Chapter 11: Fundamentals of the Nervous System and Nervous Tissue

Overview of the Nervous System

The nervous system is a complex network responsible for controlling and integrating all bodily activities. It is essential for communication within the body, allowing rapid responses to internal and external stimuli.

• Sensory Input: The process of gathering information from sensory receptors located throughout the body.

• Integration: The central nervous system (CNS) processes and interprets sensory input, determining the appropriate response.

• Motor Output: Activation of effector organs (muscles and glands) to produce a response.

Main Divisions of the Nervous System

The nervous system is divided into two major anatomical and functional regions:

• Central Nervous System (CNS):

  • Consists of the brain and spinal cord.

  • Acts as the integrating and control center for the body.

• Peripheral Nervous System (PNS):

  • Includes all neural structures outside the CNS (nerves and ganglia).

  • Connects the body to the CNS, facilitating communication between the CNS and the rest of the body.

Functional Organization of the Nervous System

The nervous system is further organized into functional divisions based on the direction of information flow and the type of control exerted.

• Sensory (Afferent) Division:

  • Transmits sensory input from receptors to the CNS.

  • Somatic sensory fibers: Carry signals from skin, skeletal muscles, and joints.

  • Visceral sensory fibers: Carry signals from organs within the ventral body cavity.

• Motor (Efferent) Division:

  • Transmits motor commands from the CNS to effector organs (muscles and glands).

  • Two main components:

    • Somatic Nervous System:

      • Voluntary control.

      • Conducts impulses to skeletal muscles.

    • Autonomic Nervous System (ANS):

      • Involuntary control.

      • Regulates smooth muscle, cardiac muscle, and glands.

      • Divided into:

        • Sympathetic division: Activates "fight or flight" responses.

        • Parasympathetic division: Promotes "rest and digest" activities.

    • Enteric Nervous System:

      • Neurons embedded in the walls of the gastrointestinal tract.

      • Helps regulate digestive function.

Nervous Tissue Cell Types

Nervous tissue is composed of two primary cell types, each with distinct functions:

• Neuroglia (Glial Cells):

  • Supporting cells of the nervous system.

  • Provide structural support, protection, and nourishment to neurons.

• Neurons:

  • Electrically excitable cells that transmit nerve impulses.

  • Responsible for communication and processing information within the nervous system.

Example: Organization of the Nervous System

Additional info: The Enteric Nervous System is sometimes considered a subdivision of the ANS, but it can function independently to regulate digestive processes.