the membrane potential

Na+ concentration gradient

Na+ concentration gradient

Na+ concentration is higher on the extracellular side of the neuron

• positively charged ion

K+ concentration gradient

K+ concentration is higher on the intracellular side of the neuron

• positively charged ion

A- concentration gradient

A- concentration is higher on the intracellular side of the neuron

• negatively charged ion

leak channels

channels that permit constant movement of ions

• sodium and potassium leak channels

• includes diffusion which is made for specific ions to pass through

mechanical gated channel

open or close in response to physical distortion of a membrane surface

• applied pressure opens gate, removed pressure closes gate

• located in dendrites

chemical gated channel

open or close when a specific chemical binds to it

• binding chemical opens gate

• located in dendrites and cell body of neuron

voltage gated channel

open or close in response to changes in the membrane potential

• change in electrical charges open and close gates

  • -70mV: more negative charges, VGC is closed

  • -55mV: less negative charges, VGC is open

• located in axon hillock and axon of a neuron

resting membrane potential

not actively sending impulses

• inside of a membrane contains more negative charges and outside contains more positive charges

• charge is approximately -70mV

sodium (Na+) leak channels

• neuron is not permeable to Na+ because there are few Na+ leak channels

• most of its positive ions pile up on the outside of the PM trying to diffuse into the neuron

potassium (K+) leak channels

• neuron is permeable to K+ because there are many K+ leak channels

• its positive ions contribute to a positive charge build up on the outside of the PM as K+ has an easy time diffusing out of the neuron

why aren’t there leak channels for protein (A-)

negatively charged proteins are too large to fit through a membrane channel

how do the Na+/K+ pumps help maintain the resting membrane potential

more positive charges being pumped out than in helps add to the positive charges on the outside of the membrane

• 3 Na+ ions pump out for every 2 K+ ions pumped in

depolarization

membrane potential becomes less negative

• caused by the opening of an active/gated Na+ channel

• when a stimulus opens the Na+ gated channel, the positive ions diffuse into the PM therefore decreasing the negative charges

hyperpolarization

membrane potential becomes more negative

• casued by the opening of an active/gated K+ channel

• when a stimulus opens the K+ gated channel, the positive charged ions diffuse out of the PM therefore increasing the negative charges

how can a graded potential be generated

by both a depolarizing stimulus and a hyperpolarizing stimulus

how can an action potential be generated

by a depolarizing stimulus

which gated channels open to cause a graded potential

mechanical/chemical gated Na+ and K+ channels

threshold

negative charge at -55mV triggered by the opening of Na+ gated channels

how far does a graded potential travel

from the cell body towards the axon hillock

how far does an action potential travel

down the entire length of the axon until it reaches the synapse

2 types of gated channels in the dendrite/cell body of a neuron

mechanical gated Na+/K+ ion channels and chemical gated Na+/K+ ion channels

if the neuron depolarized to threshold, what happens next

triggers the opening of the voltage gated Na+ channels and an action potential is produced

how do voltage gated Na+ channels open

in a domino effect

3 things that occur during repolarization

1. voltage gated Na+ channels close

2. voltage gated K+ channels open

3. Na+/K+ pumps pump ions against their gradient