Exam 1 The Structure of Neurons to Action Potential

Microtubules are organized in a + and - orientation with

+ end at ends of axons and the - end facing the nucleus

Radial glial cells are considered the stem cells of the brain, arising from neuroepithelial cells. In humans, at which age are there the highest number of radial glial cells?

Embryonic

Which type of glial cell increases the conduction velocity of action potentials in the peripheral nervous system by promoting saltatory conduction?

Schwann cells

What prevents the action potential from propagating backwards?

Sodium channel inactivation

Voltage gated sodium channels have how many transmembrane domains per individual protein?

24

The rate at which neurons can fire action potentials is most dependent on

Action potential duration and relative refractory period

The BOLD signal in functional MRI is most dependent upon changes in blood flow in the brain that are regulated by which type of cell?

Astrocytes

Golgi's Reticular Theory and Ramon y Cajal's Neuron Doctrine rivaled each other in the way neurons were portrayed in the brain. How were the two theories different?

Cajal's theory is now more widely accepted because of its hypothesis, which we now know is true, that neurons are individual, non-continuous cells that allow for cell to cell communication in the brain through synapses.

Increasing the concentration of extracellular K+ from 5mM to 30mM will do what to the neuronal membrane potential?

Cause a depolarization

When many ion channels are opened, what happens to conductance and resistance?

Conductance increases, resistance decreases

Pseudo-unipolar neurons have a single axon coming off the cell body that then splits off into two axons and are usually found in

Dorsal root ganglion

Regulating intracellular calcium is critical for neurons because too much intracellular calcium can cause excitotoxicity. Which of the following organelles play a key role in buffering calcium in neurons?

Endoplasmic reticulum and mitochondria

True/False: The equilibrium potential of potassium is the membrane voltage at which no potassium ions are physically allowed to cross the membrane.

False

Na+ channels and K+ channels are different in their time course for opening and closing. What is the typical time course for a Na+ ion channel?

Fast and inactivating

What kind of transport is dependent on kinesin motor proteins?

Fast anterograde

Increasing intensity and duration of a stimulus will increase action potential _____, but its _____ remains the same.

Frequency, amplitude

There are two types of refractory periods: absolute and relative. What does the absolute refractory period depend on?

Inactivation of Na+ channels

How can neurons decrease resistance inside their axons (Ri)?

Increasing axon diameter

Translation is the process of creating peptides from mRNAs. What is the rate limiting step in translation regulation? This is the step that is most heavily influenced by cellular kinases and is involved in neuronal plasticity.

Initiation

Neurons, sitting at resting membrane potential, normally have a high _____ potassium ion concentration and a high _____ sodium ion concentration.

Intracellular, extracellular

In voltage-clamp experiments, a downward deflection in current usually indicates

Inward current (e.g. depolarization)

What has the capacity to activate microglia?

Ischemia, bacteria, and cytokines

Reversal potential can be reached when permeability for a given ion becomes so high that it dominates the overall permeability of the cell. As sodium's permeability gets higher and higher during an action potential and the membrane voltage becomes more and more positive, what happens to its driving force?

It gets smaller and smaller, eventually hitting its reversal potential.

The permeability of ions can vary at different stages of excitability and during the action potential. When a cell is at resting membrane potential, the cell membrane is most permeable to which ion?

K+

The resting membrane potential in neurons is primarily determined by which two ions?

K+ and Na+

What magnitudes of tau and lambda might you expect in a synaptic connection that is highly efficacious (e.g. a synapse that has undergone LTP)?

Large tau and large lambda

Which type of axon would have the fastest action potential conduction velocity?

Large, myelinated axons

Local mRNA translation can control neuronal plasticity. Which of the following are types of neuronal plasticity that are regulated by local translation?

Long term potentiation and long term depression

When blocking specific ion channels, significant changes in current can be observed during the action potential. What can be observed with TTX, the Na+ channel blocker?

Mainly outward currents remained.

The permeability of ions can vary at different stages of excitability and during the action potential. When the cell first reaches action potential threshold, the cell membrane is becoming most permeable to which ion?

Na+

Changes in membrane potential can induce changes in current and ion flow. When sodium's reversal potential is exceeded to the more positive side (e.g. +70 mV), what happens to Na+ flow in the neuron?

Na+ flows out of the cell.

Approximately how excitable are neurons during the peak of an action potential when voltage gated sodium channels are entering the inactivation phase?

Not excitable

Myelin in the CNS is made by

Oligodendrocytes

In what direction would a positively-charged ion flow if ion channels permeable to the ion opened when the resting membrane potential was more positive than the equilibrium potential for that ion?

Out of the cell

How would you describe the current generated from negatively-charged ions flowing into the cell?

Outward current

A cell's resting membrane potential can be calculated through the Goldman Equation. Goldman's Equation is different than the Nernst Equation because it introduces the concept of what?

Permeability of individual ions

When microglia are activated they enter a state where they release cytokines and take on many properties that are normally associated with macrophages in the periphery during an immune challenge. What is this state called?

Phagocytic state

The value of the resting membrane potential is most dependent upon the permeability of which ion species according to the Goldman equation?

Potassium

What would happen to the potassium ion conductance if you added tetrodotoxin (TTX) to your electrophysiological preparation?

Potassium ion conductance would not change.

In the knee jerk response reflex the flexor muscle (hamstring) is inhibited by

Release of glutamate by the muscle spindle afferent onto a GABAergic interneuron that then inhibits the motor neuron innervating the hamstring

Which of the following would occur if a neuron had increased sodium ion permeability?

Resting membrane potential would become more positive.

The transcriptome for a given tissue refers to the mRNAs that are expressed in that organ. Which of the following statements are correct?

The brain's transcriptome is distinct compared to other tissues in the human body.

If the myelin sheath surrounding the axon of a neuron were to degrade, which of the following would occur?

The length constant would decrease.

Which of the following statements about action potentials are FALSE?

They are usually induced by hyperpolarization.

How do dendrites usually increase their capacity to passively conduct current?

They increase their diameter causing the time and length constant to increase.

The Nernst equation incorporates multiple variables such as ion concentration, temperature, and the charge of ions. What is the main purpose of using the Nernst equation?

To solve for the equilibrium potential/reversal potential of an individual ion

True/False: The length constant (l) has a greater value in axons that are myelinated.

True

True/False: The sodium-potassium ATPase pump is an example of a transmembrane ion channel that requires energy.

True

True/False: The voltage sensor of voltage gated sodium channels is made up of amino acids with positive charge.

True

Ohm's law is written as Vm - Vequilibrium potential = I*R when considering currents in the nervous system because when Vm = Vequilibrium potential there is _____ net current flow.

Zero