HW

Question 1

[1] gradient and [2] gradient are the electrical and chemical forces respectively, that control movement of ions across a membrane.

Please note: When the word respectively is used in a statement/question, this provides order of information. Make sure your answers are in the order indicated in the question (i.e, answer 1 = the electrical force; answer 2 = the chemical force). Having the correct forces, but in the incorrect order will result in the full loss of points.

Make sure to read all questions carefully for grammatical cues such as this throughout the semester.

Answer 1

1) Electrical

2) Concentration

Question 2

Ions move from an area of [1] concentration to an area of [2] concentration.

Answer 2

1) HIGH

2) low

Question 3

T/F
Depolarization is when the membrane potential is less negative than the resting membrane potential, increasing the likelihood the neuron will generate an action potential; whereas hyperpolarization is when the membrane potential is more negative than the resting membrane potential, decreasing the likelihood the neuron will generate an action potential.

Answer 3

T

Question 4

Indicate if True or False: Binding of a neurotransmitter to a receptor creating an excitatory post-synaptic potential (EPSP) will always result in generation of an action potential in the postsynaptic neuron.

If false, please correct the statement by adding, deleting, replacing or rearranging as few words as possible to make the statement true. Make sure if a correction is necessary that your correction includes what the statement should say (do not simply add words such as ‘not’, ‘will’, ‘will not’, ‘does’ or ‘does not’) and that it maintains the focus of the original statement - when or how often generation of an EPSP will result in an action potential.

Answer 4

Binding of a neurotransmitter to a receptor creating an excitatory postsynaptic potential (EPSP) will sometimes result in the generation of an action potential in the postsynaptic neuron

Question 5

Using Figure 6.7, p. 127, In your own words and in 2 sentences or less, concisely describe the difference in location of release of a neurotransmitter versus a neuromodulator. Be concise, yet specific!
3)
Make sure to limit your answer to the question begin asked. Do not include information that is extraneous to this question (such as number of neurons impacted or duration of action). Doing so will result in the loss of points.

Answer 5

Neuromodulator is released into the extracellular fluid away from the synaptic cleft. A neurotransmitter is relased directly into the extracellular fluid in the synaptic cleft.

Question 6

Match the type of channel with the stimulus that opens it.

1) Modality-gated
2) Ligand-gated
3) Voltage-gated
4) Leak

Answer 6

1) Opens in response to a sensory stimulus (e.g., mechanical, chemical, or thermal)
2) Opens in response to binding of a substance to a membrane receptor
3) Opens in response to a change in charge differential across a membrane
4) Continuously open

Question 7

Resting membrane potential (RMP) is maintained by the presence of large [1] inside the neuron, diffusion of ions through [2], and the [3] which move ions into or out of the cell against their concentration and/or electrical gradients. Of these, only the [4] is an active process.

Answer 7

1) Anions
2) Leak channels
3) Sodium-Potassium Pump
4) Sodium-Potassium Pump

Question 8

The absolute refractory period helps prevent backflow of depolarization. Which of the following best describes the absolute refractory period?

Answer 8

Occurs in the early stages of an action potential when sodium channels cannot be reopened

Question 9

Indicate if True or False: In convergent input a single neuron synapses on many other neurons, whereas in divergent input many neurons synapse on a single neuron.

Answer 9

In divergent input a single neuron synapses on many other neurons, whereas in convergent input many neurons synapse on a single neuron.

Question 10

At a synapse, the local potential can either be depolaring or hyperpolarizing. A local potential that results in depolarization is said to be [1] (excitatory/inhibitory), and one that results in hyperpolarization is said to be [2] (excitatory/inhibitory). The name of a depolarizing local potential at a synapse is called an [3], which is abbreviated [4]. A hyperpolarizing local potential at a synapse is called an [5], which is abbreviated [6].

Answer 10

1) excitatory
2) inhibitory
3) excitatory postsynaptic potential
4) EPSP
5) inhibitory postsynaptic potential
6) IPSP

Question 11

Indicate if True or False: A local potential is a change in membrane potential that spreads only a very small distance along the membrane of a neuron.

If false, please correct the statement by adding, deleting, replacing or rearranging as few words as possible to make the statement true. Make sure if a correction is necessary that your correction includes what the statement should say (do not simply add words such as ‘not’, ‘will’, ‘will not’, ‘does’ or ‘does not’) and that it maintains the focus of the original statement - how far a local potential spreads along the membrane

Answer 11

True

Question 12

Indicate if True or False: Any stimulus that reaches threshold for an action potential will create the same size of the action potential, regardless of the intensity of the stimulus.

If false, please correct the statement by adding, deleting, replacing or rearranging as few words as possible to make the statement true. Make sure if a correction is necessary that your correction includes what the statement should say (do not simply add words such as ‘not’, ‘will’, ‘will not’, ‘does’ or ‘does not’) and that it maintains the focus of the original statement - size of the action potential relative to stimulus intensity

Answer 12

True

Question 13

In Figure 5.8 on pg. 109, in part B it states that voltage-gated Na+ channels open and begin to depolarize the axon. This is an error. What type of channel should this panel say?

Answer 13

In part B it should say modality-gated or ligand-gated channels open

FYI - Prior to reaching threshold it is modality- or ligand-gated channels that open, not voltage-gated. Reaching threshold is what triggers the opening of the voltage-gated channels.

Question 14

In Figure 5.8 on p. 109, in part E it states that voltage-gated K+ channels remain open and that K+ continuing to leave the cell restores the resting membrane potential (RMP). This is an error. Explain what would happen to the membrane potential if the K+ channels were to remain open during hyperpolarization as the panel states and why this would not restore RMP. What is it that actually restores RMP?

Answer 14

If K+ channels remained open throughout the hyperpolarization phase, continued efflux of potassium would cause even greater hyperpolarization rather than allow for return to the RMP. It is the effect of the Na+-K+ pump and leak channels that brings the membrane potential back to resting.

Question 15

The thicker the myelin, the ___ (faster/slower) the nerve conduction velocity (NCV).

Answer 15

Faster

Question 16

GABA is a very important inhibitory neurotransmitter. GABA is the acronym for ___.

Answer 16

Gamma-aminobutyric acid

Question 17

In your own words, concisely explain the difference between a neuromessenger agonist and antagonist.

Answer 17

An agonist reproduces the action of the neuromessenger when it binds to the receptor, whereas an antagonist impedes the release of the neuromessenger or impairs the action of the neuromessenger by binding to and blocking its receptors.

Note: An antagonist does not block the reuptake pump. Blocking the reuptake pump enhances the effect of the neurotransmitter by allowing it to remain in the synaptic cleft longer. Antagonists always impede the action of the neurotransmitter in some way.