lecture 8 Flashcards
How is EM radiation sensed by the body?
Receptor: rod and cone photoreceptors
Range: 400 to 600nm wavelength
Sensitivity and dynamic range: single photo to bright sunlight (10^10 fold)
Receptive field: single photoreceptor, concentric ganglion cell
How is distortion of the skin sensed by the body?
Receptor: various encapsulated nerve endings
Range: 10nm to sub-damaging distortion
Sensitivity and dynamic range: mg, 0-1000 Hx
Receptive field: ovaloid from 10mm^2 to entire hand
What does the somatosensory system do?
- mediates sensations from the whole body surface, including skin and deeper tissues
What is the structure of skin?
- most of the body is covered by hairy skin
- the palmar surface of the hands and the soles of the feet are covered by glabrous skin, with skin ridges a prominent feature
Give an overview of the somatosensory system.
- There are four types of mechanoreceptors in glabrous skin
- Meissner corpuscles and Merkel complexes are close to the surface
- Ruffini organs and Pacinian corpuscles are deeper in the skin
- These receptors are innervated by large myelinated axons with cell bodies in the dorsal root ganglia
- Transmission of this information to the brain generates our conscious experience of touch
What are the layers of the skin?
- top dead layer
- epidermis
- dermis
- subcutaneous layer
Where are free nerve endings located?
epidermis
Where are Meissner corpuscles located?
right below the epidermis in the upper part of the dermis
Where are Merkel cell-neutrite complexes located?
In the deep grooves of the epidermis
Where are Ruffini corpuscles located?
dermis
Where are Pacinian corpuscles located?
Dermis/subcutaneous layer
What do Ruffini corpuscles respond to?
Skin being moved or stretched
What do Pacinian corpuscles respond to?
Vibration
How do these mechanoreceptors open sodium channels?
Thought to be literally by force - movement/pressure/whatever that receptor responds to opens the gate and allows the movement of sodium ions across the membrane leading to depolarisation
- however there is greater molecular complexity to it - resistance from ECM and inside of cell
What is the key event for generating an action potential?
depolarisation