What are some ways that drug-receptor interactions can influence neuronal firing? Flashcards
What is the driving force behind action potentials?
The fact that polar molecules are hyrdophyllic and lipophobic
What are the main ions involved in action potentials?
- potassium
- sodium
- chloride
- Calcium
- anions
What is an anion?
Any negatively charged particle
What are the two major forces that determine where ions will flow?
- electrostatic forces (opposites attract, similars repel)
2. diffusion forces (an ion will want to go from an area of high concentration, to an area of low concentration)
What are the different kinds of channels situated in the membrane of a neuron to aid with action potential firing?
- potassium channels
- voltage-gated sodium channels
- voltage-gated potassium channels
- sodium-potassium pump
- voltage-gated calcium channels
What happens when K+ flows out of the cell, via the potassium channels?
The net charge of the cell relative to the outside becomes negative (at approximately -80 mV)
What is the equilibrium potential of potassium?
- 80 mV
- this is the charge at which no more K+ ions are flowing in or out of the cell
When do the voltage-gated Na+ channels open?
When the membrane potential is at -40 mV
What force(s) drive sodium into the cell?
Both electrostatic and diffusional forces
To which potential does sodium cause the cell to rise to?
+40 mV
When do the voltage-gated potassium channels open?
When the membrane potential is at +40mV
What force(s) drive potassium out of the cell?
Both electrostatic and diffusional forces
To which potential does potassium cause the cell to fall to?
-85mV
When do the sodium-potassium pumps kick in? Why do they have to kick in?
When the membrane potential is at -85mV
- they have to kick in because the potassium channel is only SEMI permeable to K+, so the cell wouldn’t stabilize soon enough on its own
What is the all-or-none law?
The law that states that an action potential either happens or it doesn’t; it can’t only get halfway
What is the function of the axon hillock?
It connects the soma of the cell to the axon
Approximately how many synapses can one neuron have?
In the hundreds of thousands
- each input is casting a vote to the all-or-nothing law
- the number of “votes” decides whether a cell will fire or not
What is an undershoot?
Another word for hyperpolarization
What is glutamate? What receptor does it bind to?
Glutamate is the main excitatory neurotransmitter in the brain
- glutamate binds to AMPA receptors (which are ligand-gated)
What are AMPA receptors permeable to?
Both K+ and Na+
- thus, the net effect becomes positive, driving the cell closer towards an action potential
What is GABA? Which receptor does it bind to?
GABA is the main inhibitory neurotransmitter in the brain
- GABA binds to the GABA(a) receptor, which is a ligand-gated ion channel
What are GABA(a) receptors permeable to?
Chloride (Cl-)
- therefore, the net effect becomes negative, moving the cell further from generating an action potential
What decides if a neuron will fire?
Which charge reaches the axon hillock first
Why is phosphorylation of G-protein coupled receptors an important concept to remember when thinking about action potentials?
Because phosphorylation can either:
- change the ion that the receptor is permeable to, or
- affect transcription to increase or decrease the production of a receptor,
this means that G-protein coupled receptors can affect how easily a neuron will fire (acting like a sidekick to the excitatory or inhibitory neurotransmitters)
What is excitotoxicity?
When a cell is so excited that it dies
Why is it dangerous to consume alcohol while taking sleeping pills?
Because both act on GABA(a) receptors, decreasing the likelihood of action potentials significantly, leading to coma or death
What is stroke damage due to?
When oxygen is depleted in the brain, glutamate is released uncontrollably, leading to excitotoxicity
When do the voltage-gated Ca2+ channels open?
When an action potential reaches the terminal bouton
What happens when a voltage-gated calcium channel opens?
It causes a second-messenger cascade to cause the vesicles in the terminal to migrate to the synaptic cleft, releasing neurotransmitters
