2.2 : Nervous System

The nervous system coordinates body functions through its complex network of nerve cells, enabling sensation and movement. It is divided into two primary parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS is composed of the brain and the spinal cord. The brain acts as the body's control center, processing sensory information and coordinating responses. The spinal cord functions as a major signaling pathway for the brain and the rest of the body.

Extending from the CNS, the PNS reaches the limbs and organs, facilitating communication to the farthest parts of the body. The PNS is branched into the somatic nervous system and the autonomic nervous system.

• The somatic nervous system includes sensory neurons, which convey information from sensory receptors to the CNS, and motor neurons, which relay signals from the CNS to muscles to move. This system allows voluntary control over skeletal muscles and mediates reflex actions.
• The autonomic nervous system monitors involuntary processes, such as breathing, heart rate, digestion, and glandular activity. It is further subdivided into the sympathetic and parasympathetic nervous systems.
• The sympathetic nervous system prepares the body to handle stressful situations through the "fight or flight" response. This involves increasing heart rate, redirecting blood flow to muscles, and releasing stored energy to enhance physical performance and alertness.
• Conversely, the parasympathetic nervous system supports "rest and digest" functions, promoting energy conservation and facilitating maintenance activities like digestion, reducing heart rate, and enabling recovery from stress.

The intricate interaction between the CNS and PNS allows for coordinating complex behaviors and maintaining homeostasis. This dynamic system ensures that the body can adapt to internal and external stimuli, maintaining overall health and functionality.