Chapter 17 - Sense Organs Flashcards
Receptors
structures that detect stimuli
Class of Receptors by Modality (type of stimuli)
- Thermoreceptors
- Photoreceptors
- Chemoreceptors
- Nociceptors
- Mechanoreceptors
Classes of Receptors by Distribution
- General senses - widely distributed
2. Special senses - involve cranial nerves, complex
Class of Receptors by Stimulus Origin
- Exteroceptros
- Interoceptors
- Proprioceptors
General senses are detected by different receptors that included both ______________ and ______________ nerve endings.
unencapsulated, encapsulated
Unencapsulated Nerve Endings
dendrites lack connective wrapping
- Free nerve endings - warm receptors, cold receptors, nociceptors
- Tactile (Merkel) discs - light touch, pressure
- Hair receptors - movement of hairs
Encapsulated Nerve Endings
dendrites wrapped by glia or connective tissue
- Tactile (Meissner) corpuscles
- End bulbs (Krause)
- Bulbous (Ruffini) corpuscles
- Lamellar (Pacinian) corpuscles
- Muscle spindles
- Tendon organs
Tactile (Meissner) Corpuscles
- oval mass in dermal papillae
- sense light touch, texture perception
End bulbs (Krause)
similar to tactile corpuscles but located in mucous membranes
Bulbous (Ruffini) Corpuscles
- flat
- sense pressure, skin stretch, and joint movement
Lamellar (Pacinian) Corpuscles
- onionlike
- sense deep pressure, stretch, tickle, and vibration
Muscle Spindles
- fusiform
- sense skeletal muscle stretch
Tendon Organs
- leaflike
- sense tendon stretch caused by muscle activity
Receptive Field
area supplied by a single neuron
Referred Pain
pain from the viscera mistakenly thought to come from more superficial areas (pain fibers from deep tissues merge with those of the skin)
Gating of Pain
pain signals from periphery never reach brain (e.g. heart attack pain in arm - stress and tension, mental factors, lack of activity)
Taste Bud Locations
- Tongue (most)
- Soft palate
- Pharynx
- Epiglottis
- Cheeks
Types of Lingual Papillae
- Filiform - numerous, tiny spikes, no buds
- Folate - ridges on tongue sides, bud in children
- Fungiform - mushroom shaped bumps, have buds
- Vallate - large bumps in a row at back of tongue, have buds
Taste Cells
- banana-shaped
- live 7-10 days
- taste hairs (receptor for taste module)
- synapse with sensory nerve
Cranial Nerves for Taste
- CN VII (anterior tongue)
- CN IX (posterior tongue)
- CN X (palate, pharynx, epiglottis)
Olfactory Mucosa
- roof of nasal cavity
- 10-20 million olfactory neurons
Olfactory Neurons
- cilia w/ binding site for odor molecules
- bipolar neuron
- neuron’s axons form CN I
Olfactory Bulbs
swollen tips of olfactory tracts at base of frontal lobes
Muscles of Ear
- tensor tympani
- stapedius
contract to tighten ossicles as a reaction to loud, potentially damaging sounds
Endolymph
fluid in membranous labyrinth
high K+
Perilymph
fluid between membranous labyrinth and bone
high Na+, low K+
Cochlear Duct
- organ of hearing
- contains spiral organ (has four rows of hair cells)
- hair cells synapse with sensory neurons that form the cochlear division of CN VIII
- contains endolymph (high K+)
Scala Vestibuli
- superior chamber of cochlea
- begins near oval window
- contains perilymph
Scala Tympani
- inferior chamber of cochlea
- ends at round window
- contains perilymph
Auditory Function
- air vibrates tympanic membrane
- ossicles push against oval window
- vibrate fluid in inner ear
- bending of stereocilia opens ion channels and starts electrical signals
Hair cells near the base of the cochlea respond to _____ pitches.
Hair cells near the apex of the cochlea respond to _____ pitches.
high, low
Auditory Projection Pathway
- hair cells excite cochlear nerve fibers
- cochlear nerve projects to cochlear nucleus
- to superior olivary nucleus
- to inferior colliculus
- to thalamus
- to primary auditory cortex of temporal lobe
Vestibular Apparatus
- equilibrium - coordination, balance, orientation
- three semicircular canals detect angular acceleration
- utricle and saccule each have macula to detect static equilibrium and linear acceleration
Maculae
- pack of hair cells in utricle and saccule
- detects orientation of head in relation to gravity (static equilibrium and linear acceleration)
- utricle is horizontal perception
- saccule is vertical perception
- hair cells have kinocilium embedded in the otolithic membrane (gelatinous) with otoliths (CaCO4 crystals)
Semicircular Canals
- three: anterior, posterior, and lateral
- each has an ampulla w/ a crista ampullaris
- hair cells project into gelatinous cupula
- detect angular acceleration
Choroid
pigmented layer behind retina
Ciliary Body
ring of smooth muscle around lens
Iris
pigmented diaphragm controlling pupil diameter
- pupillary constrictor - concentric smooth muscles cells
- pupillary dilator - spoke-like myoepithelial cells
Optic Disc
- where optic nerve exits
- blind spot with no receptors
Macula lutea
central patch for detailed vision
* pit within macula
Image Formation
- vision occurs when light is refracted as they pass through the cornea and lens
- for distant vision, lens is flat
- for near vision, lens thickens
- visual defects often involve image formation
- refractive error (uneven curvature, not smooth, etc.)
Hyperopia
- farsightedness
- corrected with convex lens
Myopia
- nearsightedness
- corrected with concave lens
Retina
light sensitive tissue that converts lights into electrical impulses that are sent to the brain through the optic nerve
Photoreceptor Cells
Rods & Cones
Rods
- photoreceptor cells
- night vision, monochromatic
- Rhodopsin (pigment)
- maximizes light absorption
Cones
- photoreceptor cells
- day vision, trichromatic
- color vision
- Photopsins (pigments, respond to different wavelengths)
Ganglion Cells of Retina
- receive input from bipolar cells
- axons from optic nerve
