ANS Pharmacology - transmitters and receptors

What does the somatic nervous system control

Voluntary movement via skeletal muscle

What does the autonomic nervous system control

Involuntary organ function via smooth muscle, cardiac muscle, and glands

How many neurons are in the somatic pathway

Single neuron from CNS to muscle

How many neurons are in the autonomic pathway

Two neurons: preganglionic and postganglionic

What are the divisions of the autonomic nervous system

Sympathetic, parasympathetic, enteric

What is the role of the ANS

Regulates blood pressure, digestion, urination, thermoregulation, and more

Where is heart rate integrated in the CNS

Brain

Where is urination integrated in the CNS

Spinal cord

What does the afferent branch of the ANS do

Sends sensory info from periphery to CNS

What does the efferent branch of the ANS do

Sends motor signals from CNS to organs

What is the baroreceptor reflex

Drop in BP → baroreceptors signal brain → increase HR and resistance → restore BP

What is the sympathetic system’s role

Fight or flight response, diffuse activation (adrenergic)

What is the parasympathetic system’s role

Rest and digest, localized control (cholinergic)

Why is the sympathetic response massive

One preganglionic neuron activates many postganglionic neurons + adrenal medulla release

Why is the parasympathetic response subtle

One preganglionic neuron activates few postganglionic neurons, no adrenal involvement

What does sympathetic stimulation do to the pupil

Dilates via radial muscle contraction

What does parasympathetic stimulation do to the pupil

Constricts via sphincter muscle contraction

What does sympathetic stimulation do to bronchioles

Dilates

What does parasympathetic stimulation do to bronchioles

Constricts and increases secretions

What does sympathetic stimulation do to the bladder

Relaxes detrusor, contracts sphincter

What does parasympathetic stimulation do to the bladder

Contracts detrusor, relaxes sphincter

What does sympathetic stimulation do to male genitalia

Ejaculation

What does parasympathetic stimulation do to male genitalia

Erection

What does sympathetic stimulation do to salivary glands

Thick, viscous secretion

What does parasympathetic stimulation do to salivary glands

Copious, watery secretion

What does sympathetic stimulation do to the heart

Increases rate and contractility

What does parasympathetic stimulation do to the heart

Decreases rate and contractility

What does sympathetic stimulation do to GI tract

Decreases motility and contracts sphincters

What does parasympathetic stimulation do to GI tract

Increases motility and tone

What does sympathetic stimulation do to the kidney

Secretion of renin (beta1 increases; alpha1 decreases) 

Which organs have dual innervation

Eyes, heart, liver, lungs, digestive system, bladder

Which organs have sympathetic-only innervation

Sweat glands, arterioles, veins

What neurotransmitter is used in somatic motor neurons

Acetylcholine (ACh)

What neurotransmitters are used in the ANS

ACh (preganglionic), NE or ACh (postganglionic)

What enzyme synthesizes ACh

Choline acetyltransferase (ChAT)

What enzyme degrades ACh

Acetylcholinesterase (AChE)

What enzyme degrades NE

COMT in synapse, MAO in neuron

What transporter reuptakes NE

NET (norepinephrine transporter)

What are the cholinergic receptors

Nicotinic (NN, NM) and muscarinic (M1–M5)

Where are NM receptors located

Skeletal neuromuscular junction

Where are NN receptors located

Autonomic ganglia and adrenal medulla

Where are M1 receptors located

Sympathetic post-ganglionic; some pre-synaptic, lungs

Where are M2 receptors located

Myocardium, smooth muscle, some pre-synaptic sites, lungs

Where are M3 receptors located

Lungs, bladder, glands

What are the adrenergic receptors

Alpha (α1, α2) and beta (β1, β2, β3)

Where are α1 receptors located

Arteries, prostate, urethra

Where are α2 receptors located

CNS sympathetic pathways

Where are β1 receptors located

Heart muscle

Where are β2 receptors located

Lungs, heart

Where are β3 receptors located

Fat cells, bladder (detrusor)

What type of receptor is nicotinic

Ligand-gated ion channel

What type of receptor is muscarinic

G-protein coupled receptor (GPCR)

What type of receptor is adrenergic

G-protein coupled receptor (GPCR)

What does M2 activation do in the heart

Decreases heart rate and contractility

What does M3 activation do in the lungs and bladder

Bronchoconstriction, bladder contraction

What does M3 activation do in glands

Increases secretion

What does α1 activation do

Vasoconstriction, pupil dilation

What does α2 activation do

Inhibits NE release

What does β1 activation do

Increases heart rate and contractility

What does β2 activation do

Bronchodilation, vasodilation

What does β3 activation do

Relaxes bladder

What does sympathetic stimulation do to the pancreas

Inhibits insulin secretion

What does parasympathetic stimulation do to the pancreas

Stimulates insulin secretion

What does sympathetic stimulation do to salivary glands

Small volume secretion

What does parasympathetic stimulation do to salivary glands

Large volume secretion with enzymes

What does sympathetic stimulation do to sweat glands

Stimulates secretion

What does parasympathetic stimulation do to sweat glands

No innervation

What does sympathetic stimulation do to digestive glands

Inhibits secretion

What does parasympathetic stimulation do to digestive glands

Stimulates secretion