Neurotransmitters

Threshold

Minimum number of neurotransmitter molecules attached to receptors to transmit an impulse

What is a summation?

When a series of weak stimuli release enough neurotransmitters to trigger an impulse, found in convergent neural pathways

What can synapses filter out?

Weak stimuli

What are Endorphins?

Neurotransmitters that stimulate neurons involved in reducing pain intensity

What increases endorphin production?

Severe injury

Prolonged/continuous exercise

Stress

Certain foods

What is a synapse?

The junction between two neurons

What is a synaptic cleft?

The gap that connects neurons with other neurons/muscle fibres

What are neurotransmitters?

Chemicals that relay impulses across the synaptic cleft

Where are neurotransmitters stored?

Vesicles in the axon endings of the presynaptic neeuron

When are neurotransmitters released

On arrival of an impulse

Explain why neurotransmitters must be removed from a synaptic cleft.

To prevent continuous stimulation

The part of the brain targeted by many recreational drugs

The reward pathway

What does dopamine stimulate?

The reward pathway

Four things in the brain altered by recreational drugs and how these affect neurotransmission at synapses

Mood

Cognition (ability to think)

Perception

Behaviour

A chemical that binds to and stimulates a receptor, mimicking a neurotransmitter

Agonist

A chemical that binds to a receptor and blocks a neurotransmitter’s action

Antagonist

Are recreational drugs agonist or antagonist

Can be agonist OR antagonist

Dopamine acts as an agonist for acetylcholine

Describe how nicotine acts as an agonist at a synapse.

Dopamine mimics the action of acetylcholine

Describe how drug addiction is caused

causes the nervous system to increase the number and sensitivity of these receptors.

This sensitisation leads to drug addiction where the individual craves more of the drug.

Reduced drug effect caused by repeated use of agonist drugs

Tolerance

What happens to the receptors during drug tolerance

The nervous system decreases both the number and sensitivity of these receptors

Neurotransmitter that induces feelings of pleasure via the reward pathway

Dopamine

Inhibitory

Type of signal that makes an impulse less likely to be generated

Excitatory

Type of signal that makes an impulse more likely to be generated

effects of disease on myelination and the impact on responses to stimuli

1. Loss of the myelin sheath

2. Loss of co-ordination to stimuli