Problem 1: The primary symptom Idris experiences after the bite is cramping of his gastrocnemius muscle. This symptom spreads to his quadriceps muscle. In some cases, the cramping contraction can also occur in the muscles of the back and abdominal wall. Which division of the peripheral nervous system is being altered by the black widow venom in this case? (I.e., which division includes skeletal muscles like the gastrocnemius)?
Problem 2: Idris also experiences stomach cramping as a secondary symptom. Which division of the peripheral nervous system is being altered by the black widow venom in this case? (I.e., which division includes smooth muscles, like that found in the stomach)?
Problem 3: In the space below, draw a synapse. Please label the following things: Synapse, pre-synaptic neuron, post-synaptic cell (assume this is a muscle cell, rather than a neuron), synaptic cleft, vesicles, neurotransmitters, Ca2+ voltage-gated channel, receptors (chemical-gated channels).
The venom from black widows contains a protein called latrotoxin. Latrotoxin binds to proteins in the membrane of pre-synaptic neurons at the synapse. Latrotoxin is introduced to tissues at the site of the bite first and, second, to additional tissues after entering the blood stream. After binding, latrotoxin inserts into the membrane of the pre-synaptic neuron and creates Ca2+ leak channels. Add Ca2+ leak channels to your drawing above to help you visualize the role of the toxin.
Problem 4: Using your drawing, what would be the result of the insertion of Ca2+ leak channels in the axon terminal of pre-synaptic neurons in relation to the process of secretion?
Problem 5: Based on your knowledge of secretion, predict what response will occur in the target tissue (i.e., muscle) and how it relates to Idris' symptoms.
Problem 6: Why did Idris experience cramping of his gastrocnemius first, followed by his quadriceps and then his stomach?
Treatment for black widow spider bites can include doses of benzodiazepine like the doctor administered to Idris in the hospital. Benzodiazepines bind to chloride (Cl-) chemical-gated channels in post-synaptic neurons and muscle cells. Chloride ions are at a higher concentration in the extracellular fluid compared to the intracellular fluid.
Problem 7: Will the influx of Cl- cause an excitatory post-synaptic potential or an inhibitory post-synaptic potential? Explain your answer.
Problem 8: If benzodiazepine is administered to a patient that has NOT been bit by a spider, what is the result in relation to activation of the target (i.e., muscle)?
Problem 9: When given to Idris after the spider bite to relieve his symptoms, what is the combined effect of latrotoxin and benzodiazepine on the process of secretion? Assume equal activity of the two chemicals.