Reversal action of Ach on Blood prerssure

By Dr. Sameh AM Abdelghany

Chemical transmitters in PSNS

Acetylcholine(Ach):

Synthesis and storage:

• Choline + Acetyl CoA → Acetylcholine + CoA

Sites of release in ANS:

1. All autonomic ganglia.

2. All postganglionic parasympathetic fibers.

3. Postganganglionic sympathathetic fibers to sweat

glands.

4. Suprarenal medulla.

Fate:

• by cholinesterase (ChE) enzyme

Cholinergic receptors

Muscarnic receptors Nicotinic receptors

• Site - Effector organs supplied by

parasympathetic

- Sweat glands , Blood vessels

- CNS(Brain only)

- Autnominc ganglia (Nn)

- Adrenal medulla (Nn)

- Motor end plate(Nm)

- CNS spinal cord mainly (Nn)

• Subtypes M1, M2, M3, m4,m5 Nn , Nm

• Blockers Atropine - Ganglion blockers

- Neuromuscular blockers

Parasympathomimetics

Parasympathomimetics

Direct

Choline esters

e.g A.Ch

Alkaloids

e.g Pilocarp0ine

Indirect

Reversible

e.g Physostigmine

Irreversible

e.G Parathion

Muscarinic actions

Eye:-

Miosis due to stimulation of M receptors in constrictor

pupillea ms

Contract ciliary ms that leads to accommodation for near

vision

Secretions:

Increase salivary , bronchial , gastric acid and sweat

secretions

Respiratory system

Bronchospasm

Increase bronchial secretions

CVS:

Heart : ↓ all cardiac properties COP

Blood vessels: VD PR

Blood pressure: decrease BP(Hypotension)

due to:

i. Generalized VD of BV.

ii. ↓ COP

Reversal action of AcH on blood pressure:

Stimulation of M receptors in heart and blood vessels produce decrease in blood

pressure. After block of M eceptors by atropine, then nicotininc receptors stimulation

in sympathetic ganglia and adrenal medulla release endogenous catecholamines

which produce elevation in blood pressure

GIT:

Increase motility

Urinary tract:

Contract wall and relax sphincters

Nicotinic effects

At Neuromuscular junctions

muscle twitches

Stimulation of all autonomic ganglia

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