Answer
The so-called autonomic nervous system (ANS) is not completely autonomous but is subject to monitoring and adjustment of its activities by inputs from various parts of the central nervous system(CNS)
Research has sown that the following areas of the CNS influence the functions of the ANS:
1. Spinal cord
2. Brain stem
3.Hypthalamus
4.Cortical centers ( frontal lobe)
Although the hypothalamus serves as an important integration centers of impulses going to and from the ANS , it is believed that the reticular formation of the direct "hands on" manager of the activities of the autonomic nervous system.
Work Step by Step
The hypothalamus which is the "boss" or senior supervisor of autonomic nervous system activities issues orders to a floor manager which is the reticular formation (RF) of the brain stem. The RF has the most direct supervisory influence on the functions of the ANS.
The anterior hypothalamus controls parasympathetic activities and the posterior hypothalamus controls sympathetic activities, The hypothalamus can have direct effects on the ANS, but mainly it manages by issuing orders to the reticular formation from where they go to preganglionic neurons in the spinal cord and brain stem.
The Reticular formation ARF and DRF) is a group of connected nuclei in different parts of the brain stem: in the mid- brain--the dorsal tegmental; in the pons, the central tegmental; in the medulla , the central, and the inferior medullary.
In the ventrolateral medulla there is a cardiac center that monitors heart rate, and there is a vasomotor center that monitors ANS control of vasodilation. Pupil dilation and focusing of eye lens are under supervision of oculomotor nuclei in the midbrain.
The autonomic nervous system is also subject to some degree of subconscious cortical control, as well as to conscious inhibition of certain reflex activities( urination and defecation reflexes)
