Question

In a frog, are the cholinergic receptors controlling heart rate of the same type as those controlling stroke volumes?

Answer 1

In frog the heart rate and stroke volume are controlled by cholinergic muscarinic receptors.

Nervous control of the heart of frog is primarily regulated by medulla of the brain, and the heart is innervated by both sympathetic and parasympathetic nerve fibers that terminate at the SA node. The neurotransmitters released by these nerves affect both heart rate and the strength of contraction , by influencing the timing and magnitude of ion currents across the cell membrane. The vagus nerves contain parasympathetic cholinergic neurons that release acetylcholine at their terminals. This neurotransmitter binds with muscarinic receptors and initiates effects.

pulmonary blood flow is achieved by a strong vagal cholinergic vasoconstriction of the pulmo-cutaneous artery that is extrinsic to the lung. Vasoconstriction in the pulmonary circuit reduces pulmonary blood flow and increases systemic recirculation of oxygen-poor blood from the right atrium, whereas decreased vagal tone on the pulmonary artery is associated with the increased pulmonary blood flow observed during lung ventilation.