week 3 Flashcards
Name and describe the phases of communication within the neuron. Explain conduction of an action potential. Describe and explain synaptic communication between neurons. Identify and describe various neurotransmitters in the brain. Describe non-chemical communication.
When cells communicate where does the info come through?
Communication between cell is directional
Info comes through dendrites and soma
Then transmits down the axon outwards other neurons
What triggers an electrical signal(action potential)?
The electrical change that occur in the cell which would trigger an electrical signal called the action potential which moves down the axon all the way to the terminal buttons
How does communication with the cell begin?
Communication begins by disturbing the resting potential of a cell.
Disturb by depolarizing (+++) or hyperpolarizing (—) the cell
What is Membrane Potential?
The electrical charge across a cell membrane (voltage unit = mV)
What is Resting membrane potential?
The potential of a neuron when it is not being altered by excitatory or inhibitory innervation;
Voltage is more negative inside relative to outside; -40 to -90 mV (-70mV)
When at rest the cell is maintaining polarization, that difference between the intracellular and extracellular spaces
What is Intracellular and extracellular?
Intracellular(inside of cell) is always more negative than extracellular(outside of cell) when at rest
What are Cations and Anions?
Ions: charged molecules
Cations (K+, Na+, Ca2+); positive charged ions
Anions (Cl-); negative charged ions
What is Diffusion?
Movement of molecules from regions of high concentration to regions of low concentration = Concentration Gradient
What is Electrostatic Pressure?
Opposites attract; Similarity repulse = Electrical Gradient (polarization)
What are 2 forces working on ions?
Diffusion
Electrostatic Pressure
How do you maintain polarization?
Voltage-gated Ion channel (passive transport pump)
Sodium-Potassium pump (active transport pump)
Desribe the Voltage-gated Ion channel
An ion channel that opens or closes according to the value of the membrane potential (how pos. or neg. the membrane potential)
Na+ voltage gated channels is closed when at rest; Na+ concentration greater outside cell than inside cell
K+ voltage gated channels is closed when at rest; K+ concentration greater inside cell than outside cell
Describe the Sodium-Potassium pump (active transport pump).
Pushes 3 Na+ ions out of the cell where there is a high concentration of Na+
and pulls 2 K+ into cell, where there is a low concentration of Na+
Ensures resting membrane potential
Requires energy (ATP) (active transport) b/c this pump moves ions against their concentration gradient
Role: Regulate ion concentration
Result: Na+ is 10x more concentrated in intracellular space
How does Concentration Gradient (diffusion) and Electrical Gradient (electrostatic pressure) effect Na+? In respect to Activity in the Neuron.
Both forces Na+ to enter the cell
Sodium (positive) will want to be pulled into the cell because it is a mostly negative space (mV-70) (electrostatic pressure)
Sodium is more concentrated outside the cell than inside of the cell so sodium will want to be pulled into the cell along its concentration gradient (diffusion) b/c there is less concentration
How does Concentration Gradient (diffusion) and Electrical Gradient (electrostatic pressure) effect K+? In respect to Activity in the Neuron.
Competing forces act on K+
Diffusion forces K+ out of the cell where its less concentrated
Electrostatic Pressure forces K+ into the cell, like Na+
Potassium channels are not fully closed so K+ can leak out of cell (Net movement will ensure greater concentration of K+ inside cell at resting)
What is the Action Potential?
Electrical charge that runs down the axon from the axon hillock to the terminal buttons
From mV-70 Voltage goes up to mV+40 after depolarization reaching an action potential. After repolarization begins and the mV returns back down to mV-70.
But also going into a refractory period where it hyper-polarizes and becomes more negative than the resting membrane potential.
The sodium potassium pump reinstates the membrane potential go to back to its resting state
What is the Threshold of excitation?
the value of the membrane potential that must be reached to produce an action potential
An action potential is all or none, if the charge is not made positive enough an action potential will not be generated
What are the 3 phases of an Action Potential?
Depolarization: Reduction (toward zero) of the membrane potential of a cell from its normal resting potential. Less negative
Repolarization: An increase in the membrane potential of a cell toward resting state. More negative
Hyperpolarization: An increase in the membrane potential of a cell, more negative than resting potential
Which respect to an Action Potiential, what is going on with Na+ and K+?
Na+ channels open as soon an threshold is met (depolarization)
Na+ begins to enter the cell(depolarization)
K+ channels open and leave the cell(depolarization)
B/c of the rush of Na+ the impact of K+ leaving the cell is minimal
Na+ channels becomes refractory, and shut close no more Na+ can entre(action potential)
K+ continues to leave cell, membrane potential returns to normal(repolarization)
K+ channels close Na+ reset
Extra K+ outside, sodium -potassium pump reestablish resting membrane potential (refractory period)
What is the Absolute refractory Period?
brief interval after a successful stimulation (meeting threshold) another action potential can not be generated
Time from opening of the sodium “activation gate” to closing of “inactivation gate”
What is the Relative refractory Period
if the cell is stimulated enough then a new action potential may be generated
While the Na+ gates closed, K+ gates open
Only a very strong stimulation can cause an action potential
explain “activation gate” and “inactivation gate”.
2 gates “activation gate” activates after threshold and “inactivation gate” closes after a specific period of time
