NERVOUS SYSTEM IN HUMANS
The nervous system can be divided into two major regions: the central and peripheral nervous systems.
1. Central nervous system (consisting of brain and spinal cord), and
2. Peripheral nervous system (consisting of all the nerves of the body like cranial nerves, spinal nerves and visceral nerves).
The peripheral nervous system can be further divided into two parts:
1) Voluntary nervous system (which is under voluntary control from the brain)
- The somatic nervous system (SNS) is responsible for conscious perception and voluntary motor responses.
- Voluntary motor response means the contraction of skeletal muscle, but those contractions are not always voluntary in the sense that you have to want to perform them
- Some somatic motor responses are reflexes, and often happen without a conscious decision to perform them.
2) Autonomic nervous system (which operates automatically or involuntarily)
- The autonomic nervous system (ANS) is responsible for involuntary control of the body, usually for the sake of homeostasis (regulation of the internal environment).
- Sensory input for autonomic functions can be from sensory structures tuned to external or internal environmental stimuli.
- The motor output extends to smooth and cardiac muscle as well as glandular tissue.
- The role of the autonomic system is to regulate the organ systems of the body, which usually means to control homeostasis.
- Sweat glands, for example, are controlled by the autonomic system. When you are hot, sweating helps cool your body down.
- That is a homeostatic mechanism.