Announcements:

1. TA Office hours:

Mon 10am-12

Wed 12-1pm

Room S161

2. Prerequisites

BGYA01H & BGYA02H OR BGYA01Y

• Today1. 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 types1. 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 & IntegrateInputs

Impulse conduction

Neurons – diversity of types

Cortical Pyramidal NeuronPurkinje Cell

dendrites

cell body

axon

ProcessingSensory Input Motor OutputBehaviour

Organization of nervous system

Filters Patternedactivity

Other sensory input

Experience

Simple ComplexAnterior specialization

‘brain’Nerve

netNeuralganglia

InterconnectedGanglia

Segmentation

Hydra Leech

# of neurons

Human100 x 109

nematode300correction

• Even ‘simple’ nervous systems can display very complex behaviour

• eg nematodes, leeches, and flies can all display learning!

Brain

SegmentedNerve Cord

HumanFruit Fly Embryo

Organization of the VertebrateNervous System

Brain

Sensory Receptors

Spinal Cord

Motor Neurons(efferent)

Sensory Neurons(afferent)

Voluntary(somatic)

Autonomic

CentralNervousSystem

PeripheralNervousSystem

Division of theMotor Nervous System

Autonomic Voluntary

Things you controlSympathetic

Parasympathetic

Heart rateCardiovascular function

Pupil dilationLung function

Autonomic Nervous System

Sympathetic

Parasympathetic

• Parallel Systems that innervate the same target• Opposing effects on the target

•Usually in balance

Dilate pupilIncrease heart rate

Constrict pupilDecrease Heart Rate

The Reflex Arc

Inte

r-n

euro

n

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

microelectrodeamplifier

0 mV

-80 mVtime

Membrane potentialReferenceelectrode

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