Section 43.2.1 (Exam 4) Channels Flashcards
Neurons Generate and Transmit Electric Signals
What are ion pumps and channels responsible for?
the distribution of charges across the membrane that determine membrane potential
What does the sodium-potassium pump do?
moves 3 Na+ to the outside and 2 K+ to the inside; requires energy; establishes concentration gradients
Ion channels are selective. What does this mean?
there are different channels for each type of ion
Which way do ions move through channels, and what does it depend on?
Ions can move in either direction; net movement depends on concentration gradient and voltage difference, which is called the electrochemical gradient
What is the electrochemical gradient?
concentration gradient of ions and voltage difference are the two motive forces that create the electrochemical gradient
Why is the inside of the cell usually negative relative to the outside?
“Leak channels” allow some ions (K+) to diffuse out
What is caused by K+ leak channels being open during resting membrane potential?
Unbalanced negative charges are left inside the cell and K+ ions diffuse back into the cell to balance them out
Define membrane potential.
electrical charge difference across a cell membrane
What causes a membrane potential?
due to a balance between the tendency of K+ ions to diffuse down their concentration gradient and the electrical potential that holds them back
Define resting potential.
the steady state membrane potential of a neuron
What is the resting potential of an axon in millivolts (mV)?
-60 mV to -70 mV
There are leak channels that are always open and then there are gated channels. Define the three gated channels.
Voltage-gated channels respond to change in voltage across membrane.
Chemically-gated channels depend on specific molecules that bind or alter the channel protein.
Mechanically-gated channels respond to force applied to membrane.
What alters membrane potential?
Opening and closing of gated channels
What will happen if Na+ channels suddenly open?
Na+ diffuses in and the inside of the cell becomes less negative.
When the inside of a neuron becomes less negative (or more positive) in comparison to its resting condition, its cell membrane is depolarized
What will happen if K+ channels open suddenly?
K+ efflux increases over the normal leak rate, the membrane potential becomes even more negative, and the cell membrane is hyperpolarized
