Nervous System Overview

Nervous System

The nervous system is responsible for controlling and coordinating all bodily functions, from movement to cognition. It consists of two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS).

Central Nervous System

The central nervous system includes the brain and spinal cord. It transmits signals between the body and the CNS, controlling voluntary actions like movement and speech, while also managing involuntary processes like breathing and heart rate regulation.

Brain

The human brain contains about 100 billion neurons, the basic unit of the nervous system. Each neuron has a cell body and special extensions called axons and dendrites. Dendrites receive incoming signals and transmit them to the cell body, while axons carry signals away from the cell body, allowing neurons to communicate over long distances.

Spinal Cord

The spinal cord extends from the lower part of the brain down through the spine. It is protected by the vertebrae of the spine and is surrounded by cerebrospinal fluid, which serves as a protective layer and helps maintain proper hydration levels.

Peripheral Nervous System

The peripheral nervous system encompasses nerves that branch off from the spinal cord and reach all parts of the body. It is divided into two parts: the somatic nervous system and the autonomic nervous system.

Somatic Nervous System

The somatic nervous system is responsible for voluntary actions, such as moving arms and legs in response to conscious thought. It involves receiving input from sensory organs and sending output to muscles.

Autonomic Nervous System

The autonomic nervous system manages involuntary functions, like heartbeat regulation and digestion. It is further divided into the sympathetic and parasympathetic systems. The sympathetic system triggers the 'fight or flight' response when the body needs to react quickly to a threat, while the parasympathetic system promotes relaxation and recovery.

Signal Transmission

Whenever a neuron sends a message to another neuron, it creates an electrical signal that travels down the axon. At the end of the axon, the electrical signal changes to a chemical one. The axon releases the chemical signal into the synapse—the space between the end of an axon and the tip of a dendrite from another neuron. The chemical signal then moves through the synapse to the neighboring dendrite, which converts it back into an electrical signal. This process allows for communication between neurons across long distances.

Non-Neuronal Cells (Glia)

In addition to neurons, there are non-neuronal cells called glia that play a crucial role in maintaining the overall health and function of the nervous system. Glial cells help support and hold neurons in place, protect them from damage, create insulation for nerve impulses using myelin, repair damaged neurons, trim out dead neurons, and regulate neurotransmitters.