GAP Chapter 11 Power Point 2025

Chapter 11: Functional Organization of Nervous Tissue

Introduction

  • Control Systems:

    • Endocrine: Uses chemical signals (hormones), involves glands and specialized cells.

    • Nervous: Comprises the brain, spinal cord, nerves, and sensory receptors; uses electrical (action potentials) and chemical signals (neurotransmitters).

Structure and Cell Types of Nervous Tissue

  • Main Cell Types:

    • Neurons: Primary functional units, responsible for transmitting information.

    • Glial Cells: Supportive cells with various functions, including maintenance, protection, and nourishment of neurons.

  • Nerve Structures:

    • Nerve: Bundle of axons outside the brain and spinal cord.

    • Cranial Nerves: 12 pairs originating from the brain.

    • Spinal Nerves: 31 pairs originating from the spinal cord.

    • Ganglion: Collection of neuron cell bodies outside the CNS.

    • Plexus: Extensive networks of axons in the PNS.

Functions of the Nervous System

  1. Maintaining Homeostasis: Regulates bodily functions by stimulating or inhibiting processes.

  2. Receiving Sensory Input: Monitors internal and external stimuli.

  3. Integrating Information: The brain and spinal cord process inputs and initiate responses.

  4. Controlling Muscles and Glands: Directs movements and physiological responses.

  5. Maintaining Mental Activities: Involves consciousness, thinking, memory, and emotion.

Divisions of the Nervous System

  • Anatomical Subdivisions:

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

    • Peripheral Nervous System (PNS): Includes sensory receptors and nerves; further divided into sensory and motor divisions.

  • Information Flow:

    • Sensory Input: Includes light, sound, taste, smell, touch, temperature, pain.

    • CNS: Processes sensory information.

    • Motor Output: Signals to effectors (muscles and glands).

Peripheral Nervous System (PNS)

  • Divisions:

    • Sensory (Afferent): Transmits impulses toward the CNS.

    • Motor (Efferent): Transmits impulses away from the CNS.

      • Somatic Nervous System: Controls voluntary movements (skeletal muscles).

      • Autonomic Nervous System: Controls involuntary functions (smooth and cardiac muscles, glands).

        • Sympathetic Division: Prepares the body for physical activity.

        • Parasympathetic Division: Regulates resting functions (e.g., digestion).

        • Enteric: Functions within the digestive tract.

Neuron Structure

  • Three Major Parts:

    • Cell Body (Soma): Contains the nucleus and organelles; responsible for metabolic functions.

    • Dendrites: Extensions that receive information; often branched.

    • Axon: Transmits impulses away from the cell body; ends at presynaptic terminals containing neurotransmitters.

Neuron Transport Mechanisms

  • Anterograde Movement: Moves materials from the cell body to the axon terminals for growth and repair.

  • Retrograde Movement: Transports materials back to the cell body, essential for recycling and repair (e.g., damaged organelles).

Neuron Types

  • Functional Classification:

    • Sensory Neurons (Afferent): Carry action potentials toward CNS.

    • Motor Neurons (Efferent): Carry action potentials away from CNS.

    • Interneurons: Connect neurons within the CNS.

  • Structural Classification:

    • Multipolar: Many dendrites; common in CNS.

    • Bipolar: One dendrite and one axon; found in sensory organs.

    • Pseudo-Unipolar: Single process that bifurcates; sensory receptors.

    • Anaxonic: Dendrites only; found in the brain and retina.

Glial Cells

  • Types:

    • CNS Glial Cells:

      • Astrocytes: Maintain blood-brain barrier and support neurons.

      • Ependymal Cells: Line ventricles; secrete cerebrospinal fluid.

      • Microglia: Immune defense; remove debris in CNS.

      • Oligodendrocytes: Form myelin sheaths around axons.

    • PNS Glial Cells:

      • Schwann Cells: Form myelin sheath around single axons.

      • Satellite Cells: Support and nourish neuron cell bodies in ganglia.

Myelinated vs. Unmyelinated Axons

  • Myelinated Axons:

    • Provide insulation, increase conduction speed, and aid in repair of axons.

    • Contain Nodes of Ranvier.

  • Unmyelinated Axons:

    • Rest in invaginations of Schwann cells or oligodendrocytes without being wrapped around, typically found in gray matter.

Organization of Nervous Tissue

  • Gray Matter: Contains unmyelinated axons, neuron cell bodies, dendrites, and glial cells; involved in processing and integration.

  • White Matter: Composed of myelinated axons; facilitates communication between different CNS regions.

    • In the brain, gray matter is found in the outer cortex and inner nuclei, while white matter is deeper.

    • In the spinal cord, white matter is on the outer part and gray matter is located centrally.