SL6 Flashcards
How are electric potentials made in cells
This happens becuase there are oppsosite charges on either side of the cell membrane, this makes a potential difference
What is resting membrane potential
This is the potential difference across the plasma membrane between the intra/extra cellular fluid while the cell it at rest
what is the typical range for neuron at rest
it is between -40 to -90mV
What causes resting membrane potential to change
an electrical current can alter it causing the cell to change in polarization
what causes + and - ions to be close to the cell membrane
the opposite ions attract to one another and thus are close to the cell membrane
what is the main ion in extrcellular and intracellular fluid
Extracellular: Na+
Intracellular K+
what does membrane potential depend on
- difference in ion concentration between the intracellular and extracellular fluid
- the membranes permeability to ion s
Describe what happens if a membrane ion channel opens and causes a flux of an ion (use potassium as an example)
- potassium channels open, K+ diffuse and goes with the concentration gradient, this creates a net positive charge
- 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
- eventually equilibrium will be reached when both potentials are equal in magnitude
what is an ion leak channel
they allow ions to difuse through the membrane and are specific to ions, they are always open, don’t need ATp
what dictates the movement of ions using ion leak channels
it is a balance between the concentration gradient of ions and there electrical potential
what is electrical potential
this is where ions want to flow towards opposite charged ions
what establishes and maintains the resting memebrane potential of. neuron
-The Na+/K+ ATPase pump does this
what maintains a cells - membrane potential
this is mainly done by an eflux of K+, the Na+/K+ ATPase pump has a minor role
betweeen Na+ and K+ what has low/ high permeability and which one has low/high electrochemical gradient
K+ is highly permeable but low electrochemical gradient while Na+ has low permeability but high electrochemical gradient
what can move Na+ and K+ against the their concentration gradient and describe the process
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
what are the different types of gated ion channels and how are they different from leak chanells
there is mechanically, chemcially or voltage gated, they are different because they are open or closed based off of their environment
what is polarized and what is overshoot
-polarized: potential difference between the inside and the outside
- overshoot this is where the membrane potential is reversed (inside is positive relative to outside)
what are some key characteristics of graded potentials
-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
In a graded potential what is required for summation
-another potential needs to arrive before the graded potential disapears
What are some key characteristics of AP
-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
what are some key aspects of Voltage-gated ion channels
-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
what responds faster to changes in membrane voltage
Na+channels open and close before K+ channels
what limits Na+ flux shortly after depolarization
inactivation gate
what is an example of positive and negative feedback during AP
-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
in a neuron what stops the AP from going the other way
- the refractory period where the neuron needs time to get back to its normal resting potential and AP can’t send the other way
what allows AP to travel in the correct direction in a neuron
Nodes of ranvier
what is receptor potentials
they are produced at peripheral endings of afferent neurons in response to stim
what are synaptic potentials
they are produced in the post synaptic neuron in response to the release of NT by a presynatpic terminal
describe the steps in which an AP is formed
- threshold is reached, Na+ influx causes addiontal voltage gated Na+ channels to open and the cell depolarizes
- membrane potential overshoots and Na+ channels begin to close and K+ channels open
- peak membrane potential is reached and Na+ channels are fully closed and voltage gated K+ channels open, causing K+ flux out of the cell
- cell starts to reploarize
- cell returns to resting membrane potential but K+ close slower than Na+ channels and the cell hyperpolarizes
- cell final returns to resting membrane potential
