5. Sensory Thresholds Vision A candle flame seen at 30 mi. on a clear, dark night Hearing The tick of a watch under quiet conditions at 20 ft. Taste One teaspoon of sugar in 2 gallons of water Smell 1 drop of perfume diffused into the entire volume of a 3 room apartment Touch The wing of a bee falling on your cheek from a height of 1 cm
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7. Stimulus – any from of energy capable of exiting the nervous system like light waves, sound waves, and the chemical energy that causes the sensation taste and smell. Receptor – is a specialized nerve ending capable of responding to energy. Senses – mechanisms which convert stimulus energy into neutral energy.
8. *Five Human Senses* 1.VISION The organ for vision is the eye. It is stimulated by light waves that strike the retina where the photo-sensitive cells- the rod and the cones- are located. The rods and cones are the receptor for vision.
11. Choroid Coat - the middle layer, a pigmented layer. It contains some of the blood vessels that supply the eye with blood. It also absorbs imperfectly focused light rays. In the front part of the eye, it becomes modified to from the iris and the cilliary blood. Pupil – the central opening of the iris
12. Iris – a circular arrangement of muscles that contract and expand to change the size of the pupil depending upon the intensity of illumination called light or dark adaptation. The color of the eye is due to the pigment in the iris Accommodation – the process when the lens become thinner to bring faraway objects into focus and thickens to focus on nearly objects.
31. Maximum level of industrial noise considered safe Characteristics of Sound Waves 20 40 60 80 100 160 0 120 180 140 Loud thunder or rock concert Pain Threshold City bus Normal conversation Subway db Noisy automobile Absolute threshold of human hearing Quiet office Whisper Rocket launch
32. Structure of the ear. The ear is divided into three parts: The outer ear - it is the visible part of the ear, composed of the pinna, the auditory canal, and the tympanic membrane commonly called eardrum.
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34. The middle ear – an air- filled chamber that is connected to the pharynx by the eustachian tube.
35. This connection of the middle ear to the pharynx serves to equalize the pressure on the two sides of the eardrum. The middle ear structure is composed of tree small bones or ossicles: the mallleus (hammer), the incus (anvil), and the stapes (stirrup). These bones are hanging into the system of levers, so that the movement of the eardrum is transmitted to a membrane called the oval window.
36. The inner ear – can find a cochlea which is a fluid- filled bony structure shaped like a snail shell. It is the organ of hearing. There are three canals in the cochlea–the cochlear canal, the tympanic canal, and the vestibular canal.
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41. 3. SMELL - The receptors for smell are found at the olfactory epithelium located at the very top of the nasal passages. -They are sensitive only to gases and to volatile substances that have been dissolved in the air.
43. 4. TASTE Much of the sensation depends on other factors-on warmth, coldness, the mild irritation caused by certain spices, and above all, on smell. When our nostrils are stuffed because of colds. Food seems almost tasteless. The tastebuds are the receptors for taste. They respond to four qualities of taste: sweet, sour, salty, and bitter.
49. 5. THE SKIN SENSES The skin has four separate senses: pain, pressure, cold, and warmth. The receptors fro the skin senses are nerve endings which come in four general forms: free nerve endings, globular bulbs, egg- shaped corpuscles, and “baskets” surrounding root hairs.
52. The Skin Senses Pressure Free nerve endings Tactile discs hair Specialized end bulbs basket cell around hair Temperature
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55. Gate-control theory of pain Direction of pain message neuro-transmitter molecules in axon of slow-pain neuron Endorphin receptor Axon of inhibitory pain gate neuron endorphin Neuron in slow-pain fiber Inhibitory pain gate neuron Stimulation of endorphin receptors inhibits firing of axon of slow-pain neuron Close-up view of inhibitory pain gates Somatosensory area of cortex Limbric system Area of pain gates Pathway of fast-pain fibers Pathway of slow-pain fibers
56. KINESTHESIS This is the sense of bodily movements. Its receptors are nerve endings found in muscles, tendons, and linings of joints. EQUILIBRIUM This is also called as the Static Sense. Two kinds of receptors give information about movements of the head and permit a sense of balance of the body.
57. These are in the semicircular canals and the vestibular canal. Both are located in the inner ear next to cochlea. THE ORGANIC SENSE This give s the result of the sensitivity of the visceral and other internal organs oft he body. Among the visceral organs are the stomach, intestines, sex structure, throat, hear and lungs.
58. PERCEPTION Chaplin defines perception as the process of knowing objects and objective events by means of senses. This sensory input consists of nerve impulses. They carry a sort of raw, undigested information about the environment. The individual must convert it into a meaningful information. Perception, then, is the organization of sensory input into meaningful experiences.
59. PERCEPTUAL CONSTANCY The perception of an object and all of its properties as constant and unchanging in spite of the continuously changing sensations of these properties outline the scope of object constancies. Our perceptual organization remains relatively stable even though some aspects of the pattern within the optical array undergo great changes.
65. * The principle of proximity – there is a tendency to perceive stimuli which are near one another as belonging together.
66. *The principle of closure – when fragmentary stimuli form enough of a familiar figure, we tend to perceive the whole figure, ignoring the missing part of parts.
67. *The principles of continuity – stimuli which from a continuous pattern are perceived as a whole, the pattern they make generally appears as a figure apart from the ground.
68. ATTENTION AND PERCEPTION Perception is selective. The direction of perception toward selected objects is called attention. A number of stimulus conditions help determine the direction of attention
69. DEPTH PERCEPTION This is the ability to see three- dimensional space and accurately judge distances. A study of perception would be incomplete without considering perceiving the third dimension- distance and depth.
There are approximately 125 million rods located outside the fovea which code information about light and dark. There are approximately 6 million cones, mostly located in the fovea, which code information about light, dark, and color. Role of rods and cones differ. 1. Rods are largely responsible for peripheral vision because of their location. 2. Rods are hundreds of times more sensitive to light, therefore, they play a more important role in vision in dim light. 3. Rods produce images that are perceived with less visual acuity than do cones. 4. Rods do not detect color as do cones.
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