Practice Exam 1: Neurobiology
Question 1: Explain how you can do optogenetic experiments with Channelrhodopsins.
Answer: Optogenetic experiments with Channelrhodopsins involve using light to control neurons that have been genetically modified to express
light-sensitive proteins. Channelrhodopsins are light-sensitive ion channels that can depolarize neurons when activated by specific wavelengths
of light. To express Channelrhodopsins in specific neurons, researchers use transfection in cultured neurons or engineer transgenic animals. The
responses of neurons or animals to light activation of the channelrhodopsins can be recorded with electrophysiology.
Question 2: Glia cells have various functions in the nervous system. Glia cells: Schwann cells, Astrocytes, Oligodendrocytes, Microglia.
Functions: phagocytosis of surplus material, formation of myelin sheath in the PNS, secretion of cytokines, forms part of blood brain barrier,
support of neurons through regulation of extracellular ion concentrations, reuptake of neurotransmitters, formation of myelin sheath in the CNS.
Answer:
• Schwann cells: formation of myelin sheath in the PNS
• Astrocytes: forms part of blood brain barrier, support of neurons through regulation of extracellular ion concentrations, reuptake of
neurotransmitters
• Oligodendrocytes: formation of myelin sheath in the CNS
• Microglia: phagocytosis of surplus material, secretion of cytokines
Question 3: What is antibody staining used for?
a. Visualising specific protein locations in the cell
b. Retrograde tracing of connections
c. Identifying neuron-specific gene transcription
d. Anterograde tracing of connections
e. Visualising structural changes due to a lesion
Answer: Visualising specific protein locations in the cell
Question 4: The image shows part of the primary visual cortex. The image is an example of which of the following
stainings?
a. Golgi
b. Antibody staining against microglia
c. Intracellular dye injection
d. Nissle
Answer: Nissle
Question 5: Which of the following brain scanning techniques has the highest spatial resolution?
a. Positron Emission Tomografie (PET)
b. Computerized Tomografie (CT)
c. Magnetoencephalografie (MEG)
d. Functional Magnetic Resonance Imaging (fMRI)
e. Magnetic Resonance Imaging (MRI)
f. Single-Photon Emission Computerized Tomografie (SPECT)
Answer: Magnetic Resonance Imaging (MRI)
Question 6: What is a measured membrane potential of +58 mV consistent with?
a. 10 mM Cl- in the cell, 100 mM Cl- outside the cell
b. 100 mM K+ in the cell, 10 mM K+ outside the cell
c. 100 mM K+ in the cell, 100 mM Na+ outside the cell
d. 10 mM Na+ in the cell, 100 mM Na+ outside the cell
Answer: 10 mM Na+ in the cell, 100 mM Na+ outside the cell
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, Question 7: What properties of the axonal membrane make axons poor conductors?
a. The length of the axon
b. The ion channels in the membrane consume current
c. Current runs through the membrane
d. The capacity of the lipid membrane
Answer: Current runs through the membrane. The capacity of the lipid membrane.
Question 8: What explains that action potentials only travel in one direction?
a. Leakage currents in the axons, such that return of action potentials is prevented
b. The polarised orientation of microtubules in the axon
c. The refractory period at a site where an action potential has just passed
d. The voltage dependency of potassium channels
e. The voltage dependency of sodium channels
Answer: The refractory period at a site where an action potential has just passed.
Question 9: Hodgkin and Huxley studied the resting membrane potential of the squid giant axon. What were their findings?
a. Increase in extracellular sodium depolarised the membrane potential
b. Changing sodium or potassium had the same effect on the membrane potential
c. Increase in extracellular sodium hyperpolarised the membrane potential
d. Increase in extracellular potassium depolarised the membrane potential
e. Increase in extracellular potassium hyperpolarised the membrane potential
Answer: Increase in extracellular potassium depolarised the membrane potential.
Question 10: What causes the different electrical signals in nerve cells?
a. Negative charges bound to the inside and outside of the cell membrane.
b. Ion currents through the cell membrane.
c. Positive charges bound to the inside and outside of the cell membrane.
d. The movement of charged proteins in the plane of the cell membrane.
Answer: Ion currents through the cell membrane.
Question 11: Explain the difference between active and passive electrical membrane properties.
Answer:
Passive properties:
• Govern how electrical signals passively spread and decay within the neuron. They are essential for determining the neuron’s electrical
behavior in the absence of action potential.
• Membrane resistance is determined by the density and properties of leak channels (non-voltage-gated ion channels).
• Membrane capacitance is determined by the surface area of the lipid bilayer of the plasma membrane.
Active properties:
• Voltage-Gated Ion Channels, including Na+ and K+ channels, each contributing to different phases of the action potential.
• Involve energy-dependent processes that enable the generation and propagation of action potentials and synaptic transmission. These
properties allow neurons to actively transmit information over long distances without the loss of signal strength.
Question 12: Rapid depolarization during the rising phase of the action potential is partly determined by an important difference between Na+
and K+ channels. Which difference is the determining factor in this?
a. Na+ channels inactivate, K+ channels do not
b. Na+ channels are more sensitive to potential differences than K+ channels
c. Na+ has a larger driving force than K+
d. Na+ channels open and close faster than K+ channels
Answer: Na+ channels open and close faster than K+ channels.
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Question 1: Explain how you can do optogenetic experiments with Channelrhodopsins.
Answer: Optogenetic experiments with Channelrhodopsins involve using light to control neurons that have been genetically modified to express
light-sensitive proteins. Channelrhodopsins are light-sensitive ion channels that can depolarize neurons when activated by specific wavelengths
of light. To express Channelrhodopsins in specific neurons, researchers use transfection in cultured neurons or engineer transgenic animals. The
responses of neurons or animals to light activation of the channelrhodopsins can be recorded with electrophysiology.
Question 2: Glia cells have various functions in the nervous system. Glia cells: Schwann cells, Astrocytes, Oligodendrocytes, Microglia.
Functions: phagocytosis of surplus material, formation of myelin sheath in the PNS, secretion of cytokines, forms part of blood brain barrier,
support of neurons through regulation of extracellular ion concentrations, reuptake of neurotransmitters, formation of myelin sheath in the CNS.
Answer:
• Schwann cells: formation of myelin sheath in the PNS
• Astrocytes: forms part of blood brain barrier, support of neurons through regulation of extracellular ion concentrations, reuptake of
neurotransmitters
• Oligodendrocytes: formation of myelin sheath in the CNS
• Microglia: phagocytosis of surplus material, secretion of cytokines
Question 3: What is antibody staining used for?
a. Visualising specific protein locations in the cell
b. Retrograde tracing of connections
c. Identifying neuron-specific gene transcription
d. Anterograde tracing of connections
e. Visualising structural changes due to a lesion
Answer: Visualising specific protein locations in the cell
Question 4: The image shows part of the primary visual cortex. The image is an example of which of the following
stainings?
a. Golgi
b. Antibody staining against microglia
c. Intracellular dye injection
d. Nissle
Answer: Nissle
Question 5: Which of the following brain scanning techniques has the highest spatial resolution?
a. Positron Emission Tomografie (PET)
b. Computerized Tomografie (CT)
c. Magnetoencephalografie (MEG)
d. Functional Magnetic Resonance Imaging (fMRI)
e. Magnetic Resonance Imaging (MRI)
f. Single-Photon Emission Computerized Tomografie (SPECT)
Answer: Magnetic Resonance Imaging (MRI)
Question 6: What is a measured membrane potential of +58 mV consistent with?
a. 10 mM Cl- in the cell, 100 mM Cl- outside the cell
b. 100 mM K+ in the cell, 10 mM K+ outside the cell
c. 100 mM K+ in the cell, 100 mM Na+ outside the cell
d. 10 mM Na+ in the cell, 100 mM Na+ outside the cell
Answer: 10 mM Na+ in the cell, 100 mM Na+ outside the cell
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, Question 7: What properties of the axonal membrane make axons poor conductors?
a. The length of the axon
b. The ion channels in the membrane consume current
c. Current runs through the membrane
d. The capacity of the lipid membrane
Answer: Current runs through the membrane. The capacity of the lipid membrane.
Question 8: What explains that action potentials only travel in one direction?
a. Leakage currents in the axons, such that return of action potentials is prevented
b. The polarised orientation of microtubules in the axon
c. The refractory period at a site where an action potential has just passed
d. The voltage dependency of potassium channels
e. The voltage dependency of sodium channels
Answer: The refractory period at a site where an action potential has just passed.
Question 9: Hodgkin and Huxley studied the resting membrane potential of the squid giant axon. What were their findings?
a. Increase in extracellular sodium depolarised the membrane potential
b. Changing sodium or potassium had the same effect on the membrane potential
c. Increase in extracellular sodium hyperpolarised the membrane potential
d. Increase in extracellular potassium depolarised the membrane potential
e. Increase in extracellular potassium hyperpolarised the membrane potential
Answer: Increase in extracellular potassium depolarised the membrane potential.
Question 10: What causes the different electrical signals in nerve cells?
a. Negative charges bound to the inside and outside of the cell membrane.
b. Ion currents through the cell membrane.
c. Positive charges bound to the inside and outside of the cell membrane.
d. The movement of charged proteins in the plane of the cell membrane.
Answer: Ion currents through the cell membrane.
Question 11: Explain the difference between active and passive electrical membrane properties.
Answer:
Passive properties:
• Govern how electrical signals passively spread and decay within the neuron. They are essential for determining the neuron’s electrical
behavior in the absence of action potential.
• Membrane resistance is determined by the density and properties of leak channels (non-voltage-gated ion channels).
• Membrane capacitance is determined by the surface area of the lipid bilayer of the plasma membrane.
Active properties:
• Voltage-Gated Ion Channels, including Na+ and K+ channels, each contributing to different phases of the action potential.
• Involve energy-dependent processes that enable the generation and propagation of action potentials and synaptic transmission. These
properties allow neurons to actively transmit information over long distances without the loss of signal strength.
Question 12: Rapid depolarization during the rising phase of the action potential is partly determined by an important difference between Na+
and K+ channels. Which difference is the determining factor in this?
a. Na+ channels inactivate, K+ channels do not
b. Na+ channels are more sensitive to potential differences than K+ channels
c. Na+ has a larger driving force than K+
d. Na+ channels open and close faster than K+ channels
Answer: Na+ channels open and close faster than K+ channels.
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