1

Neurotransmission

2

How neurons communicate

Neurons communicate through an electrical signal called the Action Potential

Action Potentials may be triggered by sense organs or by other neurons

An action potential is an all-or-nothing event

3

When does a neuron fire?

Neurons receive neurotransmitter signals through dendrites

Some signals are excitatory (accelerator), some are inhibitory (brake)

If the combined signals reach the “threshold”, it will trigger the action potential

4

Action Potentials

The neuron is electrically charged with positive and negative ions both inside and surrounding the cell

If the threshold is reached, the neuron “fires”, moving ions in and out of the cell and generating an electric impulse which travels down the axon

5

Action Potentials

When an Action Potential occurs, a molecular message is sent to neighboring neurons Neurotransmitters leave the Terminal

Buttons and are collected by neighboring dendrites

After this happens, the ions and neurotransmitters move back to their starting positions, and the neuron is at rest again

6

Myelin Sheath & Nodes of Ranvier

If an axon is myelinated (has a myelin sheath), the action potential will jump directly from node to node, without having to actually travel the whole axon.

Myelin Sheath

7

Neuron to Neuron

Axons branch out and end in buttons near dendrites of neighboring cells

A gap separates the terminal buttons from dendrites

Gap is the “Synapse”

CellBody

Dendrite

Axon

8

Synapse

axon buttons contain small storage sacs called synaptic vesicles

vesicles contain neurotransmitters

SendingNeuron

SynapseAxonTerminal

9

Neurotransmitter Release

Action Potential causes vesicle to openNeurotransmitter released into synapseLocks onto receptor molecule in dendrite of

adjacent neuronNormal psychological (and physiological)

functioning is dependent on neurotransmitter activity

Can be affected by factors such as disease and drugs

10

Locks and Keys

Neurotransmitter molecules have specific shapes

Receptor molecules have binding sites of the same shape

11

Some Drugs work on receptors

Some drugs are shaped like neurotransmitters

Antagonists : fit the receptor but poorly and block the NT e.g. beta blockers

Agonists : fit receptor well and act like the NT e.g. nicotine.

12

Further research

We have covered a lot of material already in this unit and there is more to come!

Make sure you understand what we are doing as we go along!

You can come in for tutoring after school M-Th, I am here most days until at least 3:30.

For this material, check http://www.worthpublishers.com/bloom/content/psychsim/index.htm (site is listed in your packet) – Quiz next class!