SL6

Question 1

How are electric potentials made in cells

Answer 1

This happens becuase there are oppsosite charges on either side of the cell membrane, this makes a potential difference

Question 2

What is resting membrane potential

Answer 2

This is the potential difference across the plasma membrane between the intra/extra cellular fluid while the cell it at rest

Question 3

what is the typical range for neuron at rest

Answer 3

it is between -40 to -90mV

Question 4

What causes resting membrane potential to change

Answer 4

an electrical current can alter it causing the cell to change in polarization

Question 5

what causes + and - ions to be close to the cell membrane

Answer 5

the opposite ions attract to one another and thus are close to the cell membrane

Question 6

what is the main ion in extrcellular and intracellular fluid

Answer 6

Extracellular: Na+
Intracellular K+

Question 7

what does membrane potential depend on

Answer 7

1. difference in ion concentration between the intracellular and extracellular fluid
2. the membranes permeability to ion s

Question 8

Describe what happens if a membrane ion channel opens and causes a flux of an ion (use potassium as an example)

Answer 8

1. potassium channels open, K+ diffuse and goes with the concentration gradient, this creates a net positive charge
2. movement of K+ has created an electrochemical gradient, K+ will continue to flow with its concentration gradient (because it is bigger) causing the potential difference to increase
3. eventually equilibrium will be reached when both potentials are equal in magnitude

Question 9

what is an ion leak channel

Answer 9

they allow ions to difuse through the membrane and are specific to ions, they are always open, don’t need ATp

Question 10

what dictates the movement of ions using ion leak channels

Answer 10

it is a balance between the concentration gradient of ions and there electrical potential

Question 11

what is electrical potential

Answer 11

this is where ions want to flow towards opposite charged ions

Question 12

what establishes and maintains the resting memebrane potential of. neuron

Answer 12

-The Na+/K+ ATPase pump does this

Question 13

what maintains a cells - membrane potential

Answer 13

this is mainly done by an eflux of K+, the Na+/K+ ATPase pump has a minor role

Question 14

betweeen Na+ and K+ what has low/ high permeability and which one has low/high electrochemical gradient

Answer 14

K+ is highly permeable but low electrochemical gradient while Na+ has low permeability but high electrochemical gradient

Question 15

what can move Na+ and K+ against the their concentration gradient and describe the process

Answer 15

The Na+/K+ ATPase pump can do this, 3 Na+ are pumped out of the cell using ATP, after that 2 K+ ions are brought into the cell

Question 16

what are the different types of gated ion channels and how are they different from leak chanells

Answer 16

there is mechanically, chemcially or voltage gated, they are different because they are open or closed based off of their environment

Question 17

what is polarized and what is overshoot

Answer 17

-polarized: potential difference between the inside and the outside
- overshoot this is where the membrane potential is reversed (inside is positive relative to outside)

Question 18

what are some key characteristics of graded potentials

Answer 18

-confined to small region of the cell
-magnitude can change (this is why it is called graded)
-they are named based off of their location or function
-they can initiate AP

Question 19

In a graded potential what is required for summation

Answer 19

-another potential needs to arrive before the graded potential disapears

Question 20

What are some key characteristics of AP

Answer 20

-cause large alterations in membrane potential
-very rapid, can repeat frequencies for several seconds
-communicated over large distances
-transient changes in membrane permeability to Na+ and K+ which allows them to travel down their electrochemical gradient

Question 21

what are some key aspects of Voltage-gated ion channels

Answer 21

-vary by which ion they conduct
-K+ and Na+ can reversibly change in shape in response to changes in membrane potential
-the channels are closed when membrane potential is negative and open when it is depolarizing

Question 22

what responds faster to changes in membrane voltage

Answer 22

Na+channels open and close before K+ channels

Question 23

what limits Na+ flux shortly after depolarization

Answer 23

inactivation gate

Question 24

what is an example of positive and negative feedback during AP

Answer 24

-positive: more Na+ channels keep opening a the membrane becomes more and more depolarized
-negative: when K+ channels open when the cell is depolarized causing the cell to repolarize

Question 25

in a neuron what stops the AP from going the other way

Answer 25

• the refractory period where the neuron needs time to get back to its normal resting potential and AP can’t send the other way

Question 26

what allows AP to travel in the correct direction in a neuron

Answer 26

Nodes of ranvier

Question 27

what is receptor potentials

Answer 27

they are produced at peripheral endings of afferent neurons in response to stim

Question 28

what are synaptic potentials

Answer 28

they are produced in the post synaptic neuron in response to the release of NT by a presynatpic terminal

Question 29

describe the steps in which an AP is formed

Answer 29

1. threshold is reached, Na+ influx causes addiontal voltage gated Na+ channels to open and the cell depolarizes
2. membrane potential overshoots and Na+ channels begin to close and K+ channels open
3. peak membrane potential is reached and Na+ channels are fully closed and voltage gated K+ channels open, causing K+ flux out of the cell
4. cell starts to reploarize
5. cell returns to resting membrane potential but K+ close slower than Na+ channels and the cell hyperpolarizes
6. cell final returns to resting membrane potential