Power Point Lecture Slides prepared by Vince Austin
Power. Point® Lecture Slides prepared by Vince Austin, University of Kentucky General Senses Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings 13 c
Peripheral Nervous System (PNS) § PNS – all neural structures outside the brain and spinal cord § Includes sensory receptors, peripheral nerves, associated ganglia, and motor endings § Provides links to and from the external environment Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Sensory Receptors § Structures specialized to respond to stimuli § Activation of most sensory receptors results in depolarizations (electrical activations) that trigger impulses to the CNS § The realization of these stimuli, sensation and perception, occur in the brain Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
From Sensation to Perception § Survival depends upon sensation and perception § Sensation is the biological awareness of changes in the internal and external environment § Perception is the conscious interpretation of those stimuli Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Receptor Classification by Location 1. exteroreceptors - respond to external environment 2. enteroreceptors - respond to internal environment 3. proprioreceptors - respond to body position/motion Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Receptor Class by Location: Exteroceptors § Respond to stimuli arising outside the body § Found near the body surface § Sensitive to touch, pressure, pain, and temperature § Include the special sense organs Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Receptor Class by Location: Interoceptors § Respond to stimuli arising within the body (p. H, CO 2, salts) § Found in internal viscera and blood vessels § Sensitive to chemical changes, stretch, and temperature changes Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Receptor Class by Location: Proprioceptors § Respond to degree of stretch of the organs they occupy § Found in skeletal muscles, tendons, joints, ligaments, and connective tissue coverings of bones and muscles § Constantly “advise” the brain of one’s movements Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Receptor Classification by Stimulus Type 1. mechanoreceptors - any mechanical deviation a. touch, pressure, vibration, proprioception etc. 2. thermoreceptors - changes in temperature 3. nocireceptors - pain; physical or chemical damage 4. photoreceptors - light; rods & cones of the eye 5. chemoreceptors - shapes of different molecules a. taste, smell, chemicals of blood Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Simple Receptors § Meissner’s corpuscles § Pacinian corpuscles § Muscle spindles § Golgi tendon organs § Ruffini’s corpuscles Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Simple Receptors: Unencapsulated Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Table 13. 1. 1
Simple Receptors: Encapsulated Table 13. 1. 2 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Simple Receptors: Encapsulated Table 13. 1. 3 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Adaptation of Sensory Receptors Adaptation occurs when sensory receptors are subjected to an unchanging stimulus § Receptor membranes become less responsive § Receptor potentials decline in frequency or stop § Receptors responding to pressure, touch, and smell adapt quickly § Pain receptors and proprioceptors do not exhibit adaptation Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Power. Point® Lecture Slides prepared by Vince Austin, University of Kentucky Special Senses Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings 15
I. Chemical Senses Chemical senses – gustation (taste) and olfaction (smell) Their chemoreceptors respond to chemicals in aqueous solution § Taste – to substances dissolved in saliva § Smell – to substances dissolved in fluids of the nasal membranes Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Taste Buds § Most of the 10, 000 or so taste buds are found on the tongue § Taste buds are found in papillae of the tongue mucosa § Papillae come in three types: filiform, fungiform, and circumvallate § Fungiform and circumvallate papillae contain taste buds Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Taste Buds Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 15. 1
Gustatory Pathway Figure 15. 2 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Influence of Other Sensations on Taste § Taste is 80% smell § Thermoreceptors, mechanoreceptors, nociceptors also influence tastes § Temperature and texture enhance or detract from taste Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Sense of Smell Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 15. 3
II. Eye and Associated Structures - 70% of all sensory receptors are in the eye - Most of the eye is protected by a cushion of fat and the bony orbit Accessory structures include: § eyebrows § eyelids § conjunctiva § lacrimal apparatus § extrinsic eye muscles Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Palpebrae (Eyelids) 1 2 3 4 5 6 7 8 9 Figure 15. 5 b Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Conjunctiva Transparent membrane that: § Lines the eyelids as the palpebral conjunctiva § Covers the whites of the eyes as the ocular conjunctiva § Lubricates and protects the eye Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Lacrimal Apparatus - Consists of the lacrimal gland associated ducts - Lacrimal glands secrete tears Tears: § Contain mucus, antibodies, and lysozyme § Enter the eye via superolateral excretory ducts § Exit the eye medially via the lacrimal punctum § Drain into the nasolacrimal duct Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Lacrimal Apparatus 1 2 3 4 5 6 Figure 15. 6 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Extrinsic Eye Muscles § Six straplike extrinsic eye muscles § Enable the eye to follow moving objects § Maintain the shape of the eyeball § Four rectus muscles originate from the annular ring § Two oblique muscles move the eye in the vertical plane Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Extrinsic Eye Muscles Figure 15. 7 a, b Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Summary of Cranial Nerves and Muscle Actions § Names, actions, and cranial nerve innervation of the extrinsic eye muscles Figure 15. 7 c Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Structure of the Eyeball § A slightly irregular hollow sphere with anterior and posterior poles § The wall is composed of three tunics – fibrous, vascular, and sensory § The internal cavity is filled with fluids called humors § The lens separates the internal cavity into anterior and posterior segments (chambers) Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Structure of the Eyeball 9 1 10 2 11 3 4 12 5 13 6 7 8 14 Figure 15. 8 a Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
A. Fibrous Tunic Forms the outermost coat of the eye and is composed of: § Opaque and white sclera (posteriorly) § Clear cornea (anteriorly) § The sclera protects the eye and anchors extrinsic muscles § The cornea lets light enter the eye Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
B. Vascular Tunic (Uvea) Has three regions: choroid, ciliary body, and iris 1. Choroid region: § A dark brown membrane that forms the posterior portion of the uvea § Supplies blood to all eye tunics Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
2. Ciliary body: § A thickened ring of tissue surrounding the lens § Composed of smooth muscle bundles (ciliary muscles) § Anchors the suspensory ligament that holds the lens in place Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
3. Iris: § The colored part of the eye § Pupil – central opening of the iris - Regulates the amount of light entering the eye during: -- Close vision and bright light – pupils constrict -- Distant vision and dim light – pupils dilate Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Pupil Dilation and Constriction Figure 15. 9 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
C. Sensory Tunic: Retina: A delicate two-layered membrane 1. Pigmented layer – the outer layer that absorbs light and prevents its scattering 2. Neural layer - which contains: § photoreceptors that transduce light energy § bipolar cells § ganglion cells § amacrine and horizontal cells Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Sensory Tunic: Retina Figure 15. 10 a Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
The Retina: Ganglion Cells and the Optic Disc § Ganglion cell axons leave the eye as the optic nerve The optic disc: § Is the site where the optic nerve leaves the eye § Lacks photoreceptors (the blind spot) Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
The Retina: Ganglion Cells and the Optic Disc Figure 15. 10 b Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
The Retina: Photoreceptors Rods: § Respond to dim light § Are used for peripheral vision Cones: § Respond to bright light § Have high-acuity color vision § Are found in the macula lutea § Are concentrated in the fovea centralis Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Cones and Rods Figure 15. 10 a Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Rods Functional characteristics: § Sensitive to dim light and best suited for night vision § Absorb all wavelengths of visible light § Sum of visual input from many rods feeds into a single ganglion cell § Results in fuzzy and indistinct images Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Cones Functional characteristics: § Need bright light for activation (have low sensitivity) § Have pigments that furnish a vividly colored view § Each cone synapses with a single ganglion cell § Vision is detailed and has high resolution Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Inner Chambers and Fluids - The lens separates the internal eye into anterior and posterior segments - The posterior segment is filled with a clear gel called vitreous humor that: § Transmits light § Supports the posterior surface of the lens § Holds the neural retina firmly against the pigmented layer § Contributes to intraocular pressure Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Anterior Segment Composed of two chambers: § Anterior – between the cornea and the iris § Posterior – between the iris and the lens § Aqueous humor § A plasma like fluid that fills the anterior segment § Drains via the canal of Schlemm § Supports, nourishes, and removes wastes Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Anterior Segment Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 15. 12
Lens § A biconvex, transparent, flexible, avascular structure that: - Allows precise focusing of light onto the retina § Lens epithelium – anterior cells that differentiate into lens fibers § With age, the lens becomes more compact and dense and loses its elasticity Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Visual Pathways Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 15. 23
Visual Pathways § Ganglion cells of the retina make up optic nerves § Left and right optic nerves (II) into brain via optic foraminae § Optic chiasma (nasal side fibers cross to contralateral brain) § Optic tracts (carry fibers back to the thalamsus) § Ganlion cell axons terminate in lateral geniculate n. of thalamus § Optic radiations carry fibers back to occipital cortex (Area 17) Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
The Ear: Hearing and Balance The three parts of the ear are the inner, outer, and middle ear § The outer and middle ear are involved with hearing § The inner ear functions in both hearing and equilibrium § Receptors for hearing and balance: - Respond to separate stimuli - Are activated independently Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Outer Ear The auricle (pinna) is composed of: § The helix (rim) § The lobule (earlobe) External auditory canal § Short, curved tube Tympanic membrane (eardrum) § Thin connective tissue membrane that vibrates in response to sound § Transfers sound energy to the middle ear ossicles § Boundary between outer and middle ears Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
A. External Ear Figure 15. 25 a Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
B. Middle Ear § A small, air-filled, mucosa-lined cavity § Flanked laterally by the eardrum § Flanked medially by the oval and round windows of the cochlea § Pharyngotympanic tube – connects the middle ear to the nasopharynx - Equalizes pressure in the middle ear cavity with the external air pressure Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Middle Ear (Tympanic Cavity) Figure 15. 25 b Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Ear Ossicles The tympanic cavity contains three small bones: the malleus, incus, and stapes § Transmit vibratory motion of the eardrum to the oval window § Dampened by the tensor tympani and stapedius muscles Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Ear Ossicles Figure 15. 26 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Inner Ear Bony labyrinth: § Tortuous channels worming their way through the temporal bone § Contains the cochlea, the vestibule, and the semicircular canals § Filled with perilymph Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Inner Ear Figure 15. 27 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
The Vestibule The central egg-shaped cavity of the bony labyrinth § Suspended in its perilymph are two sacs: the saccule and utricle § The saccule extends into the cochlea § The utricle extends into the semicircular canals These sacs: § House equilibrium receptors called maculae § Respond to gravity and changes in the position of the head, especially linear movements Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
The Semicircular Canals Three canals that each define two-thirds of a circle and lie in the three planes of space § Membranous semicircular ducts line each canal and communicate with the utricle § The ampulla is the swollen end of each canal and it houses equilibrium receptors in a region called the crista ampullaris - These receptors respond to angular movements of the head Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
The Semicircular Canals Figure 15. 27 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
The Cochlea § A spiral, conical, bony chamber that: § Extends from the anterior vestibule § Contains the cochlear duct, which ends at the cochlear apex § Contains the organ of Corti (hearing receptor) Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
The Cochlea The cochlea is divided into three chambers: § Scala vestibuli § Scala media § Scala tympani Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
The Cochlea § The scala tympani terminates at the round window § The scalas tympani and vestibuli are filled with perilymph § The scala media is filled with endolymph Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
The Cochlea § The “floor” of the cochlear duct is composed of: § The bony spiral lamina § The basilar membrane, which supports the organ of Corti § The cochlear branch of nerve VIII runs from the organ of Corti to the brain Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
The Cochlea Figure 15. 28 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Simplified Auditory Pathways Figure 15. 34 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
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