Chapter 5 Doug came to a profound conclusion... "Britney Spears is as close to a twit as you can get." Remember no class tomorrow - July 22 Exams ready on Friday July 23 - Friday devoted to test start at around 9:30 Doug dodges another question about test style.... ---------------------------------------------------------------------------- SENSATION OF PERCEPTION Sensory sytems LIE TO YOU; they lie to you constantly. Definitions: - Sensation: is a process of receiving stimulus energy from the environment. - Interaction of stimulus and receptors in the body. Eyes: Photons hit one of two receptors Cones sense color; Rods sense Black and White. - Eyes have an optic nerve that stems back to the brain. - Should the optic nerve be cut the receptor would be receiving; however it would be doing the brain no good. The photon of light must be converted to an ACTION POTENTIAL. Doug's wife's birthday was yesterday they went and ate... but not just for the Hallibut. Ears: Must convert sound waves to action potentials. Touch: Convert molecular contact into action potentials. Mouth: Changing chemcials into actiona potentials. Smell: changing more chemicals into action potentials. Transduction: The process of changing an energy type from one to another; while maintaining an anologous relationship. - more specifically for our purposes; changing sensation into action potentials. We only notice a subset of external stimuli; Ex: Frequencies beyond human hearing; radio waves; ultra violet light waves. Perception is a way of organizing information Label Line theory: any time a particular sensory system is active or your brain is active you perceive the activating receptor area's energy type. Ex: Pushing on your eye while it is closed creates a perception of light Light --> Rod --> A.P. in the optic nerve Transduction This was bottom up processing; starting with the stimuli and moving towards the system in the brain. Our frame work of beliefs can modify how we perceive external stimuli. You're in a car traveling 40 miles per hour; this seems pretty slow. However in a boat going 40 miles per hour it seems very very fast. Top down processing; starting with our perception - this can lead to illogical or erroneous receiving of reality. Receptor systems for stimuli; Light - Retinas can be divided into halves; Hemi-retina. If the hemi is close to the nose they are called the Nasal Hemi Retina. The hemi that is further from the nose is known as the Lateral Hemi Retina. - Coming out of the eye is a nerve known as the optic nerve. Some of the optic nerves cross at a location in the brain known as the optic chiasm. Neurons in the nasal hemi retina cross to the other side of the brain. Neurons in the Lateral hemi retina do not cross. They next project to the thalamus; and then the occipital cortex. - It then crosses over to the other side in the occipital cortex - Anything in the right visual field is perceived first by the left side of the brain. - Rods and Cones; primarily exist at the retina - When light hits the Rod it decreases the number of action potentials at the level of the receptor. This means at the level of the optic nerve something has to happen so that we change the reduction of neural activity into an increase. Doug questions the southern vernaculur; "you'll be on it like a pot of neck bones." - When the rod is stimulated alot it stimulates neuron B little, When neuron B is more active; the optic nerve is less active. - When neuron B is less active the Optic Nerve is more active. Doug makes a joke about ross perot; also coments about missing him in the election process. - When the optic nerve is active we perceive light. If B is less active we perceive more light; if B is more active we perceive less light. Perception is the same as activity in the optic nerve. - The O.N. is related to the perception of light. - When the rod is firing less neuron B fires more action potentials. - When the rod is firing more neuron B fires less. Inhibitory(more light inhibits receptor) More Light --> receptor activity is reduced. --> Bi-Polar cell is more active --> Optic Nerve is more active (excited) --> Perception of more light. How is your Eye lying to you? One of two ways. - The eye is geared toward allowing you to see edges better. The eye makes edges of objects appear lighter and the opposing edge seem darker. (depending on viewing angle and lighting conditions). - Critical Flicker Fusion Frequency says that your eye cannot perceive changes in a light source that is occuring faster than 16 times per second. EAR Pinna(outside ridge on the ear) --> funnels into the tympanic membrane --> then through bones known as the ossicles --> the bones causes fluid waves into the cochlea --> this stimulates scilia at the basilar membrane. Think of the basilar membrane as the ocean floor and the ocean water is the fluid surrounding the membrane. On the ocean floor is seaweed (which is representative of the scilia). The waves in the ocean water causes the seaweed to bend and move. Same thing happens in your inner ear. The waves cause the hair cells to bend in accordance with the waves. When the scilia bend that increases activity in the auditory nerve cells. Hearing range is 20 Herts to 20,000 Hertz (Or 20Khz) Frequency Theory: Faster firing of basilar membrane; higher frequency Which would account for 20 to 200 Hz. (The cell can't fire faster than 200 times per second.) Volly Principle 200 - 2000 Hz: Having different rows of scilia all firing in close proximity to give a multiplying effect to frequency theory. Place Theory 2000 - 20,000 Hz: Location along the membrane is resonsible for perception of frequency.