Effects of Aging on the Autonomic Nervous System (ANS)

Effects of Aging on the ANS

Preganglionic neurons of the ANS are derived from the embryonic neural tube as are somatic motor neurons. The ANS structures of the PNS are all derived from the neural crest along with all sensory neurons. These ANS structures include the adrenal medulla, the postganglionic neurons, and all autonomic ganglia. Neural crest cells migrate along axons as they grow to reach their ultimate locations. As ganglia form, they receive axons from CNS preganglionic neurons. They send their axons to synapse with their effector cells in peripheral areas of the body. This activity is based on the presence of nerve growth factor, controlled by many signaling chemicals that are similar to those that act in the CNS.

In childhood and young adulthood, impaired ANS functions are usually caused by injuries of the autonomic nerves or spinal cord. The effects of aging reduce the efficiency of ANS function. There are structural changes in certain preganglionic axon ter-minals. These terminals become clogged with neuro-filaments. Common symptoms of ANS dysfunction include constipation (because of reduced gastrointes-tinal tract motility) and both drying and infection of the eyes (because of a reduced ability to form tears). Other effects of aging include orthostatic hypotension, which is defined as low blood pressure after changes in position such as standing up quickly. This occurs because pressure receptors become less responsive to changes in blood pressure. The cardiovascular centers become less able to maintain healthy blood pressure. Most of these effects can be controlled by implement-ing changes in lifestyle or using artificial aids. Older adults are advised to change position slowly, to allow the sympathetic nervous system to adjust the blood pressure. Artificial tears are eye drops used to alleviate dry eyes and resultant conditions.