It's like pulling teeth a case study in physiology

“It’s Like Pulling Teeth” by Phil Stephens Page 1

It’s Like Pulling Teeth: A Case Study in Physiology Phil Stephens Biology Department Villanova University, Villanova, PA

Part I—The Hospital At last the day had come. Mr. Th ompson was having his wisdom teeth removed. He was tired of the aches and pains and the sight of his puff y face in the mirror every morning. He felt helpless, lying on the gurney watching the ceiling lights whiz by as he was being wheeled to surgery.

Mr. Th ompson had selected this particular oral surgeon because of the sign outside his practice that read: “We cater to cowards.” But the surgeon still hadn’t seemed to understand Mr. Th ompson’s fear of dental procedures; he had wanted to use a local anesthetic. Fortunately, the anesthesiologist was sympathetic to his request for a general anesthetic.

As the mask came over Mr. Th ompson’s face, he felt so alone. It reminded him of how he felt as a boy, in the orphanage. Th en the halothane started to take eff ect and he went under.

As surgery was about to begin, Mr. Th ompson started twitching. Th e anesthesiologist saw Mr. Th ompson’s heart rate increase, his muscle contractions become strong and widespread throughout his body, and the patient began to sweat profusely. As Mr. Th ompson’s temperature quickly increased, the anesthesiologist injected a solution into the IV drip. Th en Mr. Th ompson went limp and all that could be heard was the sound of oxygen rushing through the ventilator, assisting Mr. Th ompson’s breathing.

“Next time we do as I say and we use a local,” muttered the angry surgeon as he glared at Mr. Th ompson.

Questions 1. How is heat generated in the body? 2. In this case, where halothane-induced heat production quickly elevated Mr. Th ompson’s body

temperature, where do you think most of the heat is generated? 3. What chemical reaction is responsible for generating the huge amount of heat? 4. Which processes use ATP as an energy source in skeletal muscle?

“It’s Like Pulling Teeth” by Phil Stephens Page 2

Part II—The Motor Neuron Halothane clearly had an eff ect on Mr. Th ompson’s voluntary motor system. During this case study you will determine the location of this eff ect by looking at the normal function of motor nerves, chemical synapses, and the muscles. You will determine how halothane could act to produce strong and prolonged muscle contractions.

Complete the following fl ow diagram by fi lling in the blanks:

Discuss each of the four stages to see whether halothane could alter motor neuron function to produce strong muscle contractions.

An action potential enters the presynaptic terminal

Voltage-gated channels open and _______ & ______ ions enter the presynaptic terminal

_______ ions cause __________ __________ to fuse with the presynaptic membrane

__________________ is liberated into the synaptic cleft

“It’s Like Pulling Teeth” by Phil Stephens Page 3

Part III—The Chemical Synapse Halothane does not change motor neuron function; perhaps it aff ected the neuromuscular junction. Complete the following fl ow diagram by fi lling in the blanks:

Discuss each of the above six stages to see whether halothane could alter synaptic function and cause a single action potential in a motor axon to produce strong and prolonged contractions of the muscle fi bers it supplies.

____________ is secreted into the cleft

by the motor axon

Th e neurotransmitter reacts with _________ on the muscle

membrane

Channels open and the muscle membrane ___________

Th e neurotransmitter is broken down by __________ _________ in the

synaptic cleft

______ is taken up into the presynaptic cell

Th is produces an ______ _______ in the muscle

membrane

“It’s Like Pulling Teeth” by Phil Stephens Page 4

Part IV—The Muscle Halothane does not change the synaptic function; perhaps it aff ected the muscles. Complete the fl ow diagram below by fi lling in the blanks:

Acetylcholine binding opens the channels and the muscle membrane becomes ___________

Th is creates an action potential, which travels along the _______ ________

Th e action potential travels down the __________ _______ and stimulates voltage-sensitive ___ ________

Calcium ions are released into the sarcoplasm from the ___________ _________

Calcium binds to _______

____________ moves to expose the myosin binding sites on actin

Cross bridge cycling causes the sarcomeres to ______

Calcium is taken up into the __________ ________ to terminate the contraction

Discuss each of the eight stages to see whether halothane could alter muscle function so that a single action potential produces a strong and prolonged muscle contraction.

“It’s Like Pulling Teeth” by Phil Stephens Page 5

Copyright © 2004 by the National Center for Case Study Teaching in Science. Originally published 09/27/04 at http://www.sciencecases.org/teeth/teeth.asp Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

Part V—Hypothesis Look again at the three fl ow diagrams. Within your group decide which step (or steps) are the mostly likely to be aff ected by halothane. Construct a hypothesis within your group and state how the antidote works.

Image Credit: Silhouettes by O. Elkan, courtesy of the National Library of Medicine.

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