Chapter 9: Senses
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110 Terms
What is sensation?
The process initiated by stimulating sensory receptors.
What is perception?
Conscious awareness of stimuli received by sensory neurons.
What are the general senses?
Touch, pressure, pain, temperature, itch, vibration, and proprioception.
What are the special senses?
Smell, taste, vision, hearing, and equilibrium.
What is proprioception?
The sense of body position and movement.
What do mechanoreceptors detect?
Mechanical stimuli such as touch, pressure, and vibration.
What do chemoreceptors detect?
Chemicals, such as odors and tastes.
What do photoreceptors detect?
Light.
What do thermoreceptors detect?
Temperature changes.
What do nociceptors detect?
Painful or potentially damaging stimuli.
What are free nerve endings?
Simple, common receptors that detect pain, temperature, itch, and some movement.
What do Merkel's disks detect?
Light touch and superficial pressure.
What do hair follicle receptors detect?
Light touch.
What do Meissner corpuscles detect?
Touch and help localize tactile sensations.
What do Ruffini corpuscles detect?
Continuous pressure.
What do Pacinian corpuscles detect?
Deep pressure, vibration, and position/proprioception.
What is sensory adaptation?
Decreased sensitivity to a continued stimulus.
Why does adaptation occur?
The nervous system becomes less responsive to an unchanging stimulus.
Give an example of adaptation.
Eventually no longer noticing the weight of a coat you're wearing.
What is olfaction?
The sense of smell.
Where are olfactory receptors located?
In the olfactory epithelium in the superior nasal cavity.
What type of neurons are olfactory receptors?
Bipolar neurons.
What stimulates olfactory receptors?
Odorant molecules dissolved in mucus.
What cranial nerve is responsible for olfaction?
CN I, the olfactory nerve.
What is the basic olfactory pathway?
Odorant → olfactory receptors → olfactory bulb → brain.
Which brain lobes process olfactory information?
Frontal and temporal lobes.
Does olfactory information pass through the thalamus first?
No.
What causes olfactory adaptation?
Feedback loops that inhibit action-potential transmission.
What is gustation?
The sense of taste.
Where are taste buds located?
On tongue papillae, the hard palate, and throat.
About how many taste cells are in each taste bud?
About 40 taste cells.
What are the five basic tastes?
Sweet, sour, salty, bitter, and umami.
What happens when chemicals bind to taste receptors?
They initiate action potentials in taste cells.
Where does taste information reach in the cerebral cortex?
The insula.
How are taste and smell related?
They work together to produce the perception of flavor.
What are the three divisions of the ear?
External ear, middle ear, and inner ear.
What structures make up the external ear?
Auricle, external acoustic meatus, and tympanic membrane.
What is the auricle?
The fleshy external portion of the ear.
What is the external acoustic meatus?
The ear canal leading to the tympanic membrane.
What is the tympanic membrane?
The eardrum that vibrates when sound waves hit it.
What are the three auditory ossicles?
Malleus, incus, and stapes.
What is the order of the auditory ossicles?
Malleus → incus → stapes
What does the stapes connect to?
The oval window.
What is the function of the auditory ossicles?
They transmit and amplify sound vibrations.
What does the auditory/Eustachian tube do?
Equalizes air pressure in the middle ear.
What are the major structures of the inner ear?
Cochlea, vestibule, and semicircular canals.
What structure is responsible for hearing?
The cochlea.
What structure is responsible for static equilibrium?
The vestibule.
What structures are responsible for dynamic equilibrium?
The semicircular canals.
What is the basic pathway of sound through the ear?
Ear canal → tympanic membrane → ossicles → oval window → cochlea
What happens when sound reaches the tympanic membrane?
The membrane vibrates.
What does the stapes do?
Transmits vibrations to the oval window.
What is the cochlea?
A snail-shaped inner-ear structure responsible for hearing.
What are the three channels of the cochlea?
Scala vestibuli, cochlear duct, and scala tympani.
What fluid is in the cochlear duct?
Endolymph.
What fluid is in the scala vestibuli and scala tympani?
Perilymph.
What is the spiral organ/organ of Corti?
A sensory structure in the cochlear duct containing hair cells.
What happens when hair cells bend?
Action potentials are generated.
What determines pitch?
Frequency or wavelength of the sound.
What determines volume?
Amplitude of the sound wave.
What nerve carries hearing information?
The cochlear nerve, part of CN VIII.
What is CN VIII?
The vestibulocochlear nerve.
What is the basic hearing pathway?
Cochlea → cochlear nerve → brainstem → inferior colliculus → thalamus → auditory cortex.
What is equilibrium?
The ability to detect changes in body/head position
What is static equilibrium?
Detects head position relative to gravity.
What structures are involved in static equilibrium?
The vestibule, utricle, and saccule.
What are maculae?
Specialized patches containing hair cells in the utricle and saccule.
What are otoliths?
Protein and calcium carbonate particles that respond to gravity.
How do otoliths help detect head position?
Their movement bends hair cells and initiates action potentials.
What is dynamic equilibrium?
Detects changes in the direction and rate of head movement.
What structures detect dynamic equilibrium?
The semicircular canals.
What is the ampulla?
A swelling at the base of a semicircular canal
What is the crista ampullaris?
A sensory structure inside the ampulla.
What is the cupula?
A gelatinous structure containing the hair-cell microvilli.
How does dynamic equilibrium work?
Head movement moves endolymph, which bends the cupula and hair cells.
What nerve carries equilibrium information?
The vestibular nerve, part of CN VIII.
What are the three layers/tunics of the eye?
Fibrous, vascular, and nervous tunics.
What structures make up the fibrous tunic?
Sclera and cornea.
What is the sclera?
The firm white outer layer that protects and maintains eye shape.
What is the cornea?
The transparent anterior portion that allows and focuses light.
What structures are part of the vascular tunic?
Choroid, ciliary body, iris, and related structures.
What does the choroid do?
Contains melanin, absorbs light, and prevents reflection.
What does the ciliary body do?
Helps hold the lens and controls its shape.
What is the iris?
The colored part of the eye that regulates pupil size.
What is the pupil?
The opening that regulates how much light enters the eye.
What is the lens?
A flexible, biconvex structure that focuses light on the retina.
What is the nervous tunic?
The retina.
What are the two layers of the retina?
Pigmented retina and sensory retina.
What does the pigmented retina do?
Prevents light from reflecting inside the eye.
What does the sensory retina contain?
Photoreceptors and interneurons.
What are the two types of photoreceptors?
Rods and cones.
What do rods detect?
Light, especially in dim conditions.
What do cones detect?
Color vision.
What are the three types of cones?
Blue, green, and red.
What is the fovea centralis?
The center of the macula containing only cones for fine vision.
What is the optic disk?
The area where the optic nerve leaves the eye.
Why is the optic disk called the blind spot?
It contains no photoreceptors.
What is the retinal pathway for visual information?
Rods/cones → bipolar cells → ganglion cells → optic nerve.
What is accommodation?
Changing the lens shape to focus an image on the retina.
What happens to the lens during distant vision?
Ciliary muscles relax and the lens flattens.