Special Senses I Flashcards
sensory information
- always surrounds us
- gives info about inside and outside environments
- detected by receptors and sent to brain
- tough, taste, hearing, vision, smell, equilibrium
receptors
- respond to stimuli
- initiate sensory input to CNS
- simple and complex structures
stimuli
- changes in sensory info
- detected by receptors
- pleasurable or alert to danger or moment-to-moment info
sensation
- conscious awareness of stimulus
- only stimulus that reaches cerebral cortex
- only a fractions of stimuli
- much input relayed to lower areas of brain
- response initiated without awareness
receptors as transducers
- change from one energy form to another
- original energy specific type of receptor
- energy is transducer to electrical energy, then conducted along an afferent sensory neuron
distribution receptors
- general sense receptors
- special senses receptors
general sense receptors
- throughout body
- in skin and internal organs
- simple in structure
somatic and visceral
somatic sensory receptors
- skeletal muscles
- in skin, joints, muscles, tendons
- detect pressure, vibration, pan, stretch
visceral sensory receptors
- smooth muscles
- in walls of viscera
- blood vessels, hear, stomach, intestines, bladder
- respond to temperature, chemicals, stretch, pain
special senses receptors
- in head
- specialized complex sense organs
- 5 special senses: gustation, olfaction, vision, hearing, equilibrium
stimulus receptors (9)
- exteroceptors
- interoceptors
- proprioceptors
- chemoreceptors
- thermoreceptors
- photoreceptors
- mechanoreceptors
- baroreceptors
- nocireceptors
exteroceptors
stimuli from external environment
interoceptors
stimuli from internal organs
proprioceptors
body and limb movements in space
chemoreceptors
chemicals in the environment (taste, smell)
thermoreceptors
temperature changes in environment and body
photoreceptors
in the eye, detect light intensity, colour, movement
mechanoreceptors
touch, vibration, pressure, stretch
baroreceptors
pressure changes in organs and vessels
nocireceptors
painful stimuli
high pain
somatic/skeletal
visceral/smooth
referred pain
- sensory nerve signals from certain viscera
- not perceived as originated from an organ, perceived as coming from dermatomes of skin
- same ascending tracts within spinal cord that house cutaneous and visceral sensory neurons
- sensory cortex unable to differentiate actual and false stimuli
- stimulus localized incorrectly
sites of referred pain: cardiac problems
- receive sympathetic innervation from T1-T5
- pain of myocardial infraction sometimes referred here
- pain along medial side of left arm
sites of referred pain: kidney and ureter pain
- referred along T10-L2 dermatomes
- overlie inferior abdominal wall in groin and loin
special senses
- smell, taste, vision, hearing, equilibrium
- in complex sensory organs
- olfaction and gustation are chemoreceptors
olfactory epithelium
- covers superior nasal cavity and cribriform plate
- 3 types of receptor cells
- only detect smell when the molecules hit the olfactory epithelium
3 types of olfaction receptor cells
1) olfactory receptors
2) supporting cells
3) basal cells
olfactory receptors
- bipolar neurons (CN 1) with cilia or olfactory hairs
supporting cells
- columnar epithelium
basal cells
- stem cells
- replace receptors monthly
olfactory glands
- Bowmans glands
- helps to stop smelling stimuli
- helps detach bond of odourant molecules
gustatory sense
- requires dissolving of substances in water or saliva
- sour, bitter, sweet, salty, and umami
- taste buds are in a papillae
- taste buds are on tongue, soft palate, epiglottis, sides of valuate, foliate, and fungiform papillae
- not on fusiform papillae
3 cells types in gustation
- supporting cells
- receptor cells
- basal cells
anatomy of taste buds
- oval body with ~50 receptor cells surrounded by supporting cells
- gustatory hairs project upwards through taste pores
- basal cells develop into new receptor cells every 10 days
sweet taste
- produced by organic compounds
- sugar, artificial sweeteners
salty taste
- produced by metal ions
- Na+, K+
sour taste
- associated with metal ions
- vinegar
bitter taste
- produced by alkaloids
- unsweetened chocolate
umami taste
- related to amino acids
- proteins to produces meaty flavour
threshold for taste
- most sensitive to bitter (poison)
- least sensitive to salty and sweet
adaptation
- when you stimulate a neuron so much that it stops sending the signal
- complete adaptation in 1-5 minutes
mechanism of taste
- dissolved substances contacts gustatory hairs
- nerve impulse formed on 1st order neurons
accessory structures of the eye
- eyelids
- eyelashes
- eyebrows
- lacrimal glands
eyelashes and eyebrows
- help protect from foreign objects, perspiration, and sunlight
- sebaceous glands found at base of eyelashes
sty
- when glands at base of eyelashes become infected
- inflammation of oil glands
eyelids
- protect and lubricate eye
- palpebral fissure is gap between eyelids
lacrimal apparatus
- ~1mL of fluid produces per day
- fluid spread over eye by blinking
- contains bacterial enzyme called lysozyme
flow of tears
1) lacrimal gland
2) excretory lacrimal ducts
3) superior or inferior lacrimal canal
4) lacrimal sac
5) nasolacrimal duct
6) nasal cavity
conjunctiva
- thin, clear, moist membrane
- lines insides of eyelids and coats outer surface of eye
conjunctivitis
- pink eye
- inflammation of conjunctiva
- cause by allergies, viruses, or bacteria
anatomy of internal eye
1) fibrous tunic: sclera, cornea
2) vascular tunic: iris, ciliary body, choroid
3) retina: pigmented layer, neural layer
cornea
- avascular
- transparent
- helps focus light
- parallel collagen fibers
- nourished by tears and aqueous humor
cornea transplants
- common and successful
- no blood vessels so no antibodies to cause rejection
sclera
- white of eye
- dense irregular connective tissue layer (collagen and fibroblasts)
- provides shaped support
- sclera venous sinus is opening at junction of sclera and cornea
- posteriorly pierced by optic nerve (CNII)
choroid
- pigmented epithelial cells (melanocytes) and blood vessels
- provides nutrients to retina
- black pigment in melanocytes absorb scattered light
ciliary body
- ciliary process: folds on ciliary body, secrete aqueous humour fluid, where suspensory ligaments attach
- ciliary muscle: Smooth muscle that alters shape of lens, controls tension on ligaments and lens
iris
- coloured part of eye, flat donut
- suspended between cornea and lens
- hole in center is pupil
- regulates amount of light entering eye
- changes in size to let in different amounts of light
muscles of iris
- convector pupillae (circular) are innervated by parasympathetic fibers
- dilator pupillae (radial) are innervated by sympathetic fibres
- response varies with different levels of light
lens
- avascular
- crystalline proteins arranged in layers
- clear capsule, transparent
- held in place by suspensory ligaments
- focuses light of retina
cataracts
- clouding of lens
- genetic and habit factors
- cataract surgery is easy and common
retina
- posterior 3/4 of eyeball
- has optic disc
optic disc
- optic nerve exiting back of eyeball
- slightly medial from centre of retina
- no photoreceptors
- blind spot
- macula lutea
- peripheral retina
macula lutea
- where light comes directly in
- point of best vision
- rounded, yellowish region lateral to optic disc
- contains fovea centralis
fovea centralis
- small depressed pit
- highest proportion of cones
- few rods
- area of sharpest vision
peripheral retina
- remaining regions
- has primarily rods
- functions most effectively in low light
layers of retina
- pigmented layer
- neural layer
pigmented layer of retina
- non visual portion
- absorbs light
- helps keep image clear
neural layer of retina
- 3 layers of neurons
1) photoreceptor layer
2) bipolar neuron layer
3) ganglion neuron layer
rods
- shades of grey in dim light
- shapes and movements
- 120 million rod cells
- distributed along periphery
cones
- sharp
- colour vision
- 6 million
- fovea of macula luted is where they are concentrated (densely packed region, at exact visual axis of eye, sharpest resolution or acuity)
anterior cavity of eye
- filled with aqueous humor
- produced by ciliary body
- continually drained
2 chambers of anterior cavity of eye
1) anterior chamber: cornea to iris
2) posterior chamber: iris to lens
posterior cavity of eye
- filled with vitreous body
- formed once during embryonic life
- “floaters” are debris in vitreous of older individuals
vitreous body
- formed once
- jellylike
- cannot be replaces
- eye is useless if it is damaged
aqueous humor
- always being produced by ciliary body
- flows from posterior chamber into anterior through pupil
- ciliary process secretes aqueous humor
- canal of Schlemm
canal of Schlemm
- scleral venous sinus
- openings at junction of cornea and sclera
- drains aqueous humor from eye to bloodstream
glaucoma
- problem with drainage of aqueous humor
- increased intraocular pressure over time can lead to blindness
- too much pressure on lens
visual pathway
1) optic nerve
2) optic chasm
3) optic tract
4) lateral geniculate nucleus of thalamus
5) optic radiations
6) primary visual area of cortex in occipital lobe
