What are the stages of synaptic transmission?
- Action potential reaches the axon terminal of the presynaptic neuron
- Depolarization of the terminal leads to an influx of Calcium
- The vesicles bind to the membrane of the axon terminal
- Vesicles release neurotransmitters into the synaptic cleft
- Neurotransmitters bind to receptors causing either excitatory postsynaptic action potentials (EPSP) or inhibitory postsynaptic actions potentials (IPSP)
- Excess neurotransmitters are removed from the synapse through breakdown or reuptake into the presynaptic cell
- Other Neurotransmitters in the synapse bind to autoreceptors in the presynaptic membrane to give “feedback” on the signal that it produced
What are ligands?
Molecules that bind to postsynaptic receptors and can either “activate” or “deactivate” them
What are endogenous ligands?
Ligands which are made within the body such as neurotransmitters
What are exogenous ligands?
Ligands which are made outside of the body such as drugs
What are the two types of receptors in the post-synaptic membrane.
Ionotropic receptors & Metabotropic receptors
What are Ionotropic receptors and how do they work?
Ionotropic receptors are receptors which have ion channels. When a neurotransmitter binds to them, their channels open to allow for the flow of ions into the membrane, but only for a few seconds.
What are Metabotropic receptors and how do they work?
Metabotropic receptors are receptors that do not have their own ion channels. When a neurotransmitter binds to a metabotropic receptor, which in turn activates G-proteins which act as second messengers which open other ion channels for a longer period of time.
What are the three different types of effects that ligands can have on receptors?
- Agonists: which activate/opens channels
- Antagonists: which deactivate and hold the channels closed (inserts the key but just blocks the lock)
- Inverse Agonists: will bind and make the receptor to the opposite of it’s reaction
What is Glutamate?
It is the primary excitatory neurotransmitter found in the brain.
What is GABA?
It is the primary inhibitory neurotransmitter found in the brain.
Where is Acetylcholine distributed, source, and function?
Acetylcholine is widely distributed throughout the PNS and CNS. Acetylcholine’s source is the forebrain nuclei, and Acytlcholine’s functions include alertness and signal amplification.
Where is serotonin distributed, source, and function?
Serotonin is a hormone and neurotransmitter which is broadly distributed in the CNS. Serotonin’s source is the Raphe Nuclei. Serotonin functions in mood, and cognition.
Where is Norepinephrine distributed, source and function?
Norepinephrine is a hormone and a neurotransmitter which coordinates with the autonomic nervous system. It’s source is the locus coeruleus. Norepinephrine functions in general cognition.
Where is Dopamine distributed, source and function?
Dopamine is a hormone and neurotransmitter and has several forebrain pathways. It’s source is the ventral tegmental area. Dopamine functions in motor regulation and reinforcement.
What are five ways in which drugs can affect the pre-synaptic cell?
- Inhibition of transmitter synthesis, not allowing certain transmitters to synthesize
- Blockade of Axonal Transport
- Prevention of synaptic activity (not allowing for the firing of action potentials)
- Inactivation of transmitter reuptake
- Blockade of transmitter degradation
What are five ways in which drugs can affect the post-synaptic cell?
- Blockade of receptors
- Activation of receptors
- Modulation of intracellular signals, alternation of second messenger systems
- Down-regulation of receptors, decrease in post-synaptic receptor density
- Up-regulation of receptors, increase in post-synaptic receptor density
What is down-regulation?
Down-regulation is a long-term effect that ligands can have on receptors. It causes a decrease in receptor density, making the synapse weaker as there is less weight.
What is up-regulation?
Up-regulation is a long-term effect that the ligands can have on receptors. It causes an increase in receptor density, making the synapse strong as it has more weight .
What are the five stages of drug action?
- Administered
- Absorbed
- Binds to a receptor or a depot
- Breakdown-Inactivation
- Elimination from the body
What are the 3 factors which influence the effect of the drug on the body?
- Dose
- Set (individual variables)
- Setting (Situation variables)
What are five types of psychoactive drugs and a brief description of the mechanism of action on the brain?
- Anxiolytics: Calm the sytem, GABA agonists, increase inhibition
- Cannabinoids: affect hunger, memory, and stress, bind to cannabinoid receptors
- Ethyl Alcohol: CNS depressant
- Opiods: pain reliever, bind to opioid receptors
- Psychostimulants; increase arousal, caffeine inhibits the inhibition of ATP production
What are Antipsychotics?
Drugs that are used to treat psychoses.
1st generation affects libido and motor function
2nd generation has a broad-spectrum of side-effects
What are Antidepressants?
Drugs that relieve major depressive disorder, they prevent the breakdown of dopamine
What are Anxiolytics?
Drugs that help calm an over-aroused nervous system, work as GABA agonists increasing general CNS inhibition
