6.1.9 Investigating Touch and Temperature Receptors

Types of Receptors

1. Touch Receptors:

• Found in the dermis of the skin, especially in areas like fingertips and lips.
• Examples include:
• Meissner's corpuscles: Detect light touch and vibrations.
• Pacinian corpuscles: Detect pressure and vibration.
• Merkel discs: Detect texture and sustained pressure.
• Ruffini endings: Detect skin stretch and grip force.

2. Temperature Receptors:

• Located in the epidermis and dermis.
• Two types:
• Cold receptors: Detect decreases in temperature (e.g., below 37°C).
• Warm receptors: Detect increases in temperature (e.g., above 37°C).
• Thermoreceptors rely on ion channels in their membranes that open or close in response to temperature changes.

Practical Investigation

Aim: To investigate the distribution and sensitivity of touch and temperature receptors in human skin.

Materials Needed:

• Blunt probes (e.g., toothpicks).
• Small objects with varying temperatures (e.g., warm and cool metal rods).
• Blindfold for participants.
• Ruler or grid paper for measuring distances.

Method:

1. Touch Receptors:

• Blindfold the participant to prevent visual bias.
• Gently touch their skin using two blunt probes simultaneously.
• Gradually decrease the distance between the probes until the participant perceives them as a single touch.
• Record the smallest distance at which two distinct touches are felt (this is the two-point discrimination threshold).

2. Temperature Receptors:

• Use objects at different temperatures (e.g., a warm metal rod and a cool metal rod).
• Blindfold the participant.
• Gently touch different areas of their skin with the objects.
• Record the participant's ability to distinguish between warm and cold stimuli in different regions.

Expected Results

1. Touch Sensitivity:

• Areas like fingertips and lips should have the smallest two-point discrimination thresholds, as they have a high density of touch receptors.
• Less sensitive areas like the back will have larger thresholds.

2. Temperature Sensitivity:

• Participants are expected to detect temperature changes more accurately on areas with thin skin, such as the face and hands.
• Regions with fewer thermoreceptors may show reduced sensitivity to temperature differences.