Read page 424-425 on Read page 424-425 on drugs and the braindrugs and the brain

What 3 major concepts should we What 3 major concepts should we study to understand this article study to understand this article

further?further?

SynapseSynapsesin-aps, si-napssin-aps, si-naps

SynapseSynapse (noun) Small gap between nerve (noun) Small gap between nerve

cellscellsUse in a sentence: A synapse is Use in a sentence: A synapse is

cool.cool.

Neurotransmitters and Neurotransmitters and The Synapse The Synapse

Synapse: unique junction that mediates Synapse: unique junction that mediates information flow from one neuron to information flow from one neuron to

another or effector cell… another or effector cell… huh?huh?

Most synapses occur between axon of one Most synapses occur between axon of one nerve and the dendrite of another… BUTnerve and the dendrite of another… BUT

Pre vs PostPre vs Post

Presynaptic neuron- carries impulse towards Presynaptic neuron- carries impulse towards a synapse “Sender”a synapse “Sender”

Postsynaptic neuron- carries impulse away Postsynaptic neuron- carries impulse away from a synapse “receiver” from a synapse “receiver”

TWO TYPES: TWO TYPES: A. electrical synapse A. electrical synapse

B. chemical synapse B. chemical synapse

Electrical Synapse Electrical Synapse

Allow current carrying ions to flow directly Allow current carrying ions to flow directly from one neuron to the nextfrom one neuron to the next

Found in the brain, limited in adulthood Found in the brain, limited in adulthood

Most are replaced by Most are replaced by chemical chemical synapses synapses

Chemical SynapsesChemical Synapses

-release/reception of neurotransmitters -release/reception of neurotransmitters

Neurotransmitters act to open/close ion Neurotransmitters act to open/close ion channels channels

Anatomy of the chemical synapse Anatomy of the chemical synapse

axonal terminalaxonal terminal synaptic vesiclessynaptic vesicles

receptor region receptor region

synaptic cleft synaptic cleft

Information Transfer Across Information Transfer Across Chemical Synapses Chemical Synapses

1. Calcium gates open in the presynaptic 1. Calcium gates open in the presynaptic axonal terminal axonal terminal

Depolarization causes voltage-gated Ca2+ Depolarization causes voltage-gated Ca2+ channels to open channels to open

2. Neurotransmitter is released 2. Neurotransmitter is released Direct result of calcium being present Direct result of calcium being present Exocytosis Exocytosis

3. Neurotransmitter binds to post-synaptic 3. Neurotransmitter binds to post-synaptic receptors receptors

4. Ion channels open in the post-synaptic 4. Ion channels open in the post-synaptic membrane Boom! membrane Boom!

Neurotransmitters Neurotransmitters

-language of the nervous system -language of the nervous system -50 known NT-50 known NT

Classification Classification

1. Acetylcholine (ACh) 1. Acetylcholine (ACh) -first identified, best understood -first identified, best understood

2. Biogenic Amines2. Biogenic Amines Include: dopamine, norepinephrine and Include: dopamine, norepinephrine and

epinephrine, histamine and serotonin epinephrine, histamine and serotonin

3. Amino Acids3. Amino Acids 4. Peptides (neuropeptides)4. Peptides (neuropeptides)

substance P, endorphins, substance P, endorphins, 5. Novel Messengers5. Novel Messengers ATP ATP Nitric Oxide Nitric Oxide Carbon Monoxide Carbon Monoxide

Synthesis of NeurotransmittersSynthesis of Neurotransmitters