Peripheral Sensory Mechanisms Flashcards
Skin mechanorecepetors
merkel, meissner, ruffini pacinian
Meissner corpuscles are located
close to the surfaceof the skin in crests of dermis
Merkel complexes are located
close to the surface of the skin in epidermal valleys
Ruffini organs are located
deeper in the skin within the upper dermis
Pacinian corpuscles are located
deeper in the skin within the lower dermis or subcutaneous layer
Pacinian corpuscles respond to
vibration (transient response)
How do Pacinian corpuscles transduce vibration?
vibration stretches the membrane in which ion channels lie, pulling them open allowing Na+ to rush in
Slowly adapting receptors
show initial response to a stimulus, then encode the stimulus as time goes on until it goes away - continual information about how much stimulus is still being applied
Rapidly adapting receptors
only care about changes - when the stimulus comes on and when it is removed
Which mechanoreceptors are slowly adapting?
Merkel and Ruffini
Which mechanoreceptors are rapidly adapting?
Meissner and Pacinian
Merkel complexes respond to
pressure/indentation (sustained response)
Ruffini organs respond to
skin movement and stretch (sustained response)
Meissner corpuscles respond to
skin movement (transient response)
Tactile receptors respond to
only gentle forces on the skin eg touching a blunt object; tell us about external environment
Nociceptors respond to
more intense stimuli/tissue damage eg increasing temperature causing change to the tissue that releases mediators; tell us about internal environment
Mechanoreceptors conduct at a velocity of
~50m/s
Why do dermatome regions differ from peripheral nerve innervation patterns?
formation of plexuses and branching/crossing over of nerve roots leads to different regions of innervation by peripheral nerves than their cervical roots
Damage to a peripheral nerve shows what pattern of peripheral sensory loss?
peripheral nerve innervation (eg ulnar, radial on dorsum of hand), not dermatomal (eg C6, C7, C8 on dorsum of hand)
Damage to a cervical nerve root will show what peripheral pattern of sensory loss?
Dermatomal ie C6-C8 distribution on the dorsum of the hand
Cell bodies of mechanosensory afferents are in
DRG for 31 spinal nerves, trigeminal ganglia for trigeminal nerves
Cell bodies of nociceptor afferents are in
DRG
What happens to pain and temperature fibres at the spinal cord?
They synapse and cross over to ascend on the contralateral side of the spinal cord; this is opposite to mechanosensory afferent fibres
Mechanosensory afferent fibres ascend on which side of the spinal cord?
Ipsilateral
Pain and temperature afferents ascend on which side of the spinal cord?
Contralateral (synapse first in SC)
Pain and temperature receptor response is disrupted by
Spinal cord level lesions on the contralateral side
Touch receptor response is disrupted by
Spinal cord level lesions on the ipsilateral side
