Chemical Signaling

Question 1

Chemical Signaling: Direct vs. Indirect

Answer 1

direct: via gap junctions
indirect: via chemical messengers

Question 2

When does a target cell respond to chemical messenger?

Answer 2

when the messenger binds to a receptor in or on the target cell.

Question 3

Define specificity.

Answer 3

a receptor binds to only specific chemical messengers

Question 4

Name the ways of controlling chemical signal secretion and how they work.

Answer 4

humoral: substance in ECF acts on a secretory cell
neural: a neuron acts on a secretory cell
hormonal: a hormone acts on a secretory cell

Question 5

How is a chemical response terminated?

Answer 5

enzymes catabolize ligands/chemical signals

Question 6

Name the patterns of chemical messenger secretion.

Answer 6

chronic/constant secretion
acute secretion
cyclic secretion

Question 7

Chronic/Constant Secretion

Answer 7

secretion is constant over time

example: thyroid hormones

Question 8

Acute Secretion

Answer 8

secretion rises and falls as needed

example: epinephrine (adrenaline)

Question 9

Cyclic Secretion

Answer 9

secretion rises and falls over time in a predictable manner

example: female reproductive hormones

Question 10

Functional vs Chemical Classifications of Chemical Messengers

Answer 10

functional: means by which messengers travel from secretory to target cell an/or types of responses
chemical: the chemical structure and solubility

Question 11

Neurotransmitters: What are they released by and how do they travel to the target cell?

Answer 11

• chemical messengers secreted by neurons

- travel through ECF a short distance to target cell

Question 12

What is the synaptic cleft?

Answer 12

it’s a space that separates pre- and post- synaptic cells

Question 13

Hormones: What are they released by and how do they travel to the target cell?

Answer 13

• chemical messengers released by endocrine organs

- travel to target via the circulation (travel much longer)

Question 14

Neurohormones: What are they released by and how do they travel to the target cell?

Answer 14

manufactured and released by neurons but travel via the circulation

Question 15

Paracrine and Autocrine: How do they travel to target cells and what type of target cell do they bind to?

Answer 15

travel short distances but may use circulation to travel

• paracrine: target cell is different as secretory cell (cytokine)
• autocrine: target cell is the same as secretory cell (thromboxane)

Question 16

Hydrophilic vs. Hydrophobic Messengers

Answer 16

hydrophilic: easily dissolve in water
- polar
- lipophobic

hydrophobic: do not easily dissolve in water and must be transported by carrier proteins
- non-polar
- lipophilic

Question 17

Steroids

Answer 17

• synthesized from cholesterol
• hydrophobic, lipophilic
  examples: testosterone, estrogen, cortisol, aldosterone

Question 18

Eicosanoids

Answer 18

• synthesized from arachidonic acid
• hydrophobic, lipophilic
  examples: prostaglandins

Question 19

Amino Acids

Answer 19

• building blocks of protein
• hydrophilic, lipophobic
  examples: glutamate, aspartate, gamma-aminobutyric acid

Question 20

Proteins and Peptides

Answer 20

• composed of chains of amino acids
• hydrophilic, lipophobic
  examples: parathyroid hormones

Question 21

Proteins vs. Peptides: How many amino acids in the chains they are consisted of?

Answer 21

proteins: consist of chains of at least 50 amino acids
peptides: consist of chains of less than 50 amino acids

Question 22

Amines

Answer 22

• derived from amino acids
• hydrophilic, lipophobic
  examples: epinephrine, serotonin, thyroid hormones (hydrophobic/lipophilic), histamine

Question 23

What determines the strength of a cellular response?

Answer 23

the number of receptors bound to messenger

Question 24

What factors influence the number of receptors activated?

Answer 24

1. messenger concentration
2. binding affinity
3. receptor density

Question 25

How does messenger concentration affect the strength of the cellular response?

Answer 25

by increasing the messenger concentration, the percentage of receptors bound increases

Question 26

Define Saturation

Answer 26

when 100% of receptors are bound

Question 27

What is binding affinity and how does it affect the strength of the cellular response?

Answer 27

it is the strength of binding to a certain chemical messenger. the higher the affinity, the greater percentage of receptors that will bind to the messenger.

Question 28

How does receptor density affect the strength of a cellular response?

Answer 28

As the density of receptors increases, the total number of receptors that can be bound for a given concentration of messenger increases

Question 29

Down-regulation vs. Up-regulation

Answer 29

down: decrease in receptors up: increase in receptors

Question 30

Name an example of a paracrine.

Answer 30

cytokines: chemical messengers used by the immune system

Question 31

Name an example of a autocrine.

Answer 31

thromboxane: released by platelets during hemostasis

Question 32

Define Antagonism.

Answer 32

different chemical signals producing opposing effects

Question 33

Define Synergism (Agonism).

Answer 33

different chemical signals producing the same effects

Question 34

Define Permissiveness.

Answer 34

one chemical signal acts on a cell causing a change in the ability of the cell to respond to a different chemical signal.

Question 35

Define Anatomic Antagonism/Synergism.

Answer 35

different chemical signals bind to the same type of receptor.

Question 36

Anatomic Antagonists vs. Anatomic Synergists

Answer 36

antagonists: blockers/inhibitors; compete for bonding to the same receptors and prevent their activation synergists: mimics; promotion of the action of the messenger by activating the same receptor.

Question 37

Physiologic Antagonism/Synergism

Answer 37

different chemical signals bind to different types of receptors

Question 38

Physiologic Antagonists vs. Physiological Synergists

Answer 38

antagonists: bind to different receptors on cells, producing opposing physiological reactions synergists: bind to different receptors on cells, producing the same physiological reactions