Excitable Membranes and potential gradients

Question 1

What are the four factors that establish the cell membrane resting potential?

Answer 1

1. membrane permeability
2. solute concentration gradients
3. electrical conc gradients
4. active molecular pumps

Question 2

What does the Nerst equation assume to be zero?

Answer 2

Net flux

Question 3

What are fixed anions?

Answer 3

negatively charge large mol that cannot leave the inside of the cell and exert a net negative source on the inside of the cell

Question 4

Give an example of Donnan Equilibrium.

Answer 4

The net negative charge inside the cell pulls in K+ against its concentration gradient. At equilibrium the concentration of K+ is 20 times greater inside than outside.

Question 5

Three features of active molecular pumps

Answer 5

1. tansport can take place against a concentration gradient
2. Transport is selective
3. Use ATP

Question 6

WHat is transported where in the sodium potassium pump?

Answer 6

3 sodium of and 2 potassium in

Question 7

The charged ions moving through the electrolyte solution ie the cell membrane create a what?

Answer 7

constant current called a riogenic current

Question 8

What is electrotonis?

Answer 8

the natural electrical resting state of the cell

Question 9

What are the four physiological ions?

Answer 9

Na K Cl Ca

Question 10

Cell membranes high permeability to what ion?

Answer 10

K

Question 11

Cell membranes are not permeable to what ions?

Answer 11

Na Cl Ca

Question 12

Sodium and chloride are how many times more concentrated on the outside than inside?

Answer 12

10 times

Question 13

Calcium is how many orders of magnitude greater on the outside than inside?

Answer 13

2-7

Question 14

What is the resting membrane potential?

Answer 14

-60mV to -70mV

Question 15

What are the three types of tissue that have excitable membranes?

Answer 15

muscle
nervous
epithelial

Question 16

What are the two fundamental states of excitable membranes?

Answer 16

resting and active

Question 17

WHat does the Goldman adjustment take care of?

Answer 17

The Nerst equation for the trans membrane potential does not take into account all the ions in an excitable membrane. the Goldman adjustment specifically includes the permeability of Na and Cl and established the trans membrane potential as -60mV

Question 18

What is the primary ion involved in creating an action potential?

Answer 18

Na

Question 19

What is depolarization?

Answer 19

The complete reversal of charge of the inside to the outside of the cell from the effects of the membrane being permeable to Na for only a few microseconds.

Question 20

What does a Na equilibrium across the membrane establish?

Answer 20

an Action Potential

Question 21

Cll membranes designed to close quick or slow and what is this phenomenon known as?

Answer 21

ball and chain close fast!

Question 22

How is sodium permeability controlled?

Answer 22

When a nerve is stimulated and depolarization occurs the sodium channels are only open for a very short period of time and only a few ions are allowed to cross through and only a few are needed to create an action potential so that the nerve can repolarize faster!

Question 23

How does the membrane become permeable to sodium?

Answer 23

gated channels are opened

Question 24

what are the three types of gated channels?

Answer 24

ligand gated channels
voltage geted channels
mechanically gated channels

Question 25

What are mechanically gated channels?

Answer 25

The cell membrane is distorted and that deformation allows the Na to come in. Good in stretch receptors on skin or joints. pressure sensors too.

Question 26

What is the ligand gated channel?

Answer 26

Have specific receptors for certain types of molecules and when it comes in contact with that molecule the gate opens. Nerve Tracks

Question 27

What are voltage gated channels?

Answer 27

It is the flow of a charged molecule that creates the amperage. When there is enough flow of ions the voltage gate will open.

Question 28

What type of channel do we use the most?

Answer 28

voltage gated channels

Question 29

When Na flows through ligand gated channels what other gates are opened?

Answer 29

voltage gated channels by the flow of the charged molecules

Question 30

What is an action potential?

Answer 30

self propagating way of depolarization in a preferred direction.

Question 31

What cycle can illustrate the series of events that take place during a depolarization?

Answer 31

Hodgkin's Cycle

Question 32

What are the events that are shown in the action potential?

Answer 32

sodium channels activated, overshoot, sodium channels deactivate, rectified potassium channels activate, hyper polarization

Question 33

WHat is a local response?

Answer 33

A response that causes a little movement of ions but not enough to trip the voltage gates. Membrane reestablished itself almost instantly.

Question 34

What is threshold value?

Answer 34

Once you reach threshold response cannot stop what happens it all relies on the membrane potential. Voltage gates open and reach 0 V and goes beyond to overshoot.

Question 35

Why does the membrane over shoot the 0V?

Answer 35

Because there is a concentration and electrical gradient. Jaust because the electrical gradient is in equilibrium does not mean the concentration is in equilibrium as well.

Question 36

At what voltage do the sodium gates close?

Answer 36

+55mV

Question 37

WHat are the rectified potassium channels?

Answer 37

Specialized gates in cell membrane that allow potassium to move out faster to restore negative inside to outside relationship for another action potential to occur.

Question 38

From the time threshold is reached to the time where the tangent on curve shifts another action potential will not be generated what is this point called?

Answer 38

absolute refractory period

Question 39

Relative refractory period?

Answer 39

period where you can send another action potential but you must have a much stronger signal strength.

Question 40

What is Accommodation?

Answer 40

slow gradual application of stimulus and therefore need a higher threshold...threshold event is changeable

Question 41

What is adaptation? what is a better term for this?

Answer 41

Constant stimulus in certain neurons will cause a decrease in the frequency of depolarization. A better term would be habituation. ex puppy with color