Introduction to Sensory Physiology and Perception Flashcards
What is the required pathway for a sensory event to occur?
Stimulation -> transduction -> receptor potential -> threshold -> AP -> propagation -> CNS ->
What are other components of the sensory nervous system apart form sensation and perception?
Subconscious and arousal
What are 3 types of subconscious sensory responses?
- Control of movement (proprioceptor, vestibular)
- Autonomic responses (olfactory input->salivation)
- Behavioural repsonses (sight/smell -> feeding)
What is the difference between sensation and perception?
Sensation is being aware of an event that’s occurred, perception is how we respond to the event - what/where/how?
What do photoreceptors detect?
Light (EM radiation)
Where are chemoreceptors found and what do they detect?
Nose, mouth - for smell and taste.
In most parts of body to respond to inflammatory chemicals -> response to injury, this makes them nociceptors and produce sensation of pain.
In some systems the receptors are also the primary afferents. How is this true for the touch reflex involving fingertips? What are they good for?
There are pressure sensitive endings on our fingertips - there is a sensory receptive membrane that itself gets depolarised in response to pressure and sends signals up the dorsal column pathway.
Important for being resilient to injury.
All-in-one axons have the ability to regrow if an injury cuts not too close to cell body and can restore sensation. Why is this NOT the case with photoreceptors and auditory receptors?
Photoreceptors and auditory receptors are highly specialised, separate cells and communicate via synapses unlike the all-in-one afferents.
So therefore a powerful stimulus is likely to destroy the receptors as they are very sensitive.
What kind of potential does transduction produce?
Electrotonic potentials -> which may give rise to APs if threshold reached
What is perceptual threshold?
Whether or not subject can detect the stimulus, low threshold means it’s easy for person to detect stimulus. Can be most easily tested in a clinical environment.
Is a large or small receptive field important to read braille (for example) or to differentiate the stimulus?
Small receptive field -> Allows higher innervation density so each lump will produce its own individual signal, whereas in the arm there are large receptive fields that all ‘merge’ into one input.
What’s the problem with small receptive fields?
Higher innervation density is required - more cortex is needed to deal with the input (refer to sensory humunculus, postcentral gyrus).
What is temporal resolution and why is it problematic?
A measure of spatial resolution, if two probes are tapped separately over a sensory receptor it forms one potential rather than two because the receptor cannot repolarise quickly enough to give rise to 2 APs. So it’s perceived as one tap rather than two.
Sensory systems adapt to constant stimuli, how is this?
To begin with, the higher the frequency of firing of APs, the stronger the stimulus. But sensory receptors only work like this for about 10 ms.
Vast majority adapt, there is high frequency to start with but then depolarisation gradually fades away and frequency firing returns to original level.
Sensory system adaptation highlights ‘salient’ moments, what does this mean?
It is noticeable when the stimulus strength changes, allows receptors to encode changes in stimulus strength over huge range without saturation.
