ch 5 physiology

In chemical communication between cells, a ________ cell secretes a chemical messenger that binds to ________ on the ________ cell.

secretory : receptors : target

Direct communication between cells in contact with one another is accomplished through _____.

gap junctions.

The number of bound receptors on a target cell depends on what two things?

the concentration of the messenger and the concentration of receptors on the target cell

Which type of chemical messenger, when released, binds to receptors on the cell that released the chemical messenger?

autocrine

Which type of chemical messenger is released into the bloodstream by an endocrine gland where it can affect target cells throughout the body?

hormone

Which type of chemical messenger is released from the axon terminal of a neuron and directly communicates with other cells?

E) neurotransmitter

Communication across a synapse is initiated by the release of a neurotransmitter from the ________ region of the neuron.

B) axon terminal

Vasopressin (antidiuretic hormone), which is released from the posterior pituitary, is an example of what type of chemical messenger?

D) neurohormone

Inflammation is characterized in part by redness and swelling. In inflammation, ________ increases blood flow to affected tissues (producing redness) and causes fluid to leak out of the blood vessels and into the tissue (producing swelling).

C) histamine

The more specific a drug is for a certain ________ type, the more specific the therapeutic actions of the drug and the fewer the side effects.

B) receptor

Which of the following chemical messengers is lipophilic and is therefore able to cross the cell membrane?

D) eicosanoids

Histamine acts as a(n) ________ in its role in inflammation.

A) paracrine

What molecules are hydrophobic and can easily cross the plasma membrane?

C) lipophilic

All the messengers in what class are derived from cholesterol?

C) steroids

Most amines are ___*, meaning they dissolve in water and therefore cannot cross the cell membrane. The _*__ hormones are an exception because they are ________ and can easily cross the cell membrane.

C) lipophobic : thyroid : lipophilic

Peptide hormones are made___*, stored and released via _*__.

B) in advance : exocytosis

Cells that secrete dopamine must contain which enzymes?

E) tyrosine β-hydroxylase and dopa decarboxylase

Cells that secrete epinephrine must contain which enzymes?

D) dopamine β-hydroxylase, tyrosine β-hydroxylase, phenylethanolamine N-methyl transferase, and dopa decarboxylase

Catecholamines are derived from what amino acid?

C) tyrosine

Thyroid hormones are synthesized from what amino acid?

C) tyrosine

Aspirin is a nonsteroidal anti-inflammatory drug (NSAID) that relieves pain. Which mechanism best describes how NSAIDs work?

C) Prostaglandins (PG) are eicosanoids that produce pain and inflammation. Cyclooxygenase (COX) is an essential enzyme in the production of PG and aspirin inhibits COX and therefore relieves pain due to the reduced production of PG.

Doctors often prescribe baby aspirin (82 mg) to guard against the formation of blood clots instead of a higher dose of 350 mg found in a regular aspirin. Which statement best describes the distinction in dosages?

C) Aspirin causes several side effects, some good and some bad. Aspirin decreases thromboxane A2 which causes blood clots; however, at higher dosages, it also decreases the production of PGI2 (prostacyclin) that inhibits production of blood clots. Thus, higher dosages of aspirin would actually promote the formation of blood clots.

Once a steroid hormone is synthesized, it is

A) immediately capable of diffusing across the membrane.

What organelle packages peptide/protein messengers into secretory vesicles?

D) Golgi apparatus

In order to synthesize eicosanoids, ________ catalyzes the release of ________ from a membrane phospholipid.

C) phospholipase A2 : arachidonic acid

An equilibrium exists between a hormone that is bound to a carrier protein and a free hormone such that, as the amount of free hormone increases,

D) more free hormone will become bound to carrier proteins.

Lipophilic chemical messengers are poorly soluble in water. However, many of these lipophilic messengers are transported throughout the body. Their transport in blood (water) is facilitated by

C) carrier proteins.

What enzyme catalyzes synthesis of prostaglandins from arachidonic acid?

D) cyclooxygenase

A half-life, in terms of a chemical messenger, refers to

A) the time it takes for half of the chemical messenger in the blood to be degraded.

Androgens are precursor molecules for the synthesis of

A) estradiol.

Progesterone is a potential precursor for the synthesis of

B) cortisol.

Aspirin decreases inflammation by inhibiting the actions of what enzyme?

B) cyclooxygenase

Hormones that are dissolved in blood typically exhibit a half-life on the order of ___*, whereas hormones that are bound to carrier proteins can remain undegraded for _*__.

C) minutes : hours

The location of receptors on a target cell depends on the solubility of the chemical messenger. Where would the receptors for lipophilic messengers be located?

B) on the inside of the cell

The β1 adrenergic receptor has the greatest affinity for what messenger?

E) epinephrine and norepinephrine equally

The α1 adrenergic receptor has the greatest affinity for what messenger?

A) norepinephrine

Which of the following will NOT affect the magnitude of a cell's response to a specific hydrophilic ligand?

E) lipid solubility of the ligand

Chronic exposure to a ligand (messenger) ________ the receptor population for that chemical messenger on the target cell.

D) down regulates

Which of the following statements best describes the release of lipophobic messengers?

A) Lipophobic messengers are stored in vesicles and released by exocytosis in response to a stimulus.

Which of the following statements best describes the release of a lipophilic messenger?

C) Lipophilic messengers are released immediately upon synthesis by simple diffusion.

Lipophilic hormones are transported in blood ________ and bind to receptors located ________.

D) bound to carrier proteins : inside the target cell

Much evidence suggests that depression might be associated with deficiencies in the biogenic amines serotonin and norepinephrine. If this is true and the body has reduced concentrations of these amines, one might predict the body would ________ in order to adapt to these lowered levels.

A) upregulate

What is a molecule that is similar in structure to a messenger and binds with that messenger's receptor to stimulate a similar response from the target cell?

D) agonist

As a general rule, the magnitude of a target cell's response to a chemical messenger depends on which three factors?

C) (1) the concentration of the messenger, (2) the number of receptors, and (3) the affinity of the receptor for the messenger

The affinity of a receptor for its ligand is a measure of the

A) strength of binding between ligand and receptor.

Typical responses to ________ messengers require a long time to develop because they necessitate transcription of mRNA and translation of that mRNA into a functional protein.

B) lipophilic

Insulin is a peptide hormone and therefore lipophobic. When insulin is released due to high blood glucose levels, the response of the cells to this hormone will be ________ because it causes ________.

A) fast : enzyme-linked receptors to catalyze intracellular reactions

Heroin overdose is usually treated with an opioid ________ such as naloxone (Narcan) or naltrexone, an opioid, which prevents heroin from binding to mu receptors and reverses the effects of heroin on the body.

A) antagonist

Differences in the rate of activity between fast and slow ligand-gated channels are caused by

D) G protein activity gating the slow channel.

Opening channels for which of the following ions can trigger exocytosis?

C) calcium

Which of the following ions binds to calmodulin to ultimately activate a protein kinase?

C) calcium

A first messenger is an extracellular messenger that binds to its receptor on the ________ of the cell and therefore activates a second messenger system.

B) outside

Which of the following statements best describes the function of tyrosine kinase?

C) It catalyzes the phosphorylation of a protein inside a cell.

Cholera is the leading cause of death in children in developing countries, characterized by massive diarrhea. The effects stem from an extracellular toxin that the bacterium Vibrio cholerae releases into the gut. The toxin acts on a ________ that overstimulates ________ which causes a cascade of events that leads to electrolytes leaving the cell and causing water to follow them into the lumen of the intestine, resulting in severe diarrhea.

A) G proteins : adenylate cyclase

Which of the following is the most common second messenger in the human body?

A) cAMP

What terminates the cAMP second messenger system?

C) the degradation of cAMP by the enzyme cAMP

Cyclic AMP (cAMP) stimulates one's metabolic rate. Many supplement companies offer products claiming to increase the levels of this chemical within the body. If you had a patient on this supplement and they had high levels of cAMP in their body, what symptoms would you expect them to display?

A) weight loss and a high temperature

The function of a second messenger system is to

D) amplify the response of the first messenger.

Based on your knowledge of signal amplification, which type of chemical messenger can have relatively small concentrations within the bloodstream and still get a large response?

B) lipophobic

Functionally, G proteins are classified into what three types?

B) those that affect ion channels, stimulatory G proteins, and inhibitory G proteins

When the alpha subunit of the G protein is activated, it can stimulate ion channels to do what?

A) either open or close

The enzyme that catalyzes synthesis of cAMP is called ________ and is activated by ________.

A) adenylate cyclase : a Gs protein

What enzyme is activated by cAMP?

D) protein kinase A

In order to terminate a cAMP-mediated response, the enzyme ________ can be activated to degrade cAMP.

D) cAMP phosphodiesterase

When associated with G protein, guanylate cyclase will activate what enzyme?

B) protein kinase G

What molecule, whose synthesis is catalyzed by phospholipase C, triggers the release of calcium from the endoplasmic reticulum?

A) inositol triphosphate

Which of the following proteins is directly activated by a G protein?

B) adenylate cyclase

Which of the following are second messengers?

E) cAMP, calcium, and inositol triphosphate

What two systems primarily control homeostasis due to their ability to communicate over long distances?

A) nervous and endocrine

The chemical messenger of the nervous system is ________ and chemical messenger of the endocrine system is ________.

E) neurotransmitter : hormone

The target cells of the nervous system are

C) neurons, muscles, or glands.

The nervous system communicates via the ________ and the endocrine system communicates via the ________.

C) synapse : bloodstream

Which of the following statements is true for the nervous system but NOT the endocrine system?

C) There is a special anatomical arrangement between the secretory cell and the target cell.

What part of a neuron releases neurotransmitter by exocytosis?

D) axon terminal

What chemical messenger diffuses to neighboring cells to exert an effect?

A) paracrine

What chemical messenger is released from endocrine glands into the bloodstream?

C) hormone

What chemical messenger is released by a presynaptic cell?

D) neurotransmitter

Which of the following enzymes catalyzes phosphorylation of a protein?

E) tyrosine kinase

Which of the following enzymes catalyzes synthesis and release of arachidonic acid?

D) phospholipase A2

Which of the following enzymes catalyzes synthesis of epinephrine from norepinephrine?

E) phenylethanolamine N-methyl transferase

Which of the following enzymes catalyzes synthesis of cAMP?

C) adenylate cyclase

Which of the following enzymes catalyzes synthesis of prostaglandins and thromboxanes?

E) cyclooxygenase

Which of the following enzymes catalyzes dephosphorylation of a protein?

B) phosphoprotein phosphatase

Which of the following enzymes catalyzes synthesis of diacylglycerol and inositol triphosphate?

C) phospholipase C

A target cell will respond to a chemical messenger once that molecule has bound to a

A) receptor.

A(n) ________ is transported in the bloodstream.

A) hormone

Histamine is an example of a(n)

C) paracrine.

Lipid-soluble molecules are not only hydrophobic, but are also

B) lipophilic.

Catecholamines, such as dopamine, norepinephrine, and epinephrine, are derived from the amino acid

B) tyrosine.

Identify the two enzymes involved in converting tyrosine into dopamine.

C) tyrosine β hydroxylase and dopa decarboxylase

Eicosanoids are derived from what phospholipid?

E) arachidonic acid

Steroid messengers are derived from what precursor molecule?

B) cholesterol

Catecholamines are released from the secretory cell by

B) exocytosis.

Steroids are released from the secretory cell by

C) simple diffusion.

What protein in the blood that is relatively non-specific with respect to its ability to bind and transport chemical messengers in the blood?

A) albumin

As free hormones bind to their receptors and no more hormone is released from their cell of origin, the concentration of hormone bound to carrier proteins will

B) decrease.

The strength with which a ligand (chemical messenger) will bind with a receptor is referred to as its

A) affinity.

As the concentration of receptors on the cell membrane decreases, the response of the target cell will

B) decrease.

Which of the following chemical messengers are lipophilic?

E) steroids, eicosanoids, and thyroid hormone

Which of the following chemical messengers are lipophobic?

A) amino acids