Sensory Receptors and Sensations PDF

Overview of Sensory Receptors and Sensations Learning Outcomes: 1. List the four categories of sensory receptors and describe what each responds to 2. Distinguish between perception and sensation 3. Explain the purpose of sensory adaptation Copyright © 2018 McGraw-Hill Education. All rights reserv...

Overview of Sensory Receptors and Sensations Learning Outcomes: 1. List the four categories of sensory receptors and describe what each responds to 2. Distinguish between perception and sensation 3. Explain the purpose of sensory adaptation Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 1  Overview of Sensory Receptors and Sensations, continued Sensory receptor – converts signals from the environment, called stimuli, into nerve impulses – Detect stimuli from inside and outside the body E.g., taste, smell, vision, hearing, and equilibrium E.g., some receptors respond to changes in blood pressure Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 2  Types of Sensory Receptors Sensory receptors are classified into four categories: chemoreceptors, photoreceptors, mechanoreceptors, and thermoreceptors – Chemoreceptors – respond to chemical substances E.g., taste, smell and blood pH Nociceptors (pain receptors) – type of chemoreceptor – Respond to chemicals released by damaged tissues – Protective; alert us to danger Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 3  Types of Sensory Receptors, continued Sensory receptors, cont. – Photoreceptors – respond to light – Mechanoreceptors – stimulated by mechanical forces E.g., hearing, balance, touch, pressure – Thermoreceptors – stimulated by changes in temperature; regulate body temperature Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 4  How Sensation Occurs Sensation – the conscious perception of stimuli – Occurs in the cerebral cortex – The sensation that results depends on which part of the brain receives the nerve signals Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 5 6  How Sensation Occurs, continued Sensation, cont. – Sensory adaptation – a decrease in response to a stimulus over time E.g., smelling an odor at first and later not being aware of it Sensory receptors send fewer impulses to the brain Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 7  Check Your Progress 1. Describe the functions of the four types of sensory receptors 2. Explain how perception differs from sensation, and give an example 3. Summarize the importance of sensory receptors in the maintenance of homeostasis in the body Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 8  Sense of Taste and Smell Learning Outcomes: 1. Compare and contrast the senses of taste and smell 2. Identify the structures of the tongue and the olfactory areas of the nose 3. Summarize how the brain receives taste and odor information Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 9  Sense of Taste Sense of taste – Taste buds – sensory receptors of taste Primarily located on the tongue – Humans have five main types of taste receptors: sweet, sour, salty, bitter, and umami (savory) – Nerve signals go to the parietal lobe for sensation Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 10  Sense of Smell Sense of smell – 80% of what we perceive as “taste” actually is due to the sense of smell Can’t taste well with a stuffed-up nose – Olfactory cells – found in the roof of the nasal cavity – Signals go to the temporal lobe and limbic system (for emotional responses) Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 11 12  Check Your Progress 1. Identify the structures of the tongue and nose that are involved in the senses of taste and smell 2. Summarize the pathway of sensory information regarding taste and smell from the receptors to the brain Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 13  Sense of Vision Learning Outcomes: 1. Identify the structures of the human eye 2. Explain how the eye focuses on near and far objects 3. Describe the role of photoreceptors in vision 4. Summarize the abnormalities of the eye that produce vision problems Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 14  Anatomy and Physiology of the Eye The eye – Three layers: sclera, choroid, and retina Sclera – outer layer; white – Cornea – anterior; clear Choroid – middle layer; its dark pigment absorbs light – Becomes the iris, which regulates the size of the pupil (a hole through which light enters the eye) – Forms the ciliary body, which controls the shape of the lens for focusing Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 15 16  Anatomy and Physiology of the Eye, continued The eye, cont. – The lens divides the eye into two compartments: The anterior compartment is filled with a clear, watery fluid called the aqueous humor Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 17  Anatomy and Physiology of the Eye, cont. The eye, cont. – Aqueous humor is continually produced and is drained by tiny ducts Glaucoma – the drainage ducts are blocked; aqueous humor builds up, creating pressure that compresses the arteries that serve the retina, where photoreceptors are located – Gradual loss of vision, leading to eventual total blindness Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 18  More Anatomy and Physiology of the Eye The eye, cont. – Retina - the third layer of the eye; in the posterior compartment The posterior compartment is filled with vitreous humor, which holds the retina in place Contains photoreceptors called rods and cones – Rods – very sensitive to light, but don’t detect color – Cones – require bright light, do detect color Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 19  More Anatomy and Physiology of the Eye, continued The eye, cont. – Retina, cont. Fovea centralis – packed with cone cells – When we look directly at an object, it is focused onto the fovea – Optic nerve – made of sensory fibers from the retina Takes nerve signals to the occipital lobe Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 20  Function of the Lens The cornea, lens and the humors focus images on the retina – Light rays are bent (refracted) when they are brought into focus Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 21  Function of the Lens, continued Visual accommodation – focusing – Lens changes its shape to focus light onto the retina – The shape of the lens is controlled by the ciliary body Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 22 23 24  Function of Photoreceptors, cont. Cones – located primarily in the fovea centralis – Activated by bright light – Detect fine detail and color – Three types of cones: B (blue), G (green), and R (red) – Various combinations of cones are stimulated by in-between shades of color Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 25 26  Blind Spot Blind Spot – where the optic nerve exits the eye; there are no rods and cones Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 27  Abnormalities of the Eye Abnormalities of the Eye – Color blindness One type of cone is defective or is deficient in number Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 28  Distance Vision If you can see from 20 ft what a person with normal vision can see from 20 ft, you are said to have 20/20 vision Nearsighted – can see close, can’t see far Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 29 30 31  Distance Vision, continued Farsighted – can see far; can’t see close Astigmatism – the cornea is uneven Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 32  Check Your Progress 1. Identify the structures of the eye, and provide a function of each 2. Describe the two types of photoreceptors, and state the function of each Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 33  Sense of Hearing Learning Outcomes: 1. Identify the structures of the ear that are involved in hearing 2. Describe the pathway of sensory information from the ear to the brain Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 34  Anatomy and Physiology of the Ear The ear – Has three regions: outer, middle, and inner Outer ear – consists of the pinna and the auditory canal – Auditory canal – lined with hairs and modified sweat glands that secrete earwax » Guards against the entrance of foreign matter Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 35 36  Anatomy and Physiology of the Ear, continued The ear, cont. – Middle ear – begins at the tympanic membrane Ossicles – three small bones found here – Malleus, incus and stapes Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 37  Anatomy and Physiology of the Ear, cont. The ear, cont. – Auditory tube – connects the middle ear to the throat Equalizes air pressure on each side the tympanic membrane Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 38  Anatomy and Physiology of the Ear, cont. The ear, cont. – Whereas the outer ear and the middle ear contain air, the inner ear is filled with fluid Has three areas: semicircular canals and the vestibule handle equilibrium; the cochlea handles hearing – Hair cells in the cochlea are mechanoreceptors Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 39  Path of Sound Waves and Electrical Signals The pinna channels sound waves into the auditory canal; they then strike the tympanic membrane, causing it to vibrate – This causes vibrations of the malleus, incus and then the stapes The stapes passes the pressure to the fluid within the cochlea Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 40  Check Your Progress 1. Identify the structures of the ear involved in hearing, and provide a function for each Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 41  Equilibrium Equilibrium of movement – Handled by mechanoreceptors in the semicircular canals There is one in each dimension of space Equilibrium when not moving – Handled by mechanoreceptors in the vestibule Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 42 43