BIO 360 - Exam 1 - Chapter 6 Summary and Outline Questions

Question 1

Chapter 6 Summary Questions

Question 2

There are two basic types of physiological signals: ______ and ______. ______ signals are the basis for most communication within the body.

Answer 2

chemical and electrical / Chemical

Question 3

There are four methods of cell-to-cell communication:

Answer 3

(1) direct cytoplasmic transfer through gap junctions.
(2) contact-dependent signaling.
(3) local chemical communication.
(4) long-distance communication.

Question 4

______ ______ are protein channels that connect two adjacent cells. When they are open, chemical and electrical signals pass directly from one cell to the next.

Answer 4

Gap junctions

Question 5

______-______ ______ require direct contact between surface molecules of two cells.

Answer 5

Contact-dependent signals

Question 6

Local communication uses ______ signals, chemicals that act on cells close to the cell that secreted the paracrine.
A chemical that acts on the cell that secreted it is called an ______ signal.
The activity of ______ and ______ signal molecules is limited by ______ distance.

Answer 6

paracrine / autocrine / paracrine and autocrine / diffusion

Question 7

Long-distance communication uses ______ molecules and electrical signals in the nervous system.
Long-distance communication uses ______ in the endocrine system.
Only cells that possess receptors for a ______ will be target cells.

Answer 7

neurocrine / hormones / hormone

Question 8

______ are regulatory peptides that control cell development, differentiation, and the immune response. They serve as both local and long-distance signals.

Answer 8

Cytokines

Question 9

______ ______ ______ use membrane receptor proteins and intracellular second messenger molecules to translate signal information into an intracellular response.

Answer 9

Signal transduction pathways

Question 10

Some signal transduction pathways activate ______ ______. Others activate ______ ______ that create second messenger molecules.

Answer 10

protein kinases / amplifier enzyme

Question 11

Signal pathways create intracellular ______ that amplify the original signal.

Answer 11

cascades

Question 12

______-______ ______ channels open or close to create electrical signals.

Answer 12

Ligand-gated ion

Question 13

___ ______ linked to amplifier enzymes are the most prevalent signal transduction system. ___-______ coupled receptors also alter ion channels.

Answer 13

G proteins / G protein

Question 14

Calcium is an important signal molecule that binds to ______ to alter enzyme activity. It also binds to other cell proteins to alter movement and initiate exocytosis.

Answer 14

calmodulin

Question 15

Receptors come in related forms called ______. One ligand may have different effects when binding to different ______.

Answer 15

isoforms

Question 16

A receptor may have multiple ligands. Receptor ______ mimic the action of a signal molecule. Receptor ______ block the signal pathway.

Answer 16

agonists / antagonists

Question 17

Receptor proteins exhibit _______, ______, and ______.

Answer 17

specificity, competition, and saturation.

Question 18

Cells exposed to abnormally high concentrations of a signal for a sustained period of time attempt to bring their response back to normal through down-regulation or by desensitization.
In ______-______, the cell decreases the number of receptors.
In ______, the cell decreases the binding affinity of the receptors.
______-______ is the opposite of down-regulation and involves ______ the number of receptors for a signal.

Answer 18

down-regulation / desensitization / Up-regulation / increasing

Question 19

Cells have these two mechanisms for terminating signal pathways.

Answer 19

(1) removing the signal molecule
(2) breaking down the receptor-ligand complex.

Question 20

In ______ ______ pathways, an integrating center makes the decision to respond to a change.
A chemical or electrical signal to the target cell or tissue then initiates the response.
Long-distance reflex pathways involve the ______ and ______ ______ and ______.

Answer 20

reflex control / nervous and endocrine systems and cytokines.

Question 21

______ ______ is faster and more specific than ______ ______ but is usually of ______ duration. ______ control is less specific and slower to start but is longer lasting and is usually amplified.

Answer 21

Neural control / endocrine control / shorter / Endocrine

Question 22

Chapter 6 Outline Questions

Question 23

______ signals are changes in a cell’s membrane potential. ______ signals are molecules secreted by cells into the extracellular fluid. The cells that respond to ______ or ______ signals are called ______ cells.

Answer 23

Electrical / Chemical / target

Question 24

______ signals are responsible for most communication within the body. ______ signals act as ______ that bind to proteins to initiate a response.

Answer 24

Chemical / Chemical / ligands

Question 25

Cell adhesion molecules (CAMs) first known for their role in cell-to-cell adhesion, have now been shown to act as receptors in cell-to-cell signaling. CAMs are linked to the cytoskeleton or to intracellular enzymes. Through these linkages, CAMs transfer signals in both directions across cell membranes. Contact-dependent signaling is also known as juxtacrine signaling.

Question 26

A ______ signal is a chemical that acts on cells in the immediate vicinity of the cell that secreted the signal.
A ______ signal that acts on the cell that secreted it is called an ______ signal.
In some cases, a molecule may act as both an autocrine signal and a paracrine signal.
Paracrine and autocrine signal molecules reach their target cells by ___________________________________. Because distance is a limiting factor for ______, the effective range of paracrine signals is restricted to adjacent cells. A good example of a paracrine molecule is ______, a chemical released from damaged cells

Answer 26

paracrine / chemical / autocrine / diffusing through the interstitial fluid / diffusion / histamine

Question 27

The endocrine system communicates by using ______, chemical signals that are secreted into the blood and distributed all over the body by the circulation. ______ come in contact with most cells of the body, but only those cells with receptors for the hormone are target cells

Answer 27

hormones

Question 28

Chemicals secreted by neurons are called?

Answer 28

neurocrine molecules

Question 29

If a neurocrine molecule diffuses from the neuron across a narrow extracellular space to a target cell and has a rapid-onset effect, it is called a ______.
If a neurocrine acts more slowly as an autocrine or paracrine signal, it is called a ______.
If a neurocrine molecule diffuses into the blood for body-wide distribution, it is called a ______.

Answer 29

neurotransmitter / neuromodulator / neurohormone

Question 30

What is the role of cytokines?

Answer 30

• Associated primarily with immune responses, such as inflammation, but they also control cell development and cell differentiation.
• In development and differentiation, cytokines usually function as autocrine or paracrine signals.
• In stress and inflammation, some cytokines may act on relatively distant targets and may be transported through the circulation just as hormones are.

Question 31

A cell can respond to a particular chemical signal only if the cell has the appropriate ______ ______ to bind that signal.

Answer 31

receptor protein

Question 32

All signal pathways share the following features (Fig. 6.2):

Answer 32

(1) The signal molecule is a ligand that binds to a protein receptor.
(2) The ligand is also known as a first messenger because it brings information to the target cell.
(3) Ligand-receptor binding activates the receptor.
(4) The receptor in turn activates one or more intracellular signal molecules.
(5) The last signal molecule in the pathway creates a response by modifying existing proteins or initiating the synthesis of new proteins.

Question 33

______ signal molecules enter cells by ______ ______ through the phospholipid bilayer of the cell membrane. Once inside, they bind to ______ receptors or ______ receptors.

Answer 33

Lipophilic / simple diffusion / cytosolic / nuclear

Question 34

______ signal molecules are unable to enter cells by simple diffusion through the cell membrane. Instead, these signal molecules remain in the extracellular fluid and ______ ______ ______ ______ on the cell membrane.
In general, the response time for pathways ____________________________ is very rapid: responses can be seen within milliseconds to minutes.

Answer 34

Lipophobic / bind to receptor proteins / linked to membrane receptor proteins

Question 35

Concept Check
4. List four components of signal pathways.
5. Name three cellular locations of receptors.

Question 36

_______ _______ is the process by which an extracellular signal molecule activates a membrane receptor that in turn alters intracellular molecules to create a response.

Answer 36

Signal transduction

Question 37

A _______ is a device that converts a signal from one form into a different form. For example, the transducer in a radio converts radio waves into sound waves

Answer 37

transducer

Question 38

A signaling ______ starts when a stimulus (the signal molecule) converts inactive molecule A (the receptor) to an active form.

Active A then converts inactive molecule B into active B, active molecule B in turn converts inactive molecule C into active C, and so on, until at the final step a substrate is converted into a product. Many intracellular signal pathways are cascades. ______ ______ is an important example of an extracellular cascade.

Answer 38

cascade / Blood clotting

Question 39

G proteins get their name from the fact that they bind guanosine nucleotides[p. 34]. Inactive G proteins are bound to guanosine diphosphate (GDP). Exchanging the GDP for guanosine triphosphate (GTP) activates the G protein. When G proteins are activated, they either (1) open an ion channel in the membrane or (2) alter enzyme activity on the cytoplasmic side of the membran

Question 40

Figure 6.10 is a summary map of basic signal transduction, showing the general relationships among first messengers, membrane receptors, second messengers, and cell responses. The modified proteins that control cell responses can be broadly grouped into four categories:

metabolic enzymes
motor proteins for muscle contraction and cytoskeletal movement
proteins that regulate gene activity and protein synthesis
membrane transport and receptor proteins

Question 41

different ligand molecules with similar structures may be able to bind to the same receptor. A classic example of this principle involves two neurocrine molecules responsible for fight-or-flight responses: the neurotransmitter norepinephrine and its cousin the neurohormone epinephrine (also called adrenaline). Both molecules bind to a class of receptors called adrenergic receptors.

Question 42

A competing ligand that binds and elicits a response is known as an agonist of the primary ligand. Competing ligands that bind and block receptor activity are called antagonists of the primary ligand.

Question 43

The cellular response that follows activation of a receptor depends on which isoform of the receptor is involved. For example, the
and
receptors for epinephrine are isoforms of each other. When epinephrine binds to
on intestinal blood vessels, the vessels constrict (Fig. 6.14). When epinephrine binds to
on certain skeletal muscle blood vessels, the vessels dilate. The responses of the blood vessels depend on the receptor isoforms and their signal transduction pathways, not on epinephrine.

Question 44

Long-distance reflex pathways are traditionally considered to involve two control systems: the nervous system and the endocrine system. During stress and systemic inflammatory responses, cytokines work with the nervous and endocrine systems to integrate information from all over the body.