1. Voltage-gated ion channels and ligand-gated ion channels 

2. Voltage-gated: 

• responds to changes in membrane potential 
• they are in a high concentration on the axons of nerve cells
• they open sodium, potassium, and calcium channels  

Ligand-gated: 

• responds to neurotransmitters
• they are found on presynaptic and postsynaptic cell bodies 
• they can either function as ionotropic or metabotropic 

3. Ionotropic receptors opens ion channels by working directly on them, whereas metabotropic receptors use signal transduction mechanisms when there is metabolic change with the help of 2nd messengers. 

4. Ionotropic receptors include GABA-A, Nicotinic, EAA, and 5-HT3. Metabotropic receptors work with transduction systems that rely on the formation of 2nd messengers. Adenylyl cyclase systems and Phospholipase C systems are transduction systems. 

Adenylate cyclase receptors include negative( D2, α2,5-HT1 A+B , M2 ) and positive( ß1 + 2, D1) receptors, which convert ATP to cAMP. cAMP activates various protein kinase enzymes. 

Phospholipase C receptors are positive and include α1, 5-HT2 M1, H1 receptors. This system converts PIP2 to IP3 and/or DAG. IP3 and DAG function as second messengers.  

5. EPSP: Excitatory postsynaptic potentials that are generated by the opening of Sodium or Calcium channels. Exp: Nicotinic, EEA, and 5-HT3 receptors 

IPSP: Inhibitory postsynaptic potentials that are generated by the opening of potassium or chloride channels. Exp: GABA-A 

6. An influx of calcium into the presynaptic membrane causes NT release from the synaptic vesicles into the synaptic cleft. The NT can then diffuse and bind to the postsynaptic membrane, this will produce an effect. Calcium is essential for  NT release and ultimately for the effect.