Specails senses Flashcards
Olfactory epithelium
Highly modified nerve cells and detect dissolved chemicals.
What 4 structures are withing the lamina propria?
- Areolar tissue
- blood vessels
- nerves
- olfactory glands
What is the first step of olfactory reception?
Begins with binding of odorant to G protein-coupled receptor.
What happens after the G protein-coupled with a receptor?
Generator potential (depolarization)
What happens after a generator potential happens?
Afferent fibers leave olfactory epithelium and collect in 20 or more bundles.
After 20 or more bundles are collected what happens
Penetrates cribiform plate of ethmoid bone and reach olfactory bulbs of cerebrum where first synapse.
What happens after there is a cerebrum where first synapse occurs?
Axons leaving olfactory bulb travel along olfactory tract to olfactory cortex, hypothalmus and limbic system.
Olfactory information is the only type of sensory information to reach cerebral cortex _______.
Directly
What are the accessory structures of the eye (3)?
- Eyelids
- Conjuntiva
- Lacrimal apparatus
Palpebral fissure-gap that separates structures?
Free margins of upper and lower eyelids.
Eyelids are collected where?
Medial angle and lateral angle
Lacrimal caruncle
Mass of soft tissue at medial angle of eye and contains glands producing thick secretions.
Palpebral conjuctiva
Covers inner surface of eyelids.
Bulbar conjunctiva
Covers anterior surface of eye and extends to edges of cornea.
Fornix
Pocket where palpebral conjuntiva joins bulbar and receives 10-12 ducts from lacirmal gland.
Tears pass through what areas ( place them in order)?
- Lacrimal puncta
- Lacrimal canaliculi
- Lacrimal sac
- Nasolacrimal duct
- Nasal cavity
Orbital fat
Cushions and insulates eye
Corneaoscleral junction (corneal limbus)
Border between cornea and sclera.
Where does the ciliary body attach?
Attaches to iris
Ciliary body extends posteriorly to level of what structure?
Ora serrata
Ciliary body contains what structures
- Ciliary muscle
2. ciliary processes
Ciliary zonule attaches the lens to what structure?
ciliary processes
Choroid
Vascular layer that separates fibrous and inner layers posterior to ora serrata and capillaries deliver oxygen and nutrients to retina.
Pupillary muscles
Change diameter of pupil (central opening of eye.
What are the functions of the vascular layer?
- Provides route for blood vessels and lymphatics that supply tissues of eye.
- Regulates amount of light entering eye.
- Secretes and reabsorbs aqueous humor that circulates within chambers of the eye.
- Controls shape of lens, which is essential to focusing.
Pigmented layer
Absorbs light that passes through neural layer.
Neural layer
Contains supporting cells and neurons, outermost part contains photoreceptors.
Bipolar cells
Synapse with rods and cones
Ganglion cells
Synapse with bipolar cells.
Horizontal and amacrine cells
Facilitate or inhibit communication between photoreceptors and ganglion cells and alter sensitivity of retina.
What part of the eye has no photoreceptors?
Blind spot
Aqueous humor
Diffuses through posterior cavity, enters scleral venous sinus at corneoscleral junction and reenters circulation at veins in the scerla.
Lens fibers
Enucleate cells in interior of lens and filled with crystallins, which provide clarity and focusing power.
Focal point
Specific point of intersection of light rays on retina.
Focal distance
Distance between center of lens and focal point.
How is the focal distance determined?
Distance of object from lens and shape of lens.
Accommodation
Automatic adjustment of eye to provide clear vision.
Astigmatism
Condition where light passing through cornea and lens is not refracted properly.
What is visual acuity for someone who is legally blind?
20/200
Scotoma
Abnormal, permanent blind spot, may result from compression of optic nerve, damage to photoreceptors, or central damage.
What are the 4 steps to photoreception?
- Absorption of a photon changes retinal from 11-cis to 11-trans form and activates opsin.
- Opsin activates transducin (G protien) which activates phosphodiesterase (PDE)
- PDE reduces levels of cyclic GMP chemically gated sodium ion channels close.
- Dark current is reduced, rate of neurotransmitter release declines.
Dark adapted state
Visual pigments are fully receptive to stimulation.
Light adapted state
Rates of bleaching and reassembly of visual pigments are balanced.
Retinitis pigmentosa
Inherited disease and characterized by progressive retinal degeneration.
M cells
Monitor rods, relatively large, and provide information about general form of an object motion, shadows in dim lighting.
P cells
Monitor cones in foveas, ratio of cones to ganglion cells is 1:1, smaller and more numerous than M cells and provide information about edges, fine detail and color.
On center neurons
Excited by light arriving in center of receptive field and inhibited when light strikes edges.
Off center neurons
Inhibited by light in central zone and stimulated by light at edges.
Optic radiation
Bundle of projections fibers linking lateral geniculates with visual cortex.
What are the smallest synovial joints in the body?
Auditory ossicles
Bony labyrinth can be subdivided into what 3 parts?
- Vestibule
- Semicircular canals
- Cochlea
What are the semicirular canals stimulated by?
Rotation of head
Round window
Thin, membranous partition and separates perilymph from air spaces of middle ear.
Oval window
Connected to base of stapes by collagen fibers.
What do ampullary crest contain?
Hair cells
Each hair cell in vestibular complex has how many sterecilia?
80-100
Macula
Oval structures where hair cells cluster.
Macula of utricle
senses horizontal movement
Macula of saccule
Senses vertical movement
Otoliths
(ear stones) Densely packed calcium carbonate crystals on surface of gelatinous mass.
4 functions of the vestibular nuclei
- Intergrate sensory information about balance and equilibrium from bothsides of head
- Relay information from vestibular complex to cerebellum.
- Relay information from vestibular complex to cerebral cortex.
- Send commands to motor nuclei in brainstem and spinal cord.
Nystagmus
Trouble controlling eye movements when body is stationary and caused by damage to brainstem or internal ear.
Pressure wave
Consists of a region where air molecules are crowded together, and adjacent zone where they are farther apart.
Wavelength
Distance between two adjacent wave crests.
Frequency
Number of waves that pass a fixed reference point in a given time.
Pitch
Our sensory response to frequency
Amplitude
Height of a sound wave
Intensity
Amount of energy in sound wave and determines how loud it seem is reported in decibels.
