Sandra was 74 years old. She often complained being fatigue, having muscle cramps, difficulty swallowing, and needing machines to help her breath. During reflex tests, she also showed absents of some reflexes. Both her presynaptic and postsynaptic neurons were low in numbers. Her postsynaptic neurons were lower than presynaptic neurons. With further investigation, it was revealed that she was exposed to a chemical that increases intracellular protein production in the nerves. This unknown chemical could also increase release of excessive excitatory neurotransmitters which could cause death in postsynaptic neurons. Knowing that rise in massive amount of Ca2+ in cytoplasm of postsynaptic neuron could kill the nerve, propose two mechanisms that may be involved in Ca2+ entry to the postsynaptic neurons after the release of the neurotransmitters in the synaptic cleft: (Hint: need to show how Ca2+ enters the neurons). 1) In one sentence, explain why Sandra had all those symptoms:
2) Why do you think both the numbers of presynaptic and postsynaptic neurons were low? Why do you think the numbers of postsynaptic potential were lower?
3) Assuming Sandra was exposed to a nerve gas that inhibits the enzyme involved in breaking down Glutamate, propose a mechanism to counteract this effect:
4) Assuming she is suffering from hyperexcitability syndrome, which is abnormality of AP repolarization, what channels may be associated with nerve AP that might lead to this condition?
5) Assuming Sandra had a seizures, her doctor prescribed Valium to control the seizure. Seizures are related to uncontrolled excessive electrical activity of groups of neurons in the brain. Based on your knowledge of nervous system and action potential, do you think this drug enhances EPSPs or IPSPs?
6) What kind of neurotransmitter do you think Valium could promote to bind to its receptor postsynaptically? Provide explanation and why would this effect reduce the likelihood of seizures?
These questions are not related to Sandra’s case.
At the hillock region, 12 of the neurons produce EPSPs of 2 mV each, and the other three produce IPSPs of 3 mV each. Will an action potential be produced?
7) For each of the following drugs, state how they would affect neural communication (i. e. resting membrane potential, action potential, or synapse). HINT: Think about where each of these channels are located. If they are blocked what does that lead to?
a. Digitalis – inhibits the Na+/K+ ATP-ase pump
b. Warfarin (inhibits the enzyme that breaks down acetylcholine in the synaptic cleft)