Chapter 4 Flashcards
Neurons and electrical signaling
What is a positively charged ion called?
Cation
What is a negatively charged ion called?
Anion
Cation
Positively charged ion
Anion
Negatively charged ion
Concentration gradient
the relative abundance of a substance in a space (ions in this case)
Concentration gradients flow due to…
Diffusion
Diffusion
the movement of a substance from a high concentration to a place with low concentration
Does diffusion require energy?
No
Voltage gradient
the difference in charge between 2 areas
How do ions flow in a voltage gradient?
from a place of higher charge to a place of lower charge
What is the voltage of an axon during resting potential?
-70mv (avg.)
What four charged particles take part in producing resting potential and where are they concentrated (intra- or extracellular)?
Na+ (extra-), K+ (intra-), Cl-(extra-), A- (intra-)
What three features contribute to the cell’s resting potential?
- A- (protein anions) can’t pass out of the cell (keeps negative voltage).
- channels allow K+ and Cl- to flow freely in and out of cell (along concentration/voltage gradient)
- Na+-K+ pumps extrude Na+ and inject K+ (3 Na+ for 2 K+, keeping voltage difference).
Why don’t sodium ions diffuse freely across the cell membrane?
Gated channels.
What does the sodium-potassium pump do?
Pumps 3 sodium ions out of the cell and take in 2 potassium ion. For when sodium ions leak in the cell.
How do chloride ions travel across the cell membrane?
Open channels. Still, because of the voltage gradient and concentration gradient, there are more chloride ions outside of the cell.
What is a graded potential?
A small voltage fluctuation across the cell membrane
What is hyperpolarization?
An increase in the charge inside the cell.
Less likely for an action potential to occur.
What ions contribute to hyperpolarization
Efflux of K+ (outside becomes more positive)
Influx of Cl-
What is depolarization?
A decrease in the charge inside the cell.
More likely for an action potential to occur.
What ions contribute to depolarization?
Na+ (inlfux inside the cell)
Where on the cell do graded potentials occur?
Soma and neuronal dendrites - where there are gated channels
What is the threshold potential of a cell?
-50mv
How much does a cell depolarize during an action potential?
to 30mv (100mv change)