Mastering A&P Chapter 6

A given hormone affects ________. A) only specific target cells, because nontarget cells lack the appropriate receptors B) only specific target cells, because hormones are delivered only to those cells C) all cells in the body, because hormones are secreted into blood, which is then transported everywhere D) all cells in the body, but different types of cells produce different responses to the hormone

Choose the true statement. A) Paracrine signals are used for long-distance communication. B) Cytokines are generally made in advance and stored until needed. C) Autocrine signals are produced by and act upon the same cell. D) Neurotransmitters are a type of neurohormone.

Which form of cell-to-cell communication uses the direct transfer of electrical and chemical signals? A) Gap junction signaling B) Autocrine signaling C) Contact dependent signaling D) Endocrine signaling

What determines which cells act as targets for endocrine signals? A) those cells that are derived from the same embryonic tissue as the endocrine organ B) those cells in the same area as the cells that release the hormone C) those with a high density of CAMs D) those cells with receptors specific for the signaling molecule

Choose the correct example of signal amplification. A) One hormone-producing cell alters the activity of more than one target cell. B) One hormone molecule causes the activation of more than one second messenger molecule. C) A chemical signal is converted into a mechanical signal. D) An electrical signal is converted into a mechanical signal.

The most rapid intracellular responses to signals result from activation of receptors that are also __________. A) second messengers B) enzymes C) amplifiers D) ion channels

What is the best example of a first messenger? A) Na+, which binds to the Na+/K+ATP pump and is actively transported out of a cell in exchange for K+. B) Dystrophin, which associates with costameres to transmit the force of muscle contraction to the extracellular matrix. C) Myosin, which binds to actin and causes muscle contraction. D) Insulin, which causes the target cell to take up glucose from the blood.

Which specific characteristic must a signaling molecule have in order to bind to a cytosolic or nuclear receptor? A) It must be actively transported across the membrane. B) It must contain significant polarity to allow it to associate with its receptor. C) It must be a gene activator. D) It must be lipophilic.

Which type of receptor alters the cytoskeleton when its ligand binds to it? A) Receptor-enzyme B) Integrin receptor C) G-protein-coupled receptor (GPCR) D) Receptor-channel

The binding of a single ligand to its receptor can activate many second messengers. Which characteristic of signal transduction systems is this? A) Signal amplification B) Signal specificity C) Signal initiation D) Signal conversion

What are the second messengers in the GPCR-phospholipase C signal transduction system? A) Ca2+and calmodulin B) cAMP and cGMP C) ATP and NADH D) Inositol triphosphate and diacylglycerol

Which molecule of the GPCR-adenylyl cyclase signal transduction system phosphorylates proteins to create the cellular response? A) Inositol triphosphate B) Protein kinase C C) Protein kinase A D) Phosphatase

Ion channels can be opened or closed via three signal transduction mechanisms. Two of them are extracellular signals and second messengers. What is the third mechanism for opening or closing ion channels? A) phosphorylation B) dephosphorylation C) cellular response D) G protein action

The ion that controls the widest variety of intracellular activities is __________. A) sodium B) chloride C) calcium D) potassium

Signal molecules that degrade most rapidly, resulting in very brief effects, are __________. A) paracrines B) ions C) hormones D) gases such as nitric oxide

Which is the best example of a second messenger? A) Thyroid hormone B) Adenylyl cyclase C) Intracellular Ca2+ D) Gene transcription

Which gas is also a paracrine signaling molecule? A) Sulphur dioxide B) Nitrous oxide C) Nitric oxide D) Carbon dioxide

Administration of ibuprofen can decrease pain. Why does this COX inhibitor have this effect? A) It inhibits lipoxygenase activity. B) It blocks production of the leukotrienes. C) It enhances the production of thromboxanes. D) It blocks production of prostaglandins.

The neurotransmitter norepinephrine __________. A) affects all blood vessels in the same way, because all blood vessels have only one type of norepinephrine receptor B) causes some blood vessels to dilate and others to constrict, because different vessels have different receptors for norepinephrine C) has effects that are opposite those of the neurohormone epinephrine D) affects all blood vessels in the same way, because the response of a target is specific for the neurotransmitter

Which of the following is NOT a means by which cell signal pathways are normally halted? A) The signal is halted by the binding of an inactivator molecule to the signal molecule. B) The extracellular signal molecule may be degraded. C) The extracellular signal molecule may be transported away from the receptor. D) The signal molecule may be pumped out of the cell or into storage.

α-adrenergic receptors have a higher affinity for norepinephrine than for epinephrine. β-adrenergic receptors have a higher affinity for epinephrine than for norepinephrine. Which concept about receptor function do these statements reflect? A) antagonism B) competition C) up-regulation D) amplification

Which of the following is the best example of an antagonist? A) Serotonin binds the 5-HT receptor and activates phospholipase C but not phospholipase A2. B) Glucagon binds the glucagon receptor (a G-protein-coupled receptor) and causes the release of glucose from hepatocytes. C) Epinephrine and norepinephrine each bind to α- and β-adrenergic receptors, but with different affinities. D) Atenolol is a drug that binds to β1-adrenergic receptors reducing blood pressure.

Cells can decrease receptor activity by down-regulation and through which other mechanism? A) Desensitization B) Saturation C) Demarcation D) Degradation

Cannon's second postulate states that "some systems of the body are under tonic control." What does this statement mean? A) The tonic, an area of the brain, is responsible for controlling certain body systems. B) Some organs are innervated. C) The body has the ability to adjust the levels of regulated variables. D) Some organs control themselves with little external input.

Negative feedback in reflex loops __________. A) is rare compared to positive feedback B) is common because it promotes homeostasis C) is "negative" because it opposes homeostasis D) is responsible for triggering the response to the stimulus

Compared to endocrine reflexes, neural reflexes __________. A) respond rapidly and are longer-lasting B) respond slowly, and are longer-lasting C) respond rapidly, and are very brief D) respond slowly and are very brief

The hypothalamus senses the temperature of the blood via thermoreceptors. When blood temperature begins to drop, the hypothalamus releases a hormone, TRH, that stimulates the release of TSH from the anterior pituitary gland. TSH causes the thyroid gland to release thyroid hormone (TH). TH causes an increase in body temperature, which causes the hypothalamus to stop releasing TRH. In this reflex pathway, what is the response? A) decreased release of TRH B) thermoreceptors C) increased release of TSH D) increased body temperature

Which of the following statements makes an accurate distinction between type 1 and type 2 diabetes? A) Both are characterized by an inability to make insulin. B) Both are characterized by normal levels of insulin, but the cells of the body are no longer responsive to the hormone. C) Type 1 diabetes occurs when cells of the pancreas stop making insulin while type 2 diabetes occurs when the cells are no longer sensitive to insulin. D) Type 1 diabetes is characterized by high levels of insulin while type 2 diabetes is characterized by low insulin levels.

If you give a patient who recently developed diabetes a shot of insulin and blood glucose levels do not change, what type of diabetes does he or she most likely have? A) type 2 B) type 1 C) It is possible that they could have either. D) There is not enough information to tell.

Is Marvin's high blood glucose level the direct cause for concern expressed by the nurse? A) Yes. High glucose levels are thought to be toxic to all cells of the body. B) No. Blood glucose normally spikes after a meal; it is the fact that it is high under a fasted state that suggests a problem with homeostatic controls. C) Yes. The body should never have a high level of glucose in the blood. D) No. Blood glucose levels are always high in the body and should therefore not be a cause for concern.

If glucose levels are low, how would you predict activation of the beta cell and insulin release to change? A) decrease; decrease B) increase; decrease C) increase; increase D) decrease; increase

Extracellular signal molecules are also called A) receptors. B) neurotransmitters. C) ligands. D) hormones.

Conversion of an extracellular signal into an intracellular one is called A) transcription. B) signal transduction. C) translation. D) transmogrification.

Amplifier enzymes produce A) ATP. B) phosphorylated proteins. C) second messengers. D) kinases.

Which is NOT a basic method of cell-to-cell communication? A) mechanical signals B) nerve and blood-transported signals C) cytoplasmic transfer of signals D) contact-dependent signals E) diffused chemical signals

The most significant difference between a paracrine and an autocrine is A) the route of transport. B) the cell that responds to it. C) the cell that releases it. D) the method of transport. E) There are no differences-they are the same.

Neurotransmitters and neurohormones both A) are released by neurons. B) are released by neurons and affect only cells with specific receptors. C) affect only cells with a specific receptor. D) travel in the blood to their target cell. E) are produced by all cells.

Why do some normal cells fail to respond to a chemical signal? A) Signal chemicals often break down before reaching a distant target. B) Chemical signals are only delivered to specific cells. C) Some cells are completely without receptors. D) Some cells are completely without ligands. E) Some cells lack the necessary receptors.

Receptor molecules on the surface of a cell A) bind to all ligands. B) determine that cell's response. C) determine that cell's response and may allow a particular ligand to bind. D) determine that cell's response and bind to all ligands. E) may allow a particular ligand to bind.

Receptor molecules are located A) only on the cell surface. B) only in the cytosol. C) only in the nucleus. D) only in the outer cell membrane. E) in all of these places.

Down-regulation may allow a target cell to A) only increase its number of receptors for a ligand. B) decrease the receptors' binding affinity and increase its number of receptors. C) only increase its binding affinity for a ligand. D) only decrease its number of receptors for a ligand.

Lipophilic hormones A) cannot diffuse through the cell membrane. B) function by activating cAMP. C) bind to receptors on the surface of the cell. D) function by way of a second messenger system. E) bind to receptors inside the cytoplasm or nucleus.

When adenylyl cyclase is activated, A) steroids are produced. B) cAMP is broken down. C) cAMP is formed. D) calcium ions are released from intracellular stores. E) protein kinases are metabolized.

Second messenger molecules directly A) change regulation of gene expression. B) change enzyme activity. C) change the regulation of ion channels. D) increase intracellular calcium concentration. E) All of the answers are correct.

Cyclic AMP activates A) hormone receptors. B) protein hormones. C) adenylyl cyclase. D) protein kinase A. E) a G protein.

Diacylglycerol is produced from A) cyclic AMP. B) phospholipase C. C) phosphatidylinositol bisphosphate. D) protein kinase A. E) a G protein.

What by-product results during the production of nitric oxide? A) carbon monoxide B) nitric oxide synthase C) citrulline D) carbon dioxide E) arginine

An integrating center A) is an electrical and/or chemical signal that travels to the effector. B) is the minimum stimulus that must be achieved to set the reflect response in motion. C) is the disturbance or change that sets the pathway in motion. D) evaluates incoming signals and compares it with the setpoint.

Which of the following are considered differences between endocrine and neural control systems? A) nature of the signal B) duration of action C) speed D) specificity E) All of the answers are correct.

Match the term with its description: the desired target value for a parameter A. threshold B. effector C. integrating center D. setpoint E. sensory receptor

Match the term with its description: the minimum stimulus to trigger a response A. threshold B. effector C. integrating center D. setpoint E. sensory receptor

Match the term with its description: the organ or gland that performs the change A. threshold B. effector C. integrating center D. setpoint E. sensory receptor

Match the term with its description: continuously monitors its environment for a specific variable A. threshold B. effector C. integrating center D. setpoint E. sensory receptor

Peripheral cells sensitive to the presence of hormones are called A) targets. B) receivers. C) compliments. D) complex.

A few gases are known to act as signal molecules, including all of the following except A) oxygen. B) hydrogen sulfide. C) nitric oxide. D) carbon monoxide.

Lipid signal molecules that act in a paracrine fashion and combine with G-protein coupled receptors include A) carbon monoxide and hydrogen sulfide. B) histamine and cytokines. C) eicosanoids and sphingolipids. D) arachidonic acid and leukotrienes.

A gap junction forms when opposing membrane-spanning proteins called ________ on two adjacent cells unite, creating a protein channel that is capable of opening and closing. A) G protein B) integrin C) CAMs D) connexins

________ are molecules that bind to the receptor in such a way that they block the normal ligand from binding and turning the receptor on. As a result, the signal pathway remains inactive. A) Amplifiers B) Agonists C) Antagonists D) Enzymes

If the concentration of an endocrine ligand decreases, the target cell may insert more receptors into the cell membrane in an attempt to keep its response at a normal level, in a process known as A) up-regulation. B) inhibition. C) amplification. D) down-regulation.

Most long-distance communication between cells takes place through the ________ and ________ systems with their combination of chemical and electrical signals. A) endocrine, lymphatic B) nervous, circulatory C) nervous, endocrine D) lymphatic, circulatory

An intracellular signal molecule that translates a signal from a neurotransmitter or hormone into an intracellular response is called a A) second messenger. B) first messenger. C) ligand. D) cytokine.

The secretion of the hormone insulin in response to changes in blood glucose level is an example of a ________ reflex. A) complex neuroendocrine B) simple neural C) neurohormone D) simple endocrine

Homeostatic regulation usually involves a(n) ________ that is sensitive to a particular stimulus (variable) and a(n) ________ whose activity has an effect on the same stimulus. A) receptor effector B) effector, target C) target, effector D) integration center, target

When epinephrine combines with alpha adrenergic receptors on smooth muscle in intestinal blood vessels, the blood vessels ________; however, when epinephrine binds to beta-2 adrenergic receptors on certain skeletal muscle blood vessels, the vessels ________. A) constrict, constrict B) constrict, dilate C) dilate, dilate D) dilate, constrict

The most important factor determining which type of receptor a signal molecule will bind to is A) the size of the ligand. B) the lipid solubility of the ligand. C) the size of the receptor molecule. D) the location of the receptor molecule.

When calcium becomes available inside a cell, it comes from A) extracellular fluid only. B) extracellular fluid and intracellular storage. C) intracellular storage only. D) It is always available as a major cytosol cation.

One intracellular calcium-binding protein is A) calcitriol. B) nitric oxide. C) calmodulin. D) IP3. E) calcitonin.

Signal molecule receptors exhibit A) saturation only. B) specificity, competition, and saturation. C) specificity only. D) competition only. E) competition and saturation only.

The binding of lipophilic messengers, such as steroid hormones, to their receptors triggers A) adenylyl cyclase activation. B) cyclic nucleotide formation. C) G protein inhibition. D) gene transcription. E) protein kinase activation.

Both insulin and glucagon are peptide hormones that target liver cells. The response of the target cells to each of these two hormones is opposite. This information implies that A) the two hormones bind to different receptors and use a different second messenger. B) each of the two hormones uses a different second messenger. C) the two hormones bind to different cell surface receptors. D) both hormones interact with receptors at the cell nucleus. E) one hormone binds to a receptor on the cell membrane and the other to an intracellular receptor.

Each of the following is an example of homeostasis except one. Identify the exception. A) Increased pressure in the aorta triggers mechanisms to lower blood pressure. B) A decrease in body temperature triggers a neural response that initiates physiological changes to increase body temperature. C) Increased blood sugar stimulates the release of a hormone from the pancreas that stimulates the liver to store blood sugar. D) A rise in blood calcium levels triggers the release of a hormone that lowers blood calcium levels. E) A rise in estrogen during the menstrual cycle increases the number of progesterone receptors in the uterus.