Chapter 10c Sensory Physiology. The Ear: Equilibrium Vestibular apparatus Semicircular canals Otolith organs Equilibrium pathways.
Post on 29-Mar-2015
216 Views
Preview:
Transcript
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
Cochlea
(a)
Saccule
UtricleCristae within
ampulla
Maculae
SEMICIRCULAR CANALS
Superior
Horizontal
Posterior
Anatomy Summary: The Vestibular Apparatus
Figure 10-25a
Anatomy Summary: The Vestibular Apparatus
Figure 10-25b
Vestibularapparatus
Superior canal(nod for “yes”)
Horizontal canal(shake head
for “no”)
Posterior canal(head tilt)
Left right
(b)
Anatomy Summary: The Vestibular Apparatus
Figure 10-25c
(c)
Cupula
Haircells
Supportingcells
Nerve
Endolymph
Anatomy Summary: The Vestibular Apparatus
Figure 10-25d
Nerve fibers
Gelatinousotolith
membrane
Hair cells
Otoliths are crystalsthat move in responseto gravitational forces.
(d) Macula
Transduction of Rotational Forces in the Cristae
• The semicircular canals sense rotational acceleration
Figure 10-26
Stationaryboard
Bristlesbend left
Brush movesright
Direction of rotation of the head
Endolymph
Bone
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 10-28
Vestibular apparatus
Vestibular branch ofvestibulocochlearnerve (VIII)
Reticularformation
Cerebralcortex
Somaticmotor neuronscontrolling eye
movements
Thalamus
Cerebellum
Vestibularnuclei ofmedulla
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
Figure 10-29
Lacrimal glandsecretes tears.
Uppereyelid
Lowereyelid
Pupil
Iris
Sclera
Muscles attached toexternal surface of eyecontrol eye movement.
The orbit is a bonycavity that protectsthe eye.
Nasolacrimal ductdrains tears intonasal cavity.
Anatomy Summary: The Eye
Figure 10-30
Vitreous chamber
Aqueoushumor
Cornea
Fovea
Macula
Optic nerve
Iris
Pupil
Retina
Sclera is connective tissue.Ciliary muscle
Central retinalartery and vein
Canal ofSchlemm
(a) Sagittal section of the eye
(b)
Optic disk(blind spot)
LensZonules
Anatomy Summary: The Eye
Figure 10-30a
Vitreous chamber
Aqueoushumor
Cornea
FoveaOptic nerve
Iris
Pupil
Retina
Sclera is connective tissue.Ciliary muscle
Central retinalartery and vein
Canal ofSchlemm
(a) Sagittal section of the eye
Optic disk(blind spot)
LensZonules
Anatomy Summary: The Eye
Figure 10-30b
Fovea
Macula
Central retinalartery 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
Optictract
Eye
Lateral geniculatebody (thalamus)
Opticchiasm
Opticnerve
Visual cortex(occipital lobe)
(b) Neural pathway forvision, lateral view
Neural Pathways for Vision and the Pupillary Reflex
Figure 10-31c
Optictract
Eye
Lateral geniculatebody (thalamus)
Opticchiasm
Opticnerve
Visual cortex(occipital lobe)
Midbrain
Cranial nerve III controlspupillary constriction.
Light
(c) Collateral pathwaysleave the thalamusand go to themidbrain.
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 ciliarymuscle by inelastic ligaments (zonules).
Accommodation
Figure 10-34b
Cornea
Ligamentspulled tight
Lens flattened
Ciliary musclerelaxed
(b) When ciliary muscle is relaxed, theligaments pull on and flatten the lens.
Accommodation
Figure 10-34c
Ligamentsslacken
Lens rounded
Ciliary musclecontracted
(c) When ciliary muscle contracts, itreleases tension on the ligamentsand 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
Ganglioncell
Amacrinecell
Horizontalcell
(d) Retinal photoreceptors are organized into layers.
Neurons where signalsfrom rods and cones
are integrated
Light
Phototransduction
Figure 10-38
Photoreceptors: Rods and Cones
Figure 10-39
Melanin granules
OUTER SEGMENT
Visual pigments inmembrane disks
INNER SEGMENT
SYNAPTIC TERMINALSynapses withbipolar cells
PIGMENTEPITHELIUM
Bipolar cell
Location of majororganelles and metabolicoperations such asphotopigment synthesisand ATP production
Disks
Connectingstalks
Mitochondria
Cone Rods
LIGHT
Old disks at tip arephagocytized bypigment epithelial cells.
Retinal
Rhodopsinmolecule
Disks
Opsin
Photoreceptors: Rods and Cones
Figure 10-39 (1 of 2)
Melanin granules
OUTER SEGMENT
Visual pigments inmembrane disks
PIGMENTEPITHELIUM
Disks
Connectingstalks
Old disks at tip arephagocytized bypigment epithelial cells.
Disks
Photoreceptors: Rods and Cones
Figure 10-39 (2 of 2)
INNER SEGMENT
SYNAPTIC TERMINALSynapses withbipolar cells
Bipolar cell
Location of majororganelles and metabolicoperations such asphotopigment synthesisand ATP production
Mitochondria
Cone Rods
LIGHT
Retinal
Rhodopsinmolecule
Opsin
Light Absorption of Visual Pigments
Figure 10-40
Phototransduction in Rods
Figure 10-41a
cGMPlevels high
Transducin(G protein)
Membrane potentialin dark = –40mV
Pigment epithelium cell
Inactiverhodopsin
(opsin and retinal)
Na+
Ca2+
(a) In darkness, rhodopsin isinactive, cGMP is high, andCNG and K+ channels are open.
Disk
CNG channelopen
K+
Tonic release ofneurotransmitter
onto bipolar neurons
Rod
Phototransduction in Rods
Figure 10-41b
Ca2+
Neurotransmitter releasedecreases in proportion
to amount of light.
Membranehyperpolarizes
to –70 mV
Activatedretinal
Na+
CNG channelcloses
DecreasedcGMP
Opsin (bleachedpigment)
Activatestransducin
Cascade
(b) Light bleaches rhodopsin. Opsindecreases cGMP, closes CNGchannels, and hyperpolarizes the cell.
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, retinalrecombines with opsin.
Retinal converted toinactive form
Retinal recombineswith opsin to
form rhodopsin.
Ganglion Cell Receptive Fields
Figure 10-42
Visual Fields and Binocular Vision
Figure 10-43
Opticchiasm
Optic nerve
Lateralgeniculate body
(thalamus)
Visual cortex
Leftvisualfield
Rightvisualfield
Binocularzone
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
top related