Deck 4: Principles of Neural and Hormonal Communication

Question 1

Which of the following is not a graded potential?

A) end-plate potential
B) action potential
C) slow-wave potential
D) receptor potential
E) postsynaptic potential

Answer 1

action potential

Question 2

Which of the following channels opens or closes in response to changes in membrane potential?

A) voltage-gated
B) chemical-gated
C) mechanically-gated
D) thermally-gated
E) none of these answers.

Answer 2

voltage-gated

Question 3

The rising phase of the action potential is due to

A) calcium equilibrium.
B) potassium efflux.
C) potassium influx.
D) sodium efflux.
E) sodium influx.

Answer 3

sodium influx.

Question 4

The cells of excitable and nonexcitable tissues share which of the following properties?

A) a threshold potential
B) a resting membrane potential
C) an ability to open the Na⁺ gates
D) all of these answers.
E) none of these answers.

Question 5

The negative charge established along a nerve cell membrane is due to

A) movement of Na⁺ into the cell.
B) movement of proteins out of the cell.
C) higher permeability of K⁺ relative to Na⁺.
D) intracellular protein anions.
E) both (c) and (d).

Question 6

A change in a membrane potential from -70 mV to -70 mV is an example of

A) depolarization.
B) hyperpolarization.
C) polarization.
D) repolarization.
E) zero potential.

Question 7

A change in a membrane potential from -70 mV to -90mV is an example of

A) depolarization.
B) hyperpolarization.
C) polarization.
D) repolarization.
E) zero potential.

Question 8

The falling phase of the action potential is due to

A) calcium equilibrium.
B) potassium efflux.
C) potassium influx.
D) sodium efflux.
E) sodium influx.

Question 9

At the peak of an action potential,

A) the electrical gradient for K⁺ tends to move this ion outward.
B) the concentration gradient for K⁺ tends to move this ion outward.
C) K⁺ permeability greatly increases.
D) two of these answers.
E) all of these answers.

Question 10

When chemically-gated Na⁺ channels open

A) the membrane hyperpolarizes.
B) the membrane repolarizes.
C) the membrane depolarizes.
D) the membrane becomes more negative.
E) the membrane is inhibited.

Question 11

The stronger the triggering event:

A) the larger the graded potential
B) the smaller the graded potential
C) the larger the action potential
D) the lower the frequency of action potentials
E) all of these answers.

Question 12

Myelinated axons conduct impulses much faster because

A) the myelin insulates the axon.
B) channels only have to open at the nodes.
C) voltage is not lost through along myelinated areas.
D) of saltatory conduction.
E) all of these answers.

Question 13

Which term below best describes an excitable when a resting membrane potential is present?

A) polarized.
B) depolarized.
C) hyperpolarized.
D) repolarized.
E) nonpolarized.

Question 14

Because of the presence of both activation and inactivation gates, voltage-gated Na⁺ channels can

A) be closed but capable of opening.
B) activated.
C) closed and not capable of opening.
D) all of these answers.
E) none of these answers.

Question 15

Which of the following statements concerning the absolute refractory period is inaccurate?

A) the absolute refractory period refers to the period of time during which another action potential cannot be initiated
B) the absolute refractory period corresponds to the time period during which the Na⁺ gates are first opened and then closed and inactivated.
C) the relative refractory period immediately follows the absolute refractory period
D) the absolute refractory period occurs during the after hyperpolarization phase of the action potential.
E) the absolute and relative refractory periods assure the unidirectional spread of the action potential down the nerve fiber away from the initial site of activation.

Question 16

A threshold potential is

A) the same value in every cell
B) the peak potential achieved during an action potential.
C) the point at which there is an explosive increase in Na⁺ permeability.
D) the potential at which K⁺ permeability increases.
E) always a positive potential.

Question 17

Which of the following is responsible for the falling phase of an action potential?

A) opening of Na⁺ gates
B) Na⁺-K⁺ pump restoring the ions to their original locations
C) greatly increased permeability to K⁺
D) ATP-ase destroying the energy supply that was maintaining the action potential at its peak.
E) none of these answers.

Question 18

During the rising phase of the action potential,

A) P_K+ is much greater than P_Na+.
B) P_Na+. is much greater than P_K+.
C) P_K+ is the same as P_Na+
D) Na⁺ efflux occurs.
E) two of these answers.

Question 19

Graded potentials

A) are local changes in membrane potential that occur in varying degrees of magnitude.
B) serve as short-distance signals.
C) serve as long-distance signals.
D) both (a) and (b).
E) both (a) and (c).

Question 20

When a membrane is stimulated due to opening of chemically-gated Na? channels

A) an impulse is propagated.
B) a graded potential is established.
C) an action potential is inhibited
D) the voltage across the membrane becomes more negative.
E) the voltage across the membrane stays the same.

Question 21

When an action potential is over and the membrane has returned to resting potential, the voltage-gated sodium channel:

A) is closed and not capable of opening
B) is closed and capable of opening
C) is open
D) open and not capable of closing
E) two of these answers.

Question 22

The refractory period

A) prevents action potentials from spreading forward and backward.
B) refers to the time period during which a portion of the membrane that has just undergone an action potential cannot undergo another action potential in response to normal triggering events because the channels opened during the action potential have not been restored to their "closed but capable of opening" conformation.
C) places an upper limit on the frequency with which a neuron can conduct action potentials.
D) two of these answers.
E) all of these answers.

Question 23

Which of the following statements concerning propagation of action potentials is incorrect?

A) saltatory conduction occurs in myelinated nerve fibers.
B) during conduction by local current flow, there is a flow of current between the active and adjacent inactive area of the cell membrane, thereby decreasing the potential in the inactive area to threshold.
C) the action potential jumps from one Schwann cell to the adjacent Schwann cell in a myelinated fiber.
D) saltatory conduction is faster than conduction by local current flow.
E) conduction by local current flow is the method of propagation in unmyelinated fibers.

Question 24

The membrane is more permeable to K⁺ than to Na⁺

A) at resting potential.
B) during the rising phase of an action potential.
C) during the falling phase of an action potential.
D) both (a) and (b).
E) both (a) and (c).

Question 25

The trigger zone of a neuron

A) is at the axon terminal
B) is located in the hillock
C) contains voltage gated channels
D) both (b) and (c) above
E) all of these answers.

Question 26

Temporal summation takes place when

A) two EPSPs from the same presynaptic input occur so closely together in time that they add together or sum.
B) an EPSP and an IPSP occur simultaneously in time and cancel each other out.
C) two EPSPs that occur simultaneously from different presynaptic inputs add together or sum.
D) action potentials occurring in two presynaptic inputs simultaneously converge upon the postsynaptic cell, initiating two different action potentials in the postsynaptic cell.
E) none of these answers.

Question 27

Saltatory conduction

A) occurs in unmyelinated nerve fibers.
B) is slower than conduction by local current flow because the myelin acts as an insulator to slow the impulse down.
C) involves the impulse jumping from one node of Ranvier to the adjacent node.
D) refers to the action potential spreading from one Schwann cell to the adjacent Schwann cell.
E) more than one of these answers.

Question 28

Voltage-gated K⁺ channels:

A) are closed during the falling phase of the action potential
B) are slow to close
C) are activated at threshold, but open a short time later
D) both b and c
E) all of the above

Question 29

At an excitatory synapse, an action potential in the

A) postsynaptic neuron depolarizes the presynaptic cell membrane.
B) presynaptic neuron increases the permeability of the subsynaptic membrane of the postsynaptic cell to both Na⁺ and K⁺.
C) presynaptic neuron increases the permeability of the subsynaptic membrane of the postsynaptic cell to K⁺ only.
D) both (a) and (b) above.
E) both (a) and (c) above.

Question 30

A drug that blocks the reuptake of a NT in a synapse:

A) decreases the amount of NT in the synapse
B) decreases the function of the synapse
C) acts on the presynaptic cell
D) acts on the postsynaptic cell

Question 31

The relative refractory period occurs after the action potential is complete because of the

A) lingering inactivation of the voltage-gated Na⁺ channels.
B) slowness of the voltage-gated channels.
C) the sodium-potassium pump.
D) both (a) and (b).
E) both (b) and (c).

Question 32

Which protein(s) is/are responsible for development of the resting membrane potential?

A) leak channels.
B) gated channels.
C) pumps.
D) both (a) and (b) above.
E) both (a) and (c) above.

Question 33

During the peak of the action potential which ion has the greatest permeability?

A) sodium.
B) potassium.
C) calcium.
D) chloride.
E) protein.

Question 34

The period of time following an action potential during which a membrane cannot be restimulated no matter how strong the stimulus

A) is known as the absolute refractory period.
B) occurs during the time after the Na+ gates have opened until they are restored to their "closed but capable of opening" conformation.
C) prevents the action potential from spreading back over the part of the membrane where the impulse has just passed.
D) two of these.
E) all of these answers.

Question 35

Select the incorrect statement about the action potential.

A) it has an all-or-none characteristic.
B) it has a refractory period.
C) it is triggered by depolarization to threshold.
D) it occurs along a plasma membrane.
E) it speeds up transmission by summation.

Question 36

Conduction by local current flow

A) occurs in unmyelinated fibers.
B) is faster than propagation of an action potential in myelinated fibers because myelin acts as an insulator to slow down the impulse.
C) involves current flowing locally between the active and adjacent inactive areas, thereby bringing the inactive areas to threshold so that they too become active (i.e., have an action potential).
D) both (a) and (c) above.
E) all of these answers.

Question 37

Spatial summation occurs in a postsynaptic neuron

A) when several EPSPs from a single presynaptic input sum to reach threshold.
B) when EPSPs from several presynaptic inputs sum to reach threshold.
C) upon simultaneous interaction of an EPSP and an IPSP.
D) when several IPSPs from a single presynaptic input sum to hyperpolarize the membrane.
E) none of these answers.

Question 38

Which of the following nerve fibers will have the highest conduction velocity when compared to an unmyelinated nerve fiber with conduction velocity = 0.35 m/sec.

A) a dendrite
B) a smaller unmyelinated nerve fiber
C) a myelinated nerve fiber the same size
D) a larger myelinated fiber
E) it is impossible to determine with the information provided.

Question 39

Permeability of which ion is affected by a positive feedback mechanism once threshold is reached?

A) sodium.
B) potassium.
C) calcium.
D) chloride.
E) protein.

Question 40

Which statement regarding graded potentials is false?

A) they are decremental.
B) they travel only short distances.
C) they are self-propagating.
D) they may contribute to the development of an action potential.
E) they travel in both directions along the membrane.

Question 41

The specificity of hormones is due to

A) specialized hormone secretion.
B) molecular rearrangement at the site of action.
C) specific binding of hormones to plasma proteins.
D) specialization of target-cell receptors.
E) inactivation of hormones by the kidneys.

Question 42

Hormones are classified into the following three types:

A) amines, peptides, and steroids.
B) amines, steroids, and phospholipids
C) amines, phospholipids, and steroids.
D) amines, free fatty acids, and peptides.
E) free fatty acids, peptides, and steroids.

Question 43

The most common second messenger used by hydrophilic hormones is

A) calcium.
B) cyclic AMP.
C) chromatin.
D) messenger RNA.
E) plasma proteins.

Question 44

Which of the following statements concerning peptide hormones is incorrect?

A) Peptides are synthesized by the endoplasmic reticulum-Golgi complex system.
B) Peptides circulate largely bound to plasma proteins.
C) Peptides bind to surface receptors of their target cells.
D) Peptides exert their effect largely by means of second-messenger systems.
E) Peptides are released by exocytosis upon appropriate stimulation.

Question 45

Which of the class(es) of hormones interacts with DNA?

A) proteins.
B) catecholamines.
C) steroids.
D) amines
E) both (a) and (b) above.

Question 46

All hormones

A) are regulated by the hypothalamus.
B) initiate synthesis of new proteins.
C) are secreted by endocrine glands through ducts into the blood.
D) must combine with specific receptors on the target cells in order to exert their effects.
E) are produced in a gland and target cells in different tissues.

Question 47

Which of the classes of hormones are synthesized by the endoplasmic reticulum-Golgi complex mechanism?

A) peptides
B) catecholamines
C) steroids
D) thyroid hormone
E) both peptides and catecholamines are correct.

Question 48

Which of the following is not associated with the postreceptor events of hydrophilic hormones?

A) cyclic AMP.
B) protein kinase.
C) adenylate cyclase.
D) chromatin.
E) phosphorylated enzymes.

Question 49

Which of the classes of hormones triggers the synthesis of new intracellular proteins within the target cell?

A) peptides.
B) catecholamines.
C) steroids.
D) thyroid hormone.
E) both steroids and thyroid hormone are correct.

Question 50

Which of the classes of hormones is derived from large preprohormones?

A) peptides.
B) estrogen
C) steroids.
D) both (a) and (b) above.
E) all of the above

Question 51

Select the incorrect statement about the postreceptor events of hydrophilic hormones.

A) Adenyl cyclase forms cAMP.
B) cAMP is a secondary messenger.
C) Some hydrophilic hormones use calcium ions as a secondary messenger.
D) The hydrophilic hormone binds to a cytoplasmic receptor to activate the second messenger system
E) cAMP activates protein kinase

Question 52

Which of the following is true about hormones?

A) are released from exocrine glands.
B) interact with receptors at target-cell sites.
C) are synthesized in the lymph nodes.
D) interact with receptors in the blood.
E) are all similar chemically.

Question 53

Neurosecretory neurons

A) release neurotransmitters.
B) release hormones.
C) are unable to conduct action potentials, unlike ordinary neurons.
D) both release neurotransmitters and are unable to conduct action potentials, unlike ordinary neurons.
E) both release hormones and are unable to conduct action potentials, unlike ordinary neurons.

Question 54

Which class(s) of hormone(s) is not stored in the secretory cell after being synthesized?

A) peptides.
B) catecholamines.
C) steroids.
D) thyroid hormone.
E) both steroids and thyroid hormone are correct.

Question 55

Lipophilic hormones

A) include steroids and thyroid hormone.
B) bind with receptors located inside their target cells.
C) activate second-messenger systems within their target cells.
D) both (a) and (b) above.
E) all of these answers.

Question 56

Steroids

A) are lipophilic.
B) are derived from cholesterol.
C) initiate the synthesis of specific new proteins within their target cells.
D) are lipophilic and derived from cholesterol.
E) all of these answers.

Question 57

Hormones

A) are all of similar chemical composition.
B) combine with specific receptors on the target cell's surface or inside the target cell.
C) are secreted at a constant rate.
D) are also known as paracrines
E) all of these answers.

Question 58

Which of the following statements concerning hormones is incorrect?

A) a single endocrine gland may produce multiple hormones.
B) a single target cell may be influenced by more than one hormone.
C) a single hormone can influence only one type of target cell.
D) an endocrine organ may exert nonendocrine functions in addition to secreting hormones.
E) the same hormone may be secreted by more than one endocrine gland.

Question 59

Amine hormones:

A) are derived from amino acids
B) are always hydrophilic
C) area always hydrophobic
D) are derived from cholesterol
E) are also known as steroids

Question 60

Which hormone class would utilize second messenger systems?

A) lipophillic
B) hydrophilic
C) steroids
D) those with receptors inside the cell
E) all of these answers.

Question 61

A high percentage of sodium and potassium ions move during each action potential.

Question 62

As the stimulus strength increases, the amplitude of a graded potential decreases.

Question 63

In a graded potential the direction of current flow is designated by the movement of positive charges.

Question 64

Lipophilic hormones must interact with which of the following prior to gene activation?

A) membrane receptors.
B) molecular chaperones.
C) hormone response elements.
D) both (a) and (b) above.
E) both (b) and (c) above.

Question 65

The Na? and K? channels that open and close during an action potential are voltage-gated channels.

Question 66

The current flow of a action potential fades quickly.

Question 67

Catecholamines:

A) are derived from cholesterol
B) are secreted by the adrenal medulla
C) include epinephrine as the major hormone
D) include estrogen and testosterone
E) are lipophilic

Question 68

Along a neuron, an action potential normally travels from the dendrites to the cell body to the axon.

Question 69

During the resting potential, many potassium channels are open in the plasma membrane.

Question 70

Which of the following hormone types does not require membrane receptors to invoke cell responses?

A) peptides
B) catecholamines
C) steroids
D) thyroid hormone
E) both (c) and (d) above.

Question 71

After an action potential has occurred, there is more Na? inside the cell than outside the cell (before any Na?-K? pump activity has taken place).

Question 72

In the second-messenger

A) a small amount of one hormone (the second messenger) is required to release another.
B) a tropic hormone (the first messenger) stimulates secretion of another hormone (the second messenger).
C) the hormone first binds to a specific surface receptor, whereupon the hormone-receptor complex moves into the cell to combine with a specific intracellular receptor.
D) releasing hormones (the first messenger) from the hypothalamus regulate many anterior pituitary hormones (the second messenger).
E) a hormone (the first messenger) binds to surface receptors activating adenylate cyclase, catalyzing cAMP formation.

Question 73

Which statement is characteristic of the endocrine system?

A) it is considered "wireless"
B) utilizes neurotransmitters
C) is effective over short distances
D) has a rapid response
E) coordinates precise responses

Question 74

Which characteristic below is not shared by both lipophilic and hydrophilic hormones?

A) amplification of hormone actions in the target cell.
B) transport via plasma proteins.
C) regulation of metabolic reactions.
D) initiation of second messenger systems.
E) both (b) and (d) above.

Question 75

Direct intercellular communication involves

A) communication through gap junctions
B) communication through direct linkups via surface markers
C) extracellular chemical messengers
D) (a) and (b) above
E) all of the above

Question 76

Repolarization occurs between the rising and falling phase of an action potential.

Question 77

In which way can a hormone's response at the target tissue be modified?

A) cascade effect of second messenger pathways
B) inactivation of second messenger pathways by another hormone
C) changing the number of receptors on the target cell
D) changing the affinity of the receptors on the target cell
E) all of these answers.

Question 78

Threshold potential is the peak potential achieved during an action potential.

Question 79

During conduction by local current flow, current flows locally between the active and adjacent inactive area of the cell membrane, thereby decreasing the potential in the inactive area to threshold.

Question 80

Nerve and muscle cells establish resting membrane potentials.