Question

ANS

A) Compare the two branches of the autonomic nervous system in terms of neurotransmitters and receptors.

​B) How can the same neurotransmitter cause different responses? Be specific as possible and compare the lungs bronchial muscles with the heart response to epinephrine in terms of their receptor types and second messenger respones.

Answer 1

A.SYMPATHETIC SYSTEM - adrenoreceptors(alpha & beta)

Presynaptic membrane have Acetylcholine neurotransmittor, whereas in post synaptic membrane have Norepinephrine (Except in Adrenal medulla - epinephrine)

PARASYMPATHETIC SYSTEM - cholinoreceptors (Muscuranic (M) and Nicotinic (N)receptors)

Presynaptic membrane and postsynaptic membrane have same neurotransmittor - Acetylcholine.

B.Sympathetic action in the lung

Preganglionic neurons impulse conduction to the axonal terminal causes release of the acetyl choline into synapse 1 (T1&T4 sympathetic ganglia). Acetyl choline binds with the Nicotinic cholinergic receptors and contineus to the sympathetic post ganglionic neuron  to the axonal terminal to release the Norepinephrine into synapse 2.Norepinephrine binds to the beta adrenergic receptors on the lung muscle to relax resulting in bronchodilation, to increase the airway.The increased oxygen by bronchodilation will be supplied to those organ cells that are capable of rapidly resisting the stress.

Parasympathetic action in the lung

Preganglionic neurons impulse conduction to the axonal terminal causes release of the acetyl choline into synapse 1 (intramural ganglia). Acetyl choline binds with the Nicotinic cholinergic receptors and contineus to the sympathetic post ganglionic neuron  to the axonal terminal to release the Acetyl choline in the Synapse 2 and binds to the cholinergic receptors on the lung on the Muscarinic receptors causing constriction of smooth muscle and increases the mucosal secretion.

SYMPATHETIC ACTION IN THE HEART

Preganglionic neurons impulse conduction to the axonal terminal causes release of the acetyl choline into synapse 1 (T1&T4 sympathetic ganglia).Acetyl choline binds with the Nicotinic cholinergic receptors and contineus to the sympathetic post ganglionic neuron  to the axonal terminal to release the Norepinephrine into synapse 2(SA & AV nodes).Norepinephrine binds to the beta adrenergic receptors on the heart.This results in increase in the heart rate,cardiac contractility,automaticity,and conduction velocity.Thus cardiac output is increased.

Parasympathetic action in the HEART.

Preganglionic neurons impulse conduction to the axonal terminal causes release of the acetyl choline into synapse 1 (intramural ganglia). Acetyl choline binds with the Nicotinic cholinergic receptors and contineus to the sympathetic post ganglionic neuron  to the axonal terminal to release the Acetyl choline in the Synapse 2 (SA & AV Node) and binds to the cholinergic receptors on the heart,on the Muscarinic receptors causing decreasing the heart rate,contractility,automaticity,and the conduction velocity. Thus reducing the cardiac output.