Lecture 10 - Special Senses #1 Flashcards
Function of sensory receptors
- > respond to stimulus
- > initiated sensory input to CNS
Explain stimuli
- > changes in sensory information which are detected by receptors
- > react to pleasure/ danger
Explain sensations
- > conscious awareness of a stimulus (sensory information; aware of only fraction of stimuli)
- > only stimulus that reaches cerebral cortex
Receptors as transducers
- > change one form of energy into different form
- > original energy specific to type of receptors i.e. light energy in eye, sound energy in ear
- > energy is transduced into electrical energy which is then conducted along afferent sensory neuron
Receptor clasification
- General sense receptors
- > somatic sensory receptors (skeletal muscles)
- > Visceral sensory receptors (smooth muscle) - Special senses receptors
Functions of somatic sensory receptors
housed within skin, joints, muscles, tendons which detect pressure, vibration, pain, stretch
functions of visceral sensory receptors
located in the walls of viscera which respond to temperature, chemicals, stretch and pain
What are the five special senses
- Gustation (taste)
- Olfaction (smell)
- Vision (sight)
- Hearing (auditory)
- Equilibrium (balance and acceleration)
Explain special senses receptors
specialized, complex sense organ receptors located within the head in charge of the 5 special senses
Stimulus receptor classifications
- Exteroceptors
- Interoceptors
- Proprioceptors
- Chemoreceptors
- Thermoreceptors
- Photoreceptors
- Mechanoreceptors
- Baroreceptors
- Nociceptors
Exteroceptors
detect stimuli from external environment
Interoceptors
detect stimuli from internal organs
Proprioceptors
detect body and limb movement in space
Chemoreceptors
detect chemicals in environment (taste, smell use chemoreceptors)
Thermoreceptors
detect temp change in environment & body
Photoreceptors
in the eye detects light intensity, colour, movement
Mechanoreceptors
detect touch, vibration, pressure, stretch
Baroreceptors
detect pressure changes (stretch) in organs and vessels
Nociceptors
detect painful stimuli (somatic/skeletal or visceral/smooth muscles)
Explain referred pain
- > when pain is not perceived as originating from specific organ but is perceived as originating form dermatomes of skin
- > stimulus localized incorrectly
Dermatomes
an area of skin supplied by a single spinal nerve; area of skins pain is connected *dermatomes map*
list some common sites of referred pain
Cardiac problems - > may feel pain along medial side of left arm
Kidney and Ureter pain - > may feel pain over inferior abdominal wall and groin and loin
Olfactory epithelium
covers superior naval cavity and cribriform plate
What are the three types of olfactory epithelium
- Olfactory receptors (bipolar neurons with cilia or olfactory neurons)
- Supporting cells (columnar epithelium)
- Basal cells (= stem cells)
Explain Bowman’s gland
also know as the olfactory gland, this gland helps detach odourant molecules from bipolar neurons (coffee grounds in a perfume shop)
what is a vallante papilla
little groves on the tongue with sides lined with tastebuds and a top layer of epithelium which overs the whole structure
how do taste buds detect taste
tastes bud has a taste pore in the epithelial tissue which has gustatory hairs that project upward through the taste pore. This allows taste receptors (gustratory cells) to transmit information to the brain via sensory nerves; also contains support cells
List all five basic taste sensations
- Sweet - > produced by organic compounds (sugar, artificial sweeteners)
- Salt - > produced by metal ios (Na+ or K+)
- Sour - > associated with acids (vinegar)
- Bitter - > produced by alkaloids ie. unsweetened chocolate (alkaloids=things that would have poisoned our ancient ancestors i.e. poison berries)
- Umami - > taste related to amino acids to produce meaty flavour
Physiology of Taste
- > substances must be desolved in water (saliva) to be able to taste
- > thresholds for taste varies among 5 primary tastes (most sensitive bitter/poison, least sensitive salt and sugar)
- > complete adaptation in 1-5 minutes (taste neurons get fatigued/ overstimulated and stop sending the same taste signal)
List all accessory structure of the eye and their function(s)
Eyelid - > protect and lubricate the eye
Eylashes/brows - > help protect eye from forign objects, sweat and sunlight
Lacrimal glands - > secrete lacrimal fluid (tears)
Explain the flow of tears
- > fluid is secreted from the lacrimal glands
- > fluid flows across conjunctiva and through the lacrimal punctum and through the superior/ inferior lacrimal canals
- > it then passes through the lacrimal sac - > nasolacrimal duct - > nasal cavity
sebaceous glands
found at the base of eyelashes, also know as sty
- > clogged sty form a pimple-like structure on eyelid
conjunctiva
a thin, clear, moist membrane that lines the inside of the eyelids ad the outter surface of the eye
- > inflamation of the conjunctiva is called conjunctivitis (pink eye)
List the three major structures that make up the internal eye and what are their substructures
- Fibrous Tunic (tunic=layer)
- > Sclera
- > cornea - Vascular Tunic
- > Iris
- > Ciliary body
- > choroid - Retina
- > Pigmented layer
- > neural layer
Properties of the cornea
- > avascular, trasparent
- > parallel collagen fibres with cristalline proteins
- > helps focus light (refraction)
- > common successful transplants as there are no blood vessels or antibodies to cause rejection
- > noursihed by tears and aqueous humor
Properties of Sclera
- > “white” of the eye
- > dense irregular (diff ways) connective tissue layer (collagen and fibroblasts)
- > provides shape and support to the eye itself
- > separated from cornea by scleral venous sinus
- > posterior peirced by optic nerve
Properties of the Choroid
- > made up of pigmented epithelial cells and blood vessesl
- > provides nutrients to retina
- > black pigment abosorbs scatted light
Ciliary Body
Made up of Ciliary process
- > secretes aqueous humor fluid
- > attached to lens by suspensory ligaments
And ciliary muscle
- > smooth muscle that alters shape of lense (tenses releases lens)
Iris
- > coloured portion of eye
- > hole in the centre is pupil
- > regulated the amount of light that enters the eye
Muscles of the iris and how are they innervated
Constrictor pupillae (circular) - > are innervated by parasympathelic fibres (sleepy kitty; rest and digest)
Dilator pupillae (radial) - > are innervated by sympathetic fibres (fast kitty: cat gets excitde/scared pupil enlarges so that the cat can see the threat)
Properties of the lens
- > Avascular
- > focuses light on retina
- > held in place by suspensory ligaments
- > made up of critalinne proteins arranged in layers
What are cataracts
Clouding of the lense caused by foreign objects embedding in christalline proteins
- > main causes are linked to both genetics and habit factors
Lens shape in far vision vs near vision
distant vision - > lense flattens, ciliary muscles relaxed
near vision - > lense is more rounded/thickens, ciliary muscles contract (moving closer to lens) and suspensary ligamens relax
Properties of the Retina
- > covers 3/4 of the posterior eyeball
- > houses the optic disc, macula lutea and peripheral retina
optic disc
- > optic nerve exiting back of eyeball = optic disc
- > has no photoreceptors (light bouces off and not absorbed) and it the “blind spot”
What is the macula lutea
rounded, yellowish region lateral to optic disc (directly behind lens) which has highest proportion of cones and some rods, making it the area of sharpest vision within the eye
What is the peripheral retina
- > remaining regions of the eye that aren’t the macula lutea which is primarily rods which are black/white receptors, functions most effectively in low light
- > look off to the side to see better in the dark
Layers of the retina
- Pigmented layer (non visual portion)
- > absorbs stray light and helps keep image clear - Neural Layer (3 layers of neurons)
- > photoreceptor layer
- > bipolar neuron layer
- > ganglion neuron layer
Cones vs Rods
Rods - > way more rods than cones, black/white photoreceptors, responsible for dim light vision
Cones - > colour vision
What makes up the cavities of the interior of the eyeball
(anterior to lense)
- > filled with aqueous humor (continuously drained)
- > anterior chamber (above iris)
- > posterior chamber (above lens under pupil)
(posterior to lens)
- > filled with vitrous fluid (cannot be replaced/replenished)
Aqueous Humor
- > contiually produced by the ciliary body
- > water-like substance
- > drained by canal of schlemm (scleral venous sinus)
glaucoma
- > problem with drainage of the aqueous humor
- > increases intraorbital pressure and can lead to blindness
vitrous fluid
- > formed during embryonic developement
- > cannot be replenished
- > jelly-like substance
- > “floaters” are debris in vitreous body of older ppl
Optic chiasm
X-shaped structure formed by the crossing of the optic nerves in the brain, connects brain to the eyes
