A Case on Nervous Tissue
Case Study One – Bad Fish: A Case on Nervous Tissue
One evening during a recent trip to Indonesia, Dr. Marshall Westwood sat down to a meal of puffer fish and rice. Within an hour of returning to his hotel room, Dr. Westwood felt numbness in his lips and tongue, which quickly spread to his face and neck. Before he could call the front desk, he began to feel pains in his stomach and throat, which produced feelings of nausea and eventually severe vomiting.
Fearing that he had eaten some “bad fish” for dinner, Dr. Westwood called a local hospital to describe his condition. The numbness in his lips and face made it almost impossible for him to communicate, but the hospital staff managed to at least understand the address he gave them and they sent an ambulance. As Dr. Westwood was rushed to the hospital, his breathing became increasingly labored.
The patient presented in the ED with diaphoresis, motor dysfunction, paresthesias, nausea, and an ascending paralysis that started in his legs and spread to the upper body, arms, face, and head. The patient was cyanotic and hypoventilating. Within 30 minutes of presenting in the ED, Dr. Westwood developed bradycardia with a BP of 90/50 mmHg. Atropine was administered in response to the bradycardia. Intravenous hydration, gastric lavage, and activated charcoal followed a presumptive diagnosis of tetrodotoxin poisoning that was based on the clinical presentation in the ED. Five hours after treatment, the following vital signs were noted:
• BP 125/79 mmHg
• HR 78 bpm
• Oxygen saturation: 97% on room air
After discussing his case with his physician, he learned that he had probably been the victim of puffer fish poisoning. The active toxin in the tissues of this fish is a chemical called tetrodotoxin (TTX). Tetrodotoxin is in a class of chemicals known as neurotoxins because it exerts its effects on neurons. The specific action of tetrodotoxin is that it blocks voltage-gated sodium ion channels.
-When nerve cells are at rest, there is an unequal amount of positive and negative charges on either side of a nerve cell membrane. This charge difference creates an electrical potential. Describe how the resting membrane potential (resting potential) is generated.
-What would happen to a neuron if it was exposed to tetrodotoxin? Be specific regarding its effect on the ability of a neuron to communicate.
Case Study 2 – “My Leg is on Fire”: A Case Study on Spinal and Peripheral Nerve Anatomy
Sarah Mitchell is a 68-year-old female who is normally healthy. However, about five days ago she began to feel very fatigued and started to experience a burning and tingling sensation on her right thigh.
You ask to see the area and upon visual inspection you notice 3–4 small, red, swollen areas with vesicles on the posterior aspect of her right thigh. She describes the pain to you, saying “it feels like the back of my leg is on fire and it hurts so bad.” She denies being exposed to any excessive heat sources, any changes in her diet, and any changes in the type of body soap, lotion, or laundry detergent she is using. All other physical findings are within normal limits, but her oral temperature is 100.6˚F. She complains about being under a lot of stress for the past three months because she has been helping take care of her husband, who is in the end stages of Alzheimer’s disease. She has no known drug allergies, is a non-smoker, and attends a water aerobics class twice a week. You suspect she may be suffering from a particular viral infection, so you ask if she had chicken pox as a child. Sarah confirms that she had chicken pox and measles during childhood. Her answer confirms your suspicions that she is likely suffering from shingles (herpes zoster) due to varicella-zoster virus infection.
-Define the following terms, used in the case and also in associated questions.
-The virus infecting Sarah lies dormant in the dorsal root ganglion. What part of a neuron is located in the dorsal root ganglion? Does the dorsal root and its ganglion carry sensory input, motor output, or both?
-If Sarah had a viral infection that affected neuron function in the ventral root of the same spinal nerve, how would the signs and symptoms be different than those she has now?
Please include an introduction paragraph of both cases (just one) and answer the five questions.