Special+Senses
Essentials of Human Anatomy & Physiology - Chapter 8: Special Senses
Page 1
Textbook Information
Title: Essentials of Human Anatomy & Physiology
Edition: Seventh Edition
Author: Elaine N. Marieb
Publisher: Pearson Education, Inc. (Benjamin Cummings)
Lecture Slides by Jerry L. Cook
Page 2
Types of Senses
General Senses
Touch
Temperature
Pressure
Pain
Special Senses
Smell
Taste
Sight
Hearing
Equilibrium
Receptor Types
Large sensory organs (eyes, ears)
Localized clusters (taste buds, olfactory epithelium)
note: there are responsible sensors in our toungue that has respetive taste
Page 3
The Eye and Vision
70% of sensory receptors are in the eyes
Each eye contains over a million nerve fibers
Protection
Enclosed in a bony orbit
Surrounded by a cushion of fat
Page 4-7
Accessory Structures of the Eye
Eyelids and Eyelashes(closes eyes)
Glands
Meibomian glands: Produce oily secretion for lubrication
modified sebaceous glands which makes the eyes move smoothly
Ciliary glands: Modified sweat glands
testosterone- makes hair grow
Conjunctiva
memrane that Lines eyelids and connects to the eye surface
Secretes mucus for lubrication
Lacrimal Apparatus
Lacrimal gland: Produces lacrimal fluid (tears)
Lacrimal canals: Drain fluid from eyes
Lacrimal sac and nasolacrimal duct: Passage to nasal cavity
lacrimal sac- provides passage towards nasal cavity
eyes, nose, throat, ears are connected through a hollow cavity (cavity is empty)
Nasolacrimal duct- empties lacrimal fluid into nasal cavity
Page 8
Function of the Lacrimal Apparatus
Lacrimal fluid: Dilute (weakend by water) salt solution containing antibodies and lysozyme
Protects, moistens, and lubricates the eye
fluid is not allowed in the eyess hence empties into the nasal cavity
Page 9
Extrinsic Eye Muscles
Muscle Attach to the outer surface of the eye
Enable gross eye movements and tracking of moving objects
Page 10-12
Structure of the Eye
wall is Composed of three tunics: coats while the interior is filled withh fluid called humors
Fibrous Tunic (Sclera): White connective tissue layer
“white of the eye” taht can see anteriorly
Cornea: Transparent, central anterior portion that allows for light to pass through
can repairs itself easily
human tissue that can onl,y be transplanted without fear of rejection- no blood vessels
Choroid: Blood-rich nutritive tunic
layer with dark pigment to prevent light from scattering inside the eye
Contains :
ciliary body - smooth muscle to which the lenses is attached
iris- pigment layer (eye color)
pupil- rounded opening in the iris for light enter
dilates or ontracts on the light
Sensory Tunic (Retina): Contains photoreceptors (rods and cones)
signals pass from photoireceptors via neuron chain
bipolar neurons
ganglion cells
signals retina to leave toward the brain through the optic nerve
Page 13-16
Neurons of the Retina
Photoreceptors
Rods: found towards edges of the retina
Dim light and peripheral vision
all in gray tones
Cones: detailed Color vision in bright light. denstest center of the retina
Fovea centralis: Area with only cones which makes lateral to each blid spot
Blind spot: No photoreceptor cells where the optic nerve leaves te eyeball
Page 17-20
Cone sensitivity- There are three types of cones
Different cones are
sensitive to different
wavelengths
lack of one cone type results of color blindness
Impulses received at the
same time are interpreted
as intermediate colors
Lens and Internal Eye Chamber Fluids
Lens: Biconvex structure for focusing light
held by suspensory ligaments attached to the cillary of the body
tells whether u can see or not
Aqueous Humor: Watery fluid (loc: between lens and cornea) that helps maintaining intraocular pressure
provides nutrients and reabsorbed into venous blodd through canal of Schlemm
Vitreous Humor: Gel-like substance (behind the lens) preventing eye collapsing inward reinforcing it internally
lasts a lifetime and is not replaced
Cataracts and Glaucoma: Conditions affecting lens and aqueous humor drainage
Cataracts- lens becomes increasingly
hard and opaque over time
requiring a transplant or
special glasses
Glaucoma- drainage of
aqueous humor is blocked and pressure
within the eye increases dramatically and
compresses the delicate retina and optic
nerve causing pain and blindness
Page 21-26
Lens Accommodation and Visual Pathway
Light must focus on the retina for optimal vision that is done by lens
The resting eye is set
for distance vision
(over 20 ft away)
lens must change shape to focus for closer objects-accomodation
Visual Pathway: Signals from retina to optic nerve, crossing at optic chiasma, synapsing in thalamus, and reaching visual cortex of the occipital lobe
Real image (reversed left to right, and
upside down) formed on the retina
Photoreceptors of
the retina
Optic Nerve - crosses at the optic chiasma to the opposite side
Fiber tracts that
result are the optic
tracts
Page 27-30
The Ear
Houses senses of hearing and equilibrium
Divided into three areas: Outer, Middle, and Inner ear
External Ear: Pinna and external auditory canal
Middle Ear: Air-filled cavity with ossicles (malleus, incus, stapes)
Page 31-35
Inner Ear
Bony labyrinth containing cochlea, vestibule, and semicircular canals
Organ of Corti: Contains hair cells for hearing
Mechanisms of hearing involve vibrations and action potentials
Page 36-44
Organs of Equilibrium
Static Equilibrium: Maculae in vestibule report head position
Dynamic Equilibrium: Crista ampullaris in semicircular canals respond to head movements
Page 45-54
Chemical Senses: Taste and Smell
Both senses use chemoreceptors
Olfaction: Olfactory receptors in nasal cavity detect chemicals
Taste: Taste buds located on tongue and other areas
Types of taste sensations: Sweet, Sour, Bitter, Salty
Developmental aspects: Special senses functional at birth, eyes as outgrowths of the brain
This note summarizes the key concepts and details from Chapter 8 on Special Senses, providing a structured overview of the anatomy and physiology of the eye and ear, as well as the chemical senses of taste and smell.