Solutions to a variety of anatomy and physiology case study

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~Elvis Presley died on August 16, 1977. He was extremely overweight when he died. He had a history of ingesting fatty foods including fried peanut butter and banana sandwiches. He also had a long list of prescription medications he was taking, some of which had cardiovascular or neurological effects. He died on the toilet while trying to defecate. The post-mortem exam on Elvis Presley revealed that his rectum and colon were severely impacted with fecal material, but the cause of death was listed as cardiac arrhythmia. Which cranial nerve serves both the rectum and the heart? How could the normal function of that nerve have contributed to his death?

The vagus nerve (cranial nerve X) serves both the heart and the rectum. Stimulation of the vagus can lead to cardiac arrhythmias. If Elvis had an impaction, that may have led to vagal nerve stimulation, an abnormal heart rhythm, and in combination with his already unhealthy diet, an infarction.

~Some bacteria produce a toxin that causes a flaccid paralysis. Other bacteria produce a toxin that causes all of the skeletal muscles to contract at the same time. How might these toxins cause their effects?

A flaccid paralysis could be caused by a couple of mechanisms, most notably by the toxin molecule attaching to the Ca+ binding sites on the actin fibers. This would block the troponin/tropomyosin from being able to uncover the actin binding sites for the myosin heads. It could also block the ATP binding sites on the myosin heads. No ATP binding, no muscle contraction.

A tetanus paralysis could be caused by a toxin molecule blocking the action of the Ca+ pumps on the sarcoplasmic reticulum. This would lead to an excess of calcium in the muscle fibers, and so long as ATP is available, continuous contraction. It could also act as an acetylcholine synergist and continually stimulate the muscle cells through the motor end plates.

~In 1848, a railroad worker named Phineas Gage was seriously injured during an explosion on the job. A tapered metal rod ranging from 0.25 inches to 1.25 inches in diameter and over 3 feet long entered his skull just under his left cheek bone and exited through the top of his skull. The rod was found over twenty feet away. Amazingly, Gage lived even though he suffered massive damage to the left front of his brain. His personality and intellectual abilities ...