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

A) Parasympathetic impulses were increased. 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 Step 1: A sensory receptor detects the stimulus from the external or internal environment. Stimulus Sensory receptor Step 2: Sensory neurons conduct a nerve impulse to the spinal cord and then to the brain, or directly to the brain. Nerve impulse carried by sensory nerves Step 3: The brain interprets the information from the sensory receptor. Spinal cord Brain Step 4: The brain’s interpretation of the information is a perception or understanding of the stimulus. Figure 9.1

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 Lungs and diaphragm Heart Stomach Liver and gallbladder Small intestine Appendix Colon Urinary bladder Ureter Testes Kidney Figure 9.3

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 Optic nerve Optic disk (blind spot) Fovea Sclera Choroid Retina Vitreous humor (fills the posterior chamber) Lens Ciliary body Aqueous humor (fills the anterior chamber) Cornea Pupil Iris Sclera Figure 9.4

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 Light Choroid Sclera Retina Blind spot (a) Light enters the left eye and strikes the retina. Figure 9.8a

Vision Depends on the Eye Light Vitreous humor Ganglion cell layer Electrical signals Bipolar cell layer Retina Cone Photoreceptor cells Rod Pigment layer Axons Choroid Sclera (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. Figure 9.8b

Vision Depends on the Eye Light Retina Optic nerve Visual cortex (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. Figure 9.8c

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 Cones function in color vision. Rods function in black-and-white vision. Disks containing visual pigments Rod cell Cone cell Nuclei Synaptic endings Figure 9.9 (1 of 2)

Vision Depends on the Eye Rod cell Cone cell Figure 9.9 (2 of 2)

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 Outer ear (receiver) Middle ear (amplifier) Inner ear (transmitter) Figure 9.12 (1 of 2)

Hearing Depends on the Ear Outer ear (receiver) Middle ear (amplifier) Inner ear (transmitter) Eardrum (tympanic membrane) Malleus (hammer) Incus (anvil) Stapes (stirrup) Vestibular apparatus: Semicircular canals Vestibule Auditory nerve Oval window Cochlea Round window External auditory canal Auditory tube (Eustachian tube) 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. Figure 9.12 (2 of 2)

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 Tectorial membrane Hair cell Figure 9.13 (2 of 2)

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

Hearing Depends on the Ear Round window Upper compartment (vestibular canal) Cochlea Oval window Central compartment (cochlear duct) Stapes (stirrup) Incus (anvil) Malleus (hammer) Spiral organ (of Corti) Eardrum (tympanic membrane) Tectorial membrane Hair cell Sound waves Basilar membrane Step 1: Sound waves cause the eardrum to vibrate. These vibrations are transmitted through the bones of the middle ear to the oval window. Lower compartment (tympanic canal) Step 2: Movement of the oval window creates pressure waves in the cochlear fluid, causing the basilar membrane to vibrate. Auditory tube Figure 9.14 (1 of 2)

Hearing Depends on the Ear Upper compartment (vestibular canal) Central compartment (cochlear duct) Spiral organ (of Corti) Tectorial membrane Hair cell Basilar membrane Lower compartment (tympanic canal) 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. Figure 9.14 (2 of 2)

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 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 Dynamic equilibrium Bony labyrinth Ampulla Utricle Saccule Semicircular canals Cochlea Cochlear duct Figure 9.16

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 The vestibule 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