Lecture 5

Nervous Tissue

Structure and Function of Nervous Tissue

Nervous tissue is the main component of the nervous system, which regulates and controls body functions. It consists of two major cell types: neurons and supporting (neuroglial) cells.

• Neurons: Specialized cells that transmit electrical impulses throughout the body. They have branching processes (dendrites and axons) extending from the cell body.

• Supporting Cells (Neuroglia): Non-excitable cells that support, protect, and insulate neurons.

• Location: Found in the brain, spinal cord, and peripheral nerves.

Key Functions:

• Transmit electrical signals from sensory receptors to effectors (muscles and glands).

• Integrate and process information.

• Maintain homeostasis and coordinate body activities.

Example: Neurons in the spinal cord relay pain signals from the skin to the brain.

Body Membranes

Types of Body Membranes: Cutaneous, Mucous, and Serous

Body membranes are sheets of tissue that cover body surfaces, line body cavities, and form protective barriers. They are composed of at least two primary tissue types: an epithelium bound to underlying connective tissue proper.

Cutaneous Membrane

• Structure: Also known as the skin; consists of two layers:

  • Epidermis: Keratinized stratified squamous epithelium.

  • Dermis: Thick layer of connective tissue.

• Function: Protects underlying tissues, prevents water loss, and provides sensory information.

• Characteristic: Dry membrane (unlike other body membranes).

Mucous Membrane

• Structure: Lines body cavities open to the exterior (e.g., digestive, respiratory, urinary, and reproductive tracts).

• Layers:

  • Epithelial sheet

  • Lamina propria: Loose connective tissue

• Function: Secretes mucus to lubricate and protect surfaces; may absorb or secrete substances.

• Characteristic: Wet membrane, bathed by secretions.

Serous Membrane

• Structure: Lines body cavities that are closed to the exterior (e.g., thoracic and abdominal cavities).

• Layers:

  • Mesothelium: Simple squamous epithelium

  • Thin areolar connective tissue

• Function: Secretes serous fluid to reduce friction between organs.

• Characteristic: Double-layered: parietal (lines cavity walls) and visceral (covers organs).

Membrane Type	Location	Structure	Function
Cutaneous	Skin (external body surface)	Keratinized stratified squamous epithelium + connective tissue	Protection, sensation, water loss prevention
Mucous	Body cavities open to exterior	Epithelial sheet + lamina propria	Secretion, absorption, protection
Serous	Closed body cavities (thoracic, abdominal)	Mesothelium + areolar connective tissue	Lubrication, reduces friction

Additional info: The cutaneous membrane is the only dry membrane, while mucous and serous membranes are moist due to their secretions.