Cell physiology: Autonomic synapses

Question 1

For the Somatic Nervous Division, name the neurotransmitter and receptor type.

Answer 1

ACh / nicotinic ACh receptor (nAChR) which is an Ion channel

Question 2

For the Sympathetic Nervous Division, name the neurotransmitter and receptor type.

Answer 2

Preganglionic NT / Receptor: ACh / nicotinic ACh receptor (nAChR) which is an Ion channel

Postganglionic NT / Receptor: Norepinephrine / adrenergic receptor which is a GPCR

Question 3

For the Parasympathetic Nervous Division, name the neurotransmitter and receptor type.

Answer 3

Preganglionic NT / Receptor: ACh / nicotinic ACh receptor (nAChR) which is an Ion channel

Postganglionic NT / Receptor: ACh / muscarinic receptor which is a GPCR

Question 4

Name the location and G-protein α-subunit for α1 and α2. What does it promote?

Answer 4

Adrenergic receptor: α1 Location: smooth muscle G-protein α-subunit: Gαq (smooth muscle contraction)Adrenergic receptor: α2 Location: presynaptic side of sympathetic G-protein α-subunit: Gαi (inhibits further NE release)

Question 5

Name the location and G-protein α-subunit for β1, β2 and β3

Answer 5

All β are Gαs subunits!Adrenergic receptor: β1Location: heart, juxtaglomerular cells G-protein α-subunit: Gαs (promotes contraction)Adrenergic receptor: β2Location: smooth muscle G-protein α-subunit: Gαs (smooth muscle relaxation)Adrenergic receptor: β3Location: fat cells G-protein α-subunit: Gαs (lipid breakdown)Adrenergic receptor: β3Location: bladderG-protein α-subunit: Gαs (bladder relaxation)

Question 6

Compare nicotinic and muscarinic acetylcholine receptor activation

Answer 6

nAChRs are fast ligand-gated cation channels opened directly by binding of ACh mAChRs are GPCRs

Question 7

Identify acetylcholine muscarinic receptor types and their effects on various target organs

Answer 7

Two primary types are M2 (Gαi) and M3 (Gαq)Effects: M2 (Gαi) Slows heart rate via activation of a K+ channel leading to hyperpolarization Effects: M3 (Gαq) 1. Contracts smooth muscle by increased intracellular Ca2+ 2. Stimulates glands to secrete 3. Elevates NO (nitric oxide) production in endothelial cells —> smooth muscle relaxation (vasodilation)

Question 8

Identify the role of ATP and nitric oxide in smooth muscle relaxation and blood vessel dilation.

Answer 8

ATP causes contraction of smooth muscle in arterioles and in the vas deferens. Triggered by Ca2+, NO stimulates guanylate cyclase increasing production of cGMP, causes relaxation of smooth muscle.

Question 9

Describe the baroreceptor reflex in response to high or low blood pressure

Answer 9

Baroreceptors are mechanoreceptors that detect changes in blood pressure and bring about short term mediation of blood pressure. Mediated by the ANS, they detect stretch when blood pressures is high. They are located in the carotid sinus and aortic arch.

Question 10

Define orthostatic hypotension and discuss how the baroreflex counters it in healthy patients

Answer 10

Orthostatic hypotension occurs when a person goes from lying down to standing which causes the blood to rush downward thus reducing blood flow to the heart and dropping arterial BP. Baroreflex counters this by initiating the sympathetic system and reducing the parasympathetic which constricts blood vessels and speeds up heart rate restoring homeostasis.