CHAPTER 25 Test Your Knowledge
DRIVING QUESTION 1
How are the bodies of living organisms organized?
By answering the questions below and studying Infographic 25.1, you should be able to generate an answer for the broader Driving Question above.
KNOW IT
Compare and contrast anatomy and physiology.
Anatomy is the study of the structure of living organisms. Physiology is the study of how organisms function, particularly with respect to maintaining homeostasis.
Organize the following terms on the basis of level of structure, from the simplest (1) to the most complex (4).
_________________ Small intestine
_________________ Mucus-secreting cell of the small intestine
_________________ Digestive system
_________________ The layer of muscle that contributes to the function of the small intestine
(1) mucus-secreting cell of the small intestine; (2) the layer of muscle that contributes to the function of the small intestine; (3) small intestine; (4) digestive system
USE IT
An emergency room doctor setting a complex bone fracture is relying primarily on knowledge of
a. anatomy.
b. physiology.
c. thermoregulation.
d. homeostasis.
e. osmoregulation.
a
Is a personal trainer who works with clients to help them lose weight through a combination of diet and exercise focusing primarily on anatomy or physiology? Explain your answer.
The trainer is focusing on physiology. Both diet and exercise work through a variety of metabolic processes and require homeostatic mechanisms (e.g., body temperature regulation, blood-sugar regulation, ATP production, lipid storage vs. lipid utilization, heart rate, breathing rate).
Why is the heart considered an organ and not a tissue?
Because the heart is made up of more than one tissue type, all working together to maintain heart function. The heart contains nervous tissue and muscle tissue as part of its structure.
DRIVING QUESTION 2
How do humans and other organisms regulate body temperature?
By answering the questions below and studying Infographics 25.2, 25.3, and 25.4, you should be able to generate an answer for the broader Driving Question above.
KNOW IT
What is homeostasis?
The maintenance of a relatively stable internal environment, even when the external environment changes.
How does brown fat contribute to thermoregulation in bats?
a. by providing insulation to retain heat
b. by providing a highly vascularized tissue to release heat to the environment
c. by generating heat through shivering
d. by generating heat via cellular respiration in specialized mitochondria
e. b and d
d
Describe the feedback loop involved in thermoregulation in cold conditions. Use the following terms in your answer: hypothalamus, sensor, muscle, effector, low body temperature, normal body temperature.
In cold conditions, sensors will detect the low body temperature and send a signal to the hypothalamus. The hypothalamus will send signals to effectors (including muscles and blood vessels), which will exert their effects (e.g., shivering and vasoconstriction), bringing about a normal body temperature.
USE IT
How could damage to the hypothalamus prevent shivering even if the core body temperature drops dramatically?
If the hypothalamus is damaged, it may not be able to receive information from the sensors or send information to the effectors. In either case, the muscles will not receive the signal to shiver, and in the absence of any intervention body temperature will remain low.
Why is glucagon released as part of the response to a drop in body temperature?
One of the responses to a drop in body temperature is shivering. Muscles require energy in order to shiver. Glucagon acts on the liver to promote the breakdown of glycogen and release of glucose (which serves as fuel) into the blood, providing circulating glucose for muscles. Similarly, glucagon acts on skeletal muscle to promote the breakdown of glycogen to enable the muscle to continue to shiver.
Name two or three physiological responses that could help the body dissipate heat during exertion on a hot day. For each mechanism that you propose, explain how it would dissipate heat.
Sweating: as sweat evaporates, it cools the body. Vasodilation brings more blood flow to the surface of the skin, allowing some heat to dissipate from the body.
DRIVING QUESTION 3
What physiological systems are regulated by homeostatic feedback loops?
By answering the questions below and studying Infographics 25.5 and 25.6, you should be able to generate an answer for the broader Driving Question above.
KNOW IT
What internal signals are associated with dehydration?
a. high osmolarity
b. low blood volume
c. low blood pressure
d. all of the above
e. a and b
d
People who are severely dehydrated produce ____________ urine that is ____________.
a. a high volume of; highly concentrated and dark in color
b. a high volume of; dilute and light in color
c. a low volume of; highly concentrated and dark in color
d. a low volume of; dilute and light in color
e. a normal volume; a normal color (neither very light nor very dark)
c
Insulin is released from the ______________ in response to ______________.
a. pancreas; elevated blood sugar
b. pancreas; low levels of blood sugar
c. hypothalamus; elevated blood sugar
d. hypothalamus; low levels of blood sugar
e. pituitary; signals from the hypothalamus
a
USE IT
What conditions might cause high levels of insulin in the bloodstream? What events would follow?
High insulin will occur in response to high blood sugar—for example after eating a carbohydrate-rich (particularly sugar-rich) meal. The pancreas releases insulin into the blood in response to high blood sugar. Insulin acts on target cells, signaling them to take up sugar from the blood, thus lowering blood sugar. As the blood sugar drops, the pancreas stops releasing insulin, causing the insulin levels to drop as well.
Tibetan Sherpas, many of whom serve as guides and rescuers on Everest, often do not require bottled oxygen to reach the summit. Why might Tibetans, who have lived at high elevations for many generations, have an easier time than others with hypoxia? (Think about both short-term and long-term changes.)
In the short term, Sherpas individually adapt to low O2 levels, producing higher numbers of red blood cells in response to that environmental factor. In the longer term, the population has likely adapted. Evolutionary adaptations to high altitude and low O2 could include lung structure (increased lung volume) and the capacity of individual red blood cells to carry O2 (because of altered hemoglobin).
MINI CASE
Hypertension (high blood pressure) has been diagnosed in a 65-year-old woman. She needs medication that will return her blood pressure to normal (and safe) levels. Her doctor tells her that there are two main categories of drugs for hypertension: thiazides, a type of diuretic, and ACE inhibitors, which help relax blood vessels and prevent their constriction. Explain how both of these could reduce blood pressure.
A diuretic (often called a “water pill”) causes excess water from the blood to be excreted by the kidneys. Reducing the volume of the blood (through water removal) causes the pressure in the blood vessels to decrease. ACE inhibitors relax the blood vessels and prevent them from constricting. This will reduce the pressure applied to the blood in the vessels, dropping the blood pressure.
INTERPRETING DATA
Jonas and Jennifer have abnormal fasting glucose levels in their blood. They each had a blood test to measure the levels of insulin in their blood (also measured after fasting). Their blood values for both glucose and insulin are shown in the table below. From the data shown, is Jonas or Jennifer more likely to have type 2 diabetes (which is characterized by an inability of cells to respond to insulin)? Which of them is more likely to have type 1 diabetes (which results from a failure of insulin production)? Be sure you can explain all of their blood test results.
As Jonas has high blood sugar but low insulin, he likely has type 1 diabetes. Normally, high blood sugar will cause the pancreas to release insulin into the blood, but in type 1diabetes the pancreas cannot produce insulin, so there is no signal to the cells to take up sugar from the blood—elevated blood sugar results. As Jennifer has high blood sugar and high insulin, she appears to have type 2 diabetes. Her pancreas is appropriately releasing insulin in the presence of high blood sugar. But, the high insulin should be reducing the blood sugar. The fact that she has high insulin and high blood sugar indicates that her cells are not responding appropriately to the insulin.
BRING IT HOME
The U.S. National Park Service has to rescue stranded hikers, often at great expense. Do you think that hikers’ level of preparation should be a factor in determining whether or not they should bear the cost of their rescue? What factors would you consider to determine whether or not a hiker was adequately prepared? Give a physiological reason for each factor that you propose.
There will likely be many opinions about the financial liabilities of stranded hikers and their level of preparedness. In terms of preparing appropriately (particularly for unexpected weather), there are many things that hikers can do. For example, hikers should carry more water than they think they will need to prevent dehydration (especially if they end up hiking longer than anticipated or in hot climates). They should have sufficient clothing to prevent hypothermia if the weather becomes cold. Similarly, if the trek is in sunny environments (hot or cold), sunscreen and sun-protective clothing should be included, to prevent painful sunburns that may limit the ability to continue the hike (and increase the risk of being stranded). Hikers should have sufficient food (particularly carbohydrate-rich food) to maintain blood-sugar levels if they deplete their glycogen stores. If they are hiking at high altitude, preparation should include acclimatization before starting the hike.