Option E.4 Neurotransmitters & Synapses

Page 360

Synaptic Transmission

• Neurons communicate with each other chemically across a space called a synapse

• Presynaptic membrane – Sending

• Postsynaptic membrane – Receiving

• The molecule moving across the space (synaptic cleft) is called a neurotransmitter

Neurotransmitters

• Some NTs are excitatory – Stimulate the next neuron to forward the message – Increase the permeability to positive ions (positive

ions move in) • Some NTs are inhibitory – They cause positive ions to move out of the

postsynaptic cell – Movement of positive ions back into the synaptic cleft

chemically depresses the postsynaptic cell (harder to excite)

Question

• When two neurons communicate with each other, the presynaptic neuron sends a message across the synapse to the postsynaptic neuron. – 1. What type of molecule carries the message

across the synapse and what type of molecule receives the message?

– 2. Explain the two ways that presynaptic neurons can act on postsynaptic neurons.

Decisions, decisions

• What interaction occurs between excitatory and inhibitory presynaptic neurons acting at the synapse?

• Open your book to page 361. Read pages 361-362. Then answer the following questions: – In your own words, outline the steps of decision making

in the central nervous system.– Identify an excitatory neurotransmitter. Outline how an

excitatory neurotransmitter works. – Identify an inhibitory neurotransmitter. Outline how an

inhibitory neurotransmitter works.

Psychoactive drugs

• Before we talk about how drugs affect the brain & personality, we need to have a fundamental understanding of two neurotransmitters: – Acetylcholine – Noradrenaline

Cholinergic vs. Adrenergic Synapses

• Synapses using acetylcholine are called cholinergic synapses – Nicotine, for example, stimulates transmission in

cholinergic synapses calming effect • “C”

• Synapses using noradrenaline are called adrenergic synapses – Cocaine & amphetamines stimulate adrenergic

synapses increased alertness, energy & euphoria • “A”

What’s amphetamine?

• Adderall (ADHD/cognitive control)• Sometimes prescribed “off label” for

depression, obesity & nasal congestion

Effect of drugs on the brain

• Drugs can alter your mood & emotional state• Excitatory drugs like nicotine, cocaine and

amphetamine increase nerve transmission • Inhibitory drugs like benzodiazepines, alcohol

and tetrahydrocannabinol (THC) decrease likelihood of nerve transmission

How can drugs change synaptic transmission?

• Block a receptor for a neurotransmitter• Block release of a neurotransmitter • Enhance release of a neurotransmitter • Enhance neurotransmission by mimicking a

neurotransmitter • Block removal of a neurotransmitter from the

synapse and prolong the effects of the NT

EXCITATORY!!!! DRUGS

• Turn to page 365.• Explain the effects of nicotine, cocaine and

amphetamine in terms of their actions at the synapses in the brain.

Inhibitory Drugs

• Turn to page 366.• Explain the effects of GABA, alcohol and THC

in terms of their actions at the synapses in the brain.