Lecture 8- Touch Flashcards
What can you tell from the size of a receptive field?
-tells you how the info starts to get analysed, tells you about the resoultion of that system
What are the four types of receptors in the skin?
-Various encapsulated nerve endings -Merkel, Meissner, Pacinian, Ruffini
What does the somatosensory system do?
-mediates sensations from the whole body surface, including skin and deeper tissues
What is the overall structure of the skin?
-most of the body covered by hairy skin. -Palmar surface of the hands and the soles of the feet are covered by glabrous skin, with skin ridges a prominent feature
What type of receptors are the receptors in the skin?
-mechanoreceptors= respond to mechanical stress/stimuli
What 2 mechanoreceptors are close to the surface?
Meissner corpuscles and Merkel complex
What 2 mechanoreceptors are deeper in the skin?
Ruffini organs and Pacinian corpuscles
What are the receptors innervated by and where are their cell bodies?
-innervated by large myelinated axons with cell bodies in dorsal root ganglia
What is hepatic manipulation?
-can work out what an object is just by touch
What is special about the Merkel complex?
- the Merkel cells are not neural
- it is a complex and the nerve endings end around these Merkel cells and transmit information to the CNS
What does the Meissner corpuscle look like and why?
- like a corn cob sort of
- the shape of the end= connective tissue, important as it determines how the nerve will be stimulated depending on its shape
What does the Pacinian corpuscle look like?
- like a marine worm
- flat= because it reacts to vibrations (again the shape confers its properties)
What does the Ruffini organ look like?
- like a Neptune’s necklace (sea geep)
- long= thus reacts to stretch of the skin
In which layer are the Merkel and Meissner?
-epidermis (upper)
In which layer is the Ruffini organ?
-dermis (below epidermis)
In which layer is the Pacinian corpuscle?
-lower bit of dermis and subcutaneous layer (below dermis) hypodermis
How does transduction work in mechanoreceptors (afferent fibre)?
- afferent fibre is encapsulated by Schwann cells
- then the receptor at the end
- in the membrane of the receptor there are mechanically gated channels (when you touch sth or move sth across= the membrane stretches) it opens a Sodium channel and that results in DEPOLARISATION of the cell
- if the stimuli is strong enough, reach the threshold and fire an action potential (all or nothing system)
- all the skin receptors do it but respond differently to ongoing stimuli