Lec 5 & 6

Question 1

A small number of ions will change the Vm by Alot!

T or F?

Answer 1

True

Question 2

What is defined as “a measurement of cell voltage while controlling applied current “ ?

Answer 2

Current Clamp

Question 3

What is defined as “a measurement of cell currents hwile controlling cell voltage “ ?

Answer 3

Voltage Clamp

Question 4

Which “Clamp” experiment is being described?

When current is injected, capacitance causes a delay in voltage response in order to charge the membrane.

Answer 4

Current Clamp

Question 5

Capacitance (in Voltage Clamp) depends on what two variables?

Answer 5

size of the cell

and

size of voltage change

Question 6

Which “Clamp” experiment is being described?

When cell voltage ‘steps up’ there is a transient burst of current.

The equal but opposite current that occurs when the membrane is returned to original voltage is dissipated.

Answer 6

Voltage Clamp

Question 7

Which 2 people discovered the Patch Clamp Technique?

Answer 7

Erwin Neher + Bert Sakmann

Question 8

What “enables recordings of the opening and closing of individual ion channels” ?

*high resistance seal*

Answer 8

Patch Clamp Technique

Question 9

What are the 4 types of Patch Clamp Configurations?

Answer 9

1. cell-attached
2. whole-cell patch
3. inside-out excised patch
4. outside-out excised patch

Question 10

What is “The cell-attached patch clamp technique” ?

Answer 10

Channels remain on the cell surface - single channel recording

Question 11

What is “The whole-cell patch clamp technique” ?

Answer 11

enables recording of all currents on the cell membrane

(broken open to cell membrane)

Question 12

What is “The inside-out excised patch clamp technique” ?

Answer 12

the cytoplasmic side of the channel is facign into the bath solution.

** makes it very easy to change the internal concentration of a ligand

Question 13

What is “The outside out-out excised patch clamp technique” ?

Answer 13

the extracellular side of the channel is facing out into the bath.

** makes it very easy to change the concentrations of an external ligand.

Question 14

The period of time during an action potential when “a second response is not possible regardless of strength or duration of stimulus” is called …?

Answer 14

Absolute Refractory Period

Question 15

The period of time during an action potential when “a second response can be elicited but at a greater “cost” (strength/duration) is called…?

Answer 15

Relative Refractory Period

Question 16

The diameter of a Giant squid axon is around ____ micrometers

Where as the mammalian axon is around 2 micrometers.

Answer 16

800 nanometers

Question 17

The amplitude of an action potential depends on the external ____ concentration.

a. K+
b. Na+
c. Cl-
d. Ca²⁺

Answer 17

answer: B Na+

Question 18

Resting membrane potential (Vm) is changed ______ (little or alot) by Na+ concentrations.

Answer 18

Vm is changed very little by Na+

Question 19

Resting membrane potential (Vm) is changed ______ (little or alot) by K+ concentrations.

Answer 19

Vm depends strongly on the K+

Question 20

1. In a Current-Voltage relationship graph, the early current is a potential difference created by which ion?
2. how does it behave as the membrane potential becomes more positive?

Answer 20

Na+

Sodium current reverses to outflow and positive current at its reversal potential (around +50 mV)

Question 21

1. In a Current-Voltage relationship graph, the late current is a potential difference created by which ion?
2. how does it behave as the membrane potential becomes more positive?

Answer 21

K+

K+ curve continues to increase as the driving force gets larger

Question 22

What ion blocker(s) are used to inhibit early current?

Answer 22

TTX - tetrodotoxin

STX - Saxitoxin

Question 23

What ion blocker(s) are used to inhibit late current?

Answer 23

TEA - tetraethylammonium

Question 24

Which ion Blocker (used in early and late currents) resides in pufferfish and is 1,200x more poisonous than cyanide?

Answer 24

TTX tetrodotoxin

Question 25

When channels are assumed to always be fully open the current through them is linear or “ohmic”

T or F?

Answer 25

True

Question 26

Conductance changes with voltage when channels are assumed to always be fully open.

T or F?

Answer 26

False

Conductance does not change with voltage when channels are assumed to always be open.

Question 27

The opening of Na and K channels depends on resistance and conductance.

T or F?

Answer 27

False

depends on Voltage!