Sensory receptors Flashcards
(34 cards)
what are sensory receptors
are nerve endings that inform your brain about the internal and external environment. convert different stimuli into frequency of action potentials so are transducers
3 types of sensory receptors
proprioceptors, mechanoreceptors, nociceptors
sensory modality
stimulus type that activates a particular receptor eg touch, pressure, joint angle, pain
adequate stimulus
form of energy to which a receptor normally responds
what is a mechanoreceptor
stimulated by mechanical stimuli, pressure, strength, deformation, give us skin sensations of touch and pressure
what are proprioceptors
mechanoreceptors in joints and muscles. they signal information about body or limb position
what are nociceptors
respond to painful stimuli
how are sensory receptors specific
highly sensitive to one specific energy form but they can be activated by other intense stimuli
what is a receptor potential
adequate stimulus causing a graded membrane potential change
what is the adequate stimulus in cutaneous mechanoreceptors and proprioceptors
membrane deformation- activates stretch sensitive ion channels. ions flow across the membrane and change the membrane potential locally
how is receptor potential graded
by stimulus intensity. stimulus triggers ions to flow through membrane locally and when depolarisation reaches the area with voltage gated ion channels (first node of Ranvier), action potentials start firing
what electrodes measure change in membrane potential
those at receptor membrane and first node of ranvier
why is it important that some mechanoreceptors experience a drop off in APs if stimulus persists
the brain can process new or changing events eg taking off or putting on clothes. some receptors only signal the onset of a stimulus
which receptors do not adapt
nocireceptors
pacinian corpuscle
senses pressure and vibration. mechanoreceptor comprised of a myelinated nerve and a naked nerve ending. mechanical stimulus deforms the capsule and nerve ending, stretches and opens ion channels, sodium influx causes depolarisation, APs generated and myelination begins.
how can pacinian corpuscle adapt
depends on capsule surrounding. can rapidly adapt by fluid between lamellae distributes, spreading stimulus impact out, minimising deformation which causes the stop of nerve endings stretching so APs stop firing. if stimulus withdrawn, the capsule lamellae spring back like suction force and Ap fire again
receptive field
a specific area where a somatic sensory neurone is activated by stimuli
ability to tell 2 points apart on the skin is measured by
two points discrimination test- the receptive field size and neuronal convergence
neuronal convergence
if there is a single path to the brain or more than one that merge
simultaneous sub threshold stimuli effect
can merge together and sum together at the secondary neuron, forming a larger secondary receptive field and initiating APs (two pencils test)
acuity
ability to locate a stimulus on the skin and differentiate it from another close. low acuity means one signal goes to brain instead of two when there is two stimuli- caused by high convergence
lateral inhibition
enhances perception of stimulus and means you can localise the central point of a stimulus precisely by receptors at edge of stimulus being more strongly inhibited than receptors near centre
where does sensory information go
to the brain, relayed via the spinal cord to the thalamus and on to the somatosensory cortex
proprioceptors include
muscle spindles, Golgi tendon organs, joint receptors
