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Senses I. General Sense A. “General sense” refers to: temperature, pain, touch, pressure, vibration & proprioception. B. Receptors & receptor specificity - type of sense detected depends on anatomy of receptor 1. free nerve endings (unencapsulated) 2. modified dendritic endings for particular sense eg) encapsulated endings C. Receptive field Area monitored by a single receptor cell. The larger the receptive field, harder it is to pinpoint the stimulus eg) skin: light touch 2.5 in. field. VS tongue field 1mm D. Types of receptors: 1. nociceptors: stimulated by a variety of stimuli, cause the sensation of pain Referred pain: pain originating at visceral organs can be sensed as originating from superficial areas served by same spinal nerve. Mechanism unknown. 2. thermoreceptors: stimulated by change in temperature 3. mechanoreceptors: stimulated or inhibited by physical distortion a) Tactile receptors: touch & pressure b) Baroreceptors: stretch receptors monitor changes in stretch of walls of organs eg) blood vessels c) Proprioceptors: monitor position of joints, tendons & ligaments. 4. chemoreceptors: stimulated by chemicals (require specific receptors for chemicals) Figure 18.3a Tactile Receptors in the Skin Free Nerve Endings vs. Encapsulated ones Hair Merkel cells and Tactile tactile discs corpuscle Free nerve ending Ruffini corpuscle Lamellated corpuscle Root hair plexus Free nerve endings Sensory nerves Figure 18.1 Receptors and Receptive Fields Receptive field 1 Receptive field 2 Receptive fields Figure 18.2 Referred Pain Heart Liver and gallbladder Stomach Small intestine Appendix Colon Ureters Figure 18.3 Tactile Receptors in the Skin Merkel cells Tactile disc Merkel cells and tactile discs Merkel cells and Tactile tactile discs corpuscle Hair Free nerve endings Free nerve ending Free nerve endings of root hair plexus Tactile corpuscle Epidermis Ruffini corpuscle Lamellated corpuscle Root hair plexus Dermis Dendritic process Accessory cells (specialized fibrocytes) Dermis Concentric layers (lamellae) of collagen fibers separated by fluid Lamellated corpuscle Sensory nerves Tactile corpuscle LM 125 Concentric layers (lamellae) of collagen fibers separated by fluid Collagen Sensory fibers nerve fiber LM 550 Capsule Accessory cells Dendritic process Dendrites Sensory nerve fiber Ruffini corpuscle Lamellated corpuscle Tactile corpuscle; the capsule boundary in the micrograph is indicated by a dashed line. Figure 18.4 Baroreceptors and the Regulation of Autonomic Functions Baroreceptors of Carotid Sinus and Aortic Sinus Provide information on blood pressure to cardiovascular and respiratory control centers Baroreceptors of Lung Baroreceptors of Digestive Tract Provide information on volume of tract segments, trigger reflex movement of materials along tract Provide information on lung stretching to respiratory rhythmicity centers for control of respiratory rate Baroreceptors of Colon Baroreceptors of Bladder Wall Provide information on volume of urinary bladder, trigger urinary reflex Provide information on volume of fecal material in colon, trigger defecation reflex Figure 18.5 Chemoreceptors Chemoreceptive neurons Blood vessel Chemoreceptors in and near Respiratory Centers of Medulla Oblongata Trigger reflexive adjustments in depth and rate of respiration Sensitive to changes in pH and PCO2 in cerebrospinal fluid Chemoreceptors of Carotid Bodies Sensitive to changes in pH, PCO2, and PO2 in blood Chemoreceptors of Aortic Bodies Sensitive to changes in pH, PCO2, and PO2 in blood Carotid body LM 1500 Via cranial nerve IX Via cranial Trigger reflexive nerve X adjustments in respiratory and cardiovascular activity Which of the following types of receptors are especially common in the superficial portions of the skin, in joint capsules, within the periostea of bones, and around the walls of blood vessels? a. proprioceptors b. nociceptors c. tactile receptors d. chemoreceptors • II. Special Senses • These are all special senses: Hearing, Vision, Taste, Equilibrium, Olfaction. • A. Olfaction- chemoreceptors in olfactory epithelium • B. Gustation (taste)- chemoreceptors (covered in digestive system) • III. Eye • A. Lacrimal Apparatus • 1. lacrimal gland, lacrimal ducts, lacrimal punctum, lacrimal canaliculi (sup. & inf.) lacrimal sac, nasolacrimal duct nose • B. Conjunctiva • Clear mucous membrane on inner eyelid & white surface of the eye. • Cornea does not have conjunctiva. It helps lubricate the eye by producing mucus and some tears, although a smaller volume of tears than the lacrimal gland. Helps to prevent the entrance of microbes into the eye • Inflammation: Conjunctivitis Figure 18.6a The Olfactory Organs Olfactory bulb Olfactory nerve fibers (N I) Olfactory tract Cribriform plate of ethmoid Olfactory epithelium The distribution of the olfactory receptors on the left side of the nasal septum is shown by the shading. Figure 18.6b The Olfactory Organs To olfactory bulb Olfactory nerve fibers Regenerative basal cell: divides to replace worn-out olfactory receptor cells Cribriform plate Olfactory receptor cell Olfactory epithelium Mucous layer Olfactory cilia: surfaces contain receptor proteins A detailed view of the olfactory epithelium • C. Layers of the eye • 1. Fibrous tunic • a) Sclera: white of the eye. Collagen & elastic fibers. Thicker at the back of eye. • b) Cornea: made of transparent collagen in regular sheets (like pages in a book.) • The cornea is avascular, getting oxygen via diffusion from air & nutrients from aqueous humor in anterior chamber. It does have lots of pain receptors & has high capacity for regeneration. • 2. Vascular tunic • a) Iris – • 1) 2 layers of smooth muscle • i. Circularly arranged pupillary sphincter muscle • ii. radiating pupillary dilating muscles • 2) pigmented epithium: various am’t of melanin & different depths account for eye color • • Conjunctiva • b) Choroid – middle layer, pigmented & vascularized. Contains lymphatics. • Blood supply nourishes other layers of the eye. (in animals: tapedum lucidum reflects light- in cow/pig eye dissection) Melanin absorbs light, so it doesn’t reflect within the eye, causing confusion. • c) Ciliary body= ciliary muscle (smooth muscle) + suspensory ligaments that anchor to lens. Ring of tissue that encircles the lens. Controls shape of lens for focusing Figure 18.21a Sectional Anatomy of the Eye Fibrous Vascular Neural tunic tunic tunic (sclera) (choroid) (retina) The three layers, or tunics, of the eye Fibrous tunic- Sclera & Cornea • 3. Neural tunic • a) Retina: innermost layer of the eye. Retina itself has 2 layers• i) outer pigmented layer with melanocytes • ii) thick neural layer 3 types of neurons: • 1. Photoreceptors: • rods See light/dark, shades of gray. Rods are very sensitive to light & suited to night vision. Peripheral vision & perception of motion. • Cones: color vision. 3 types: blue, red & green. (needs bright light) • 2. Bipolar cells • 3. Ganglion cells optic nerve • b) macula lutea (yellow spot), at the center of the macula, there is a pit, called the fovea centralis which only contains cones! The fovea is where light is focused when you look directly at something. Rods not found in fovea. • c) optic disc: optic nerve, artery & vein passes through the retina. Blind spot. • D. Cavities & Chambers of the Eye • 1. Anterior Cavity- Filled with aqueous humor (clear, watery). • a. anterior chamber in front of iris • b. posterior chamber between iris and lens • ciliary body creates aqueous humor that moves to anterior chamber via pupil& drains into Canals of Schlemm: improper drainage: glaucoma • Aqueous humor: 1. Equilibrium of formation & drainage keeps intraocular pressure constant. 2. Aqueous humor nourishes cornea & lens (both avascular) • 2. Posterior Cavity • Lens: separates eye into anterior & posterior compartments. • Filled with vitreous humor (clear, gelatinous material). Keeps retina in place. • 3. Lens : Thick, transparent & biconvex. Concentric layers of cells that become fibers. Fibers are proteins folded in such a way that they are transparent. Fibers added throughout life lens thickens with age, is denser more convex & less elastic- ability to focus diminishes in old age. Figure 18.21b Sectional Anatomy of the Eye Ora serrata Fornix Palpebral conjunctiva Posterior cavity (Vitreous chamber filled with the vitreous body) Ocular conjunctiva Ciliary body Anterior chamber (filled with aqueous humor) Lens Pupil Cornea Iris Posterior chamber (filled with aqueous humor) Central retinal artery and vein Optic nerve Optic disc Fovea Corneal limbus Retina Suspensory ligaments Choroid Sclera Major anatomical landmarks and features in a diagrammatic view of the left eye Figure 18.21c Sectional Anatomy of the Eye Pupillary dilator muscles (radial) Constrictors contract Pupil Pupillary constrictor muscles (sphincter) Dilators contract The action of pupillary muscles and changes in pupillary diameter Figure 18.23a Retinal Organization Rods & Cones Horizontal cell Cone Rod Choroid Pigmented part of retina Rods and cones Bipolar cells Amacrine cell Ganglion cells Nuclei of rods Nuclei of Nuclei of ganglion cells and cones bipolar cells The retina LM 70 LIGHT Histological organization of the retina. Note that the photoreceptors are located closest to the choroid rather than near the vitreous chamber. What nerve fibers make up the optic nerve? a) photoreceptors c) bipolar cells b) ganglion cells d) horizontal cells Figure 18.23c Retinal Organization -find your blind spot. Macula Fovea lutea Optic disc Central retinal artery (blind spot) and vein emerging from center of optic disc A photograph taken through the pupil of the eye showing the retinal blood vessels, the origin of the optic nerve, and the optic disc Which of the following is (are) a function(s) of the vascular tunic of the eye? a. regulating the amount of light entering the eye b. secreting and reabsorbing the aqueous humor that circulates within the eye c. controlling the shape of the lens d. all of the above Figure 18.22a The Lens and Chambers of the Eye Choroid Posterior cavity Ciliary body Vascular tunic Iris (uvea) Anterior cavity Cornea Neural tunic (retina) Neural part Sclera Fibrous tunic Pigmented part The lens is suspended between the posterior cavity and the posterior chamber of the anterior cavity. Figure 18.24 The Circulation of Aqueous Humor (Part 1 of 1) Ciliary process Posterior chamber Suspensory ligaments Anterior chamber Pigmented epithelium Posterior cavity (vitreous chamber) Lens Pupil Cornea Canal of Schlemm Body of iris Retina Conjunctiva Choroid Sclera Ciliary body Anterior cavity Glaucoma Glaucoma: drainage ducts are blocked, aqueous humor builds up-> pressure builds-> compress arteries that serve nerves. If nerves die, blindness (partial or total, depending on damage) occurs. Vision associated with glaucoma. • • • • • E. Vision Pathway Optic nerve optic chiasm optic tract optic radiations occipital lobe a) Some fibers synapse with thalamus. The cells at the thalamus form optic radiations to reach occipital cortex. b) Other fibers from the optic tract synapse at the superior colliculus of midbrain c) other fibers synapse with hypothalamus Figure 18.26 Anatomy of the Visual Pathways, Part II Optic chiasm Optic tract hypothalamic nuclei, pineal gland, and reticular formation Hypothalamus thalamus thalamus Superior colliculus optic radiation LEFT CEREBRAL HEMISPHERE RIGHT CEREBRAL HEMISPHERE Visual cortex of cerebral hemispheres Note the thalamus & superior colliculus are part of the pathway for optic fibers Vision & the brain TED conference Figure 18.25 Anatomy of the Visual Pathways, Part I Cribriform plate of ethmoid Crista galli Right eyeball Levator palpebrae superioris muscle Left eyeball Superior rectus muscle Medial rectus muscle Superior oblique muscle Branch of N V Lacrimal gland Right optic nerve (N II) Superior rectus muscle Levator palpebrae superioris muscle Trochlear nerve (N IV) Cut ends of optic nerve (segment removed) Left optic nerve (N II) Cerebral arterial circle Optic chiasm Horizontal section, superior view IV. Ear Ear functions: hearing & equilibrium (balance). A. Outer ear: 1. Auricle or pinna: “ear”. Shaped to funnel & amplify sound waves as it enters the external auditory meatus. 2. External auditory meatus: 2.5 cm long opening, lined with fine hairs & modified sweat & sebaceous glands produce cerumen protects ear from foreign materials & microbes. Figure 18.9 Anatomy of the Ear (Part 1 of 1) EXTERNAL EAR MIDDLE EAR INNER EAR Auditory ossicles Semicircular Petrous part Facial nerve of temporal (N VII) canals bone Auricle External acoustic meatus Bony labyrinth of inner ear Tympanic membrane Tympanic cavity Elastic cartilage Oval window Round window Vestibule Auditory tube Cochlea To nasopharynx B. Middle Ear - The boundary of external to middle ear is the tympanic membrane. - Air filled space in the petrous portion of the temporal bone. 1. Ossicles: malleus, incus & stapes Sound waves external ear vibrate tympanic membrane malleus, which passes vibrations to incus & then to stapes. Vibrations are amplified 20 times by the time it reaches stapes. Vibrations passed on to oval window of cochlea. 2. Eustacian tube- links middle ear to superior pharynx, behind the nasal cavity. About 4cm long. Normally closed (flattened) but can open when yawning, swallowing to equalize pressure with outside. *important b/c eardrum doesn’t vibrate freely if pressure is not equal - route for middle ear infections (otitis media) Figure 18.10b The Middle Ear Temporal bone (petrous part) Stabilizing ligament Malleus Incus Base of stapes at oval window Chorda tympani nerve (cut), a branch of N VII External acoustic meatus Stapes Round window Tympanic cavity (middle ear) Tympanic membrane (tympanum) Auditory tube Structures within the middle ear cavity C. Inner ear - also lies in the petrous portion of temporal bone. 1.Cochlea a) perilymph is found in the vestibular duct & tympanic duct (above & below cochlear duct). The tympanic duct ends at the round window. b) endolymph inside cochlear duct which also houses the spiral organ of Corti c) spiral organ of Corti. i) Hair cells w/ stereocilia. Hair cells embedded in a basilar membrane. ii) tectorial membrane: stereocilia embedded. iii) At the base, hair cells synapse with sensory fibers of cochlear nerve. As vibrations are transmitted to perilymph in the vestibular duct, then to tympanic duct “bounces” the basilar membrane of the spiral organbends the stereocilia of hair cells. The bending causes the neuron to fire impulses to the cochlear nerve, temporal lobe of brain & inferior colliculus. iv) pitch: different regions of organ of corti are sensitive & deform at different frequencies. Shorter the wavelength = higher frequency v) amplitude: size of deformation of basilar membrane Figure 18.10d The Middle Ear Malleus Tendon of tensor tympani muscle Malleus attached to tympanic membrane Inner surface of tympanic membrane Incus Base of stapes at oval window Stapes Stapedius muscle The tympanic membrane and auditory ossicles as seen through a fiber-optic tube inserted along the auditory canal and into the middle ear cavity 2. Semicircular canals - rotational equilibrium. - 3 canals at right angles to each other 3. Vestibule - static equilibrium Hair cells with stereocilia also vestibule & semicircular canals & function the same (bending impulse) but are embedded in different structures. D. Auditory Pathway 1. Sound: cochlear branch vestibulocochlear nerve inferior colliculus thalamus temporal lobe for processing 2. Equilibrium: vestibular branch vestibulocochlear nerve olivary nucleus of medulla(proprioception) other parts of brain dealing with equilibrium & proprioception. Figure 18.12a Semicircular Canals and Ducts KEY Semicircular canal Membranous labyrinth Bony labyrinth Anterior Semicircular ducts Lateral Posterior Vestibule Cristae within ampullae Maculae Endolymphatic sac Cochlea Utricle Saccule Vestibular duct Cochlear duct Anterior view of the bony labyrinth cut away to show the semicircular canals and the enclosed semicircular ducts of the membranous labyrinth Tympanic Organ of duct Corti Figure 18.17a The Cochlea and Organ of Corti Round window Stapes at oval window Cochlear duct Vestibular duct Tympanic duct Cochlear Vestibular branch branch Vestibulocochlear nerve (VIII) Semicircular canals Structure of the cochlea in partial section KEY From oval window to tip of spiral From tip of spiral to round window Figure 18.17b The Cochlea and Organ of Corti Vestibular membrane Tectorial membrane Basilar membrane Vestibular duct contains perilymph Organ of Corti Cochlear duct (contains endolymph) Tympanic duct contains perilymph Cochlear nerve Vestibulocochlear nerve (VIII) Structure of the cochlea within the temporal bone showing the turns of the vestibular duct, cochlear duct, and tympanic duct Cochlea Figure 18.17e The Cochlea and Organ of Corti Cochlear duct (scala media) Tectorial membrane Vestibular membrane Tectorial membrane Outer hair cell Basilar membrane Inner hair cell Nerve fibers Diagrammatic and histological sections through the receptor hair cell complex of the organ of Corti Tympanic duct Basilar Hair cells Spiral ganglion (scala tympani) membrane of organ cells of of Corti cochlear nerve Organ of Corti LM 125 Hair cells are what kind of receptor? a)Chemoreceptor d) baroreceptor b) nociceptor c) mechanoreceptor Spiral organ & sound • high pitch vs low pitch Each part of spiral organ is sensitive to different frequencies of waves. • Amplitude (loudness) is the degree of the vibrations of basilar membrane. Loud noise cause fluid in canal of cochlea to exert more pressure on basilar membrane. See animated tutorial hearing Auditory pathway From spiral organ, travel to synapse w/ vestibulocochlear nerve (VIII) that brings impulse to synapse with medulla Inferior colliculus Thalamus Temporal lobe Figure 18.13a The Function of the Semicircular Ducts, Part I Vestibular branch (N VIII) Semicircular ducts Anterior Posterior Lateral Cochlea Ampulla Endolymphatic sac Endolymphatic duct Utricle Anterior view of the maculae and semicircular ducts of the right side Saccule Maculae Vestibule & Semicircular canals