Test 2: Sensory System Flashcards
Sensory receptors
transduce energy into neural signals. Lack axons; form synapses with dendrites of other sensory neurons
Visual system
Detects electromagnetic radiation (EMR) emitted. 400-700 nM. Perceived color is related to wavelength of light. Brightness-intensity of radiation.
An eye consists of:
Aperture (pupil) to admit light, lens to focus light, photoreceptive elements (retina) that transduce the light stimulus
3 layers of cells in retina:
Ganglion cell layer, bipolar layer, and photoreceptor layer (transduces light into electrical signals)
Light travels through all three layers, bounces off the back and is then processed by the cells
2 types of photoreceptors
Rods and cones
Rods
120 million. light sensitive, found in periphery of ret, low activation threshold
Cones
6 million. Found mostly in fovea; we see color best right in front of us.
Where are photopigments located?
On outer segments of rods and cones
What do photopigments consist of?
An opsin (a protein) and retinal (a lipid)
How do rods and cones fire?
NA+ channels are open in the dark. Glutamate is released and depolarizes membrane.
Light splits the opsin and retinal apart, which closes NA+ channels. Net effect of light is to hyperpolarize the retinal receptor and reduce the release of glutamate.
Which cell in the eye fires to the brain?
Ganglion Cell
Visual pathways
Ganglion cells –> thalmus (via optic nerve/tract) –> LGN (part of thalmus) –> optic radiations –> primary visual cortex
Trichromatic theory
3 different receptors in the eye, with each sensitive to a single hue. Any color could be accounted for by mixing 3 lights in various proportions
Opponent theory
People perceive three primary colors: Yellow, blue, and red. Negative color afterimages suggest that red and green are complementary colors as are blue and yellow
Visual association cortex streams
Dorsal stream: where an object is
Ventral streat: what an object is (analysis of form)
Where are sound waves transduced into nerve impulses?
Organ of Corti. Cilia movement produces tension of the link which opens an ion channel in the adjacent tip
Auditory Pathways
Cochlear nuclei –> superior olivary nuclei –> inferior colliculus via lateral lemniscus –> medial geniculate nucleus (thalamus) –> auditory cortex (temporal lobe)
Cutaneous senses
Various signals from the skin that form the sense of touch
