Sensory Receptors 1 Flashcards
what are 5 general classes of sensory receptors?
- mechanoreceptors
- thermal receptors
- pain receptors
- chemoreceptors
- photoreceptors
what are cutaneous sensory receptors?
+ located at ends of sensory nerve dendrites
+ function to transduce sensory info signals the brain can read
+ have specialised structures to detect sensory info from surroundings
what sensation is linked to Aδ fibres?
sharp pricking pain
what sensation is linked to C fibres?
hot cold burning ache
what are features of free nerve endings?
+ slow adapting
+ high activation
what are the different types of receptors?
\+ pacini's corpuscles \+ meissner's corpuscles \+ merkel disks \+ ruffini corpuscles \+ skin hair cell receptors
what are features of pacini’s corpuscles?
\+ largest mechanoreceptor \+ 2mm long \+ onion-like encapsulation of nerve endings \+ found in deep layers of dermis \+ detects high frequency vibration (40-500Hz) \+ Aβ fibres \+ glabrous and hairy skin types \+ low activation threshold
what are features of meissner’s corpuscles?
+ encapsulated nerves but smaller than pacini’s
+ stacks of discs interspersed with nerve branch endings
found between dermal papillae
+ detects touch, flutter and low frequency vibration (2-40Hz)
+ Aβ fibres
+ glabrous skin types
+ low activation threshold
what are features of merkel disks?
+ non-encapsulated nerve endings
+ detect static touch and light pressure
+ Aβ fibres
+ all skin types
+ consists of specialised epithelial cell and nerve fibre
+ slowly adapting
+ found just under skin surface: good discrimination
+ multiple branches found in ‘Iggo Dome”
+ work with meissner’s corpuscles to help determine texture
what are features of ruffini corpuscles?
+ responds to skin stretch
+ located in deeper layers of skin, tendons and ligaments
+ encapsulated nerve endings
+ in all skin types esp. fingers, hands and soles
+ nerve endings weave between collagen fibres which activate nerve when pulled longitudinally
what are features of skin hair cell receptors?
+ each type has a mechanosensitive receptor wrapped around its follicle
+ detect muscular movements of hair (erector muscle) and external displacements of hair
how is the brain informed about stimuli?
+ when a sensory nerve ending or receptor is stimulated enough it causes APs to travel to CNS
+ APs from pain receptors in the leg are indistinguishable in character from stretch related impulses from the arm
how does the CNS distinguish APs via leg pain receptors, from stretch related arm impulses?
+ each sensory nerve is recognised by CNS as particular modality
+ CNS reads final destination of nerve fibre
+ modal info delivered to CNS is topographical fashion
how does phantom limb sensation arise?
when sensory neurons from absent limbs are spontaneously, and can be mimicked by electrical stimulation
how does CNS determine signal strength?
+ APs have fixed potential and amplitude
+ intensity of signal determined by frequency of impulse
+ the higher the frequency the more intense the signal
what is generator potential (GP)?
+ a graded depolarisation of sensory neuron
+ proportional to strength of stimulus
+ GP initiates impulses in sensory nerves
what is the link between GP and signal strength?
the bigger the GP (depolarisation), the faster the frequency of sensory nerve impulses (so bigger signal intensity/strength)
what effect does distance from site of origin have on GPs?
amplitude decreases
what effect does distance from site of origin have on APs?
no effect as they are self propagating
what happens when there is a receptor cell that synapses onto a sensory neuron?
+ the sensory cells produce a receptor potenial when stimulated instead of GP
+ this causes receptor cells to release NTs into synapse and normal neurotransmission takes place
how are GPs and post-synaptic potentials (PSPs) the same?
+ both trigger action potentials
+ local in nature
how are GPs different to PSPs?
+ GPs can last as long as the receptor is stimulated (provided no adaption)
+ amplitude is determined directly by intensity of sensory stimulus (not NT concentration)
