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Sensory systems
Chapter 50
Five senses
Touch
Taste
Smell
Sound
Vision
Sensory systems
Sensory info is received
Nerve impulse or action potential
All or nothing response
Response depends on part of brain
that receives the info
Sensory information
Sensory info to CNS
1. Sensory reception
2. Transduction
Graded potential
Ion channels open or close
Receptor potential
Change in membrane potential
Depolarization
Sensory information
3. Transmission
Goes to CNS via afferent pathway
4. Interpretation
Perception by the brain
Sensory receptors
Nerve endings
Specialized neurons or epithelial cells
Associated with sensory organs -eyes
All stimuli is a form of energy
Sensory receptors
Stimuli-outside body
Heat, light, pressure & chemicals
Stimuli-inside body
BP, body position, body temperature
Types of sensory receptors
Mechanoreceptors
– Pressure, stretch, touch
Chemoreceptors
– chemicals
Electromagnetic receptors
(photoreceptors)
Nociceptors (pain)
Thermoreceptors
Receptors
Cutaneous receptors:
Skin
Heat, cold, pressure, pain & touch
Thermoreceptors
Heat/Cold
Hypothalamus
– Regulates temp of blood (core temp)
Receptors
Mechanoreceptors
Touch
Close to surface of skin
Hair follicle receptors
Pressure
Deeper
skin
Heat
Gentle
touch
Pain
Cold
Hair
Epidermis
Dermis
Hypodermis
Nerve
Connective
tissue
Hair
movement
Strong
pressure
Receptors
Nociceptors:
Pain
Severe temperature change
Tissue damage
Free nerve endings (naked dendrites)
Located in the epidermis
PAIN
Receptors
Proprioceptors
Give info on animal’s body parts
Position
Movement
Stretch receptors on muscle
Prevent over stretch
Receptors
Baroreceptors:
Detect tension or stretch in blood
vessel walls
Internal carotids
Aortic arch
Drop in BP
Stimulation to increase HR &
vasoconstriction
Receptors
Chemoreceptor
Aorta & carotid
Medulla oblongata
pH (blood & CSF)
Slow breathing
Increased CO2
Lowers pH
Causes an increased respiration rate
Taste
Taste buds
Collections of receptor cells
Epithelial cells
Papillae
Raised areas on tongue
Taste buds located
Taste
Taste buds contain
50-100 taste cells
Food dissolves in
saliva
Contact taste cells
Taste salty, sweet,
sour, bitter
Taste
Chemoreceptors
Salt: Na+1
Sour: H+1
Directly through ion-channel
Sweet: receptor proteins for sugar
Bitter: K+channels are closed by
receptor proteins
Papilla
Papillae
Taste
buds
Tongue
(a) The tongue
Sweet
Salty
Sour
Bitter
Umami
Taste bud
Taste
pore
Sensory
neuron
(b) A taste bud
Sensory
receptor
cells
Food
molecules
Sweet
Sugar molecule
G protein
Sweet
receptor
Tongue
Taste pore
Taste
bud
Sugar
molecule
Phospholipase C
SENSORY
RECEPTOR
CELL
PIP2
Sensory
receptor
cells
IP3
(second
messenger)
Sensory
neuron
Nucleus
ER
IP3-gated
calcium
channel
Ca2+
(second
messenger)
Sodium
channel
Na+
Smell
Olfactory receptors
Chemoreceptors
Located upper portions of nasal passages
Dendrites are in cilia
Axon goes directly to cerebral cortex
Odorant or odorous substance binds
proteins
Second messenger response in receptor
cell
Smell
Opens membrane to Ca & Na
Causes impulse (action potential)
Distinguish thousands of odors
Very accurate
Single odorant molecule
NOSE
Nose
Brain
Action potentials
Olfactory
bulb
Odorants
Nasal cavity
Bone
Epithelial
cell
Odorant
receptors
Chemoreceptor
Plasma
membrane
Odorants
Cilia
Mucus
Hearing
Outer ear:
Pinna, canal
Middle ear:
Tympanic membrane (ear drum)
Eustachian tube
Small bones (malleus, incus, stapes)
Inner ear:
Cochlea, auditory nerve
Figure 50.10a
Middle ear
Outer ear
Skull
bone
Inner ear
Stapes
Incus
Malleus
Semicircular
canals
Auditory
nerve to brain
Cochlea
Pinna
Auditory
canal
Oval
window
Tympanic
Round
membrane
window
Eustachian
tube
Ear
Hearing
Vibrations move in canal
Cause eardrum to move
Vibrations pass through the bones
Stapes pass vibration to inner ear
Causes pressure waves in fluid in
cochlea
Basilar membrane of the cochlea
vibrates
Hearing
Hair cells on membrane vibrate
Leads to change in membrane
potentials in sensory neurons
Sound interpreted
Humans hear 20-20,000 hertz
Age decreases higher frequencies
Dogs hear sounds at 40,000 hertz
Ears
Inner ear
Body position & balance
Two chambers near the cochlea
Utricle & saccule
Filled with fluid
Hair cells in chambers respond to
changes in head positions
Ears
Utricle: horizontal motion
Saccule: vertical motion
Different movement causes different
sensory neurons to be stimulate
Labyrinth system
Spin around become dizzy
Equilibrium
Semicircular canals
Flow of fluid
Vestibular nerve
Cupula
Hairs
Hair
cells
Axons
Vestibule
Utricle
Saccule
Body movement
Eye
Sclera:
White outer layer of connective tissue
Conjunctiva:
Epithelial layer
Covers outer surface of sclera
Under surface of the eyelid
Cornea:
Clear part of sclera, light passes through
Eye
Choroid
Pigmented layer under the sclera
Iris
Color part of eye formed by the choroid
Pupil
Opening at the center of the iris
Controlled by iris
Lens
Behind the pupil, held in place by ligaments
Eye
Retina
Back of eye where image is focused
Optic nerve
Sensory neurons
Vitreous humor
Jellylike substance behind the lens
Aqueous humor
Thinner fluid
Fills smaller chamber in front of the lens
EYE
Choroid
Sclera
Retina
Suspensory
ligament
Fovea
Cornea
Iris
Optic
nerve
Pupil
Aqueous
humor
Lens
Vitreous
humor
Optic
disk
Central
artery and
vein of
the retina
Eye
Light enters eye through cornea
Passes through pupil to lens
Lens focuses images on retina
Photoreceptor cells of retina
transduce light energy
Action potentials pass via sensory
neurons in the optic nerve
Eye
Rods & cones
Photoreceptors of eyes
Rods: black and white vision in dim
light
Cones: high visual acuity & color vision
Located in center of retina
EYE
Rods/cones
Retina
Choroid
Photoreceptors
Neurons
Retina
Light
Cone Rod
To
brain
Optic nerve
Light
Ganglion
cell
Amacrine
cell
Optic
nerve
axons
Horizontal
cell
Bipolar
cell
Pigmented
epithelium
Figure 50.17ba
Rod
Synaptic Cell
terminal body
Cone
Rod
Cone
Outer
segment
Disks
Eyes
Binocular vision
Axons of ganglion cells form optic nerves
Optic nerves meet at the optic chiasm
(base of the cerebral cortex)
Visions from the right visual field go to the
left side of the brain and vise versa
Thalamus
Cortex
Vision
Right
visual
field
Optic
chiasm
Right
eye
Left
eye
Left
visual
field
Optic nerve
Lateral
geniculate
nucleus
Primary
visual cortex
Near and Distance Vision
Eyes
Nearsightedness: longer eyeball
Farsightedness: shorter eyeball
Asitgmatism: problems with lens or
cornea
Light rays converge unevenly
Colorblindness: inherited lack of one
or more types of cones