Week 6A: Touch and Pain

A set of 30 vocabulary flashcards covering skin types, tactile receptors, pain pathways, and proprioception based on the Foundations of Biological & Cognitive Psychology lecture.

What is skin and what are the two types of skin?

Skin is the largest organ of the body, serving as a protective barrier and playing roles in sensation, temperature regulation, and more.

The two types of skin are Glabrous and Hairy.

Glabrous skin

A type of skin found on the palms of the hands and the soles of the feet.

Hairy skin

The type of skin found everywhere on the body except for the palms of the hands and the soles of the feet.

Skin sensations

are the sensations perceived by the skin, including touch (mechanical stimuli), pain, body sense (proprioception), temperature which help to communicate information about the environment.

Epidermis

The outermost layer of the skin above the dermis.

Dermis

The layer of skin below the epidermis that contains various tactile receptors.

Hypodermis (subcutaneous layer)

The deepest layer of skin, made of fat and connective tissue, it helps insulate the body and cushions internal organs.

Tactile receptors

Sensory receptors in the skin that detect touch, pressure, vibration, and texture, playing a crucial role in how we perceive tactile stimuli.

1. Merkel's disc

A tactile receptor responsible for perceiving fine details, such as reading braille.

2. Meissner corpuscle

A tactile receptor that detects flutter, such as when an object is slipping through the fingers.

3. Ruffini organ

A tactile receptor that detects stretching, for example, when picking up an object.

4. Paccinian corpuscle

A tactile receptor sensitive to vibration and fine texture, such as when using a tool.

Receptive field

The specific area of skin that a particular cell receives information about.

Two point threshold

The smallest separation of two separate but adjacent points of stimulation on the skin that produces two distinct impressions of touch; measured at $2\,mm$ on the fingertip and $3.5\,cm$ on the arm.

OR the minimum distance between two points of physical contact (such as the tips of a caliper) that must be applied to the skin for a person to perceive them as two distinct, separate touches rather than one.

Somatosensory cortex

The region of the brain that processes and integrates sensory information from the body, including touch, temperature, pain, and proprioception.

Homunculus

A representation showing that the somatosensory cortex is most sensitive to the lips, hands, and face.

Active touch

The active exploration of the environment through touch.

Advantages:

+More parts of body contact object

+You can search for the most diagnostic parts of objects to feel

+Kinesthetic senses are also engaged

Passive touch

Touch perception that occurs when the body remains stationary.

Spatial cues

Information about texture derived from bumps and grooves when the finger is stationary or moving.

Temporal cues

Information about texture perceived only when moving a finger across a surface, involving high-frequency vibrations detected by Paccinican corpuscles.

Tactile agnosia

A condition where patients cannot identify objects by touch but have no problems with spatial processing.

Tactile extinction

A condition characterized by problems in spatial processing without impairments in object recognition.

Aristotle's Illusion

A tactile illusion where crossing two fingers and touching an object results in the perception of two objects.

Cutaneous rabbit

A tactile illusion where widely separated taps are perceived as evenly spaced jumps, involving activity in the primary somatosensory cortex ($S1$).

Nocieceptor

A specialized receptor for detecting pain.

Two types of pain

Delta fibres and C fibres

A delta fibres

Fibre types responsible for fast, sharp pain such as pin pricks, pinches, or extreme temperatures.

C fibres

Fibre types responsible for slow, dull pain; mild stimulation of these can sometimes be perceived as pleasurable.

Gating of pain

A process in the spinal cord where painful information can be reduced by non-painful tactile inputs (like massage) or top-down factors.

Referred pain

Pain that appears to come from a skin surface remote from the organ sending the nociceptive signal, such as left arm pain during a heart attack.

Phantom limbs

The perception of a limb in its place after it has been amputated, indicating the missing hand is still represented in the brain.

Proprioception

The sense of where your body is in space, using signals from muscles and other modalities like the vestibular system.

Kinesthesis

The sense regarding the movement of the limbs in space.

Pinocchio Illusion

An illusion where stimulation of the biceps leads to the perception of the arm or even the nose extending.

Ian Waterman (IW)

A patient who lost proprioception, kinesthesis, and touch due to a viral infection and had to learn to compensate using visual information.

CT (C Tactile)

A receptor discovered in 2002 that is responsible for pleasant touch and the enjoyment of being cuddled.

What is the role of Merkel's disc in sensory perception?

Merkel's disc is responsible for perceiving fine details, such as reading braille.

What tactile receptor detects fluttering sensations when an object slips through the fingers?

Meissner corpuscle detects flutter, helping in the perception of slipping objects.

What type of sensation do Ruffini organs detect?

Ruffini organs detect stretching sensations, for example, when picking up an object.

What do Pacinian corpuscles primarily respond to?

Pacinian corpuscles are sensitive to vibration and fine texture.

What factor is measured by the two-point threshold?

The smallest separation of two distinct touch points that can be perceived on the skin.

What phenomenon describes the perception of pain from a remote area of the body during damage to an organ?

Referred pain describes this phenomenon where the pain is felt in a different location.

What condition involves the inability to identify objects by touch despite intact spatial processing?

Tactile agnosia.

How does active touch differ from passive touch in sensory exploration?

Active touch involves movement and exploration of objects, while passive touch occurs when the body is stationary.

What is the Pinocchio illusion?

An illusion where stimulation of the biceps leads to the perception of the arm or even the nose extending.

What condition did Ian Waterman experience that altered his sensory perception?

Ian Waterman lost proprioception, kinesthesis, and touch due to a viral infection.