chapter 4-6

Which is TRUE about typical, resting neurons?

The permeability of the plasma membrane to potassium ions is much greater than its permeability to sodium ions.

Red blood cells have a higher proportion of aquaporins on the membrane than skin cells do. Assuming equal osmotic pressures, which is true?

The rate of osmosis is faster in red blood cells than in skin cells.

Using a micropipette, a neuroscientist injects an axon with enough Na+ ions to move the membrane potential +25mV (from resting). What happens next?

Voltage-gated Na+ will be triggered to open.

Osmosis" refers to the movement of what substance across semipermeable membranes?

WATER

Synthesis of neuropeptides differs from that of other neurotransmitters because it A. takes place in the axon terminals of neurons. B. takes place in the cell bodies of neurons. C. takes place on ribosomes in the postsynaptic cell's membrane. D. uses amino acids as precursor molecules. E. only takes place at synapses outside the central nervous system.

?? B

When you have a negative experience, your brain ties the emotion to the memory so that you avoid similar experiences in the future. If you were in a bike accident, and were afraid to get on a bike again, which brain structure functional group is active in guiding your fear? Diencephalon Cerebrum Limbic system Reticular formation Cerebellum

?? LIMBIC SYSTEM

Naloxone (Narcan) is an antagonist to the opioid receptor, the same receptor to which heroin is an agonist. If both heroin and naloxone were in the bloodstream, what would the user experience? A. A decrease in the effects of heroin B. An increase in the effects of heroin C. The same effects from heroin plus additional effects of naloxone D. A new set of effects unlike those of heroin alone

A decrease in the effects of heroin

Which is true of the resting membrane potential? A. It requires few ions to be distributed unevenly. B. It has the same value in all cells C. Only nerve and muscle cells have a potential difference across the membrane at rest. D. It is not altered by changing concentration gradients of permeating ions

A. It requires few ions to be distributed unevenly.

Which of the following statements is true? A. Phosphorylation by protein kinases can stimulate or inhibit the activity of effector proteins. B. Ca2+ is not a second messenger. C. Phosphodiesterase converts GMP into cGMP D. Conversion of ATP to cAMP is a phosphorylation reaction. E. Phospholipase C converts ATP to cAMP.

A. Phosphorylation by protein kinases can stimulate or inhibit the activity of effector proteins.

What is a role of calcium ions in the second-messenger cascade involving phospholipase C, diacylglycerol, and inositol trisphosphate?

Along with diacylglycerol, it activates protein kinase C.

Which is FALSE about the equilibrium potential of a given ion across a membrane?

An anion that is in higher concentration inside the cell than outside the cell will have a negative equilibrium potential.

You are examining the data from two time points taken in an experiment. At time 1 there was an extracellular concentration of Na+ of 115 mM outside the cell and 8mM inside the cell. An amino acid, lycine, is at 20mM outside and 40mM inside. At the second time measured Na+ is 100mM outside the cell and 23 mM inside the cell. Lycine is 15 mM outside the cell and 45mM inside. What is the best explanation?

Both Na+ and the amino acid bind on the side of the membrane where the Na+ concentration is higher, and both are transported to the side of the membrane where the Na+ concentration is lower.

At a very low temperature known as absolute zero, there is no random molecular motion. At absolute zero, would diffusion occur?

No, because diffusion depends upon the random motion of molecules.

A fat cell responds to the presence of the hormone epinephrine by increasing cytosolic cyclic AMP production, which leads to the catabolism of both glycogen and fat. What is the most likely explanation for this phenomenon?

Cyclic-AMP-dependent protein kinase activates two kinds of enzymes.

You are designing a drug. You'd like to deliver the drug by creating a skin patch that is impregnated with the drug and allowing the drug to diffuse through the layers of the skin to reach the underlying tissues and bloodstream. Which of these chemical changes might you make to increase the number of drug molecules that diffuse through the layers of the skin cells?

Decreasing the number of polar groups in the drug

If there was an increased concentration of K+ outside of the neuron, which would be TRUE? A. Neurons would spontaneously depolarize. B. Neurons would spontaneously hyperpolarize. C. The potassium equilibrium potential of nerve cells would become more negative. D. The sodium equilibrium potential would become less positive. E. During an action potential, the neuron would repolarize slowly or stay depolarized.

During an action potential, the neuron would repolarize slowly or stay depolarized.

During which of the following phases is K+ permeability greater than at rest?

During the after-hyperpolarization phase, to reach AP.

Amplification of a second messenger cascade can take place at which level of a signal cascade? A, One activated receptor can activate numerous G-proteins. B. One activated G-protein can activate numerous effector enzymes. C. One active effector enzyme can catalyze numerous reactions. D. One activated protein kinase can allosterically modulate numerous proteins. E. All of the choices are correct.

E.

Which of the following are ways in which binding of a chemical messenger with a cell's receptor can bring about a cellular response? A. Opening or closing of specific ionic channels in the plasma membrane B. Activation of an intracellular second-messenger system C. Promoting or inhibiting the transcription of genes that code for the synthesis of cellular proteins D. Activating or inhibiting intracellular enzymes E. All of the choices are correct.

E.

Although nerve cells in each cerebral hemisphere make connections with other cells in the same hemisphere, there is no crossover of information between the two hemispheres.

FALSE

Because all parts of a neuronal cell body have the same threshold, no one synapse on the cell is more important than any other.

FALSE

Competition for receptors is strictly a pharmacological phenomenon, since naturally occurring chemical messengers do not compete with each other for the same receptor site.

FALSE

Phosphorylation is a necessary component of any enzyme activation.

FALSE

TRUE OR FALSE Although permeability to mineral ions does not vary much from one cell to another, different cells vary considerably in their permeability to nonpolar molecules.

FALSE

TRUE OR FALSE If a cell were placed in a solution of 0.15 M NaCl, it would shrink.

FALSE

TRUE OR FALSE Pinocytosis is a method by which molecules can leave cells whose membranes are impermeable to the molecules.

FALSE

TRUE OR FALSE The component of the plasma membrane that acts as a selective barrier to diffusion of polar molecules is the integral proteins.

FALSE

The enzyme that catalyzes the production of cAMP from ATP is phosphodiesteras

FALSE

What will happen if a normal cell is placed in a hypotonic solution?

IT WILL SWELL IN SIZE

Which of the following is TRUE about the concentration gradient of Na+ in a neuron at rest?

It favors its movement into the cell at the resting membrane potential.

Which best describes the reticular formation of the brain? A. It is mainly involved in motor coordination and balance. B. It is the master endocrine gland of the brain. C. It is primarily responsible for visual perception. D. It integrates information from all regions of the CNS, and incorporates the mechanisms that regulate sleep and wakefulness. E. It is the primary synaptic relay station for sensory information entering the CNS.

It integrates information from all regions of the CNS, and incorporates the mechanisms that regulate sleep and wakefulness.

Which is true about mediated transport of substances across cell membranes?

It involves a specific membrane protein that functions as a carrier molecule.

Which is TRUE about the axon hillock of an axon? A. Its membrane potential at threshold is more positive than that of the cell body and dendrites. B. Its membrane potential at threshold is more negative than that of the cell body and dendrites. C. Synapses far from the axon hillock are more effective in influencing whether an action potential will be generated in the axon than are synapses close to the axon hillock. D. It is the region where neurotransmitter vesicles are docked and ready to be released by exocytosis. E. It can only conduct graded potentials because it lacks voltage-gated Na+ channels.

Its membrane potential at threshold is more positive than that of the cell body and dendrites.

Which of the following is NOT known to be an important neurotransmitter in the CNS? Dopamine Acetylcholine Morphine Glutamate Substance P

Morphine

Postganglionic neuron cell bodies of the autonomic nervous system have which category of neurotransmitter receptor?

Nicotinic acetylcholine receptors

If the ATP-generating mechanisms in a cell are poisoned and the cell depletes its ATP reserves, which would occur first?

Primary active transport of molecules would cease.

Equal amounts of two solutes, A and B, are placed into the same beaker of water at the same time. Solute A reaches diffusion equilibrium faster than solute B. What is the most likely explanation for this observation?

Solute A is smaller than solute

Activated calmodulin functions to activate or inactivate cytosolic enzymes.

TRUE

Cyclic AMP activates allosteric proteins.

TRUE

Designing a drug that blocked the release of eicosanoids would be an effective therapy for both pain and inflammation.

TRUE

TRUE OR FALSE Adding one mole of NaCl to one liter of water will lower the water concentration twice as much as adding one mole of glucose.

TRUE

TRUE OR FALSE All other factors being equal, the rate of diffusion across a permeable surface will be greater for small molecules than for larger ones.

TRUE

TRUE OR FALSE Because of the active transport of Na+ and K+, the intracellular concentration of Na+ is lower than the extracellular concentration, whereas the reverse is true for K+.

TRUE

The lipid portion of a cell's plasma membrane constitutes a barrier to current. TRUE OR FALSE

TRUE

The maintenance of a resting potential in a neuron depends indirectly upon the functioning of the Na+, K+-ATPase pumps in the membrane.

TRUE

Two stimuli occur on the same neuron more than a minute apart. The second stimulus is more than ten times greater than the first. If we compare the two resulting action potentials, which is TRUE? A. The second stimulus will lead to an action potential with higher amplitude. The second stimulus will lead to an action potential with a longer duration. B. The second stimulus will lead to an action potential with a longer hyperpolarization at the end. C. The amplitude of the two action potentials will be the same. D. The amplitude and duration of the second action potential will be greater than the first.

The amplitude of the two action potentials will be the same.

In which situation would an injected drug be the most effective agonist for an endogenous chemical messenger?

The drug achieves 50% saturation of the messenger's receptors at a lower concentration than that required by the messenger.

Which is true about neuronal membrane electrical and concentration gradients at the peak of the action potential?

The electrical gradient is in a direction that would tend to move K+ out of the cell.

At very low concentrations, epinephrine causes an artery to dilate. At higher concentrations epinephrine causes the same artery to constrict. How can these different effects be explained?

There are two types of epinephrine receptors with different affinities for epinephrine that use two different second-messenger systems.

Which of the following is NOT typically true about G proteins?

They act as second messengers.

Which of the following is NOT true of glial cells? A. They form the myelin for axons. B. They are outnumbered 10 to 1 by neurons in the nervous system. C. They deliver fuel molecules to neurons and remove the waste products of metabolism. D. They are important for the growth and development of the nervous system. E. They regulate the composition of the extracellular fluid in the CNS.

They are outnumbered 10 to 1 by neurons in the nervous system.

Visual signals travel on myelinated axons. While most pain signals travel on unmyelinated axons. If you get a paper cut, will you see the cut happen or feel the pain first?

You will experience the visual sensation before the pain sensation.

Nicotine is a cholinergic antagonist. a beta-adrenergic agonist. a cholinergic agonist. an alpha-adrenergic antagonist. a neurotransmitter.

a cholinergic agonist.

Amplification during a second-messenger cascade is beneficial because amplification:

allows small amounts of hormones to produce large responses in target cells

excessive alcohol intake can cause difficulty maintaining posture and coordinating body movements. This is likely due to alcohol's stimulatory affect on GABA releasing neurons in the

cerebellum

Epinephrine activates the cyclic AMP pathway in liver cells. In this example, epinephrine is a ___________ and cAMP is a _____ ________.

first messenger, second messenger

What second messenger most directly causes calcium ions to be released from intracellular stores?

inositol

Insulin is a protein hormone with mostly hydrophilic amino acids. Which is the most likely description of its receptor?

integral membrane protein

Molecule X is some sort of chemical messenger. Its receptor resides within the nucleus and once the receptor is bound to X, gene transcription occurs. Molecule X might be a(n)

lipid/steroid

Alzheimer's disease is thought to involve primarily

loss of cholinergic neurons.

Substance A, a penetrating solute, crosses the membrane at a rate of 10 molecules per second. When a patient has a fever and body temperature is elevated, we would expect the cell to have a rate of

more than 10 molecules per second

The regions of myelinated axon membrane that have the highest permeability to ions are the

nodes of Ranvier.

What is the most common transport mechanism by which glucose and other organic solutes cross the luminal membrane of an epithelial cell layer?

secondary active cotransport with Na+

CO2 is a small, non-polar molecule. It will cross the cell membrane by

simple diffusion

Some glucose transport proteins can also bind fructose, another six-carbon monosaccharide, but not lycine, an amino acid, because transport proteins exhibit ___________ for their ligands

specificity

Synthesis of neuropeptides differs from that of other neurotransmitters because it

takes place in the cell bodies of neurons