Touch Flashcards
What processing system is the perception of touch part of?
The somatic sensory (somatosensory) processing system.
What does touch provide information about?
The nature of surfaces and objects in the world that are in direct contact with the skin.
How is touch vital for survival?
It informs us of potentially useful and harmful stimuli.
In what ways is touch distinct from the other 4 sense modalities?
- receptors are varied and distributed throughout the body (rather than specific localised structures)
- perceptual apparatus (receptors, pathways etc.) mediating touch responds tod different types of stimulation, with diverse sensation qualities produced.
What does the fact that different types of stimulation cause different sensations suggest?
That there are multiple touch pathways, rather than a unitary pathway.
List some of the sensations touch can evoke.
Mechanical pressure (contact, vibration, roughness, etc.), temperature, itch, and pain.
What do receptors in the muscles and joints encode?
The postures, locations and movements of the body - proprioception.
What is proprioception important for?
Active touch.
What are the dead layers and living cells called in mammalian skin?
Epidermis and dermis, respectively.
What are the sensory receptors in mammalian skin?
Meissner’s corpuscle, basket cell, Merkel’s disc, Free nerve ending, Kraus end bulb, Ruffini ending, and Pacinian corpuscle.
Which of the sensory receptors in mammalian skin is studied the most?
Pacinian corpuscles.
Which sensory receptors in mammalian skin respond only to pressure?
Meissner’s corpuscle, basket cell, Merkel’s disc, Ruffini ending, and Pacinian corpuscle.
What do free nerve endings in mammalian skin respond to?
Pain, temperature, and pressure.
What do Kraus end bulbs respond to?
Temperature (possibly).
What did Iggo (1976) propose?
That different sensory qualities are mediated by different specialised receptors within the skin layers.
What are mechanoreceptors?
Touch receptors that respond to pressure or indentation of the skin.
What is glabrous skin?
The smooth, hairless skin found on the palms, fingers, and soles of the feet.
What 4 kinds of mechanoreceptors does glabrous skin contain?
Pacinian corpuscles, Meissner corpuscles, Merkel discs and Ruffini endings.
What did Johansson and Vallbo (1983) state?
That there are about 17000 mechanoreceptors on the glabrous skin on the hand.
Does stimulation of a particular type of receptor exclusively evoke a specific touch sensation?
It’s not clear - natural stimuli activate multiple types of mechanoreceptors.
How do the four types of mechanoreceptors send information to the brain?
Via afferent touch fibres.
How can afferent fibres be classified?
According to their properties (temporal and spatial).
How do slowly and rapidly adapting afferent fibres differ?
Slowly adapting fibres respond continuously to a persistent tactile stimulus, whereas rapidly adapting fibres respond only to the onset and termination (i.e. change) of a stimulus.
Describe the receptive fields in the skin.
They’re organised concentrically, e.g. with an excitatory centre and inhibitory surround.