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Human Biology Concepts and Current Issues Seventh Edition Michael D. Johnson 12 Sensory Mechanisms © 2014 Pearson Education, Inc. Lecture Presentations by Robert J. Sullivan Marist College Receptors Receive and Convert Stimuli Stimulus: A change in the environment – Heat, pressure, pain, touch, sound, light, chemical Receptor: a structure sensitive to a specific stimulus and converts its energy into electric signals © 2014 Pearson Education, Inc. Receptors Are Classified According to Stimulus Mechanoreceptors – Respond to mechanical stimuli – Example; respond to touch, pressure Thermoreceptors – Respond to heat or cold Pain receptors – Respond to tissue damage or excessive heat or pressure Chemoreceptors – Respond to presence of chemicals example, taste receptors Photoreceptors – Respond to light © 2014 Pearson Education, Inc. CNS Interprets Nerve Impulses Nerve impulses are transmitted from receptors to specific portions of brain Sensations are perceived in the brain, example sensation of pain, heat, cold, vision © 2014 Pearson Education, Inc. General (somatic) Sensations and Special Senses Provide Sensory Information General (somatic) sensations – Arise from sensory receptors located throughout the body – Temperature, pressure, touch, vibration, pain, of body position Special senses – Arise from sensory receptors restricted to specific areas of the body – Taste, smell, hearing, balance, vision © 2014 Pearson Education, Inc. General (somatic)Sensations Arise from Receptors Throughout the Body Somatic receptors include sensory receptors in skin, muscle, joints, ligaments Nerve impulses from general (somatic) receptors sent to the primary somatosensory area of parietal lobe of cerebral cortex Somatosensory area processes the information and perception of sensation happens here © 2014 Pearson Education, Inc. Figure 12.1 Skin receptors Hair Epidermis Merkel disks: light touch Dermis Meissner’s corpuscle: light touch Ruffini endings: pressure Pacinian corpuscle: deep pressure and highfrequency vibration Thermolight touch, and pain receptors Receptors that sense changing position of hairs Subcutaneous layer Modified and encapsulated nerve endings © 2014 Pearson Education, Inc. Unencapsulated dendritic endings Special Senses: Taste Taste buds – Chemoreceptors bind with dissolved substances – Most are distributed around edge, front, back of tongue Taste categories – – – – Sweet Salty Sour Bitter © 2014 Pearson Education, Inc. Special Senses: Smell Olfactory receptor cells – Chemoreceptors that bind with odorants – Detect 1,000 different odorants Olfactory bulb Sense of smell is perceived in the temporal lobe of the brain © 2014 Pearson Education, Inc. Olfactory epithelium Figure 12.9 Special Senses- Hearing: receptors detect sound waves Outer ear Pinna Middle ear Inner ear Incus (anvil) Malleus (hammer) Semicircular canals Vestibulocochlear nerve ( VIII) Nerve Vestibular nerve Cochlear nerve Vestibule Oval window (behind stirrup) Stapes (stirrup) Cochlea Auditory canal Tympanic membrane © 2014 Pearson Education, Inc. Round window Auditory tube The Outer Ear Pinna: visible portion of ear, directs sound waves to auditory canal Auditory canal: directs sound waves to the tympanic membrane Tympanic membrane (ear drum): separates outer ear from middle ear, vibrates in response to sound waves and passes along vibrations to the ear bones © 2014 Pearson Education, Inc. The Middle Ear Air-filled space with three small bones vibrations of tympanic membrane, passed to these three bones in sequence vibrations passed to inner ear Auditory tube (eustachian tube) – Connects to throat – Equalizes pressure © 2014 Pearson Education, Inc. The Inner Ear & hearing Bony cochlea (looks like a snail),contains a cochlear duct- has receptors for hearing which get stimulated Sound waves converted to action potentials (nerve impulses) Nerve impulses carried by VIII cranial nerve (vestibulocochlear nerve) to auditory area in the temporal lobe of the brain © 2014 Pearson Education, Inc. Inner Ear also plays an essential role in balance Vestibular apparatus Helps maintain equilibrium – Three semicircular canals and vestibule – Contain receptors for detecting changes in position of head Sensing rotational movement – Detected by receptors in semicircular canals linear movement – Detected by receptors in vestibule © 2014 Pearson Education, Inc. Inner Ear Semicircular canals for balance Cochlea (for hearing) Vestibule © 2014 Pearson Education, Inc. Eye & Vision Vision involves converting light energy to nerve impulses and transmitting them to the occipital lobe of the brain Eye ball structures – – – – – – Sclera (white of the eye) and cornea Iris, choroid lens Aqueous humor & vitreous humor Retina, macula optic nerve, optic disc © 2014 Pearson Education, Inc. Figure 12.14 Macula Fovea centralis Optic nerve Optic disk Sclera Canal of Schlemm Cornea Aqueous humor Iris Pupil Lens Vitreous humor Ciliary muscle Choroid Retina © 2014 Pearson Education, Inc. Table 12.4 © 2014 Pearson Education, Inc. Figure 12.18 Retina- contains photoreceptors: rods and cones Retina Blind spot Artery Axons of ganglion cells To optic nerve Ganglion cell layer Bipolar cell layer Rod cell and cone cell layer © 2014 Pearson Education, Inc. Vein Rod Cone Photoreceptor cells Pigmented cell layer Photoreceptors Photoreceptors contain photo pigments Rods- provide vision in dim light Contain single type of photo pigment In dim light, vision primarily dependent on rods Cones- provide color vision and accurate images Three types of cones, according to three types of photopigments- red, green, blue © 2014 Pearson Education, Inc. Disorders Otitis media Deafness Retinal detachment Cataract Glaucoma Color blindness © 2014 Pearson Education, Inc.