Extracellular Signalling - Basics

Question 1

What is remote signalling?

Answer 1

When cell secretes chemicals that signal to far away cells

Question 2

What are steps involved from signalling to cellular response?

Answer 2

1. Reception - reception of extracellular signal by cell through interaction with receptor
2. Transduction - transduction of signal from outside to inside of cell
3. Response - activation of cellular response

Question 3

What are 2 types of contact signalling?

Answer 3

Involves plasma membrane-bound molecules (juxtacrine –> requires close contact)

OR

Involves gap junctions

Question 4

What type of signalling is T-helper cell activation by APCs an example of?

Answer 4

Contact signalling

Question 5

What occurs during T-helper cell activation by APCs?

Answer 5

1. APCs display bits of bacteria on cell surface to see if an immune response is needed
2. T cells recognise these bits of pathogen

Question 6

What are gap junctions?

Answer 6

Directly join the cytoplasms of interacting cells, allowing the passage of chemical and electrical signals

Form when connexin proteins expressed by 2 adjacent cells form a channel that allows movement of cytoplasmic contents and allows rapid electrical coupling

Question 7

What type of signalling is a cardiomyocyte contraction an example of?

Answer 7

Contact signalling - adjacent myocytes coupled through connexin-43 gap junctions

Question 8

What is endocrine signalling?

Answer 8

Secreted into duct then enters blood stream for FAR AWAY target

Question 9

What is paracrine signalling?

Answer 9

Signalling molecule affects target cell CLOSE TO cell

Question 10

What is autocrine signalling?

Answer 10

Cell responds to molecule that it has produced ITSELF

Question 11

What is neuronal signalling?

Answer 11

Stimulus (nerve impulse) leads to electrical signal which is converted to chemical signal which affects another cell type

Question 12

What are hormones?

Answer 12

Chemical messengers released by a cell, gland, or organ that transport a signal from one cell to another

Question 13

Where are receptors located for hydrophilic (soluble) hormones?

Answer 13

On the cell membrane

Question 14

Where are receptors located for lipid-based hormones (hydrophobic and able to cross membrane)?

Answer 14

Inside cell

Question 15

What type of hormones are catecholamines?

Answer 15

Hydrophilic

Question 16

What are the catecholamines?

Answer 16

Adrenaline, noradrenaline, dopamine, serotonin, histamine

Question 17

What are the peptide hormones?

Answer 17

Insulin, glucagon, angiotensin II

Question 18

What type of hormones are peptide hormones?

Answer 18

Hydrophilic

Question 19

What are the steroid hormones?

Answer 19

Oestrogen, testosterone, cortisol, aldosterone

Question 20

What type of hormones are steroids?

Answer 20

Lipid-based (hydrophobic)

Question 21

What type of hormones are the thyroid hormones?

Answer 21

Lipid-based (hydrophobic)

Question 22

What type of hormones are the sterol hormones?

Answer 22

Lipid-based (hydrophobic)

Question 23

What are examples of 1st messengers of signalling molecules?

Answer 23

• Growth factors
• Neurotransmitters
• Hormones
• Cytokines

Question 24

How are hormones secreted during endocrine signalling?

Answer 24

Secreted directly into blood from endocrine glands

Question 25

How are hormones secreted during paracrine signalling?

Answer 25

Diffuse through interstitial tissues to target cells

Question 26

What are the steroid hormones?

Answer 26

Oestrogen, testosterone, cortisol, aldosterone

Question 27

The extracellular hormone signal has to be converted into an intracellular signal. How does this occur?

Answer 27

The signal has to be conveyed across the plasma membrane directly or indirectly. The specificity of hormonal action is achieved through interaction with its complementary receptor.