Physiology Week 1

Question 1

Diffusion is __________. This is the result of _______.

Answer 1

1. The movement of particles down a concentration gradient.

2. RANDOM kinetic movement of particles.

Question 2

Define Flux and Force:

Answer 2

Flux: The movement of particles
Force: The Chemical Energy Gradient

Question 3

What does the relationship of displacement to the square root of time tell us about diffusion?

Answer 3

Since it implies that over longer periods of time, gradually less and less displacement will be seen, we cannot rely on diffusion to achieve rapid displacement of particles over time. We MUST utilize other resources like blood flow/pressure to drive the concentration gradient.

Question 4

List the 3 most important factors that drive flux:

Answer 4

1. Magnitude: Of the Conc. gradient (delta C)
2. Surface Area: Available for flux
3. Distance: Over which the delta C exists (the membrane)

Question 5

How is force related to flux?

Answer 5

PROPORTIONALLY. Meaning an increase in one will mean a proportional increase in the other.

Question 6

What is the Diffusion Coefficient:

Answer 6

A descriptor of the EASE with which diffusion of a particle down a conc. gradient will take place.

Question 7

Give the equation for Fick’s 1st Law Of Diffusion:

Answer 7

J = (-DcPcA)/X x (C1-C2)
or
J = -P x (c1-c2)/X

Question 8

Give the units for each variable in Fick’s 1st Law of Diffusion:

Answer 8

Flux (J)= moles/cm^2 x S
Conc. Gradient (Delta C)= moles/cm^3
Distance (Delta X)= 1/cm
Diffusion Coefficient (D)= cm^2/S

Question 9

The diffusion coefficient is also referred to as ________.

Answer 9

Permeability

Question 10

What 4 factors determine the overall permeability coefficient of the diffusion of a substance?

Answer 10

1. Diffusion Coefficient
2. Partition Coefficient
3. Area
4. Distance

Question 11

What does a HIGHER partition coefficient mean in terms of Fick’s Law?

Answer 11

1. The HIGHER the partition coefficient, the greater the concentration gradient, and therefore the greater the flux.

Question 12

The diffusion coefficient also represents _______.

Answer 12

Conductivity

Question 13

Extracellular and vascular fluid is generally rich in ________ fluid, while intracellular fluid is rich in _______ fluid.

Answer 13

1. NaCl

2. KCl

Question 14

How are mM converted into mOsm and mEq?

Answer 14

1. mOsm are calculated by taking the mM value and multiplying by the number of particles it will dissociate into.
2. mEq are calculated by taking the mM value and multiple by the charge of the ion

Question 15

All solutions start out with ___________, and because of the Na+/K+-ATPase, _______.

Answer 15

1. Equivalent charge

2. The concentration gradient remains intact to correct any charge in charge

Question 16

Vm (membrane potential) is set by __________.

Answer 16

The ion with the highest permeability

Question 17

Explain the difference between Vm and Eq?

Answer 17

Vm (membrane potential) is a measured value of the cell that reflects the open and closed variety of ion channels present throughout the membrane.
The Eq (equilibrium potential) of an ion is a calculated value that reflects the ideal membrane potential for that ion to be in equilibrium with respect to its concentration inside and outside of the cell.

Question 18

Almost all secretion is driven by _______ and almost all absorption is driven by _______.

Answer 18

1. Chloride

2. Sodium

Question 19

The trans-epithelial potential during secretion is _______ in the apical domain, while during absorption it is ________ in the apical domain.

Answer 19

1. Negative

2. Also Negative