1. Membranes & Nerves
Card Set Information
1. Membranes & Nerves
What is Resting Membrane Potential (RMP)?
A difference in electrical potential across the plasma membrane at rest.
What is Action Potential?
Stimulation of i.e. a spinal reflex --> action potential in a spial motor neuron.
Allows the neurons (bad at conducting electrical signals long way) to signal across long distances.
What are the intra-/extracellular consentrations for:
: High concentration intracellular
: High concentration extracellular
What are active/passive transporters?
Active (ion transporters)
Activly move ions into or out of cells, against their concentration gradient.
Passive (ion channels)
Proteins allow certain kinds of ions to cross the membrane in the direction of their concentration gradient.
Describe the K
Uses 1 ATP
Moves 3 Na
& 2 K
against their concentration gradient
Describe the passive transport of K
across the membrane
moves outside the cell, taking its positive charge with it
Since the charge will be positive outside the cell, it repells the K
back against it concentration gradient.
The equlibrium is an "electrochemical" balance
What is the difference between Nernst and Goldmans equations?
Nernst only considers the concentration of a given ion (eg. K
Goldman considers K
Describe the ionic basis of the A.P.
(the steps of AP)
AP are conducted along the axon, which contains voltage gated Na
: Rising (depolarization), Overshoot, Falling (repolarization), Undershoot
1. The neuronal membrane becomes temporarily permeable to Na
due to opening of more and more Na
channel that are closed at rest.
2. The membrane potential deoplarizes and approaches E
3. Decrease in Na
pemebeality (inactivation of Na
channels) and delayed increase in K
permeability cause repolarization of the membrane toward the E
and resting levels.
4. During the
(afterhyperpolarization) the K
permability is greater that it is at rest.
5. The membrane potential returns to resting levels
Name the 3 general classes of ion channels found in neurons.
Leaked/Non-gated ion channels
Voltage gated ion channels
Ligand gated ion channels
How does a Leaked/Non-gated ion channel work?
Always open and specific for an ion (i.e K
The ions flow aross the plasma membrane down their concentration gradients, taking their charge with them. This in turn causes the potential!
How does a Voltage-gated ion channel work?
These channels have a charged voltage sensor that detects a change in the membrane potential and permits voltage dependent gating of ion channels.
Closed at rest, opens when membrane potential changes.
Example of Voltage gated ion channels
How does a Ligand-gated ion channel work?
Open when a ligand (e.g a neurotransmitter) binds to it.
Example of neurotransmiters
: acetylcholine, glutamate, GABA, glycine.
Example of ionotropic receptor
: the acetylcholine nicotinic receptor
What are ionotropic, ligand gated channels?
Allow influx of Ca
that leads to hyperpolarization
What are the differances between the K
voltage gated channels?
has 2 gates; Close/Active --> Open --> Close/Inactive --> Close/Active
has only 1 gate; Close --> Open --> Close
opens faster, causes shooting phase.
is slower and cuases the falling phase.
There are 3 groups of neurotransmittors, which are they?
1. Small molecules
- Biogenic amines (monoamines)
: Dopamine, Noradrenaline, Adrenaline
--- GABA and Glycine (-)
--- Glut and Asp (+)
: Opiopds (endorphin), Somatostatin, Substance P
3. Others (non-vesicular release)
: Neuroactive gases (NO, CO, arachidonic acid etc)
Name the events from neurotransmittor release to postsynaptic excitatinon or inhibition
1. Neurotransmittor release
2. Receptor binding
3. Ion channels, open or close
4. Conductor change causes current-flow
5. Postsynaptic potential changes
6. Postsynaptic cells, excited or inhibited
7. Summation determines whether or not an AP occurs
Name one inhibitatory and one excitatory neurotransmittor molecule
: GABA and Glycine
: Glutamate and Aspartate