neurons 09 FINAL

neurons 09 FINAL - BIOLOGY 5B Nervous Systems Review...

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Unformatted text preview: BIOLOGY 5B Nervous Systems Review Session for Final exam: Monday 8 June 7:00-8:30 pm Bourns B118 CONCEPT: Neuron organization and structure reflect function in information transfer Nervous systems process information in three stages: sensory input , integration , and motor output Sensors detect external stimuli and internal conditions and transmit information along sensory neurons Sensory information is sent to the brain or ganglia, where interneurons integrate the information Motor output leaves the brain or ganglia via motor neurons, which trigger muscle or gland activity Sensor Sensory input Integration Effector Motor output Peripheral nervous system (PNS) Central nervous system (CNS) Neuron Structure and Function Most of a neurons organelles are in the cell body Most neurons have dendrites , highly branched extensions that receive signals from other neurons The axon is typically a much longer extension that transmits signals to other cells at synapses An axon joins the cell body at the axon hillock Dendrites Stimulus Nucleus Cell body Axon hillock Presynaptic cell Axon Synaptic terminals Synapse Postsynaptic cell Neurotransmitter A synapse is a junction between an axon and another cell The synaptic terminal of one axon passes information across the synapse in the form of chemical messengers called neurotransmitters A Neuron is the Functional Unit of the Nervous System Information is transmitted from a presynaptic cell (a neuron) to a postsynaptic cell (a neuron, muscle, or gland cell) Most neurons are nourished or insulated by cells called glia CONCEPT: Ion pumps and ion channels maintain the resting potential of a neuron Every cell has a voltage (difference in electrical charge) across its plasma membrane called a membrane potential Messages are transmitted as changes in membrane potential The resting potential is the membrane potential of a neuron when it is not sending signals. Note that it is highly negative on the inside because the charges are kept separate when the neuron is resting . It is highly polarized Formation of the Resting Potential At resting potential, the concentration of K + is greater inside the cell, and the concentration of Na + is greater outside the cell Sodium-potassium pumps use the energy of ATP to maintain these K + & Na + gradients across the plasma membrane These concentration gradients represent chemical potential energy OUTSIDE CELL [K + ] 5 m M [Na + ] 150 m M [Cl ] 120 m M INSIDE CELL [K + ] 140 m M [Na + ] 15 m M [Cl ] 10 m M [A ] 100 m M (a) (b) OUTSIDE CELL Na + Key K + Sodium- potassium pump Potassium channel Sodium channel INSIDE CELL (b) OUTSIDE CELL Na + Key K + Sodium- potassium pump Potassium channel Sodium channel INSIDE CELL...
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neurons 09 FINAL - BIOLOGY 5B Nervous Systems Review...

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