Organization of the Nervous System: Structure and Function

Organization of the Nervous System

The Nervous System

The nervous system is a complex network of neurons that conveys electrochemical information throughout the body. It is essential for sensation, movement, cognition, and regulation of bodily functions.

• Composed of the brain and spinal cord; acts as the main control center for the body.

• Peripheral Nervous System (PNS): Composed of all nerves outside the CNS; connects the CNS to limbs and organs.

Central Nervous System (CNS)	Peripheral Nervous System (PNS)
Composed of the brain and spinal cord Acts as the main control center Responsible for processing and integrating information	Composed of nerves outside the brain and spinal cord Connects CNS to the rest of the body Responsible for sensation and movement

Example

• The CNS includes the brain and spinal cord, which process information and coordinate responses.

• The PNS includes nerves that carry signals to and from the CNS, enabling movement and sensation.

Subdivisions of the Peripheral Nervous System

Somatic vs. Autonomic Nervous Systems

The peripheral nervous system is divided into two major subsystems: the somatic nervous system and the autonomic nervous system.

Somatic Nervous System	Autonomic Nervous System
Controls voluntary movement Primarily innervates skeletal muscles	Controls involuntary movement Primarily innervates glands, organs, and smooth muscle

Example

• Somatic: Moving your arm to pick up a book.

• Autonomic: Heart rate increases when you are frightened.

Subdivisions of the Autonomic Nervous System

Sympathetic vs. Parasympathetic Divisions

The autonomic nervous system is further divided into the sympathetic and parasympathetic divisions, which often have opposite effects on the same organs.

Sympathetic Division	Parasympathetic Division
Activated during stress or emergency ("fight or flight") Increases heart rate Dilates pupils Inhibits digestion	Activated during relaxation ("rest and digest") Decreases heart rate Constricts pupils Stimulates digestion

Example

• Sympathetic: Running from danger increases heart rate and energy availability.

• Parasympathetic: Resting after a meal slows heart rate and promotes digestion.

Summary Table: Divisions of the Nervous System

Nervous System	Central Nervous System	Peripheral Nervous System
Peripheral Nervous System	Somatic Nervous System (voluntary)	Autonomic Nervous System (involuntary)
	Sympathetic Division (fight or flight)	Parasympathetic Division (rest and digest)

Key Terms and Definitions

• Neuron: A nerve cell; the basic unit of the nervous system.

• Central Nervous System (CNS): The brain and spinal cord.

• Peripheral Nervous System (PNS): All nerves outside the CNS.

• Somatic Nervous System: Controls voluntary movements.

• Autonomic Nervous System: Controls involuntary functions.

• Sympathetic Division: Prepares the body for action.

• Parasympathetic Division: Promotes relaxation and recovery.

Formulas and Equations

• There are no mathematical formulas directly associated with the structure of the nervous system, but neural transmission can be described by the following:

$\text{Nerve Impulse Speed} = \frac{\text{Distance}}{\text{Time}}$

Additional info: The notes above expand on the basic structure and function of the nervous system, providing context and examples for each division and subdivision.