Test 2: Special Senses Flashcards
Somatic senses
Tactile sensations; touch, pressure, vibration, itch, tickle
Thermal sensations; warm, cold, pain, proprioception
Visceral senses
Conditions within internal organs
Types of receptors
Classified by mode of activation Mechanoreceptors - deformation Thermoreceptors - temperature changes Nociceptors - painful stimuli Photoreceptors - photons of light Chemoreceptors - chemicals in the mouth Osmoreceptors - Osmotic pressure of body flu
Olfactory epithelium, cells
Olfactory receptor
bipolar neuron with cilia (olfactory hairs)
10 -100 million in nose
Supporting cells
Support and nourishment
Innervated by the facial VIII nerve to lacrimal glands and mucous membranes
Basal cells
Stem cells that replace olfactory receptors
Olfactory pathway
Sensory pathways are rapidly adapting, decreasing activity by 50% in first second and completely accommodating in 1-2 minutes
1) Olfactory receptors in the Olfactory epithelium detect chemicals
Olfactory epithelium is located in nasal cavity, cribriform plate of ethmoid bone
Olfactory bulb and olfactory tract lie above cribriform plate
2) Neurons extend into olfactory epithelium, send signal to olfactory nerve (Cranial Nerve I)
3) Olfactory nerve sends information via two pathways
Interpretation
Olfactory nerve -> Thalamus -> Olfactory areas of temporal lobe cortex and frontal lobe below orbits
Emotion
Olfactory nerve -> Hypothalamus -> Amygdala, other parts of limbic system
Olfaction compared to other species: dogs, bears, shark, kiwi, snake
Dogs-
Dogs have two air passages, one for smelling one for breathing
Dogs have a wet nose that captures scent particles
Dog nostrils work independently
Dogs have 40-60 times the olfactory receptor cells, an olfactory cortex 40 times larger
Specialized vomeronasal organ can sense emotion
Bears
Can travel 18 miles from a food source, 100s of miles for a mate
Shark
Great white has largest olfactory bulb
Kiwi
Have nostrils at the end of their beak
Snake
Use their tongues to carry the scent particles to a Jacobson’s organ
Taste sensations
Chemicals that stimulate gustatory receptor cells are called tastents
Once dissolved make contact with plasma membrane of gustatory hairs
Five primary tastes
Sweet, Sour, Bitter, Salty, Umami
10,000 taste buds, decrease with age
Taste buds
Each is composed of ~50 gustatory receptor cells
Supporting cells
Basal cells near base multiply and differentiate, first become supporting cells then gustatory receptor cells
Gustatory hair is a single long microvillus, projects from each receptor cell to surface through taste pore
Papillae
Elevations on the tongue that contain taste buds
Regions of papillae
Vallate papillae
12 large form row at back of tongue, house 100-300 taste buds
Fungiform papillae
mushroom-shaped, over entire surface, 5 taste buds each
Foliate papillae
Small trenches on lateral margins of tongue
Degenerate in early childhood
Filiform papillae
entire surface, contain receptors but no taste buds
Increase friction for food
Gustatory pathway
Three cranial nerves innervate taste buds
Facial VIII - serves taste buds in anterior ⅔ of tongue
Glossopharyngeal IX - taste buds posterior ⅓ of tongue
Vagus X - taste buds in throat and epiglottis
Nerve impulses: cranial nerves -> gustatory nucleus in medulla oblongata -> thalamus -> gustatory cortex of parietal lobe in cerebral corte
Gustation compared to carnivores, other species
Carnivores have fewer taste buds
Catfish have many, some species have 175k compared to our 10,000, chickens have 24
Features of external ear
uses air to collect and channel sound waves
ceruminous glands
modified sweat gland, apocrine, secretion mixes with oil from sebaceous glands to create earwax for protection
Curved 1” long external auditory canal
Leads to tympanic membrane or ear drum
Features of Middle Ear
uses a bony system to amplify sound vibration
Air filled cavity in temporal bone, lined with epithelium
Contains 3 auditory ossicles
Malleus (hammer) attaches to tympanic membrane
Stapes (stirrup)
Incus (anvil)
Transmit sound from external ear to middle ear
Tensor tympani attach and vibrate to dampen loud noises
Eustachian (auditory) tube
connects middle ear with nasopharynx (upper portion of throat)
children get more ear infections because their eustachian tube is not as tilted
Features of Inner ear
generates action potentials to transmit sound and balance information to the brain
begins at oval window
-connective tissue membrane, as the stapes rocks back and forth the oval window and round window oscillate
round window bulges out in response to pressure placed on oval window by oscillates
movement allows fluid to move in cochlea, which in turn allows activation of auditory receptors
consists of outer bony labyrinth and inner membranous labyrinth
Outer bony labyrinth
Contains semicircular canals
Ampulla - receptors for equilibrium
Vestibule - utricle and saccule
Cochlea - hearing receptors
Cochlea
hearing receptors
perilymph and endolymph fill its 3 different internal channels
scala vestibuli
Inner channel
perilymph
scala tympani
Outer channel
perilymph
cochlear duct
In between other channels
endolymph
Hair of inner ear vibration pathway
basilar membrane vibrates from endolymph, vibration moves hair cells of organ of corti against tectorial membrane, leads to bending of stereocilia, stereocilia are mechanosensing organelles, bending of stereocilia ultimately generates nerve impulses to spiral ganglion, cochlear branch of vestibulocochlear nerve VIII
Cells of audition
Hair cells
Supporting cells
basal cells
Auditory pathway
Sound waves enter external auditory canal and strike ear drum
Vibration of ear drum cause ossicles to vibrate
Stapes pushes membrane of oval window
Movement of oval window sends fluid pressure waves in the perilymph of scala vestibuli
Waves transmits to scala tympani and eventually round window
Round window bulges outward in the middle ear
Pressure waves move into endolymph of cochlea duct
Basilar membrane vibrates
-various frequencies causes different regions of basilar membrane to vibrate more intensely than other regions, allows for discernment
Vibration causes the bending of hair cells / stereocilia in the organ of corti of the cochlea
Bending of hair cells causes generation of nerve impulses in first order neurons
Generates nerve impulses along cranial nerve VIII, vestibulocochlear
Nerve impulse travels along cranial nerve VIII, which transmits sound, balance, equilibrium from inner ear to brain
- slight differences in timing arriving from ears to superior olivary nucleus in pons allows us to determine location of sound
- primary auditory cortex in temporal lobe
Types of equilibrium
Static - relative to gravity
Dynamic - relative to movement
Static equilibrium
balance relative to force of gravity
occurs in the vestibule utricle, saccule sensory hairs otolithic membrane composed of calcium carbonite crystals, rests atop hairs
when the membrane is moved according to gravity, the hairs trigger action potentials
Dynamic equilibrium
balance relative to sudden movements
occurs in the semicircular canals
sensory hairs
ampula
crista (small elevation)
each crista contains hair cells and supporting cells covered by cupula, gelatinous material
With movement, cupla bends and nerve impulses are generated
equilibrium nerve
Also uses cranial nerve VIII
Hearing compared to other species
different frequencies, echolocation
Three layers of the inner ear
Sclera (fibrous tunic), Choroid (vascular tunic), Retina (nervous tunic)
Sclera
also includes cornea, transparent epithelium that protects front of eye
Sclera is the white of the eye
gives the eye shape, protects inner anatomical parts
Cornea is transparent, where light enters eye
Choroid
includes ciliary body, iris
melanin prevents light from scattering inside the eye
Anterior portion has two structures
Ciliary body
secretes aqueous humor
muscle changes shape of lens to focus near or far
Iris
Colored portion of eyeball, controls size of pupil
Circular muscles in the center cause pupil to constrict
Radial muscles of iris cause pupils to dilate
Retina
inner nervous layer
Sensory layer, converts light into nerve impulses
photoreceptors
lines the posterior ⅔ of the eye
consists of a layer of melanin pigmented epithelium that allows light to be absorbed rather than scattered
Rods and Cones
Rods
Grey tones, more sensitive to light, excited in dim light, peripheral vision, low resolution images
Lose as you age
120million
Cones
Central areas, need bright light to be excited
3 types for red, green, blue
Center of retina
Macula lutae in the fovea centralis
tiny pit in back of retina, exact center
contains only cones, sharpest vision
blindspot where optic nerve leaves
Chambers of the eye
Anterior - between cornea and iris
Posterior - between iris and lens
Vitreous - between lens and retina
Vitreous chamber
posterior segment large chamber behind lens Filled with clear gel: vitreous humor transmits light supports back of lens holds layers of retina in place
Anterior chamber
Smaller chamber between lens and cornea
Filled with aqueous humor
Nourishes lens and cornea, replaced every 90 minutes
Focuses incoming light
Held in place by ligaments attached to ciliary body
Visual pathway
After focused by cornea, then lens:
Light comes in, pigmented layers of retina focus light, rods and cones react to the color or light and synapse with the bipolar cells, horizontal cells
Horizontal cells can transmit inhibitory signals to bipolar cells lateral to rods and cones
Bipolar cells can transmit excitatory signals to ganglion cells
Ganglion cells become depolarized and initiate nerve responses
Nerve responses go up optic nerve (cranial nerve II)
Some axons cross at optic chiasm
Most optic tracts terminate at thalamus, synapse with neurons that project primary visual cortex in occipital lobes
Lens
avascular, posterior to pupil and iris, transparent
attaches to ciliary body
consists of capsule with crystallin proteins arranged in layers
Disorders of refraction
Myopia - nearsightedness, only near objects can be seen
Light rays are focused in front of retina, corrected with negative concave lens
Hyperopia - farsightedness
Light rays are focused behind retina, corrected with positive convex lens
Astigmatism - multiple focal points
Accessory eye structures
Extrinsic eye muscle move eye
Eyebrows, eyelids, eyelashes protect eyes
Lacrimal apparatus produces tears
washes eyes, antibodies and antibacterial agents
Drains tears into nasal passages
Tears
lacrimal glands are size of almond, produce lacrimal fluid
Oil glands
protect against bacteria
Conjunctiva
Mucous membrane lubricates eyeball
Color blindness
absence or deficiency of one of the three types of cones
red green most common
Night blindness
caused by prolonged vitamin a deficiency
rods not working as well
also age
retinal detachment
if you lose the vitreous humor, the retina can detach
medical emergency
Macular degeneration
loss of vision in center of visual field, can’t recognize faces
happens to older people
Cataracts
Opaque defect in cornea or lens
Caused by injury, medications, disease
principle cause of blindness
Conjunctivitis
Inflammation of the conjunctival membrane
Glaucoma
Blockage to aqueous humor flow increases pressure inside eye
can lead to degeneration of eye function
Hagfish eyesight
Hagfish don’t have cornea, lens, no melanin, wired to brain like pineal gland
Only photoreceptors, interneurons, ganglion cells
Cornea is continuos with skin
Shark eyesight
similar to human corneas, cat eyes
layer of reflective crystals acts as a mirror to reflect incoming light
“second look”, but counterproductive in bright conditions - like cats
pupils dilate, are very dynamic
double cornea protects things
Bird eyesight
some have two foveas
some diving birds have eyes that adapt very quickly to water with muscular iris
Owls only can see the color blue, can’t move their eyes
Pigeons have good color vision
Ostriches have eyes bigger than their brains
Eagles have very sharp vision
Meissners corpuscles and Pacinian corpuscles
Meissner’s corpuscles are rapidly-adapting, encapsulated neurons that responds to low-frequency vibrations and fine touch; they are located in the glabrous skin on fingertips and eyelids.
Pacinian corpuscles are rapidly-adapting, deep receptors that respond to deep pressure and high-frequency vibration.
