Pharmacology: Autonomic Nervous System

Autonomic Nervous System target tissues

Smooth muscle, cardiac muscle, and glands.

Somatic Nervous System target tissues

Skeletal muscle.

ANS pathway

CNS to preganglionic neuron to ganglion to postganglionic neuron to target.

Number of neurons in standard autonomic pathways

Two neurons in series.

Sympathetic pathway to the adrenal medulla

CNS to preganglionic neuron to adrenal medulla to adrenaline into bloodstream.

Neurotransmitter released by all ANS preganglionic neurons

Acetylcholine (ACh).

nicotinic location

Autonomic ganglia, adrenal medulla, and skeletal muscle.

muscarinic location

cardiac muscle, smooth muscle, and glands.

Miosis

Pupil constriction.

Bradycardia

Decreased heart rate.

Muscarinic activation effect on bronchial smooth muscle

Bronchoconstriction.

alpha-receptors general effect

Smooth muscle contraction and excitation.

b-receptors main function

Smooth muscle relaxation and inhibition.

botulinum toxin

Inhibits the exocytotic release of acetylcholine.

cocaine

Blocks the reuptake of NA and dopamine.

amphetamines

Hijacks uptake mechanisms to promote neurotransmitter release.

pseudoephedrine

Promotes NA release to cause nasal vasoconstriction.

beta-blockers not with asthma

bronchoconstriction by blocking β receptors in the lungs.

adrenaline in anaphylaxis

a receptors - vasoconstriction

b receptors - bronchodilation

atropine (muscarinic antagonists)

mydriasis for retinal examination.

a drug could

synthesis

storage

release

Receptor activation

Receptor blockade

removal/breakdown

drug protein target

Enzymes, Transporters, Receptors, Ion channels

Cholinergic nerve terminal termination

action on ACH is terminated by AChE

Cholinergic nerve terminal pathway

Choline -> ACh -> Storage in synaptic vesicles -> Exocytosis ->ACh receptor -> Response

If AChE is inhibited:

ACh remains in synapse for longer --> more parasympathetic response

ACh release inhibited

ANS: decreased receptor activation and decreased response.

SNS: muscle weakness

alpha-adrenoceptors agonists

vasoconstriction, slowing gut, mydriasis

β-adrenoceptors agonists

force of heart contraction, slower GI movement, Bronchodilation

a-adrenoceptors antagonists

vasodilation, speeding gut, miosis

NA termination

reuptake