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General Physiology
Homework #3
Due via email on November 16, before 6pm.
1. (5 points) Colostrum, the first milk that a mother produces, contains an abundance of antibodies,
large protein molecules that provide immediate immunity. These maternal antibodies help protect
breast-fed infants from infections until the babies are capable of producing their own antibodies.
By what means would you suspect these maternal antibodies are transported across the cells
lining a newborn’s digestive tract into the bloodstream? Explain your choice.
2. (5 points) Given the following solutions, which has the lowest water concentration? Which two
have the same osmolarity? (Solution A has 20 mM glucose, 30 mM urea, 150 mM NaCl, and 10
mM CaCl2 all combined in the solution) Explain your answer.
Concentration (mM)
Solution
A
B
C
D
Glucose
20
10
100
30
Urea
30
100
200
10
NaCl
150
20
10
60
CaCl2
10
50
20
100
3. (5 points) Why will inhibition of ATP synthesis by a cell lead eventually to a decrease and,
ultimately, cessation in secondary active transport?
4. (5 points) Neurons are treated with a drug that instantly and permanently stops the Na+/K+
ATPase pumps. Assume for this question that the pumps are not electrogenic. What happens to
the resting membrane potential immediately and over time?
5. (5 points) If the enzyme acetylcholinesterase were blocked with a drug, what malfunctions would
occur in the heart and skeletal muscle?
6. (5 points) A person has received a severe blow to the head but appears to be all right. Over the
next weeks, however, he develops loss of appetite, thirst, and sexual capacity, but no loss in
sensory or motor function. What part of the brain do you think may have been damaged?
7. (5 points) If the transverse tubules of a skeletal muscle are disconnected from the plasma
membrane, will action potentials trigger a contraction? Give an explanation.
8. (5 points) In the laboratory, if an isolated skeletal muscle is placed in a solution that contains no
calcium ions, will the muscle contract when it is stimulated (1) directly by depolarizing its
membrane, or (2) by stimulating the nerve to the muscle? What would happen if it were a smooth
muscle?
9. (5 points) What conditions will produce the maximum tension in a skeletal muscle fiber?
10. (5 points) What is the advantage of dual innervation of many organs by both branches of the
autonomic nervous system?