Biology 172 FINAL EXAM: The Sense Organs

a. conversion of physical or chemical stimulus to a change in membrane potential (receptor potential)
b. strengthen of receptor potential varies with the strength of the stimulus)

a. respond to stimuli in the external environment
b. examples: vision, hearing, smell, taste, & touch

a. respond to stimuli in the internal environment of the body
b. example: muscle spindle (stretch receptor) in muscle

a) Merkel discs (flattened disk-shaped nerve endings near the surface of the skin)
b) Meissner corpuscles (egg-shaped mass of dendrites wrapped in capsule of connective tissue)
c) hair root plexuses (free nerve endings wrapped around hair follicles)

nerve endings called Pacinian corpuscles which are composed of individual dendrites each wrapped in multiple layers of connective tissue – encapsulated nerve ending

a) = stretch receptors in muscles
b) important in reflex arcs

1) consists of a canal below the epidermis with periodically-situated vibration-sensing organs
2) canal connected to the surface via pores that allow the entry of water
3) vibration-sensing organ (neuromast) structure = collection of hair cells with sensory hairs imbedded in gelatinous cupula

bending of hairs
a) receptor potential depolarized or hyperpolarized – depends on the direction of hair bending
b) depolarization _______ rate of action potential generation above background rate
c) hyperpolarization ______ the rate of action potential generation below the background rate

1) typically consists of hair cells surrounding a chamber
2) mineralized _______ in chamber deforms sensory hairs of hair cells

a) involves the saccule and utricle of the inner ear
b) hair cells in a gelatinous matrix (macula) in these structures deformed by the weight of otoliths on the hairs

a) response to rotational acceleration or deceleration
b) involves the three semicircular canals arranged at right angles to each other in three dimensions
c) hairs of the hair cells organized into a cupula within the ampullae of each semicircular canal
d) fluid moving through semicircular canal deforms cupula and induces action potential to be generated by the hair cells

cold receptors respond to temperature range = 
warm receptors respond to temperature range =

a. naked dendrites in the skin  and other tissues of the body (except the brain)
b. may be sensitized by prostaglandins (aspirin inhibits prostaglandin synthesis)

2) compound eyes 
a) observed in arthropods
b) each photoreceptive unit = _________
c) compound eyes useful for detecting motion

Eye:
______ does the coarse focus adjustment, but its focus is fixed by its fixed shape

Eye:
_____ contributes to accommodation because a small pupil size increases the depth of field

a) eyeball too long
b) nearsightedness
c) correct with concave lens

a) eyeball too short
b) farsightedness
c) correct with convex lens

a) abnormal curvature of the cornea or lens
b) lens correction is complex