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- 1. The Special Senses Photoreceptors Mechanoreceptors Chemoreceptors
- 3. Figure 15.1a
- 4. Figure 15.1b
- 5. Figure 15.2
- 6. Figure 15.3
- 7. Internal Structure of the Eye (sagittal section)
- 8. Figure 15.4a
- 11. Pupillary Constriction and Pupillary Dilation
- 13. Neural Layer - Retina
- 14. Photoreceptors – Rods and Cones
- 15. The Electromagnetic spectrum and photoreceptor sensitivities
- 16. Ganglion cells and the Optic Nerve
- 18. The Eye
- 19. Figure 15.7
- 20. Aqueous and Vitreous Humors
- 22. The Lens
- 24. Figure 15.13
- 27. Refraction – spoon appears to be broken at the water-air interface
- 28. Thickening and hardening of the crystallins in the lens leads to the formation of cataracts = clouding of the lens ct
- 29. Path taken by light through the eye : cornea—aqueous humor--pupil—lens—vitreous humor—ganglion cells—bipolar neurons--photoreceptors
- 30. Pathway of light through the Retina: Ganglion cells—bipolar neurons--Photoreceptors
- 31. Transmission of electrical signals – light hits the photoreceptors and they generate electrical signals Bipolar neurons- Ganglion cells
- 32. Visual pathway to the Brain
- 34. Mechanoreceptors – Hair Cells Sense organs - Ears
- 35. The EAR
- 37. The EAR
- 38. Middle and Inner Ear
- 39. The 3 ossicles in the Middle Ear
- 40. Bony and Membranous Labyrinth
- 41. Anatomy of the Cochlea
- 43. Organ of Corti
- 44. Photograph of cochlear Hair Cells with stereocilia Figure 15.33
- 45. Route of Sound Waves through the Ear
- 47. Figure 15.34 Auditory Pathway to the primary auditory cortex in the TEMPORAL LOBES in the cerebral hemispheres in the Brain
- 52. Taste buds and Gustatory cells
- 54. Figure 15.24 The Gustatory Pathway to the Primary Gustatory Cortex in the Insula
Notas del editor
- 3 parts of eyeball = Eye wall Humors Lens Humors = 2 types aqueous and vitreous aqueous humor --> filtered from blood capillaries in the ciliary processes. Aqueous humor is drained by the canal of schlemm Function: provides nutrients and oxygen to the avascular cornea and avascular lensremoves metabolic wastes from the cornea and the lens also maintains the intraocular pressure (to prevent formation of glaucoma *aqueous humor is located in the anterior segment between the cornea and the lensvitreous humor is the thick fluid located in the posterior segment of the eye --> behind the lens and in front of the eye wall Vitreous humor is formed during embyonic development and it lasts a lifetime Function: 1) vitreous humor supports the back of the lens 2) pushes the neural layer firmly against the pigmented layer to prevent retinal detachment *cells in pigmented layer provide nutrients to the photoreceptors in the neural layer
- 3 rd part of the eye the lens it is a biconvex, flexible, avascular, transparent structure held in an upright position by the suspensory ligaments composed of precisely folded clear proteins called CRYSTALINS When the cystallin proteins form climps due to lack of nutriends and oxygen cataracts develop Function: lens refracts (or bends) light to focus on the photoreceptors in the retina (neural layer) =========================== Far distances objects viewed will not require ACCOMODATION of the lens accomodation of the lens refers to changes that lens undergoes to focus images on the retina --------------------------- Near objects less than 20 ft require accomodation of the lens ciliary muscles in the ciliary body contract causes the lens to bulge anteriorly and refract the image onto the retina Next slide for more info
- Different types of lenses diverge/converge light before you see it to fix vision Problems with refraction of light by the lens Myopic Eye (nearsighted) eyeball too long, images focused in front of the retina (contains the photoreceptors) for correction CONCAVE lens diverges the image to focus on the retina Hyperopic eye (farsighted) *the eye can focus clearly on distant objects eyeball too short, so in close vision, images focused behind the retina for correction CONVEX lens converges the image onto the retina
- Image processing and the route taken by light through the eye THIS IS IMPORTANT Cornea Aqueous Humor Pupil Lens Vitreous Humor ganglion cells (light passes) bipolar cells (neurons) (light passes) photoreceptors (respond to light energy by producing electrical signals Electrical signals travel to bipolar cells (neurons) ganglion cells are the only cells in the eye that generate/transmit action potentials via their axons axons bundle to form the OPTIC NERVE (Cranial Nerve II)
- Optic nerves (one from each eye) cross over before entering the brain The point where the optic nerves cross over OPTIC CHIASMA After the optic chiasma OPTIC TRACTS as they are in the brain Because the crossing over, images from the left eye are received from the primary visual cortex located in the right occipital lobe and vice versa Information from the optic tracts (action potentials) are sent to the superior colliculi in the midbrain visual reflex centers Visual information is relayed in the LGN (Lateral Geniculate Nucleus) in the thalamus visual relay center From the LGN, the information is sent to the primary visual cortex for interpretation The visual association center adds detail to the image Slide 34
- EAR 3 regions
- EAR in search of the mechanoreceptor HAIR CELLS 3 regions - External, Middle, and Inner External ear consists of 2 parts auricle (pinna) and the external auditory canal (external acoustic meatus) Auricle composed of elastic cartilage covered with skin function of the auricles (pinnae) direct sound waves into the external auditory canal
- EAR 3 regions External, Middle, Internal External Auricle = pinna and External auditory canal Auricle composed of elastic cartilage External auditory canal short canal carved in the temporal bone External auditory canal is lined with skin sebaceous glands and specialized sweat glands called ceruminous glands secrete Cerumen = earwax Cerumen keeps the tympanic membrane soft and supple (malleable) Cerumen also prevents the entry of foreign substances such as water or insects The tympanic membrane cone-shaped flexible membrane that separates the external auditory canal from the middle ear ==========================
- Middle Ear = Tympanic cavity air filled and contains/houses the smallest bones in the body called the auditory ossicles three auditory ossicles malleus - abuts tympanic membrane incus – located between the malleus and the stapes stapes – sits atop an oval window The middle ear is separated from the inner (=internal) ear by a bony wall with two openings The two openings round window and the oval window The stapes sits on top of the oval window (the superior opening) Extending from the middle ear is the pharyngotympanic tube, which equalizes the air pressure in the middle ear with the air pressure in the external auditory canal (=atmospheric pressure) The air pressure in front of the tympanic membrane must be equal to the air pressure behind it to get optimum vibration of the tympanic membrane which sets off a series of events which eventually will be interpreted as hearing ======================== Inner/Internal Ear Labyrinth Composed of 2 parts bony and the membranous labyrinth Bony Labyrinth (3 parts) carved inside the temporal bone and consists of meandering channels vestibule semicircular canals cochlea All 3 parts of the bony labyrinth contain a fluid called PERILYMPH = CSF Membranous Labyrinth – consists of a continuous series of ducts and sacs. These ducts and sacs contain the fluid called ENDOLYMPH (similar to intracellular fluid… high in K+) Hence, the membranous labyrinth structures (ducts and sacs) are surrounded by perilymph in the bony labyrinth. These same structures of the membranous labyrinth (ducts and sacs) contain endolymph ------------------------- Vestibule = bony labyrinth structure houses 2 membranous sacs called SACCULE and UTRICLE contain equiilibrim receptors called MACULAE used for static equilibrium for positioning of the head in space the maculae is involved in posture Semicircular canals bony labyrinth arranged in 3 planes of space = 3 semicircular canals: anterior semicircular canal posterior “ “ lateral “ “ Meandering through the semicircular canals are the membranous ducts called semicircular ducts end in expanded structures called AMPULLAE (singular = ampulla) house equilibrium structures called the CRISTAE AMPULLARES (crysta ampullares singular) Cristae ampullares are used for rotational movements of the head; act to maintain the position of the head in space after rotational movements (think of a ballerina) ------------------- Cochlea bony labrinth makes a 2 and a half turn around a bony pillar called the MODIOLUS Inside the cochlea is the membranous duct called the COCHLEAR DUCT houses the spiral organ of Corti rests on a flexible membrane called the BASILAR MEMBRANE The spiral organ of Corti is composed of supporting cells and the HAIR CELLS = MECHANORECEPTORS
- Hair cells have stereocilia microvilli stiffened by actin The stereocilia are trapped in a gel-like membrane called the TECTORIAL MEMBRANE Wrapped around the bases of the hair cells are the afferent fibers of the cochlear nerve The cochlear nerve is a division of the vestibulocochlear nerve = CN VIII
- Route taken by sound through the ear Auricles (pinnae) direct sound waves into the external auditory canal Travels through the canal to the tympanic membrane The tympanic membrane vibrates and the sound wave is transmitted as vibrations to the ossicles in the middle ear in the order Malleus Incus Stapes The stapes vibrates and sets the fluids in the inner ear into motion perilymph moves and the endolymph also moves This causes the BASILAR MEMBRANE in the spiral organ of corti to oscillate The hair cells located on top of the basilar membrane also oscillate which causes the stereocilia trapped in the tectorial membrane to bend The bending of the stereocilia causes the generation of electrical signals conducted to the cochlear afferent fibers at the bases of the hair cells These afferent fibers undergo depolarization and the generation of action potentials These action potentials are transmitted via the vestibulocochlear nerve (CN VIII) to the structures in the brain Once inside the brain, we are looking at tracts. The action potentials are transmitted to the INFERIOR COLLICULI in the midbrain (inferior colliculi - auditory reflex centers) Action potentials are then transmitted to the MEDIAL GENICULATE NUCLEUS (MGN) = auditory relay center in the thalamus From the relay centers in the thalamus, the action potentials reach the primary auditory cortex located in the temporal lobes INTERPRETATION OF SOUND AND THE QUALITY OF THE SOUND using the auditory association center Equilibrium receptors = mechanoreceptors Mechanoreceptors Maculae and cristae ampullares both are composed of hair cells and supporting cells The hair cells in Maculae have stereocilia trapped in a gel-like membrane called OTOLITHIC membrane When the hair moves sideways (horizontally) the maculae in the utricle respond to maintain posture When the hair moves vertically (= ascending in an elevator), the maculae in the saccule respond to maintain posture Cristae ampullares hair cells + supporting cells Hair cells have stereocilia trapped in cupula (a gel-like membrane) During rotational movements of the head (twirling) the hair cells in the cristae ampullares respond to maintain posture (prevents falling) --------------- Deafness loss of hearing Conduction deafness interference in the conduction of sound waves to the tympanic membrane EXAMPLES impacted ear wav, perforated tympanic membrane SOUND WAVES DO NOT CAUSE VIBRATION OF THE TYMPANIC MEMBRANE Sensoneural deafness damage to the hair cells or to the cochlear nerve or to the vestibulocochlear nerve or to the auditory cortex in the temporal lobe
- Chemoreceptors Olfactory and Gustatory cells -------------------------
- The olfactory cells mediate OLFACtION sense of smell In the roof of the nasal cavity yellowish patch called the OLFACTORY EPITHELIUM composed of three types of cells Olfactory cells bipolar neurons with ciliated dendrites. The cilia on the dendrites of the bipolar neurons are called OLFACTORY HAIRS OLFACTORY HAIRS are trapped (embedded) in a thin layer of mucus the olfactory cells (bipolar neurons) are unique because unlike other neurons, the olfactory cells do NOT exhibit longevity; they are replaced every 30-60 days and replaced by the next type of cell… THE BASAL CELLS Basal Cells part of the olfactory epithelium and they differentiate to form new olfactory cells to replace the old ones every 30-60 days, as mentioned above. Supporting Cells produce a yellowish pigment which gives the olfactory epithelium its yellowish tint (hue) Supporting cells produce mucus
- Physiology of olfaction The chemical or odorant MUST dissolve in the thin coat of mucus covering the olfactory hairs Dissolved chemical binds to the olfactory hairs to cause depolarization and the formation of electrical signals The axons of the olfactory cells bundle up to form the OLFACTORY NERVE (CN I) If the depolarization currents electrical signals are strong enough axons in the olfactory nerve will generate/transmit action potentials to another set of neurons called MITRAL CELLS located in the OLFACTORY BULB The axons of the mitril cells bundle up to form the OLFACTORY TRACT (this is unique) When the action potentials reach the olfactory tract transmitted to the two brain areas (MAMMILLARY BODIES and Mammillary bodies located inferior to the hypothalamus action potentials are transmitted to the amygdala for the recognition of the emotional aspect of smell
- 12/6 Chemoreceptors Gustatory cells used in Gustation = sense of taste Gustatory cells specialized epithelial cells located in TASTE BUDS located in papillae Papillae are the peg-like projections on the surface of the tongue 3 types of papillae contain taste buds Fungiform papillae Foliate papillae Circumvallate (Vallate) papillae Anatomy of a taste bud Each taste bud consists of 2 types of epithelial cells Gustatory cells and Basal cells Gustatory cells are the chemoreceptors and they have long microvilli that extend through taste pores to the surface of the tongue long microvilli called GUSTATORY HAIRS are bathed in SALIVA Hence, any chemical can be tasted only when the chemical dissolves in saliva and the dissolved chemical attaches to the gustatory hairs depolarization and development of electrical signals
- 3 cranial nerves trasnmit action potentials from the gustatory cells in the taste buds when chemicals dissolved in saliva attach and depolarize the gustatory hairs Wrapped around the bases of the gustatory cells are the afferent fibers: Anterior 2/3 of the tongue the fibers will be from the FACIAL NERVE (CN VII) Posterior 1/3 of the tongue is supplied by the GLOSSOPHARYNGEAL NERVE (CN IX) In the pharynx (throat) the gustatory cells are wrapped by the afferent fibers from the VAGUS NERVE (CN X) (refer to previous slide) Depolarization of the gustatory hairs depolarization generation of electrical signals development/transmission of action potentials (=nerve impulse) via the facial nerve, glossopharyngeal nerve, vagus nerve nerve impulse is relayed to the gustatory relay center in the ventral posterior medial nucleus (VPM nucleus) nerve impulse is relayed from the VPM nucleus to the primary gustatory cortex in the INSULA The gustatory association areas provide quality and discrimination to taste