Chapter 16, Problem 7CT

Summary Introduction

Case Summary:

A drug is known to decrease heart rate even after cutting T1-T4 white rami. After cutting the vagus nerve, the drug no longer affects the heart rate. It affects the preganglionic and postganglionic neurons. The effect of the drugs is either inhibitory or excitatory.

Adequate Information:

The Autonomic Nervous System (ANS) controls the unconscious movement of the body. It has two important divisions’ sympathetic and parasympathetic divisions. They are present on the preganglionic neuron of the CNS and autonomic ganglia of the PNS. The sympathetic axons travel through the sympathetic chain ganglia to their target cell. The parasympathetic axons travel from cranial and sacral nerves to the target tissue. These branches of nerves either supply the organ or join nerve plexus.

To determine:

The drugs affect the ANS division. The effect caused by the drugs on the synapse between preganglionic and postganglionic neurons. The drug effect is inhibitory or exhibitory.

Given Information:

The parasympathetic division of the brainstem of medulla oblongata controls the effect of the drugs and get excited. By cutting the vagus nerve the effect of the drug get eliminated because it is no longer acting between the preganglionic and postganglionic synapses