Sensory Receptors

(a) Receptor is afferent neuron. (b) Receptor regulates afferent neuron.

To CNS

Afferentneuron

Afferentneuron

To CNS

Receptorprotein

Sensoryreceptor

Stimulus

Neurotransmitter

Sensoryreceptorcell Stimulus

Stimulusleads toneuro-transmitterrelease.

Figure 50.3

Figure 50.4a

(a) Single sensory receptor activated

Gentle pressure

Sensory receptor

More pressure

Low frequency ofaction potentials per receptor

High frequency ofaction potentials per receptor

Figure 50.4b

(b) Multiple receptors activated

Sensory receptor Gentle pressure

More pressure

Fewerreceptorsactivated

Morereceptorsactivated

Gentle pressure, vibration,and temperature

Connectivetissue

Hair Pain

Epidermis

Dermis

Hypodermis

Nerve

Hair movement

Strongpressure

Figure 50.5

Figure 50.24

Papillae

Papilla

Tastebuds

(a) Tongue

Key

SweetSalty

SourBitter

Umami

Taste bud

Sensoryneuron Sensory

receptor cellsFood

molecules

Tastepore

(b) Taste buds

Figure 50.25

Odorants

Brain

Nasal cavity

Receptors for differentodorants

Plasmamembrane

Odorants

potentialsAction

Olfactorybulb

Bone

Epithelialcell

Chemo-receptor

Cilia

Mucus

Sclera

Suspensoryligament

Cornea

Iris

Pupil

Aqueoushumor

Lens

Vitreous humor Optic disk

Centralartery andvein of the retina

Opticnerve

Fovea

Retina

ChoroidFigure 50.17aa

Retina

NeuronsPhotoreceptors

Rod Cone

Opticnervefibers Ganglion

cell

Amacrinecell

Bipolarcell

Horizontal cellPigmentedepithelium

Figure 50.17ab

CYTOSOL

INSIDE OF DISK

Retinal

OpsinRhodopsin

Figure 50.17bb

Figure 50.18

Light

Inactiverhodopsin

Activerhodopsin

Transducin

Phosphodiesterase

INSIDE OF DISK

Diskmembrane

CYTOSOL

GMP

cGMP

Na

Na

EXTRA-CELLULARFLUID

Plasmamembrane

Dark Light

Hyper-polarization

Time

0

40

70Mem

bra

ne

po

ten

tial

(m

V)

Outer ear Middle ear Inner ear

Skullbone

MalleusIncus

Stapes Semicircularcanals

Auditory nerveto brain

Cochlea

Eustachiantube

Roundwindow

Ovalwindow

Tympanicmembrane

AuditorycanalPinna

Figure 50.10a

Figure 50.10b

Cochlearduct

BoneAuditorynerve

Vestibularcanal

Tympaniccanal

Organof Corti

Figure 50.10c

Tectorial membrane

Basilarmembrane

Hair cells Axons ofsensoryneurons

To auditorynerve

Figure 50.10d

1 m

Bundled hairs projecting from a hair cell

Figure 50.12

Tympanicmembrane

Cochlea

Stapes

Base

(a)

Roundwindow

Point A

A

A

10Tympaniccanal

Basilarmembrane

Point B

B

B

20

Point C

C

C

30

Apex

Vestibularcanal

Oval window

Axons ofsensory neurons

(b)

3

3

3

0

0

00

Distance from oval window (mm)

6,000 Hz

1,000 Hz

100 Hz

Re

lati

ve

mo

tio

n o

f b

as

ila

r m

em

bra

ne

Semicircularcanals

Vestibularnerve

Vestibule

Utricle

Saccule

PERILYMPH

Fluidflow

Cupula

Hairs

Haircell

Nervefibers

Body movement

Figure 50.13