6-sensory systems Flashcards
Describe how we can see different colors.
There is electromagnetic radiation all around us. However, humans can only detect a tiny faction of the available range. Different surfaces reflect different amounts of light, which albedo, the proportion of incident light that a surface reflects, determines how light a surface appears. Intensity is determined by the amplitude, or height. Hue, or color, is determined by the wavelength, or distance between two peaks of a wave.
Describe the whole process of how we can see.
- Light passes through the cornea, a thin tissue that protects the eye and bends light to provide focus, through the pupil, a small opening controlled by the iris, the colored muscle that constricts or dilates based on light intensity.
- Behind the pupil is the lens, which focuses light onto the retina as an upside-down image and changes the light’s shape through accommodation.
- On the retina, transduction will occur. The rods and cones will trigger chemical changes, which will begin a chain reaction to nearby bipolar cells, which are neurons with axons on both sides. This will activate the ganglion cells, which give rise to the axons forming the optic nerve, which then sends the message to the thalamus, to the visual cortex.
- Where the optic nerve leaves the eye is a blind spot, as a result of the lack of receptor cells.
- Remember: everything tangible has a frequency. Ex: blue-black dress versus gold-white dress. It’s all about perception.
Describe what goes in our retina.
In our retina are these photoreceptors: rods and cones. Cones = color. Rods = black and white. Blood vessels and a network of interneurons make up the rest of it. Each type of cone has rhodopsin, a visual pigment that can be bleached in light to produce a response. Each receptor can produce a graded receptor potential, a tiny voltage. Since these are small and densely packed, they can produce a fine-grained ‘neural image’. Then, retinal interneurons transmit that image to the retinal ganglion cells, where they would respond to light in a small region of the retina called the cell’s receptive field.
What are sounds?
Sounds are caused by movements in the external world which create waves of pressure variation that are picked up the ear drum.
How do we detect high or low frequencies?
High frequences produce pulses that start large and become gradually smaller as they travel along. Low frequencies produce pulses that start small and become gradually larger.
How do we locate sounds?
Through interaural delay and intensity differences. Delay: Sound travels slowly and it’s is less reliable for timing cues. Ex: a sound to the left will reach the left ear before the right ear. Intensity: The head blocks sounds, and this makes it less reliable for low frequencies because the head doesn’t block those well. Finally, the pinna, or shape of the external ear, creates tiny echoes. The delay between the sound and the echo varies systematically with each direction.
Describe the whole process of how we can hear.
Vibrations in our environment are picked up by our eardrums, which then are transmitted by ossicles in the middle ear to the cochlea, the main auditory sensory organ in the inner ear. Each pulse of the cochlea causes a pulse to travel along the basilar membrane, which is crucial to excite the hair cells that act as auditory receptors. These hair cells cause action potentials in the auditory nerve. Stimuli from different directions are superimposed on each other but arrive at the ear in a single auditory stream.
What is transduction?
It’s a process in which a change of stimuli by a special cell to a chemical that our brain can read.
Describe the difference between sensation and perception, then describe what the whole sensory system is.
Sensation is concerned with the physical stimulus, while perception is concerned with interpreting those sensations in terms of the stimulus that produced them. All sense, except for the smell, is processed by the thalamus. Then, inputs are sent to cortical regions that process info. Remember: objects and events only indirectly affect our sense organs. These organs register these effects, but not the objects or events themselves.
Describe the difference between midget ganglion cells and parasol ganglion cells. Finally, what are konio cells?
Midget ganglion cells have strong lateral inhibition and are particularly sensitive to spatial change. Input is sent to the parvocellular layers and is concerned with signaling color and fine detail; blue-yellow. Parasol cells have weaker lateral inhibition, but strong delayed inhibition. Input is sent to the magnocellular layers and is concerned with signaling movement. Konio cells are between those layers, which is concerned with red-green opponent cells.
Describe the theories of color vision.
-Young Helmholtiz theory: retina contains three different color receptors, RBG. these combine to produce other colors we see. Colorblind people may lack one or two of these receptors. Monochromatic = one color; lacking two receptors. Dichromatic = two colors; lacking one receptor.
-Opponent Process Theory: depends on three sets of opposing retinal process: red-green, blue-yellow, and white-black. Ex: Some neurons are turned on by green and off by red.
