Name______________________________________________________Period_______
Sensory Reception Notes
AP Biology
Mrs. Laux
I. Sensory receptors
-specialized, respond to specific energy stimuli in the environment
-link animal to outside world
-species specific
-ex: echolocation in bats, UV light in insects, dogs/cats-high-pitched
whistles
-humans-best sense: sight
A. Sensory receptors
-neuron endings or specialized receptor cells in close contact with
neurons
-receptors transduce (convert) energy of stimulus to electrical
signals
-transmit impulses to CNS
B. Sense organs (eyes, ears (sound and balance), nose, taste buds, skintouch, pressure, pain and temperature)
-composed of sensory receptors and accessory cells.
II. Different kinds of sensory receptors
A. Exteroreceptors
-receive information from the outside world
-find food, attract mate, detect enemies
B. Proprioceptors
-sensory receptors within muscles, tendons, and joints
-enable the animal to perceive orientation of the body and the
positions of its parts
-can dress, eat in dark
C. Interoceptors
-sensory receptors within body organs
-help maintain homeostasis
-detect changes in pH, osmotic pressure, body temp, chem.
composition of blood
-can perceive thirst, hunger, nausea, pain, orgasm
III. Based on the types of stimuli to which they respond, sensory receptors also
may be classified as:
A. Mechanoreceptors
-respond to touch, pressure, gravity, stretching, movement
B. Chemoreceptors
-respond to certain chemical compounds
C. Photoreceptors
-detect light energy
D. Thermoreceptors
-respond to heat and cold
E. Electroreceptors
-detect electrical energy (fish)
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Name______________________________________________________Period_______
Sensory Reception Notes
AP Biology
Mrs. Laux
IV. Receptor cells
-absorb energy; particular to the receptor
-ex: eye: rods/cones-light energy
skin: thermal energy (heat)
-transduce (convert) that energy into electrical energy
-produce receptor potentials (change in membrane potential)
-depolarizations-potential decreases (charge difference)
-above threshold, creates action potential
-hyperpolarizations-potential increases (charge difference)
-message decoded in brain
-intensity depends on:
-number of neurons transmitting action potentials
-frequency of firing
V. Sensory adaptation to a continuous stimulus results in decreased response to
that stimulus
-occurs for 2 reasons:
1. receptor produces smaller receptor potentialÆlower frequency of
action potentials
2. release of neurotransmitter decreases at presynaptic terminal
-pain/cold do NOT adapt
A. Receptors that adapt slowly or not at all
-tonic receptors
B. Receptors that adapt rapidly are phasic receptors
-don’t feel clothes after awhile
-can ignore unpleasant or unimportant stimuli
VI. Mechanoreceptors respond to
-touch, pressure, gravity, stretch, or movement
-allow awareness of food in stomach, feces in rectum, urine in
bladder, fetus in uterus
A. The tactile receptors in the skin respond to
-mechanical displacement of hairs
-displacement of the receptor cells themselves
-ex: Merkel’s discs-touch, pressure, slow adaptation
-ex: Pacinian corpuscle responds deep pressure, esp.
vibrations
-ex: Meissner corpuscles-light touch, pressure, adapt quickly
-ex: Ruffini corpuscles-adapt slowly, heavy touch and
pressure
B. Statocysts
-gravity receptors
-found in many invertebrates
-infolding of epidermis, lined with sensory hair cells
-cavity contains statoliths-loose sand grains or CaCO3
-particles pulled downward by gravity; tells organism position
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Name______________________________________________________Period_______
Sensory Reception Notes
AP Biology
Mrs. Laux
C. Lateral line organs
-supplement vision in fish and some amphibians
-inform animal of moving objects or objects in its path
-detect vibrations in water
D. Proprioceptors: 3 main types; all tonic
1. Muscle spindles-muscle movement
2. Golgi tendon organs-tendon stretch
3. joint receptors-ligament stretch
-continually respond to tension and movement in the muscles and
joints
-allow us to do complicated, skillful acts
-ex: playing the piano with eyes closed
E. The vertebrate inner ear
-hearing, but mostly equilibrium-also proprioceptors in feet, visual
cues
-consists of a labyrinth of fluid-filled chambers and canals
-vestibular apparatus in the upper part of the labyrinth
-consists of the saccule, utricle, and 3 semicircular canals
1. The saccule and utricle contain otoliths (small CaCO3 ear
stones) that change position when the head is tilted or when the
body is moving in a straight line (linear acceleration). The hair cells
stimulated by otoliths send impulses to the brain, enabling the
animal to perceive the direction of gravity.
2. The semicircular canals inform the brain about turning
movements (angular acceleration). The cristae within each ampulla
are stimulated by movements of the endolymph, a fluid that fills
each canal; no otoliths here
-most movement is horizontal
-vertical movement, elevator or ship pitching causes
seasickness
F. In birds and mammals, the organ of Corti within the cochlea contains
auditory receptors.
-cochlea-spiral tube, resembles snail’s shell
1. Sound waves pass through the external auditory canal, cause
the eardrum (tympanic membrane) to vibrate, and are amplified and
transmitted through the middle ear by the malleus, incus, and
stapes.
2. Vibrations pass through the oval window to fluid (perilymph)
within the vestibular duct. Pressure waves press on the
membranes that separate the three ducts of the cochlea.
3. The bulging of the round window serves as an escape valve for
the pressure. The pressure waves cause movements of the basilar
membrane. These movements stimulate the hair cells of the organ
of Corti by rubbing them against the overlying tectorial membrane.
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Name______________________________________________________Period_______
Sensory Reception Notes
AP Biology
Mrs. Laux
4. Nerve impulses are initiated in the dendrites of neurons that lie at
the base of each hair cell, and neural impulses are transmitted by
the cochlear nerve to the brain.
VII. Chemoreceptors include receptors for taste (gustation) and smell (olfaction)
-unlike most neurons, are continuously regenerated
-used in intraspecific communication-pheromones
A. Taste receptors
-taste buds in mouth, located in papillae (tiny elevations)
-specialized epithelial cells in taste buds
-detect dissolved food molecules
-sweet, salty, bitter, sour
-flavor combo of these, plus temp, smell, texture of food
-no taste with a cold
-ability to taste PTC-dominant trait
-ability to taste PROP-1 supertaster:2 regular tasters:1
non-taster
B. The olfactory epithelium
-roof of nasal cavity
-contains specialized olfactory cells (100 million) with axons that
extend to the brain as fibers of the olfactory nerves (1st cranial
nerve)
-when a molecule binds with a receptor on an olfactory receptor
cell, a signal transduction process involving a G protein is initiated,
leading to depolarization
-humans can detect 7 main groups of smells
-camphor, musk, floral, peppermint, ethereal, pungent, putrid
-can perceive 10,000 scents
VIII. Thermoreceptors
-important in endothermic animals
-detect heat, cold, and pain (extreme temps)
-provide cues about body temperature
-ex: hypothalamus maintains homeostasis
-in some invertebrates are used to locate an endothermic host
-ex: mosquitoes, ticks, blood-sucking arthropods
IX. Electroreceptors
-detect electrical currents in water, Earth’s magnetic field
-used by predatory fishes to detect prey
-ex: sharks, rays, bony fishes
-used in murky waters to navigate
-deliver powerful shocks to stun prey
-ex: electric eels or rays
X. Photoreceptors
-in eyespots or ocelli
-detect light, but do not form images effectively
Effective image formation and interpretation are called vision.
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Name______________________________________________________Period_______
Sensory Reception Notes
AP Biology
Mrs. Laux
A. The compound eye of insects and crustaceans
-consists of visual units called ommatidia
-collectively produce a mosaic image
-each ommatidium has a transparent lens and a crystalline cone
-focus light onto receptor cells, called retinular cells.
B. In the human eye
-light enters through the cornea
-focused by the lens
-produces an image on the retina
-iris regulates the amount of light that can enter
C. The retina
-contains photoreceptor cells:
-rods function in dim light
-form images in black and white
-cones function in bright light
-permit color vision.
D. In addition to the rods and cones, the retina contains
-bipolar cells
-ganglion cells
- axons of the ganglion cells make up the optic nerve
-horizontal cells
-amacrine cells
-interneurons that integrate information in the retina.
E. When light strikes rhodopsin in the rod cells, the retinal portion of the
rhodopsin molecule changes shape and initiates a signal transduction
process that involves a G protein. The membrane becomes
hyperpolarized and less inhibitory neurotransmitter is released. Bipolar
and ganglion cells are affected.
F. The optic nerves transmit information to the lateral geniculate nuclei in
the thalamus. From there neurons project to the primary visual cortex and
then to integration centers in the cerebral cortex
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