Functions of the Nervous System

Overview

• The nervous system is the master control and communication center of the body.
• Communicates via electrical and chemical signals which are rapid and specific.
  • Electrical signals can travel up to 300 feet per second.
• Causes immediate responses due to rapid signal transmission.

Three Overlapping Functions

1. Sensory Input

   • Information is sent from receptors (e.g., photoreceptors in the retina) to the brain.
   • Example: Photoreceptors collecting light data.

2. Integration and Processing

   • The brain processes and interprets sensory data.
   • Example: Interpreting visual information as a glass of water.

3. Motor Output (Efferent Output)

   • Decisions based on integration lead to actions.
   • Example: Stimulating muscles to raise a glass and drink water.

Structural Divisions of the Nervous System

1. Central Nervous System (CNS)

   • Consists of the brain and spinal cord.
   • Located in the dorsal body cavity.
   • Functions as the integration and control center.
   • Processes sensory input to dictate motor output.

2. Peripheral Nervous System (PNS)

   • Consists of nerves outside the CNS.
   • Includes spinal nerves (from the spinal cord) and cranial nerves (from the brain).
   • Communicates motor and sensory information between the body and CNS.

Functional Divisions of the Nervous System

1. Sensory (Afferent) Division

   • Inputs information to the CNS.
   • Consists of:
     • Somatic Sensory Fibers: Relay data from skin, muscles, joints.
     • Visceral Sensory Fibers: Convey information from organs.

2. Motor (Efferent) Division

   • Transmits impulses from CNS to effector organs (muscles and glands).
   • Includes:
     • Somatic Nervous System: Controls skeletal muscle (voluntary control).
     • Autonomic Nervous System (ANS): Regulates involuntary activities (e.g., cardiac and smooth muscle).

Autonomic Nervous System (ANS)

• Sympathetic Division

  • Activates the "fight or flight" response.
  • Mobilizes body systems during activity.

• Parasympathetic Division

  • Manages "rest and digest" functions.
  • Promotes energy conservation and housekeeping activities.

• Both divisions work antagonistically to maintain homeostasis, impacting the same organs (e.g., heart rate regulation).

Summary

• The CNS acts as the processing center for sensory input and dictates motor output.
• The PNS links the CNS with the body, carrying information to and from.
• Functional divisions (sensory and motor) are crucial for understanding the direction and origin of information.
• The ANS, particularly its sympathetic and parasympathetic branches, is vital for maintaining internal balance through involuntary control.