9 - Principles Of Sensory Systems Flashcards
Sensation
Process of encoding events and stimuli by nervous system
Perception
Process by which brain interprets sensory info
Transduction
Conversion of one energy form to another
In sensory receptors, a physical stimulus causes…
A change in mempot in receptor cell that performs transduction (receptor potential)
Transmission and transduction
- Mechanoreceptors in somatosensory system
- Photoreceptors in visual system
- Chemical receptors in taste and smell
Mechanoreceptors in somatosensory system
Sensitive to different levels of pressure and vibration and contain mechanically gated ion channels
What do eyelids, cornea, lens and pupil control?
Amount of light entering eye and image focus
Opsin molecules in photoreceptor membrane absorb…
Photons of light, produce graded hyperpolarisation in mempot
Rods are sensitive to _______ light levels
Low
Cones sensitive to ______ light levels
High
Are there photoreceptors at optic nerve head?
Nope - blindspot
Salt sensations
Na+ channels
Sour sensation
H+ channels
Other taste sensations
Special G protein coupled receptors
Are somatosensory mechanoreceptors spiking or non-spiking?
Spiking neurons
Are APs different in each sensory system?
No - a nerve is a nerve and APs basically identical
How do sensory neurons encode info?
In rate and timing of APs
Rate coding
Different rates for different stimuli
Temporal coding
Different timings for different stimuli
T/F - a neuron can encode only one stimulus feature
False - a neuron can encode multiple stimulus features
T/F - a neuron’s responses to repetitions of an identical stimulus are the same
False - highly variable
To ensure reliable responses and account for variability,
Every stimulus encoded by population of neurons
Forms of adaptation
- somatosensory: clothes on your back
- visual: mean luminance inside vs outside
- auditory: aircons
Why have adaptations?
Limited no. Neurons available to encode stimuli
Optimise neurons to encode change
Matches neural sensitivity to prevailing environmental stats
Topographic maps in cortex
Somatosensory, auditory and visual cortex each contain topographic map
Somatosensory cortex somatotropin map
Adjacent neurons respond to touch of adjacent skin surface regions
Auditory cortex contains a tonotopic map
Adjacent neurons optimally activated w/ same freq
Visual cortex contains retinotopic map
Adjacent photoreceptors in retina encode adjacent parts of visual field
Adjacent neurons in primary visual cortex encode adjacent parts of visual field
