Eicosanoids, Melatonin, Histamine, Bradykinin, Serotonin (Physiology)

Question 1

What are eicosanoids?(2)

Answer 1

Lipid derived paracrine signals which regulate various physiological functions.

Question 2

What cleaves the eicosanoids and what is formed when they are cleaved?

Answer 2

They are cleaved by phospholipase A2, and they form arachidonic acid.

Question 3

Examples of eicosanoids

Answer 3

Thromboxanes, leukotrienes, prostaglandins

Question 4

What activates phospholipase A2?

Answer 4

Cell swelling and increased intracellular calcium.

Question 5

What stimulates phospholipase A2? (4)

Answer 5

Histamine, bradykinin, NA, Serotonin

Question 6

What inhibits phospholipase A2? (2)

Answer 6

Glucocorticoids
Adrenaline

Question 7

Explain the effects of COX-1.

Answer 7

When there is a physiologic stimulus, COX-1 is produced, which is constitutive.
It acts upon the stomach,kidneys, intestines, platelets and endothelium.
Causes the secretion of PGE2, TxA2, and PGI2, which performs physiologic functions.
Note: this pathway can be inhibited by NSAIDs.

Question 8

Explain the effects of COX-2.

Answer 8

There will be an inflammatory stimuli.
Stumulates the inducive COX2 to act upon the inflammatory sites.
Causes the production if inflammatory prostaglandins, proteases and reactive oxygen species, which causes inflammation.

Question 9

What are the functions of leukotrienes and PGF?

Answer 9

-Smooth muscle constriction
-Indirect vascular permeability-oedema
-Adhesion, chemotaxis
- Stimulates release of lysosomal enzymes, O2 radicals, insulin and histamine.

Question 10

Function of Thromboxane A

Answer 10

Clotting

Question 11

What are the functions of Prostaglandin E2?

Answer 11

Stimulates contraction of smooth muscle of gut and uterus.
Lipolysis, inhibits production of hormones.
Inhibits contraction of renal vasculature and bronchial muscles.

Question 12

What is responsible for:
A. Blood clotting
B. Bronchoconstriction
C. Regulation of circadian rhythm

Answer 12

A. Thromboxanes
B. Leukotrienes
C. Melatonin

Question 13

What are the functions of PGE2 and PGI2? (4)

Answer 13

-Demineralise bone
-Vasodilation
-pain
-Natriuresis and diuresis

Question 14

Which cells produces histamine?

Answer 14

Tissue mast cells
Basophils

Question 15

What stimulates the release of histamine?

Answer 15

Burns, inflammation, drugs, IgE.

Question 16

What inhibits release of histamine?

Answer 16

-PGE2, adrenalin, anti-histamines

Question 17

What are the effects of histamine in the body? (6)

Answer 17

Causes catecholamines release.
Causes increased secretion of HCL in stomach.
Increases cardiac contractility and rate.
Vasodilation of independent small blood vessels.
Contraction of smooth muscle of uterus, intestines and bronchi.
Increases capillary permeability (oedema).

Question 18

What are the effects of histamine and bradykinin? (6)

Answer 18

-Bronchospasm
-Oedema
-Abdominal cramps (histamine)
-Drop in blood pressure
-Pain
-Puritis

Question 19

What are the effects of serotonin in the body? (5)

Answer 19

-Causes smooth muscle contraction of small intestines, bronchi, uterus and blood vessels.
-Can also cause vasodilation.
-Platelets aggregation
-Pain
-Permeability of capillaries

Question 20

What are the consequences of serotonin?

Answer 20

-Oedema
-Bronchospasm, increased or decreased BP, diarrhoea.
-Pain
-Headaches