Sensory Systems Flashcards
Law of specific nerve energies
activity by a particular nerve always conveys the same type of information to the brain
Pathway of light
Pupil > focused by lens and cornea onto retina (lined with visual receptors)
Cellular organisation is (eyes)
bipolar cells (back of the eye) synapse with ganglion cells (which form the optic nerve). Amacrine cells then synapse with bipolar and ganglion cells (many types of GC)
Types of ganglion cells
• Midget GC (parvocellular pathway)
• Parasol GC (magnocellular pathway)
• Bistratisfied GC (konicellular)
Optic chiasm
place where two optic nerves meet. Most axons terminate in the lateral geniculate nucleus.
Fovea
central portion of the retina. Lots of receptors, each receptor 1:1 with bipolar and ganglion cells. Poor low light but high spatial
Periphery of retina
greater number of receptors converge, low spatial but greater perception in faint light
Visual receptors
Rods: 120 million, most in periphery
Cones: 6 million, most around retina. Colour.
Trichromatic theory
occurs through relative rates of response by three kinds of cones. Ratio of activity determines the colour
Opponent process theory
paired opposites (R-G, B-Y). Mechanism = bipolar cells excited by one set of wavelength, inhibited by another
Retinex theory
cortex compares information from various parts of retina to determine brightness. Explains consistent colour perception in lighting.
Primary Visual Cortex (V1) (occipital lobe)
• Receives input from lateral geniculate nucleus, visual perception
• Various cell types – simple, complex, end-stopped.
• Secondary visual cortex (V2, important for binocular disparity) gets info from V1.
Ventral stream
the ‘what’, identify and recognise objects
Dorsal stream
the ‘how/where’, visually guided movements
Regions of brain responsible for facial recognition
• Core: Inferior occipital gyri
• Extended: Intraparietal sulcus
Brain regions responsible for motion perception
- Middle-temporal cortex – cells w directional selectivity
- Medial superior temporal – optic flow
Process of sound transduction
• Outer ear: Pinna
• Middle ear: Tympanic membrane, malleus, incus, stapes, oval window
• Inner ear: Cochlea (basilar membrane and tectorial membrane
What is sound and audition?
Sound waves are transduced, period compressions of air or water
Place theory
each hair cell in BM sensitive to only one frequency
Frequency theory
BM vibrates with sound and causes axons to produce APs at same frequency
Pitch perception theory
combines both, PlaceT = high frequency sounds, FrequencyT low frequency sounds
Primary auditory cortex location
superior temporal cortex, sylvian fissure
Primary auditory cortex purpose
Primary site for processing information
Sound localisation
does not rely on activity of sensory receptors, computed in CNS.
Cues for sound and audition
Sound shadow and time of arrival
What is vestibular sensation
composed of several structures, detect position/movement of head
Vestibular sensation structures
• Saccule and utricle contain otoloths and hair cells
• Three canals contain jellylike substance
Types of mechanoreceptors
• Meissners corpuscles – light pressure, fast adapt
• Merkels disks – light p, slow adapt
• Pacinian corpuscles – deep p, fast adapt
• Ruffini endings – deep p, slow adapt
Transduction of touch
information enters CNS/brain through cranial nerves. Below head VIA spinal cord/nerves.
Labeled line theory
Taste depends on which receptor is activated
Across fibre pattern theory
pattern of activity dictates taste perception
Transduction of taste
o Salt permits sodium ions to cross membrane
o Sour detects acids
o Sweet/bitter/umami activate 2nd messenger
Taste
Papillae on surface of tongue, 10+ taste buds each w 50 receptors
What is smell?
Olfactory receptors respond to odour molecules, which are lined in epithelium.
Transduction of smell
occurs via second messenger. Info carried to olfactory bulb, which projects to cortex.
