1. Neurons, Glia and Neurophysiology

2. Which of the following substances is least able to cross the blood-brain barrier?
Water
Sodium ions
Glucose
Leukocytes (White Blood Cells)

3. Which of the following substances is least able to cross the blood-brain barrier?
Water
Sodium ions
Glucose
Leukocytes (White Blood Cells)

4. Which of the following voltages would most likely be measured during the relative refractory period?
+30 mV
0 mV
-45 mV
-80 mV

5. Which of the following voltages would most likely be measured during the relative refractory period?
+30 mV
0 mV
-45 mV
-80 mV

6. Which of the following is probably going to propagate and action potential fastest?
A thin, unmyelinated axon
A thin, myelinated axon
A thick, unmyelinated axon
A thick, myelinated axon

7. Which of the following is probably going to propagate an action potential fastest?
A thin, unmyelinated axon
A thin, myelinated axon
A thick, unmyelinated axon
A thick, myelinated axon

8. What does a ligand-gated channel require in order to open?
Increase in concentration of Na+ ions
Binding of a neurotransmitter
Increase in concentration of K+ ions
Depolarisation of the membrane

9. What does a ligand-gated channel require in order to open?
Increase in concentration of Na+ ions
Binding of a neurotransmitter
Increase in concentration of K+ ions
Depolarisation of the membrane

10. A channel opens on a postsynaptic membrane that causes a negative ion (anion) to enter the cell. What type of graded potential is this?
Depolarising
Repolarising
Hyperpolarizing
Non-polarizing

11. A channel opens on a postsynaptic membrane that causes a negative ion (anion) to enter the cell. What type of graded potential is this?
Depolarising
Repolarising
Hyperpolarizing
Non-polarizing

12. Which neurotransmitter is released at the neuromuscular junction?
Norepinephrine
Serotonin
Dopamine
Acetylcholine

13. Which neurotransmitter is released at the neuromuscular junction?
Norepinephrine
Serotonin
Dopamine
Acetylcholine

14. A column is a collection of neuron cell bodies
group of tracts in the spinal cord
bundle of white matter with a common origin and destination
none of the above

15. A column is a collection of neuron cell bodies
group of tracts in the spinal cord
bundle of white matter with a common origin and destination
none of the above

16. A neuron’s resting membrane potential is established and maintained by
a high concentration of K+ in the extracellular fluid and a high concentration of Na- in the cytosol,
the plasma membrane’s higher permeability to Na- because of the presence of numerous Na- leakage channels,
differences in both ion concentrations and electrical gradients,
the fact that there are numerous large, nondiffusible anions in the cytosol,
sodium–potassium pumps that help to maintain the proper distribution of sodium and potassium.
1, 2, and 5
1, 2, and 3
2, 3, and 4
3, 4, and 5
1, 2, 3, 4, and 5

17. A neuron’s resting membrane potential is established and maintained by
a high concentration of K+ in the extracellular fluid and a high concentration of Na- in the cytosol,
the plasma membrane’s higher permeability to Na- because of the presence of numerous Na- leakage channels,
differences in both ion concentrations and electrical gradients,
the fact that there are numerous large, nondiffusible anions in the cytosol,
sodium–potassium pumps that help to maintain the proper distribution of sodium and potassium.
1, 2, and 5
1, 2, and 3
2, 3, and 4
3, 4, and 5
1, 2, 3, 4, and 5

18. Which of the following is something that glia do NOT do?
Synchronize activity of a group of axons
Remove waste material
Dilate blood vessels to increase blood flow to the most active brain areas
Conduct action potential

19. Which of the following is something that glia do NOT do?
Synchronize activity of a group of axons
Remove waste material
Dilate blood vessels to increase blood flow to the most active brain areas
Conduct action potential

20. During the rising portion of the action potential, which ions are moving across the membrane and in which direction?
Sodium ions move out
Sodium ions move in
Both sodium and potassium ions move in
Potassium ions move in

21. During the rising portion of the action potential, which ions are moving across the membrane and in which direction?
Sodium ions move out
Sodium ions move in
Both sodium and potassium ions move in
Potassium ions move in

22. Which of the following statements are true?
If the excitatory effect is greater than the inhibitory effect but less than the threshold of stimulation, the result is a subthreshold EPSP.
If the excitatory effect is greater than the inhibitory effect and reaches or surpasses the threshold level of stimulation, the result is a threshold or suprathreshold EPSP and one or more nerve impulses.
If the inhibitory effect is greater than the excitatory effect, the membrane hyperpolarizes, resulting in inhibition of the postsynaptic neuron and the inability of the neuron to generate a nerve impulse.
The greater the summation of hyperpolarizations, the more likely a nerve impulse will be initiated.
1 and 4
2 and 4
1, 3, and 4
2, 3, and 4
1, 2, and 3

23. Which of the following statements are true?
If the excitatory effect is greater than the inhibitory effect but less than the threshold of stimulation, the result is a subthreshold EPSP.
If the excitatory effect is greater than the inhibitory effect and reaches or surpasses the threshold level of stimulation, the result is a threshold or suprathreshold EPSP and one or more nerve impulses.
If the inhibitory effect is greater than the excitatory effect, the membrane hyperpolarizes, resulting in inhibition of the postsynaptic neuron and the inability of the neuron to generate a nerve impulse.
The greater the summation of hyperpolarizations, the more likely a nerve impulse will be initiated.
1 and 4
2 and 4
1, 3, and 4
2, 3, and 4
1, 2, and 3

24. Which of the following statements are true?
Ion channels can be either gated or ungated.
Ion channels allow for the development of graded potentials and action potentials.
Voltage-gated channels open in response to changes in membrane potential.
Ligand-gated channels open due to the presence of specific chemicals.
A graded potential is useful for communication over long distances.
1, 2, and 3
1, 2, 3, and 4
2, 3, and 5
2, 3, 4, and 5
1, 3, and 5

25. Which of the following statements are true?
Ion channels can be either gated or ungated.
Ion channels allow for the development of graded potentials and action potentials.
Voltage-gated channels open in response to changes in membrane potential.
Ligand-gated channels open due to the presence of specific chemicals.
A graded potential is useful for communication over long distances.
1, 2, and 3
1, 2, 3, and 4
2, 3, and 5
2, 3, 4, and 5
1, 3, and 5

26. Which of the following statements are true?
The frequency of impulses and number of activated sensory neurons encodes differences in stimuli intensity.
Larger-diameter axons conduct nerve impulses faster than smaller-diameter ones.
Continuous conduction is faster than saltatory conduction.
The presence or absence of a myelin sheath is an important factor that determines the speed of nerve impulse propagation.
Action potentials are localized, but graded potentials are propagated.
1, 3, and 5
3 and 4
2, 4, and 5
2 and 4
1, 2, and 4

27. Which of the following statements are true?
The frequency of impulses and number of activated sensory neurons encodes differences in stimuli intensity.
Larger-diameter axons conduct nerve impulses faster than smaller-diameter ones.
Continuous conduction is faster than saltatory conduction.
The presence or absence of a myelin sheath is an important factor that determines the speed of nerve impulse propagation.
Action potentials are localized, but graded potentials are propagated.
1, 3, and 5
3 and 4
2, 4, and 5
2 and 4
1, 2, and 4

28. After the action potential reaches its peak, the potential across the membrane falls toward its resting level. What accounts for this recovery?
The sodium–potassium pump removes the extra sodium.
Potassium ions move out because their channels are open and the electrical gradient pushes them out.
Potassium ions move out because their channels are open and the concentration gradient pushes them out.
Potassium ions move in.

29. After the action potential reaches its peak, the potential across the membrane falls toward its resting level. What accounts for this recovery?
The sodium–potassium pump removes the extra sodium.
Potassium ions move out because their channels are open and the electrical gradient pushes them out.
Potassium ions move out because their channels are open and the concentration gradient pushes them out.
Potassium ions move in.

30. What was Otto Loewi’s evidence that neurotransmission depends on the release of chemicals?
He applied adrenaline to muscles and saw them contract.
He applied drugs at various synapses and observed excitatory and inhibitory postsynaptic potentials.
He stimulated one frog’s heart, collected fluid around it, transferred it to another frog’s heart, and saw change in its heart rate.
He stimulated certain nerves, collected the fluid around their terminals, and analyzed the contents chemically.

31. What was Otto Loewi’s evidence that neurotransmission depends on the release of chemicals?
He applied adrenaline to muscles and saw them contract.
He applied drugs at various synapses and observed excitatory and inhibitory postsynaptic potentials.
He stimulated one frog’s heart, collected fluid around it, transferred it to another frog’s heart, and saw change in its heart rate.
He stimulated certain nerves, collected the fluid around their terminals, and analyzed the contents chemically.

32. Suppose you want to cause the presynaptic terminal of an axon to release its transmitter. How could you do so without an action potential?
Decrease the temperature at the synapse.
Use an electrode to produce IPSPs in the postsynaptic neuron.
Inject water into the presynaptic terminal.
Inject calcium into the presynaptic terminal.

33. Suppose you want to cause the presynaptic terminal of an axon to release its transmitter. How could you do so without an action potential?
Decrease the temperature at the synapse.
Use an electrode to produce IPSPs in the postsynaptic neuron.
Inject water into the presynaptic terminal.
Inject calcium into the presynaptic terminal.

34. In which of these ways does a metabotropic synapse differ from an ionotropic synapse?
Its effects are slower to start and last longer.
Its effects are faster to start and last longer.
Its effects are slower to start and briefer in duration.
Its effects are faster to start and briefer in duration.

35. In which of these ways does a metabotropic synapse differ from an ionotropic synapse?
Its effects are slower to start and last longer.
Its effects are faster to start and last longer.
Its effects are slower to start and briefer in duration.
Its effects are faster to start and briefer in duration.

36. Assume that an EPSP is being generated on the dendritic membrane
Assume that an EPSP is being generated on the dendritic membrane. Which will occur?
Specific Na+ channels will open
Specific K+ channels will open
A single type of channel will open, permitting simultaneous flow of Na+ and K+
Na+ channels will open first and then close as K+ channels open.

37. Assume that an EPSP is being generated on the dendritic membrane
Assume that an EPSP is being generated on the dendritic membrane. Which will occur?
Specific Na+ channels will open
Specific K+ channels will open
A single type of channel will open, permitting simultaneous flow of Na+ and K+
Na+ channels will open first and then close as K+ channels open.

38. In the laboratory, researchers can apply an electrical stimulus at any point along the axon, making action potentials travel in both directions from the point of stimulation. An action potential moving in the usual direction, away from the axon hillock, is said to be traveling in the orthodromic direction. An action potential traveling toward the axon hillock is traveling in the antidromic direction. If we started an orthodromic action potential at the start of the axon and an antidromic action potential at the opposite end of the axon, what would happen when they met at the center? Why?

40. Assume you touched a hot stove with your finger
Assume you touched a hot stove with your finger. Contraction of the biceps muscle causes flexion (bending) of the elbow, whereas contraction of the triceps muscle causes extension (straightening) of the elbow. What pattern of postsynaptic potentials (EPSPs and IPSPs) would you expect to be initiated as a reflex in the cell bodies of the neurons controlling these muscles to pull your hand away from the painful stimulus?

42. GABAergic interneurons activate synaptic GABAA receptors on pyramidal neurons. The pyramidal cells are interconnected, and release glutamate when excited, thus activating postsynaptic glutamate receptors (GLU-R). (a) Immature pyramidal neurons have high concentrations of Cl-. The neurons take up Cl- by NKCC1, an inwardly-directed Na+,K+-2Cl- cotransporter, overwhelming Cl- extrusion by KCC2, an outwardly-directed K+-Cl- cotransporter. The Cl- equilibrium potential is therefore positive to the resting membrane potential, and activation of GABAA receptor-channels results in Cl- efflux and depolarization. This depolarization (and excitation) may cause the release of glutamate, which further induces excitation by activation of GLU-R, rendering neonatal cortex highly susceptible to seizures. Thus, NKCC1 activity facilitates neonatal seizures.
Developmental changes in chloride homeostasis during development. A: during development, the intracellular chloride concentration decreases. In the immature neurons, efflux of the negatively charged chloride ions produces inward electric current and depolarization. In the mature neurons, chloride enters the cell and produces outward electric current and hyperpolarization. B: developmental change in the intracellular chloride is due to the changes in the expression of the two major chloride cotransporters, KCC2 and NKCC1. Chloride extruder KCC2 is expressed late in development, whereas NKCC1, which accumulates chloride in the cell, is more expressed in the immature neurons.

43. Bipolar cells have centre-surround receptive fields
Bipolar cells have centre-surround receptive fields. The centre of each such field receives direct connections from a small number of photoreceptors, while the surrounding area (called the "surround") receives inputs from a larger set of photoreceptors whose activity is relayed by the horizontal cells.
Light shining on the centre of a bipolar cell's receptive field and light shining on the surround produce opposite changes in the cell's membrane potential.
If light is shined on the centre of an ON-centre cell’s receptive field, the first change is a hyperpolarization of the photoreceptor cell, causing depolarization of the bipolar cell, because of the inhibitory nature of the synapse between them. This depolarization in turn excites the following cell, a ganglion cell, causing it to emit action potentials at a higher frequency.
Conversely, if light were shined on the surround of the receptive field of this same ON-centre bipolar cell, it would become hyperpolarized. In contrast, another kind of bipolar cell becomes depolarized when an area of darkness strikes the centre of its receptive field, and hyperpolarized when it strikes the surround. Bipolar cells of this kind are called OFF-centre cells.
In the absence of light, photoreceptors release their neurotransmitter, glutamate, continuously. Consequently, the glutamate receptors of OFF-centre bipolar cells are excitatory, because the absence of light must stimulate them. Similarly, the receptors of ON-centre bipolar cells are inhibitory, because light striking the photoreceptors at the centre of their receptive fields hyperpolarizes them and reduces their release of glutamate. Since glutamate is an inhibitory neurotransmitter, reducing it excites the bipolar cell.
Thus it is the excitatory or inhibitory nature of the glutamate receptors that determines the type of receptive field for bipolar cells.