History
When was the neuron first discovered?
1863
What ion is responsible for a delayed, outward current?
potassium (K+)
Why does the action potential only spread in one direction, and not both ways, including back to the cell body?
Because voltage-sensitive Na+ channels are briefly inactivated after they open
Which opens first, a voltage-gated potassium channel or a voltage-gated sodium channel?
Voltage-gated Na+ channels open at the threshold potential, leading to an action potential. Then, voltage-gated K+ channels open, bringing the membrane potential close to K+ equilibrium potential.
What macromolecules are found in the cell membrane? Which one appears the most?
Lipids, carbohydrates, and proteins
Lipids
Camillo Golgi
What is the difference between a microscopic current and a macroscopic current?
Microscopic currents flow through individual channels
Macroscopic currents are summations of microscopic currents
Which ion is responsible for maintaining resting potential? Action potential?
Potassium for resting
Sodium for AP
How does permeability of ions change
over time?
Ion channels specific to that ion species open and close given different conditions
primary proteins are made up of ___ while quaternary proteins are made up of ____
amino acid chains, many polypeptide chains (subunits)
Which scientist came up with the neuron hypothesis?
Santiago Ramon y Cajal
Early inward current reverses at around which ion's equilibrium potential?
Sodium (Na+)
What is passive current flow?
When the stimulus is not great enough to reach the action potential threshold potential thus there is no active opening of ion channels and the voltage dies out
What are Tetrodotoxin (TTX) and Tetraethylammonium (TEA) used for?
TTX: Blocks sodium channels
TEA: Blocks potassium channels
Transcription makes ___ and translation makes ____
mRNA, proteins
Which scientists worked on the giant squid axon?
Hodgkin and Katz
What does a patch clamp study tell us? How does it test this?
Does the ion channel inactivate right away? At what voltage does the channel activate (open)?
By studying one ion channel at a time
What is saltatory conduction?
ion channels are only present in the Nodes of Ranvier so the action potential "jumps" over the myelin
What are the four types of ion channels and give a description of each.
1. Leakage channels: open all the time
2. Voltage-gated ion channels: open and close depending on the potential across the membrane
3. Ligand-gated ion channels: open in response to a chemical ligand binding to the channel
4. Stretch-gated ion channels: which open due to mechanical force acting on the channel
What do microtubules do?
carry proteins up & down the long processes of the neuron
What is the neuron hypothesis?
The brain is made up of cells
(neurons), like other biological tissue, and
these neurons are the basic signaling units
for the nervous system
How does a voltage clamp study work?
Use an electrode to inject current into the neuron so that the membrane potential is equal to a desired potential and a voltage clamp amplifier holds it steady at said current
How do we know which ion is responsible for resting potential? How about an action potential?
Resting: Increased the amount of extracellular K+ and the resting potential predictably increased as well.
Action: Take away extracellular Na+ which decreased the concentration difference inside and outside the cell, the equilibrium potential for Na+ goes down which reduces an action potential
How do ion channels keep the ions they do not want to enter out?
The pore of an ion channel can only fit a specific ion's size and its water shell
What allows voltage-gated ion channels to change shape once activated?
Some regions of the alpha subunit are voltage
sensitive (voltage sensors), allowing changes in conformation (shape) with voltage changes