Week 1, Types of cell signaling

Question 1

Autocrine signaling

Answer 1

When the signaling molecule binds to the receptors on the same cell that they were secreted from

Question 2

What is an example of autocrine signaling?

Answer 2

The regulation of somatostatin secretion in the stomach

Question 3

What is the mode of action of somatostatin in the stomach ?

Answer 3

binds to SST2R receptors on parietal cells inhibiting adenylyl cyclase which decreases cAMP levels leading to a decrease in gastric acid secretion.

Question 4

What cell type secretes somatostatin?

Answer 4

D cells

Question 5

How is somatostatin levels regulated in the stomach?

Answer 5

Through autocrine regulation. Somatostatin binds to SST2R receptors on the D cells resulting in a negative feedback loop reducing secretion

Question 6

Paracrine signaling

Answer 6

Signaling molecules are secreted into extracellular space and bind to receptors on adjacent cells, but do not pass through the circulatory system.

Question 7

What is an example of paracrine signaling?

Answer 7

the action of histamine in the stomach

Question 8

What cell type secrets Histamine in the stomach?

Answer 8

enterochromaffin-like cells

Question 9

What is the mode of action of Histamine in the stomach ?

Answer 9

Histamine binds to H2 receptors on parietal cells, activating adenylyl cyclase, increasing cAMP.
An increase of cAMP increases the number of proton pumps which increases gastric acid secretion.

Question 10

endocrine signaling

Answer 10

signaling molecules are secreted by cells in secretory glands into circulatory system. The molecules travel through the body and eventually bind to receptors located on or in cells of a target organ or tissue.

Question 11

Hypophyseal portal system

Answer 11

involved in endocrine signaling. It is a system of blood vessels that connect the hypothalamus with the anterior pituitary

Question 12

Describe the Hypothalamic-pituitary-adrenal axis

Answer 12

Stress detected by Cerebral Cortex -> Hypothalamus releases CRH -> the Anterior Pituitary releases ACTH -> Adrenal cortex the secrete cortisol -> target tissue.

Question 13

What happens when cortisol levels are elevated ?

Answer 13

It exerts a negative feedback effect on CRH and ACTH

Question 14

What are the functions of cortisol

Answer 14

1) Stimulates gluconeogenesis in the liver
2) Protein breakdown and liberation of free fatty acids
3) Immune system suppression
4) Facilitated stress response
5) Maintains blood pressure

Question 15

What type of signaling is synaptic transmission?

Answer 15

paracrine

Question 16

Describe synaptic transmission

Answer 16

1) action pot. activates Ca2+ channels allowing for Ca2+ ions to flow into the cell.
2) Ca2+ binds to synaptic vesicles (containing neurotransmitters) and pushes them towards the synaptic cleft.
3) The vesicles fuse with the pre-synaptic membrane and release neurotransmitters into the synaptic cleft.
4) Neurotransmitters bind to the receptors on the postsynaptic neuron triggering response.

Question 17

define neurotransmitter

Answer 17

a chemical substance released from a neuron bringing about a transfer of an impulse to another neuron

Question 18

Why can some neuro transmitters also be hormones ?

Answer 18

it depends on the mode of release. Some can also be released by glands into the circulatory system making them hormones e.g. Adrenaline