Bio 2 Exam 3 C

B. the primary nitrogenous waste product of humans

Urea is \________:
A. insoluble in water
B. the primary nitrogenous waste product of humans
C. the primary nitrogenous waste product of most birds
D. the primary nitrogenous waste product of most aquatic invertebrates

A. is soluble in water

Ammonia \________.
A. is soluble in water
B. has low toxicity relative to urea
C. is metabolically more expensive to synthesize than urea
D. is the major nitrogenous waste excreted by insects

B. Selective reabsorption

Materials are returned to the blood from the filtrate by which of the following processes?
A. Filtration
B. Selective reabsorption
C. Secretion
D. Excretion

A. active transport carriers

The reabsorption of glucose, amino acids, and many other molecules needed by the body is driven by \______________.
A. active transport carriers
B. diffusion
C. facilitated diffusion
D. homeostasis

C. Malpighian tubules

The osmoregulatory/excretory system of most insects is based on the operation of \_____.
A. Protonephridia
B. Metanephridia
C. Malpighian tubules
D. nephrons

E. insects—ammonia

Select the incorrectly matched organism and its nitrogenous waste product.
A. most fish—ammonia
B. mammals—urea
C. reptiles—uric acid
D. birds—uric acid
E. insects—ammonia

B. Small, stagnant pools do not provide enough water to dilute the toxic ammonia.

African lungfish, which are often found in small, stagnant pools of fresh water, produce urea as a nitrogenous waste. What is the advantage of this adaptation?
A. Urea takes less energy to synthesize than ammonia.
B. Small, stagnant pools do not provide enough water to dilute the toxic ammonia.
C. The highly toxic urea makes the pool uninhabitable to potential competitors.
D. Urea makes lungfish tissue hypo-osmotic to the pool.

B. Movement of potassium into the lumen of the Malpighian tubules is an energy-requiring process.

Through studies of insect Malpighian tubules, researchers found that K+accumulated on the inner face of the tubule, against its concentration gradient. What can you infer about the mechanism of transport?
A. Potassium transport is a passive process.
B. Movement of potassium into the lumen of the Malpighian tubules is an energy-requiring process.
C. Potassium moves out of the tubules at a faster rate than it moves into the lumen of the tubules.
D. Sodium ions will follow potassium ions.

C. There would be a net movement of water into the lumen of the tubules.

A potassium ion gradient is set up in insect Malpighian tubules through an active transport process. As a result, potassium concentration is higher in the lumen of the tubules than in hemolymph. How would the potassium gradient affect water movement?
A. Water would be forced out of the lumen of the Malpighian tubules through an osmotic gradient.
B. The potassium gradient would have no effect on water movement.
C. There would be a net movement of water into the lumen of the tubules.
D. Water would be conserved, forming a hypertonic solution in the Malpighian tubules.

A. amphibians—isotonic

Select the incorrectly matched vertebrate and its urine concentration relative to its blood.
A. amphibians—isotonic
B. marine reptiles—isotonic
C. desert mammals—strongly hypertonic
D. marine mammals—strongly hypertonic
E. terrestrial birds—weakly hypertonic

C. a marine bony fish

Which of the following animals generally has the lowest volume of urine production?
A. a vampire bat
B. a salmon in fresh water
C. a marine bony fish
D. a shark inhabiting the Mississippi River

A. 0.0 mM sucrose

Single-celled Paramecium live in pond water (a hypotonic environment). They have a structural feature, a contractile vacuole, which enables them to osmoregulate. If you observed them in the following solutions, at which sucrose concentration (in millimolars, mM) would you expect the contractile vacuole to be most active?
A. 0.0 mM sucrose
B. 0.05 mM saline
C. 0.08 mM sucrose
D. 1.0 mM saline

B. False

Beverages such as coffee, tea, and soda are diuretic and lead to a net loss of water.
A. True
B. False

B. Tap water

From a health standpoint, which of the following is probably the healthiest to drink?
A. Bottled water
B. Tap water
C. Sports drinks
D. Energy drinks
E. Vitamin water

B. Uric acid

Terrestrial organisms must conserve water. The least amount of water is lost with the excretion of which nitrogenous waste product?
A. Carbon dioxide
B. Uric acid
C. Ammonia
D. Urea

B. kangaroo rats

Among the following choices, the most concentrated urine is excreted by \_____.
A. frogs
B. kangaroo rats
C. humans
D. freshwater fish

C. hypertonic osmoregulators

Which of the following best describes freshwater fish?
A. hypotonic osmoregulators
B. hypotonic osmoconformers
C. hypertonic osmoregulators
D. hypertonic osmoconformers
E. isotonic osmoconformers

A. excrete copious dilute urine and retain salts

Organisms living in a freshwater environment normally
A. excrete copious dilute urine and retain salts
B. excrete a small volume of dilute urine and retain salts
C. excrete copious concentrated urine
D. conserve both water and salts

C. Drinking salt water and excreting salts

Saltwater fish achieve water balance by
A. Excreting water
B. Retaining salts
C. Drinking salt water and excreting salts
D. Excreting salts with a nasal salt gland

E. All of the above

Which of the following operates by passing fluids into a tube, and then secreting or reabsorbing specific substances?
A. Flame cells of flatworms
B. Metanephridia of annelid worms
C. Malpighian tubules of insects
D. Vertebrate nephrons
E. All of the above

C. I, II, III, and IV

The mammalian kidney contains structures that can perform various functions. These functions include:
I-excretion.
II-reabsorption.
III-secretion.
IV-filtration.

A. I and II

B. I, II, and III

C. I, II, III, and IV

D. II and III

E. II, III, and IV

D. Loop of Henle

Which structure is found in the renal medulla?
A. Bowman's capsule
B. Convoluted tubule
C. Glomerulus
D. Loop of Henle
E. Both A and D

B. Bowman's capsule → proximal convoluted tubule → loop of Henle → distal convoluted tubule → collecting duct

Which of the following choices is the correct path for the filtrate to follow through the nephron in the production of urine?
A. Bowman's capsule → distal convoluted tubule → loop of Henle → proximal convoluted tubule → collecting duct

B. Bowman's capsule → proximal convoluted tubule → loop of Henle → distal convoluted tubule → collecting duct

C. Bowman's capsule → loop of Henle → proximal convoluted tubule → distal convoluted tubule → collecting duct

D. Bowman's capsule → collecting duct → proximal convoluted tubule → loop of Henle → distal convoluted tubule

E. collecting duct → proximal convoluted tubule → loop of Henle → distal convoluted tubule→ Bowman's capsule

C. arid

Animals that have very long juxtamedullary nephrons likely live in \______ environments.
A. marine
B. freshwater
C. arid
D. tropical forest

D. is mainly a consequence of blood pressure in the capillaries of the glomerulus

The transfer of fluid from the glomerulus to Bowman's capsule \_____.
A. results from active transport
B. transfers large molecules as easily as small ones
C. is very selective as to which subprotein-sized molecules are transferred
D. is mainly a consequence of blood pressure in the capillaries of the glomerulus

C. have plasma membranes of low permeability to water

In humans, the transport epithelial cells in the ascending loop of Henle \_____.
A. are the largest epithelial cells in the body
B. are not in contact with interstitial fluid
C. have plasma membranes of low permeability to water
D. are not affected by high levels of nitrogenous wastes

D. diffusion of salt from the descending limb of the loop of Henle

The high osmolarity of the renal medulla is maintained by all of the following except\________.
A. active transport of salt from the upper region of the ascending limb
B. the spatial arrangement of juxtamedullary nephrons
C. diffusion of urea from the collecting duct
D. diffusion of salt from the descending limb of the loop of Henle

B. immunity

The kidneys are important homeostatic organs, contributing to the stability of all of the following except:
A. blood volume
B. immunity
C. blood pressure
D. electrolytic concentration
E. pH

C. Copious dilute urine

A person with diabetes insipidus fails to respond to ADH. Which of the following is a symptom of this condition?
A. Glucose in urine
B. Copious hyperosmotic urine
C. Copious dilute urine
D. Small volume of concentrated urine
E. Failure to urinate

B. increase, and the urine would be isoosmotic compared to plasma

If ATP production in a human kidney was suddenly halted, urine production would \_____.
A. decrease, and the urine would be hypoosmotic compared to plasma
B. increase, and the urine would be isoosmotic compared to plasma
C. increase, and the urine would be hyperosmotic compared to plasma
D. decrease, and the urine would be isoosmotic compared to plasma

B. Arterial blood pressure

Which process drives the process of filtration from the capillaries into the glomerulus?
A. Active transport
B. Arterial blood pressure
C. Venous blood pressure
D. Osmotic pressure

B. Reabsorption of water

An important function of the proximal convoluted tubule is \_____.
A. Filtration of NaCl
B. Reabsorption of water
C. Countercurrent heat exchange
D. Secretion of water

D. Proximal convoluted tubule

Valuable molecules like glucose, amino acids, and vitamins are mostly reabsorbed into the blood at which location in the nephron?
A. Collecting duct
B. Glomerulus
C. Loop of Henle
D. Proximal convoluted tubule

A. Countercurrent exchange between ascending and descending loops of Henle

An osmotic gradient in the kidney medulla is established by
A. Countercurrent exchange between ascending and descending loops of Henle
B. Countercurrent exchange between the loop of Henle and collecting ducts
C. Filtration of large proteins in the glomerulus
D. Movement of water out of the collecting duct

A. Signals aquaporins to be added to cell membrane

In response to dehydration, ADH
A. Signals aquaporins to be added to cell membrane
B. Signals aquaporins to be added to vesicles
C. Stimulates production of angiotensin II
D. Stimulates thirst response

B. urea is less toxic than ammonia

The advantage of excreting nitrogenous wastes as urea rather than as ammonia is that \_____.
A. urea can be exchanged for Na+
B. urea is less toxic than ammonia
C. urea does not affect the osmolargradient
D. less nitrogen is removed from the body

D. Collection duct

In the vertebrate nephron antidiuretic hormone (ADH) acts primarily in the
A. Loop of Henle
B. Proximal convoluted tubule
C. Glomerulus
D. Collection duct

A. is activated immediately upon infection

Innate immunity \_____.
A. is activated immediately upon infection
B. depends on an infected animal's previous exposure to the same pathogen
C. is based on recognition of antigens that are specific to different pathogens
D. is found only in vertebrate animals

A. It enables a rapid defense against an antigen that has been previously encountered.

What major advantage is conveyed by having a system of adaptive immunity?
A. It enables a rapid defense against an antigen that has been previously encountered.
B. It enables an animal to counter most pathogens almost instantly the first time they are encountered.
C. It results in effector cells with specificity for a large number of antigens.
D. It allows for the destruction of antibodies.

B. antibody synthesis

Which of the following is uniqueto the adaptive immune defense system?
A. cells that ingest invading microbes
B. antibody synthesis
C. inflammation
D. fever

D. They release chemicals that dilate blood vessels near the wound site, allowing blood components to enter the region from the bloodstream.

Which of the following statements best describes the role of mast cells in the inflammatory response?
A. They secrete substances that degrade bacterial cell walls and engulf and digest the invaders.
B. They release chemicals that constrict blood vessels at some distance from the wound site.
C. They release cytokines to stimulate the release of additional neutrophils and macrophages.
D. They release chemicals that dilate blood vessels near the wound site, allowing blood components to enter the region from the bloodstream.

D. They are directly involved in antibody production.

Which of the following is false about neutrophils?
A. They are part of the non-adaptive immune response.
B. They are produced by bone marrow stem cells.
C. The are phagocytic and engulf foreign particles
D. They are directly involved in antibody production.

A. a thymus

Immunologists can breed mice that lack \_______ in order to compare the immune response of normal mice to those that have no T cells.
A. a thymus
B. a spleen
C. bone marrow
D. kidneys
E. a liver

A. inflammatory response

A boy falls while riding his bike. A scrape on his hand almost immediately begins to bleed and becomes red, warm, and swollen. What response is occurring?
A. inflammatory response
B. lytic response
C. adaptive immune response
D. autoimmune response

D. the ancient observation that someone who had recovered from the plague could safely care for those newly diseased

Immunological memory accounts for \_____.
A. the human body's ability to distinguish self from non-self
B. the observation that some strains of the pathogen that causes dengue fever cause more severe disease than others
C. the ability of a helper T cell to signal B cells via cytokines
D. the ancient observation that someone who had recovered from the plague could safely care for those newly diseased

B. You had an adaptive immunity to that virus

You and a friend were in line for a movie when you noticed the woman in front of you sneezing and coughing. Both of you were equally exposed to the woman's virus, but over the next few days, only your friend acquired flu-like symptoms and was ill for almost a week before recovering. Which one of the following is a logical explanation for this?
A. Your friend had antibodies to that virus.
B. You had an adaptive immunity to that virus.
C. Your friend had an autoimmune disorder.
D. Your friend had allergies.

C. memory cell

A certain cell type has existed in the blood and tissue of its vertebrate host's immune system for over twenty years. One day, it recognizes a newly arrived antigen and binds to it, subsequently triggering a secondary immune response in the body. Which of the following cell types most accurately describes this cell?
A. plasma cell
B. thyroid cell
C. memory cell
D. macrophage

A. is a filtrate of the blood, as is urine.

The lymphatic fluid
A. is a filtrate of the blood, as is urine.
B. is completely separate from the circulatory system for blood.
C. carries both red and white blood cells.
D. functions in adaptive immunity but not in innate immunity.
E. carries a toxic gas that kills cancerous cells.

D. that part of an antigen that actually binds to an antigen receptor.

An epitope is
A. part of the interferons that penetrate foreign cells.
B. a protein protruding from the surface of B cells.
C. two structurally similar antibodies dissolved in the blood plasma.
D. that part of an antigen that actually binds to an antigen receptor.
E. a mirror image of an antigen.

D. mark pathogenic cells for destruction.

The function of antibodies is to
A. inject toxins into living pathogens.
B. secrete cytokines that attract macrophages to infection sites.
C. release perforins to disrupt infected cells.
D. mark pathogenic cells for destruction.

A. distinguish self from non-self.

The MHC is important in a T-cell's ability to
A. distinguish self from non-self.
B. recognize specific parasitic pathogens.
C. identify specific bacterial pathogens.
D. identify specific viruses.
E. recognize differences among types of cancer.

B. proliferate

When a T cell is activated by an antigen, it will most likely
A. secrete antibodies
B. proliferate
C. die
D. become a hybridoma
E. become a plasma cell

B. B-cells

Which of the following releases histamines?
A. Mast cells
B. B-cells
C. T-cells
D. Plasma cells

C. Antibodies and interferons are produced against the antigens.

Which of the following is notpart of the inflammatory response?
A. Histamine and other chemicals are released, which produce redness, warmth, and swelling.
B. Neutrophils and macrophages attack the invading microbes and contribute to the pus.
C. Antibodies and interferons are produced against the antigens.
D. Invading agent causes the release of cytokines, which produce a fever.

A. Complement protein

Which of the following components of the immune system destroys bacteria by punching holes in the wall of the bacteria?
A. Complement protein
B. Macrophages
C. Plasma cells
D. Major histocompatibility complex (MHC) proteins

C. antibodies

In the humoral response, B cells produce plasma cells, which in turn produce large quantities of \______ that are specific for foreign antigens.
A. agglutinations
B. interferons
C. antibodies
D. macrophages

C. Cytokines

\_________ are molecules released by activated helper T cells.
A. Antigens
B. Immunoglobulins
C. Cytokines
D. Antibodies

A. the antibody having at least two binding regions

When antibodies bind antigens, the clumping of antigens results from \_____.
A. the antibody having at least two binding regions
B. disulfide bridges between the antigens
C. bonds between class I and class II MHC molecules
D. denaturation of the antibodies

A. Memory

If a patient is missing B and T cells, what would be absent from the immune response?
A. Memory
B. Lysozymes
C. Cytokines
D. Defense against bacteria

B. only I, II, and IV

Which of the following would help a virus avoid triggering an effective adaptive immune response?
I) having frequent mutations in genes for surface proteins
II) building the viral shell from host proteins
III) producing proteins very similar to those of other viruses
IV) infecting and killing helper T cells

A. only I and III

B. only I, II, and IV

C. only I, II, and III

D. only II, III, and IV

D. III → IV → II → I → V

Arrange in the correct sequence these components of the mammalian immune system as it first responds to a pathogen.
I) Pathogen is destroyed.
II) Lymphocytes secrete antibodies.
III) Antigenic determinants from pathogen bind to antigen receptors on lymphocytes.
IV) Lymphocytes specific to antigenic determinants from pathogen become numerous.
V) Only memory cells remain.

A. I → III → II → IV → V

B. II → I → IV → III → V

C. IV → II → III → I → V

D. III → IV → II → I → V

B. injection of antibodies to the toxin

An individual who has been bitten by a poisonous snake that has a fast-acting toxin would likely benefit from \_____.
A. vaccination with a weakened form of the toxin
B. injection of antibodies to the toxin
C. injection of interleukin-1
D. injection of interferon

C. Antihistamines

A patient complaining of watery, itchy eyes and sneezing after being given a flower bouquet as a birthday gift should first be treated with \_____.
A. a vaccine
B. sterile pollen
C. Antihistamines
D. monoclonal antibodies

B. cytotoxic and helper cells

T cells of the immune system include \_____.
A. CD4, CD8, and plasma cells
B. cytotoxic and helper cells
C. plasma, antigen-presenting, and memory cells
D. lymphocytes, macrophages, and dendritic cells

D. helper T cells

The immune response is mostly coordinated by
A. coordinator T cells
B. cytotoxic T cells
C. inducer T cells
D. helper T cells

A. One has a major role in antibody production, while the other has a major role in cytotoxicity.

Which of the following is a difference between B cells and T cells?
A. One has a major role in antibody production, while the other has a major role in cytotoxicity.
B. One binds a receptor called BCR (B-cell receptor), while the other recognizes a receptor called TCR (T-cell receptor).
C. B cells are activated by free-floating antigens in the blood or lymph. T cells are activated by membrane-bound antigens.
D. T cells are produced in the thymus and B cells are produced in the bone marrow.

A. Phagocytosis

Which of the following do Helper T-cells not directly carry out?
A. Phagocytosis
B. Activate B-cells
C. Activate cytotoxic T-cells
D. Produce cytokines

D. I and II

When an antigen first challenges the immune system, if the primary immune response produces B cells, what are the fates of those B cells?
I. Some of the B cells become plasma cells that secrete antibodies
II. Some of the B cells become memory cells and can produce a swifter response if the body encounters that particular antigen again
III. Some of the B cells secrete chemicals called pyrogens that travel to the brain inducing a fever

A. just II

B. just I

C. II and III

D. I and II

E. I, II, and III

B. Rapid response

Which of the following is not a key trait of the adaptive immunity response?
A. Ability to respond specifically to a wide diversity of foreign molecules and organisms
B. Rapid response
C. Generally long-lasting immunological memory
D. The ability to recognize "self" from "nonself"

D. sodium ions out of the cell and potassium ions into the cell.

The operation of the sodium-potassium "pump" moves
A. sodium and potassium ions into the cell.
B. sodium and potassium ions out of the cell.
C. sodium ions into the cell and potassium ions out of the cell.
D. sodium ions out of the cell and potassium ions into the cell.

C.dendrites.

The multiple cytoplasmic extensions of a neuron are called
A.axons.
B.cell bodies.
C.dendrites.
D.synapses.

C. interneurons.

Most of the neurons in the human brain are
A. sensory neurons.
B. motor neurons.
C. interneurons.
D. peripheral neurons.

B. are always open

Ion (leak) channels differ from gated channels in that the former
A. use carrier proteins
B. are always open
C. only allow anions to pass through the membrane
D. require ATP

B. False

Ions are able to move across the cell membrane when no channels are present
A. True
B. False

B. The outside is 70 millivolts more positive than the inside

Which of the following describes the resting potential of the neuronal cell membrane?
A. The inside is 70 millivolts more positive than the outside
B. The outside is 70 millivolts more positive than the inside
C. The inside is 30 millivolts more positive than the outside
D. The outside is 30 millivolts more positive than the inside

C. potassium channels in the membrane

The resting potential of a neuron is produced primarily by
A. voltage-gated channels in the membrane
B. chemically gated channels in the membrane permanently open
C. potassium channels in the membrane
D. the concentration difference in Na+ across the membrane
E. blockage of the sodium-potassium pump

B. The membrane potential would increase.

If you experimentally increase the concentration of Na+ outside a cell while maintaining other ion concentrations as they were, what wouldhappen to the cell's membrane potential?
A. The membrane potential would decrease.
B. The membrane potential would increase.
C. The membrane potential would be unaffected.
D. The answer depends on the thermodynamic potential.

B. hyperpolarization of the neuron

For a neuron with an initial membrane potential at -70 mV, an increase in the movement of potassium ions out of that neuron's cytoplasm would result in the \_____.
A. depolarization of the neuron
B. hyperpolarization of the neuron
C. replacement of potassium ions with sodium ions
D. replacement of potassium ions with calcium ions

C. because the Na+ concentration is much higher outside the cell than it is inside, and the Na+ ions are attracted to the negatively charged interior

Why do Na+ ions enter the cell when voltage-gated Na+ channels are opened in neurons?
A. because the Na+ concentration is much lower outside the cell than it is inside
B. because the Na+ ions are actively transported by the sodium-potassium pump into the cell
C. because the Na+ concentration is much higher outside the cell than it is inside, and the Na+ ions are attracted to the negatively charged interior
D. because the Na+ concentration is much higher outside the cell than it is inside, and the Na+ions are actively transported by the sodium-potassium pump into the cell

C. The resting potential would approach zero.

Suppose there was a mutation in the gene encoding the voltage-gated sodium channel in neurons, that disrupted the gate and allows Na+ and K+ to move across the membrane in both directions at all times. What would be the effect on the resting potential?
A. The resting potential will be increased to more negative inside since more Na+would move across the membrane.
B. There would be no effect since the Na+ /K+pump would still be operating.
C. The resting potential would approach zero.
D. The resting potential would switch to being more negative outside than inside.

D. Sodium in, potassium out

A Hawaiian legend tells of a village that angered a shark god. In revenge, a "seaweed" began to grow in the tidepools that killed anyone who touched it. In fact, this "Limu Make O Hana"("Seaweed of Death from Hana") is a zoanthid cnidarian, or soft coral which contains a palytoxin that locks the sodium-potassium pump open, allowing free flow of ions. Palytoxin is incredibly toxic and there have been incidents of poisoning from zoanthids within marine aquaria tanks in people's homes. If a villager suffers palytoxin poisoning, which way will the ions in his neurons flow?

A. All ions will flow out

B. Potassium in, sodium out

C. Chloride and sodium out, potassium in

D. Sodium in, potassium out

A. peripheral nervous system

Neurons that transmit information from sensory cells to the central nervous system are part of the
A. peripheral nervous system
B. nerve net
C. spinal cord
D. brain

D. K+

The membrane of a resting neuron is much more permeable to which of the following ions than any other ion?
A. Cl-
B. Ca2+
C. Na+
D. K+
E. H+

C. open and close depending on stimuli, and are specific as to which ions can traverse them.

Two fundamental concepts about gated channels are that they
A. are always open, but the concentration gradients of ions frequently change.
B. are always closed, but ions move closer to the channels during excitation.
C. open and close depending on stimuli, and are specific as to which ions can traverse them.
D. open and close depending on chemical messengers, and are nonspecific as to which ion can traverse them.

C. potassium channels in the membrane that are permanently open.

The resting potential of a neuron is primarily produced by
A. voltage-gated channels in the membrane.
B. chemically gated channels in the membrane.
C. potassium channels in the membrane that are permanently open.
D. the concentration difference in Na+ across the membrane.

B. If membrane voltage reaches threshold potential, ions can diffuse through

Which of the following describes the mechanism of voltage-gated channel proteins?
A. If membrane voltage reaches threshold potential, ions are pumped through
B. If membrane voltage reaches threshold potential, ions can diffuse through
C. Ions are pumped through to maintain existing membrane voltage
D. When gates close, membrane voltage changes

B. metanephridia

The osmoregulatory/excretory system of an earthworm (Annelid) is based on the operation of \_____.
A. protonephridia
B. metanephridia
C. Malpighian tubules
D. nephrons

B. the concentration gradient; ATP

The force driving simple diffusion is \_____, while the energy source for active transport is \_____.
A. the concentration gradient; ADP
B. the concentration gradient; ATP
C. transmembrane pumps; electron transport
D. phosphorylated protein carriers; ATP

C. synapse

The point of connection between two communicating neurons is called the \_____.
A. axon hillock
B. dendrite
C. synapse
D. cell body

D. K+

In a resting potential, an example of a cation that is more abundant as a solute in the cytosol of a neuron than it is in the interstitial fluid outside the neuron is \_____.
A. Cl-
B. Ca2+
C. Na+
D. K+

A. the voltage-gated sodium channel.

The main ion channel responsible for the action potential is
A. the voltage-gated sodium channel.
B. the voltage-gated potassium channel.
C. the ligand-gated sodium channel.
D. the ligand-gated potassium channel.
E. the non-gated, or leaky, sodium channel.

B. prevent the depolarization phase of the action potential

A toxin that binds specifically to voltage-gated sodium channels in axons would be expected to \_____.
A. prevent the hyperpolarization phase of the action potential
B. prevent the depolarization phase of the action potential
C. prevent graded potentials
D. increase the release of neurotransmitter molecules

E. A and B

The rising phase of action potentials ends when
A. Na+ inactivation gates close
B. Voltage-gated K+ channels open
C. Voltage-gated K+ channels closes
D. A, B, and C
E. A and B

C. plasma membrane of neuron

Nerve impulses are electrical signals produced by which of the following?
A. nodes of Ranvier
B. lipid sheath of Schwann cell
C. plasma membrane of neuron
D. synapse
E. neuromuscular junction

D. Reduction in the rate of repolarization of the membrane after an action potential

Which of the following is unlikelyto be an effect caused by multiple sclerosis?
A. Reduction in the velocity of nerve impulse transmission
B. Reduction in saltatory conduction
C. Loss of electrical resistance across the membrane
D. Reduction in the rate of repolarization of the membrane after an action potential

E. depolarization stimulus for the next action potential.

Action potentials are generated along an axon as one action potential serves as the
A. action potential stimulus for the next action potential.
B. excitatory postsynaptic potential stimulus for the next action potential.
C. saltatory conduction stimulus for the next action potential.
D. monosynaptic reflex stimulus for the next action potential.
E. depolarization stimulus for the next action potential.

D. exocytosis

Neurotransmitters are released from axon terminals via \_____.
A. osmosis
B. active transport
C. diffusion
D. exocytosis

B. increase K+ permeability

How could you increase the magnitude of inhibitory postsynaptic potentials (IPSPs) generated at a synapse?
A. increase sodium-potassium pump activity
B. increase K+ permeability
C. increase the influx of calcium
D. All ofthe listed responses are correct.

B. it can be excitatory or inhibitory, depending on the type of postsynaptic membrane

When the neurotransmitter diffuses across the synaptic cleft,
A. it automatically causes depolarization of the postsynaptic membrane
B. it can be excitatory or inhibitory, depending on the type of postsynaptic membrane
C. it must move through nodes in the myelin sheath
D. a single molecule is sufficient to trigger activation of the postsynaptic membrane

B.convulsions due to constant muscle stimulation

Motor neurons release the neurotransmitter acetylcholine (ACh) and acetylcholinesterase degrades ACh in the synapse. If a neurophysiologist applies onchidal (a naturally occurring acetylcholinesterase inhibitor produced by the molluscOnchidella binneyi) to a synapse, what would you expect to happen?
A.paralysis of muscle tissue
B.convulsions due to constant muscle stimulation
C.decrease in the frequency of action potentials
D. no effect