SENSES Chapter 18 18 1 SENSORY RECEPTORS AND
- Slides: 42
SENSES Chapter 18
18. 1 SENSORY RECEPTORS AND SENSATIONS • Sensory Receptors • Specialized to detect specific stimuli • Interoreceptors - detect stimuli inside body • Includes receptors for blood pressure, blood volume, and p. H of the blood. • Directly involved in homeostasis, regulated by negative feedback • Exteroreceptors - detect stimuli outside body • Includes receptors for taste, smell, vision, hearing, and equilibrium. • They function to inform the CNS about environmental conditions
18. 1 SENSORY RECEPTORS AND SENSATIONS • Types of Sensory Receptors • Chemoreceptors • Taste, smell, blood p. H • Photoreceptors • Vision (light) • Mechanoreceptors • Hearing, gravity, motion, body position • Thermoreceptors • Temperature • Located in the hypothalamus and skin
18. 1 SENSORY RECEPTORS AND SENSATIONS Detection Sensation
18. 1 SENSORY RECEPTORS AND SENSATIONS • How Sensation Occurs • Sensory Transduction • Energy from a chemical or physical stimulus is converted into an electrical signal (nerve impulse) • The stronger the stimulus, the more frequent the action potentials • The sensation that results depends on the part of the brain receiving the nerve impulses
18. 1 SENSORY RECEPTORS AND SENSATIONS • How Sensation Occurs • Integration: the summing up of environmental signals by sensory receptors • Sensory Adaptation: a decrease in response to a stimulus (not being consciously aware of a stimulus)
18. 2 SOMATIC SENSES • Three Types of Somatic Sensory Receptors • Proprioceptors • Cutaneous Receptors • Pain Receptors
18. 2 SOMATIC SENSES • Three Types of Somatic Sensory Receptors • Proprioceptors • Mechanoreceptors involved in reflex action • Help maintain muscle tone • Muscle spindles increase the degree of muscle contraction • Golgi tendon organs decrease the degree of muscle contraction • The result is proper muscle length and tension (tone)
MUSCLE SPINDLE
• Three Types of Somatic Sensory Receptors • Cutaneous Receptors • In the dermis of the skin • Fine touch receptors • Meissner corpuscles and Krause end bulbs - fingertips, lips, palms, penis, clitoris • Merkel disks - junction of epidermis and dermis • Root hair plexus - free nerve endings at base of follicles • Allows sensation when hair is touched • Pressure receptors • Pacinian corpuscles - onion-shaped, deep in dermis • Ruffini endings - encapsulated receptors with complex nerve networks • Temperature receptors - free nerve endings
CUTANEOUS RECEPTORS IN THE HUMAN SKIN
• Three Types of Somatic Sensory Receptors • Pain Receptors • Free nerve endings • Damaged tissues release chemicals that stimulate pain receptors • Alert us to possible danger • Referred Pain • In some areas stimulation of internal pain receptors is also perceived as pain from the skin • Most likely explanation- impulses from internal pain receptors also synapse in cord with neurons receiving pain impulses from skin • Ex: pain originating in heart is also referred to left arm and shoulder
18. 3 SENSES OF TASTE AND SMELL • Sense of Taste • Taste buds contain chemoreceptors and are located in the tongue, hard palate, pharynx, epiglottis • There are different receptors for salty, sour, bitter, and sweet tastes • Taste bud structure • Each has a pore surrounded by supporting cells and taste cells • Taste cells have microvilli with receptors • How the brain receives taste information • Chemicals bind to receptors on microvilli-impulses generated • Gustatory (taste) cortex surveys incoming pattern of impulses • “Weighted average” is the perceived taste
TASTE BUDS IN HUMANS
18. 3 SENSES OF TASTE AND SMELL • Sense of Smell • 80 -90% of what we perceive as taste is actually smell • Olfactory Cells • Chemoreceptors (modified neurons) located high in nasal cavity • Olfactory cells have a tuft of olfactory cilia with receptors for odor molecules • How the Brain Receives Odor Information • Nerve fibers lead to olfactory bulb, an extension of the brain, • A single odor is composed of many different molecules which activates a characteristic combination of receptor proteins • Odor’s “signature” is interpreted by brain
OLFACTORY CELL LOCATION AND ANATOMY
ANATOMY OF THE HUMAN EYE
ANATOMY AND PHYSIOLOGY OF THE EYE
18. 4 SENSE OF VISION • Anatomy and Physiology of the Eye • Function of the Lens • Focuses light rays onto the retina • Image is inverted and upside down on the retina • If eyeball is too long or too short corrective lenses are needed to bring image into focus on the retina • Visual accommodation • For viewing close objects • Lens rounds up to bring the image into focus on the lens • Lens shape is controlled by the ciliary muscle • Elasticity of the lens may decrease with age
18. 4 SENSE OF VISION • Visual Pathway to the Brain • Function of Photoreceptors (Rods and Cones) • Rods • Very sensitive to light, important for night vision • Visual pigment is rhodopsin • Also provide us with peripheral vision and the perception of motion • Cones • Activated by bright light • Allow for color perception
PHOTORECEPTORS IN THE EYE
• Visual Pathway to the Brain • Function of the Retina • Three Layers of Cells • Layer closest to choroid contains rods and cones • Middle layer composed of bipolar cells • Inner layer composed of ganglion cells • Sensory fibers become the optic nerve • Rod and cone cells synapse with bipolar cells which synapse with ganglion cells • Integration occurs as signals pass to bipolar and ganglion cells • Considerable processing occurs in the retina before ganglion cells generate impulses • Impulses from the ganglion cells travel in the optic nerve to the visual cortex where further integration occurs
STRUCTURE AND FUNCTION OF THE RETINA
• Visual Pathway to the Brain • From the Retina to the Visual Cortex • Optic nerves from each eye travel to the optic chiasma • Some of the axons cross over at the optic chiasma • Fibers from the right half of each retina join together to form the right optic tract • Fibers from the left half of each retina join together to form the left optic tract • Optic tracts travel around the hypothalamus and most fibers synapse with nuclei in the thalamus • Axons from the thalamic nuclei form optic radiations that carry impulses to the visual area • Right and left visual areas must communicate for us to see entire visual field
18. 5 SENSE OF HEARING • The Ear Has Two Sensory Functions • Hearing and Balance • Mechanoreceptors (hair cells) located in the inner ear associated with both functions
ANATOMY OF THE HUMAN EAR
18. 5 SENSE OF HEARING • Auditory Pathway to the Brain • Sound waves enter the auditory canal • Tympanic membrane (ear drum) begins to vibrate • Vibrations are amplified across the middle ear bones • The stapes is attached to the oval window • Oval window vibrates and transmits vibrations to fluid inside the cochlea
MECHANORECEPTORS FOR HEARING
18. 5 SENSE OF HEARING • Auditory Pathway to the Brain Continued. . . • Stapes causes the oval window to vibrate • Vibrations move from the vestibular canal to the tympanic canal across the basilar membrane • Basilar membrane moves up and down and the stereocilia of the hair cells bend • This generates nerve impulses in the cochlear nerve • The nerve impulses travel to the brain • The auditory cortex interprets them as sound
• Rotational Equilibrium Pathway • Three semicircular canals arranged so that one is in each plane of motion • Each semicircular canal has an enlarged base called an ampulla • Each ampulla contains hair cells with stereocilia embedded in a cupula • As fluid within a canal flows and bends a cupula, the stereocilia are bent and this changes the pattern of impulses carried in the vestibular nerve to cerebellum and cerebrum • Brain uses this information to make postural corrections
• Gravitational Equilibrium Pathway • Depends on utricle and saccule • Utricle is sensitive to horizontal movements of the head • Saccule is sensitive to vertical movements of the head • Both contain hair cells with stereocilia embedded in an otolithic membrane • Large central cilium called the kinetocilium • Calcium carbonate granules (otoliths) rest on otolithic membrane • When head or body moves in horizontal or vertical plane the otoliths are displaced and the otolithic membrane sags
18. 7 DISORDERS THAT AFFECT THE SENSES • Disorders of Taste and Smell • Sense of smell begins to decline after age 60 • Some people are born without a sense of smell • Other factors that contribute to a decrease in the ability to taste and/or smell include: • Upper respiratory infections • Allergies • Exposure to certain drugs or chemicals (including tobacco smoke) • Brain trauma
18. 7 DISORDERS THAT AFFECT THE SENSES • Disorders of the Eye • Color Blindness • Complete colorblindness is rare • Most common types involve deficiency in one type of cone • Red-green colorblindness • Most common type • X-linked recessive trait • 5 -8% of the male population
TESTING FOR COLORBLINDNESS
18. 7 DISORDERS THAT AFFECT THE SENSES • Distance Vision • Nearsighted • Can see close objects better than distant ones • Eyeball is elongated so image is brought to point focus in front of the retina • Corrected by concave lenses which diverge light rays so point focus is farther back • Farsighted • Can see distant objects better than close ones • Eyeball is shortened so image is brought to point focus behind the lens • Corrected by convex lenses to increase bending of light rays so point focus is farther forward
CORRECTIVE ABNORMALITIES OF THE EYE AND POSSIBLE CORRECTIVE LENSES
• Common Causes of Blindness • Retinal Disorders • Capillaries to the retina may become damaged • Macular Degeneration • Cones are destroyed • Detached retina • Glaucoma • Fluid builds up in the eye destroying nerve fibers associated with peripheral vision • Cataracts • Cloudy spots on the lens • Exposure to UV light, diabetes, heavy alcohol consumption, and smoking are all risk factors
18. 7 DISORDERS THAT AFFECT THE SENSES • Disorders of Hearing and Equilibrium • Hearing Loss • Mobility of the middle ear bones decreases with age • The ability to hear high-pitched sounds is affected first. • Sudden Deafness • Usually occurs in only one ear • Causes include infections, trauma, and side effects of some drugs • Sometimes resolves itself • Deafness at Birth • Genetic and/or environmental causes (pathogens)
18. 7 DISORDERS THAT AFFECT THE SENSES • Disorders of Hearing and Equilibrium • Vertigo (dizziness) • Can be caused by problems in the brain or inner ear • Meniere’s Disease • Caused by an increased fluid volume in the inner ear • Hearing loss and vertigo are both characteristics of this condition
- Distinguish between general senses and special senses.
- General senses vs special senses
- Classification of sensory receptors
- Where does transduction occur in the ear
- Classification of sensory receptors
- Sensory receptors in the eye
- Exteroceptors examples
- Classification of sensory receptors
- Dermatome
- Sensory receptors
- Proprioceptors
- Names of parts of ear
- Thermoreceptors
- Chapter 11 special senses the eyes and ears
- Anatomy and physiology chapter 8 special senses
- The general and special senses chapter 9
- Chapter 17 special senses answer key
- Eye anatomy
- Chapter 10 special senses
- Chapter 15 special senses
- Chapter 15 special senses
- Adrenergic vs cholinergic
- Orbelli phenomenon
- Difference between ionotropic and metabotropic receptors
- Muscarinic adrenergic receptors
- Nicotinic vs muscarinic
- Five elements and five senses
- The chemical senses taste and smell review worksheet
- Kinesthetic and vestibular senses
- Cranial nerve function mnemonic
- In your notebook identify the function of each
- Ear bone structure
- Somatic senses
- Special senses the eyes and ears
- Chapter 53 care of the patient with a sensory disorder
- Sensory evaluation cryptogram answers
- What is taste bias
- The thinness or thickness of a product
- Tuberous receptors
- Olfactory receptors
- Sensory coding
- Receptive fields of sensory neurons
- 3 types of lung receptors