Neuro 8 - sensory receptors

different types of senses, receptors, and factors in determining intensity of sensation

somatic senses — (internal/external, specificity)

internal or external information we are aware of
highly specific — easy to pinpoint location and direction

visceral senses — (internal/external, specificity)

internal information associated with autonomic nervous system
less specific — cannot pinpoint precise location

special senses

detected by highly specialised organs/structures

somatic senses examples

touch, temperature

visceral senses example

nausea, hunger

special senses example

vision, taste

tonic receptors

slow-adapting
important info
Ap frequency increases with stimulus

phasic receptors

fast-adapting
less important info
APs sent on detection and removal of stimulus

why is the distinction of phasic and tonic receptors useful?

prevents sensory overload (allows brain to focus and monitor important info)

thermoreceptor (stimulus and example, ion channel, tonic/phasic)

detects changes in temperature, temperature-gated Na+, phasic

chemoreceptor (stimulus and example, ion channel, tonic/phasic)

detect chemicals (e.g. CO2 and O2 conc. in blood), chemically-gated, tonic/phasic

mechanoreceptor types

tactile, proprioreceptors, baroreceptors

tactile receptors (stimulus and example, ion channel, tonic/phasic)

detect skin touch (e.g. light touch, vibration), mechanically-gated, mostly phasic

proprioceptors (stimulus and example, ion channel, tonic/phasic)

detect body position in space (e.g. stretch of muscles, joints and tendons), mechanically-gated, tonic

baroreceptors (stimulus and example, ion channel, tonic/phasic)

detect pressure (e.g. stretch of blood vessels), mechanically-gated, tonic

nociceptor (stimulus and example, ion channel, tonic/phasic)

detect pain (e.g. excess temp), can be temperature, chemical or mechanically-gated, mostly tonic

temperature-gated ion channels mechanism

different temperature-gated ion channels for different temperatures
stimulus opens channels
when receptor reaches threshold AP is fired

what are receptors?

nerve endings with a specific type of ion channel that detects a specific stimulus

intensity of sensation determined by

frequency modulation (frequency of APs) and recruitment (number of neurons)

location of sensation determined by

modality (selection of axons/motor units to be active along a specific pathway)

receptive fields

areas with receptive endings for a single sensory neuron

smaller tightly packed receptive fields

sensitive, localized stimulus

larger, spread out receptive fields

less sensitive, less localized stimulus

somatotopic map

the more receptive fields dedicated to an area of the body, the more representation (more neurons) it has in the brain