BIO 360 - Exam 1 - End of Chapter 6 Review Questions

Question 1

What are the two routes for long-distance signal delivery in the body?

Answer 1

neurons and blood

Question 2

Which two body systems maintain homeostasis by monitoring and responding to changes in the environment?

Answer 2

nervous and endocrine systems

Question 3

What two types of physiological signals does the body use to send messages? Of these two types, which is available to all cells?

Answer 3

chemical (available to all cells) and electrical

Question 4

In a signal transduction pathway, the signal ligand, also called the first messenger, binds to a(n) ______, which activates and changes intracellular ______.

Answer 4

receptor, targets (effectors), or proteins

Question 5

The three main amplifier enzymes are (a) ______, which forms cAMP; (b) ______,which forms cGMP; and (c) ______, which converts a phospholipid from the cell’s membrane into two different second messenger molecules.

Answer 5

(a) adenylyl cyclase, (b) guanylyl cyclase, (c) phospholipase C

Question 6

An enzyme known as protein kinase adds the functional group ______ to its substrate, by transferring it from a(n) molecule.

Answer 6

phosphate, ATP

Question 7

Distinguish between central and peripheral receptors.

Answer 7

Central: located within the central nervous system. Peripheral: found outside the CNS

Question 8

Receptors for signal pathways may be found in the ______, ______, or ______ of the cell.

Answer 8

nucleus, cytosol, cell membrane

Question 9

Down-regulation results in a(n) ______ (increased or decreased?) number of receptors in response to a prolonged signal.

Answer 9

decreased

Question 10

List two ways a cell may decrease its response to a signal.

Answer 10

It may down-regulate receptor number or decrease receptor affinity for the substrate.

Question 11

In a negative feedback loop, the response moves the system in the ______(same/opposite) direction as the stimulus moves it.

Answer 11

opposite

Question 12

Explain the relationships of the terms in each of the following sets. Give a physiological example or location if applicable.
(a) gap junctions, connexins, connexon
(b) autocrine signal, paracrine signal
(c) cytokine, neurotransmitter, neurohormone, neuromodulator, hormone
(d) Receptor agonist, receptor antagonist, antagonistic control pathways
(e) transduction, amplification, cascade

Answer 12

(a) Gap junctions connect two cells using protein channels called connexons, made from connexin subunits.
(b) Paracrine signals act on nearby cells; autocrine signals act on the cell that secretes them.
(c) Cytokines are peptide autocrine and paracrine signals. Neurotransmitters, neuromodulators, and neurohormones are all chemicals secreted by neurons. Neurotransmitters act rapidly on nearby cells; neuromodulators act more slowly. Neurohormones and hormones are secreted into the blood for action on distant targets.
(d) Receptor agonists activate receptors just like the normal ligand; receptor antagonists also bind to the receptor but block its activation. Antagonistic pathways create responses that oppose each other.
(e) Transduction: A signal molecule transfers information from ECF to the cytoplasm. Cascade: a series of steps. Amplification: One signal molecule creates a larger signal.

Question 13

List and compare the four classes of membrane receptors for signal pathways. Give an example of each.

Answer 13

G protein-coupled receptors (adenylyl cyclase/cAMP-linked receptors).

Receptor enzymes (tyrosine kinase receptor);

Integrin receptors (platelet receptors);

Ligand-gated channels (ATP-gated K+ channel);

Question 14

Arrange the following terms in the order of a reflex and give an anatomical example of each step when applicable: input signal, integrating center, output signal, response, sensor, stimulus, target.

Answer 14

Stimulus to sensor (sensory receptor) to input signal (sensory nerve) to integrating center. Integrating center (the brain or an endocrine cell) sends an output signal (through nerve or hormone) to target cell (muscles and glands), which reacts to the stimulus with a response.

Question 15

Compare and contrast the advantages and disadvantages of neural versus endocrine control mechanisms.

Answer 15

Neural control is faster than endocrine and better for short-acting responses. Endocrine control can affect widely separated tissues with a single signal and better for long-acting responses.

Question 16

Would the following reflexes have positive or negative feedback?
(a) glucagon secretion in response to declining blood glucose
(b) increasing milk release and secretion in response to baby’s suckling
(c) urgency in emptying one’s urinary bladder
(d) sweating in response to rising body temperature

Answer 16

(a) negative, (b) positive, (c) negative, (d) negative

Question 17

Identify the target tissue or organ for each example in question 17.

Answer 17

(a) tissues that respond to glucagon, such as liver; (b) breast; (c) bladder; (d) sweat glands

Question 18

Now identify the integrating center for examples (a), (c), and (d) in question 17.

Answer 18

(a) pancreatic endocrine cells that secrete glucagon, (c) and (d) nervous system

Question 19

In each of the following situations, identify the components of the reflex.
(a) You are sitting quietly at your desk, studying, when you become aware of the bitterly cold winds blowing outside at 30 mph, and you begin to feel a little chilly. You start to turn up the thermostat, remember last month’s heating bill, and reach for an afghan to pull around you instead. Pretty soon you are toasty warm again.
(b) While you are strolling through the shopping district, the aroma of cinnamon sticky buns reaches you. You inhale appreciatively but remind yourself that you’re not hungry because you had lunch just an hour ago. You go about your business, but 20 minutes later you’re back at the bakery, sticky bun in hand, ravenously devouring its sweetness, saliva moistening your mouth.

Answer 19

(a) stimulus = decrease in body temperature to decrease, sensor = temperature receptors, input = sensory neurons, integrating center = brain, output = efferent neurons, targets = muscles used to pull up afghan, response = afghan conserves heat.

(b) stimulus = smell of sticky buns, sensor = odor receptors in the nose, input = sensory neurons, integrating center = brain, output = efferent neurons, target = skeletal muscles, response = walk to bakery, buy buns, and eat

Question 20

A researcher is studying the smooth muscle of the respiratory system airways. When she exposes the airways to the neurotransmitter acetylcholine, the smooth muscle contracts. When she exposes the airways to the neurohormone epinephrine, the airways relax.
(a) The phenomenon just described is an example of control.
(b) What distinguishes a neurotransmitter from a neurohormone?
(c) Which chemical messenger is secreted in higher concentrations: acetylcholine or epinephrine? Defend your answer.

Answer 20

(a) antagonistic.

(b) Neurotransmitters act on nearby cells (paracrine action). Neurohormones act on distant targets.

(c) Epinephrine is secreted in larger amounts because it will be diluted by the blood volume before reaching its target.

Question 21

In a signal cascade for rhodopsin, a photoreceptor molecule, one rhodopsin activates 1,000 molecules of transducin, the next molecule in the signal cascade. Each transducin activates one phosphodiesterase, and each phosphodiesterase converts 4,000 cGMP to GMP.
(a) What is the name of the phenomenon described in this paragraph?
(b) Activation of one rhodopsin will result in the production of how many GMP molecules?

Answer 21

(a) amplification and a cascade.
(b) (1000×4000) or 4,000,000 GMP.