Autonoom zenuwstelsel

The autonomic nervous system, or ANS, is a network of motor neurons that regulates the activity of smooth muscles, cardiac muscles, and glands.

The ANS is divided into the sympathetic and parasympathetic divisions, which regulate opposing functions.

The sympathetic division prepares the body for an emergency fight or flight response. It elevates heart and metabolic rates and increases mental alertness. At the same time, it represses the activity of the digestive and urinary systems.

In contrast, the parasympathetic division plays a role in digestion and rest activities. It stimulates defecation and urination and decreases heart, metabolic, and respiratory rates. 

The ANS uses a two-neuron pathway to stimulate or inhibit its effectors.

The first neuron, known as the preganglionic neuron, originates in the brainstem or spinal cord. It is lightly myelinated and carries impulses from the CNS to the autonomic ganglion or the adrenal medulla, inside the adrenal gland.

The second neuron, the unmyelinated postganglionic neuron, originates in the autonomic ganglion and carries impulses to the effector muscle or gland.