Module 3: Lecture 4 Flashcards
True or False
Action potentials all have the same magnitude but the frequency effects how and what is cellularly communicated
True
What is the refractory period?
we are unable to generate a second action potential until the first one has completed
the time period in between
What are the 2 general phases of the refractory period?
- Absolute refractory period
- Relative refractory period
What is the Absolute refractory period
period where we cannot generate a second action potential
What is the beginning to end of the Absolute refractory period
initial to resting membrane
What is the Relative refractory period?
where another action potential can occur, because the sodium channels have reset
How do we restore the original concentrations of sodium and potassium?
sodium/potassium ATPase pump
How does the sodium-potassium pump work?
- the opening for the Na+/K+ pump is facing intracellularly
- it has a very high affinity for sodium, it has a active site specifically for sodium which will bind to it
- then we phosphorylate the pump, we bring in ATP and bind a phosphate group to the pump
- as the phosphate uses its energy the protein membrane changes it’s opening to be extracellularly, which allows sodium ions to diffuse out
- now the pump has a high affinity for potassium which it now binds to the specific potassium active sites
- now the phosphate group will leave the pump, reverting the pump towards the inside of the cell allowing potassium to diffuse into the cell
Is the sodium-potassium pump always “ON”?
Yasss
True of False
The sodium-potassium pump counterbalances the rate of passive leakage
True
Is the sodium-potassium pump an active or passive process?
primary active transport, it requires energy
What are the 4 zones of the nerve cell?
- Input zone
- Trigger zone
- Conducting zone
- Output zone
What happens in the input zone?
(dendrites and cell body)
- where the cell receives all of its communications from other nerves
- this is where all the graded potentials occur
- it includes the cell body (has a nucleus) and dendrites (finger-like structure)
- the message goes from the dendrites to the cell body to the trigger zone or axon hillock
What happens in the trigger zone?
(Axon Hillocks)
- where the action potentials are initiated
- there is a high concentration of voltage-gated sodium and potassium channels
What happens in the conducting zone?
(axon)
- where an action potential is propagated
- can be a long or a short distance
What happens in the output zone?
(axon terminals)
- where the axon terminals are and they send off the continued messages
what is the point of the dendrites?
they greatly increase the surface area, to receive multiple-cell communications
What are the 2 methods of action potentials that will travel down the axon?
- Contiguous conduction
- Saltatory conduction
How does the contiguous conduction work?
- it uses the initial gated channels that reach the threshold to allow one action potential to occur
- then once all the sodium is in the cell is travels along the membrane triggers more action potentials all the way down the axon
True or False
The contiguous conduction is a self-perpetuating cycle that automatic
True
Why does the action potential only travel in one directon?
due to refractory period
What is saltatory conduction
action potentials will jump down patches due to myelinated fibers
Are myelin sheets hydrophobic or hydrophilic?
hydrophobic, very good insulator
what is the peripheral nervous cells?
nerve cells not including the spinal cord
What are the central nervous cells?
nerve cells in the spinal cord
How does myelination occur?
due to Schwann cells
- individuals cells wrap around the axon leaving a gap called the nodes of ranvier
What are the nervous cells in the central nervous system called?
oligodendrocytes
What are oligodendrocytes?
nerve cells with large bodies and foot-like projections
- wrap multiple different axons in myelin sheath
What is the point of having cells wrapped in myelinated sheath?
- increases insulating effects increasing cell communication
How long are the nodes of ranvier?
2 microns in length
How often do node of ranvier occur? and why?
- every millimeters or so
- we need them because theres voltage-gated ion channels at the nodes for action potentials to occur
