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Homeostasis Review Questions
1. Heat exhaustion caused by a person’s exposure to heat can result in weakness or collapse. It usually involves a
decrease in blood pressure. Explain why the homeostatic adjustment to heat can cause a drop in blood pressure.
2. During lactation (milk production), the suckling by the baby stimulates the production of oxytocin, which in turn
causes contraction of smooth muscle surrounding the milk duct, causing milk to flow. The flow of milk increases
the suckling by the baby and more oxytocin is produced.
a. Identify the type of feedback system described above.
b. What would end the feedback loop?
c. Draw a feedback loop to represent these processes.
3. Drugs such as ecstasy, interfere with the feedback mechanism that helps maintain a constant body temperature.
Explain why these drugs are dangerous.
4. Describe the three main processes involved in urine formation.
5. The following is a random list of processes that occur in the formation and excretion of urine once the blood has
entered the kidney. Place these processes in the correct order.
i. Urine is stored in the bladder
ii. Blood enters the afferent arteriole
iii. Fluids pass from the glomerulus into Bowman’s capsule
iv. Urine is excreted by the urethra
v. Sodium ions, glucose and amino acids are actively transported from the nephron
vi. Urine passes from the kidneys into the ureters
6. Complete the table of kidney diseases and their treatments:
Kidney Disease
Diabetes mellitus
Diabetes insipidus
Cause
Lack of insulin production
Effects
Glucose in urine will
cause dehydration
Treatment
ADH provided by
injection
Bright’s Disease
Kidney stones
7. Draw and label a negative feedback system for a home heating and cooling system. Include the following in your
diagram: furnace, air conditioning unit, thermostat, coordinating centre and regulators.
8. Fluids were drawn from different areas of the nephron. The solutes in the fluid were measured and the results
are presented in the chart below. Analyse the results following and answer the accompanying questions:
Solute
Bowman’s Capsule
Glomerulus
Loop of Henle
Collecting Duct
Protein
0
0.8
0
0
Urea
0.05
0.05
1.50
2.00
Glucose
0.10
No data
0
0
Chloride
0.37
No data
No data
0.6
Ammonia
0.0001
0.0001
0.0001
0.04
Substance X
0
9.15
0
0
a. Which of the solutes was not filtered into the nephron? Explain your answer.
b. Predict whether glucose would be found in the glomerulus and provide reasons for your prediction.
c. Why do urea and ammonia levels increase after filtration occurs?
d. Is it correct to say that veins carry blood with high concentrations of waste products and arteries carry
blood with high concentrations of nutrients? Explain?
e. Compare the blood found in the renal artery and venal vein with respect to urea and glucose.
9. Athletes now undergo random urine testing for drugs. From your knowledge of excretion, describe the pathway
of substances such as drugs through the excretory system from the time they enter the blood stream until they
are excreted in the urine. Be sure to include mention of the blood vessels, the parts of the nephron and the
urinary structures that they pass through.
10. A lab experiment was conducted to determine the effect of thyroxine on metabolic rate. Four groups of adult
male rats were used. All the groups were maintained in similar environments, designed to provide maximum
physical activity. Each group was supplied with adequate water and one of the following diets.
Diet A: food containing all essential nutrients
Diet B: food containing all essential nutrients and an extract of thyroxine
Diet C: food containing all essential nutrients and a chemical that counteracts the effects of thyroxine
Diet D: food containing all essential nutrients, except iodine
The results of the experiment are as follows:
Group
Average Initial Mass (g)
1 (Diet A)
2 (Diet ?)
3 (Diet ?)
4 (Diet ?)
310
320
318
315
Average mass 2 weeks after
treatment (g)
312
309
340
400
Final average oxygen
consumption (mL/kg/min)
4.0
10.1
2.7
2.0
a. Formulate a hypothesis for this experiment.
b. Which group was most likely used as the control? Explain your answer.
c. Diet B was most likely fed to which group? Explain.
d. Which group was Diet D most likely fed to? Explain.
11. Explain the advantage of elevated blood sugar and blood pressure in times of stress.
12. A number of lab experiments were conducted on mice. The endocrine system of mice is similar to that of
humans. Brief summaries of the procedures are provided below:
#
1
Procedure
Gland removed
2
3
4
Hormone injected
Blood flow from the posterior pituitary reduced
Hormone injected
a.
b.
c.
d.
Observation
Urine output increased
Sodium ion concentration in urine increased
ACTH level increased in blood
Blood glucose levels decreased
Urine production increased
Glycogen converted to glucose in the liver
Blood glucose increased
In procedure 1, identify the gland that was removed and explain why the levels of ACTH increased.
In procedure 2, identify the hormone that was injected and explain why blood-glucose levels decreased.
In procedure 3, identify the hormone that was affected and explain why urine production increased.
In procedure 4, identify the hormone that was injected and explain why blood glucose levels increased.
13. Briefly describe the function of the following parts of a neuron: dendrites, myelin sheath, Schwann cells, cell
body and axon.
14. What changes take place along a nerve cell membrane as it moves from a resting potential to action potential to
a refractory period?
15. Use what you have learned about threshold levels to explain why some individuals can tolerate more pain than
others.
16. Use what you know about the transmission of nerve impulses to formulate a hypothesis about how local
anaesthetics work (ie: the dentist freezing your gums before filling a cavity)