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Announcements: 1. TA Office hours: Mon 10am-12 Wed 12-1pm Room S161 2. Prerequisites BGYA01H & BGYA02H OR BGYA01Y • Today 1. The neuron 2. Organization of the nervous system • Next lecture – Resting membrane potential Section One: Nervous System • 5 lectures on basic nerve cell properties – Especially electric potentials • 4-5 lectures on neural communication • 4-5 lectures on sensory reception Cells of the Nervous System • Two major cell types 1. Neurons • Electrical and chemical communication 2. Glia • • Important for development and support Myelin Neurons are the fundamental unit of the nervous system The Neuron – vertebrate motor neuron Dendrites Cell Body (Soma) Axon Nerve Terminal Receive & Integrate Inputs Impulse conduction Neurotransmitter Secretion Neurons – diversity of types dendrites cell body axon Cortical Pyramidal Neuron Purkinje Cell Organization of nervous system Other sensory input Motor Output Behaviour Processing Sensory Input Patterned activity Filters Experience Simple Nerve net Complex Neural ganglia Hydra Interconnected Ganglia Segmentation Anterior specialization ‘brain’ Leech # of neurons correction nematode 300 Human 100 x 109 • Even ‘simple’ nervous systems can display very complex behaviour • eg nematodes, leeches, and flies can all display learning! Brain Segmented Nerve Cord Fruit Fly Embryo Human Central Nervous System Peripheral Nervous System Organization of the Vertebrate Nervous System Brain Sensory Neurons (afferent) Sensory Receptors Spinal Cord Motor Neurons (efferent) Autonomic Voluntary (somatic) Division of the Motor Nervous System Autonomic Sympathetic Parasympathetic Heart rate Cardiovascular function Pupil dilation Lung function Voluntary Things you control Autonomic Nervous System • Parallel Systems that innervate the same target • Opposing effects on the target •Usually in balance Sympathetic Parasympathetic Dilate pupil Constrict pupil Increase heart rate Decrease Heart Rate The Reflex Arc Sensory receptor Monosynaptic Sensory receptor Interneuron Polysynaptic Summary & Key Points 1. The fundamental cell of the nervous system is the neuron. 2. The neuron has functionally specialized regions 3. Evolution of the nervous system includes increasing cell number and interconnection 4. Subdivisions of the vertebrate nervous system Neural Signaling A Simple Circuit Within neurons electrical Between neurons chemical & electrical Membrane Potentials • Neurons, like most cells, have an electric potential (voltage) across the cell membrane – Inside is more negative than the outside • Neurons use this electric potential to carry information Measuring Membrane Potential amplifier microelectrode Reference electrode Membrane potential 0 mV cell -80 mV Bathing solution time Membrane Potentials • Depend on: 1. Selective Permeability of the Cell Membrane 2. Unequal distribution of ions across the membrane • Next lecture: Ionic basis of membrane potential
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