The Nervous System Flashcards
What is the soma in a neuron? What does it contain?
Cell body
Nucleus, ER, and ribosomes
What is a collection of cell bodies called in the CNS?
Nucleus
What is a collection of cell bodies called in the PNS?
Ganglion
What is the role of astrocytes? 3
- Nourish neurons
- Form the blood/brain barrier
- Perform the scarring process in the CNS, which reduces the potential for neural regrowth
What is the role of ependymal cells?
Produce cerebrospinal fluid
What is the role of oligodendrocytes?
Produce myelin in CNS
What is the role of Scwann cells?
Produce myelin in PNS
During the action potential, which ion channel opens first?
Na+
What is the voltage of the resting membrane potential?
-70mV
What enzyme maintains the resting membrane potential?
Na+/K+ ATPase
What is the threshold for the first ion channel to open?
-50mV
What regulates the Na+ channel to close?
Full depolarization at +35mV
During the action potential, which ion channel opens second?
The K+ channel
At what voltage does the second channel open?
+35mV
What regulates the K+ channel to close?
Hyperpolarization to slightly below -70mV
What is the absolute refractory period?
When the axon is GETTING depolarizaed and getting hyperpolarized: the cell is unable to fire another action potential –> whenever Na+ and K+ ion channels are open –> think of the bell on the curve, until -70
What is the relative refractory period?
When the axon requires a larger than normal stimulus to fire an action potential: from hyperpolarization to resting potential
What are the Nodes of Ranvier?
Exposed areas of demyelinated axons
What are the parts of the synapse?
- Synaptic bouton of one neuron
- Synaptic cleft
- Membrane of post-synaptic cell
What does the speed of the impulse down the axon depend on? 2 things
Which effect is more significant?
- Length: decrease length = increase conduction
2. Cross-sectional area: increase = increase conduction –> more significant
Which neurons have very little myelin?
Sensory neurons
What do local anesthetics inhibit?
The Na+ ion channel
What ion channel opens once the impulse has reached the synaptic bouton? Where do these ions go?
Ca+, come inside the cell
What is white matter?
Myelinated axons
What is grey matter?
Unmyelinated cell body and dendrites
What is the difference between monosynaptic and polysynaptic reflexes?
The use of interneurons
What is the equation to calculate a membrane potential based on the concentrations of only 1 ion?
Nernst:
E = 61.5/z(charge of ion) x log [ion out] / [ion in]
What is the equation to calculate a membrane potential based on the concentrations of multiple ions?
Goldman-Hodgkin-Katz:
Vm = 61.5 x log (Pion1.[ion out] + Pion2.[ion out]) / (Pion1.[ion in] + Pion2.[ion in])
P = permeability
BUT: invert denominator for ions with a different charge
Which one is the presynaptic neuron?
The one releasing the NTs
Which one is the postsynaptic neuron?
The one receiving the NTs
Why do the concentrations of K+ ions play a much larger role than the Na+ concentrations in determining the membrane potential?
Because K+ has a higher permeability than Na+
What neuron type is responsible for pilo erection? Sensory or motor?
Motor
Inside the cell, are there more Na+ or K+ ions?
K +
What is the normal movement of ions to maintain the resting membrane potential?
3 Na+ ions move out for every 2 K+ ions moved in
Outside the cell, are there more Na+ or K+ ions?
Na+
Inside the cell: negative or positive?
Negative
Outside the cell: negative or positive?
Positive
What are the 3 statuses for the Na+ ion channel?
Open, closed, or inactivated
When does inactivation of Na+ channels occur? What is the purpose?
When the membrane potential is 35, this is the fast closing of the gate, the other one is slow
What is the status of the Na+ channel for another action potential to be fired?
Closed
What does a higher magnitude action potential change?
The frequency of the action potential
Are the Na+ ions going in or out?
In
Are the K+ ions going in or out?
Out
When K+ blood concentration is low, how will this affect the action potential?
When the K+ blood concentration is low, the drive for the K+ ion to leave the cell is high, which means the membrane potential will reach even lower values during hyperpolarization = will rneed a higher stimulus for an action potential to happen
When K+ blood concentration is high, how will this affect the action potential?
The neuron will be more excitable because the resting membrane potential will be higher
What happens on the axon at the unmyelinated portions?
+ charges flow down and open Na+ channels as they go –> recharging
Does the Ca2+ go in or out at the axon terminal?
In the cell!
How to calculate the change in electric potential energy of an ion crossing the membrane?
U = Delta V . q
Delta V = difference between outside (0V) and inside (-70mV)
q = charge of the ion: each charge = 1.6 x 10^-19 C
