Bio 1040 - Chapter 29 The Senses

Magnetoreceptors

- In migratory birds (pigeon beaks) and fish (trout noses). - Sense the orientation of the Earth's magnetic field.

Photoreceptors

- Most common type (as in eyes). - Detect various wavelengths of light (including ultraviolet, visible & infrared).

Three Main Subdivisions of the human ear:

- Outer Ear - Middle Ear - Inner Ear

"Somatic Sensory Systems" include

- Pain - Temperature - Pressure (touch) - Muscle sense

Outer ear includes:

- Pinna - Auditory Canal

Evolutionary significance of light detection:

- Plays a central role in the lives of nearly all animals. - Involves photoreceptor cells containing pigment molecules that absorb light. - Often involves some type of light-detecting organ (e.g. eye / eyespot). - Ranges from simple detection of light vs. darkness to forming complete images.

Pain Receptors

- Respond to excess heat, pressure or chemicals (prostaglandins) released from damaged or inflamed tissues. - Prostaglandins increase sensitivity of pain receptors. - Pain signals injury or disease; leads to retreat to safety.

Inner ear includes:

- Semi-circular canals - Cochlea

The "Chemical Senses" include

- Smell - Taste

Inner Ear Organs Include . . .

- Three Semicircular Canals & Ampullae - Utricle - Saccule

The "Physical Senses" includes

- Vision - Hearing - Balance

Stretch receptors

- in muscles & tendons. - Enable us to know body posture & position of body parts without seeing them.

The unit of frequency (i.e. "Hertz") refers to

"cycles per second"

Otoliths aka

"ear stones"

Venomous/predatory snakes have

"thermal pits" that can sense radiant body heat (IR radiation)

myopic

(nearsighted): such people can see close objects clearly, but cannot see objects clearly that are farther away

Middle ear includes:

- Eardrum - Three bones: Hammer, Anvil, Stirrup - Eustachian Tube

Types of Eyes Include . . .

- Eyespots - Compound eyes - Single-lens eyes

Mechanoreceptors

- Firm Touch - Light Touch - Stretch

Saccule

senses up & down motion (vertical motion).

Eyespots of Planaria are said to be __________________. Size of "cup" is misleading, i.e. does not correspond to white, rather black.

"inverted"

Muscle sense

- the ability to know/manipulate parts of your body without seeing them - e.g. as in a road sobriety test to touch your nose. - Another good example is the ability to reach into a bag of chips (after looking into the bag) and to pull out a specific chip w/o seeing into the bag while reaching.

Four Steps in Sensory Perception:

1. Reception 2. Transduction 3. Transmission 4. Processing

Sensory Transduction at a Taste Bud:

1. Stimulus (sugar molecules) are detected at the taste bud cell. 2. Sugar molecules bind to sweetness receptor in plasma membrane. 3. Sugar binding triggers a signal transduction cascade. 4. Ion channels open to create a receptor potential. 5. Neurotransmitter is released into synaptic cleft. 6. A series of action potentials are triggered in the sensory neuron. 7. Stronger stimuli release more neurotransmitter. 8. Frequency of impulses are processed into degree of sweetness. 9. Repeated stimuli lead to sensory adaptation.

Healthy humans can hear from

20 - 20,000 Hz

One day, you watch people reading in the library. A man aged 55 or so, without eyeglasses, is holding his book at arm's length, while a young girl sits bent over the table, her face almost touching the book in front of her. What visual deficits do these two people most likely have? - 55-year-old man: presbyopia::young girl: myopia - 55-year-old man: astigmatism::young girl: presbyopia - 55-year-old man: hyperopia::young girl: myopia - 55-year-old man: myopia::young girl: hyperopia - 55-year-old man: presbyopia::young girl: astigmatism

55-year-old man: presbyopia::young girl: myopia

vision: Rely on it for ______________% of the senses

80-90%

The Ear Converts Air Pressure Waves to _________________________ that Are Perceived As Sound.

Action Potentials

The Inner Ear Houses Our Organs of _____________

Balance

- High heat - High pressure

Cause tissue damage & release of prostaglandins

Thermoreceptors

Detect heat or cold.

There are five different receptors for taste. The receptor for sour could be detecting which of the following substances? - C6H12O6 - Cl- - Na+ - H+

H+

Sensory cells have cilia or microvilli (i.e. "hairs") that bend or deflect in relation to physical motion (e.g. sound waves, fluid displacement).

Important in the senses of hearing & balance.

Electromagnetic Receptors

Includes: - Photoreceptors - Electroreceptors - Magnetoreceptors

You are told by your optometrist that you have 20/40 vision in both eyes. What does this mean? - It means that your visual acuity is approximately 50% (20/40) of normal visual acuity. - It means that your vision is normal in one eye, but only 50% (20/40) normal in the other eye. - It means that you would have to stand 20 feet from an object to see it as clearly as a person with normal acuity could see it at 40 feet. - It means that you would have to stand 40 feet from an object to see it as clearly as a person with normal acuity could see it at 20 feet. - It means that your vision in one eye is 20/20 and in the other eye, 40/40.

It means that you would have to stand 20 feet from an object to see it as clearly as a person with normal acuity could see it at 40 feet.

Which is the first step of those listed in the transmission of a visual image to the brain? Note that these steps begin after light has entered the eye. - A network of neurons in the retina is activated. - Action potentials are conveyed along the optic nerve. - Receptor potentials are generated by rods and cones. - Integration sharpens images and increases contrast. - Light is absorbed by rhodopsin and photopsin.

Light is absorbed by rhodopsin and photopsin.

Individuals with vitamin A deficiency in childhood often suffer from blindness. What component of the eye most likely relies on vitamin A? A. Cones, because vitamin A is a component of their membranes. B. Rods, because they rely on rhodopsins. C. Cones, because they rely on rhodopsins. D. Rods, because they rely on photopsins.

Rods, because they rely on rhodopsins.

reason why you only hear the bass on an approaching car stereo

Low (bass) frequencies penetrate air farther than high frequencies

Which statement about the focusing of light by the eyes is true? A. Mammals focus light when a rigid lens is moved back and forth. B. Mammals use muscles and ligaments to change the shape of their lenses to focus light. C. Squids and many fishes change the shape of their lenses to focus light. D. Mammalian lenses thicken when focused on distant objects.

Mammals use muscles and ligaments to change the shape of their lenses to focus light.

Which of the following is a unique property of the sense of smell? - Olfactory receptor cells generate receptor potentials. - The sense of smell relies on chemoreceptors. - Olfactory receptor cells generate action potentials. - The input from receptor cells is sent to the brain. - There are five main smells that humans can distinguish.

Olfactory receptor cells generate action potentials.

Electroreceptors

On the head of the hammerhead shark, & bill of the duckbilled Platypus - detect electric fields generated by the muscles of prey.

Hearing Range is Relative to

Position in Cochlea

Which of the following statements is INCORRECT regarding the visual system? - Visual pigments are stored in membranous discs in rods and cones. - Night blindness results from a deficiency of vitamin A. - Cones are named according to the wavelength of light that they absorb. - Red, green, and blue are the three types of cones. - Rods and cones send receptor potentials directly to the optic nerve.

Rods and cones send receptor potentials directly to the optic nerve.

Which statement regarding photoreceptors is true? A. Rods are more sensitive to light than cones. B. Rods contain the visual pigment called photopsin. C. Rods are found at the greatest density at the fovea, the retina's center of focus. D. Cones are responsible for night vision.

Rods are more sensitive to light than cones.

What is the current state of knowledge regarding magnetite in animals that migrate for long distances? - Magnetite has been conclusively shown to be present in the sensory cells of migrating turtles, but not seabirds. - There is no evidence that magnetite is present in migrating animals, but it is the most likely possibility. - Because magnetite has not been found in the cells of migrating animals, its role in migratory behavior has been dismissed. - Studies have not confirmed the existence of magnetite in the cells of migrating animals. - Evidence supports the presence of magnetite in migrating trout, but not in sea turtles.

Studies have not confirmed the existence of magnetite in the cells of migrating animals.

Receptor cells for more than one taste (salty, sweet, etc) can be located on the same taste bud. How are these tastes "sorted out" as different tastes by the brain? - The receptor potentials generated by the five main tastes are of different magnitude, so the action potentials they cause are of different magnitude, too. - Tastes affect different regions of the tongue, so the brain "understands" that a particular taste comes from a specific region of the tongue. - There are so many taste buds that all taste sensations will be received and integrated by the brain. - The axons carrying signals for different tastes synapse with different neurons in the brain. - The axons carrying signals for different tastes conduct action potentials at different rates, which helps the brain decode the signals.

The axons carrying signals for different tastes synapse with different neurons in the brain.

Which of the following occurs when you focus on the text in a book on your desk? - The ciliary muscle contracts, allowing light to strike the fovea in parallel rays. - The ciliary muscle relaxes, causing the lens to become thinner and flatter. - The ciliary muscle relaxes, causing the lens to become thicker and rounder. - The ciliary muscle contracts, causing the lens to become thinner and flatter. - The ciliary muscle contracts, causing the lens to become thicker and rounder.

The ciliary muscle contracts, causing the lens to become thicker and rounder.

What happens to pressure waves produced by sound as they travel from the environment to the cochlea? - They are amplified about 20-fold by the hammer, anvil, and stirrup in the middle ear. - They are amplified about 10-fold by the hammer, anvil, and stirrup in the outer ear. - They are amplified about 20-fold by collision and reverberation through the round window. - They are reduced about 20-fold as they approach the cochlea, the location of the sensitive hair cells. - They become smaller and smaller as they approach the semicircular canals, the location of the delicate basilar membrane.

They are amplified about 20-fold by the hammer, anvil, and stirrup in the middle ear.

Which feature do ALL sensory receptors have in common? A. They respond to continuous stimuli by becoming more sensitive, to sharpen perception of the environment. B. They are located in the skin. C. They respond to a stimulus by opening or closing ion channels, which changes the membrane potential. D. They respond to a stimulus by temporarily dividing, thereby increasing their sensitivity to the environment. E. They respond to a stimulus by opening or closing ion channels, which generates an action potential.

They respond to a stimulus by opening or closing ion channels, which changes the membrane potential.

True/False: Regular, continuous exposure to 80 decibels (db) can damage hearing

True

True/false: Any region of the tongue with taste buds can detect any of the five main tastes.

True

Honeybees can detect . . .

UV coloration of flowers

Are there other sensory systems?

Yes

Why do you often need to turn your head slightly to see the dimmest stars? A. Turning your head slightly usually activates the visual receptors. B. Your lens will focus the light on the part of the retina with the highest concentration of cones. C. The image will then be focused on the fovea, the part of the retina with the highest acuity. D. Humans are diurnal animals with only limited night vision. E. Your lens will focus the light on the part of the retina with the highest concentration of rods.

Your lens will focus the light on the part of the retina with the highest concentration of rods.

Which of the following examples illustrates sensory adaptation? - You come from a family of expert wine tasters, and you are already showing these abilities too. - You are able to hear lower-pitched sounds than anyone else in your family. - Your friend says, "Look at that amazing star in the sky," but you don't see anything. - You have always preferred chocolate cake to any other flavor. - Your uncle says, "Wow, I smell gas!" when he walks in the front door, but you haven't noticed anything.

Your uncle says, "Wow, I smell gas!" when he walks in the front door, but you haven't noticed anything.

The "oval window"

a connective tissue membrane positioned against the "vestibule"

The possibility that the sense of taste is partly genetically determined is provided by studies that show that __________. - a greater proportion of fraternal than identical twins had similar responses to the taste of cilantro - identical twins raised separately had different responses to the taste of cilantro - fraternal twins raised separately had different responses to the taste of cilantro - members of the same family tended to have similar responses to the taste of cilantro - a greater proportion of identical than fraternal twins had similar responses to the taste of cilantro

a greater proportion of identical than fraternal twins had similar responses to the taste of cilantro

eardrum

a membrane that vibrates in response to sound; it does not respond differently in different regions

The Bulbous corpuscle or (Ruffini corpuscle)

a stretch receptor of skin.

all tastebuds can respond to

all types of taste sensations.

Loudness =

amplitude

The Mosquito (aka Mosquito alarm & SonicScreen)

an electronic device, used to deter loitering by young people, which emits an annoying sound with a very high frequency (17.4 KHz) that can generally be heard only by young people (< 25 years old). It is especially used in France, Switzerland (Europe) & Canada.

Sound waves

are alternating regions of compressed (high pressure) & rarified (low pressure) air moving as waves away from a source. These pressure waves vibrate against the ear drum to get it vibrating.

Birds & fish

are thought to respond to magnetic fields for migratory purposes.

Five basic taste sensations:

bitter, salty, sour, sweet and umami

symptoms of astigmatism

blurred vision

Duck-billed Platypus

can detect electric fields emitted by prey.

The Eustachian tube

can easily become blocked as in ear infections.

Which component of the human eye forms the iris? - pupil - sclera - retina - choroid

choroid

Which of the following is an INCORRECT match between a structure of an eye and the animal species that has that structure? - single-lens eye: all vertebrates - photoreceptor pigments: all animals - compound eye: some vertebrates - ommatidia: some invertebrates - eyecup: some invertebrates

compound eye: some vertebrates

fovea is the region with the highest concentration of ___________, which are of little use in dim light (useful in bright light)

cones

Eustachian Tube

connects with pharynx; allows pressure equalization on each side of the eardrum.

Cochlea

contain the actual hearing organ (Organ of Corti) & associated sensory receptors.

Inner Ear

contains fluid-filled channels involved in balance & hearing.

Middle Ear

converts sound pressure waves into bone vibrations.

Which list correctly orders the structures through which light must pass on its way to the retina of the human eye? A. cornea, aqueous humor, pupil, lens B. pupil, cornea, aqueous humor, lens C. cornea, pupil, aqueous humor, lens D. lens, aqueous humor, pupil, cornea

cornea, aqueous humor, pupil, lens

Which light enters the eye, it passes through several structures before stimulating the optic nerve. Which choice lists these structures in the correct order, front to back? - cornea, pupil, lens, vitreous humor, retina - lens, pupil, vitreous humor, cornea retina - lens, pupil, cornea, vitreous humor, retina - cornea, pupil, retina, vitreous humor, lens - cornea, lens, pupil, aqueous humor, retina

cornea, pupil, lens, vitreous humor, retina

Different regions along the length of the organ of ___________ respond to different frequencies of vibrations.

corti

Loudness is measured in ____________________.

decibels

The senses of taste and smell are linked, and the integration of both of these senses allows us to enjoy the food we eat. As we age, both the sense of smell and the sense of taste begin to diminish. The most likely explanation for this phenomenon is a _____. A. decrease in the surface area of the nasal cavity B. decrease in the number of rods and cones C. decrease in the number of available receptors D. decrease in the number of neurons carrying action potentials to the brain

decrease in the number of available receptors

Fluids of inner ear move slower than the motion of the head, which results in . . .

deflection of gelatinous cupula & stimulation of hair cells

Three Semicircular Canals & Ampullae

detect changes in the angular movement (rotation) of the head; one for each plane of 3D motion.

"Internal" Chemoreceptors

detect chemicals of the internal environment of the body. - CO2 & O2 Sensors in the arteries. - Glucose sensors in the pancreas. - pH & Osmoreceptors of the brain.

Pain Receptors

detect dangerous stimuli . . . - High heat - High pressure

Thermoreceptors

detect heat or cold.

Electromagnetic Receptors

detect various forms of electromagnetic radiation.

Sensory reception is extremely important in . . .

detecting & responding to changes in the environment.

The Eustachian tube

drains mucus (and other fluids) from the middle ear into the nasopharynx

Pheromone receptors

e.g. in the male silkworm moth.

The five senses

each has its own sensory organ.

In stimulus detection, sensory receptor cells convert a stimulus into a(n) - astigmatism. - neurotransmitter. - electric signal. - enzyme.

electric signal.

Humans have all of the following types of sensory receptors EXCEPT _____. - chemoreceptors - mechanoreceptors - electroreceptors - thermoreceptors

electroreceptors

Motion sickness is thought to result from a mismatch between signals that the brain receives from the _______. - musculoskeletal and digestive systems - equilibrium and visual systems - musculoskeletal and visual systems - digestive and equilibrium systems - auditory and visual systems

equilibrium and visual systems

True/false: action potentials and receptor potentials are the same thing

false

presbyopia

farsighted condition of middle age people

Anvil

incus

Outer Ear

focusses sound waves onto the eardrum.

Semi-circular canals

for 3-dimensional balance.

"Somatic Sensory Systems"

general systems that occur in multiple locations throughout the body.

Otoliths

give density & gravitational responsiveness to the ottolithic membrane.

A fish detects vibrations in the water around it by means of its lateral lines, rows of sensory receptors along each side of the body. Based on what you know about sensory receptors, the lateral line receptors are probably which of the following? - hair cells - chemoreceptors - rods - infrared receptors

hair cells

Vibrations in upper canal cause

hair to bend

Aging most often affects people's ability to detect ______ sounds. Why? A. high-frequency: stiffening of the bones in the middle ear B. low-frequency: loss of hair cells in that region of the basilar membrane C. extremely loud: damage to the organ of Corti D. high-frequency: loss of hair cells in that region of the basilar membrane E. low-frequency: stiffening of the bones in the inner ear

high-frequency: loss of hair cells in that region of the basilar membrane

louder sounds generate ________________________ waves

higher-amplitude

A person whose eyeball is shorter than normal suffers from - astigmatism. - myopia. - presbyopia. - hyperopia.

hyperopia

Stretch

in relation to movement of hairs, slippage, loss of grip, & position of body parts (i.e. "Muscle Sense").

The eyes of a planarian provide A. three-dimensional images, but in black and white. B. information about light intensity and direction. C. a higher degree of resolution than human eyes. D. two-dimensional images.

information about light intensity and direction.

Vertigo is a medical term used to describe feeling dizzy, as if everything is spinning. As it can severely compromise an individual's ability to walk or stand still properly, vertigo most likely indicates a problem with the person's - eardrum. - pinna. - auditory canal. - inner ear.

inner ear

The "Chemical Senses"

involved in the detection of chemical substances or molecules in air & food.

The "Physical Senses"

involved in the detection of light & mechanical or physical stimulation.

"External" chemoreceptors

involved in the sense of taste & smell.

Otolithic membrane

is also a gelatinous matrix

Thermoreceptors perform all of the listed functions EXCEPT ______. - conveying information from within the body - keeping an animal's body at an optimal temperature - detecting heat - telling a snake's brain that warm prey is nearby - detecting cold

keeping an animal's body at an optimal temperature

receptors are activated by . . .

light of particular wavelengths, not by motion of the head.

Hammer

malleus

Which receptor transduces when it changes shape and its plasma membrane becomes more permeable to sodium or potassium ions? - thermoreceptor - chemoreceptor - pain receptor - mechanoreceptor

mechanoreceptor

The sensory receptors that respond to stretch, the movement of hairs on your skin, and sound are all ________. - pain receptors - thermoreceptors - chemoreceptors - mechanoreceptors - electromagnetic receptors

mechanoreceptors

A human hears a taxi honking. How long does it take for this signal to reach the person's brain? - nanoseconds - microseconds - milliseconds - seconds

milliseconds

louder sounds cause

more bending of hair

Compared to a dim light, a bright light shined into someone's face causes _______. - less frequent action potentials in the sensory neurons carrying visual information to the CNS - more frequent action potentials in the receptor cells for visual information in the CNS - more frequent action potentials in the sensory neurons carrying visual information to the CNS - larger action potentials in the sensory neurons carrying visual information to the CNS - less frequent, but larger, action potentials in the receptor cells for visual information in the CNS

more frequent action potentials in the sensory neurons carrying visual information to the CNS

Ampulla

name given to the swollen region of each semicircular canal as it attaches to the urtricle.

Glasses with corrective lenses that are thinner in the middle than at the edges (concave) are prescribed for people with _______. - astigmatism - cataracts - nearsightedness - farsightedness - glaucoma

nearsightedness

If stereocilia move towards the kinocilium, . . .

nerve impulse transmission increases

if stereocilia move away from the kinocilium, . . .

nerve impulses decrease

The Eustachian tube

normally closed, but can open to release air pressure.

Which list has structures that are involved only in the sense of hearing? A. oval window, cochlea, aqueous humor B. middle ear bones, semicircular canals, basilar membrane C. eardrum, utricle, organ of Corti D. oval window, basilar membrane, organ of Corti

oval window, basilar membrane, organ of Corti

The only receptors in the epidermis are . . .

pain receptors; the rest are located in the dermis.

Receptor potentials are generated by . . .

photoreceptors (rods and cones) that are embedded in the retina

Frequency =

pitch (musical note)

The somatosensory cortex

processes information from the somatic sensory system.

Generic photoreceptor cell w/stacked membranes containing

receptor pigment, axon region & synapse region (base).

Ibuprofen & Aspirin

reduce pain & inflammation by blocking the synthesis of prostaglandins.

Electromagnetic Receptors

respond to . . . - Electric fields - Magnetic fields - Light (electromagnetic radiation).

Mechanoreceptors

respond to . . . - Mechanical energy - Touch - Pressure - Stretch & muscle sense - Sound - Gravity

Electromagnetic

respond to change in energy that is in the form of electricity, magnetism, or light

Chemoreceptors

respond to chemicals in the external or internal environment. They can sense changes in the amount of oxygen or in the solute concentration in blood

Chemoreceptors

respond to chemicals. - Chemoreceptors in the nose. - Chemoreceptors in the taste buds.

Pain receptors

respond to extremes of temperature and pressure, and to certain chemicals.

Thermoreceptors

respond to heat or cold

Firm Touch

respond to high frequency vibrations.

Light Touch

respond to low frequency vibrations.

mechanoreceptors

respond to mechanical energy by bending or stretching, which puts tension on the cells' plasma membranes and allows ions to move across the membrane, transducing a stimulus into a receptor potential.

Utricle

senses tilting of head relative to gravity, including . . . - Forward vs. backward motion. - Side to side motion. - Acceleration vs. deceleration.

Which listed animal has a well-developed lateral line system, electroreceptors that detect the muscle movements of other animals, and extremely sensitive chemoreceptors? - shark - loggerhead sea turtle - human - snake - fly

shark

all action potentials are of ______________ magnitude

similar

Which of the following choices is an INCORRECT match between a sensory structure and the function it performs? - saccule: its hair cells detect position of head relative to gravity - retina: its rods and cones detect visual stimuli - cupula: its hair cells detect changes in rotation or angular movement - skin: its chemoreceptors produce prostaglandins - basilar membrane: its hair cells detect pressure waves due to sound

skin: its chemoreceptors produce prostaglandins

Fluids of inner ear move ________________________ the motion of the head.

slower than

Stirrup

stapes

All functions of the Inner Ear Organs involve . . .

the bending of hairs on hair cells

Bent hair cells send impulses to

the brain.

Vestibule

the combined chambers of the utricle & saccule.

Loudness (volume) is encoded in the auditory system as _______. Pitch is encoded as _____. - the size of the receptor potential: the degree of movement of the basilar membrane - the location on the eardrum that vibrates in response to a particular sound: the degree of movement of the basilar membrane - the size of action potentials in the auditory nerve: the frequency of axon potentials in the auditory nerve - the location on the basilar membrane that responds to a particular sound: the frequency of action potentials in the auditory nerve - the frequency of action potentials in the auditory nerve: the location on the basilar membrane that responds to a particular sound

the frequency of action potentials in the auditory nerve: the location on the basilar membrane that responds to a particular sound

The brain determines the loudness of a sound from __________. A. the number of action potentials generated in the sensory neurons B. the range of air pressure changes in the middle ear C. the intensity of the action potentials received D. the part of the organ of Corti stimulated by the sound

the number of action potentials generated in the sensory neurons

The saccule and utricle together make

the otolith organs

All action potentials are _________________________

the same size

interpret what the numbers in 20/20 mean

the top number is the distance you would have to stand, and the bottom number is the distance a person with normal visual acuity (always 20, for "20 feet") would have to stand, to see the letters on the eye chart with the same clarity. The numbers do not represent a percentage.

Eardrum

the tympanic membrane.

Which option incorrectly pairs a class of sensory receptor with one of the stimuli it detects? A. chemoreceptors−molecular structure B. thermoreceptors−touch C. electromagnetic receptors−light D. mechanoreceptors−sound

thermoreceptors−touch

Next most sensitive chemoreceptors are probably found in sharks

they can detect blood amounts as low as 1 part per billion ( which is roughly 1 drop per 13,500 gal; or 1 drop per medium sized swimming pool).

Chemoreceptors on the antennae of the male silkworm moth are thought to be the most sensitive in the animal kingdom

they detect a sex pheromone released by the female. Sensitivity of their receptors approach single molecule detection. The name of the pheromone is "bombykol".

What is the function of the Eustachian tube? - to promote yawning or swallowing when fluid builds up - to maintain equal air pressure on either side of the eardrum - to amplify sound within the bony ear canal - to allow drainage of the inner ear if infection occurs - to help conduct the lowest frequencies of sound

to maintain equal air pressure on either side of the eardrum

Incapacitating the muscles of a vertebrate eye would result in an inability _____. A. to expel aqueous humor from the eye, resulting in glaucoma B. of the photoreceptor cells to transduce light energy C. to regulate the amount of light entering the eye and an inability of the photoreceptor cells to transduce light energy D. to regulate the amount of light entering the eye and an inability to focus light

to regulate the amount of light entering the eye and an inability to focus light

Ear drum =

tympanic membrane

Rate of conduction of action potentials _______________. This is a function of the intensity of the stimulus

varies

Most important sense

vision