Chapter 11, 16, 18, 21 Questions

Assume you have a membrane with only potassium leakage channels. The RMP is -90mV. Predict the RMP if we add Na+Na+ leakage channels.The most likely RMP value of Na+Na+ is __________.

-70 mV

Cl−Cl− is a common, negatively charged extracellular ion. Predict the effect on the RMP if many Cl−Cl− gated channels are suddenly opened.

A more negative RMP would result. Submit

Which of the following is true of axons?

A neuron can have only one axon, but the axon may have occasional branches along its length.

Which of the following hormone pairs exhibit an antagonistic relationship?

Angiotensin II & ANP

Adult onset diabetes, diabetes type 2, can best be described using which of the following concepts?

Constantly high blood sugar leads to high insulin release. High amounts of insulin lead to down-regulation of insulin receptors.

What type of conduction takes place in unmyelinated axons?

Continuous conduction

Which of the following adrenal gland homeostatic imbalances is characterized by persistent elevated blood glucose levels, dramatic losses in muscle and bone protein, and water and salt retention, leading to hypertension and edema?

Cushing's syndrome

Which description of synapses is not correct?

Direct signaling involves the activation of G proteins.

People who have hydrocephaly often have an issue with which of these glial cell types?

Ependymal cells

More Na+ than K+ leaks through neuron membranes because of the properties of the non-gated leak channels.

False

Second messenger signaling systems produce small but rapid target cell effects.

False

Steroid hormones are synthesized from amino acids.

False

The hypothalamus is known to control the activity of the thyroid, which has traditionally been called the master endocrine gland.

False

Up-regulation involves the loss of receptors and prevents the target cells from overreacting to persistently high hormone levels.

False

Water-soluble hormones are inactivated and removed from the blood by the liver.

False

How do endocrine hormones reach their target cells?

Hormones are transported through the blood stream to target cells.

What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?

Inactivation gates of voltage-gated Na+‎ channels close, while activation gates of voltage-gated K+‎ channels open.

People with multiple sclerosis (MS) experience many challenging symptoms. Which statement best explains one cause of these difficulties?

Loss of oligodendrocytes in the central nervous system results in absence of the myelin sheath of neuronal axons, impairing rapid saltatory conduction.

Match the words in the left column to the appropriate phrases on the right. Make certain each word is matched with a phrase before submitting your answer.

Membrane potential of −−70 mVmV Membrane potential of −70 m V: The resting membrane potential of the cell : The resting membrane potential of the cell K+K+ permeability K + permeability: The primary determinant of the resting membrane potential : The primary determinant of the resting membrane potential Na+Na+ permeability N a + permeability: Although it plays a role, it is not a primary determinant of the resting membrane potential : Although it plays a role, it is not a primary determinant of the resting membrane potential Membrane potential of −−90 mVmV Membrane potential of −90 m V: The point at which there is no net movement of K + into or out of the cell : The point at which there is no net movement of K+K+ into or out of the cell

For each of the following, indicate whether the condition will cause the membrane potential to become more positive, more negative, or largely unchanged when compared to the normal physiological resting membrane potential. Drag the appropriate items to their respective bins.

More Positive Triple the number of Na+Na+ leak channels Double the concentration of K+K+ outside the cell More Negative Double the number of K+K+ leak channels Decrease the concentration of Na+Na+ outside the cell by half Largely Unchanged Double the size of the cell, without adding channels Double the number of closed channels for K+K+

In which type of axon will velocity of action potential conduction be the fastest?

Myelinated axons with the largest diameter

The concentrations of which two ions are highest outside the cell?

Na+ and Cl−

Which of the following does NOT describe conditions that occur during an action potential?

Na+ is used to repolarize the membrane.

Which of the following is a hormone produced by the posterior pituitary?

None of the listed responses is correct. Submit

Which of the following does NOT describe the process of summation?

One EPSP fails to bring the cell to threshold.

What is the role of activated protein kinases?

Phosphorylate proteins.

Which of the following is NOT one of the basic functions of the nervous system?

Release hormones into the bloodstream that travel around the systemic blood circulation to communicate with cells in multiple locations within the body.

Which of the following peripheral nervous system (PNS) neuroglia form the myelin sheaths around larger nerve fibers in the PNS?

Schwann cells

Which of the following statements is correct regarding the polarization of a neuronal membrane and the formation of a resting membrane potential?

Sodium/Potassium pumps maintain concentration gradients; sodium and potassium move down their concentration gradients through leakage channels.

Imagine that the cell membrane from the previous problem becomes more permeable to Na+Na+. Predict how this will affect the RMP.

The RMP will be more positive.

You are going to record RMP from a cell using an electrode. You place your electrode and record a resting membrane potential every millisecond. You record an initial value of -70mV; however, over time you notice that your recordings become more and more positive until the RMP reaches 0mV. Assuming that Na+Na+ and K+K+ are the major determinants of RMP in this cell, which of the following could best explain your results?

The cell's Na+Na+-K+K+ ATPase pumps have stopped functioning.

The resting membrane potential is dependent upon two important factors: 1) differences in sodium and potassium concentrations across the membrane (electrochemical gradients) and 2) differences in sodium and potassium membrane permeability. This activity will help you to review how the resting membrane potential of cells are generated and maintained. Use the provided ions to correctly complete each sentence about the resting membrane potential. Ions may be used more than once, or not at all.

The concentration of Na+ is higher outside than inside the cell. The concentration of K+ is higher inside than outside the cell. The resting membrane potential is maintained by Na+-K+ pumps that actively transport K+ into and Na+ out of the cell. The membrane is more permeable to K+.

Many neurons have many short, branching extensions called dendrites. What is the benefit of these structures for a neuron?

The dendrites provide a large surface area for connections from other neurons.

In a lab you are conducting tests with various chemicals and neurotransmitter receptors. You notice that exposed frog muscle cells depolarize when you add the chemical nicotine to the acetylcholine (ACh) receptors. What does this tell us about the relationship between neurotransmitters and their receptors?

The effect of a neurotransmitter is based on the properties of the receptor more than the neurotransmitter.

Why does regeneration of the action potential occur in one direction, rather than in two directions?

The inactivation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just fired an action potential. Submit

Which of the following is NOT a difference between graded potentials and action potentials?

The magnitude of action potentials decrease as the impulse travels further away from the start of the impulse while graded potentials do not decrease in magnitude.

What is the function of the myelin sheath?

The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.

You discover that a new chemical compound interacts with K+ voltage-dependent channels. What would be the effect on a neuron if the chemical came into contact with the axonal membrane?

The neuron would be unable to repolarize. Submit

Match these prefixes to their meanings.

The prefix neuro- means "pertaining to the nervous system." The prefix endo- means "within." The prefix hyper- means "higher than normal." The prefix de- means "do the opposite of or reverse." The prefix peri- means "around" or "surrounding." The prefix syn- means "being together" or "similar."

Which mechanism allows the rabies virus to gain access to the central nervous system (CNS)?

The rabies virus uses retrograde movement along the neuronal axon.

What is the basic condition when a neuron is described as polarized?

There is a separation of positive and negative charges across a membrane.

Which of the following is NOT representative of endocrine glands?

They use ducts to secrete their products into the surrounding tissue fluid.

Action potentials (nerve impulses) are changes in the membrane potential that, once started, will affect the entire excitable membrane. The first action potential is usually generated at the initial segment of the neuron's axon. This activity will test your understanding of the sequence of events that occur at the membrane of the initial segment of the axon during generation of an action potential. Place the events involved in generation of an action potential in the correct order of occurrence from left to right.

Threshold stimulusNa+ channels open Na+ influxDepolarization Na+ channels closeK+ channels open K+ effluxRepolarization HyperpolarizationK+ channels close

Bundles of axons in the central nervous system are called tracts.

True

If the neuron membrane becomes more permeable to Na+, Na+ will transport across the membrane, causing the cell to depolarize.

True

Opening K+ or Cl- channels in a postsynaptic membrane would produce an inhibitory postsynaptic potential (IPSP).

True

The adrenal medulla is stimulated to release catecholamines during a stress response.

True

Match these vocabulary terms to their meanings.

When potassium channels have been open long enough to over-shoot resting membrane potential, hyperpolarization has occurred. Endorphins are a group of natural chemicals that reduce the perception of pain. When a neuron is stimulated and sodium channels open, the process of depolarization has begun. Supporting cells of the nervous system are collectively called neuroglia. Two consecutive neurons communicate at a synapse, where they physically come together. Structures of the nervous system surrounding, but not part of the central nervous system are part of the peripheral nervous system.

What type of event is required for an action potential to be generated?

a threshold level depolarization

What is the primary function of hormones?

act as chemical messengers that regulate the metabolic function of cells in the body Submit

Which of the following is characteristic of water-soluble hormones?

acting through second messengers at their target cells

Which of the following is NOT an endocrine gland?

adenoid

Secretion of __________ is increased in response to stress.

adrenocorticotropic hormone

Which hormone is essential to our ability to maintain our fluid levels?

aldosterone

Cold sores on the skin of the mouth occur when herpes simplex viruses that are dormant in neural ganglia become active and travel to the skin of the mouth. Which of the following is the mechanism by which these viruses travel from the ganglia (located within the head) to the skin of the mouth?

anterograde transport

Which hormone aids in water resorption?

antidiuretic hormone

Which of the following hormones helps the body avoid dehydration?

antidiuretic hormone

Which glial cells have the most diversity of function?

astrocytes

The amplification of the signal from a water-soluble hormone is achieved through an increase in _______.

cAMP in the cytoplasm

Which of the following is a factor that determines the rate of impulse propagation, or conduction velocity, along an axon?

degree of myelination of the axon Submit

Which of the following events would be directly affected if a neuron had a mutation that prevented the production of voltage-gated Na+ channels?

depolarization leading to action potentials

An action potential is self-regenerating because __________.

depolarizing currents established by the influx of Na+‎ flow down the axon and trigger an action potential at the next segment

Which of the following is not a major type of stimulus that triggers endocrine glands to manufacture and release hormones?

enzymatic

Which membrane potential occurs because of the influx of Na+ through chemically gated channels in the receptive region of a neuron?

excitatory postsynaptic potential

Which of the following hormones has significantly different effects when it is released in males instead of females?

follicle-stimulating hormone

Which pancreatic hormone functions to raise blood glucose levels?

glucagon

What is directly required for the production of anterior pituitary gland hormones?

hormonal stimuli

What component of the reflex arc determines the response to a stimulus?

integration center

When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron,

ion channels in the plasma membrane of the receiving neuron open.

Which of the following types of glial cells monitors the health of neurons, and can transform into a special type of macrophage to protect endangered neurons?

microglia

Ependymal cells line many open cavities in the central nervous system (CNS). Ependymal cells have cilia on the side of the cell that face these openings. What is the most likely function of these ciliated cells?

movement and circulation of cerebrospinal fluid

Complete the following sentence. The operation of the Na+−K+Na+−K+ ATPase pump __________.

moves 3 Na+Na+ to the ECF and 2 K+K+ to the cytoplasm

Which of the following pairings does not fit?

multipolar neurons: peripheral nervous system sensory neurons

A molecule that carries information across a synaptic cleft is a

neurotransmitter.

In multiple sclerosis, the cells that are the target of an autoimmune attack are the _________.

oligodendrocytes Submit

Let's consider a scenario in which the resting membrane potential changes from −−70 mVmV to +70 mVmV, but the concentrations of all ions in the intracellular and extracellular fluids are unchanged. Predict how this change in membrane potential affects the movement of Na+Na+. The electrical gradient for Na+Na+ would tend to move Na+Na+ __________ while the chemical gradient for Na+Na+ would tend to move Na+Na+ __________.

out; in

A resting neuron is an unstimulated neuron that is not presently generating an action potential. The resting membrane potential is the separation of the relative positive and negative charges across the membrane of a cell at rest. Drag the charges to the correct side of the membrane to represent the resting membrane potential of a typical neuron.

outside + inside -

In the brain, vision originates in the rods and cones in the retina. Separate regions of the brain decode basic information, like color, shapes, intensity of light, and there are other regions that decode information like position in space, and awareness of patterns. As you use your visual system, all of these regions are working simultaneously. This simultaneous awareness of all regions working at the same time is due to which processing pattern listed below?

parallel processing Submit

Which gland secretes the most important hormone controlling calcium balance in the blood?

parathyroid

Water-soluble hormones affect target cells by binding to __________.

plasma membrane receptors

Which of the following is NOT a type of circuit?

pre-synaptic circuits

You are working on a new medication to selectively kill cancer cells. You test the drug on a culture of normal neurons to check for any side effects. Despite the presence of the drug, a normal resting membrane potential of −−70 mVmV is maintained. Look at each of the figures below to analyze how the drug might be affecting the neuron. Figure A shows neuron activity under normal, or control, conditions (without the drug). Figure B shows neuron activity that has been altered due to exposure to the drug. Based on these results, the drug is most likely __________.

preventing Na+Na+-gated channels from opening

Which hormone stimulates mammary glands to produce milk in nursing mothers?

prolactin

Which neuron circuit pattern is involved in the control of rhythmic activities such as breathing?

reverberating circuit

Which of the following circuit types is involved in the control of rhythmic activities such as the sleep-wake cycle, breathing, and certain motor activities (such as arm swinging when walking)?

reverberating circuits

What division of the nervous system is most specifically responsible for voluntary motor control?

somatic nervous system

The small space between the sending neuron and the receiving neuron is the

synaptic cleft.

Which of the following occurs in situations where different hormones produce the same effects at the same target cell and their combined effects are amplified?

synergism

Which is the main receptive portion of the neuron?

the dendrite

Which criterion is used to functionally classify neurons?

the direction in which the nerve impulse travels relative to the central nervous system Submit

What determines whether a particular cell is able to respond to a hormone?

the presence of a specific hormone receptor Submit

If a signal from a sending neuron makes the receiving neuron more negative inside,

the receiving neuron is less likely to generate an action potential.

As you start working out, you notice that your heart rate and breathing rate start to increase. Which division of your nervous system is generating this response? Be as specific as possible.

the sympathetic division of the autonomic nervous system

When calcium ions enter the synaptic terminal,

they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron. Submit

Which choice best characterizes K+ leakage channels?

transmembrane protein channels that are always open to allow K+K+ to cross the membrane without the additional input of energy

The various hormones secreted by the anterior pituitary that regulate the secretion of hormones from other endocrine organs are called __________.

tropins

The generation of an action potential in a neuron requires the presence what type of membrane channels?

voltage-gated channels

Which of the following pairs correctly matches the adrenal gland structure with the class of hormones it produces?

zona glomerulosa: mineralocorticoids Submit