Chapter 10c
Sensory Physiology
The Ear: Equilibrium
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•
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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