Lecture 5- Intro to NS (Action potentials) Flashcards
1
Q
Neurons are like tiny batteries becauseee
A
- They store a charge (capacitor)
- Basally (resting membrane potential) is negatively charged (hyperpolarized)… there is a difference between the inside and outside charge
- You can change the charge inside a neuron with ions (positive and negative charges)
2
Q
Movement of Charges
A
- Movement of charges = changes in potential
- Na+, K+, Cl+, and Ca2+ are extremely important ions to neurons (more K+ and protein inside the cell, more of everything else outside the cell)
- A neuron resting membrane potential is about -70mV (a lot more negative ions are on the inside than the outside)
3
Q
What causes ions to pass through channels?
A
- The electrochemical gradient
- Protein channels allow ions to go in and out, the concentration gradiet determines if a channel will open. Ions from the ouside (cations) will be attracted to the anions in the inside.
- The electrochemical gradient is essential for action potential change
4
Q
Generation of an action potential
Step 1
A
- Resting potential is present (-70mV)
5
Q
Generation of an action potential
Step 2
A
- Initial depolarization/threshold value… positive ions slowly trickle into the neuron, and the membrane potential becomes more positively charged.
- The sodium channels begin to open up to allow the sodium to come into the cell
- The neuron is now depolarized
- Hits a cap around -50mV, this is the action potential threshold
6
Q
Generation of an action potential
Step 3
A
- Rapid depolarization
- Once the neuron hits the threshold (-50mV), the sodium channels open all at once and the sodium rushes into the cell very fast
- Limit is around +40mV
7
Q
Generation of an action potential
Step 4
A
- Repolarization/Hyperpolarization
- Sodium channels close up at +40mV
- Potassium channels open at this point
- The positive potassium channels are pushed potassium out, the neuron starts becoming more negative again
8
Q
Generation of an action potential
Step 5
A
- Refractory period
- The neuron is made a little too negative
- We think this is to limit the neuron from firing too frequently
- The neuron cannot generate another action potential because it is below the threshold
9
Q
Generation of an action potential- facts
A
- The entire process takes only 1 millisecond
- We consider action potentials to be all or none due to the thresholds
10
Q
Speed of an action potential is critical
A
- Myelination occurs throughout development
- Increases speed of neuronal communication is part of maturation
11
Q
Myelin Sheath
A
- Insulating layer made up of protein and fatty substances
- Formed by oligodentrocytes
- Fat is the white color in the brain (white mater) and is myelinated axons
12
Q
White vs. grey matter
A
- White matter is fat, is the myelinated axons
- Gray matter is everything else (cell bodies, dendrites, axons)
13
Q
What diseases are associated with myelin degeneration?
A
- Multiple Sclerosis (MS)
- Huntington’s Disease (HD)
- Traumatic Brain Injury (TBI)
14
Q
Integration of Information
A
- Neurons simultaneously recieve inputs from multiple neurons
- Excitatory inputs (positive ions) are the “accelerator,” known as EPSPs (Excitatory postsynaptic potentials). They slowly build up to threshold and generate an actio potential
- Inhibitory inputs (negative ions) are the “brakes,” known as IPSPs (Inhibitory postsynaptic potentials)- inhibits cell from generating an action potential
Neurons must sum up this information to reach action potential threshold
15
Q
Temporal summation
A
Rapid succession at same input
