Exam 2 Flashcards
Which channel is most important for NM transmission?
Ligand channels
Which channel is most important for tactile sensation?
Mechanically gated channels
Which channel is most important for action potential transmission in the axon?
Voltage gated channels
What is the membrane’s potential determined by?
Differences in the concentrations of ions
What are the 2 types of gradients created by the different ion concentrations that determine membrane potential’?
Concentration gradients
Electrical gradients
What are the main ions that contribute to membrane potentials? Include their charge and their location of highest concentration
Na: + extracellular K: + intracellular Ca: + extracellular Cl: - extracellular Anions: - intracellular
What are anions made of?
Protein
PO4
What pump is the sodium gradient maintained through?
Na/K ATPase
How does the Na/K ATPase pump work?
It removes 3 Na in exchange for 2 K and contribute -4 mV to the membrane potential
What would happen if the balance of Na significantly differed form inside to outside?
The cell would shrink or swell
Which ion is the most important to be able to diffuse across the membrane? What is its equilibrium potential?
Potassium
-96.81 mV
Which ion is so tightly regulated it cannot diffuse through the membrane? What is its equilibrium potential?
Calcium
+137.04 mV
What is the resting potential for the neuronal membrane?
-70 mV
What does the membrane potential allow the neuron, dendrites, and axons to have?
Excitable membranes so they can transmit signals
Where is the trigger zone (Dr. Beasley’s favorite area)located?
At the axon hillock
What must happen in order to transmit an action potential?
You must reach the threshold to stimulate the axon
What is the membrane potential of the trigger zone?
Between -40 mV and -55 mV
Does a depolarization make the membrane potential more positive or negative?
Positive
Does a hyper polarization make the membrane potential more positive or negative?
Negative
What are the steps of action potential?
Threshold is reached, making depolarization self-generating via graded potentials
This triggers opening of the activation gates of the voltage gated Na channels, which are open for a predetermined amount of time until the inactivation gates close
Sodium rushes into the cell down its potential making the membrane on the inside more positive
This triggers neighboring voltage gated sodium channels to open propagating the action potential, but only in the direction of axon flow because of the absolute refractory period
The voltage gated potassium channels open and the potassium rushes out down its concentration gradient
The membrane becomes extra negative as too much potassium leaves the cell, which creates a hyperpolarized membrane potential
To reach the threshold potential to create a new action potential, you have to get from hyperpolarized membrane to the threshold at -40 to -55 mV
The Na/K ATPase pumps kick into high gear to get the Na out of the cell and the K back in returning the membrane to its resting membrane potential
What is the hyperpolarized membrane potential?
-80 to -90 mV
More simply put, what does the action potential consist of?
Depolarization, repolarization, hyperpolarization
Where does myelin live?
On the axons
What creates myelin in the CNS?
Oligodendrocytes