Lab 11: Special Senses Flashcards
Sensation
conscious/subconscious awareness of changes in internal/external environment.
General Senses
- somatic senses - touch, pressure, pain, temperature and proprioception
- visceral senses - provides information about internal organs
Special Senses
- vision, hearing, equilibrium, taste and smell
* distinct receptor cells restricted to the head
Adipose tissue function in eye
padding and insulation within the orbit to protect the eye.
Sclera
•“white of the eye” •Function: - protects/shapes eyeball - provides sturdy anchoring site for extrinsic eye muscles - oppose pulling forces of eye muscles
Cornea
• transparent, anterior portion of sclera
•Function:
- allows light to enter eye
- helps bend (refract) light rays so they focus on photoreceptors in retina.
Extrinsic eye muscles
- skeletal muscles provide rotary movements of the eye
- focus the eye for optimum vision
- anchor the eye in the bony orbit
- flat bands on the surface of the eye.
The wall of the eye is composed of three layers/tunics:
- Outer Layer (Fibrous Tunic): sclera and the cornea.
- Middle Layer (Vascular Tunic): iris, the ciliary body and the choroid
- Inner Layer: retina
Iris
Function: Controls light that can enter back of eye
Lens
Function: flexible, changes shape to focus light
What is this fluid found in the anterior cavity in relation to the lens?
What is the function of this fluid?
- Aqueous Humor
- Clear, continuously fomred
- Function: forms a fluid cushion, maintain constant intraocular pressure, supply oxygen and nutrients to lens/cornea and carry away metabolic waste
What is this fluid found in the posterior cavity in relation to the lens?
What is the function of this fluid?
- Vitreous Humor
- Jelly like fluid, formed during embryonic life and lasts a lifetime
- Functions: help stabilize shape of eye, supports lens/retina, contributes to intraocular pressure
Ciliary Body
= ciliary processes + ciliary muscles
• ciliary muscles: control lens shape
• ciliary processes: contain capillaries that produce aqueous humor
Choroid
- highly vascular and darkly pigmented tissue
* Function: absorb excess light rays to prevent reflection, can deliver oxygen and nutrients to retnia
Retnia
Two Layers
• Outer pigmented layer - absorbs light
• Inner Neural layer - photoreceptors (rods & cones) + bipolar cells + ganglion cells.
Optic Disc
- ‘blind spot’
- Light focused on this area cannot be seen because it lacks photoreceptors
- where the optic nerve/blood vessles leave eye
Photoreceptors types
Cones:
• stimulated by bright light
• produce colour vision.
Rods:
• absent in fovea, more on periphery of retina
• stimulated by dimmer light
•produce shades of black, white and grey.
Macula Lutea
• The central portion of the macula lutea has a small depression known as the fovea centralis.
Fovea Centralis
- area of greatest visual acuity (sharpness of vision)
* contains only cones
Glaucoma
- develops if drainage of aqueous humor is blocked
* intraoccular pressure increases
Cataract
• Clouding of the lens
Accommodation
lens of the eye must become more rounded or convex in shape in order to view objects at close range
How do we see far (3)
- ciliary muscles relax
- suspensory ligaments stretch
- lens flattens
How do we see near (3)
- cilliary muscles contract (close = ciliary = contract)
- suspensory ligaments relax
- lens buldges
near point
- The closest distance at which an object appears to be in sharp focus
- change due to loss of lens elasticity
Visual acuity
degree of “sharpness” of eyesight.
Hyperopia (Hypermetropia)
- can see far
- short eyeball + flat lens
- Fix = converging lens (convex)
Myopia
- can see close
- long eyeball + curved lens
- Fix = diverging lens (concave)
Astigmatism
- Astigmatism: cornea or lens has irregularities in the surface curvature
- objects may be in focus in one axis and blurred in another axis.
The ear is divided into 3 main regions
- External ear: collects/channels sound waves inward
- Middle ear: transfers sound vibrations to oval window
- Internal ear: contains receptors for hearing/equilibrium.
External Ear
Two parts: auricle/pinna + external auditory canal/meatus
Auricle/pinna
•external ear, flap of skin/elastic cartilage
Function: Collects/directs sound waves into external auditory canal
External auditory canal/meatus
•external ear
• ceruminous (wax) glands to trap forign bodies and repel insects
Function: conduct airborne sound to tympanic membrane.
Tympanic Membrane
•external ear
Function - vibrates at frequency/amplitude of the sound that reaches it.
Middle Ear
- Air filled cavity in temporal bone
- Auditory ossicles: Bones of axiel skeleton, malleus, incus stapes Functions: transmits and magnifies vibrations fo tympanic membrane to oval window (stapes sits here).
- Auditory Tube
Auditory (pharyngotympanic) tube or eustachian tube
- middle ear
- goes to nasal pharynx.
- Funciton: used to equalize pressure on both sides of tympanic membrane to prevent it from rupturing.
Inner Ear
Outer bony labyrinth
- contains perilymph fluid.
- cochlea + vestibule + semicircular canals
Inner membranous labyrinth
- contains endolymph fluid
- cochlear duct + saccule and utricle + semicircular ducts
cochlear duct
- contains organ of Corti, the receptor organ for hearing.
- Special receptors (hair cells) convert sound waves into nervous impulses that are carried by the cochlear branch to the auditory area of cerebral cortex.
saccule and utricle
• Hair cells contain receptors to detect static equilibrium
semicircular ducts
- receptors for maintaining dynamic equilibrium
* Ampulla: contains equilibrium receptors (crista ampularis) where we detect dynamic equilibrium
Static vs. Dynamic Equilibrium:
Static Equilibrium: the position of head with respect to respect to gravity and linear acceleration. Saccule and utricle.
Dynamic equilibrium: position of head during rotational movement. Semicircular ducts.
Smell
- chemical sense
- Receptors = neurons
- Impulses from olfactory nerve (I) –> olfactory bulbs –> olfactory tracts –> primary olfactory area of cerebral cortex in temporal lobe.
Olfactory Adaptation
an adaptation of olfactory receptors to a certain smell. After you smell something for a while you stop detecting the smell.
Taste
- chemical sense
* receptors = modified skin cells
taste bud
- oval structure containing taste cells, supporting cells and basal cells
- Taste buds generally respond to a mixture of the five basic tastes.
- a single taste cell has receptors for only one of the basic taste sensations.
Five primary or basic
- sweet - organic substances (sugars, alcohols, some amino acids)
- sour - hydrogen ions (citric acid of lemon juice)
- bitter - nitrogen (caffeine, quinine, and nicotine)
- salt - metal ions (sodium and potassium)
- umami (savoury beef) - glutamate or other amino acids
- may also be a possible sixth taste that accounts for a liking of fatty foods
- all areas of the tongue can detect all five taste sensations.
