Lec2-basic physiology of the senses

Lec2-basic physiology of the senses - Lectures 1 and 2...

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Lectures 1 and 2- Introduction and Anatomy of the main perceptual systems Notes from chapter 5 from Gazzaniga and Heatherton for lecture 4 SENSATION- how sense organs respond to external stimuli and transmit the responses to the brain. PERCEPTION- the processing, organisation and interpretation of sensory signals that result in an internal representation of the stimulus. For example, a green light emits photons that are detected by specialized neurons in the eyes, which transmit signals to the brain ( SENSATION ). The brain processes those neural signals and the observer thinks ‘that light is green’ ( PERCEPTION ). Sensation and perception bridge the physical and psychological worlds. The brain only understands electrical impulses from neural discharges, the way our sensory organs translate a physical stimulus’ physical properties into neural impulses is called SENSORY CODING . Different features of the physical environment are coded by different neural impulses. Receptors are specialized neurons in the sense organs that pass impulses to connecting neurons where they receive some sort of physical or chemical stimulation, this is called TRANSDUCTION . After transduction in the receptors, connecting neurons in the sensory organs transmit information to the brain in the form of neural impulses. Most sensory information goes first to a structure in the middle of the brain called the THALMUS . Connecting neurons in the thalamus then conduct information to the cortex, where the brain interprets the incoming neural impulses as sight, smell, sound, touch or taste. Sensations are composed of pieces of information that are coded when stimuli are transduced into nerve impulses. Sensory coding can be divided into two categories; quantitative and qualitative. Coding for quantitative factors such as loudness, brightness is often indexed by neural firing frequency; the greater the firing sequence, the louder or brighter the stimulus. Also the number of neurons is used; more intense stimuli tend to recruit more neurons. Quantitative is not useful for colour and taste. Qualitative is used for this, with qualitative there is a recpeot type for each type of stimulus. TRANSDUCTION- a process by which sensory receptors produce neural impulses when they receive physical or chemical stimulation. ABSOLUTE THRESHOLD- the minimum intensity of stimulation that must occur before one can experience a sensation. DIFFERENCE THRESHOLD- the minimum amount of change required in order to detect a difference between intensities of stimuli.
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The stimuli, receptors and pathways for each sense SENSE STIMULUS RECEPTORS PATHWAY TO THE BRAIN Hearing Sound waves Pressure-sensitive hair cells Auditory nerve (8th cranial nerve) in the cochlea of inner ear Vision Light waves Light-sensitive rods and cones Optic nerve (2nd cranial nerve) in retina of eye Touch Pressure on the skin Sensitive ends of touch neurons in skin TRIGEMINAL nerve (5th cranial nerve) for touch above neck, spinal nerves for below
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This note was uploaded on 05/04/2008 for the course PSYCH 2006 taught by Professor Newellf during the Winter '06 term at Trinity College Dublin.

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Lec2-basic physiology of the senses - Lectures 1 and 2...

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