Psych 101 - Introduction to Psychology - Lecture 4


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Lecture 4 - Sensation.

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Psych 101 - Introduction to Psychology - Lecture 4

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  2. 2. Definitions:The detection of physical energy by our sense organs, which then relay information to the brain.The process by which our sense organs translate environmental stimulation into neural impulses to prepare it for processing by the nervous system.
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  4. 4.  The two basic requirements for all sensation are a stimulus and a receptor. ◦ Stimulus: The particular form of energy that the sense organ is designed to detect. ◦ Receptor: A sensory neuron that responds to specific stimuli such as light waves, sound waves, or chemicals in substances.
  5. 5.  To activate a sensory receptor, a stimulus must be at or above the receptors absolute threshold. Absolute threshold refers to the minimum amount of stimulus energy required to activate a receptor
  6. 6.  Sensory receptors eventually cease to respond to stimuli that are continually present. In other words, they become accustomed to the stimuli (except when they are too intense). Example: after a while you no longer notice the sensation of pressure on your skin from a watch or sock you are wearing. Sensory adaptation is essential in allowing us to focus our attention.
  7. 7.  JND refers to the smallest change in the intensity of a stimulus that we can detect. The stronger the stimulus, the greater the change needed for a change in stimulus to be noticeable. Example: Imagine how much light you would need to add to a very brightly lit room vs a dark room to notice a change in illumination.
  8. 8. The Power of Vision
  9. 9.  The stimulus detected by the visual system is light, a form of electromagnetic energy. Humans respond to a narrow range of wavelengths of light.
  10. 10. [Insert Figure JK97fig3.3.eye_structure.jpg]
  11. 11.  Cornea – a curved, transparent layer, covering the iris and pupil. It bends incoming light, focusing it at the back of the eye. Iris: The circular arrangement of smooth muscles that contract and expand to control the size of the pupil. Pupil: The opening in the iris that admits light waves into the eye.
  12. 12.  Lens: The transparent structure inside the eye that changes shape to focus images on the retina, allowing us to fine-tune the visual image. Retina: Tissue at the back of the eyeball; contains rods and cones which are the receptors for vision. ◦ Rods – allow us to see in light of low intensity; enable us to see basic shapes and forms ◦ Cones – allow us to see colour; more sensitive to detail
  13. 13.  Optic Nerve: Nerve that travels from the retina to the brain, conveying visual information.
  14. 14.  Light waves strike the cornea and pass through the pupil to the lens. The lens focuses the light waves onto the retina which contains the light-sensitive receptors. Messages from the receptors are transmitted to the brain via the optic nerve which exits at the back of the eyeball.
  15. 15.  The point at which the optic nerve exits the eye is a blind spot. No light receptors are located at this point so if an image is focused on this region, it will not be seen. Try the activity on the next slide to find your blind spot!
  16. 16.  Make a small dot on the left side of a piece of paper and a small + on the right side (as shown below), with about 6-8 inches between them. Hold the paper about 20 inches away, close your right eye and stare at the +. Slowly move the paper closer, all the time focusing on the +. After a while, the dot will disappear – this is when the dot falls on the blind spot in your left eye.
  17. 17. The Power of Hearing
  18. 18.  The stimulus detected by the auditory system is sound, a form of mechanical energy. Sound waves vary in frequency, which is measured in cycles per second, or Hertz (Hz). Humans can detect frequencies ranging form about 20 to 20,000 Hz.
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  20. 20.  Outer ear: the visible portion of the ear that collects sound waves and funnels them onto the eardrum. Eardrum: the membrane between the outer ear and the inner ear. Middle ear: an air-filled cavity containing three small bones known as the ossicles (the hammer, anvil and stirrup) which conduct vibrations.
  21. 21.  Inner ear: the part of the ear that contains the cochlea, vestibule, and semicircular canals. Cochlea – contains the receptors for sound. Auditory nerve: carries auditory information from the ear to the brain.
  22. 22.  Sound waves enter the outer ear, pass through the auditory canal, and set up vibrations of the eardrum. The three bones of the middle ear transmit the vibrations to the cochlea through its oval window. The auditory nerve carries messages from the hearing receptors inside the cochlea to the brain.
  23. 23.  The four basic tastes are sweet, salty, sour and bitter. In recent years, scientists have considered a fifth taste – umami The taste receptors are called taste buds and can be found in the bumps on the tongue (papillae) and at the back of the throat.
  24. 24. Smell (Olfaction) Olfactory epithelium: the part of the nasal passage that contains receptor cells for smell. Odorants: chemical molecules that stimulate the receptor cells for smell.When olfactory receptors come in contact withodorants, action potentials are triggered inolfactory neurons.
  25. 25.  The system that helps us to detect touch and pain is the somatosensory system. The somatosensory system responds to various types of stimuli, for example, pressure and temperature. We sense touch, temperature and pain with nerve endings located in the skin. Different parts of the body have varying degrees of sensitivity to touch.
  26. 26.  The sense of bodily position is called proprioception (or kinesthetic sense). Proprioception helps us to keep track of where we are and move efficiently. The receptors for body position are called proprioceptors, which help us to sense muscle strength and force. Two types of proprioceptors: stretch receptors located in the muscles, and force detectors embedded in the tendons.
  27. 27.  Our sense of balance or equilibrium is called the vestibular sense. It depends on hair-like receptors in the inner ears three semicircular canals and vestibular sacs.