TJ guide

Question 1

What types of molecules can travel across a membrane unaided?

Answer 1

Small uncharged (e.g. O2 and CO2)

Question 2

What is Fick’s Law?

Answer 2

Net Flux = J = DA(∆C)/∆x

D = diffusion coefficient = kT/6πrn ~ 1/rn
n = viscosity

A = surface Area
∆C = differences in solute conc. 
∆x = distance

Question 3

How can fick’s law be used to explain why lung collapse and edema leads to reduced oxygen in the tissues?

Answer 3

• lung collapse - A decreases meaning a lower net flux of oxygen.
• Edema - swelling increases the volume in the intersitial space which means oxygen has to diffuse further to get to the tissues when coming from the capillaries.

Question 4

How are amino acids transferred into the cell?

Answer 4

Symport with Na+

Question 5

How is Ca2+ imported into the cell?

Answer 5

Antiport with Na+

Question 6

What are the 4 types of gating mechanisms?

Answer 6

1. Voltage gated
2. Ligand Gated
3. Voltage-Ligand Gated
4. Mechanosensitive

Question 7

What is net ion movement proportional to?

Answer 7

ConductanceOpen time of channelDriving force

Question 8

What is the simplified nernst eqn?

Answer 8

v = 60/z log [out]/[in]

Question 9

Explain in terms of the electrical and chemical potential why there is a net driving force to push K+ out of the cell under normal conditions.

Answer 9

In the cell the resting potential is -60mV
The chemical gradient for K+ is +88 mV,
Therefore there is

Question 10

T or F: graded potentials propagate.

Answer 10

False

Question 11

Describe all underlying details of an action potential.

Answer 11

1. Voltage-gated Na activation gates are closed and inactivation gates are open
2. Na rushes in through activation gates
3. Permeability to Na increases causing more Na to rush in and THRESHOLD is reached
4. up to 60mV reached as Na+ reaches full permeability
5. Inactivation gates close slowly ~.5 ms due to depolarization
6. Potassium channels open slowly (~1 ms later) due to depolarization causing K+ channels to open
7. K+ channels close

Question 12

T or F: Time and space constants apply to action potentials?

Answer 12

False, they apply to graded potentials.

Question 13

What is the space constant?

Answer 13

lamba = sqrt(dRm/4Ri)

Question 14

What is the time constant?

Answer 14

Tau = RmCm

Question 15

Is a compound action potential actually an action potential?

Answer 15

No, it measures the time and magnitude of electrical activity traveling through the heart EKG, nerve EMG, or brain EEG

Question 16

What type of disease results in a slower propagation of action potential?

Answer 16

Neurogenic, potentials are still normal height though

Question 17

What type of effect is seen in compound action potentials in myogenic diseases?

Answer 17

Same time, but reduced height

Question 18

TEA (tetraethylammunium) effect

Answer 18

Blocks K+ Channels (Slow repolarization, no hyperpolarization)

Question 19

TTX (tetrodotoxin)

Answer 19

(pufferfish) Blocks Na+ channels (no action potential)

Question 20

Rickets

Answer 20

• No Ca2+ to bind to inactivation domain
• Gate threshold is lowered
• sporactic opening leads to siezures and cramps

Question 21

Local Anesthetics

Answer 21

• e.g. novocaine, cocaine

- bind to Na+ channels and inhibit them from opening (fewer APs)

Question 22

Tingling Ears

Answer 22

• less blood flow, no O2 or ATP
• No ATP then no Na/K ATPase
• Less intracellular K+ = depolarized cell
• More APs

Question 23

Hyperkalemia

Answer 23

• Slight depolarization causes closure of the inactivation gates
• Prevents action potential from happening

Question 24

What type of proteins are responsible for the organization of microtubule protofilaments?

Answer 24

MAPS

Question 25

T or F: in the cell microtubules can disassemble from the - end?

Answer 25

FALSE

Question 26

Dyenins

Answer 26

Use ATP

Direct Golgi toward Nuc.

Question 27

Kinesins

Answer 27

Use ATP

Direct ER to periphery