Case Study 1: Death by the Thousands

Headlines in French newspapers shouted out the shocking findings when thousands of Paris residents returned
home near the end of August 2013 from their Summer Holiday. The morgues were full of dead bodies and an
unpleasant stench greeted many Parisians as they entered apartment buildings. Even indoor skating rinks were
used to store bodies that the funeral homes could not contain.

What was the cause of the carnage? A terrorist attack? A new outbreak of bubonic plague? No, it was
something a bit more mundane, but potentially just as deadly, especially if you were elderly and lived alone.
One of the longest heat waves on record roasted Western Europe during the first three weeks of August 2013,
leading to over 15,000 deaths in France alone. Most of these individuals died from complications of something
called heat stroke. Read through chapter 1 of your text and be prepared to answer the following questions
during your week 1 discussion section.

1. Why are sustained temperatures above the normal body set point dangerous to a person’s health?
Sustained temperatures above the normal body set point are dangerous to a person’s health because it will cause
profuse sweating, decreasing extracellular fluid levels. As extracellular fluid levels decrease, blood pressure
also decreases, causing the ability of the heart to pump blood sufficiently up to the brain to be poor. Without
sufficient blood flow, cells in the brain begin to malfunction, potentially causing heatstroke. In addition, profuse
sweating also impacts the balance of ions in the body fluids, specifically Na+, K+, and C-, which also affects
the brain cells. Therefore, homeostatic balance of the ions in body fluids are also essential for normal heart and
brain function

2. What are some of the physiological adaptations the body uses to rid itself of excessive heat?
Some of the physiological adaptations that the body uses to rid itself of excessive heat are dilation of the blood
vessels and perspiration.

3. What adverse outcomes may result from maintaining these adaptations over an extended period of time (days
or even weeks)?
Adverse outcomes that may result from maintaining these adaptations over an extended period (days or even
weeks) are huge amounts of water loss through profuse sweating over an extended period of time and extremely
low blood pressure that causes insufficient amounts of blood to be pumped up to the brain.

4. Other than attempting to cool the body, what other measures should be taken to help a person who has had a
heat stroke, reestablish homeostasis? What problems may result from such treatments?
Other measures that should be taken to help a person who has had a heat stroke to reestablish homeostasis is
making them drink lots of water. But drinking too much water can be a problem as hyponatremia can occur
where Na+ concentrations in the blood get too diluted, causing medical complications such as seizures, coma,
and even death.

5. Describe the elements of a negative feedback loop that plays a role maintaining body temperature.

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A negative feedback loop system is a feedback system in which an increase or decrease in the variable being
regulated brings about responses that tend to move the variable in the direction opposite (“negative” to) the
direction of the original change. In the example of maintaining body temperature, an increase in body
temperature would result in responses that tended to decrease the body temperature while a decrease in body
temperature would result in responses that tended to increase the body temperature, both times moving the body
temperature back to its original value and thus maintaining body temperature.

6. Which in theory would be more effective in preventing a rise in body temperature: a feedback or feedforward
mechanism? Explain.
In theory, a feedforward mechanism would be more effective in preventing a rise in body temperature as it is a
system in which changes in regulated variables are anticipated and prepared for before they actually occur.
When outside temperature increases, temperature-sensitive neurons detect the change, relay the signal to the
brain, and the brain sends signals to different parts of the body that results in responses that cause heat loss and
decreased heat production. Through feedforward mechanisms, compensatory thermoregulatory responses are
activated before the hotter outside temperature can cause the body temperature to increase.

7. What is a physiological integrating center and what role does it play in maintaining homeostasis? What
region of brain is believed to be the location of the integrating center that regulates body temperature?
A physiological integrating center is a component of a biological regulatory system that receives a signal from
the receptor(s) and compares it to the send point before sending it to the effector, causing a change in activity
that works to bring balance back to the system. It plays a major role in maintaining homeostasis as it integrates
numerous bits of information that ultimately leads to the response that maintains homeostasis. The region of the
brain believed to be the location of the integrating center that regulates body temperature is the hypothalamus.
The hypothalamus compares the signal and information received from afferent sensory neurons to the body
temperature set point and sends signals through the efferent pathways to, for example. causes contraction of
skin blood vessels to decrease blood flow, and thus decrease heat loss to maintain the body temperature and stop
its decrease from the set point.

8. List the organ systems that are known to be involved in the process of temperature regulation.
The organ systems known to be involved in the process of temperature regulation are the nervous system,
muscular system (smooth muscle and skeletal muscle), circulatory system, and endocrine system.