What are the special senses in humans?

Vision

Taste

Smell

Hearing

Equilibrium

How do special senses differ from general senses?

General:Scattered throughout the body, and relatively simple in structure

Special: are localized by their respective sensory organ.

What is the sequence of structures and fluids that light rays must pass through to reach the retina?

conjuctiva, cornea, anterior segment, margin of pupil, lens, ciliary body, ciliary process, ciliary zonule, posterior segment, retina.

Which of the eye structures does most of the refraction of light rays?

cornea

What is astigmatism?

a condition in which unequal curvatures in different parts of the cornea or lens of the eye lead to blurred vision.

How does the ANS control pupil diameter?

The parasympathetic controls constriction and the sympathetic controls dilation

How does the ANS control changes in lens shape during accommodation (how does the ciliary muscle change lens shape when viewing a near versus distant object)?

For near objects, the ciliary muscle relaxes and the lens flattens.

For distant objects, the ciliary muscle contracts and the lens bulges.

What are the layers of cells that constitute the retina?

horizontal, bipolar, amacrine, and ganglion cells

In which direction does light pass through these cell layers in the retina?

horizontal, bipolar, amacrine, and ganglion??

Which neurons of the retina form the optic nerve?

ganglion cells

How do rods and cones differ anatomically?

Rods contain rhodopsin; they are for black and white.

Cones contain retinal; they are for colors.

What is the outer segment?

contains visual pigment molecules

What is photodissociation?

bleaching of visual pigments

What is rhodopsin?

visual pigment made of retinal and opsin

What is retinal?

protein derived from vitamin A

What is opsin?

protein that helps make up rhodopsin and is activated by light.

Why is vitamin A important for vision?

retinal comes from vitamin A

What vision problem occurs as a result of vitamin A deficiency?

night blindness

What is responsible for dark adaptation?

rhodopsin

How are action potentials (nerve impulses) generated in the optic nerve when light strikes the photoreceptors?

phototransduction closes the Na channels; no release of inhibitory neurotransmitter

What are the types of cones?

red, green, blue

How do the different types of cones differ?

Each type contains retinal attached to different types of opsin

red(560 nm), green(530 nm), blue(420 nm)

What anatomical features of the retina are responsible for producing high visual sensitivity?

rods

What anatomical features of the retina are responsible for producing high visual acuity?

cones

What are the relative distribution of rods and cones in the retina?

way more rods than cones

What is the extent of neuronal convergence from these photoreceptors to the ganglion cells?

Extensive neuronal convergence from rods; no neuronal convergence from cones.

What is myopia?

nearsightedness

What is hyperopia?

farsightedness

What produces conditions of hyperopia?

the eye is too short

How do corrective lenses compensate for myopia?

concave lenses

How do corrective lenses compensate for hyperopia?

convex lenses

What is glaucoma?

inadequate drainage of aqueous humor

What produces glaucoma?

high intraocular pressure damages optic nerve

What is cataract?

inadequate delivery of nutrients to deeper lens fibers

What produces cataract?

clumping of crystallin proteins

What types of receptors are responsible for the sense of taste?

taste buds aka taste cells or taste hairs

What types of receptors are responsible for the sense of olfaction?

olfactory cells

How are taste receptors stimulated?

dissolved molecules bind to protein receptors

How are olfaction receptors stimulated?

volatile molecules bind to protein receptors

How many different odors can humans distinguish?

more than 1 trillion

How many different tastes can humans distinguish?

five

What are the tastes that humans can distinguish?

salty, sweet, sour, bitter, savory

What structures are located in the outer ear region?

auditory canal, tympanic membrane

What structures are located in the middle ear region?

tympanic membrane, auditory tube, oval window

What structures are located in the inner ear region?

oval window, cochlea, auditory tube

What is the sequence of events that leads to generation of action potentials in cochlear nerve?

Sound waves vibrate tympanic membrane, the vibration moves ossicles, stapes move oval window, pressure waves created in fluid inside cochlea, pressure waves in cochlear fluid move the basilar membrane, hair cells in spiral organ are bent, bending of hair cells opens K+ channels of sterocilia, K+ inflow --> depolarization --> Ca influx --> release of glutamate --> APs in cochlear nerve fibers

What are the sensory receptor cells for hearing?

cochlear hair cells

Where are the sensory receptor cells for hearing located?

cochlea of the inner ear

How does transduction occur in hearing receptors?

outer modify responsiveness of inner

What is the reflex mechanism for preventing damage to hearing receptor cells when you are exposed to very loud sounds?

stapedius and tensor tympani limit movements from loud sounds

How does the ear detect differences in pitch of sound?

high pitch stimulates basilar membrane close to the oval window

low pitch stimulates basilar membrane farther from oval window

What types of problems can lead to conduction deafness?

auditory canal blockage, inflamed middle ear, abnormal bone growth near middle ear, damage to tympanic membrane

What types of problems can lead to sensorineural deafness?

loss of cochlear hair cells

Which structures of the inner ear are involved in sensory perception for balance?

hair cells in the inner ear

What are the sensory receptor cells for balance?

hair cells, visual receptors, somatic receptors(proprioceptors)

Where are the sensory receptor cells for balance located?

ear, eyes, neck, trunk, limbs

What are the stimuli for the balance (vestibular) receptors in these structures?

gravity and inertia

What are the motor responses for vestibular information?

reflexive eye movements, motion sickness