Transcript Chapter 10c
Chapter 10c Sensory Physiology The Ear: Equilibrium • • • • Vestibular apparatus Semicircular canals Otolith organs Equilibrium pathways The Vestibular Apparatus • Vestibular apparatus • A series of interconnected fluid-filled chambers • Provides information about movement and position in space Anatomy Summary: The Vestibular Apparatus SEMICIRCULAR CANALS (a) Superior Horizontal Posterior Cochlea Cristae within ampulla Utricle Saccule Maculae Figure 10-25a Anatomy Summary: The Vestibular Apparatus Vestibular apparatus (b) Posterior canal (head tilt) Left right Superior canal (nod for “yes”) Horizontal canal (shake head for “no”) Figure 10-25b Anatomy Summary: The Vestibular Apparatus Endolymph Cupula Hair cells Supporting cells Nerve (c) Figure 10-25c Anatomy Summary: The Vestibular Apparatus Hair cells Gelatinous otolith membrane Otoliths are crystals that move in response to gravitational forces. (d) Macula Nerve fibers Figure 10-25d Transduction of Rotational Forces in the Cristae • The semicircular canals sense rotational acceleration Brush moves right Cupula Endolymph Stationary board Bristles bend left Bone Hair cells Bone Direction of rotation of the head When the head turns right, endolymph pushes the cupula to the left. Figure 10-26 Otoliths Move in Response to Gravity or Acceleration Figure 10-27a Otoliths Move in Response to Gravity or Acceleration Figure 10-27b Dynamic Equilibrium and the crista ampullaris Meniere's disease Vincent van Gogh, whose artistic brilliance and supposed madness have made him a focus of popular fascination, suffered not from epilepsy or insanity but from Meniere's disease, Central Nervous System Pathways for Equilibrium Cerebral cortex Thalamus Vestibular branch of vestibulocochlear nerve (VIII) Vestibular apparatus Reticular formation Cerebellum Vestibular nuclei of medulla Somatic motor neurons controlling eye movements Figure 10-28 The Eye and Vision • Light enters the eye • Focused on retina by the lens • Photoreceptors transduce light energy • Electrical signal • Electrical signal • Processed through neural pathways External Anatomy of the Eye Lacrimal gland secretes tears. Muscles attached to external surface of eye control eye movement. Upper eyelid Sclera Pupil Iris Lower eyelid The orbit is a bony cavity that protects the eye. Nasolacrimal duct drains tears into nasal cavity. Figure 10-29 Anatomy Summary: The Eye Zonules Lens Optic disk (blind spot) Canal of Schlemm Aqueous humor Central retinal artery and vein Cornea Pupil Optic nerve Fovea Iris Macula Vitreous chamber Retina Ciliary muscle (b) Sclera is connective tissue. (a) Sagittal section of the eye Figure 10-30 Anatomy Summary: The Eye Zonules Lens Optic disk (blind spot) Canal of Schlemm Aqueous humor Central retinal artery and vein Cornea Optic nerve Fovea Pupil Iris Vitreous chamber Retina Ciliary muscle (a) Sagittal section of the eye Sclera is connective tissue. Figure 10-30a Anatomy Summary: The Eye Optic disk (blind spot) Central retinal artery and vein Fovea Macula (b) Figure 10-30b Neural Pathways for Vision and the Pupillary Reflex (a) Dorsal view Optic tract Eye Optic chiasm Optic nerve Figure 10-31a Neural Pathways for Vision and the Pupillary Reflex (b) Neural pathway for vision, lateral view Eye Optic Optic nerve chiasm Optic Lateral geniculate tract body (thalamus) Visual cortex (occipital lobe) Figure 10-31b Neural Pathways for Vision and the Pupillary Reflex (c) Collateral pathways leave the thalamus and go to the midbrain. Optic Optic nerve chiasm Optic Lateral geniculate tract body (thalamus) Visual cortex (occipital lobe) Eye Light Midbrain Cranial nerve III controls pupillary constriction. Figure 10-31c The Pupil • Light enters the eye through the pupil • Size of the pupil modulates light • Photoreceptors • Shape of lens focuses the light • Pupillary reflex • Standard part of neurological examination Refraction of Light Figure 10-32a Refraction of Light Figure 10-32b Optics Figure 10-33a Optics Figure 10-33b Optics Figure 10-33c Accommodation • Accommodation is the process by which the eye adjusts the shape of the lens to keep objects in focus Ciliary muscle Lens Ligaments Cornea Iris (a) The lens is attached to the ciliary muscle by inelastic ligaments (zonules). Figure 10-34a Accommodation Ciliary muscle relaxed Lens flattened Cornea Ligaments pulled tight (b) When ciliary muscle is relaxed, the ligaments pull on and flatten the lens. Figure 10-34b Accommodation Ciliary muscle contracted Lens rounded Ligaments slacken (c) When ciliary muscle contracts, it releases tension on the ligaments and the lens becomes more rounded. Figure 10-34c Common Visual Defects Figure 10-35a Common Visual Defects Figure 10-35b The Electromagnetic Spectrum Figure 10-36 Anatomy Summary: The Retina Horizontal cell Amacrine cell Light Neurons where signals from rods and cones are integrated Ganglion cell Bipolar cell Cone (color vision) Rod (monochromatic vision) (d) Retinal photoreceptors are organized into layers. Figure 10-37d Phototransduction Figure 10-38 Photoreceptors: Rods and Cones PIGMENT EPITHELIUM Old disks at tip are phagocytized by pigment epithelial cells. Melanin granules OUTER SEGMENT Disks Visual pigments in membrane disks Disks Connecting stalks INNER SEGMENT Mitochondria Location of major organelles and metabolic operations such as photopigment synthesis and ATP production Rhodopsin molecule Cone Rods Retinal Opsin SYNAPTIC TERMINAL Synapses with bipolar cells Bipolar cell LIGHT Figure 10-39 Photoreceptors: Rods and Cones PIGMENT EPITHELIUM Old disks at tip are phagocytized by pigment epithelial cells. Melanin granules OUTER SEGMENT Visual pigments in membrane disks Disks Disks Connecting stalks Figure 10-39 (1 of 2) Photoreceptors: Rods and Cones INNER SEGMENT Mitochondria Location of major organelles and metabolic operations such as photopigment synthesis and ATP production Rhodopsin molecule Cone Rods Retinal Opsin SYNAPTIC TERMINAL Synapses with bipolar cells Bipolar cell LIGHT Figure 10-39 (2 of 2) Light Absorption of Visual Pigments Figure 10-40 Phototransduction in Rods (a) In darkness, rhodopsin is inactive, cGMP is high, and CNG and K+ channels are open. Pigment epithelium cell Disk Transducin (G protein) Inactive rhodopsin (opsin and retinal) cGMP levels high CNG channel open Ca2+ Na+ K+ Membrane potential in dark = –40mV Rod Tonic release of neurotransmitter onto bipolar neurons Figure 10-41a Phototransduction in Rods (b) Light bleaches rhodopsin. Opsin decreases cGMP, closes CNG channels, and hyperpolarizes the cell. Activated Opsin (bleached Activates pigment) transducin retinal Cascade Decreased cGMP CNG channel closes Ca2+ Na+ K+ Membrane hyperpolarizes to –70 mV Light Neurotransmitter release decreases in proportion to amount of light. Figure 10-41b Phototransduction in Rods (c) In the recovery phase, retinal recombines with opsin. • When light activates rhodopsin, a secondmessenger cascade is initiated through transducin Retinal converted to inactive form Retinal recombines with opsin to form rhodopsin. Figure 10-41c Ganglion Cell Receptive Fields Figure 10-42 Visual Fields and Binocular Vision Visual field Binocular zone Left visual field Right visual field Optic chiasm Optic nerve Optic tract Lateral geniculate body (thalamus) Visual cortex Figure 10-43 Summary • General properties • Four types of sensory receptors • Adequate stimulus, threshold, receptive field, and perceptual threshold • Modality, localization, intensity, and duration • Somatic senses • Four modalities, second sensory neurons, and somatosensory cortex • Nociceptors, spinal reflexes, and pain Summary • Chemoreception • Olfaction and taste • The ear: hearing and equilibrium • The eye and vision • Retina, pupil, ciliary muscle, and photoreceptors