A&P 2nd ed 204 L01

Introduction to the Nervous System

  • Overview of the nervous system

    • Responsible for controlling perception and experience of the world

    • Directs voluntary movement

    • Seat of consciousness, personality, learning, and memory

    • Regulates aspects of homeostasis alongside the endocrine system:

      • Respiratory rate

      • Blood pressure

      • Body temperature

      • Sleep/wake cycle

      • Blood pH

Anatomical Divisions of the Nervous System

  • Central Nervous System (CNS)

    • Includes brain and spinal cord

      • Brain: contains billions of nerve cells (neurons); protected by skull.

      • Spinal cord: begins at foramen magnum and continues through the vertebral foramina to lumbar vertebrae; consists of millions of neurons.

  • Peripheral Nervous System (PNS)

    • Comprises all nerves outside the skull and vertebral column.

    • Nerves: axons of neurons bundled with blood vessels and connective tissue; they carry signals to and from CNS, classified by origin or destination:

      • Cranial nerves: 12 pairs relating to the brain

      • Spinal nerves: 31 pairs relating to the spinal cord.

Functional Divisions of the Nervous System

  • Functional categories: sensory, integrative, motor.

  • Sensory Division

    • Collects information about internal and external environments; carried by:

      • Somatic sensory division (special sensory): carries signals from muscles, bones, joints, and skin; includes senses of vision, hearing, taste, smell, and balance.

      • Visceral sensory division: transmits signals from internal organs (heart, lungs, stomach, kidneys, urinary bladder).

  • Integrative Functions

    • Analyze and interpret sensory information; determine appropriate responses.

      • 99% of sensory information is subconsciously disregarded as unimportant; remaining stimuli provoke motor responses.

  • Motor Division

    • Actions performed in response to integration, subdivided into:

      • Somatic motor division: voluntary control of skeletal muscles (also known as voluntary motor division).

      • Autonomic Nervous System (ANS): carries signals to thoracic and abdominal