You accidentally consume botulinum toxin by eating a contaminated can of sausages. What do you predict will be the most harmful physiological effect?

Question

A.  slowed action potential conduction
B.  respiratory failure due to spastic paralysis (constant muscle contraction)
C.  respiratory failure due to flaccid paralysis (relaxed muscles)
D.  pupil dilation

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?

Gather Content/Choose Answer
· What do you already know about botulism? What other information is related to the question?

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

C.  respiratory failure due to flaccid paralysis (relaxed muscles)

Clarify Question
· What is the key concept addressed by the question?
        o What is the most harmful effect of botulinum toxin?
· What type of thinking is required?
        o This is an analyze question because you need to take information about the neuromuscular junction and synaptic transmission and predict clinical symptoms from a toxin.

Gather Content/Choose Answer
· What do you already know about botulism? What other information is related to the question?
        o To solve this problem, you’ll need to know that ACh is released at neuromuscular junctions and that for a muscle cell to be activated and contract, ACh must be released by synaptic vesicles as they fuse to the pre-synaptic membrane, and then bind to ACh receptors in the post-synaptic membrane. Then you need to consider what the most harmful physiological effects of preventing ACh release would be. Since this toxin prevents muscle contraction (i.e., paralysis), lack of contraction in which muscles would be the most life-threatening? Probably the heart and the lungs. Since no question refers to the heart directly and only two answers refer to the lungs (respiration), one can assume that the answer is either B or C. Answer B cannot be correct because we know that botulinum toxin leads to lack of contraction, not spastic, constant contraction.

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o If you figured out the correct answer, good job! If not, where did you go wrong? Did you forget that lack of ACh release prevents muscle contraction? Did you think through what the most dangerous physiological effects are (e.g., pupil dilation is not life threatening per se). Although slowed action potential conduction would be detrimental, botulinum toxin stops action potentials altogether as ACh release is necessary for action potentials.