Transcript chap 10 lecture - Warren County Public Schools

PowerPoint Lecture Outlines
to accompany
Hole’s Human
Anatomy and Physiology
Tenth Edition
Shier w Butler w Lewis
Chapter
10
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
12-1
Chapter 10
Somatic and Special Senses
Sensory Receptors
• specialized cells or multicellular structures that
collect information
• stimulate neurons to send impulses along sensory
fibers to the brain
12-2
The Body Senses
• Skin Senses: there are three basic skin sensations:
touch, temperature, and pain.
• Vestibular Sense: sense of body orientation with
respect to gravity and three-dimensional space
– The semicircular canals provide the brain with balance information.
• Kinesthetic Sense: sensory system for body
posture, orientation and movement
– Kinsethetic receptors are found throughout the muscles, joints, and
tendons of the body.
Receptor Types
Chemoreceptors
• respond to changes in chemical concentrations
Pain receptors
• respond to tissue damage
Thermoreceptors
• respond to changes in temperature
Mechanoreceptors
• respond to mechanical forces
Photoreceptors
• respond to light
12-3
Sensory Impulses
• stimulation of receptor causes local change in its membrane
• a graded electrical current is generated that reflects intensity
of stimulation
• if receptor is part of a neuron, the membrane potential may
generate an action potential
• if receptor is not part of a neuron, the receptor potential must
be transferred to a neuron to trigger an actin potential
• peripheral nerves transmit impulses to CNS
12-4
Sensation and Perception
• Sensation is the process of receiving,
converting, and transmitting information from
the outside world.
– Sensory organs contain receptors that transduce
sensory energy into nerve impulses that are carried
to the brain.
Sensation/Perception
• Transduction: sensory receptors convert a
physical energy into nerve impulses
Sensory Reduction
• Sensory reduction involves the filtering and
analyzing of incoming sensations before
sending a neural message to the cortex.
– If the reticular formation decides that
information is important, it is passed on to alert
the cerebral cortex.
Sensory Thresholds
• Each sensory system has a threshold level of energy
that is required to activate that sense.
– Absolute threshold: The smallest amount of energy that
can be detected by a system.
– Difference threshold: The smallest difference in sensory
energies that can be detected.
• Different people can have widely varying sensory
thresholds.
• Thresholds can change within a person over time
and as a function of hormone status.
– Olfactory sensitivity during pregnancy
– Ability to taste foods as we get older
Modification of Sensation
• A key function of sensory systems is to detect
change within the environment.
– Movement in the peripheral aspects of the eye may
signal food or danger.
– Constant pressure of an object on the skin may not
be important.
• A stimulus that moves across the skin may be a snake or
a spider.
• The skin adapts to constant pressure.
Sensory Adaptation
• Sensory adaptation refers to the fact that
repeated or constant stimulation decreases
the number of sensory messages sent to the
brain, which causes decreased sensation.
Touch and Pressure Senses
Meissner’s corpuscles
• abundant in hairless portions
of skin
• detect light touch
Pacinian corpuscles
• common in deeper subcutaneous
tissues, tendons, and ligaments
• detect heavy pressure
12-7
Touch and Pressure Senses
12-8
Temperature Senses
Warm receptors
• sensitive to temperatures above 25oC (77o F)
• unresponsive to temperature above 45oC (113oF)
Cold receptors
• sensitive to temperature between 10oC (50oF) and 20oC
(68oF)
12-9
Referred Pain
• may occur due to sensory impulses from two regions
following a common nerve pathway to brain
12-11
Pain Nerve Fibers
Acute pain fibers
• thin, myelinated
• conduct impulses
rapidly
• associated with
sharp pain
• well localized
Chronic pain fibers
• thin, unmyelinated
• conduct impulses more
slowly
• associated with dull,
aching pain
• difficult to pinpoint
12-12
Special Senses
• sensory receptors are within large, complex sensory
organs in the head
• smell in olfactory organs
• taste in taste buds
• hearing and equilibrium in ears
• sight in eyes
12-16
Smell
Olfactory Receptors
• chemoreceptors
• respond to chemicals dissolved in liquids
Olfactory Organs
• contain olfactory receptors
•cover parts of nasal cavity and a portion of the nasal
septum
12-17
Olfactory Receptors
12-18
Taste
Taste Buds
• organs of taste
• located on papillae of tongue, roof of mouth, linings of
cheeks and walls of pharynx
Taste Receptors
• chemoreceptors
• taste cells – modified epithelial cells that function
as receptors
• taste hairs –microvilli that protrude from taste
cells; sensitive parts of taste cells
12-20
Taste Receptors
12-21
Taste Sensations
Four Primary Taste Sensations
• sweet – stimulated by carbohydrates (sugars,
saccharine, and some amino acids)
• sour – stimulated by acids
• salty – stimulated by salts; metal ions
• bitter – stimulated by many organic compound;
alkaloids
Spicy foods activate pain receptors
12-22
Do you taste food when are
congested? Why?
Hearing
Ear – organ of hearing
3 Sections
• External
• Middle
• Inner
12-24
Anatomy of the Ear
(Sound Waves)
Audition
• Receptors within the ear are tuned to detect
sound waves (changes in sound pressure
level).
– Sound waves vary in terms of:
• Frequency: corresponds to pitch
• Amplitude: corresponds to loudness
• Sound loudness is measured in decibels.
Sound Loudness (dB)
External Ear
• auricle (pinna)
• collects sounds waves
• external auditory meatus
(canal)
• lined with ceruminous glands
• carries sound to tympanic
membrane
• terminates with tympanic
membrane
• tympanic membrane (aka
eardrum)
• vibrates in response to sound
waves
12-25
Middle Ear
*begins at the eardrum and ends at the windows
* must maintain a certain amount of pressure for hearing
• tympanic cavity
• air-filled space in temporal
bone
• auditory ossicles
• vibrate in response to tympanic
membrane
•Smallest bones in the body
• malleus, incus, and stapes
(hammer, anvil, and stirrup)
• oval window
• opening in wall of tympanic
cavity
• stapes vibrates against it to
move fluids in inner ear
12-26
Auditory Tube
• (AKA) eustachian
tube
• connects middle ear to
throat
• helps maintain equal
pressure on both sides
of tympanic membrane
• always closed except
for yawning and
swallowing
12-27
Inner Ear
• complex system of labyrinths
(behind the eye)
• osseous labyrinth
• bony canal in temporal
bone
• filled with perilymph
• membranous labyrinth
• tube within osseous
labyrinth
• filled with endolymph
12-28
Inner Ear
3 Parts of Labyrinths
• cochlea
• functions in hearing
•Houses Organ of
Corti
• semicircular canals
•fxns in main-taining
balance, sensing mvmt,
& rotation
•(3 looped tubes @ rt.
angles
•Vestibule
•Fxn in equilibrium
•Btwn cochlea &
semicircular canals
12-29
Organ of Corti
• group of hearing receptor
cells (hair cells)
•different frequencies of
vibration move different parts
of membrane
• particular sound frequencies
cause hairs of receptor cells to
bend
• nerve impulse generated
•“snail”
12-32
Pathway of sound through the ear
•
•
•
•
•
•
External auditory canal
Eardrum
Ossicles
Fluid of inner ear
Cochlea
Brain
Summary of the Generation of
Sensory Impulses from the Ear
12-35
Mechanisms of Hearing
• High pitch sounds disturb receptor cells close to
the oval window and low pitch sounds
stimulate cochlea.
• Since sound usually reaches your ears at two
different times, we hear “in stereo.” This helps
determine where the sound comes from.
• Auditory receptors adapt or stop responding to
sound that keep reaching the ears.
• Hearing is the last sense to leave our awareness
before sleep, anesthesia (or death), and is the
first to return.
Hearing Loss
• Conduction deafness: Middle-ear deafness
resulting from problems with transferring sound
waves to the inner-ear.
– Causes can be earwax buildup, fusion of ossicles,
ruptured eardrum, & otitis media
• Sensorineural deafness: Inner-ear deafness
resulting from damage to the cochlea, hair cells, or
auditory nerve.
– Causes can be extended listening to loud sounds >90dB
• Equilibrium problems include nausea,
dizziness, and being unable to maintain
balance.
• Vertigo – sensation of spinning causing
nausea and vomiting; in severe cases you
cannot stand up
• Motion sickness – cause is abnormal and
irregular body motions that disturb the
organs of equilibrium; symptoms include
nausea, vomiting, dizziness, headache, and
prostration
Equilibrium
Static Equilibrium
• vestibule( specifically the
maculae)
• sense position of
head when body is
not moving
Dynamic Equilibrium
• semicircular canals
(crista ampullaris)
• sense rotation and
movement of head and
body
12-36
Macula
• responds to
changes in head
position
• bending of hairs
results in generation
of nerve impulse
12-38
Crista Ampullaris
12-40
Sight
Visual Accessory Organs
(accesory organs are those
not directly related to the
vision process but are
important in maintaining
eye health)
• eyelids
• lacrimal apparatus
• extrinsic eye muscles
12-41
Eye brain
proxomity
• Can you see :
• the optic
nerve bundle?
• Spinal cord?
Eyelid
•composed of four layers
• skin
• muscle
• connective tissue
• conjunctiva
• orbicularis oculi - closes
•conjunctiva – mucous
membrane; lines eyelid and
covers portion of eyeball
12-42
Eye disorders
• Conjunctivitis – inflammation of the
conjunctiva
• Pinkeye – inflammation of the conjunctiva
caused by bacteria/virus; very contagious
Lacrimal Apparatus
• lacrimal gland
• lateral to eye
• secretes tears
•lacrimal sac
• collects from canaliculi
• nasolacrimal duct
• collects from lacrimal
sac
• empties tears into nasal
cavity
12-43
• Tears contain lysozymes for cleansing and
protecting the eyes.
• Too many tears are secreted (in crying) =
congestion in the nasal cavity
• During a cold, inflammation can “stop up”
the canals or ducts, tears do not drain from
the eyes = “watery eyes”
• “Cross eyed” – results from unequal pulls
by external eye muscles. Treatment ;
exercise, glasses, or surgery.
Extrinsic Eye Muscles
Superior rectus
• rotates eye up and
medially
Inferior rectus
• rotates eye down
and medially
Medial rectus
• rotates eye
medially
12-44
Structure of the Eye
• hollow
• spherical
• wall has 3 layers
• outer fibrous tunic
• middle vascular tunic
• inner nervous tunic
12-46
Outer Tunic
Cornea
• anterior portion
• transparent
• light transmission
• light refraction
• sensitive to touch
• many nerves
•no blood vessels
Sclera
• posterior portion
•“white if eye”
• opaque
• protection
12-47
Middle Tunic
Iris
• anterior portion
• pigmented
• controls light intensity
Ciliary body
• anterior portion
• pigmented
• holds lens
• moves lens for focusing
Choroid coat
• provides blood supply
• pigments absorb extra light
12-48
Iris
• composed of connective
tissue and smooth muscle
• pupil is hole in iris
• dim light stimulates
radial muscles and pupil
dilates
• bright light stimulates
circular muscles and
pupil constricts
12-53
**The iris is made of two
pigments**
• 1. front layer - varying amounts of melanin
based on genetics
• 2. back layer – blue pigment
Anterior Portion of Eye
• filled with aqueous humor
12-49
Lens
• transparent
• biconvex
• lies behind iris
• largely composed of
lens fibers
• elastic
• held in place by
suspensory ligaments
of ciliary body
12-50
Accommodation
• changing of lens shape to view objects
12-52
Eye Disorders
• Cataracts – lens becomes hard and opaque;
causes blindness
• Astigmatism – caused by an imperfect
curvature in the cornea or lens; makes
changing what you are trying to focus on
difficult; corrected with glasses
Ciliary Body
• forms internal ring around front of eye
• ciliary processes – radiating folds
• ciliary muscles – contract and relax to move lens
12-51
Controlling light
levels
• Your eye are very
sensitive and can be
damaged by harsh
light.
• Your iris controls
light allowed into
the eye by changing
the size of the pupil
Aqueous Humor
• fluid in anterior cavity of eye
• provides nutrients
• maintains shape of anterior portion of eye
12-54
Inner Tunic
• retina
• contains visual receptors
• continuous with optic nerve
•composed of several layers
•fovea centralis –produces sharpest vision
• optic disc – blind spot; contains no visual receptors
• vitreous humor – thick gel that holds retina flat against
choroid coat
12-55
Retina – receives the image
• Full of light
receptors which
are sensitive to:
• Colour
• Light levels
• Massive blood
supply is also
needed
Fovea is the main
focal point and has
greatest density of
light receptors
Pathway of light through the eye
•
•
•
•
•
•
•
Cornea
Aqueous humor
Lens
Vitrous humor
Retina
Optic nerve
Brain (occipital lobe)
Light Refraction
Refraction
• bending of light
• occurs when light waves pass at an oblique angle into
mediums of different densities
12-57
Types of Lenses
Convex lenses cause
light waves to converge
Concave lenses cause
light waves to diverge
12-58
Focusing On Retina
• as light enters eye, it is refracted by
• convex surface of cornea
• convex surface of lens
• image focused on retina is upside down and reversed from
left to right
12-59
Visual Receptors
Cones
Rods
• contain light sensitive
•contain light sensitive
pigments called
pigment called rhodopsin
erythrolabe, chlorolabe,
• hundred times more
and cyanolabe
sensitive to light than cones
• provide vision in bright
• provide vision in dim light
light
• produce colorless vision
• produce sharp images
• produce outlines of objects
• produce color vision
12-60
Disorders of the eyes
• Night blindness – problem with rod fxn.
Caused by a Vit. A deficiency
• Color blindness – lack of all cones (total);
lack of one cone (partial)
• Glaucoma – results from unequal pressure
which compresses on the retina and optic
nerve; can result in blindness; progresses
slowly which no early symptoms
Stereoscopic Vision
• provides perception of distance and depth
• results from formation of two slightly different retinal
images
12-63
Visual Pathway
12-64
Developmental Aspects
•Formed very early in embryonic development
•Eyes are developed by 4th week
•Vision is the only sense not fully functional at birth
•Eyeballs grow until age 8-9
•Newborns only see in gray tones
•Lacrimal glands are not fully developed
•until about 2 weeks old, the baby is tearless
12-65
Life-Span Changes
Age related hearing loss due to
• damage of hair cells in organ of Corti
• degeneration of nerve pathways to the brain
• tinnitus
Age-related visual problems include
• dry eyes
• floaters (crystals in vitreous humor)
• loss of elasticity of lens
• glaucoma
• cataracts
• macular degeneration
12-65
Clinical Application
Refraction Disorders
• concave lens corrects
nearsightedness
• convex lens corrects
farsightedness
12-66