Announcements: 1.TA Office hours: Mon 10am-12 Wed 12-1pm Room S 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 Neurotransmitter Secretion Receive & Integrate Inputs Impulse conduction

Neurons – diversity of types Cortical Pyramidal Neuron Purkinje Cell dendrites cell body axon

Processing Sensory Input Motor Output Behaviour Organization of nervous system Filters Patterned activity Other sensory input Experience

Simple Complex Anterior specialization ‘brain’ Nerve net Neural ganglia Interconnected Ganglia Segmentation Hydra Leech # of neurons Human 100 x 10 9 nematode 300 correction

Even ‘simple’ nervous systems can display very complex behaviour eg nematodes, leeches, and flies can all display learning!

Brain Segmented Nerve Cord Human Fruit Fly Embryo

Organization of the Vertebrate Nervous System Brain Sensory Receptors Spinal Cord Motor Neurons (efferent) Sensory Neurons (afferent) Voluntary (somatic) Autonomic Central Nervous System Peripheral Nervous System

Division of the Motor Nervous System AutonomicVoluntary Things you control Sympathetic Parasympathetic Heart rate Cardiovascular function Pupil dilation Lung function

Autonomic Nervous System Sympathetic Parasympathetic Parallel Systems that innervate the same target Opposing effects on the target Usually in balance Dilate pupil Increase heart rate Constrict pupil Decrease Heart Rate

The Reflex Arc Inter- neuron Monosynaptic Polysynaptic Sensory receptor Sensory receptor

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 Within neurons Between neurons electrical chemical & electrical A Simple Circuit

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 cell microelectrode amplifier 0 mV -80 mV time Membrane potential Reference electrode Bathing solution

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