Sensation.pptx
- 1. Sensation and Perception Sensation: your window to the world Perception: interpreting what comes in your window.
- 2. Sensations and Perceptions Sensations - the passive process of bringing information from the outside world into the body and to the brain. Perception - the active process of selecting, organizing, and interpreting the information brought to the brain by the senses
- 3. What is Sensation? A stimulus can be measured in a variety of ways including it’s size, duration, intensity, or wavelength. A Sensation occurs anytime a stimulus activates one of your receptors. The sense organs then detect any change in energy, such as light, heat, sound, and physical pressure.
- 4. What is Sensation? Sensation occurs when special receptors in the sense organs—the eyes, ears, nose, skin, and taste buds—are activated, allowing various forms of outside stimuli to become neural signals in the brain. (This process of converting outside stimuli, such as light, into neural activity is called transduction.)
- 5. Sensory systems Transduction - Communication between the brain & the rest of the body occurs via neuron. Information goes from the senses to the thalamus, then to the various areas in the brain. All senses involve something called receptor cells. Their job is to transduce (transform or even “translate”) physical stimulation/physical energy from the environment into electrochemical messages that can be understood by the brain.
- 7. Psychophysics This explains how sensation and perception are related Psychophysics: The study of the relationships between sensory experiences and the physical stimuli that cause them!
- 8. So where do vision and hearing (& the other senses) happen? The Brain! The physical energy in the environment is detected by the eyes, ears, etc. but we can’t see, hear, etc. until the brain interprets them— i.e., makes sense of them. So in a way, we see, hear, smell, etc. in our brains!
- 9. Principles of sensation • Absolute threshold • Signal detection theory • Subliminal • Difference threshold • Weber’s law • Sensory adaptation
- 10. Absolute Threshold The Absolute Threshold is the level of stimulus that produces a positive response of detection 50% of the time. the lowest level of stimulation that a person can consciously detect 50 percent of the time the stimulation is present.
- 11. The Absolute Thresholds for the “5” senses in humans are the following: 1. Vision: Seeing a candle flame 30 miles away on a clear night. 2. Hearing: Hearing a watch ticking 20 feet away. 3. Taste: Tasting 1 teaspoon of sugar dissolved into 2 gallons of water. 4. Smell: Smelling one drop of perfume in a 3 room house. 5. Touch: Feeling a bee’s wing falling a distance of one centimeter onto your cheek.
- 12. Signal detection theory Signal detection theory is a method of differentiating a person's ability to discriminate the presence and absence of a stimulus (or different stimulus intensities) from the criterion the person uses to make responses to those stimuli.
- 13. Subliminal stimuli Subliminal stimulation is sensory stimulation that is below a person's threshold for perception. It can't be seen by the naked eye or consciously heard.
- 14. Weber’s law of just noticeable differences (jnd, or the difference threshold). • The difference threshold is the amount of change needed for us to recognize that a change has occurred. • It’s the smallest difference between two stimuli that is detectable 50 percent of the time • Weber's Law states that “The larger or stronger the stimulus, the larger the change required for a person to notice that anything has happened to it.”
- 15. Sensory Adaptation Adaptation (sometimes called habituation) is a part of everyday experience. It’s a decreased responsiveness to stimuli due to constant stimulation. We are able to respond to the changes in our environment because our senses have the ability to adapt, or adjust themselves, to a constant level of stimulation. Once your senses get used to a new level of a stimulation, they respond only to deviations from it.
- 16. Examples of Adaptation 1. Your eyes eventually adjust to a darkened movie theatre. At first you see blackness, but eventually, you can see what is going on around you. 2. When you first jump into a pool that “feels cold” your body reacts to the stimulus. Eventually, your body adapts to the sensation and you become “comfortable.” 3. When you first walk into a sports locker room, the smell is almost nauseating. After a while, your senses adjust and you can hardly tell.
- 18. Sensation • Our most dominating sense. • Parts:- cornea, iris, retina, optic nerve and pupil. • Stimulated by various wavelengths of light. • The different wavelengths are responsible for the diversity of colors we see. • Light is electromagnetic radiation that travels in the form of waves. Light is emitted from the sun, stars, fire, and lightbulbs.
- 19. The Human Eye
- 20. Sensory Receptor Cells • There are two types of sensory receptor cells which are located on the retina – Rods – Cones • Rods enable us to see black and white, are more sensitive to light, and there are 100 million in each eye • Cones enable us to see color, they work best in bright light, there are 6.5 million in each eye and they are located mostly at the center of the eye
- 21. Sensory Receptor Cells • These cells transform light energy into neural impulses that are sent to various areas in the brain through the bundle of neurons called the optic nerve. • What is the place called in which the optic nerve leaves the eye? – The blind spot • Why is it called “the blind spot”? – Because there are no rods & cones on this area (there are neurons instead), images that fall on this area of the retina are not “seen”!
- 23. Hearing • Hearing depends on vibrations in the air called sound waves. • Sound waves from the air pass through various bones until they reach the inner ear, which contains tiny hair like cells that move back and forth. • These hair cells change sound vibrations into neuronal signals that travel through the auditory nerve to the brain.
- 24. Transduction in the ear Sound waves hit the eardrum then anvil then hammer then stirrup then oval window. Everything is just vibrating. Then the cochlea vibrates. The cochlea is lined with mucus called basilar membrane. In basilar membrane there are hair cells. When hair cells vibrate they turn vibrations into neural impulses which are called organ of Corti. Sent then to thalamus up auditory nerve. It is all about the vibrations!!!
- 25. Auditory defects =Deafness • There are 2 types of deafness: – 1. Conduction Deafness: occurs when anything hinders physical motion through the outer or middle ear or when the bones of the middle ear become rigid and cannot carry sounds inward. (Can be helped with a conventional hearing aid.) – 2. Sensorineural Deafness:Occurs from damage to the Cochlea, the hair cells, or the auditory neurons. (Complete Sensorineural deafness cannot be helped by a hearing aid.)
- 27. Olfactory/Smelling Sensation • Smell depends on sensory receptors that respond to airborne chemicals. • In humans, these chemoreceptors are located in the olfactory epithelium. • The olfactory epithelium is made up of three kinds of cells: -sensory neurons each with a primary cilium supporting cells between them -basal cells that divide regularly producing a fresh crop of sensory neurons to replace those that die
- 28. Disorders of olfaction: • Anosmia – inability to smell • Cacosmia – things smell like feces • Dysosmia – things smell different than they should • Hyperosmia – an abnormally acute sense of smell. • Hyposmia – decreased ability to smell • Olfactory Reference Syndrome – psychological disorder which causes the patient to imagine he or she has strong body odor • Parosmia – things smell worse than they should • Phantosmia – "hallucinated smell," often unpleasant in nature
- 29. Gustatory/Taste Sensation • Gustation - The sensation of taste – We have bumps on our tongue called papillae. – Taste buds are located on the papillae (they are actually all over the mouth).
- 30. Taste Sensation
- 31. Gustatory/Taste Sensation • Five basic tastes – Sweet – Sour – Salty – Bitter – Umami (amino acids and nucleotides)
- 32. Sense of touch/Cutaneous or skin sensation • Skin - The largest organ of your body • Our sense of touch is controlled by a huge network of nerve endings and touch receptors in the skin known as the somatosensory system. • This system is responsible for all the sensations we feel - cold, hot, smooth, rough, pressure, tickle, itch, pain, vibrations, and more.
- 33. Sensory functions • Factual experiences – pressure and pain • Thermal experiences – warmth and cold
- 34. Pain • Pain receptors are probably the most important for your safety because they can protect you by warning your brain that your body is hurt! • Pain – Motivates us to tend to injuries, to restrict activity, and to seek medical help – Teaches us to avoid pain-producing circumstances in the future