General Principles of Cell Signaling

Question 1

Three types of Cell Signaling

Answer 1

• sharing info via gap junctions
• contact-dependent signaling
• signaling via secreted molecules

Question 2

Example of sharing info via gap junction

Answer 2

Glucagon receptors
-not uniformly distributed on liver cells
-connexins (=gap junctions) couple liver cells
Signal: cAMP (cyclic adenosine monophosphate)
Function: Synchronize the response to glucagon

Question 3

For gap junctions, each cell has one half-pore that makes a whole pore between the two cells when connected. What makes up a half-pore?

Answer 3

6 connexin molecules

Question 4

Example of Contact-dependent signaling

Answer 4

Leukocyte adhesion prior to transmigration n inflammation
Signal: Glycoproteins on leukocyte
Receptor: Adhesion proteins on endothelial cells
Function: Attract and guide leukocytes to a site of injury

Question 5

Sharing info by a gap junction requires the cells to be….

Answer 5

touching and connected

Question 6

In contact-dependent signaling, signaling and target cells are close together or far apart/

Answer 6

Close together

Question 7

Example of Signaling via secreted molecules

Answer 7

Signals: hormones, neurotransmitters (ex - epinephrine, acetylcholine, erythropoietin,etc.)

Receptors: alpha- and beta-adrenergic receptors, nAchR, mAchR, erythropoietin receptors,etc.

Function: constriction, relaxation, secretion, growth, etc.

Question 8

Endocrine

Answer 8

Signaling molecule is transported via the circulation

Question 9

Neuroendocrine

Answer 9

• similar to endocrine

- signaling cell is a neuron

Question 10

paracrine

Answer 10

• signaling molecule diffuse to nearby cell

- close by, but not identical cells (different cell types)

Question 11

neurotransmitter

Answer 11

• similar to paracrine

- signaling cell is a neuron

Question 12

autocrine

Answer 12

• similar to paracrine
• signaling cell is the target cell
• to cell of same type (or even the same cell that released the signal) -> like patting yourself on the back

Question 13

T/F: V1 and V2 are identical.

Answer 13

False.

They are similar, but not identical.

Question 14

Endocrine Signaling Example

Answer 14

Anti-diuretic homone (ADH) = Argenine-Vasopressin (AVP)

Signal: ADH/AVP

Receptors

• V1 vasopressin receptor on smooth muscle cells
• V2 vasopressin receptor on kidney collecting duct cells

Function
-Respond to low blood volume and high blood osmolarity w/ water retention and vasoconstriction

Question 15

When blood volume is low and blood osmolarity is high, what is the purpose of anti-diuretic hormone/ argenine-vasopressin?
Why is this important?

Answer 15

Purpose:

• kidneys =water retention
• blood vessels: vasoconstriction

Important: keeps blood pressure up and keeps brain oxygenated

Question 16

Where is ADH/AVP secreted?

Answer 16

From Posterior Pituitary

Question 17

Paracrine Signaling Example

Answer 17

Histamine-induced vasodilation via nitric oxide (NO)

Signal: Histamine and NO (both act paracrine)

Enzyme: Histamine receptors and guanylyl cyclase

Function: Vasodilation as part of an inflammatory response

Question 18

Neuronal signaling example

Answer 18

Neuromuscular Junction

Signal: Acetylcholine

Receptor: Nicotinic acetylcholine receptor

Function: Voluntary muscle contraction

Question 19

Synaptic Signaling

Answer 19

• signal reaches many cells

- low concentrations of signaling molecule are needed to activate the target

Question 20

Endocrine Signaling

Answer 20

• signal reaches only specific cells

- high concentrations of signaling molecule are needed to activate the target

Question 21

Signaling molecules are chemically very diverse and can include…

Answer 21

• proteins
• peptides
• fatty acid derivatives
• amino acids
• cholesterol derivatives
• small molecules
• dissolved gases
• ions

Question 22

Difference between water-soluble and lipid-soluble signaling molecules (=drugs)

Answer 22

water-soluble = reach receptors on outside of cell

lipid-soluble = reach receptors on inside of cell

Question 23

In regards to drugs, what does solubility define?

Answer 23

• the body space in which the drug is diluted

- the location of receptors that are reached

Question 24

Three Types of Target Molecules

Answer 24

Cell-surface receptors
Intracellular receptors
Intracellular enzymes

Question 25

Example of a Cell-surface receptor

Answer 25

ADH/AVP

signal: ADH/AVP

Receptors: V1 and V2 vasopressin

Function: Respond to low blood volume and high blood osmolarity with water retention and vasoconstriction

Question 26

Intracellular Receptor Example

Answer 26

Aldosterone control of plasma K+ concentration

Signal: aldosterone

Receptor: aldosterone receptor

Function:

• Respond to a high [K+] in plasma with K+ excretion via the collecting duct of the kidney
• increases Na+ and water retention

Question 27

Intracellular Enzyme Example

Answer 27

Vasodilation via nitric oxide (NO)

Signal: NO

Enzyme: Guanylyl cyclase

Function: Vasodilation as part of inflammatory response