Structure and Function of the Nervous System

Overview

• The nervous system enables humans to react to their surroundings and coordinate behavior.
• Composed of millions of neurons that use electrical impulses for rapid communication.
• Part of homeostasis and response in biology.

Control Systems

• Conditions in the body are controlled by chemical and nervous responses.
• Control systems include:
  • Receptors: Detect stimuli (changes in the environment such as light, heat, sound, etc.).
  • Coordination Center: Brain, spinal cord, or pancreas that processes information from receptors.
  • Effectors: Muscles or glands that bring responses to restore optimum levels (e.g., body temperature, blood glucose).

Neurons (Nerve Cells)

• Neurons carry electrical impulses and are adapted for this purpose.
• Types of Neurons:
  • Sensory Neurons: Carry signals from receptors to the CNS.
  • Motor Neurons: Carry signals from the CNS to effectors.
  • Relay Neurons: Connect sensory neurons to motor neurons.
• Features:
  • Long fibers (axons) insulated by a myelin sheath for faster transmission.
  • Dendrons and dendrites for receiving and sending signals.

Information Flow

• Information flows from receptors to effectors through the nervous system.
• The pathway: Stimulus -> Receptor -> Coordinator (CNS) -> Effector -> Response.

Receptors

• Specialized cells that detect stimuli and produce electrical impulses.
• Located in sense organs and respond to specific stimuli:
  • Skin: Touch, temperature, pain.
  • Tongue: Chemicals in food/drink.
  • Nose: Chemicals in the air.
  • Eye: Light.
  • Ear: Sound and head position.

Effectors

• Include muscles and glands that produce a specific response.
• Examples of responses:
  • Muscle contraction (e.g., moving an arm).
  • Saliva secretion from glands.
  • Hormone release into the bloodstream.

Additional Resources

• For more detailed study, refer to topics on Reflex Arc, The Brain, and The Eye.

Related Topics

• Coordination and control in the human endocrine system.
• Hormones in human reproduction.
• Homeostasis in humans.
• Plant hormones.

This guide is part of the AQA GCSE Biology curriculum and can help in understanding the role of the nervous system in maintaining homeostasis and responding to environmental changes.