Touch

Senses II

Touch and pain are from the

Somatosensory system

Somatosensory system tells us

Info from body about touch, pressure, vibration, pain, temperature, and proprioception.

Discriminative

Features we can distinguish and identify easily

Non-discriminative

Features we cannot distinguish and identify easily.

Exteroception

Information from external world

Mechanoreception

pressure/touch (tactile sensitivity)

Thermoreception

temperature

Nocireception (nocicpetion)

noxious (damaging or potentially damaging) stimuli

PROPRIOCEPTION 

Provides information about position and movement of limbs and body in space

INTEROCEPTION 

Provides information from internal organs.

Nerve fibre endings

Specialised for types of stimuli by ion channels of receptive zone and accessory structures.

What are accessory structures made of?

Connective tissue and fluid.

Receptors without accessory structures

Free nerve endings

Touch sensations

Cutaneous discriminative mechanoreception.

The major mechanoreceptors that contribute to discriminative mechanoreception in humans

1. Meissner’s corpuscles (upper layers of skin)

2. Merkel’s disks (upper layers of skin), and

3. Pacinian corpuscles (deep in the skin).

4. In hairy skin, hair follicle receptors replace Meissner’s corpuscles.

Accessory sheaths

Modify how the energy from one stimulus acts on the nerve terminal underneath.

Adaptation rate

Ability to tell if a stimulus is changing and how fast it is doing so

Receptive field size

How precisely you can identify where the stimulus is happening on your skin

3 Dimensions of Fine Touch

1. Form perception

2. Texture perception

3. Vibration perception

FORM perception

Identify the form and shape of objects solely by touch (as in Braille reading)

1. TEXTURE perception

Feel and discriminate the smoothness/roughness of an object

1. VIBRATION perception

Distinguish between something fluttering on our skin through to something vibrating on our skin