Sensory Physiology Flashcards
What is the difference between activation threshold and perceptual threshold?
Activation threshold
Minimum stimulus strength that will depolarise a receptor for APs – receptors can be high or low activation depending on their sensitivity
Perceptual threshold: minimum stimulus strength that can be detected – used clinically, ie “can you feel this”
How is specificity and selectivity different from each other?
Selectivity =how fussy a cell is with regards to the type of stimuli they respond to
What is subconscious control responsible for?
CONTROL OF MOVEMENT - via proprioceptor and vestibular input to motor pathways
AUTONOMIC RESPONSES - via interoceptors
olfactory input – salivation and gastric motility
BEHAVIOURAL RESPONSES - sight / smell of food – feeding behaviour
Describe arousal and attention and which systems are involved in this
SLEEP-WAKE CYCLE: sensory input induces wakefulness, sensory deprivation induces sleep
FOCUSSING ATTENTION: concentration on one sensory modality can suppress awareness of the others . . .
SWITCHING ATTENTION: . . . but a salient stimulus will recapture awareness
What are TRP channels?
What happens to them once damage has occured?
Change shape and open in response to temp changes
Family of them which open at diff temp ranges
Some only open in response to damaging heat/cold (nociceptors)
They bind inflammatory chemicals.
Once damage has occurred, chemicals bind to outside and around the channel = ↑ sensitivity = open to stimuli that they wouldn’t normally open to
Separate receptors are delicate and irreplaceable, give examples to show this
Auditory hair cells in ears can be permanently lost if:
noise trauma, genetic mutations, ototoxicity (chemo, aminoglycoside antibiotics)
Photoreceptors: light damage, mutations, metabolic disease, malnourishment
If afferents survive, hay potential to restore sensation
How do separate smaller cells communicate signals if they do not fire action potentials?
Separate cells are too small to need an axon so they dont fire APs. They instead have receptor potentials which releases glutamate–> APs in the afferent
Outline the different types of receptors which encode different qualities of touch
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What is spatial and temporal resolution?
Spatial and temporal resolution mean ? the receptor can?
Spatial resolution pulls ?, but temporal resolution pulls ?
Spatial and temporal resolution mean how much fine detail the receptor can recognise within the stimulus.
Spatial resolution pulls out fine details of textures, but temporal resolution pulls out fine detail in rapidly altering stimulus pa- eg if someone taps you constantly
Is spatial resolution limited?
What happens if you poke 2 different skin areas?
Spatial resolution is limited by receptive field size:
Poking 2 different skin areas supplied by a single axon gives same depolarisation despite pressing on diff branches
Any one afferent has control over a region of skin (receptive field) and the axon relays a single stream of APs.
Describe why you wouldnt be able to read braille with your forearm
2 point discrimination is poor on upper arm and back->can’t read braille w forearm as RF is large
Each bump depolarises different receptor endings but signals brought together to one axon = summate info and send to brain =remove fine detail
Fingertips have smaller receptive fields so have more afferents= need more space in somatosensory strip of brain
Sensory systems can use a frequency code, but don’t do this. Explain why, and what sensory systems do instead
Sensory systems don’t respond to the amount of pressure, rather they respond to changes in pressure.
Therefore if a constant pressure would be applied, then the action potential would stop firing in order to avoid saturation, and then re fire once it detects a Pa CHANGE
What type of temporal resolution do slowly vs rapidly adapting receptors have?
Describe Pacinian corpuscles and their structure
Respond to firm pressure, has a large receptive field and has very rapid adaptation
Located deep within the skin
Use diagrams to explain the rapid adaptation of pacinian corpuscles
The Pacinian corpuscle will only fire a single AP every time pressure is applied. ONLY if the pressure applied is fast enough to prevent the gel from squeezing out and deforming the corpuscle itself.
Label this and explain how Different types of receptor have different temporal characteristics
What is the purpose of lateral inhibiton?
Adaptation + lateral inhibition mean afferents can respond strongly to small changes, over a v large stimulus range
This boosts their “dynamic range” + makes them resistant to “saturation”
Red represents eg a splinter:
What are the different parts of the primary SSC?
Describe how the skin receptors detect different qualities of touch and relate this to the PSSC
