BILD 140 Neurobiology

In a two-compartment model of a cell with a K+-permeable membrane and a 10-fold excess of K+ in the inside compartment, how would the membrane potential change if all K+ ions were replaced by Na+ ions

. No potential would be generated.

Damage to glial cells can have profound negative effects on the nervous system. Link the outcome (labeled 1,2,3,4) that would occur upon damage to the following four cell types (starting at the top). 3 points Cell types: Oligodendrocytes Astrocytes Microglia Schwann Cells

1. debris buildup and/or accumulation of unneeded synapses 2. loss of myelination in the CNS 3. loss of Blood Brain Barrier (BBB) and/or extracellular environment disruption 4. loss of myelination in the PNS a. a. 2,3,1,4

While recording from a neuron using the current c;amp method, you measure a steady-state 8 mV depolarization after an injection of 40 pA. Given a time constant of 6 ms, determine the membrane capacitance.

30 pf V=IR Change into R=V/I then out into Cm=t/RM

levels of deoxygenated blood flow in the whole brain to indicate where neuron metabolism increases by neural activities

BOLD fMRI

Which factor is important in determining the membrane potential when there are multiple permeant ions?

Both the concentration gradient and membrane permeability of the individual ionic species

You are performing a voltage clamp experiment in a neuron in vitro, and obtaining the following I-V curve for a channel (channel B). What type of ion channel is this? Explain your reasoning. Graph straight hypotenuse

Either leak Cl- or leak K + channel- non voltage gated if curved its na or calcium- voltage gated

electric field fluctuations resulting from currents of cortical activities under the scalp

Electroencephalography (EEG)

As electrical currents transverse the length of the axon, current diffuses out of the membrane via leak channels; as the distance from the site of current injection increases, the size of recorded potentials decreases. What equation explains this relationship? 2 points Equation W: Vt = Vmax×(1-e-t/t) Equation X: Vx = V0×e-x/l Equation Y: V = I×R Equation Z: t = Rm×Cm

Equation X

fluorescent signals that correlates with intracellular calcium concentration, which is increased by action potentials

Fluorescence calcium imaging

Which statement about passive current involved in action potential propagation is most accurate?

It opens voltage-dependent Na+ channels in the adjacent region of axon

How will a neuron respond to an injection of negative current?

It will become hyperpolarized.

In a two-compartment model of a cell with a potassium- and calcium-permeable membrane and a 10-fold excess of potassium in the inside compartment, how would the membrane potential change if all potassium ions were replaced by calcium ions?

It would be reduced by half.

Protein Z is produced in the cell body of a neuron, but it's function is at the far end of an axon terminal. This protein would take days to reach the axon by passive diffusion inside the intracellular cytosol. Instead, it must be actively trafficked to the distal axon, using the motor protein ____ along the cytoskeletal element __________ composed of _______.

Kinesin, microtubules, tubulin

While studying an unknown ion channel, you find that it is open for an average of 3 ms. If you observe 22 open events over a 100 ms recording, what is the open probability of this channel?

Open probability is time open divided by total time Po = time open / total time Po = (22 events * 3 ms each) / 100 ms recording time Po = 0.66

How does membrane permeability to K+ (PK) and Na+ (PNa) change during an action potential?

PK exceeds PNa at rest; PNa temporarily increases during the action potential.

levels of radio-labeled neurotransmitters or glucose analog in the whole brain to indicate where synaptic activity or consumption of glucose increase due to neural activities

Positron Emission Tomography (PET)

During which phase of an action potential does membrane permeability to Na+ exceed membrane permeability to K+?

Rising and overshoot phases

hich cell produces myelin in the nerves of the peripheral nervous system?

Schwann cell

What drug would you apply to block voltage-gated K+ channels?

TEA

What drug would you apply to block voltage-gated Na+ channels?

TTX

What is the role of the S4 domain in mammalian K+ channels? Is a similar domain present in the bacterial KcsA channel? Why or why not?

The S4 domain is enriched in positive charges, and together with S1-3 senses transmembrane voltage [2 pts] . The Bacterial KcsA channel only possesses 2 transmembrane domains, which correspond to the S5 and S6 domains in mammalian channels [2 pts]. Without S1-4, KcsA is not voltage-dependent

A neuron has received enough stimulation to fire an action potential; it also has been treated with TEA, a K+ channel blocker. Which outcome is possible?

The cell will initially depolarize, but repolarization will take much longer because it relies only on ion pumps.

What happens to a neuron's length constant if most of the ion channels close?

The length constant increases

What structural elements are used for travel in pattern B?

from axon terminal to dendrite microtubules

What motor protein mediates axoplasmic transport in pattern C?

from detrite to axon terminal is kinesin

What accounts for the effects of Ouabain, which causes slow membrane potential increases in neurons?

inhibits the Na/K pump, causing Na to build up in the cell

Fill in the blanks: Long-distance axonal transport is mediated by motor proteins moving along _______, with _____ proteins moving cargo away from the cell body and ____ proteins moving cargo towards the cell body.

micro tubules, kinesin, dynesin

Which of the following cytoskeleton components is the smallest diameter?

microfilaments ps. microtubules are the largest

What motor protein mediates axoplasmic transport in pattern A? in dendrite

myosin

Which statement about the ionic permeability of cell membranes is true?

n resting nerve cells, the membrane is quite permeable to potassium.

n a two-compartment model of a cell with a K+-permeable membrane, at K+ equilibrium potential, there is _______ flux of K+ ions

no net

What glial cell wraps myelin sheaths around the axons in the CNS?

oligodendrocytes

You are measuring the resting membrane potential of a neuron in an ex vivo brain slice, and record a value of -68 mV. What change, if any, would you expect to see upon application of Ouabain?

raise in membrane voltage

You are recording a neuron's resting membrane potential. If you add KCl to the external medium, what will happen to the resting potential?

raise in membrane voltage

Fill in the blank. The cell membrane behaves as a _______, in its ability to impede the movement of charge

resistor

In depolarization ,______ are moving ______ the cell.

sodium ; into

You are recording action potentials from a neuron. How will the action potential be affected if you lower the amount of sodium in the extracellular space?

the action potential will be suppressed

What is the neuron doctrine?

the theory that the nervous system is composed of distinct units

How does capacitance relate to resistance?

their product is the time constant tau

Which of the following statement(s) are true about neuronal membranes?

they resist current flow they are composed of a phospholipid bilayer

When applying the indicated current injection, what membrane potential do you expect to reach?

use equation V=IR I=injected R=Resitance

Imagine you induce a mutation to the voltage-gated Na+ channel to cause its inactivation gate to slow. How would this influence the shape of the action potential

wider action potential

In a current clamp experiment, you inject enough current into a neuron to bring the voltage from -80mV to a steady state of -60 mV. Given a time constant of 5 ms, how long will it take for the voltage to drop to -71 mV after current injection ends?

Vt = Vmax·(e^ -t/τ) Vt=9mv from -80 to -71mv Vmax=20mv from -80 to -60 b.4ms

Under which circumstances is the Goldman-Hodgkin-Katz equation equivalent to the Nernst equation?

When a membrane is permeable to only one ion.

Can unmyelinated axons generate and propagate action potentials?

Yes

Taking the subunit of the mammalian voltage-gated K+ channel as an example, which transmembrane domain(s) correspond(s) to which category?

a) What domain(s) are enriched in positive charges? S4 [1 pt] b) What domain(s) are connected to the pore loop? S5 + S6 [1 pt] c) What domain(s) are voltage-sensing? S1-4 [2 pts if all, 1 pt if only S4] d) What domains are conserved with the bacterial KcsA channel? S5 + S6 [1 pt]

When injecting a negative current into a neuron, why does the effect on voltage depend on the number of open channels?

because more open channels means larger conductance

Fill in the blank. The cell membrane behaves as a _______, in its ability to store charge.

capacitor

What best describes the capacitive properties of a neuronal membrane?

charge stored across an insulator

A student new to neuroscience research is practicing recording resting membrane potentials from giant squid axons. During one of the trials, the resting membrane potential, which is normally around -60 mV, measured -15 mV. Which statement best describes what might have occurred during the experiment?

The student added too much potassium to the extracellular solution, reduces potassium gradient and causes depolarization

What type of ion channel is this? What drug would you use to block this current? Curved

This is a voltage-gated Na+ channel You would block it with TTX (tetrodotoxin)