Chapter 9 Sensory Systems
Dec 25, 2015
Chapter 9
Sensory Systems
Announcements
• Chapter 8a- Extra credit (10 pts)• Chapter 8 online quiz- Due Wednesday!• Quiz 7 Wednesday- Chapters 8, 9• Midterm grades updated
Chapter Outline
• Kinds of Sensory receptors• Vision and the eye• Hearing, balance, and the ear• Smell and taste
Perry joined the National Guard and was sent overseas to a war zone. While on duty, an improvised explosive
device went off near him and he barely escaped unharmed. What would be true of his nervous system?
• A) Parasympathetic impulses were increased. • B) Most sympathetic impulses were reduced. • C) The sympathetic neurons all released
acetylcholine. • D) Norepinephrine and epinephrine were
released.
Sensory System
• Sensory receptors generate electrochemical messages in response to stimuli
• Receptors are classified by the type of stimulus to which they respond
• Receptors for the general senses are distributed throughout the body
• Vision depends on the eye • Hearing depends on the ear
Sensory Receptors Generate Electrochemical Messages
• Sensory receptors respond to stimuli by generating electrochemical messages
• All sensory receptors are selective, responding best to one form of energy
Sensory Receptors Generate Electrochemical Messages
Figure 9.1
Step 1: A sensory receptor detects the stimulus from the external or internal environment.
Step 2: Sensory neurons conduct a nerve impulse to the spinal cord and then to the brain, or directly to the brain.
Step 3: The brain interprets the information from the sensory receptor.
Step 4: The brain’s interpretation of the information is a perception or understanding of the stimulus.
Stimulus
Sensory receptor
Nerve impulse carried by sensory nerves
Spinal cord Brain
Sensory Receptors
• Continuous stimulation leads to sensory adaptation, a decrease in the awareness of the stimuli
Receptor Classification
• The body contains many specialized receptors including – Mechanoreceptors– Thermoreceptors– Photoreceptors– Chemoreceptors– Pain receptors
Receptor Classification
• Receptors for the general senses are located throughout the body
Receptor Classification
• Receptors rely on either free nerve endings or encapsulated nerve endings– Free nerve endings are the tips of dendrites of
sensory neurons– Encapsulated nerve endings are those in which a
connective tissue capsule encloses and protects the tips of dendrites of sensory neurons
Receptor Classification
Figure 9.2 (1 of 2)
Receptor Classification
Figure 9.2 (2 of 2)a
Receptor Classification
Figure 9.2 (2 of 2)b
Receptor Classification
• The special senses – Vision– Hearing– Equilibrium– Smell – Taste
Receptors for the General Senses
• Mechanoreceptors located in the skin perceive touch and pressure
Receptors for the General Senses
• Free nerve endings in Merkel disks receive touch, as do the encapsulated nerve endings in Meissner’s corpuscles
Receptors for the General Senses
Figure 9.2 (2 of 2)c
Receptors for the General Senses
Figure 9.2 (2 of 2)d
Receptors for the General Senses
• Pacinian corpuscles – Respond to pressure when it is first applied
• Ruffini corpuscles – Respond to continuous pressure
Receptors for the General Senses
Figure 9.2 (2 of 2)e
Receptors for the General Senses
Figure 9.2 (2 of 2)f
Receptors for the General Senses
• Body and limb position are detected by – Muscle spindles responding to the stretch of a
muscle – Golgi tendon organs measuring muscle tension
Receptors for the General Senses
• Pain receptors are found in all tissues of the body
• Referred pain– Pain felt somewhere besides the site of the injury– Common with damage to internal organs
Receptors for the General Senses
Figure 9.3
Lungs anddiaphragm
Heart
Stomach
Liver andgallbladder
Small intestine
Colon
Appendix
Urinarybladder
Kidney
Testes
Ureter
Vision Depends on the Eye
• The outer layer of the eye is made of – The sclera • Protects and shapes the eye • Provides attachment for muscles
– The cornea• Allows light to enter
Vision Depends on the Eye
Table 9.1 (2 of 4)
Vision Depends on the Eye
Table 9.1 (3 of 4)
Vision Depends on the Eye
Table 9.1 (4 of 4)
Vision Depends on the Eye
Figure 9.4
Retina
FoveaOptic disk(blind spot)
Optic nerve
Choroid
Sclera
Vitreous humor(fills the posteriorchamber)
Iris
Ciliary body
Pupil
Cornea
Aqueous humor(fills the anteriorchamber)
Sclera
Lens
Vision Depends on the Eye
• The choroid, ciliary body, and iris make up the middle layer
• The middle layer is vascular
Vision Depends on the Eye
• The pupil – An opening in the center of the iris– Allows light to enter the eye and reach the
innermost layer, the retina, which contains • Photoreceptors• Rods • Cones
Vision Depends on the Eye
• The cones are concentrated in the center of the retina (fovea) for focused vision
Vision Depends on the Eye
• The optic nerve – Cranial nerve II– Carries visual information to the brain – Forms a blind spot where it leaves the retina
• An image that strikes the blind spot can not be seen
Vision Depends on the Eye
• The eyeball is divided into two fluid filled cavities– The posterior cavity• The main cavity of the eye• Contains vitreous humor, the jelly–like fluid
– The anterior cavity• The cavity in front of the eye between the cornea and
the lens • Contains aqueous humor, the watery fluid
Vision Depends on the Eye
• Glaucoma – Results when pressure of the aqueous humor
reaches dangerous levels due to underabsorption or over–secretion of the fluid
Vision Depends on the Eye
• Light is bent (refracted) at 4 points when it enters the eye– The cornea– The aqueous humor– The lens – The vitreous humor
Vision Depends on the Eye
• The ciliary muscle can change the shape of the lens, allowing the image to be focused on the retina
• The elasticity of the lens provides for the process of accommodation – The changing the shape of the lens to change the
bending of light
Vision Depends on the Eye
Figure 9.5
Vision Depends on the Eye
• A cataract – A lens that has become cloudy, usually due to
aging
Vision Depends on the Eye
• Depth perception and a focused image are accomplished by convergence– Keeps both eyes focused on the midline of an
object
Vision Depends on the Eye
• Farsightedness, nearsightedness, and astigmatism are the three most common visual problems and are due to refractive problems
• These refractive disorders may be caused by discrepancies in the lens or the shape of the eye
• Normal vision can be restored with corrective lenses
Vision Depends on the Eye
Table 9.2
Vision Depends on the Eye
Figure 9.6a
Vision Depends on the Eye
Figure 9.6b
Vision Depends on the Eye
Figure 9.6c
Vision Depends on the Eye
Figure 9.6d
Vision Depends on the Eye
• Rods and cones are the two types of photoreceptors
• All photoreceptors respond to light with a neural message sent to the brain
Vision Depends on the Eye
Figure 9.7
Vision Depends on the Eye
Figure 9.8a
(a) Light enters the left eye and strikes the retina.
Light
Retina
Choroid
Sclera
Blind spot
Vision Depends on the Eye
Figure 9.8b
(b) When light is focused on the retina, it passes through the ganglion cell layer and bipolar cell layer before reaching the rods and cones. In response to light, the rods and cones generate electrical signals that are sent to bipolar cells and then to ganglion cells. These cells begin the processing of visual information.
Ganglioncell layer
Bipolarcell layer
Retina
Photoreceptorcells
Pigment layer
Choroid
Sclera
Rod
Electricalsignals
Axons
Cone
Light
Vitreoushumor
Vision Depends on the Eye
Figure 9.8c
(c) The axons of the ganglion cells leave the eye at the blind spot, carrying nerve impulses to the brain (viewed from below) by means of the optic nerve.
Retina
Light
Optic nerve
Visual cortex
Vision Depends on the Eye
• Rods allow us to see in dim light, seeing black and white– They contain the pigment rhodopsin, which is
broken down in bright light– They are more numerous than cones
Vision Depends on the Eye
• Color vision depends on cones• Three types of cones—red, blue, and green—
allow us to see color • Produce sharp images• A reduced number or lack of one of the types
of cones results in color blindness
Vision Depends on the Eye
Figure 9.9
Vision Depends on the Eye
Figure 9.9 (1 of 2)
Rod cell
Cone cell
Disks containingvisual pigments
Nuclei
Synapticendings
Rods function in black-and-white vision.
Cones function in color vision.
Vision Depends on the Eye
Figure 9.9 (2 of 2)
Rod cell
Cone cell
Hearing Depends on the Ear
• In order to hear, the ear collects and amplifies sound waves – Converts them to neural messages
• The sound waves are produced by vibrations
Hearing Depends on the Ear
Figure 9.11a
Hearing Depends on the Ear
Figure 9.11b
Hearing Depends on the Ear
Figure 9.11c
Hearing Depends on the Ear
• Three divisions of the ear – Outer ear – The middle ear – The inner ear
Hearing Depends on the Ear
• Outer ear – The receiver• Consists of the pinna and external auditory canal• Receives the waves
• The middle ear – The amplifier
• The inner ear – The transmitter
Hearing Depends on the Ear
Figure 9.12 (1 of 2)
Outerear(receiver)
Middleear(amplifier)
Innerear(transmitter)
Hearing Depends on the Ear
Figure 9.12 (2 of 2)
The pinna gathers sound and funnels it into the external auditory canal to the tympanic membrane (eardrum).
The eardrum vibrates synchronously with sound waves, causing the bones of the middle ear to move.
The three bones of the middle ear amplify the pressure waves and convey the vibrations of the eardrum to the inner ear.
The cochlea converts pressure waves to neural messages that are sent to the brain for interpretation as sound.
Malleus(hammer)
Incus(anvil)
Stapes(stirrup)
Semicircular canals
Vestibular apparatus:
Auditory nerve
Cochlea
Oval window
Eardrum(tympanic membrane)
Round window
Auditory tube(Eustachiantube)
Outer ear(receiver)
Middle ear(amplifier)
Inner ear(transmitter)
External auditory canal
Vestibule
Hearing Depends on the Ear
Table 9.3 (1 of 2)
Hearing Depends on the Ear
Table 9.3 (2 of 2)
Hearing Depends on the Ear
• The tympanic membrane separates the outer ear from the middle ear
• The middle ear consists of an air-filled cavity within the temporal bone of the skull and the three auditory bones– Malleus– Incus – Stapes
Hearing Depends on the Ear
• The middle ear – Takes sound from the eardrum to the oval
window – Uses the malleus, incus, and stapes to amplify the
sound
Hearing Depends on the Ear
• The inner ear – A transmitter – Consists of the cochlea and vestibular apparatus • The spiral organ is most directly responsible for the
sense of hearing
Hearing Depends on the Ear
Figure 9.13 (1 of 2)
Hearing Depends on the Ear
Figure 9.13 (2 of 2)
Hair cell
Tectorialmembrane
Hearing Depends on the Ear
• Vibrations – Transmitted from the middle ear to the fluid
within the cochlea – Activate hair cells that stimulate the nerves that
carry the impulse to the brain– The more hair cells stimulated, the louder the
sound
Hearing Depends on the Ear
Figure 9.11a
Hearing Depends on the Ear
Figure 9.11b
Hearing Depends on the Ear
Figure 9.14
Spiral organ (of Corti)
Step 2: Movement of the oval window creates pressure waves in the cochlear fluid, causing the basilar membrane to vibrate.
Basilar membrane
Central compartment(cochlear duct)
Eardrum(tympanic
membrane)
Sound waves
Malleus(hammer)
Incus(anvil)
Stapes(stirrup)
CochleaUpper compartment (vestibular canal)
Lower compartment(tympanic canal)
Oval window
Roundwindow
Auditorytube
Step 1: Sound waves cause the eardrum to vibrate. These vibrations are transmitted through the bones of the middle ear to the oval window.
Tectorial membrane
Hair cell
Hearing Depends on the Ear
Figure 9.14 (1 of 2)
Hearing Depends on the Ear
Figure 9.14 (2 of 2)
Spiral organ (of Corti)
Step 3: When the basilar membrane vibrates, the hairlike projections on the hair cell receptors are pushed against the overhanging tectorial membrane, resulting in nerve impulses that are carried to the brain by the auditory nerve.
Basilar membrane
Central compartment(cochlear duct)
Upper compartment (vestibular canal)
Lower compartment(tympanic canal)
Tectorial membrane
Hair cell
Hearing Depends on the Ear
• Pitch is interpreted by the frequency of impulses in the auditory nerve
Figure 9.11c
Hearing Depends on the Ear
• There are two types of hearing loss– Conductive • Involves an obstruction along the route that sound
follows to the inner ear
– Sensorineural • Caused by damage to the hair cells or the nerve supply
of the inner ear
Balance Depends on the Vestibular Apparatus
• Balance – Depends on the vestibular apparatus of the inner
ear • A fluid-filled maze of chambers and canals within the
inner ear
Balance Depends on the Vestibular Apparatus
Figure 9.16
Semicircularcanals
Dynamic equilibrium
Cochlea
Cochlear duct
Bony labyrinthAmpulla
Utricle
Saccule
Balance Depends on the Vestibular Apparatus
Figure 9.16a (1 of 2)
Balance Depends on the Vestibular Apparatus
Figure 9.16a (2 of 2)
Balance Depends on the Vestibular Apparatus
Figure 9.16b (1 of 2)
Balance Depends on the Vestibular Apparatus
Figure 9.16b (2 of 2)
Balance
• The semicircular canals and the vestibule make up the vestibular apparatus
Balance
• The semicircular canals – Contain sensory receptors that monitor
movement
• The vestibule – Monitors balance when we are not moving
Smell and Taste Are the Chemical Senses
• Olfactory receptors – Neurons with long cilia covered by mucus– Located in the roof of the nasal cavity
• There are about 1000 types of olfactory receptors
Smell and Taste Are the Chemical Senses
Figure 9.17
Smell and Taste
• Odor molecules – Dissolve in the mucus and bind to the receptors • Causes a stimulation that is relayed to the olfactory
bulb in the brain
Smell and Taste
• Taste – Perceived by taste buds • Located on the tongue and inner surfaces of the mouth
Smell and Taste
Figure 9.18
Smell and Taste
Figure 9.18a–b
Smell and Taste
Figure 9.18b–c
Smell and Taste
Figure 9.18d
Smell and Taste
• Taste cells have taste hairs – They project into a pore at the tip of the taste bud
• When food molecules are dissolved in water, they enter the pore and stimulate the taste hairs
Smell and Taste
• Taste buds sense the five basic tastes– Sweet– Salty– Sour – Bitter – Umami