Sensory Receptors Flashcards
Def of stimulus:
environment event that excites sensory receptors
Def of sensation:
what is perceived in the brain when sensory receptors are stimulated
Sensation can be…
conscious or unconscious
Sensation differs in 3 things:
- modality: E form associated w/ stimulus
- quality
- quantity
Sensory receptors are…
specialized to respond to specific stimulus
Responses of activated sensory receptors are…
- depolarization at receptive end
- possible release of neurotransmitters at axonal end
Primary sensory neurons:
- have receptors at dendritic ends
- simple unmodified dendritic ends (naked nerve endings)
- modified endings: enlarged/wrapped in CT
What do sensory receptors monitor?
both internal and external conditions
What falls under internal conditions?
- proprioceptors
- visceral
What falls under external conditions?
- special sensory
- cutaneous
Sensory receptors are classified as…
- somatic (skeletal muscle and skin)
- visceral (organs)
- special senses
Examples of somatic receptors:
- proprioceptors
- cutaneous receptors
Proprioceptors:
- type of somatic receptor
- sense info about body’s position in space and weight difference
- muscle spindle
- golgi tendon organ
What do muscle spindles detect?
muscle length
What do golgi tendon organ detect?
changes in muscle tension
Cutanoues receptors:
- type of somatic receptor
- naked nerve endings
- Merkel discs
- Ruffini endings
- Meissner’s corpuscles
- Pacinian corpuscles
Naked nerve endings detect…
pain b/c it is a nociceptor
Merkel discs detect…
sustained pressure
Ruffini endings detect…
deep pressure
Meissner’s corpuscles detect…
light touch
Pacinian corpuscles detect…
vibration
Visceral receptors respond to…
- organ sensations
- pain
- stretch
- chemoreceptor
- baroreceptor
- osmoreceptor
Special senses are…
modified neurons localized in specialized sensory organs in head
- passes info alond to afferent neurons
What do special senses detect?
- vision
- hearing
- taste
- smell
- rotational/linear acceleration of head
Sensory receptors have a ______ field
receptive
- can be determined by two point discrimination test
Two point discrimination test looks at…
- sensitive area: has smaller receptive fields (fingertips)
- less sensitive areas: convergence of many primary neurons to one secondary neuron
Sensitive areas have a 1:1 relationship between…
primary and secondary neurons
Sensory transduction converts E of signal modality to…
graded potentials (GP)
T/F: types of stimuli transduced depends on receptor type
T
Mechanoreceptors respond to…
- mechanical deformation of receptor
- pressure
- cell stretch
- vibration
- acceleration
- sound
Baroreceptors monitors…
stretch of hollow structures
Chemoreceptors respond to…
- chemicals
- oxygen
- pH
- organic molecules
Nociceptors respond to…
physical and chemical damage of tissues
Thermoreceptors detect…
changes in temperature
Photoreceptors detect…
light
What happens to membrane when a stimulus is applied?
depolarization will alter membrane potential
Generator potential (GP):
- produced by stimulus acting on receptors on afferent neurons
- is the small temporary change in membrane potential
GP will create ______
local current: flow of ions
- flows away from stimulated area to area w/ higher # of VG Na+ channels
What happens if GP has enough amplitude?
threshold will be reached and AP generated
Receptor potential (RP):
- produced in specialized receptor cell, which in turn stimulates afferent neurons
- can be depolarized or hyperpolarized
Amplitude and duration of RP regulates…
amount of neurotransmitters released
- enough neurotransmitters released = AP generated
Difference between GP and RP?
- GP: produced by stimulus acting on afferent neurons (enough amplitude = AP)
- RP: produced in specialized receptors (enough neurotransmitters = AP)
T/F: receptors don’t have adaptive abilities
F, they do because it lets body know if it needs to monitor the stimulus or be constantly aware of stimulus
Adaptations of receptors leads to…
decrease of GP/RP to constant intensity stimulus
Adaptations of receptors will produce…
a decrease of frequency of AP over time in response to constant intensity of stimulus
Total adaptation of receptor leads to…
loss of perception of stimulus
Phasic receptors:
- respond to changes in stimuli
- fast adaptation: stops responding immediately when stimulus stops changing
- sends signal only when there is a change in stimulus
Phasic receptors have a predictive function, which provides…
- good assessment of rate of change
- pacinian corpuscles
- hair receptors
- olfactory receptors
Tonic receptors:
- intensity receptors
- continue to send signal as long as the stimulus persists
- very slow/no adaptation
- keeps consistent firing rate when stimulus is applied
Tonic receptors are important for…
- homeostasis
- limiting potential for injuries
Exampes of tonic receptors:
- nociceptors
- proprioceptors
- baroreceptors
Magnitude of GP/RP is directly proportionate to…
stimulus intensity (log)
Magnitude of GP is directly proportionate to…
rate of AP of afferent fibers (linear)
Information coding:
how info about a stimulus is carried in CNS
Sensory coding involves:
- which sensory receptors are activated
- response of sensory receptor to stimulus
- intensity and duration of stimulus
- info processing in sensory pathway
Aspects that can be coded:
- sensory modality: coded by pathway
- intensity of stimulus: coded by rate of APs
Types of sensory modalities:
- cutaneous stimuli
- noncutaneous stimuli
Cutaneous stimuli are interpreted as:
- touch
- pressure
- cold
- warmth
- pain
Noncutaneous stimuli are interpreted as:
- vision
- auditory
- position
- taste
- smell
Threshold stimulus:
- weakest stimulus that produces AP
- below this = no AP generated
- can add subthreshold stimulus to get AP (spatial and temporal summation)
Spatial summation:
- progessively larger # of primary afferent neurons activated simultaneously
Temporal summation:
- single primary afferent neuron fires multiple times in a row
T/F: greater stimulus usually affects a smaller area of CNS
F, should affect greater area b/c can affect more sensory receptors
Sensory unit:
a sensory neuron and all its receptive ends
- activate more receptors in one sensory unit leads to more APs/sec produced
receptive field:
- area whose stimulation affects neuron AP
- can overlap with multiple sensory units
Continuous info is provided by…
tonic receptors
Beginning/ending signal are provided by…
phasic receptors
Spatial location of stimulus:
activation of specific population of sensory neurons w/ endpoint of pathway onto cortex
- ex: lateral inhibition and somatotopic map
Lateral inhibition:
mechanism where transmission of signal can be inhibited laterally, which limits widespread of signal
- enhances contrast between sites of strong and weak stimulus
Somatotopic map:
plan of body regions in sensory cortex
Movement of info:
primary sensory afferent neurons in PNS to interneurons in CNS to CNS integrative areas
Speed of transmission is affected by:
- diameter and myelination of neurons
- # of synapses that must be crossed (more = slower)
of sensory units stimulated leads to…
size of receptive field
Organization of relaying interneurons allows CNS to _______ info
- filter
- correlate
- summate
- sort
Convergence of interneurons:
# of signals entering neuronal pool > # exiting - allows summation of weak signal and can filter out signal
Divergence of interneurons:
of signals entering neuronal pool < # exiting
- amplifies signal within single pathway
- can maintain signal strength and send to multiple pathways
