Ch 43 Sensory Organs

Question 1

– neuron endings or specialized receptor cells in close contact with neurons

Answer 1

Sensory receptors

Question 2

Part of the nervous system

– sensory receptors and accessory cells

Answer 2

Sense organs

Question 3

• Generally specialized nerve endings
– not specialized receptor cells 
• In some animals
– used to locate endothermic prey
– used to find an endothermic host 
• In endothermic animals
– provide cues about body temperature

Answer 3

Thermoreceptors

Question 4

• Used by fishes
– to detect prey muscle movements
– communicate
• ability to generate electric currents is further specialized in electric eels and rays.
• Many animals detect Earth’s magnetic field
– some animals orient by magnetic fields
– migratory animals navigate by magnetic fields

Answer 4

Electroreceptors

Question 5

• Pain receptors
– free nerve endings of certain sensory neurons 
– in almost every tissue
• Respond to extremes of many stimuli
– strong tactile stimuli
– temperature extremes
– certain chemicals

Answer 5

Nociceptors

Question 6

• Transduce mechanical energy
– allow animals to feel, hear, maintain balance
– activated by shape change
– (push or pull)

Answer 6

Mechanoreceptors

Question 7

Mechanoreceptors respond to

Answer 7

– touch
– pressure
– gravity
– stretch
– movement

Question 8

• Several kinds of touch receptors in skin
• Respond to
– displacement of hairs
– displacement of receptor cells themselves

Answer 8

Tactile (touch) Receptors

Question 9

5 types of Tactile (touch) Receptors

Answer 9

• Hair follicle receptors
• Merkel disks
• Ruffini corpuscles
• Meissner corpuscles
• Pacinian corpuscles

Question 10

• Allow animal to perceive body orientation and positions of its parts
– muscle spindles
– Golgi tendon organs
– joint receptors
• movement in ligaments
• Probably the most numerous and active receptors

Answer 10

Proprioceptors

Question 11

Proprioceptors respond to

Answer 11

– tension (position)

– movement

Question 12

• Each has two types of cilia for detection of movement
– often covered with a cupula
• Found in lateral line of fishes
– and inner ears of vertebrates

Answer 12

Vertebrate Hair Cells

Question 13

Inform animal of moving objects or objects in its path

Answer 13

Lateral line organs

Question 14

• Consists of a labyrinth
– of fluid-filled chambers and canals
– helps maintain equilibrium (i.e. balance)

Answer 14

The Vertebrate Inner Ear

Question 15

– in upper part of labyrinth

– contains saccule, utricle, semicircular canals

Answer 15

Vestibular apparatus

Question 16

• In saccule and utricle
• Change position
– when head is tilted
– when body is accelerating
• Stimulate hair cells that signal to brain
– enable animal to perceive direction of gravity/acceleration

Answer 16

Otoliths

Question 17

• Oriented in 3 planes
• Inform brain about turning movements
• Clumps of hair cells located within each of the
bulblike enlargements (ampullae)
• Hair cells are stimulated by movements of fluid that fills each canal

Answer 17

Semicircular Canals

Question 18

• Passes through external auditory canal
• Causes tympanic membrane (eardrum) to vibrate
• Ear bones transmit and amplify vibrations through middle ear.
• Vibrations pass into fluid within
canals/ducts of the cochlea
• Pressure waves press on membranes separating three ducts of the cochlea
• Movements stimulate hair cells of organ of Corti by rubbing them against overlying tectorial membrane

Answer 18

The Path of Sound

Question 19

• Smell (olfaction)
• Taste (gustation)
• Taste & smell are not distinct in many aquatic organisms.
• Both depend upon a dissolved molecule fitting into a receptor on a cell.

Answer 19

Chemoreceptors

Question 20

– olfactory epithelium with specialized olfactory cells

– samples small quantities of molecules away from source

Answer 20

Smell (olfaction)

Question 21

– specialized epithelial cells in taste buds of vertebrates

– samples large quantities of molecules directly from source

Answer 21

Taste (gustation)

Question 22

Use pigments to transduce light energy.

Answer 22

Photoreceptors

Question 23

Molecules that absorb light.

Answer 23

Pigments

Question 24

Major photoreceptor pigment in animals

Answer 24

Rhodopsin

Question 25

– Detect light but do not form images

– in cnidarians and flatworms

Answer 25

Eyespots

Question 26

• Light
– enters through the cornea
– is focused by the lens
– produces an image on the retina
– amount of light entering is regulated by the iris

Answer 26

The Human Eye

Question 27

• At the back of the retina
– epithelium provides retinal (for rhodopsin) • Rods
• Cones
• Bipolar cells
– send signals to ganglion cells
• Other cells in retina function inintegration

Answer 27

Receptors in Retina

Question 28

Most abundant
– function in dim light
– form images in black and white

Answer 28

Rods

Question 29

Concentrated near center
– function in bright light
– permit color vision

Answer 29

Cones