Surgery | Basic Science | Autonomic Nervous System part b

Autonomic Nervous System (ANS) B: Neurotransmitters and Pharmacology
Session Overview
Description
This session is part of the topic “Homeostasis”. It is concerned with the physiology and pharmacology of the neurotransmitters released by autonomic nerves.

Learning Objectives
By the end of this session you will be able to:

• Identify the location and the types of receptor for the neurotransmitter acetylcholine (ACh)
• Explain how the receptor types for catecholamines (adrenoceptors) are classified
• Outline some of the major routes by which drugs modify autonomic function

This session is part of the topic “Homeostasis”. It is concerned with the neurotransmitters in the autonomic nervous system (ANS) and the ways in which drugs targeting neurotransmission mechanisms can be used to modify autonomic function.

The two main neurotransmitters involved are acetylcholine (ACh) and noradrenaline.

Otto Loewi (Fig 1), a German, is credited with the discovery of ACh as a neurotransmitter in 1921. It was later shown to be a highly polar compound which cannot cross cell membranes. It can, however, bind to extracellular receptors.

The biosynthetic pathway for the catecholamines adrenaline and noradrenaline, both of which function as neurotransmitters, begins with the amino acid tyrosine. Alternative terminology is in use. Adrenaline is also known as epinephrine and noradrenaline as norepinephrine.