week 2 - resting potential and action potential Flashcards
What is the main component of a cell that drives in neuron communication?
cell membrane
cell membrane
- phospholipid bilayer
- semi-permeable
semi-permeable
very small structures, such as oxygen and other gases, can pass; ions (charged particles) cannot
What do neurons use to communicate with each other?
ions (charged particles)
cations
- positive charge
- ex.) Na+, Ca+ K+
anions
- negative charge
- ex.) CI-
What is one way that ions cross the cell membrane?
They use ion selective channels made of transmembrane protein pores.
Why are some ion channels gated?
to prevent ions from going through
What forces will push an ion across an open ion channel?
diffusion and electrostatic forces
diffusion
molecules move from high concentration to low concentration
electrostatic force
- electrical gradient
- opposites attract, likes repel
What is potential?
the difference in charge between the inside and outside of a cell membrane
What is the resting membrane potential of a neuron?
-70mV
Why is the resting membrane potential negative?
due to the unequal distribution of ions; there are more anions inside compared to outside
During diffusion, which way to ions go?
- K+: outside
- CI-: inside
- Na+: inside
During electrostatic forces, which way do ions go?
- K+: inside
- CI-: outside
- Na+: inside
Why is there an unequal distribution of ions?
selective permeability and sodium-potassium pump
selective permeability
- membrane is moderately permeable to K+ and CI- but relative permeable to Na+
- Na+ is impermeable
sodium-potassium pump
- makes up for Na+ impermeability
- active transporter (must use ATP)
- pumps 3 Na+ out for every 2 K+ pumped in
What is the direction of neuronal conduction?
- soma to axon
- then presynaptic to postsynaptic
What is action potential?
rapid changes in cell membrane potential
depolarization
- inside of cell becomes less negative/more positive
- cations enter and anions exit
hyperpolarization
- inside of cell becomes more negative/less positive
- anions enter and cations exit
axon hillock
- spike initiation zone
- stimulus can be applied once or multiple times
What happens when stimulus reaches threshold?
- action potential occurs
- may cause ion channels to open/close
What is the movement of Na+ channels when action potential occurs?
- Na+ ion channels will open and Na+ ion rush in (causes depolarization
- channels close at peak of action potential (Na+ cannot enter)
What happens during action potential?
- when cell membrane threshold is met, voltage-gated Na+ channels open up, Na+ enters the cell
- Na+ channels close in 1 msec
- In the meantime, voltage-gated K+ channels open, K+ leaves cell, repolarizing it
- “all-or-none”
How is information coded by the nervous system?
based on changes in pattern frequency
What would happen if you were given a drug that blocked Na+ channels?
action potential does not occur
What happens if you are given a drug that blocks K+ channels?
repolarization would not occur (constant depolarization)