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Chapter7 Power Point Lecture
 

Chapter7 Power Point Lecture

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Chapter7 Power Point Lecture Chapter7 Power Point Lecture Presentation Transcript

  • Chapter 7 The Other Sensory Systems
  • Audition
    • Our senses have evolved to allow us to detect and interpret biologically useful information from our environment .
    • However, we do not detect all sensory information in the world.
    • Some sensory information lies beyond our ability to detect it.
    • We also tend to focus on information that is important or relevant.
  • Audition
    • Audition refers to our sense of hearing.
    • Audition depends upon our ability to detect sound waves.
    • Sound waves are periodic compressions of air, water or other media.
    • Sound waves are “transduced” into action potentials sent to the brain.
  • Audition
    • The amplitude refers to the height and subsequent intensity of the sound wave.
    • Loudness refers to the perception of the sound wave.
      • Amplitude is one factor.
    • Frequency refers to the number of compressions per second and is measured in hertz.
      • Related to the pitch (high to low) of a sound.
  • Fig. 7-1, p. 196
  • Audition
    • Anatomist distinguish between:
      • The outer ear
      • The middle ear
      • The inner ear
  • Audition
    • The outer ear includes the pinna and is responsible for:
      • Altering the reflection of sound waves into the middle ear from the outer ear.
      • Helping to locate the source of a sound.
  • Audition
    • The middle ear contains the tympanic membrane which vibrates at the same rate when struck by sound waves.
    • Three tiny bones (malleus, incus, & stapes) transmit information to the oval window or a membrane in the middle ear.
  • Fig. 7-2, p. 197
  • Audition
    • The inner ear contains a snail shaped structure called the cochlea which contains three fluid-filled tunnels (scala vestibuli, scala media, and the scala tympani).
    • Hair cells are auditory receptors that excite the cells of the auditory nerve when displaced by vibrations in the fluid of the cochlea.
      • Lie between the basilar membrane and the tectorial membrane in the cochlea.
  • Fig. 7-3, p. 198
  • Audition
    • Pitch perception can be explained by the following theories:
    • Frequency theory - the basilar membrane vibrates in synchrony with the sound and causes auditory nerve axons to produce action potentials at the same frequency.
    • Place theory - each area along the basilar membrane is tuned to a specific frequency of sound wave.
  • Fig. 7-4, p. 199
  • Audition
    • The current pitch theory combines modified versions of both the place theory and frequency theory :
      • Low frequency sounds best explained by the frequency theory.
      • High frequency sounds best explained by place theory.
  • Audition
    • Volley principle states that the auditory nerve can have volleys of impulses (up to 4000 per second) even though no individual axon approaches that frequency by itself.
      • provides justification for the place theory and
  • Audition
    • The primary auditory cortex is the ultimate destination of information from the auditory system.
      • Located in the superior temporal cortex.
    • Each hemisphere receives most of its information from the opposite ear.
  • Audition
    • The superior temporal cortex contains area MT which allows for the detection of the location of sound.
    • Area A1 of the brain is important for auditory imagery.
    • The auditory cortex requires experience to develop properly.
      • Auditory axons develop less in those who are deaf from birth.
  • Fig. 7-5, p. 200
  • Audition
    • The cortex is necessary for the advanced processing of hearing.
      • Damage to A1 does not necessarily cause deafness unless damage extends to the subcortical areas.
    • The auditory cortex provides a tonotopic map in which cells in the primary auditory cortex are more responsive to preferred tones.
      • Some cells respond better to complex sounds than pure tones.
  • Fig. 7-6, p. 201
  • Audition
    • Areas around the primary auditory cortex exist in which cells respond more to changes in sound.
    • Cells outside A1 respond to auditory “objects” (animal cries, machinery noise, music, etc.).
      • Because initial response is slow, most likely responsible for interpreting the meaning of sounds.
  • Audition
    • About 99% of hearing impaired people have at least some response to loud noises.
    • Two categories of hearing impairment include:
      • Conductive or middle ear deafness.
      • Nerve deafness.
  • Audition
    • Conductive or middle ear deafness occurs if bones of the middle ear fail to transmit sound waves properly to the cochlea.
    • Caused by disease, infections, or tumerous bone growth near the middle ear.
    • Can be corrected by surgery or hearing aids that amplify the stimulus.
    • Normal cochlea and normal auditory nerve allows people to hear their own voice clearly.
  • Audition
    • Nerve or inner-ear deafness results from damage to the cochlea, the hair cells or the auditory nerve.
    • Can be confined to one part of the cochlea.
      • people can hear only certain frequencies.
    • Can be inherited or caused by prenatal problems or early childhood disorders (rubella, syphilis, inadequate oxygen to the brain during birth, repeated exposure to loud noises, etc).
  • Audition
    • Tinnitus is a frequent or constant ringing in the ears.
      • experienced by many people with nerve deafness.
    • Sometimes occurs after damage to the cochlea.
      • axons representing other part of the body invade parts of the brain previously responsive to sound.
      • Similar to the mechanisms of phantom limb.
  • Audition
    • Sound localization depends upon comparing the responses of the two ears.
    • Humans localize low frequency sound by phase difference and high frequency sound by loudness difference.
  • Audition
    • Three mechanisms:
      • High-frequency sounds (2000 to 3000Hz) create a “sound shadow”, making the sound louder for the closer ear.
      • The difference in the time of arrival at the two ears is most useful for localizing sounds with sudden onset.
      • Phase difference between the ears provides cues to sound location for localizing sounds with frequencies up to 1500 Hz.
  • Fig. 7-7, p. 202
  • Fig. 7-8, p. 203
  • Fig. 7-9, p. 203
  • The Mechanical Senses
    • The mechanical senses include:
      • The vestibular sensation
      • Touch
      • Pain
      • Other body sensations
    • The mechanical senses respond to pressure, bending, or other distortions of a receptor.
  • The Mechanical Senses
    • The vestibular sense refers to the system that detects the position and the movement of the head.
      • Directs compensatory movements of the eye and helps to maintain balance.
    • The vestibular organ is in the ear and is adjacent to the cochlea.
  • The Mechanical Senses
    • The vestibular organ consists of two otolith organs (the saccule and untricle) and three semicircular canals.
    • The otolith organs have calcium carbonate particles (otoliths) that activate hair cells when the head tilts.
    • The 3 semicircular canals are oriented in three different planes and filled with a jellylike substance that activates hair cells when the head moves.
  • Fig. 7-10, p. 206
  • The Mechanical Senses
    • The vestibular sense is integrated with other sensations by the angular gyrus.
      • Angular gyrus is an area at the border between the parietal and temporal cortex.
  • The Mechanical Senses
    • The somatosensory system refers to the sensation of the body and its movements.
      • Includes discriminative touch, deep pressure, cold warmth, pain, itch, tickle and the position and movement of the joints.
    • Touch receptors may be simple bare neurons, an elaborated neuron ending, or a bare ending surrounded by non-neural cells that modify its function.
  • Fig. 7-11, p. 207
  • The Mechanical Senses
    • The pacinian corpuscle is a type of touch receptor that detects sudden displacement or high-frequency vibrations on the skin.
    • Mechanical pressure bend the membrane.
      • increases the flow of sodium ions and triggers an action potential.
  • Fig. 7-12, p. 207
  • The Mechanical Senses
    • Information from touch receptors in the head enters the CNS through the cranial nerves.
    • Information from receptors below the head enter the spinal cord and travel through the 31 spinal nerves to the brain.
  • Fig. 7-13, p. 208
  • The Mechanical Senses
    • Each spinal nerve has a sensory component and a motor component and connects to a limited area of the body.
    • A dermatome refers to the skin area connected to a single sensory spinal nerve.
    • Sensory information entering the spinal cord travel in well-defined and distinct pathways.
      • Example: touch pathway is distinct from pain pathway.
  • Fig. 7-14, p. 208
  • The Mechanical Senses
    • Various aspects of body sensations remain partly separate all the way to the cortex.
    • Various areas of the thalamus send impulses to different areas of the somatosensory cortex located in the parietal lobe.
    • Different sub areas of the somatosensory cortex respond to different areas of the body.
    • Damage to the somatosensory cortex can result in the impairment of body perceptions.
  • The Mechanical Senses
    • Pain depends on several types of axons, several neurotransmitters, and several brain areas.
    • Mild pain triggers the release of glutamate while stronger pain triggers the release of glutamate and substance P .
      • Substance P results in the increased intensity of pain.
      • Morphine and opiates block pain by blocking these neurotransmitters.
  • Fig. 7-15, p. 210
  • The Mechanical Senses
    • Opioid mechanisms are systems that are sensitive to opioid drugs and similar chemicals.
    • Activating opiate receptors blocks the release of substance P in the spinal chord and in the periaqueductal grey of the midbrain.
    • Enkephalins refer to opiate-type chemical in the brain.
    • Endorphins - group of chemicals that attach to the same brain receptors as morphine.
  • Fig. 7-16, p. 211
  • The Mechanical Senses
    • Discrepancy in pain perception can partially be explained by genetic differences in receptors.
    • Gate theory suggests that the spinal cord areas that receive messages from pain receptors also receive input from other skin receptors and from axons descending from the brain.
      • These other areas that provide input can close the “gates” and decrease pain perception.
  • The Mechanical Senses
    • Special heat receptors account for the pain associated with a burn.
    • Heat receptors can also be activated by acids.
    • Capsaicin is a chemical found in hot peppers that directly stimulates these receptors and also triggers an increase in the release of substance P.
  • The Mechanical Senses
    • Pain activates the hypothalamus, amygdala, and cingulate cortex.
      • results in an emotional component to pain.
    • A placebo is a drug or other procedure with no pharmacalogical effect.
    • Placebo’s decrease pain perception by decreasing the brains emotional response to pain perception and not the sensation itself.
  • Fig. 7-17, p. 211
  • The Mechanical Senses
    • Mechanisms of the body to increase sensitivity to pain include:
      • Damaged or inflamed tissue releases histamine, nerve growth factor, and other chemicals that increase the number of sodium gates in nearby pain receptors.
        • Pain responses are thus magnified.
      • Certain receptors become potentiated after an intense barrage of painful stimuli.
        • leads to increased sensitivity or chronic pain later.
  • The Mechanical Senses
    • Pain is best controlled by preventing the brain from being bombarded with pain messages.
    • Bombarding the brain with pain messages results in the increased sensitivity of the pain nerves and their receptors.
  • The Mechanical Senses
    • Morphine and other opiates are the primary drugs for controlling serious pain.
    • Morphine inhibits slow, dull pain carried by thin unmyelinated axons.
      • Sharp pain is conveyed by thicker myelinated axons.
      • Not influenced by morphine and endorphins.
    • Ibuprofen, an anti-inflammatory drug, controls pain by reducing the release of chemicals from damaged tissues.
  • The Mechanical Senses
    • The release of histamines by the skin produce itching sensations.
    • The release of histamine by the skin activates a distinct pathway in the spinal cord to the brain.
    • Impulses travel slowly along this pathway (half a meter per second).
    • Pain and itch have an inhibitory relationship.
      • Opiates increase itch while antihistamines decrease itch.
  • The Chemical Senses
    • Coding in the sensory system could theoretically follow:
      • The labeled-line principle in which each receptor responds to a limited range of stimuli and sends a direct line to the brain.
      • Across-fiber pattern in which each receptor responds to a wider range of stimuli and contributes to the perception of each of them.
  • The Chemical Senses
    • Vertebrate sensory systems probably have no pure label-lined codes.
    • The brain gets better information from a combination of responses.
      • Example: auditory perception and color perception both rely on label-lined codes.
    • Taste and smell stimuli activate several neurons and the meaning of the response of a single neuron depends on the context of responses by other neurons.
  • The Chemical Senses
    • Taste refers to the stimulation of the taste buds.
    • Our perception of flavor is the combination of both taste and smell.
      • Taste and smell axons converge in the endopiriform cortex.
  • The Chemical Senses
    • Receptors for taste are modified skin cells.
    • Taste receptors have excitable membranes that release neurotransmitters to excite neighboring neurons.
    • Taste receptors are replaced every 10 to 14 days.
  • The Chemical Senses
    • Papillae are structures on the surface of the tongue that contain the taste buds.
    • Each papillae may contain zero to ten taste buds.
    • Each taste bud contains approximately 50 receptors.
    • Most taste buds are located along the outside of the tongue in humans.
  • Fig. 7-18, p. 217
  • The Chemical Senses
    • Procedures that alter one receptor but not others can be used to identify taste receptors.
    • Adaptation refers to reduced perception of a stimuli due to the fatigue of receptors.
    • Cross-adaptation refers to reduced response to one stimuli after exposure to another.
  • The Chemical Senses
    • Western societies have traditionally described sweet, sour, salty and bitter tastes as the “primary” tastes and four types of receptors.
    • Evidence suggests a fifth type of glutamate receptor.
  • The Chemical Senses
    • The saltiness receptor permits sodium ions to cross the membrane.
      • results in an action potential.
    • Sourness receptors close potassium channels when acid binds to receptors.
      • results in depolarization of the membrane.
    • Sweetness, bitterness, and umami receptors activate a G protein that releases a second messenger in the cell when a molecule binds to a receptor.
  • The Chemical Senses
    • Different chemicals also result in different temporal patterns of action potentials and activity in the brain.
    • Taste is a function of both the type of cell activity, as well as the rhythm of cell activity.
  • The Chemical Senses
    • Bitter receptors are sensitive to a wide range of chemicals with varying degrees of toxicity.
      • Over 40 types of bitter receptors exist.
    • Most taste cells contain only a small number of these receptors.
    • We are sensitive to a wide range of harmful substances, but not highly sensitive to any single one.
  • The Chemical Senses
    • Taste coding in the brain depends upon a pattern of responses across fibers in the brain.
    • The brain determines taste by comparing the responses of several types of taste neurons.
    • Receptors converge their input onto the next cells in the taste system.
    • Cells thus respond best to a particular taste but others as well.
  • The Chemical Senses
    • Different nerves carry taste information to the brain from the anterior two-thirds of the tongue than from the posterior tongue and throat.
    • Taste nerves project to a structure in the medulla known as the nucleus of the tractus solitarius (NTS).
      • projects information to other parts of the brain.
  • Fig. 7-19, p. 219
  • The Chemical Senses
    • Various areas of the brain are responsible for processing different taste information.
      • The somatosensory cortex responds to the touch aspect of taste.
      • The insula is the primary taste cortex.
    • Each hemisphere of the cortex is also responsive to the ipsilateral side of the tongue.
  • The Chemical Senses
    • Genetic factors and hormones can account for some differences in taste sensitivity.
    • Variations in taste sensitivity are related to the number of fungiform papillae near the tip of the tongue.
    • Supertasters have higher sensitivity to all tastes and mouth sensations in general.
  • Fig. 7-20, p. 220
  • The Chemical Senses
    • Olfaction is the sense of smell and refers to the detection and recognition of chemicals that contact the membranes inside the nose.
    • Olfaction is more subject to adaptation than our other senses.
    • Olfactory cells line the olfactory epithelium in the rear of the nasal passage and are the neurons responsible for smell.
  • Fig. 7-21, p. 221
  • The Chemical Senses
    • Olfactory receptors are located on cilia which extend from the cell body into the mucous surface of the nasal passage.
    • Vertebrates have hundreds of olfactory receptors which are highly responsive to some related chemicals and unresponsive to others.
    • Olfaction processes a wide variety of airborne chemicals, hence the need for many different types of receptors.
  • The Chemical Senses
    • Proteins in olfactory receptors respond to chemicals outside the cells and trigger changes in G protein inside the cell.
    • G protein then triggers chemical activities that lead to action potentials.
  • Fig. 7-22, p. 222
  • The Chemical Senses
    • Axons from olfactory receptors carry information to the olfactory bulb in the brain.
    • Coding in the brain is determined by which part of the olfactory bulb is excited.
    • Chemicals excite limited parts of the olfactory bulb with similar chemicals exciting similar parts.
  • The Chemical Senses
    • The olfactory bulb sends axons to the cerebral cortex where messages are coded by location.
    • The cortex connects to other areas that control feeding and reproduction.
      • Both behaviors are highly influenced by smell.
  • Olfaction
    • Olfactory receptors are replaced approximately every month, but are subject to permanent impairment from massive damage.
    • Anosmia refers to a general lack of olfaction.
    • Specific anosmia refers to the inability to smell a single type of chemical.
  • The Chemical Senses
    • Individual differences in olfaction exist regarding olfaction.
    • Women detect odor more readily than men and brain responses are stronger.
    • The ability to attend to a faint odor and become more sensitive to it is characteristic of young adult women and thus seems to be influenced by hormones.
  • The Chemical Senses
    • The vomeronasal organ (VNO) is a set of receptors located near the olfactory receptors that are sensitive to pheromones.
    • Pheromones are chemicals released by an animal to affect the behavior of others of the same species.
  • The Chemical Senses
    • The VNO and pheromones are important for most mammals, but less so for humans.
    • The VNO is tiny in human adults and has no receptors.
    • Humans unconsciously respond to some pheromones through receptors in the olfactory mucosa.
      • Example: synchronization of menstrual cycle’s in women.
  • The Chemical Senses
    • Synesthesia is the experience of one sense in response to stimulation of a different sense.
      • Estimates suggest 1 in every 500 people (Day, 2005).
    • fMRI case studies show activity in both the auditory and visual cortex responsive to color when exposed to spoken language.
      • Suggests some axons from one area have branches to other cortical regions.