Foundations Of Neural Signaling And Pharmacological Mechanisms Practice Tests

Question 1

If a neuron has a membrane resistance of $R_m = 100\, \Omega\cdot m^2$ and a surface area of $A = 10^{-8}\, m^2$, calculate the total membrane resistance $R_{total}$ in $\Omega$.

Accepted Answer

10000000000

Question 2

Given the Nernst equation $E_{ion} = \frac{RT}{zF} \ln\left(\frac{[ion]_{out}}{[ion]_{in}}\right)$, if the extracellular concentration of $K^+$ is $5\, mM$ and the intracellular concentration is $150\, mM$, determine the equilibrium potential at $37^\circ C$ (where $\frac{RT}{F} \ln(10) \approx 61.5\, mV$).

Accepted Answer

Option A

Answer

Option B

Answer

Option C

Answer

Option D

Question 3

A neuron receives two EPSPs of $5\, mV$ and one IPSP of $3\, mV$ simultaneously at the same dendritic location. Calculate the net change in membrane potential at the axon hillock, assuming no signal decay.

Accepted Answer

7 mV

Question 4

If the time constant $	au$ of a neuronal membrane is $20\, ms$, how long does it take for a graded potential to reach approximately $63\%$ of its final steady-state value after a step current injection?

Accepted Answer

Option A

Answer

Option B

Answer

Option C

Answer

Option D

Question 5

In a myelinated axon, the density of voltage-gated $Na^+$ channels is significantly higher at the nodes of Ranvier compared to the internodal regions covered by myelin.

Accepted Answer

True

Answer

False

Question 6

Calculate the driving force for $Na^+$ ions if the membrane potential $V_m$ is $-70\, mV$ and the equilibrium potential for $Na^+$ ($E_{Na}$) is $+60\, mV$.

Accepted Answer

-130 mV

Question 7

Which of the following glial cells are primarily responsible for maintaining the chemical environment of the CNS and forming the blood-brain barrier?

Accepted Answer

Option A

Answer

Option B

Answer

Option C

Answer

Option D

Question 8

If the conductance of $K^+$ ($g_K$) is $20\, nS$ and the driving force is $-20\, mV$, calculate the current $I_K$ flowing across the membrane.

Accepted Answer

Option A

Answer

Option B

Answer

Option C

Answer

Option D

Question 9

During the absolute refractory period, a second action potential can be triggered if the stimulus intensity is increased above the threshold.

Accepted Answer

False

Answer

True

Question 10

A synaptic vesicle contains $10,000$ neurotransmitter molecules. If $20\%$ of these are released into the synaptic cleft during exocytosis, how many molecules are released?

Accepted Answer

2000

Question 11

A researcher measures the concentration of dopamine in the synaptic cleft over time $t$ (in seconds) following a stimulus, modeled by the function $C(t) = C_0 e^{-kt}$. If the reuptake rate constant $k$ is $0.15 	ext{ s}^{-1}$, calculate the time required for the concentration to reach $10\%$ of its initial value $C_0$.

Accepted Answer

15.35 seconds

Answer

6.67 seconds

Answer

23.03 seconds

Answer

1.50 seconds

Question 12

In a study of receptor occupancy, the fraction of receptors occupied $Y$ is given by $Y = \frac{[D]}{K_d + [D]}$, where $[D]$ is the drug concentration and $K_d$ is the dissociation constant. If a drug has a $K_d = 5 	ext{ nM}$ and the concentration of the drug is $15 	ext{ nM}$, determine the percentage of receptors occupied.

Accepted Answer

75%

Answer

25%

Answer

50%

Answer

80%

Question 13

A patient is administered a drug that acts as a competitive antagonist. If the original $EC_{50}$ of the agonist is $2 	ext{ nM}$ and the presence of the antagonist shifts the $EC_{50}$ to $10 	ext{ nM}$, calculate the dose ratio (DR) defined as $DR = \frac{EC_{50, 	ext{with antagonist}}}{EC_{50, 	ext{without antagonist}}}$.

Accepted Answer

5

Question 14

Which of the following scenarios describe mechanisms that would increase the net effect of a neurotransmitter in the synaptic cleft? Select all that apply.

Answer

Inhibition of the reuptake transporter protein

Answer

Inhibition of the monoamine oxidase (MAO) enzyme

Answer

Activation of presynaptic autoreceptors that inhibit neurotransmitter release

Answer

Increased enzymatic degradation of the neurotransmitter

Question 15

If a drug follows first-order elimination kinetics such that the plasma concentration at time $t$ is $C(t) = C_0 e^{-kt}$, and the half-life $t_{1/2}$ is $4$ hours, the elimination rate constant $k$ is approximately $0.173 	ext{ hr}^{-1}$.

Accepted Answer

True

Answer

False

Question 16

In a double-blind study, the probability of a patient showing improvement due to the placebo effect is $P(A) = 0.30$, and the probability of improvement due to the active drug is $P(B) = 0.60$. Assuming these are independent events, what is the probability that a patient shows improvement from either the placebo effect or the drug?

Accepted Answer

Option A

Answer

Option B

Answer

Option C

Answer

Option D

Question 17

A drug exhibits tolerance such that the effective dose required to achieve the same behavioral response increases linearly over time. If the initial dose $D_0 = 5 	ext{ mg}$ and the dose increases by $2 	ext{ mg}$ every week, calculate the total dose required at the start of the 5th week (where $n=1$ is the first week).

Accepted Answer

13 mg

Question 18

A neuron has a resting membrane potential of $V_m = -70	ext{ mV}$. If the extracellular concentration of $K^+$ is $5	ext{ mM}$ and the intracellular concentration is $140	ext{ mM}$, calculate the equilibrium potential $E_K$ using the Nernst equation $E_K = \frac{RT}{zF} \ln\left(\frac{[K^+]_{out}}{[K^+]_{in}}ight)$, assuming $\frac{RT}{zF} \approx 61.5	ext{ mV}$ at body temperature. Determine the direction of net ion flow if the membrane potential is suddenly clamped to $-90	ext{ mV}$.

Accepted Answer

The equilibrium potential is approximately $-94	ext{ mV}$, and $K^+$ will flow out of the cell.

Answer

The equilibrium potential is approximately $-94	ext{ mV}$, and $K^+$ will flow into the cell.

Answer

The equilibrium potential is approximately $-45	ext{ mV}$, and $K^+$ will flow out of the cell.

Answer

The equilibrium potential is approximately $-45	ext{ mV}$, and $K^+$ will flow into the cell.

Question 19

A postsynaptic neuron receives two simultaneous inputs: an EPSP of $+15	ext{ mV}$ and an IPSP of $-8	ext{ mV}$. If the threshold for an action potential is $V_{th} = -55	ext{ mV}$ and the resting potential is $V_{rest} = -65	ext{ mV}$, calculate the final membrane potential $V_{final}$ and determine if an action potential is triggered.

Accepted Answer

$V_{final} = -58	ext{ mV}$; no action potential is triggered.

Question 20

A drug acts as a competitive antagonist at a receptor site. If the baseline response to a neurotransmitter is $R = \frac{E_{max} \cdot [L]}{K_d + [L]}$, where $[L]$ is the ligand concentration and $K_d$ is the dissociation constant, how does the presence of the antagonist $[I]$ modify the effective $K_d$ to $K_d'$ given the inhibition constant $K_i$?

Accepted Answer

$K_d' = K_d \left(1 + \frac{[I]}{K_i}\right)$

Answer

$K_d' = K_d \left(1 - \frac{[I]}{K_i}\right)$

Answer

$K_d' = K_d \cdot \frac{[I]}{K_i}$

Answer

$K_d' = K_d + \frac{[I]}{K_i}$

Foundations Of Neural Signaling And Pharmacological Mechanisms Practice Tests

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Foundations of Neural Signaling and Pharmacological Mechanisms

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