Download Sensory System Note Guide

Learning Objectives
Introduction to
Medical Careers
SENSORY SYSTEM
• Define at least 10 terms relating to the
sensory system.
• Describe the function of the sensory
system.
• Identify at least 10 sensory system
structures and the function of each.
• Describe at least five disorders of the
sensory system.
Key Terms
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Accommodation
Auditory
Cutaneous
Equilibrium
Gustatory
Intraocular
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•
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Olfactory
Receptor
Refraction
Stimulus
Vision
What are the senses?
Sight
Eyes
Structure and Function
• Sensory system consists of receptors in
specialized cells and organs that perceive
changes in the internal and external
environment
• The stimuli cause nerve impulses that are
sent to the brain for interpretation
• Environmental stimuli are perceived with
the senses of vision, hearing, touch, taste,
position, and balance
Smell
Hearing
Nose
Ears
Taste
Touch
Skin
Tongue
Eye
• Considered the most important
sensory organ
• 60-90% of all information to
the brain is via the eyes
• 20% of the structure is
exposed
• Structure - 3 parts
External
Eye Ball
Internal
1
Eye ball
Sclera
(i) Sclera- white part,
supports and gives
structure
(e) Cornea- focuses
images (outer)
(b) Iris- colored part,
dilates and contracts
to let light in
(d) Pupil- black dot,
allows light in
(f) Lens- focuses images
(inner)
(k) Optic nerve- transmits
info to the brain
Optic N.
Iris
Pupil
Cornea
Lens
Internal
External
Skeletal cavity
Eye lid & lashes
Mucous membrane
Vision
Rods
100 million, sensitive
to dim light
Cones
7 million, see bright
light and color (red,
green, blue)
(m) Retina
back part of the eye
that contains the
rods/cones
Retina
Figure 20-2 Eye Functions Like
A Camera
• When we see something, light refracts from
object -> cornea, where the rays are bent (and
turned upside down), to the lens where the rays
are focused onto the retina.
• The retina then turns the
image into nerve impulses
and sends to the brain
via the optic nerve
2
Ear
Hearing
• Used for hearing
• Maintains equilibrium
• Structure
external
middle
inner
How Hearing Works
• Middle Ear
– Contains the Tympanic Membrane (ear drum)
• Moves according to the type of sound waves that
vibrate it, transmits sounds to the inner ear.
• Can also protect the inner ear from sounds which
may damage it.
• Pressure is equalized between the ear and the
mouth with the Eustachian Tube.
How Hearing Works
• Inner Ear
– Cochlea
• Contains fluid which transmits sound vibrations to
the hairs in the organ of Corti.
How Hearing Works
• Outer Ear (Pinna)
– Collects sound, channels to the middle ear.
– The sound at this point is mechanical sound
waves
How Hearing Works
• At this point, the sound waves are
vibrating the ear drum, and these waves
have to be passed through the ossicles
– Malleus
– Incus
– Stapes
Equilibrium
• Semicircular Canals
– Contain fluid that moves around when we
move, telling our brain where we are
positioned.
– Organ of Corti
• Hairs collect sound and send it to the Cochlear
nerves, which carry the sound vibrations to the
brain.
3
Tongue
Taste
taste is perceived by
specialized cells
called taste buds
(papillae)
Over 10,000 of these,
each with 50-150
receptor cells
Nose
Smell
smell originates in receptors in the
nose and travels to the brain via
nerves
sense of smell is 10,000x more
sensitive than taste
5,000 different smells can be
perceived
30 primary “pure” odors
(peppermint, floral, etc)
Skin
Touch
5 specialized cells in the skin sensitive to:
touch
pressure
temp
pain
Also sensitive to knowing where you are in
space.
4
Acorcnidg to a sutdy at cimadbrgie uirstneiy,
it dsenot mtaetr waht odrer lterets are,
olny that the fisrt and lsat are rgiht
A
BIRD
IN THE
THE BUSH
5
Assessment Techniques
• Sight
– Ophthalmoscope examines inner structure of
the eye
– Visual acuity with Snellen Test
Assessment Techniques
(Continued)
• Hearing
– Otoscope is used to view the structures of ear
– Impedance testing measures flexibility of the
tympanic membrane
6
Disorders of the Sensory
System
• Achromatism
– Called color blindness, is a common inherited
defect
•
Amblyopia
– Also called “lazy eye,” is poor vision in one
eye often resulting from better vision in the
other eye during infancy or early childhood
Disorders of the Sensory
System (Continued)
• Astigmatism
– A congenital defect causing imperfect
curvature of the cornea resulting in blurred
vision
• Cataract
– Clouding of the lens that causes blurred or
partial vision
• Conjunctivitis
– Also called pink eye, is a bacterial or viral
inflammation of the eyelid
Disorders of the Sensory
System (Continued)
• Diplopia
– Or double vision, results from muscle
imbalance or paralysis of an extraocular
muscle
• Epistaxis
– Nosebleed resulting from disease, trauma, or
other conditions such as hypertension,
leukemia, or rheumatic fever
Disorders of the Sensory
System (Continued)
• Glaucoma
– An increase in the pressure inside the eye,
caused by trauma or hereditary factors
• Hyperopia
– Farsightedness resulting from a congenital
deformity in the eye
• Macular degeneration
– A slow or sudden painless loss of central
vision
7
Disorders of the Sensory
System (Continued)
• Myopia
– Nearsightedness resulting from a congenital
deformity in the eye
Disorders of the Sensory
System (Continued)
• Otitis media
– A middle ear bacterial or viral infection
common in young children
• Night blindness
– Poor vision in dim light that results from a
deficiency in the rods of the retina
Disorders of the Sensory System
(Continued)
• Rhinitis
– Inflammation of the lining of the nose caused
by allergic reaction, viral infection, sinusitis, or
chemical irritants
• Ruptured eardrum
– Results from infection, an explosion, a blow to
the head, or a sharp object inserted into the
ear
Disorders of the Sensory
System (Continued)
• Sinusitis
– A chronic or acute inflammation of the
cranium
• Stye
– Bacterial infection of the sebaceous glands of
the eyelid
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