W1L1: Introduction

neurons, synapses, receptors, neurotransmitters, drug addictions

number of neurons in brain

100 billion

number of neurons in cortex

0.15 quadrillion

cell membrane of neuron

acts as wall to prevent things from entering and leaving neuron

cell membrane of neuron: layers

two fatty layers with fatty inside of each layer sticking together like a sandwich

cell membrane of neuron: fatty layer

because of the layer, fluids and other chemicals like neurotransmitters can’t pass through

receptors

located on outside of cell membrane and allow released neurotransmitters to influence post-synaptic neuron

types of receptors

1. Ion channels

2. G-Protein coupled

receptor: specificity

have very specific function - when a neurotransmitter binds to the receptor this will trigger the same event every time

receptor: structure

not open-shut gates but have complex structures and often a small change in shape will open a channel

receptor: ion channels

act as gates for ions - when neurotransmitter binds to receptor outside neuron, gate opens and ions (either + or - charged molecules) flow through

receptor: g-protein coupled receptor

work through second messengers - when neurotransmitter binds to receptor it activates a second messenger system that can either open a channel or cause other things to change in the cell (DNA being transcribed and new proteins being made)

neurotransmission

1:1 info processing relationship: chemical substance from a neuron at an anatomically specialised junction (synapse), which diffuses across a narrow cleft to affect one of sometimes two postsynaptic neuron’s, a muscle cell or other effector cell

neuromodulation

acting on multiple neutrons with long lasting effects: chemical substance released from a neuron in the CNS or PNS that affects groups of neuron’s, or effector cells that have appropriate receptors - may not be released at synaptic sites, often acts through second messengers

neurotransmission: time

excitatory or inhibitory effect - rapid (millisecond), precise, point to point communication

neuromodulation: time

slower (milliseconds to seconds) processes that alter subsequent responsiveness of neurons, diffusion of communication to a number of neurons

neurotransmitters: currency

excitatory (glutamate) /inhibitory (GABA)

neuromodulators: government

modulatory (serotonin, dopamine, noradrenaline)

neuromodulation: presynaptic

alters neurotransmitter release

neuromodulation: postsynaptic

alters neurotransmitter action (e.g alters excitability, firing pattern)

neuromodulation: changes

can cause changes in neural function or structure (e.g number of receptors/enzymes/synaptic plasticity)

nuclei

bundle of cell bodies

neuromodulators: location

originate in small clusters of neurons (nuclei) deep within brain (mostly brain stem)

noradrenaline (NE) system: location

main nucleus is ‘locus coeruleus’ in the pons

histamine (HA) system: location

‘forgotten one’ - neurons localised to posterior hypothalamus (affects sleep and arousal)

cholinergic (ACh) system: location

pontine and basal forebrain groups (smoking affects)

dopamine (DA) system: location

ventral tegmental area and substantial nigra area (midbrain)

serotonin (5-HT) system: location

several ‘raphe’ nuclei distributed in brainstem (across medulla, pons and midbrain of brainstem)

neurotransmitter: synthesis and transport to synapse

slow

neurotransmitter: action

extremely fast because it sits ready for release

psychopharmacology

study of drug induced changes in mood, sensation, thinking and behaviour

drugs: action at recepetor

mimic natural neurotransmitters/neuromodulators

drugs: agonists

activate receptor like natural compound

drugs: antagonists

block receptor and prevent natural compound from activating it

cycle of neurotransmitters

1. synthesis

2. release from synaptic vesicles

3. binds to receptors

4. ± influence on post synaptic neuron

5. broken down into enzymes

6. reuptake of transmitter

   1. formation and storage in synaptic vesicles

synthesis interruption

neurotransmitter function can be altered by increasing or decreasing synthesis of the neurotransmitter - adding or subtracting molecules is how neurotransmitters are synthesised

MDMA: transport in neurotransmitter interruption

1. MDMA mimics serotonin (5-HT) and enters neurons

2. MDMA prevents serotonin storage in vesicles

3. serotonin accumulates in cytosol because packaging is inhibited

4. MDMA switches direction of explore, instead of import

5. serotonin concentrations increase in synaptic cleft

6. Post-synaptic serotonergic neurons fire continuously

hormones

signalling molecules produced by glands and transported through blood to regulate physiology (muscles, neurons) and behaviour

pharmacology affects psychology

natural neurotransmitters and natural/artificial drugs can affect mood, cognition and behaviour

psychology affecting pharmacology

emotional or stressful events, thoughts and behaviour affect humans because they influence neurotransmitters