receptor
