UTSC NROB61 Neurophysiology: Exam 3 - Questions with
Correct Answers
50 questions
1. Which glial cells regulate extracellular K+ and neurotransmitter uptake?
A. Microglia
B. Ependymal cells
C. Schwann cells
D. Astrocytes
Correct Answer: D. Astrocytes
Rationale: Astrocytes buffer K+ and take up glutamate.
2. Depolarization refers to:
A. Membrane potential becoming more negative
B. No change in potential
C. Membrane potential becoming less negative
D. Return to rest after hyperpolarization only
Correct Answer: C. Membrane potential becoming less negative
Rationale: Movement toward 0 mV or beyond.
3. Which part of a neuron usually integrates synaptic inputs and initiates the action potential?
A. Distal dendrite
B. Axon initial segment
C. Presynaptic terminal
D. Myelin sheath
Correct Answer: B. Axon initial segment
Rationale: It has the lowest threshold due to dense Na+ channels.
4. Microglia primarily function as:
A. Myelin producers
B. Ion pumps
C. Sensory receptors
D. Immune cells of the CNS
Correct Answer: D. Immune cells of the CNS
Rationale: They clear debris and respond to injury.
5. Open probability (Po) is:
A. The channel's conductance
B. The fraction of time a channel spends open
C. The number of channels
D. The reversal potential
Correct Answer: B. The fraction of time a channel spends open
Rationale: Ranges from 0 to 1.
6. A single channel passes 2 pA at a driving force of 100 mV. Its conductance is:
A. 200 pS
B. 20 pS
C. 2 pS
D. 50 pS
Correct Answer: B. 20 pS
Rationale: g = i/V = 2 pA / 0.1 V = 20 pS.
, 7. A JoVE patch-clamp protocol begins with which step before breaking into the cell?
A. Applying TTX
B. Forming a high-resistance seal with gentle suction
C. Inserting a sharp electrode
D. Staining the neuron
Correct Answer: B. Forming a high-resistance seal with gentle suction
Rationale: Seal formation precedes rupture.
8. Macroscopic current equals:
A. Number of channels x open probability x single-channel current
B. Single-channel current only
C. Open probability only
D. Number of channels x capacitance
Correct Answer: A. Number of channels x open probability x single-channel current
Rationale: I = N Po i.
9. [K+]out = 5 mM and [K+]in = 140 mM at 37 C. EK is about:
A. -89 mV
B. +89 mV
C. -61 mV
D. -120 mV
Correct Answer: A. -89 mV
Rationale: 61.5 x log10(5/140) = -89 mV.
10. Raising extracellular K+ from 5 to 20 mM will:
A. Hyperpolarize the neuron
B. Depolarize the neuron
C. Have no effect
D. Make EK more negative
Correct Answer: B. Depolarize the neuron
Rationale: EK becomes less negative.
11. Experimentally, the slope of Vm versus log [K+]out at high [K+]out approaches the Nernst
slope, showing that:
A. The resting membrane is dominated by K+ permeability
B. Na+ dominates
C. Cl- dominates
D. Vm is unrelated to K+
Correct Answer: A. The resting membrane is dominated by K+ permeability
Rationale: Deviations at low [K+] reflect Na+ permeability.
12. The Goldman-Hodgkin-Katz equation differs from the Nernst equation because it:
A. Applies to one ion only
B. Ignores concentrations
C. Applies only to Ca2+
D. Accounts for multiple ions and their relative permeabilities
Correct Answer: D. Accounts for multiple ions and their relative permeabilities
Rationale: Vm is a weighted balance.
Correct Answers
50 questions
1. Which glial cells regulate extracellular K+ and neurotransmitter uptake?
A. Microglia
B. Ependymal cells
C. Schwann cells
D. Astrocytes
Correct Answer: D. Astrocytes
Rationale: Astrocytes buffer K+ and take up glutamate.
2. Depolarization refers to:
A. Membrane potential becoming more negative
B. No change in potential
C. Membrane potential becoming less negative
D. Return to rest after hyperpolarization only
Correct Answer: C. Membrane potential becoming less negative
Rationale: Movement toward 0 mV or beyond.
3. Which part of a neuron usually integrates synaptic inputs and initiates the action potential?
A. Distal dendrite
B. Axon initial segment
C. Presynaptic terminal
D. Myelin sheath
Correct Answer: B. Axon initial segment
Rationale: It has the lowest threshold due to dense Na+ channels.
4. Microglia primarily function as:
A. Myelin producers
B. Ion pumps
C. Sensory receptors
D. Immune cells of the CNS
Correct Answer: D. Immune cells of the CNS
Rationale: They clear debris and respond to injury.
5. Open probability (Po) is:
A. The channel's conductance
B. The fraction of time a channel spends open
C. The number of channels
D. The reversal potential
Correct Answer: B. The fraction of time a channel spends open
Rationale: Ranges from 0 to 1.
6. A single channel passes 2 pA at a driving force of 100 mV. Its conductance is:
A. 200 pS
B. 20 pS
C. 2 pS
D. 50 pS
Correct Answer: B. 20 pS
Rationale: g = i/V = 2 pA / 0.1 V = 20 pS.
, 7. A JoVE patch-clamp protocol begins with which step before breaking into the cell?
A. Applying TTX
B. Forming a high-resistance seal with gentle suction
C. Inserting a sharp electrode
D. Staining the neuron
Correct Answer: B. Forming a high-resistance seal with gentle suction
Rationale: Seal formation precedes rupture.
8. Macroscopic current equals:
A. Number of channels x open probability x single-channel current
B. Single-channel current only
C. Open probability only
D. Number of channels x capacitance
Correct Answer: A. Number of channels x open probability x single-channel current
Rationale: I = N Po i.
9. [K+]out = 5 mM and [K+]in = 140 mM at 37 C. EK is about:
A. -89 mV
B. +89 mV
C. -61 mV
D. -120 mV
Correct Answer: A. -89 mV
Rationale: 61.5 x log10(5/140) = -89 mV.
10. Raising extracellular K+ from 5 to 20 mM will:
A. Hyperpolarize the neuron
B. Depolarize the neuron
C. Have no effect
D. Make EK more negative
Correct Answer: B. Depolarize the neuron
Rationale: EK becomes less negative.
11. Experimentally, the slope of Vm versus log [K+]out at high [K+]out approaches the Nernst
slope, showing that:
A. The resting membrane is dominated by K+ permeability
B. Na+ dominates
C. Cl- dominates
D. Vm is unrelated to K+
Correct Answer: A. The resting membrane is dominated by K+ permeability
Rationale: Deviations at low [K+] reflect Na+ permeability.
12. The Goldman-Hodgkin-Katz equation differs from the Nernst equation because it:
A. Applies to one ion only
B. Ignores concentrations
C. Applies only to Ca2+
D. Accounts for multiple ions and their relative permeabilities
Correct Answer: D. Accounts for multiple ions and their relative permeabilities
Rationale: Vm is a weighted balance.
