Neurotransmitters

Neurotransmitters

chemicals contained in synaptic vesicles in the axon terminal/ presynaptic terminal

Bridge the synapse/ synaptic cleft

Released when the presynaptic membrane and the synaptic vesicles bond (occurs when Ca2+ ion channels open and calcium flows into the cell)

Bond to neurotransmitter receptors on post synaptic neuron (causes a postsynaptic potential; electrical change in charge, that can be excitatory or inhibitory)

Excitatory PSP

Opens a sodium ion channels, depolarization occurs, action potential likely to fire and continue

Inhibitory PSP

Allows chloride (Cl-) to flow in to cell, hyperpolarization occurs, AP less likely to occur

Enzymatic degradation

Breaking down of the neurotransmitters that remain in the synaptic cleft by specialized proteins or enzymes

Often taken back to presynaptic neuron to synthesize new neurotransmitters (ex. Acetylcholine)

Reuptake

More common process of termination

Functional neurotransmitter molecules drawn back to presynaptic neuron and recycled for future use (ex, dopamine, serotonin, norepinephrine)

• SSRIs inhibit the reuptake of serotonin therefore increasing amount of serotonin available

Important neurotransmitters

1. ACH

2. Dopamine (DA)

3. Norepinephrine (NE)

4. Serotonin (5-HT)

5. GABA (gaba- amino butyric acid)

6. Glutamate

Acetylcholine

• important for stimulating muscles (role in communication between motor and sensory neurons)

• Important for attention, arousal and memory, plays a part in REM sleep

• Affected by nicotine, some snake venom and Botox/ botulin

Dopamine

• associated with mood, voluntary movement control, reward centre

• Excessive amount of dopamine in frontal lobe associated with schizophrenia

• Too little in motor areas of brain associated with Parkinson’s

• Number of drugs increase dopamine levels (heroin, opium, alcohol, nicotine, cocaine, meth)

Norepinephrine

• involved in stimulating the sympathetic NS

• Also plays a role in learning memory sleep and emotions

• Low levels linked to depressive disorders

• High levels linked to anxiety

Serotonin

• involved in regulation of food, appetite sleep and perception of pain

• Plays a role in activity levels and cognitive functions like learning and memory

• Ecstasy, LSD, MAOIS (monoamine oxidase inhibitors), SSRIs (antidepressants) act on serotonin

GABA

• most common inhibitory neurotransmitter

• Reduces activity of neuron it binds to

• Implicated in sleep associated with reduction of NS arousal

• Benzodiazepines (Valium etc) mimic GABA to reduce anxiety

• Alcohol acts on GABA

• Abnormal levels linked to epilepsy and eating disorders

Glutamate

• believed to be most important for normal brain function

• Most common excitatory neurotransmitter

• plays central role in learning and formation of new memories

• Excessive glutamate activation has been linked to neuron degenerative disorders like Huntington’s

• Ketamine acts on glutamate

Hebbian synapses

Synapses that change as a result of input or experience

Structural plasticity vs functional plasticity

SP: experience or memory change a brains physical structure

FP: areas of function move to undamaged areas when damage occurs