Ch 43 Sensory Organs Flashcards
– neuron endings or specialized receptor cells in close contact with neurons
Sensory receptors
Part of the nervous system
– sensory receptors and accessory cells
Sense organs
• 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
Thermoreceptors
• 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
Electroreceptors
• 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
Nociceptors
• Transduce mechanical energy
– allow animals to feel, hear, maintain balance
– activated by shape change
– (push or pull)
Mechanoreceptors
Mechanoreceptors respond to
– touch – pressure – gravity – stretch – movement
• Several kinds of touch receptors in skin
• Respond to
– displacement of hairs
– displacement of receptor cells themselves
Tactile (touch) Receptors
5 types of Tactile (touch) Receptors
- Hair follicle receptors
- Merkel disks
- Ruffini corpuscles
- Meissner corpuscles
- Pacinian corpuscles
• 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
Proprioceptors
Proprioceptors respond to
– tension (position)
– movement
• 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
Vertebrate Hair Cells
Inform animal of moving objects or objects in its path
Lateral line organs
• Consists of a labyrinth
– of fluid-filled chambers and canals
– helps maintain equilibrium (i.e. balance)
The Vertebrate Inner Ear
– in upper part of labyrinth
– contains saccule, utricle, semicircular canals
Vestibular apparatus
• 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
Otoliths
• 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
Semicircular Canals
• 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
The Path of Sound
- 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.
Chemoreceptors
– olfactory epithelium with specialized olfactory cells
– samples small quantities of molecules away from source
Smell (olfaction)
– specialized epithelial cells in taste buds of vertebrates
– samples large quantities of molecules directly from source
Taste (gustation)
Use pigments to transduce light energy.
Photoreceptors
Molecules that absorb light.
Pigments
Major photoreceptor pigment in animals
Rhodopsin
