7 - Peripheral Sensory Mechanisms Flashcards
Four types of skin mechanoreceptors
Meissner corpuscles and Merkel complexes are close to the surface. Ruffini organs and Pacinian corpuscles are deeper in the skin.
Glabrous skin
Skin on palms of hands, soles of feet (hairless)
What innervate skin mechanoreceptors
Large myelinated axons with cell bodies in the dorsal root ganglia
Role of free nerve endings in skin
Nociception, thermoception
*Mechanoreceptors in the skin
Receptive field (w/r/t skin mechanoreceptors)
Area of space over which a receptor can detect touch
Basic way in which mechanoreceptors detect touch
Touch stretches receptor, opens Na+ channels in cell membrane. If this receptor potential is large enough, depolarisation.
Broad difference in response to stimulus between different skin mechanoreceptors
Rapidly- and slowly-adapting to stimulus
Slowly-adapting mechanoreceptors
Merkel, Ruffini
Rapidly-adapting mechanoreceptors
Meissner, Pacinian
Mechanoreceptors found at tips of epidermal ridges
Merkel complexes
Mechanoreceptors found in upper dermis
Ruffini endings
Mechanoreceptors found near surface of skin
Meissner receptors
Mechanoreceptors in the deep dermis and hypodermis
Pacinian corpuscles
Size of Pacinian receptor fields
Large
Size of Meissner receptor fields
Small
What do Merkel complexes respond to?
Indentation
What do Meissner receptors respond to?
Transient response to skin movement
What do Ruffini endings respond to?
Sustained response to skin movement
What do Pacinian corpuscles respond to?
Transient response to vibration
Low density (large receptor field) mechanoreceptors
Ruffini and Pacinian receptors (deep receptors)
Most common skin mechanoreceptors
Meissner
*Comparison chart of skin mechanoreceptors
In picking up an object, what role do the four mechanoreceptors serve?
Meissner - Encode rate of force Merkel - Encode grip force Pacinian - Encode vibration (when you touch object) Ruffini - Encode hand posture
Examples of mechanoreceptors not in the skin
Muscle spindle, Golgi tendon organs, cells in basilar membrane in ear
Type of mechanoreceptor present in hairy skin that is absent in glabrous
Hair follicle
Dermatome of the face
Trigeminal nerve (emerges from the pons)
Dermatome
An area of skin supplied by a single spinal nerve. Overlap significantly.
Dermatome with only a sensory branch
C1
Fastest-conducting nerve fibre
Proprioceptive from muscle spindle
Speed of nerve axons innervating skin mechanoreceptors
Second-fastest conducting axon
Path of sensory afferent from mechanoreceptor
Cell body is in dorsal root ganglion. Enters dorsal horn of spinal cord, ascends to brainstem through dorsal column (white matter tract) ipsilaterally.
