Question

Comparison of the NMJ vs the synapse .

Side by side, draw and label the cells and key factors involved in cell to cell transmission between neuron to neuron and neuron to muscle call. List two diseases where transmission at these junctions in negatively affected. List two medications that target the synapse and expalin how they work.

Answer 1

NMJ vs the synapse:

Differences:

• NMJ is always Acetylcholine, but synapse can use adrenaline, non adrenaline and other neurotransmitter.
• A junction between two neurons is synapse, where as the junction between a motor neuron and a skeletal muscle is NMJ.
• A synapse can be excitatory or inhibitory, where as an NMJ is always excitatory
• synapse may be part of a multi neuronal pathway while the NMJ is the end of a pathway by the definition.

Similarities:

• Both have axon terminals that store chemical messenger
• The change in membrane potential resulting in both cases is a graded potential

For the transmission between neurons, it have to send and receive signals. These signals are produced because of charged cellular membrane of neuron that means the voltage difference across the neuron. Neurotransmitter i.e. released from another neuron causes the change in the charge of this membrane. Electric potential difference between two points generate voltage; for example, the separation of both positive and negative electric charges across a resistive barrier.

Acetylcholine (ACh) is released by motor neurons in vertebrates, neurotransmitter i.e. a small molecule, that diffuses across the synaptic cleft and binds to nicotinic acetylcholine receptors (nAChRs) present on the muscle fiber membrane, also called as sarcolemma. nAChRs are ionotropic receptors, that means they act as ligand-gated ion channels. The ACh binding to the receptor depolarizes the muscle fiber, result in a cascade that finally results in muscle contraction. NMJ diseases may be genetic or autoimmune origin. Genetic disorders like Duchenne muscular dystrophy, arise due to mutation in structural proteins that form the neuromuscular junction, while autoimmune diseases, like myasthenia gravis, occur due to production of antibodies against sarcolemma receptor nicotinic acetylcholine.

Pilocarpine

Pilocarpine is an agonist of acetylcholine. It mimics the acetylcholine action on muscarinic receptors (found at the synapse between the parasympathetic nervous system's post-ganglionic fibres and their effector organs). Pilocarpine increases the acetylcholine's parasympathetic effects and used to treat open angle glaucoma.

Prozac is an anti-depressant drug which results to generate serotonin ( hormone produced in brain leads to feeling of pleasure) concentration in synapses.It blocks the serotonin re-uptake from a synapse.