Lec 8: Sensory receptors Flashcards
sensory receptor
convert a stimulus into an electrical signal (action potential)
sensory pathways
convey sensory info from peripheral and central NS
Sensory processing
CNS
Cranial nerves
C1-C8
Thoracic nerves
T1-12
Lumbar nerves
L1-5
Sacral nerves
S1-5
Coccygeal nerves
CO1
Dermatome
An area of skin that is mainly supplied by a single spinal nerve which relays sensation from the skin to the brain
Somatotopy (brain body picture)
the correspondence of an area of the body where sensory info arise to a specific point in the brain where this info is processed
Somatosensory
info relayed from receptor in skin, body surface, muscles and joints. (controls voluntary movements of skeletal muscle
Viscerosensory
info relayed from receptors mainoy in visceral organs (incl. blood vessels) (influences autonomic - unconscious- regulation of these organs
(location) Primary vs seconday (and tertiary) afferent neuron
Primary - part of PNS, found in ganglia of cranial nerves and terminate in brain stem. 2 and 3 - part of CNS and are part of ascending sensory fibre tracts in spinal chord, relay info to cerebral cortex
Pseudounipolar neuron
A neuron that has an axon that has split into two branches - one branch to the PNS and the other to the CNS. Most peripheral sensory afferent neurons are pseudounipolar
Mechanoreceptors
pressure, sound eg hair cells in ear
chemoreceptors
chemical substances, eg taste buds and olfactory cells in nose
thermoreceptors
temperature, egnerve edings in skin and hypothalamus in brain
photoreceptors
light, eg rods and cones in retina of eyes
nociceptors
invloved in perception of pain
What is receptor potential caused by
inreasced membrane ion flux (usually na or ca) due to change in gated ion channels that are responsive to the stimulus
Receptive fields
the area within which a sensory receptor can respond to a stimulus. they may overlap, max sensitivity is the largest area of overlap
Lateral inhibition
the most strongly activated neurons at the centre inhibit the less excited neurons in the surrounding areas (makes stimulus easier to percieve and localise
sensory adaptation
when sensory receptors reduce their sensitivity to the stimulus
Slowly adapting receptors (SA)
Tonic receptors - gradual adaptation to a constant stimulus
Rapidly adapting receptors (RA)
Phasic receptors - adapt quickly
Pacinian corpuscles
pressure receptors sensitive to vibration located in the dermal layer of the skin (more abundant on palms) large oval shaped, phasic receptors, large receptive fields on skin’s surface
Mesissner’s corpuscle
found in upper dermis in hairless skin regions of fingertips and eyelids. respon to fine touch and pressure but also low frequency vibration or flutter. rapidly adapting, fluid filled encapsulated neurons with a small receptive field
