Study Notes on Sensory Physiology

Stage One of Sensory Physiology

Overview

• Sensory physiology involves the stimulation of receptors, which are cells that perceive different types of stimuli.

• The classification of receptors can be done in three main ways: by type, location, and complexity.

Classification by Type

1. Mechanoreceptors

   • Definition: Receptors that require a physical alteration to function.

   • Function: Respond to touch, vibration, and pressure.

   • Example: When you touch or apply pressure to a surface, these receptors are physically altered and activate.

2. Thermoreceptors

   • Definition: Receptors that detect changes in temperature.

   • Function: Can sense both hot and cold temperatures.

   • Example: When touching an ice cube or hot water in a shower, thermoreceptors respond to these temperature changes.

3. Photoreceptors

   • Definition: Receptors that respond to light.

   • Function: Detect changes in light intensity.

   • Example: Detecting if the environment gets darker or brighter.

4. Chemoreceptors

   • Definition: Receptors that detect changes in chemical concentrations.

   • Function: Monitor levels of various chemicals within the body including oxygen, carbon dioxide, acids, bases, and glucose.

   • Example: Changes in blood chemistry such as shifts in oxygen levels activate these receptors.

5. Nociceptors

   • Definition: Receptors that respond to pain stimuli.

   • Function: The most prevalent type of receptor; they indicate body damage and are crucial for self-preservation.

   • Example: Pain perception occurs when there is something wrong with the body, prompting the activation of nociceptors.

   • Important Note: Excess stimulation of other types of receptors (mechanical, thermal, chemical) can also trigger nociceptors, leading to pain perception (e.g., holding ice too long results in pain).

Classification by Location

1. Exteroceptors

   • Definition: Receptors that respond to stimuli from outside the body.

   • Location: Primarily located in the skin or near body surfaces such as mucous membranes in the nasal passages or inside the mouth.

   • Examples of Senses:

     • Vision

     • Olfactory (smell)

     • Gustatory (taste)

   • Function: Help to take input from the surrounding environment.

2. Interoceptors

   • Definition: Receptors that respond to internal stimuli within the body.

   • Function: Monitor internal conditions, such as blood pressure, heart rate, respiratory rate, and hormone levels.

   • Role of Chemoreceptors: Play a significant role in sensing blood pressure among other internal conditions.

3. Proprioceptors

   • Definition: A specialized category of interoceptors that provide information on body position and movement.

   • Location: Found in tendons, ligaments, muscles, inner ear, and joints.

   • Function: Help the body to understand its position in space and maintain balance and posture.

   • Importance: Considered a distinct category due to their extensive role and significance in sensory perception.