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Sunday, June 26, 2016

Coursera Introduction to Physiology - Week 1 - Transporter, Channel and Homeostasis

1. Cells may communicate with one another by:

A. transferring signal molecules to adjacent cells through gap junctions.

B. local chemicals, called paracrines and autocrines

C. chemicals that act at a distance.

D. A, B, and C

2. How does drinking one liter of water affect the fluid compartments of the body?

A. There are no changes in either the ECF or ICF.

B. The ECF increases by one liter with no change in the ICF.

C. The ECF will increase by 500 ml and the ICF by 500 ml.

D. The ECF will increase by 333 ml and the ICF increases by 666 ml.

This is because the osmolarity of fluid has to stay constant.

3. Complete the following true statement. Negative feedback loops ______ the initiating stimulus and positive feedback loops _____ the initiating stimulus.

A. increase; increase

B. remove; increase

C. increase; remove

D. remove; remove

4. In the following situation, identify the components of the reflex loop.

You have finished the marathon in just under three hours. You are tired, sweating profusely, and start to drink Gatorade. After several minutes you are still tired but no longer sweating or thirsty.

A. Stimulus (sweating); response (drinking)

B. Stimulus (drinking); response (sweating)

C. Stimulus (running); response (drinking)

I was confused with this one - since drinking is an activity that we choose to do, not an automatic response. But after all, given the choices, only this one make sense anyway.

5. Which of the following exhibits a circadian rhythm that coincides with sleep-wake cycles?

A. Cortisol secretion by adrenal glands

B. Acid secretion by stomach

C. Growth hormone secretion by pituitary

D. A and C

6. When plasma water is lost but electrolytes are retained, then:

A. osmolarity of the ECF falls

B. osmosis moves water from the ICF to the ECF

C. both the ICF and the ECF become more dilute

D. there is an increase in the volume of the ICF

Remember plasma is ECF

7. Which of the following solutions has the lowest concentration of water?

Solution   mM glucose   mM NaCl   mM CaCl2

A.         20           40       50

B.         20           50       80

C.         20           50       60

A. Solution A. It is 250 mOsM

B. Solution B. It is 360 mOsM

C. Solution C. It is 300 mOsM

The higher the concentration of solute, the lower the concentration of water.

8. Which of the following solutions is isotonic to a cell that is 300 mOsM?

Solution   mM glucose   mM NaCl   mM CaCl2

A.         20           40       50

B.         20           50       80

C.         20           50       60

Solution ______ is isotonic to a cell with an ICF of 300mOsM.

A. Solution A

B. Solution B

C. Solution C

The tonicity is computed using the number of particles of non-penetrating solute divided by the volume. We have 1 particle for glucose, 2 particles for NaCl and 3 particles for CaCl2

Therefore the tonicity are:
A) 20 + 2 x 40 + 3 x 50 = 250 mOsM
B) 20 + 2 x 50 + 3 x 80 = 360 mOsM
C) 20 + 2 x 50 + 3 x 40 = 300 mOsM

9. A neuronal cell with an ICF of 300mOsM will swell in which of the following solutions?

Solution   mM glucose   mM NaCl   mM CaCl2

A.         20           40       50

B.         20           50       80

C         20           50       60

A. Solution A which is 250 mOsM

B. Solution B which is 360 mOsM

C. Solution C which is 300 mOsM

Remember lower osmolarity, the higher the concentration of water. And therefore water moves from Solution A into the neuron because of the concentration gradient of water.

10. How does the addition of 10mM urea affect solution A?

Solution   mM glucose   mM NaCl   mM CaCl2

A.         20           40       50

B.         20           50       80

C         20           50       60

A. Increase the osmolarity by 10 mOsM

B. Increase the tonicity by 10 mOsM.

C. Increase the osmolarity and tonicity by 10 mOsM.

Urea can penetrate plasma membrane and therefore not included in the tonicity calculation.

11. Channels and symporters are alike because they facilitate diffusion of effective solutes across membranes as well as:

A. exhibit solute specificity

B. use ATP

C. exhibit saturation and solute specificity

D. exhibit saturation, solute specificity and use ATP

12. Channels are gated by which of the following?

A. ligands

B. voltage

C. tension (mechanical)

D. A and B

E. A, B and C

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