Transmission of Impulse: At Chemical Synapse MCQ - Practice Questions with Answers

Transmission of Impulses: At Chemical Synapse

• Transmission across a chemical synapse is carried out by neurotransmitters, which are stored in synaptic vesicles in the axon terminals.
• When nerve impulses travelling along an axon reach an axon terminal, channels for calcium ions (Ca2+) open, and calcium enters the terminal.
• This sudden rise in Ca2+ stimulates synaptic vesicles to merge with the presynaptic membrane, and neurotransmitter molecules are released into the synaptic cleft. 
• They diffuse across the cleft to the postsynaptic membrane, where they bind with specific receptor proteins. 
• Depending on the type of neurotransmitter and the type of receptor, the response of the postsynaptic neuron can be toward excitation or toward inhibition. 
• After excitatory neurotransmitters combine with a receptor, a sodium ion channel opens, and Na+ enters the neuron.
   

• Serotonin is a neurotransmitter that controls mood and induces sleep
• Endorphine is a neuropeptide which acts as a natural analgesic

Transmission of Impulses: At Electrical Synapse

• At electrical synapses, there is continuity between the presynaptic and postsynaptic membranes of the neurons. 
• This continuity is due to the gap junctions.
• Hence, there is a minimal synaptic delay due to direct flow of ions from one neuron to another through gap junctions.
• These are relatively rare and are found in the cardiac muscles, smooth muscles of the intestine and epithelial cells of the lens.