The Parasympathetic nervous system

The Autonomic Nervous system

The ANS is the part of the nervous system that regulates the activity of:

1. Visceral and vascular smooth muscles

2. Glandular secretions

3. Heart beat and force of contraction of the heart

4. It is regulated by centers in the brain

The ANS consists of two divisions: The sympathetic system & The parasympathetic system

They have opposing actions in some situations.

Many organs receive neurons from both the sympathetic and the parasympathetic system.

The Parasympathetic System (Cholinergic System)

The parasympathetic system is also called cholinergic system because when it is activated all parasympathetic nerves release Acetylcholine (ACh)… Cholinergic

ACh then reacts with its receptors, known as muscarinic receptors found on all visceral tissues to produce biological responses.

The gastrointestinal Tract (GI tract)

The GI tract is innervated by both the sympathetic and parasympathetic nerves to regulate its functions:

1. Activation of the parasympathetic system in the GI tract leads to contraction of GI smooth muscles and increased gastric acid secretions

2. Inhibition of the parasympathetic system in the GI tract (by drugs that block ACh access to its receptors) causes reduced GI motility and secretion

Therefore, drugs that enhance/ antagonize the effect of ACh can alter GI functions.