82 terms

Chapter 9: Sensory System

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Mechanoreceptors
Stimulated by changes in pressure or movement
Proprioreceptors
located in muscles; receptors detect reflex actions that maintain muscle tone, posture, relaxation stretching
Pressure receptor in skin
sensitive to touch
Hair cells in ears
bend to send sound info
Thermoreceptors
Stimulated by changes in temperature
Pain Receptors
stimulated by tissue damage
skin and internal organs
where are pain receptors found?
Chemoreceptors
Stimulated by chemical concentration of substance
taste buds and olfactory cells
work together; sensitive to molecules in foods and scents
chemoreceptors in carotid and other arteries
detect pH of blood
Photoreceptors
stimulated by changes in light; rods and cones in retina
touch
(sense)
- Mostly receptors in skin
- Receptors for pressure (mechanoreceptors)
- Receptors for temperature (thermoreceptors)
- Receptors for pain
Taste and Smell
(sense)
- Chemoreceptors
- Covered together because they are hard to separate
taste buds
- Located in papillae on the tongue
- Respond to chemicals
- Send info to brain along lingual nerve
Olfactory cells
- In nasal cavity
- Specialized endings of olfactory nerve
- Contain cilia which pick up chemicals and send to brain
Hearing
(sense)
- Mechanoreceptors are in ears
- Receptors located in hair cells in inner ear
Eyebrows
protection from debris and sun
eyelids
continuation of skin, protection and lubrication
eyelashes
trap dirt, help lubricate eye
lacrimal apparatus
Produces tears to clean eye; Lubricates eye
Extrinsic eye muscles
3 pairs of muscle that anchor eye and move eye
Sclera
• White fibrous connect tissue
• Outermost layer, encircles entire eye
• Anteriorly it is transparent, forms cornea
• Posteriorly it is opaque
• Protects eye, supports eyeball
Choroid coat
• Middle layer
• Contains blood vessels
• Anteriorly forms iris, pupil, ciliary body
• Posteriorly dark pigment, absorbs stray light rays, also nourishes retina
Retina
• Innermost layer of eye
• Thin membrane containing photoreceptors
• Attached anteriorly to ciliary body
• Attached posteriorly to optic nerve
• Only 2 attachments, can become loosened, problem
Cornea
Tough membrane through which light is admitted to part of sclera (tough connect tissue) but clear, protects eye, refracts light rays
Aqueous humor
Anterior chamber of eye, watery fluid between cornea and iris, protects eye, helps eye keep shape, refracts light rays
Iris
Colored part of eye, surrounds pupil, anterior to lens, formed from choroid layer, regulates the size of pupil, protects eye from intense light
Pupil
Black circular opening in center of iris, admits light into eye
Ciliary body
Part of choroid layer, holds lens in place, allows lens to accommodate
lens
Hard but flexible, oval, refracts and focuses light rays on retina, divides eye into anterior and posterior parts
Vitreous humor
Jellylike fluid filling posterior chamber of eye, helps eyeball keep its shape, refracts light rays
Retina
Innermost layer, contains photoreceptive cells, rods and cones, sends light info to brain
Rods
Photoreceptor cells on retina, responsible for black and white vision, function in low light levels
Cones
Photoreceptor cells on retina, responsible for color vision, function in high light levels
Fovea centralis
Depression on retina, area of greatest concentration of cones, greatest visual acuity
optic nerve
Exits eye posteriorly, carries light info to brain, there are neither rods nor cones at spot where nerve exits eye, so this is a blind spot
Tapetum lucidum
A beautiful layer of choroid only seen in animals with night vision, reflective layer that improves night vision
Astigmatism
- Uneven cornea, dips in cornea
- Light rays aren't evenly focused
- Fuzzy areas in field of view
Near-Sightedness
- Myopia
- Due to elongated eyeball
- Can see close objects, but can't see letters 20 ft away
- Lens focuses in front of retina for distant object
- Concave lens fixes problem
Far-Sightedness
- Hyperopia
- Due to shortened eyeball
- Can see distant, but not close up
- Lens focuses light rays behind retina
- Convex lens fixes problem
Glaucoma
- Buildup of fluid in anterior chamber due to duct blockage
- Pressure compresses arteries that serve retina
- Nerve fibers can die, blindness can result
papillae taste buds
where taste buds are nested
accommodation
Ability of the lens to change shape when viewing things up close
close
When viewing _____ objects, ciliary muscle contracts and lens becomes more convex, rounded
distant
When viewing _____ objects, ciliary muscle relaxes, lens flattens
Convergence reflex
As object being viewed moves closer to eyes, eyeballs move medially in order for light rays to strike equivalent spots on retina
Photopupillary reflex
When light entering the eye is intense, circular muscle of iris contracts, size of pupil decreases; when light entering eye is dim, circular muscle of iris relaxes allowing more light in, size of pupil increases
blind spot
Spot where the optic nerve exists where there are no rods or cones
pinna
- External flap
- Gathers and collects sound waves
- Also can deflect sound that is too loud
external auditory canal
- Sends sound waves to middle ear
- Has ceruminous (wax) glands to help clean ear and keep out foreign substances
tympanic membrane
- Eardrum
- Transfers sound waves to middle ear bones
Eustachian tubes
- Connects to throat
- Relieves pressure
Semicircular canals and chochlea
- Balance
- Cochlea: hearing, sound waves transferred from middle ear, stimulate hair cells
hair cells
When bent these send sound info to brain
60
how many decibels is normal conversation?
130
how many decibels is a rock concert?
90
what is the highest amount of decibels ears can be exposed to without needing protection?
1. Pinna
2. External auditory canal
3. Tympanic membrane
4. Malleus
5. Incus
6. Stapes
7. Oval window
8. Organ of Corti in the cochlea
Order of Signal Transmission for Hearing
eyelid
conjunctiva lines its inner surface
inferior oblique
rotates the eye clockwise
lacrimal gland
secretes tears
lacrimal sac
drains the tears into the nose
lateral rectus
turns the eye away from the midline
medial rectus
turns the eye toward the midline
orbit
consists of seven skull bones
superior rectus
rolls the eye upward
cone
receptor cell for color vision
choroid
middle, dark brown eye layer
fovea centralis
the majority of light falls here for acute vision
lens
attached to the ciliary body by suspensory ligaments
optic nerve
transmits impulses to the brain for sight
pupil
hole through the iris
rod
receptor cell for black-and white vision
sclera
outer, white covering of eye
auditory tube
extends from the middle ear to the nasopharynx
cochlea
contains receptor cells for hearing
incus
middle ear bone
pinna
external ear flap
round window
opening covered with a membrane in ear
semicircular canals
contribute to the sense of dynamic equilibrium
tympanic membrane
eardrum
vestibule
contains the uricle and sacule