Acetylcholine. Flashcards
What happens when we intravenously ACH at very low doses?
It binds to non-innervated muscarinic receptors on the walls of blood vessels and causes vasodilation.
What happens when ACH binds to non-innervated muscarinic receptors on the walls of blood vessels?
Calcium is released into the cell and this activates nitric oxide synthase.
NO-synthase converts arginine to NO.
NO diffuses into the smooth muscle walls of the blood vessels.
After ACH has bound to non-innervated muscarinic receptors on the walls of blood vessels, what happens after nitric oxide has diffused into the smooth muscle walls of the blood vessel?
NO activates an enzyme called guanylyl cyclase which converts GTP to cyclic gMP.
Cyclic GMP acts as a 2nd messenger and causes relaxation of the muscles and vasodilation.
Why are the effects of ACH in non-innervated muscarinic receptors on the walls of blood vessels only felt for a short amount of time?
As ACH is quickly broken down by acetylcholine esterase.
Also, baroceptors in the blood vessels sense the hypotension and induce tachycardia to correct it.
What happens if we inject a large quantity of ACH into the body?
We will get vasodilation over a large are of the body and this leads to a decrease in blood pressure.
How does ACH affect the heart?
It has negative effects on the heart leading to bradycardia and a decrease in cardiac output.
What kind of receptors in the heart lead to negative chronotropic effects?
Muscarinic receptors in the SA node.
What kind of receptors in the heart lead to negative dromotropic effects?
Muscarinic receptors in the AV node.
What kind of receptors in the heart lead to negative inotropic effects?
Muscarinic receptors in atrial muscles.
What are the pharmacological effects of ACH on smooth muscle?
Increased motility and secretions in smooth muscle in the GIT.
Increased contraction of the bladder and uterus.
Constriction of the muscle of the bronchiole.
What are the pharmacological effects of ACH on exocrine glands?
Increased secretion.
What are the pharmacological effects of ACH on the eye?
Reduction of miosis and reduction of intraocular pressure.
What is miosis of the eye?
Excessive constriction of the pupil.
Why does acetylcholine not have any major effects of the CNS?
As it is not very lipid soluble.
What is the effect of ACH on the adrenal medulla?
Increased release of epinephrine and norepinephrine.
