6 - Blood vessel order, function and specialisation of cells in the CNS Flashcards
What is the Tunica adventitia?
What is made up of?
What is its purpose?
- The external layer of the blood vessels
- contains fibrous tissue, elastin and collagen
- helps to keep the shape of the blood vessel
What is the Tunica media?
What is its made up of?
What is its purpose?
- middle layer of the blood vessel
- predominantly smooth muscle cells that allow the vessel to contract and relax
What is the Tinuca intima?
What is it made up of?
- the exchange surface
- predominantly vascular endothelium and includes the elastic basal lamina as well
What is the vascular endothelium?
a single layer of cells that acts as the blood-vessel interface
Give the 5 main vascular endothelium functions
- vascular tone management
- thrombostasis
- absorption and secretion
- barrier
- growth
What other 2 stimulators are there that will upregulate the endothelial NO?
shear stress
acetylcholine
What is arachidonic acid?
it is a precursor of lots of molecules
How are prostoglandins produced?
from arachidonic acid catalysed by COX enzymes
Where is COX1 produced?
In all cells
What is COX2 associated with?
inflammation and, hence, disease
What 2 vasoactive compounds can be produced from prostaglandins?
What are the enzymes involved in each?
What are the roles of the products?
- prostacyclin by prostacyclin synthase a vasodilator - thromboxane A2 by thromboxane synthase a powerful vasoconstrictor (which stimulates platelet aggregation)
Summary:
What 2 things can be produced from arachidonic acid?
prostoglandins or leukotrienes
Summary:
What 2 things are produced from prostaglandins?
prostocylin and thromboxane
Summary:
In what 2 ways is arachidonic acid produced?
- from phospholipids by Phospholipase A2
- from DAG via DAG lipase
Where does the production of arachidonic acid and the production or prostaglandins and leukotrienes take place?
inside the endothelial cells
Inside the nucleus, an endothelin precursor is produced and then cleaved by what enzyme to produce endothelin-1?
Endothelin Converting Enzyme
Where does endothelin-1 act on once it has been produced?
It is pushed out of the endothelial cells and binds to alpha and beta receptors on smooth muscle cells
NOTE: both receptors perform the same function in this context
What kind of effect does endothelin-1 have?
generally, it causes contraction
- if it binds to receptors on SM cells it causes contraction
- if it binds to receptors on endothelial cells, it causes relaxation
Where and when is rennin produced?
in the liver
in response to low BP (if renal perfusion decreases)
What overall effect does angiotensin II have?
Increases BP
Where is angiotensin II produced and where does it act on?
ACE is an enzyme on the endothelial cells
Angiotensin II binds to receptors on VSMCs
Describe the mechanism of action of angiotensin II
binds to an angiotensin receptor on VSMCs which leads to an activation of PLC—–> causing the conversion of PIP2 into IP3, resulting in contraction.
It also breaks down bradykinin, which normally stimulates vasodilation/relaxation
What effect does aspirin have on COX1 and COX 2?
COX1 - causes inactivation
COX2 - switches its function (to generating protective lipids)
Give a summary of the mechanisms of drug action of: NO production NO action prostacyclin action thromboxane action endothelin 1 action angiotensin II action
Gq protein linked receptor (PLC, PIP2, IP3, DAG) o Nitric Oxide production o Thromboxane action o Endothelin 1 action o Angiotensin II action
Guanylate Cyclase (GTP, cGMP, Protein Kinase G) o Nitric Oxide action
Adnylate Cyclase (ATP, cAMP, Protein Kinase A) o Prostacyclin action
