How Senses Work: An Overview

Introduction

• Focus on vertebrates using human anatomy for examples.
• Sensory Receptor: Part of a sensory neuron or associated cell that receives information and relates it to the nervous system.
  • Activated by bending, squishing, chemicals, temperature, or light.
  • Responds to specific types of signals called stimuli.
• Pathway: Sensory reception → sensory receptor cell → neuron → brain.

Sensory Perception

• Classifications:
  • General Senses: Distributed throughout the body (e.g., touch/pressure).
  • Special Senses: Have specific organs (e.g., vision with eyes).
• Functionality:
  • Mechanical deformation, chemical, or light stimulus activates receptors.
  • Depolarization occurs in the sensory neuron if the stimulus reaches threshold potential, leading to an action potential.

Types of Sensory Receptors

1. Mechanoreceptors
   • Detect physical changes from mechanical force (e.g., skin pressure, ear hair cell movement).
2. Chemoreceptors
   • Detect chemicals in the body (e.g., blood oxygen and carbon dioxide levels).
3. Electromagnetic Receptors
   • Detect electromagnetic energy like light (e.g., photoreceptors in the retina).
4. Thermoreceptors
   • Detect temperature (e.g., warm or cold objects via skin).
5. Nociceptors (Pain Receptors)
   • Detect extreme temperature, pressure, or chemicals (e.g., too hot or painful pressure).

Sensory Adaptation

• When We Stop Feeling a Stimulus:
  1. When the stimulus stops being applied.
  2. Sensory Adaptation: Receptors stop responding over time even if the stimulus is present.
• Examples of Adaptation:
  • Forgetting feeling of clothing, clock ticking, radio noise.
  • Adjusting to brightness after exiting a dark theater.
  • Diminished smell in a room over time.
  • Comfort of hot water after a few minutes.

Purpose of Sensory Adaptation

• Prevents sensory overload; allows important signals to stand out.
• Note: Nociceptors typically do not adapt due to their role in alerting danger.

Focus Areas

• The lecture will focus on hearing, vision, smell, taste, and skeletal muscle contraction.

This summary provides a comprehensive overview of the mechanisms of sensory reception and adaptation, essential for understanding how organisms interact with their environment.