What is the function of the supporting cells of the nasal epithelium?
Ans: pg. 573 – to provide physical support, nourishment, and electrical insulation for the olfactory receptor cells, and to help detoxify chemicals that come in contact with the olfactory epithelium
How do basal cells contribute to olfaction?
Ans: pg. 573 – they produce new olfactory receptor cells
Olfactory receptor cells are unique among neurons because they can undergo what process?
Ans: pg. 573 – cell division
Why must the olfactory epithelium have a coating of mucus?
Ans: pg. 573 – to moisten the surface of the olfactory epithelium and dissolve odorants
What is the sequence of events from the binding of an odorant molecule to an olfactory hair to the arrival of a nerve impulse in an olfactory bulb?
Ans: pg. 573 – odorant binds to a receptor protein (odorant binding protein) and activates adenylate cyclase resulting in the production of cyclic adenosine monophosphate → sodium ion channels open → inflow of Na+ → depolarizing generator potential → action potential triggered → nerve impulses propagate along axon of olfactory receptor cell
How long would it take for your olfactory receptor cells to adapt to the smell of something very rotten?
Ans: pg. 574 – about one minute
What is the difference between the olfactory nerves, olfactory bulbs, and olfactory tract in the olfactory pathway?
Ans: pg. 574 – olfactory nerves: formed by bundles of unmyelinated axons of olfactory receptor cells, first-order neurons; olfactory bulbs: distal ends of the olfactory nerves, site of synapse of olfactory nerves with dendrites and cell bodies of second-order neurons (olfactory bulb neurons); olfactory tract: formed by axons of second-order olfactory bulb neurons, project to the limbic system and hypothalamus
For each of the primary tastes, give an example of a food that strongly represents that taste.
Why does a cold or allergy reduce your sense of taste?
Ans: pg. 576 – it reduces the sense of smell which is the major part of taste
Where on the tongue are each of the four types of papillae located?
Ans: pg. 577 – 1) circumvallate: form an inverted V-shaped row at the back of the tongue; 2) fungiform: scattered over the entire surface of the tongue; 3) foliate: located in small trenches on the lateral margins of the tongue; 4) filiform: over the entire surface of the tongue
What is the function of supporting cells in taste buds?
What must happen to odorant and tastant molecules before they can be sensed?
Ans: pg. 576 – they must be dissolved in an aqueous solution (saliva or fluids coating nasal membranes)
Which type of receptors are olfactory and gustatory receptor cells?
Ans: pg. 576 – chemoreceptors
How do the receptor cells for olfaction and gustation differ in structure and function?
Ans: pg. 572, 577 –structure: olfactory receptor cells are bipolar neurons with a nonmotile cilia that projects from the dendrite; whereas, gustatory receptor cells have a single, long microvillus (gustatory hair) that projects from the receptor cell to the external surface; function: olfactory cells are receptors for the sense of smell; whereas, gustatory cells are receptors for the sense of taste
What is the sequence of events from the binding of a tastant molecule to a gustatory hair to the generation of an action potential in a first-order gustatory neuron?
Ans: pg. 577 – release of neurotransmitter molecules from the gustatory receptor cell with the neurotransmitter triggering action potentials in the first-order neurons
Why is the low threshold of bitter substances a survival advantage?
Where is aqueous humor produced, what is its circulation path, and where does it drain from the eyeball?
Ans: pg. 587 – 1) from blood capillaries in the ciliary processes; 2) from blood capillaries in the ciliary processes into the posterior chamber, then forward between the iris and lens, through the pupil, and into the anterior chamber; 3) into the scleral venous sinus (canal of Schlemm) and then into the blood
What is the function of the aqueous humor? The vitreous body?
Ans: pg. 587 – a) nourishes the lens and cornea; b) contributes to intraocular pressure holding the retina flush against the choroids
What separates the anterior and posterior chambers of the eyeball? The anterior cavity from the vitreous chamber?
Ans: pg. 587 – a) iris and ciliary process; b) suspensory ligaments and lens
Which characteristics allow the lens to transmit light?
Ans: pg. 587 – proteins (crystallins) arranged like the layers of an onion
Why are we unable to see an image that strikes the blind spot?
Ans: pg. 587 – it contains no rods or cones
What is refraction? Which components of the eye are primarily responsible for refracting light?
Ans: pg. 590 – a) bending of light rays; b) cornea, lens
If you were looking at the horizon, trying to determine where you were (focusing on the distance), then looking down to read a map (focusing up close), which process must your eyes accomplish to keep your vision focused?
Ans: pg. 591 – accommodation
Which sequence of events occurs when you look at a distant object? When you look at a close object?
Ans: pg. 591 – a) ciliary muscle is relaxed and lens is flattened due to being stretched in all directions; b) ciliary muscle contacts, the ciliary muscle is pulled toward the lens which pulls the ciliary process forward the lens, ciliary process moves forward toward the lens which releases tension on the lens and suspensory ligaments, which allows the lens to become more spherical
Which refraction abnormality do you likely have if both near and far objects are out of focus?
Ans: pg. 591 – astigmatism
What is convergence? Why is it important for human vision?
Why would excess cerumen in the external auditory canal muffle incoming sounds?
Ans: pg. 600 – it would prevent sound waves from traveling easily through the external auditory canal and striking the tympanic membrane
How are sound waves transmitted from the auricles to the spiral organ?
Ans: pg. 606 – from auricles into external auditory canal to tympanic membrane to ear ossicles to oval window setting up fluid pressure waves in the cochlea in the scala vestibule to the scala tympani which pushes the vestibular membrane back and forth creating pressure waves in the in the endolymph inside the cochlear duct which causes the basilar membrane to vibrate, which moves the hair cells of the spiral organ against the tectorial membrane, which binds the hair cell microvilli, which produces receptor potentials
How does the tympanic membrane respond to quieter sounds? To low-pitched sounds?
Ans: pg. 606 – it moves more slowly
If fluid waves in the cochlea bounced back and forth, sounds would echo inside your cochlea. What stops fluid waves from traveling more than once through the cochlea?
Which part of the basilar membrane vibrates most vigorously in response to banging on a bass drum (low-frequency sounds)? How would the basilar membrane respond to someone quietly whispering (low-intensity sounds)?
Ans: pg. 606 – a) the portion of the basilar membrane toward the apex of the cochlea near the helicotrema; b) with smaller vibrations
How is the human ear able to identify the origin of a sound?
Ans: pg. 607 – via slight differences in the timing of impulses arriving from the two ears to the pons
What is the pathway for auditory impulses from the cochlea to the cerebral cortex?
Ans: pg. 607 – cochlea to cochlear nerve to vestibulocochlear nerve to medulla oblongata to pons to midbrain to thalamus to primary auditory area in the superior temporal lobe of the cerebral cortex
What is the difference between static and dynamic equilibrium?
Ans: pg. 610 – static equilibrium refers to the maintenance of the position of the body relative to the force of gravity; whereas, dynamic equilibrium is the maintenance of body position in response to sudden movements such as rotation, acceleration, and deceleration
How are the receptors for hearing and equilibrium structurally similar?
If you were blindfolded, would maculae or cristae sense that you were hanging upside-down? Where are maculae and cristae each found?
Ans: pg. 610 – a) macula; b) maculae are in the saccule and utricle of the vestibule and the cristae are in the semicircular canals
What function is served by the otoliths?
Ans: pg. 610 – add weight to the otolithic membrane, amplifying the pull of gravity during movements
Why do we need three, rather than one or two, semicircular canals?
Ans: pg. 610 – the ducts lie at right angles to one another allow them to respond to virtually any rotation movement of the head
With which type of equilibrium are the semicircular ducts, the utricle, and the saccule associated?
Ans: pg. 610 – 1) semicircular ducts: rotational movements; 2) utricle and saccule: straight-line changes in speed and direction
Where do axons in the vestibular branch of the vestibulocochlear nerve terminate? What purposes are served by the transmission of equilibrium input to these locations?
Ans: pg. 610 – a) medulla oblongata and pons; b) axons from the medulla and pons extend to the nuclei of cranial nerves that control eye movement and to the nucleus of the accessory nerve that helps control head and neck movements