neuroscience NSC-2201 exam one review

An ion pump is... a) A protein that uses the flow of ions to make ATP, much like a hydroelectric dam uses water to make electricity. b) An ion channel that moves ions out of the cell instead of in. c) A phospholipid structure that moves ions along the inside of the cell membrane since ions are hydrophilic. d) An enzyme that uses ATP to move ions across the cell membrane.

d

How do catecholamines use end-product inhibition? a) Increased levels of calcium in the neuron inhibits the activity of tyrosine hydroxylase b) If too many catecholamines are up-taken into the axon terminal, the increase in Na+ concentration that accompanies their transport activates MAO to destroy catecholamines c) Increased levels of catecholamine in the extracellular matrix inhibit the uptake of tyrosine, limiting the production of catecholamines. d) Tyrosine hydroxylase is inhibited to continue converting tyrosine to L-dopa by the increased level of synthesized catecholamines in the neuron

d

If the magnitude of the depolarizing current is increased, which of the following will occur? a) Hyperpolarization amplitude will decrease b) Action potential amplitude will increase c) Action potential time will increase d) Action potential frequency will increase

d

The release of neurotransmitters into the synaptic cleft is caused by the opening of _____________ (Options 1-3) channels in the active zone of the axon terminal which leads to fusion of the synaptic vesicle by ________ (Options 4-6) to cause exocytosis. 1. Voltage-gated Na+ 2. Voltage-gated Ca++ 3. Mechanically-gated Ca++ 4. Membrane glutanoids (demagolgi) 5. Active Transporters 6. SNARE proteins

2, 6

What are the steps that lead to increased excitability in a neuron when NE is released presynaptically?

1) NE receptor bound to beta receptor activates G-protein in the membrane 2) G-protein activates adenylyl cyclase enzyme, which converts ATP into the second messenger cAMP 3) cAMP activates a protein kinase, which causes a K+ channel to close by attaching a phosphate to it. This produces little change in membrane potential but increases the membrane resistance and increases the length constant of dendrites. This enhances the response that a weak or a distant excitatory synapse produces. This effect can last longer than that of the presence of the transmitter.

List the criteria that are used to determine whether a chemical serves as a neurotransmitter. What are the various experimental strategies you could use to show that ACh fulfills the criteria of a neurotransmitter at the neuromuscular junction?

1) The molecule must be synthesized and stored in the presynaptic neuron2) The molecule must be released by the presynaptic axon terminal upon stimulation3) The molecule, when experimentally applied, must produce a response in the postsynaptic cell that mimics the response produced by the release of the neurotransmitter from the presynaptic neuron Immunohistochemistry shows where specific molecules are localized, in situ hybridization shows where specific mRNA transcripts for specific proteins are located

What are three physical characteristics that distinguish axons from dendrites?

1) the soma usually only gives rise to a single axon extending from the axon hillock, while it gives rise to many dendrites 2) axons are long and more uniform, while dendrites are much shorter 3) axon branches usually extend at right angles, dendrites are more sporadic

What two functions do proteins in the neuronal membrane perform to establish and maintain the resting membrane potential?

1. Provide channels that control the movement of specific ions across the neuronal membrane 2. Pump sodium and potassium ions across the membrane against their concentration gradient to maintain the resting membrane potential

Why is a excitatory synapse on the soma more effective in evoking an action potential in the postsynaptic neuron than an excitatory synapse on the tip of a dendrite?

A current entering through a synapse must spread through the spike-initiation zone, which must be depolarized beyond threshold. Depolarization decreases as a function of distance along a dendrite, so the effectiveness of a synapse at triggering an action potential depends on its distance from the spike-initiation zone. The soma is closer, so it is more effective there.

Colchicine is a drug that causes microtubules to break apart (depolymerize). What effect would this drug have on anterograde transport? What would happen in the axon terminal?

Anterograde transport would no longer be possible since microtubules are used by kinesin to transport vesicle containing molecules. This means the axon terminal would not receive any vesicles, and they would instead accumulate farther up the axon, closer to the cell soma.

The difference between neurons and muscles cells is that neurons have excitable membranes. True False

False

The existence of chemical synapses between neurons supports Golgi's Reticular Theory. True False

False

It is impossible to initiate an action potential during the relative refractory period. True False

False (It isn't impossible, Na+ channels are able to open during this time. They are NOT able to during the absolute refractory period. Due to hyperpolarization, they require more depolarization to reach threshold)

An axon cannot form a synapse on another neuron's axon because of the myelin sheath and the absence of ligand-gated channels. True False

False (Some neurons are able to form synapses between axons. These are called axoaxonic synapses)

Which parts of a neuron are shown by a Golgi stain that are not shown by a Nissl stain?

Golgi stains show the entire neuron, including the axon and dendrites. The Nissl stain only shows the cell soma.

Saltatory conduction describes the conduction of an action potential down an axon surrounded by myelin in which the sodium ions jump in and out of gaps in the myelin. (Really think about this one!) True False

False (Yes saltatory means to jump, but the Na+ ions are not physically jumping out of the axon and in at the next gap. Sodium ions are ALWAYS flowing in through the voltage-gated Na+ channels in the membrane. I instead like to think of each node as the speed up arrows in Mario Kart. The action potential is "running out of juice" due to leakage of ions (in other scientific words, the voltage is decreasing as it goes along the axon) until it hits these areas of high concentration of voltage-gated Na+ channels where it gives the action potential a huge boost that allows it to make it to the next node, and so on. The action potential never "jumps out" or leaves the axon like the name "saltatory conduction" suggests.)

Depolarization will always lead to an action potential True False

False (action potentials only fire if they reach threshold)

This chapter discussed a GABA-gated ion channel that is permeable to Cl-. GABA also activates a G-protein-coupled receptor, called the GABAb receptor, which causes potassium-selective channels to open. What effect would GABAb receptor activation have on the membrane potential?

GABA-gated Cl- ion channels would bring the membrane potential toward ECl (-65mV), and if Vm was less, activation would cause hyperpolarization. Activation of GABAb receptors would cause K-selective channels to open and bring the Vm toward Ek (-80mV), and if Vm was less, activation would cause hyperpolarization

When the membrane is at the potassium equilibrium potential, in which direction (in or out) is there a net movement of potassium ions?

If the membrane is at the potassium equilibrium potential, there would be no net movement across the membrane, since movement would indicate an imbalance in concentration across the membrane, thus the membrane potential would not be at the potassium equilibrium potential

There is a much greater K+ concentration inside the cell than outside. Why, then, is the resting membrane potential negative?

In addition to being filled with potassium, the membrane is also filled with negatively charged particles such as proteins that do not cross through channels the way ions do.

When the brain is deprived of oxygen, the mitochondria within neurons cease producing ATP. What effect would this have on the membrane potential? Why?

Ion channels and protein pumps cannot function without ATP, so there would be no movement of ions across the membrane against their concentration gradients. This would result in the membrane being unable to maintain a resting potential, and the brain would stop functioning.

A drug called strychnine, isolated from the seeds of a tree native to India and commonly used as rat poison, blocks the effects of glycine. Is strychnine an agonist or antagonist of the glycine receptor?

It's an antagonist. If it's blocking glycine's effects (rather than enhancing them), the drug is an antagonist. High doses of this drug eliminate glycine-mediated inhibition in the brain stem and spinal cord, which causes paralysis of the respiratory muscles, among other symptoms.

Define membrane potential (Vm) and sodium equilibrium potential (ENa). Which of these, if either, changes during the course of an action potential?

Membrane potential is the voltage across the membrane and sodium equilibrium potential, which is equal to 62 mV, is the electrical potential difference that exactly balances an ionic concentration gradient. The membrane potential changes during an action potential, but the equilibrium potential does not

What is myelin? What does it do? Which cells provide it in the central nervous system?

Myelin is an insulating membrane for axons provided by glia (oligodendroglia in the CNS and Schwann cells in the PNS). Myelin propels propagation of signals down the axon.

How does nerve gas cause respiratory paralysis?

Nerve gases interfere with synaptic transmission at the neuromuscular junction by inhibiting AChE. Uninterrupted exposure to high concentrations of ACh for several seconds leads to a process called desensitization. In this process, transmitter-gated channels close despite the continued presence of ACh. Normally, the rapid destruction of ACh by AChE prevents desensitization. However, if AChE is inhibited by nerve gas, ACh receptors will be desensitized and neuromuscular transmission will fail, causing respiratory paralysis.

What are three methods that could be used to show that a neurotransmitter receptor is synthesized or localized in a particular neuron?

Neuropharmacological analysis of i) synaptic transmission, ii) ligand-binding methods, and iii) molecular analysis of receptor proteins

You apply ACh and activate nicotinic receptors on a muscle cell. Which way will current flow through the receptor channels when a) Vm = -60 mV? b) Vm = 0 mV? c) Vm = 60 mv? why?

Nicotinic receptors are permeable to sodium and potassium, so a) inward, toward ENa (depolarization) b) this is the reverse potential (critical value of membrane potential at which current flow reverses), so no current flows c) outward, toward EK (hyperpolarization)

On which side of the neuronal membrane are Na+ ions more abundant?

Outside (Calcium is also more concentrated on the outside. Potassium is more concentrated on the inside)

Of the following structures, states which ones are unique to neurons and which are not: nucleus, mitochondria, rough ER, synaptic vesicle, Golgi apparatus

Synaptic vesicle

What ions carry the early inward and late outward currents during the action potential?

Sodium early inward, potassium late outward

Which equation would you use to calculate resting membrane potential? a) Huxley Equation b) Goldman Equation c) Nernst Equation d) Golgi Equation

b

Imagine we have labeled tetrodotoxin (TTX) so that it can be seen using a microscope. If we wash this TTX onto a neuron, what parts of the cell would you expect to be labeled? What would be the consequence of applying TTX to this neuron?

TTX clogs the voltage-gated sodium channels, so we would expect the axon to be labeled since that is where they are concentrated. This would prevent any action potentials from being fired

Some voltage-gated K+ channels are known as delayed rectifiers because of the timing of their opening during an action potential. What would happen if these channels took much longer than normal to open?

The action potential would be wider, meaning it would take longer for the membrane to return to resting potential

How does the action potential conduction velocity vary with axonal diameter? Why?

The larger in diameter the axon is, the greater the action potential's conduction velocity. If the axon is narrow and there are many open membrane pores, most of the current will flow out across the membrane. If the axon is wide and there are few open membrane pores, most of the current will flow down inside the axon.

State the neuron doctrine in a single sentence. To whom is this insight credited?

The neuron doctrine states that the cells of the nervous system are not continuous like is stated in Golgi's Reticular Theory, and instead communicate through contact. This is Cajal's theory.

What is meant by quantal release of neurotransmitter?

The total amount of transmitter released is a multiple of the number of transmitters in each vesicle. It reflects the number of transmitter molecules in one synaptic vesicle and the number of postsynaptic receptors available at the synapse

Why is the action potential referred to as "all-or-none"?

There are no partial action potentials. Depolarization either reaches threshold, thus triggering an action potential, or it does not., and no action potential is produced.

Classify the cortical pyramidal cell based on (1) number of neurites, (2) the presence or absence of dendritic spines, (3) connections, and (4) axon length

This is a multipolar cell with spiny dendrites. Their axons project to other cortical areas, and they are Golgi type I neurons because they have long axons.

You think you have discovered a new neurotransmitter, and you are studying its effect on a neuron. The reverse potential for the response caused by the new chemical is -60 mV. Is this substance excitatory or inhibitory? Why?

This neuron is inhibitory. A reverse potential of -60 mV suggests the neurotransmitter activates ion channels that make the membrane more negative, so movement towards this value is likely to be more negative than the action potential threshold. Thus, it is less likely to fire.

Differences in size, shape, and especially protein/channel makeup and density of a neuron change its electrical properties. True False

True

The synthesis of 5-HT is limited by our diet (including how much chocolate we eat!) True False

True

A neuron that experiences spatial summation where its dendrites meet the soma is more likely to fire an action potential than one that experiences an equal number of action potentials through temporal summation on the end of one dendrite. True False

True (The closer to the spike-initiation zone, the easier it is to maintain a depolarized voltage! In other words, the longer it has to travel to reach the axon hillock, the more leakage of ions it experiences and the less depolarized and able to reach threshold it may be. There is nothing to suggest that temporal summation is better than spatial, and may even be slightly less depolarizing depending on the time between the arrival of each action potential)

Adding positively charge potassium ions to the extracellular fluid surrounding a neuron will cause depolarization in the neuron. True False

True (The resting membrane potential is caused by more potassium existing in the cell than outside the cell. If you increase the amount of potassium outside the cell, less potassium would be driven out of the cell by diffusion and the internal voltage would be more positive.)

Knowledge of genes uniquely expressed in a particular category of neurons can be used to understand how those neurons function. Give one example of how you could use genetic information to study a category of neuron.

You can use green fluorescent protein (GFP). A foreign gene encoding a fluorescent protein can be introduced and placed under the control of a cell type, and when illuminated with the appropriate wavelength of light, the GFP fluoresces bright green, which allows the visualization of the neuron in which it is expressed.

At what point during the action potential do voltage-gated K+ channels open? a) About 1 millisecond after depolarization reaches threshold. b) It depends how high the depolarization is... c) Immediately when depolarization reaches threshold. d) After voltage-gated Na+ channels have closed, and pumps return the cell to resting membrane potential (~2msec).

a

How are released neurotransmitters cleared from the synaptic cleft? a) Enzymatic destruction and diffusion b) Endocytosis c) Exocytosis d) Both endocytosis and exocytosis

a

How does the lethal injection (KCl) work? a) The excess of potassium extracellularly abolishes the resting membrane potential in muscle cells, and therefore the heart stops beating. b) The excess of chloride in extracellular fluid makes the resting membrane potential in neurons drop so low that action potentials can no longer be fired. c) The brain shuts down from lack of oxygen because high potassium destroys the cerebral capillary beds. d) The toxicity of potassium shuts down the locus coeruleus in the brain stem, making it impossible to breathe.

a

If the resting potential of a cell were positive inside relative to extracellular fluid, and the membrane was permeable... a) Anions would tend to flow into the cell b) All ions would tend to flow out of the cell c) Anions would tend to flow out of the cell d) All ions would tend to flow into the cell

a

In a neuron at rest... a) The membrane is more permeable to potassium than sodium. b) The membrane is not permeable to sodium. c) Both A and B d) None of the above

a

One day while in class, Dr. Smith's Instacart delivery man turns rabid, breaks in, and bites her in the middle of lecture. Unable to speak and save herself, you call 911 and inform them that in order to save her we must stop the rabies virus from reaching the soma of her neurons, and therefore, we should block which type of axoplasmic transport? a) Retrograde transport using the motor protein dynein b) Retrograde transport using the motor protein kinesin c) Anterograde transport using the motor protein kinesin d) Anterograde transport using the motor protein dynein

a

Which is the correct order of synthesis for catecholamines? a)Dopamine → Norepinephrine → Epinephrine b) Dopamine → Epinephrine → Norepinephrine c) Epinephrine → Dopamine → Norepinephrine d) Epinephrine → Norepinephrine → Dopamine

a

Which of the following accounts for why a single action potential is able to cause a much stronger response at the neuromuscular junction than at most synapses in the CNS? a) There are more neurotransmitter receptors concentrated at the neuromuscular junction in junctional folds than on postsynaptic terminals in the CNS. b) There are multiple types of neurotransmitters released by motor neurons on the NMJ, whereas neurons in the CNS are specific to only 1 type of neurotransmitter. c) There are a larger number of transmitter molecules within the synaptic vesicles of motor neurons compared with CNS synapses. d) There is a larger synaptic cleft at the neuromuscular junction compared with CNS synapses.

a

Which of the following factors determine ion selectivity of specific ion channels? a) Nature of R groups lining the ion channel b) Different gating properties c) Whether it was translated on free or Rough ER ribosomes d) The resting membrane potential

a

Which of the following is the part of the neuron which provides innervation to other neurons? a) Axon terminal b) Soma c) Dendrite d) Axon hillock

a

Which of the following is true about Gray's type I synapses? a) The postsynaptic membrane differentiation is thicker than the presynaptic membrane differentiation b) They are usually inhibitory synapses c) They are known as symmetrical synapses d) Both A and B

a

Which of the following occurs when bitten by a Taiwanese cobra (alpha-bungarotoxin)? a) An active compound in the venom binds tightly to nicotinic ACh receptors and blocks the activation of respiratory muscles. b) An active compound in the venom that depolarizes the membrane around voltage-gated Ca++ receptors in the axon terminal leading to the release of neurotransmitters even in the absence of action potentials. c) An active compound in the venom inhibits the activities of AChE, thereby causing buildup of ACh and leading to desensitization of ACh receptors. d) An active compound in the venom destroys SNARE proteins that are necessary for the fusion of synaptic vesicles and therefore the exocytosis of neurotransmitters

a

Compare and contrast the properties of (a) AMPA and NMDA receptors and (b) GABAa and GABAb receptors

a) AMPA and NMDA are glutamate receptor subtypes; both are activated by glutamate, but the drug AMPA acts only on the AMPA receptor and the drug NMDA acts only on the NMDA receptor. NMDA is permeable to calcium, AMPA is not b) - both respond to GABA-Muscimol is agonist for GABAA receptor- agonist for GABAB is baclofen- antagonist for GABAA is bicuculline- antagonist for GABAB is phaclofen

Which of the following are responsible for inhibition in the CNS? a) GABA b) Glycine c) Glutamate d) AMPA

a, b

Which of the following are reasons for why the brain would choose G-protein coupled receptor transmission over transmitter-gated channels? a) Increased regulation of signaling b) Longer-lasting effects c) Faster response time d) Amplification of signal e) Ability to respond to any neurotransmitter with one protein

a, b, c

The "neuron doctrine"... (choose all that apply) a) was proposed by Cajal b) was discovered with a Nissl stain c) states that the neurites of neurons are continuous with one another d) rejected the reticular theory

a, d

In a hypothetical neuron, if the opening of 10 Na channels causes an action potential to fire, what happens to the one action potential if 100 Na channels are opened? (We are not talking about continuous current) a) The neuron becomes too depolarized, and starts to die due to Na+ toxicity inside the cell. b) The action potential is still fired, but does not look different on a graph. c) The action potential rises to a significantly higher voltage (increased amplitude) due to more depolarization. d) The action potential lasts for a significantly longer time.

b

Once the rising phase starts, how long does a typical action potential last? a) 2 seconds b) 2 milliseconds c) 2 microseconds d) 2 nanoseconds

b

What are co-transmitters? a) Secondary antibodies that attach to neurotransmitters and tag them with fluorescence when they are exocytosed from the axon terminal b) Transmitters that are released from the same nerve terminal c) Channels in the active terminal that can cause exocytosis and endocytosis of a transmitter d) Transmitters that are derived from the same precursor

b

What are second messengers? a) Peptide neurotransmitters b) Molecules that activate additional enzymes in the cytosol c) Special proteins that span a 3 nm gap between 2 cell membranes d) Ligand-gated ion channels that allow in more than one ion

b

What are transporters? What is their role? a) Enzymes that synthesize neurotransmitters from metabolic precursors; responsible for concentrating neurotransmitters in the synaptic cleft b) Special proteins embedded in the vesicle membrane; responsible for concentrating neurotransmitters inside the vesicle c) Special proteins embedded in the vesicle membrane; responsible for synthesizing neurotransmitters. d) Enzymes transported to the axon terminal that facilitate the fusion of synaptic vesicles containing neurotransmitters to the active zone of the axon terminal, leading to exocytosis.

b

What makes neurons different from liver cells (really really think about this)? a) The fact that they maintain a membrane potential b) Their proteins c) Their DNA d) All of the above

b

Which is true about the sodium-potassium pump? a) It pumps a Na(+) and K(+) out of the cell in exchange for bringing Ca(+2) into the cell b) It pumps 3 sodium out of the cell and brings 2 potassium into the cell c) It pumps 1 sodium out of the cell and brings 1 potassium into the cell d) There are 2 separate pumps, 1 for Na and 1 for K

b

Which of the following describes immunocytochemistry? a) A method used to assess the postsynaptic actions of a transmitter candidate b) The use of antibodies to visualize specific molecules within the brain cells c) The use of radioactivity to localize neurotransmitters and their synthesizing enzymes d) A method of localizing specific mRNA transcripts for proteins

b

Which of the following is true about nicotinic receptors? a) Nicotinic receptors do not exist in the CNS b) Nicotinic receptors are antagonized by curare c) Nicotinic receptors differ from muscarinic receptors in that they are found in cardiac muscle d) Nicotinic receptors bind only to nicotine

b

Which of the following maintain(s) the ionic gradient across the membrane? a) A sodium pump and diffusion through potassium and calcium channels b) The sodium-potassium pump, and a calcium pump c) The hydrophobic nature of the neuronal membrane d) Diffusion through potassium and sodium channels

b

Which of the following will propagate the fastest action potential? a) Small axon diameter, no myelination b) Large axon diameter, myelination c) Small axon diameter, myelination d) Large axon diameter, no myelination

b

Which organelle is responsible for regulating the intracellular concentrations of substances, such as calcium, in certain cells? a) Rough ER b) Smooth ER c) Lysosome d) Mitochondria

b

Why may it be lethal to drink alcohol while taking benzodiazepines and barbiturates? a) All three of these ligands bind to GABA-A receptors and block the binding of GABA, causing over-excitation of neurons leading to seizures, and the risk of death. b) All three of these ligands bind to GABA-A receptors and enhance the flow of Cl- caused by the binding of GABA. A stronger Cl- current makes it harder to fire any action potentials, and in high amounts can cause to death. c) Barbiturates and benzodiazepines hold the Cl- channel of GABA-A receptors open, which ethanol can flow through. If ethanol is able to enter the cell, it uses the hydrogen ions in the neuron to form water, and leaves the neuron so basic it dies, leading to death of the individual in large amounts. d) Ethanol can interact with benzodiazepines and barbiturates to form a structure which antagonizes glutamate receptors and prevents activation of neurons by glutamate, which shuts down about 80% of the neurons in the brain.

b

Imagine this scenario (really think! Drawing it out helps!): Neuron A synapses on interneuron B with GABA as it's main neurotransmitter. Interneuron B synapses on Neuron C, also with GABA as it's main neurotransmitter. What happens to Neuron C if you expose Neuron A to glutamate? (for the purposes of this example, all cells have gated-receptors for both GABA and glutamate, and GABA and glutamate act on their receptors as they do in most cases.) a) Neuron C is hyperpolarized and cannot fire an action potential b) Neuron C is disinhibited and can fire an action potential

b (GABA = inhibitory, glutamate = excitatory. so - neuron A is ACTIVATED by glutamate. This means neuron A releases GABA, so it INHIBITS neuron B. Neuron B is now inhibited, so it DOES NOT release GABA on neuron C. Neuron C is now disinhibited (no longer inhibited by GABA release from neuron B) and can therefore fire action potentials. In most cases in the CNS this will lead to neuron C being activated and releasing its neurotransmitters)

A neuron can fire at a maximum rate of _____ action potentials per second. a) 500 b) The limit does not exist c) 1,000 d) 10,000 e) 5,000

c

Diffusion is the movement of... a) Cations away from areas of positive charge, and anions away from negative charge. b) The movement of cations and anions in opposite directions c) The flow of an ion from an area of high concentration to an area of low concentration d) All of the above.

c

What is the main difference between hydrophilic and hydrophobic substance? a) Hydrophilic substances do not dissolve in water b) Hydrophilic substances are made of larger molecules than hydrophilic substances c) Hydrophobic substances do not dissolve in water d) Hydrophobic substances are colorless

c

What occurs when a protein kinase is activated? a) Phosphate groups are removed from proteins, which causes conformational change that may lead to activation or inactivation of said protein b) G-protein coupled receptors are activated c) Proteins are phosphorylated, which causes conformational change that may lead to activation or inactivation of said protein d) cAMP concentration is decreased

c

Where is the spike initiation zone in a typical neuron? a) The dendrites b) The soma c) The axon hillock d) The axon terminal

c

Which of the following cells would be likely to myelinate an axon in your leg? a) Microglia b) Astrocytes c) Schwann Cells d) Oligodendrocytes

c

Which of the following in necessary for diffusion? a) Ion pumps allowing ions to pass through the membrane b) None of the above; diffusion will happen on its own no matter what c) Channels that are open, making the membrane permeable d) No difference in voltage across the membrane

c

Which of the following is FALSE about cholinergic neurons? a) Acetylcholinesterase (AChE) is required for ACh degradation in the synaptic cleft b) The transfer of choline into the axon terminal requires the influx of Na+ c) Acetylcholine is manufactured in the soma and transferred to the axon terminal by kinesin d) Choline acetyltransferase (ChAT) adds an acetyl group taken from Acetyl CoA to choline to form acetylcholine

c

Which of the following is NOT true about the equilibrium potential of an ion? a) It is the voltage at which diffusional and electrical forces on the ion are equal yet opposite b) It depends on the extracellular and intracellular concentration of the ion c) The further from 0 the equilibrium potential, the more permeable a membrane will be to that ion. d) All of the above are true.

c

Which of the following is a difference between NMDA and AMPA receptors? a) NMDA receptors are glutamate-gated, while AMPA receptors are GABA-gated b) AMPA receptors are blocked by Mg+2 at regular resting membrane potential, and can only be activated after NMDA-mediated depolarization begins c) NMDA receptors are permeable to both Ca+2 and Na+, but AMPA receptors are only permeable to Na+ d) NMDA receptors are only permeable to Ca+2 while AMPA receptors are only permeable to NA+

c

Which of the following is responsible for the rising phase of the action potential? a) Outward K+ flux b) Inward K+ flux c) Inward Na+ flux d) Outward Na+ flux

c

_______ is/are attacked by the immune system in ____________ a) Microglia, Parkinson's disease b) Astrocytes, Epilepsy c) Myelin, Multiple Sclerosis d) Cerebellar Neurons, Alzheimer's Disease

c

What is caused by the binding of GABA to to a GABA-gated receptor? a) It opens a Cl- channel which drives the resting membrane potential lower b) It opens a Cl- channel which causes the eflux of Cl- from inside the neuron, depolarizing the membrane c) It opens a Cl- channel which hyperpolarizes the cell when Na+ influx tries to bring it to threshold d) It blocks K+ channels from opening, depolarizing the membrane potential

c (The equilibrium potential of Cl- is -65 mV, so it will try and bring the membrane potential to that always. This means that it will not affect the resting membrane potential which is also already at -65 mV. However, if the membrane potential is depolarized to a less negative number, the Cl- influx through the GABAR channel will drive the membrane potential lower, trying to bring it back to -65 mV)

If you build an artificial membrane with sodium and chloride channels and put 10 mM KCl outside the cell and 10 mM NaCl inside the cell, what would happen? a) Since NaCl is too big of a molecule to fit through Na and Cl channels, they would be unable to flow across the membrane, leaving the cell unable to reach equilibrium. b) Potassium would flow into the cell and sodium would flow out of the cell the be of equal concentration on either side. c) Nothing. Both Na and K are positively charged, so the membrane would be at rest. d) Sodium would flow out of the cell until a membrane potential develops that brings equilibrium

d

What describes spatial summation? a) EPSPs arriving at a postsynaptic neuron few msec apart from the same presynaptic neuron b) An EPSP arriving at a postsynaptic cell and depolarizing its neighboring membrane c) The inability of an EPSP to cause an action potential because of the summed negative charge on the membrane due to K+ permeability d) Many EPSPs arriving simultaneously from multiple axons at different areas on the postsynaptic cell

d

What is a Node of Ranvier? a) The scientific name for the hyperpolarization that can be seen on the graph of an action potential. b) The areas of axon where there is 100% insulation by myelin and no leakage of ions. c) The tool used in patch-clamp recordings that allow investigators to isolate a single ion channel. d) The area in an axon in which there is a gap in the myelin sheath and a high concentration of voltage-gated Na+ channels.

d

What is the role of dense-core vesicles? a) To respond to G-protein coupled receptor activation as a second messenger b) To store and release small neurotransmitters from the presynaptic axon terminal c) To phagocytize released neurotransmitters in the synaptic cleft after release d) To store larger, soluble proteins in the axon terminal to be released into the extracellular space.

d

Which of the following accounts for most of the fast synaptic transmission in the CNS? a) Gap junctions b) Cholinergic receptor channels c) G-protein coupled receptors d) Amino acid-gated channels

d

Which of the following causes voltage-gated ion channels like Na+ and K+ to become "open"? a) A globular protein cap is released from the pore in response to depolarization, allowing ions to flow through. b) The positive charge of the ion channel is negated by depolarization, allowing the ions to flow through without being repelled by like-charges. c) Increased polarity of the inner pore due to depolarization separates the ions from their water chaperone and allows them to flow more freely through the selectivity filter. d) Physical distortion of subunits of the channel in response to depolarization creates a free-flowing pore for that ion.

d

Which of the following explains why the resting membrane potential of a standard neuron is -65 mV? a) The resting membrane potential would be at 0 mV, but is driven negative by the flood of calcium ion leaving the cell. b) -65 mV is the point at which both potassium channels and sodium channels are closed and no ions can flow across the membrane. c) The equilibrium potential of chloride is also -65 mV, and since the membrane is so permeable to chloride, this drives the resting membrane potential. d) The neuron is significantly more permeable to potassium than sodium, so the resting membrane potential is driven much closer to K-eq (-80 mV) than Na-eq (+62 mV).

d

Which of the following is the definition of the resting membrane potential? a) The voltage of -65 mV that occurs in all cells at rest b) The driving force of positive ions into the cell c) The point at which the is 0 flow of ions across the membrane d) The difference in electrical potential across a cell membrane at rest

d

Which of the following is true of G-protein coupled receptors a) Alpha, Beta, and Gamma subunits must activate intermediate enzymes to lead to channel opening b) It contains 4 total subunits: alpha, beta, gamma, and the GTP binding subunit c) G-proteins are transmembrane receptor proteins d) When activated, the alpha subunit exchanges a GDP for a GTP and breaks from the other subunits, allowing both to activate effector proteins

d

Why does eating pufferfish cause numbness of the mouth, and if prepared badly, death? a) Pufferfish contain tetrodotoxin (TTX) which can enter the cell through voltage-gated Na+ channels. Once an action potential is fired, the TTX flows into the cell and binds to mitochondria. Due to its acidic nature, this can break down the membrane of the mitochondria. In small amounts this only prevents the mitochondria from making ATP until the TTX is phagocytized by the cell, but in large amounts it destroys the mitochondria. Without ATP the neuron is unable to use the sodium-potassium pump to return to resting membrane potential, and action potentials are unable to fire. b) Pufferfish contain tetrodotoxin (TTX) which attaches to voltage-gated Na+ channels and makes them unable to close. Because of this, the cell is unable to hyperpolarize and enter its refractory period or return to resting membrane potential. In small amounts, this prevents the firing of action potentials until the TTX is released from the channel, but in large amounts this prevents any action potentials from firing in the brain, causing the lungs and heart to stop working. c) Pufferfish contain tetrodotoxin which attached to voltage-gated Ca+2 channels and leads to an outflow of calcium into the extracellular matrix. Since calcium in large amount is toxic, this leads to death of surrounding neurons. If just affecting the sensory neurons near the mouth in small amounts, it causes numbness, but if in large amounts can cause extensive cell death in the brain. d) Pufferfish contain tetrodotoxin which attaches to voltage-gated Na+ channels and blocks the entrance of sodium into the cell. This makes it impossible to action potentials to be fired. In small amounts this causes no action potentials to be fired from sensory neurons surrounding the mouth, causing numbness, but in large amounts can lead to action potentials not firing in the brain to make the lungs and heart work.

d

Which of the following is true about the release of peptide neurotransmitters? a) They are released only with high frequency trains of action potentials b) They are released from synaptic vesicles, but not at the active zones c) They take longer to release than amino acid and amine neurotransmitters d) All of the above e) Two of the above

e

Why do action potentials travel in only 1 direction? a) They are the boy band's biggest fan and they want them to get back together! b) After an action potential is fired, the membranous proteins such as ion channels must be re-methylated before they are able to be opened again, which takes time. c) The membrane just behind the traveling action potential is in a refractory period due to hyperpolarization caused by closed and inactivated K+ channels. d) After an action potential fires from the axon hillock, the sodium is depleted in the extracellular space so there is not enough to fire one backwards. e) They were created by someone who was very heteronormative. f) The membrane just behind the traveling action potential is in a refractory period due to closed and inactivated voltage-gated Na+ channels.

f

What are the steps by which the information in the DNA of the nucleus directs the synthesis of a membrane-associated protein molecule?

mRNA is synthesized from DNA, which is then transported to either the rough ER or a free floating ribosome, where amino acids are constructed based off the mRNA. Several amino acids are joined together through peptide bonds to form peptides and eventually di- or polypeptides, which form proteins. (transcription and translation)