2. Electrical Acitivity Flashcards
How thick is a cell mem?
2 phospholipid molecules thick
Describe the 5 main processes involved in moving molecules passed the mem. Include if it is passive or active.
- simple diffusion = small, nonpolar, uncharge molecules can passively diffuse through the mem
- ion channels = passively allow ions to flow in or out as the [gradient] dictates
- voltage-gated channels = gated channels that allow certain ions to pass dep on the Vm (passive)
- active transporters = transporter proteins that allow molecules/ions to pass against their [gradients] using ATP (active)
- water filled pores = allow small charged molecules to passively enter the cell
T or F - voltage-gated channels have a gate that open dep on the Vm and reset immediately once the Vm changes back.
F - it takes some time for the voltage gate to reset even after the Vm changes back so another protein blocks the channel until the gate can reset
Aside from the 5 main processes used to help molecules enter/exit the cell what are 3 other lesser-known processes?
- endocytosis = vesicle is brought into cells
- exocytosis = vesicle is taken out of the cell
- phagocytosis = the cell engulfs the particle whole
The most well-known and relevant active transporter is the Na/K ATPase. Which involves resetting the electrochemical gradient of Na and K after an AP has taken place. Which way and how many mol each does each ion get transported?
2 K = into the cell
3 Na = out of the cell
What is the purpose of cell mem?
they act as a semi-permeable barrier that only lets certain molecules cross it. Protect the cell
What type of proteins are transporters?
integral (extends from both sides of the mem) mem proteins
What is the significance of ion channels in the NS?
these channels help to produce electrical impulses that are transported across neurons in allowing communication to occur
What is the Vr of the cell mem? What does this mean?
Vr ~ -70mV = meaning that the inside of the cell is more neg than the outside when mem is at rest
What is the significance of voltage-gated ion channels wrt AP?
These channels allow the AP to continue down the axon, reamplifying it as it continues to travel
What is the primary fxn of a nerve cell?
to receive, conduct and transmit signals (APs)
Describe an AP
a momentary depolarization of the Vm caused by an influx of Na
What are the 3 steps to an ion-gated channel during an AP?
- Gate is closed when at Vr
- Gate opens when Vm is pos (depolarization)
- A protein inactivates the gate due to a delay in gate reset once Vm DEC (hyperpolarization)
What is another way to say depolarization?
hypopolarization
An AP is caused by a strong enough stimulus to pass the threshold. This results in an influx of Na ions into the axon which causes a propagation of depolarization down the axon. This propagation always goes in the same direction from the axonal hillock where it is generated to the terminal. How it is unidirectional.
After the depolarization of that part of the axon due to an influx of Na ions those same Na ion-gated channels close and the K ion-gated channels open resulting in an outflux of K ions. This hyperpolarization due to positive ions leaving the cell produces a refractory period within that part of the axon. During this time that part cannot be depolarized until the Vm is repolarized back to Vr.
Draw the flowchart of what happens during an AP from the presynapse to the post. include what happens in the following parts of the neurons.
a) axon terminal of presynapse - 3
b) dendrite + soma - 3
c) axon hillock - 1
d) axon of postsynapse - 1
