SCI10 Q3 MODULE3

Nervous System Overview

  • The nervous system is a complex network of nerves and cells.

  • It carries messages to and from the brain and spinal cord to various parts of the body.

  • Functions as the control center of the body and the storage center of information.

  • Responsible for coordinating all organ systems by sending messages via nerve signals to ensure efficient functioning.

Major Divisions and Parts of the Nervous System

I. Central Nervous System (CNS)

  • The CNS serves as the main processing center of the nervous system.

    • Components:

      • A. Brain

        • Organ located within the skull.

        • Functions as the organizer and distributor of information.

        • Parts of the Brain:

          1. Cerebrum - Large upper part controlling activity and thought.

          2. Cerebellum - Coordinates posture, balance, and movement.

          3. Brain Stem - Connects brain to spinal cord, controls automatic functions (breathing, digestion, heart rate, blood pressure).

      • B. Spinal Cord

        • Channel for signals between the brain and body parts.

        • Controls simple musculoskeletal reflexes without brain processing.

II. Peripheral Nervous System (PNS)

  • Connects the CNS to organs and limbs.

    • Divisions:

      • A. Somatic Nervous System

        • Voluntary control of body movements.

        • Parts:

          1. Spinal Nerves - Carry motor and sensory signals between spinal cord and body.

          2. Cranial Nerves - Carry information to and from the brain stem.

      • B. Autonomic Nervous System

        • Involuntary control of body movements.

        • Subdivisions:

          1. Sympathetic Nervous System - Activated during stress (increases heart rate, breathing, dilates pupils).

          2. Parasympathetic Nervous System - Restores body to a normal or relaxed state.

The Nerve Cell (Neuron)

  • The fundamental unit of the nervous system.

  • Billions of neurons present in the body.

  • Structure of Neuron:

    • Cell body contains the nucleus.

    • Dendrites - Carry impulses toward the cell body.

    • Axons - Carry impulses away from the cell body.

    • Synapse - The gap between neurons.

Regulation of Homeostasis by the Nervous System

  • The nervous system allows quick responses to maintain homeostasis.

  • Homeostasis regulates:

    • Body temperature

    • Blood pressure

    • pH levels

    • Glucose concentration

  • The nervous and endocrine systems work together in this regulation, referred to as neuroendocrine coordination.

  • Feedback mechanisms restore normal state after internal changes are detected by the brain.

    • The hypothalamus affects the pituitary gland to secrete hormones needed for restoration.

    • Hormones travel in blood and act on specific organs to maintain equilibrium.

  • Examples of processes monitored to achieve homeostasis include:

    • Body temperature

    • Water content in the body

    • Metabolic waste level in cells

    • Blood calcium level