Exam 1 - Practice Test

Question 1

If the inactivate gates of the Na+ channels were hindered so that they couldn’t close as fully and reliably as normal, then the following is the most likely effect:

a) the rising phase of the action potential would be slower
b) the falling phase of the action potential would be slower
c) resting membrane potential would hyperpolarize
d) the absolute refractory period would be shorter

Answer 1

Answer

b) the falling phase of the action potential would be slower

Question 2

The current that brings the membrane potential back to rest following the peak of an EPSP is:

a) the voltage-gated potassium current
b) the voltage-gated sodium current
c) the leak current
d) the Na/K pump current

Answer 2

Answer

c) the leak current

Question 3

All voltage-gated channels have gates. The fastest of all the voltage gates associated with the action potential is the _______ gate on the voltage-gated _____ channel.
The gate most responsible for determining the length of the relative refractory period of the action potential is
the _______ gate on the voltage-gated ______channel.

Answer 3

Answer

All voltage-gated channels have gates. The fastest of all the voltage gates associated with the action potential is the (activation) gate on the voltage-gated ( Na+ ) channel.
The gate most responsible for determining the length of the relative refractory period of the action potential is
the (activation) gate on the voltage-gated ( K+ ) channel.

Question 4

The driving force for an ion increases as the difference between the membrane potential
and the _______ of that ion is increased.
Multiplying the driving force by the ________ of that ion yields the current of that ion.

Answer 4

Answer

The driving force for an ion increases as the difference between the membrane potential 
and the (equilibrium potential) of that ion is increased. 
Multiplying the driving force by the (conductance (or g)) of that ion yields the current of that ion.

Question 5

This kind of synapse doesn’t involve the use of any neurotransmitter _________.

Answer 5

Answer

This kind of synapse doesn’t involve the use of any neurotransmitter ( electrical or gap junction ) .

Question 6

Vesicles containing __________ are made in the soma and transported to the synaptic terminal.

Answer 6

Answer

Vesicles containing peptides or neuropeptides or proteins or peptide neurotransmitters are made in the soma and transported to the synaptic terminal. (*give 1 point for “neurotransmitters”)

Question 7

Name a type of glial cell that provide myelin for axons in the brain: ________ .
Name a glial cell that regulates the extracellular environment in the brain: ______ .

Answer 7

Answer

Name a type of glial cell that provide myelin for axons in the brain: ( oligodendrocytes or oligodendroglia (NOT Schwann cells—they are not in the brain) ) .
Name a glial cell that regulates the extracellular environment in the brain: ( astrocytes ) .

Question 8

The relative concentrations of _______ outside and inside of the membrane mostly determines Vrest, as it is the ion that has the greatest passive permeability with respect to the membrane.

Answer 8

Answer

The relative concentrations of ( K+ ) outside and inside of the membrane mostly determines Vrest, as it is the ion that has the greatest passive permeability with respect to the membrane.

Question 9

19. Define the term “neuron doctrine” and describe one piece of evidence that lent support for this theory when it was formulated in the late 1800s-early 1900s.

Answer 9

it was formulated in the late 1800s-early 1900s. 
Elementary structural (cellular) component of the brain and elementary signalling mechanism of the brain. Use of Golgi stain (silver nitrate) produced first images of individual cells in brain tissue. Ramon y Cajal used these images to create detailed drawings of how cells compose elements of the nervous system.

Question 10

20. In describing myelination of axons, your textbook mentions the important fact that wider axons (ie, larger diameter axons) can afford to have the nodes of Ranvier (the gaps between myelin on an axon) spaced at longer intervals, so that the segments of axon that are myelinated are longer. Explain why wider axons can afford such increased distances between the nodes of Ranvier.

Answer 10

The nodes of Ranvier allow a recharging of the AP via the voltage gated channels that are otherwise not available in the myelinated segments. Relative to the total current of the AP, the current that leaks out of an axon through a myelinated segment is proportionally smaller in a wider axon due to the decreased internal resistance (ri) of the wider (larger diameter) axon. Because of this, the relative decrease in voltage from one node to the next is diminished, allowing extra length from node to node before a critical drop below AP threshold is reached.

Question 11

2. Which of the following best describes the effect of myelination:

Answer 11

increases rm

Question 12

3. Which of the following best describes the effect of an activated adrenergic alpha2R:

Answer 12

increases gK

Question 13

4. 120 mV is closest to the equilibrium potential of what ion in a neuron?

Answer 13

calcium

Question 14

5. Briefly offer one explanation for why fewer peptidergic vesicles are released relative to aminergic (ie, amino acid or amine) vesicles in any single time frame.

Answer 14

A peptidergic vesicle typically requires a burst of APs to be released, whereas an aminergic vesicle is often released after just a single AP. [one could also argue that peptidergic vesicles couldn’t be released at as high a rate as aminergic because peptidergic vesicles are more costly—made at the soma and transported to the terminal]

Question 15

6. The reversal potential for some ionotropic receptors is about 0 mV. How can a reversal potential be 0 mV when no one ion has an equilibrium potential of 0 mV (see p. 127)?

Answer 15

The channel pore of this receptor must be permeable to more than one ion, so that the reversal potential is somewhere between the equilibrium potentials of those ions in proportion to their respective conductances (similar to Vr).

[The AMPAR, for example, has a reversal potential of 0 mV because the activated channel is permeable to both Na+ than K+, but slightly more permeable to Na+ than K+, and so the reversal potential is a little closer to ENa (62 mV) than EK (-80 mV).]

Question 16

7. For the following, fill in the blank with the word AMPA or GABA-A, in accordance with the receptor type that best matches the statement provided:
   a) The approximate reversal potential is 0 mV ________
   b) These activated receptors are permeable to Cl- ________
   c) These receptors usually provide excitation ________

Answer 16

7. For the following, fill in the blank with the word AMPA or GABA-A, in accordance with the receptor type that best matches the statement provided:
   a) The approximate reversal potential is 0 mV AMPA
   b) These activated receptors are permeable to Cl- GABA-A
   c) These receptors are considered excitatory AMPA

Question 17

8. All of the following can convey signals between neurons.
   Rank them in order of speed: 1 for fastest response, 3 for slowest response (2 points)

___ G-protein-coupled receptor (aka, metabotropic receptor)

___ electrical synapse (aka, gap-junction synapses)

___ transmitter-gated ion channel (aka, ionotropic receptor)

Answer 17

8. All of the following can convey signals between neurons.
   Rank them in order of speed: 1 for fastest response, 3 for slowest response (2 points)

3 G-protein-coupled receptor (aka, metabotropic receptor)

1 electrical synapse (aka, gap-junction synapses)

2 transmitter-gated ion channel (aka, ionotropic receptor

Question 18

9. For many pyramidal neurons in the cortex, the largest amplitude of an EPSP given from a presynaptic neuron might be less than 1 mV. How is it possible that this pyramidal neuron is made to fire APs when the largest EPSP from any single presynaptic neuron is less than 1 mV?

Answer 18

A single pyramidal neuron may be the postsynaptic target of thousands of other excitatory pyramidal neurons. If a few dozen of those excitatory synapses are activated at nearly the same time (ie, within the timeframe of a single EPSP), then those EPSPs will summate, producing a very large depolarization that can produce an AP.

Question 19

10. For the following, fill in the blank with the abbreviation NMJ (for neuromuscular junction) or PYR (for a cortical pyramidal-pyramidal neuron synapse), in accordance with kind of synaptic connection that best matches the statement provided:
    a) The number of release sites is greater than 100 ________
    b) The receptors mediating transmission are nAChRs ________
    c) The postsynaptic receptors are found on dendrites ________

Answer 19

10. For the following, fill in the blank with the abbreviation NMJ (for neuromuscular junction) or PYR (for a cortical pyramidal-pyramidal neuron synapse), in accordance with kind of synaptic connection that best matches the statement provided:
    a) The number of release sites is greater than 100 NMJ _
    b) The receptors mediating transmission are nAChRs NMJ _
    c) The postsynaptic receptors are found on dendrites PYR _

Question 20

11. What is the approximate reversal potential for a GABA-A receptor? _________

Answer 20

11. What is the approximate reversal potential for a GABA-A receptor? -65 mV_____

Question 21

12. The activation of ß receptors results in a GPCR cascade that ultimately results in the phosphorylation and closing of potassium channels in neurons (answering with an abbreviation is acceptable, if they were used in class or in the book)
    a) What enzyme phosphorylates the potassium channels in this receptor activated cascade?
    b) What enzyme is activated to increase the production of cAMP from ATP?
    c) What neurotransmitter is released to stimulate ß receptors?

Answer 21

12. The activation of ß receptors results in a GPCR cascade that ultimately results in the phosphorylation and closing of potassium channels in neurons (answering with an abbreviation is acceptable, if they were used in class or in the book)

a) What enzyme phosphorylates the potassium channels in this receptor activated cascade?
PKA (protein kinase A)

b) What enzyme is activated to increase the production of cAMP from ATP?
AC (adenylyl cyclase)

c) What neurotransmitter is released to stimulate ß receptors?
NE (norepinephrine)

Question 22

13. Name an ionotropic receptor that has a large calcium conductance: _______________

Answer 22

13. Name an ionotropic receptor that has a large calcium conductance: NMDAR

Question 23

14. Name three different GPCRs that can cause an increase in the membrane’s conductance for potassium:

Answer 23

14. Name three different GPCRs that can cause an increase in the membrane’s conductance for potassium:

Question 24

1. Which of the following values would be most affected in a neuron by decreasing the extracellular sodium concentration ([Na⁺]_o)?
   a) the resting membrane potential
   b) the reversal potential of the GABA_A receptor
   c) the reversal potential of the AMPA receptor
   d) the passive conductance for sodium in the membrane, gNa.

Answer 24

1. Which of the following values would be most affected in a neuron by decreasing the extracellular sodium concentration ([Na⁺]_o)?

☐a) the resting membrane potential

☐b)the reversal potential of the GABA_A receptor

☒c) the reversal potential of the AMPA receptor

☐d) the passive conductance for sodium in the membrane, gNa.

Question 25

2. Comparing two dendrites, the one with the higher ____________ ratio will have the greater length constant.
   a) r_m/r_i
   b) r_i/r_m
   c) r_i
   d) r_m

Answer 25

2. Comparing two dendrites, the one with the higher ____________ ratio will have the greater length constant.

☒ a) r_m/r_i

☐ b) r_i/r_m

☐ c) r_i

☐ d) r_m

Question 26

5. Increasing the diameter of an axon increases the speed of propagation, mostly because of:
   a) decrease in r_i
   b) decrease in r_m
   c) increase in r_i
   d) increase in r_m

Answer 26

5. Increasing the diameter of an axon increases the speed of propagation, mostly because of:

a) decrease in r_i

b) decrease in r_m
c) increase in r_i
d) increase in r_m

Question 27

6. Out of all the ions we’ve discussed, the resting membrane potential (Vrest) is closest to the equilibrium potential of

Answer 27

6. Out of all the ions we’ve discussed, the resting membrane potential (Vrest) is closest to the equilibrium potential of Cl^- .

Question 28

7. The ion with the most depolarized equilibrium potential is , as it has an extremely low intracellular concentration that is actively maintained.

Answer 28

7. The ion with the most depolarized equilibrium potential is Ca²⁺ , as it has an extremely low intracellular concentration that is actively maintained.

Question 29

8. The following list of events roughly describing a GPCR cascade are out of order. Please place them in the correct order by placing a “1”, “2” or “3” or “4” next to each step, indicating which event comes first, second, third and fourth:

Adenylyl cyclase converts ATP into cAMP

The g-protein separates into two subunits, the a-GTP and the bg

PKA phosphorylates K⁺ channels

Norepinephrine (NE) binds and activates a ß_R

Answer 29

8. The following list of events roughly describing a GPCR cascade are out of order. Please place them in the correct order by placing a “1”, “2” or “3” or “4” next to each step, indicating which event comes first, second, third and fourth:

3 Adenylyl cyclase converts ATP into cAMP

2 The g-protein separates into two subunits, the a-GTP and the bg

4 PKA phosphorylates K⁺ channels

1 Norepinephrine (NE) binds and activates a ß_R

Question 30

9. When the receptor is opened by glutamate and depolarization, it becomes permeable to three different ions, including calcium.

Answer 30

9. When the NMDA receptor is opened by glutamate and depolarization, it becomes permeable to three different ions, including calcium.

Question 31

10. The conductance for this ion is increased when GABA binds to GABA_A receptors: .

Answer 31

10. The conductance for this ion is increased when GABA binds to GABA_A receptors: Cl^- .

Question 32

11. All voltage-gated channels have gates. The fastest of all the voltage gates associated with the action potential is the _____ gate on the voltage-gated ____ channel.

The gate most responsible for determining the length of the relative refractory period of the action potential is

the _____ gate on the voltage-gated _____ channel.

Answer 32

11. All voltage-gated channels have gates. The fastest of all the voltage gates associated with the action potential is the activation gate on the voltage-gated Na⁺ channel.

The gate most responsible for determining the length of the relative refractory period of the action potential is the activation gate on the voltage-gated K⁺ channel.

Question 33

12. For the following, fill in the blank with the abbreviation NMJ (for neuromuscular junction), PYR (for a cortical pyramidal-pyramidal neuron synapse), or BOTH in accordance with kind of synaptic connection that best matches the statement provided. If the statement applies to BOTH kinds of synapses, then write BOTH:
    a) Every action potential (AP) in the axon produces an AP in the postsynaptic cell ___ .
    b) The predominant excitatory neurotransmitter involved is glutamate ____ .
    c) The amplitude of the EPSP produced from a single vesicle is about 0.2 mV ____ .
    d) The neurotransmitter is effectively cleared from the synapse via diffusion and reuptake ____ .

Answer 33

12. For the following, fill in the blank with the abbreviation NMJ (for neuromuscular junction), PYR (for a cortical pyramidal-pyramidal neuron synapse), or BOTH in accordance with kind of synaptic connection that best matches the statement provided. If the statement applies to BOTH kinds of synapses, then write BOTH:
    a) Every action potential (AP) in the axon produces an AP in the postsynaptic cell NMJ.
    b) The predominant excitatory neurotransmitter involved is glutamate PYR.
    c) The amplitude of the EPSP produced from a single vesicle is about 0.2 mV BOTH.
    d) The neurotransmitter is effectively cleared from the synapse via diffusion and reuptake PYR.

Question 34

13. The driving force for an ion increases as the difference between the membrane potential

and the _____ of that ion is increased.

Multiplying the driving force by the _____ of that ion yields the current of that ion.

Answer 34

13. The driving force for an ion increases as the difference between the membrane potential

and the equilibrium potential of that ion is increased.

Multiplying the driving force by the conductance (or g) of that ion yields the current of that ion.

Question 35

14. This kind of synapse doesn’t involve the use of any neurotransmitter _________ .

Answer 35

14. This kind of synapse doesn’t involve the use of any neurotransmitter electrical or gap junction.

Question 36

15. Vesicles containing _______ are made in the soma and transported to the synaptic terminal.

Answer 36

15. Vesicles containing peptides or neuropeptides or proteins or peptide neurotransmitters are made in the soma and transported to the synaptic terminal. (*give 1 point for “neurotransmitters”)

Question 37

16. Norepinephrine binding to a2 receptors results in an increased conductance of _____ ions.

Answer 37

16. Norepinephrine binding to a2 receptors results in an increased conductance of K⁺ ions.

Question 38

21. It is possible for a molecule of glutamate to be released from a synaptic terminal and then find itself back in the same terminal. Describe the journey of this molecule, beginning with its location in a synaptic vesicle and ending with the molecule in another synaptic vesicle in the same terminal. A correct answer will use the terms exocytosis, endocytosis, calcium and reuptake.

Answer 38

The AP depolarizes the terminal membrane, and this depolarization activates the vgated Ca²⁺ channels. This produces an influx of Ca²⁺ ions which bind proteins docking the vesicle to the terminal membrane, causing the vesicle to fuse with the terminal membrane and release the glutamate in a process called exocytosis. Then a new, empty vesicle is formed from the terminal membrane through endocytosis, a process by which a piece of the terminal membrane invaginates and pinches off as a new vesicle. Reuptake occurs when glutamate is pumped back into the terminal membrane, and a separate process is employed to pump the glutamate from inside the terminal into the new vesicle.

Question 39

Name a glial cell that regulates the extracellular environment in the brain: _____ .

Answer 39

Name a glial cell that regulates the extracellular environment in the brain: astrocytes .

Question 40

18. The relative concentrations of ____ outside and inside of the membrane mostly determines Vrest, as it is the ion that has the greatest passive permeability with respect to the membrane.

Question 41

22. “Acetylcholine (ACh) can function as an excitatory or inhibitory neurotransmitter, depending on where it is released.” Is this statement true or false? Explain your answer. A correct answer will define the difference between excitatory vs. inhibitory neurotransmission and will also include supporting information about two different ACh receptors, explaining why one can be considered excitatory and the other inhibitory.

Answer 41

Excitation is neurotransmission which encourages APs, and inhibition is neurotransmission which discourages APs. Ionotropic nAChRs at the NMJ are excitatory because when they bind to ACh they conduct Na+ and K+ with a reversal potential of 0 mV, which is well above threshold and therefore drives Vm towards and beyond threshold. Metabotropic mAChRs in the heart are inhibitory, as binding of ACh activates g-proteins which open up K+ channels via the shortcut pathway, producing a hyperpolarizing current