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Upload-P431-Chapter 4&5 - Chapters 4&5 Neural...

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Unformatted text preview: Chapters 4&5: Neural Communication I Chapters Neurons of nervous system (NS) II. Electrical activity of neurons III. Synaptic transmission between neurons I. I. Neurons of nervous system (NS) I. Two divisions of the nervous system: CNS: the brain and the spinal cord. PNS: the rest of the NS. Two types of cells of the nervous system: Nerve cells: neurons. Supporting cells. According to the functions, 3 types of neurons. According Sensory neurons (Afferent): Sensory gather information gather Motor neurons (Efferent): Motor control the muscles control Interneurons: connect sensory and motor neurons connect Four basic structures of neurons. Cell body (Soma): the metabolic center. Dendrites: receive synaptic messages. Axon: carries the nerve impulse from the Axon: cell body to the terminal buttons. Axons are often coated with myelin sheath with a small portion of uncoated axon between the segments of myelin sheath—node of Ranvier. Ranvier. Terminal buttons: release neurotransmitters Terminal (transmitter substances). (transmitter Internal structures of neurons Membrane: consists of a double layer of Membrane: lipid molecules and contains proteins that perform the following functions: perform • detect chemicals outside the cell • control access to the cell • transport molecules into or out of the cell Cytoplasm: a jelly like substance. Mitochondria: break down nutrients, and Mitochondria: provide the cells with energy. provide Enzymes: cause molecules to join together Enzymes: or to be split apart. or Nucleus: contains chromosomes DNA DNA genes genes II. Electrical activity of neurons II. A. Basic concepts Membrane potential: an electrical charge. Resting potential: -70mV with the inside of Resting the neuron being negative. the Action potential: rapid reversal of the Action membrane potential from -70mV to +50mV to -70mV to overshooting the resting potential and back to -70mV. potential Depolarization: a reduction of the membrane Depolarization: potential of a neuron from its resting potential. potential Hyperpolarization: an increase in the Hyperpolarization: membrane potential of a neuron from its resting potential. resting Threshold of excitation: the voltage level that Threshold triggers an action potential. triggers B. Reasons for membrane potential B. Force of diffusion: the tendency for molecules Force or ions to distribute themselves evenly. or Electrostatic pressure: the force exerted by Electrostatic ions to repel or attract each other. ions Intracellular fluid: the fluid within cells K+,AK+,A Extracellular fluid: the fluid surrounding cells Na+,ClNa The sodium-potassium pump: pushing 3 Na+ out of the cell for every 2 K+ pushed in. out pushed C. Movements of ions during the action potential C. Ion channel: protein molecules containing Ion passages that can open or close. passages Voltage-dependent ion channels: ion channels Voltage-dependent that are opened by changes in the membrane potential. potential. Action Potential D. Conduction of the action potential D. All-or-non law: an action potential either All-or-non occurs or does not occur. occurs Rate law: the rate of firing provides variable Rate information. information. Saltatory conduction: conduction of an action Saltatory potential from node of Ranvier to node of potential Ranvier down a myelinated axon. Ranvier Saltatory conduction III. Synaptic transmission between neurons III. A. Structures of synapses: Synapse: the junction between the terminal Synapse: button and the membrane of another neuron. button Synaptic cleft: a small gap between neurons. Presynaptic membrane: the membrane of Presynaptic terminal buttons. terminal Postsynaptic membrane: the membrane of Postsynaptic receiving neurons. receiving Synaptic vesicles: small containers with Synaptic neurotransmitter. neurotransmitter. Release zone: the region of the presynaptic Release membrane from which the neurotransmitter is released. released. B. Postsynaptic potentials B. Postsynaptic receptors: protein molecules that Postsynaptic are form-fitted to the molecular shape of the matching neurotransmitter. matching Postsynaptic potential: a brief change in the Postsynaptic membrane potential of the postsynaptic cell. membrane EPSPs (excitatory): depolarization produced EPSPs by the opening of neurotransmitter-dependent Na+ or Ca2+ channel. Na IPSPs (Inhibitory): hyperpolarization produced IPSPs by the opening of neurotransmitter-dependent K+ or Cl- channel. Neural integration: the interaction of the Neural effects of excitatory and inhibitory synapses on a particular neuron. on C. Termination of the postsynaptic potential C. Reuptake: removal of neurotransmitter from Reuptake: the synaptic cleft by the terminal buttons. the Enzymatic deactivation: destruction of a Enzymatic neurotransmitter by an enzyme (Acetylcholine). (Acetylcholine). D. Autoreceptors: D. Receptors on the terminal button that regulate Receptors the release of neurotransmitter. the ...
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