Anatomy Summary: The Vestibular Apparatus Figure 10-25d Nerve fibers Gelatinous otolith membrane Hair cells Otoliths are crystals that move in response to gravitational forces. (d) Macula
Transduction of Rotational Forces in the Cristae The semicircular canals sense rotational acceleration Figure Stationary board Bristles bend left Brush moves right Direction of rotation of the head Endolymph Bone Cupula Hair cells When the head turns right, endolymph pushes the cupula to the left.
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
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, Meniere's disease
Central Nervous System Pathways for Equilibrium Figure Vestibular apparatus Vestibular branch of vestibulocochlear nerve (VIII) Reticular formation Cerebral cortex Somatic motor neurons controlling eye movements Thalamus Cerebellum Vestibular nuclei of medulla
The Eye and Vision Light enters the eye Focused on retina by the lens Photoreceptors transduce light energy Electrical signal Processed through neural pathways
External Anatomy of the Eye Figure Lacrimal gland secretes tears. Upper eyelid Lower eyelid Pupil Iris Sclera Muscles attached to external surface of eye control eye movement. The orbit is a bony cavity that protects the eye. Nasolacrimal duct drains tears into nasal cavity.
Anatomy Summary: The Eye Figure Vitreous chamber Aqueous humor Cornea Fovea Macula Optic nerve Iris Pupil Retina Sclera is connective tissue. Ciliary muscle Central retinal artery and vein Canal of Schlemm (a) Sagittal section of the eye (b) Optic disk (blind spot) Lens Zonules
Anatomy Summary: The Eye Figure 10-30a Vitreous chamber Aqueous humor Cornea Fovea Optic nerve Iris Pupil Retina Sclera is connective tissue. Ciliary muscle Central retinal artery and vein Canal of Schlemm (a) Sagittal section of the eye Optic disk (blind spot) Lens Zonules
Anatomy Summary: The Eye Figure 10-30b Fovea Macula Central retinal artery and vein (b) Optic disk (blind spot)
Neural Pathways for Vision and the Pupillary Reflex Figure 10-31a Optic tract Eye Optic chiasm Optic nerve (a) Dorsal view
Neural Pathways for Vision and the Pupillary Reflex Figure 10-31b Optic tract Eye Lateral geniculate body (thalamus) Optic chiasm Optic nerve Visual cortex (occipital lobe) (b) Neural pathway for vision, lateral view
Neural Pathways for Vision and the Pupillary Reflex Figure 10-31c Optic tract Eye Lateral geniculate body (thalamus) Optic chiasm Optic nerve Visual cortex (occipital lobe) Midbrain Cranial nerve III controls pupillary constriction. Light (c) Collateral pathways leave the thalamus and go to the midbrain.
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 Figure 10-34a Cornea Iris Lens Ligaments Ciliary muscle (a) The lens is attached to the ciliary muscle by inelastic ligaments (zonules).
Accommodation Figure 10-34b Cornea Ligaments pulled tight Lens flattened Ciliary muscle relaxed (b) When ciliary muscle is relaxed, the ligaments pull on and flatten the lens.
Accommodation Figure 10-34c Ligaments slacken Lens rounded Ciliary muscle contracted (c) When ciliary muscle contracts, it releases tension on the ligaments and the lens becomes more rounded.
Common Visual Defects Figure 10-35a
Common Visual Defects Figure 10-35b
The Electromagnetic Spectrum Figure 10-36
Anatomy Summary: The Retina Figure 10-37d Rod (monochromatic vision) Cone (color vision) Bipolar cell Ganglion cell Amacrine cell Horizontal cell (d) Retinal photoreceptors are organized into layers. Neurons where signals from rods and cones are integrated Light
Phototransduction Figure 10-38
Photoreceptors: Rods and Cones Figure Melanin granules OUTER SEGMENT Visual pigments in membrane disks INNER SEGMENT SYNAPTIC TERMINAL Synapses with bipolar cells PIGMENT EPITHELIUM Bipolar cell Location of major organelles and metabolic operations such as photopigment synthesis and ATP production Disks Connecting stalks Mitochondria Cone Rods LIGHT Old disks at tip are phagocytized by pigment epithelial cells. Retinal Rhodopsin molecule Disks Opsin
Photoreceptors: Rods and Cones Figure (1 of 2) Melanin granules OUTER SEGMENT Visual pigments in membrane disks PIGMENT EPITHELIUM Disks Connecting stalks Old disks at tip are phagocytized by pigment epithelial cells. Disks
Photoreceptors: Rods and Cones Figure (2 of 2) INNER SEGMENT SYNAPTIC TERMINAL Synapses with bipolar cells Bipolarcell Location of major organelles and metabolic operations such as photopigment synthesis and ATP production Mitochondria Cone Rods LIGHT Retinal Rhodopsin molecule Opsin
Light Absorption of Visual Pigments Figure 10-40
Phototransduction in Rods Figure 10-41a cGMP levels high Transducin (G protein) Membrane potential in dark = –40mV Pigment epithelium cell Inactive rhodopsin (opsin and retinal) Na + Ca 2+ (a) In darkness, rhodopsin is inactive, cGMP is high, and CNG and K + channels are open. Disk CNG channel open K+K+ Tonic release of neurotransmitter onto bipolar neurons Rod
Phototransduction in Rods Figure 10-41b Ca 2+ Neurotransmitter release decreases in proportion to amount of light. Membrane hyperpolarizes to –70 mV Activated retinal Na + CNG channel closes Decreased cGMP Opsin (bleached pigment) Activates transducin Cascade (b) Light bleaches rhodopsin. Opsin decreases cGMP, closes CNG channels, and hyperpolarizes the cell. K+K+ Light
Phototransduction in Rods When light activates rhodopsin, a second- messenger cascade is initiated through transducin Figure 10-41c (c) In the recovery phase, retinal recombines with opsin. Retinal converted to inactive form Retinal recombines with opsin to form rhodopsin.
Ganglion Cell Receptive Fields Figure 10-42
Visual Fields and Binocular Vision Figure Optic chiasm Optic nerve Lateral geniculate body (thalamus) Visual cortex Left visual field Right visual field Binocular zone Visual field Optic tract
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