Biology, Seventh Edition
Solomon • Berg • Martin
Chapter 41
Sensory Reception
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Sensory receptors
• Neuron endings
• Specialized receptor cells in
close contact with neurons
• Sense organs
• Sensory receptors
• Accessory cells
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Mechanoreceptors
• Transduce mechanical energy
• Animal functions
–Feeling
–Hearing
–Maintaining balance
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Chemoreceptors
• Transduce certain kinds of
chemical compounds
• Allow taste and olfaction
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Thermoreceptors
• Transduce thermal energy
• In endothermic animals,
thermoreceptors provide cues
about body temperature
• Some invertebrates use
thermoreceptors to locate
endothermic prey
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Biology, Seventh Edition
Thermoreception
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CHAPTER 41 Sensory Perception
Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Electroreceptors
• Used by predatory fishes to
detect prey
• Respond to electrical stimuli
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Photoreceptors
• Transduce light energy
• Serve as the sensory receptors in
eyespots and eyes
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Receptor cells
• Absorb energy
• Transduce it into electrical energy
• Produce receptor potentials
–Depolarizations or
hyperpolarizations of the membrane
–Graded responses
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Sensation process
• Sensory receptors transmit coded
signals
• Brain interprets signals
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Sensory adaptation
• Decrease in frequency of action
potentials in a sensory neuron
• Occurs even when the stimulus is
maintained
• Decreases response to the
stimulus
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Mechanoreceptors
• Touch
• Pressure
• Gravity
• Stretch
• Movement
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Mechanoreceptors are
activated when they change
shape as a result of being
mechanically pushed or pulled
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Tactile receptors
• Found in the skin
• Respond to mechanical
displacement of hairs
• Respond to displacement of the
receptor cells
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CHAPTER 41 Sensory Perception
• Nociceptors
• Pain receptors
• Free nerve endings of certain
sensory neurons
–Strong tactile stimuli
–Temperature extremes
–Certain chemicals
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CHAPTER 41 Sensory Perception
• Proprioceptors
• Enable the animal to perceive
orientation of the body and
positions of its parts
–Muscle spindles
–Golgi tendon organs
–Joint receptors
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
Proprioceptors
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Statocysts
• Gravity receptors
• Found in many invertebrates
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
Statocysts
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CHAPTER 41 Sensory Perception
• Vertebrate hair cells
• Detect movement
• Found in
–Lateral line of fishes
–Vestibular apparatus
–Semicircular canals
–Cochlea
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Vertebrate hair cells
• Single kinocilium
–True cilium
• Stereocilia
–Microvilli
–Contain actin filaments
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CHAPTER 41 Sensory Perception
• Lateral line organs
• Supplement vision in fish and
some amphibians
• Inform the animal of moving
objects or objects in its path
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CHAPTER 41 Sensory Perception
Lateral line organ
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Vertebrate inner ear
• Labyrinth of fluid-filled chambers
• Canals that help maintain
equilibrium
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Vestibular apparatus
• Upper part of the labyrinth
• Saccule
• Utricle
• Semicircular canals
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CHAPTER 41 Sensory Perception
Human ear
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Otoliths
• Stimulate hair cells that send
signals to the brain
• Enable the animal to perceive the
direction of gravity
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CHAPTER 41 Sensory Perception
• Saccule and utricle
• Change position when the head
is tilted
• Change position when the body
is moving in a straight line
• Semicircular canals
• Inform the brain about turning
movements
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CHAPTER 41 Sensory Perception
Inner ear
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CHAPTER 41 Sensory Perception
• Cristae
• Clumps of hair cells
• Located within each bulblike
enlargement
• Stimulated by movements of the
endolymph
–Fluid that fills each canal
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CHAPTER 41 Sensory Perception
• Organ of Corti
• Found within the cochlea
• Contains auditory receptors
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CHAPTER 41 Sensory Perception
• Path taken by sound waves
• Sound waves pass through the
external auditory canal
• Tympanic membrane (eardrum)
vibrates
• Ear bones transmit and amplify
the vibrations through the middle
ear
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CHAPTER 41 Sensory Perception
• Vibrations pass through the oval
window to fluid within the
vestibular duct
• Pressure waves press on the
membranes that separate the
three ducts of the cochlea
• Bulging of the round window
serves as a pressure escape
valve
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Pressure waves cause
movements of the basilar
membrane
• Movements stimulate the hair
cells of the organ of Corti by
rubbing them against the
overlying tectorial membrane
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CHAPTER 41 Sensory Perception
• Neural impulses
• Initiated in the dendrites of
neurons that lie at the base of
each hair cell
• Transmitted by the cochlear
nerve to the brain
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CHAPTER 41 Sensory Perception
• Chemoreceptors for taste and
smell
• Taste receptor cells
–Specialized epithelial cells in taste
buds
• Olfactory epithelium
–Specialized olfactory cells
–Axons that extend to the brain
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CHAPTER 41 Sensory Perception
Olfactory
epithelium
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CHAPTER 41 Sensory Perception
• Taste and smell process
• Molecule binds with a receptor
–Taste receptor cell
–Olfactory receptor cell
• Signal transduction process
involving a G protein is initiated
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CHAPTER 41 Sensory Perception
• Eyespots (ocelli)
• Found in cnidarians and
flatworms
• Detect light
• Do not form images
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CHAPTER 41 Sensory Perception
Eyespots
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CHAPTER 41 Sensory Perception
• Compound eye of insects and
crustaceans
• Visual units called ommatidia
–Collectively produce a mosaic
image
–Transparent lens
–Crystalline cone
–Focuses light onto retinular receptor
cells
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Human eye structures and
functions
• Light enters through the cornea
• Light is focused by the lens
• Image is produced on the retina
• Iris regulates the amount of light
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
Human eye
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Photoreceptor cells in the retina
• Rods
–Function in dim light
–Black and white images
• Cones
–Function in bright light
–Color vision
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CHAPTER 41 Sensory Perception
• Bipolar cells
• Send signals to ganglion cells
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CHAPTER 41 Sensory Perception
• Lateral interneurons
• Integrate information
• Horizontal cells
–Receive signals from the rods and
cones
–Send signals to bipolar cells
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Amacrine cells
–Receive signals from bipolar cells
–Send signals back to bipolar cells
and to ganglion cells
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CHAPTER 41 Sensory Perception
Neural pathway
in the retina
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• Human vision process
• Light strikes the photopigment
rhodopsin in the rod cells
• Retinal portion changes shape
• Initiates a signal transduction
process that involves transducin
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Biology, Seventh Edition
CHAPTER 41 Sensory Perception
• G protein activates an esterase
that hydrolyzes cGMP
• Reduces cGMP concentration
• Ion channels close
• Membrane becomes
hyperpolarized
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CHAPTER 41 Sensory Perception
• Rod cells release less glutamate
• Fewer signals are transmitted
• Bipolar cells become depolarized
• Bipolar cells release
neurotransmitter that stimulates
ganglion cells
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