Introduction to the Nervous System

**Lesson Overview**

This lesson focuses on the anatomy and physiology of the nervous system.
The goal is to provide foundational knowledge of its structure and
functions.

**Definition and Structure of the Nervous System**

The nervous system is the body’s communication network, often referred to
as its “electrical wiring.” It consists of the brain, spinal cord,
neurons, nerves, meninges, cerebrospinal fluid, and sensory receptors. It is
classified into two main parts: the central nervous system (CNS) and the
peripheral nervous system (PNS). The CNS includes the brain and spinal cord,
while the PNS encompasses all nerves outside these structures.

The nervous system’s primary role is to transmit signals throughout the
body. The fundamental unit is the neuron, a specialized cell that
communicates via electrical signals that turn into neurotransmitters. The
human brain contains roughly 100 billion neurons, forming complex networks that
enable interaction among various regions and facilitate messages to the
entire body.

**Functions of the Nervous System**

The nervous system serves several key functions including regulating bodily
processes like blood pressure and breathing. Its activities can be
categorized into three main functions: sensory, integration, and motor. The
sensory function gathers information and directs it to the CNS; integration
involves analyzing these signals at the brain and spinal cord; and motor
function entails relaying signals from the CNS to effect changes in body
movement.

By constantly communicating through nerves, the nervous system monitors
both internal bodily activities and external environments. This helps
maintain homeostasis, assessing safety and orchestrating responses ranging
from quick reactions to relaxation.

**The Peripheral Nervous System**

While the CNS is composed of the brain and spinal cord, the PNS connects
the CNS to the rest of the body. It includes 12 cranial nerves and 31 pairs
of spinal nerves along with ganglia. The PNS is further divided into the
somatic and autonomic nervous systems.

**Somatic and Autonomic Nervous Systems**

The somatic nervous system manages voluntary movements, such as arm
movement. In contrast, the autonomic nervous system (ANS) regulates
involuntary functions, including breathing, heart rate, and hormone release.
Understanding the ANS is crucial for exploring how practices like yoga can
mitigate chronic stress and enhance health.

The ANS is further split into the sympathetic and parasympathetic systems,
with only one being activated at any time. The sympathetic nervous system
initiates the body’s stress response, known as the Fight or Flight
Response, when faced with threats. Conversely, the parasympathetic nervous
system promotes the Relaxation Response and supports the Rest and Digest
state, ensuring that vital functions like immune response and digestion
operate optimally during calm periods.

For more information, visit [Ashtanga Tech: Anatomy Physiology – Nervous
System
Overview](https://ashtanga.tech/study-guide/anatomy-physiology/physiology/nervous-system/nervous-system-overview/).