Answer to Question 1
With synaptic neurotransmission, neurotransmitters are released in the close proximity to their receptors and most likely induce relatively quick, short duration actions on target neurons. Also, receptor affinity is relatively low. With nonsynaptic neurotransmission, neurotransmitters are generally released from cells relatively far away from their target receptors and are more likely to induce relatively slow onset, long-lasting actions on the target neurons. Receptor affinity is relative high.
Answer to Question 2
This refers to a process in which, following activation of receptors on a postsynaptic neuron, chemicals (neurotransmitters) are released from the postsynaptic neuron, which then travel backwards to the presynaptic neuron to activate receptors on the presynaptic neuron. This action subsequently alters the release of neurotransmitters from the presynaptic neuron. For example, research indicates that endocannabinoids serve as retrograde neurotransmitters that reduce the release of various types of neurotransmitters, e.g., GABA and glutamate, from presynaptic neurons.
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