chapter11 - sense organs

Understanding Anatomy & PhysiologyUnderstanding Anatomy & PhysiologyA Visual, Interactive ApproachA Visual, Interactive Approach

Chapter 11

The Sense OrgansThe Sense Organs

Sensory receptorsSensory receptors Some combine with muscle and

tissue to form sense organs. Most consist of specialized nerve

cells or nerve endings.

Sensory receptors transmit information about:TypeType of stimulusLocationLocation of stimulusIntensityIntensity of stimulus

Classification of receptorsClassification of receptors ChemoreceptorsChemoreceptors MechanoreceptorsMechanoreceptors ThermoreceptorsThermoreceptors NociceptorsNociceptors PhotoreceptorsPhotoreceptors ProprioceptorsProprioceptors

Nociceptors respond to:

A.various chemicals inside and outside the body.B.pressure, stretch or vibration.C.pain from tissue damage.D.changes in temperature.

Correct answer: C

Rationale: Chemoreceptors react to chemicals; mechanoreceptors respond to factors that change the position of a receptor (such as pressure, stretch, or vibration); and thermoreceptors respond to changes in temperature.

General sensesGeneral senses Include pain, pressure, touch,

stretch, and temperature Involve receptors widely distributed

in skin, muscles, tendons, joints, and viscera

PainPain Nociceptors consist of free nerve

endings that carry impulses to the brain. Receptors are abundant in skin and

mucous membranes; found in almost every organ.

Nociceptors use fast and slow pain fibers.

Pain Pain pathwaypathway

View animation of pain pathway

Referred painReferred pain

The true source of pain can be difficult to identify because:

A.nociceptors can be stimulated by a variety of chemicals.B.deep body organs do not contain pain fibers.C.some pain signals travel to the thalamus, whereas others travel to the limbic system.D.sensory impulses from different areas often travel to the brain over the same pathway.

Correct answer: D

Rationale: The different chemicals released by injured receptors have nothing to do with identifying the source of pain. Deep body organs contain slow pain fibers. Pain signals that travel to the thalamus proceed to the postcentral gyrus, making the individual aware of pain; signals that travel to the limbic system trigger emotional responses to pain.

Special sensesSpecial senses Include taste, smell, hearing,

equilibrium, and vision Involve receptors grouped together

or clustered in specialized organs

TasteTaste

Vallate papillae

Foliate papillae

Filiform papillae

Fungiform papillae

Taste buds

Taste budsTaste buds

SmellSmell

HearingHearing

Auricle

Auditory canal

Middle earMiddle ear

Malleus

Stapes

Tympanic membrane

Eustachian tube

Inner earInner ear

Semicircular canals

Vestibule

Cochlea

Cochlear duct

Inner ear Inner ear (cont’d)(cont’d)

Basilar membrane

Organ of Corti

Which inner ear structure contains the structures for hearing?

A.VestibuleB.Semicircular canalsC.CochleaD.Auricle

Correct answer: C

Rationale:The vestibule contains organs necessary for the sense of balance. The semicircular canals are crucial for balance and equilibrium. The auricle (pinna) is the visible part of the external ear.

How hearing occursHow hearing occurs

View animation on how hearing occurs

BalanceBalanceSemicircular canals

AmpullaVestibule

Inside the ampullaInside the ampulla

Inside the vestibuleInside the vestibule

Dynamic equilibriumDynamic equilibrium

Static equilibriumStatic equilibrium

The utricle and saccule reside inside the:

A.vestibule.B.ampulla.C.organ of Corti.D.cochlea.

Correct answer: A

Rationale:The cupula resides in the ampulla. The cochlea contains the organ of Corti, the hearing sense organ.

VisionVision

Eyelashes

Conjunctiva

Eyebrow

Eyelids

Palpebral fissure

Lacrimal apparatusLacrimal apparatus

Lacrimal punctum

Lacrimal gland

Nasolacrimal duct

Extrinsic eye musclesExtrinsic eye muscles

Tissue layers of the eyeTissue layers of the eye

Sclera

Cornea

Ciliary body

Choroid

Retina

Optic nerve

RetinaRetina

Macula lutea

Fovea centralis

Optic disc

The outermost layer of the eye is the:

A.sclera.B.ciliary body.C.choroid.D.retina.

Correct answer: A

Rationale:The ciliary body and choroid are parts of the middle vascular layer. The retina is part of the inner neural layer.

Eye chambers and fluidsEye chambers and fluids

Anterior cavity

Posterior cavity

Process of visionProcess of vision

1. Light focuses on retina and produces upside-down image.

2. Rods and cone convert image to nerve impulses.

3. Impulses are transmitted to brain.

RefractionRefraction

ConvergenceConvergence

Constriction of the pupilConstriction of the pupil

Pupillary constrictor

Pupillary dilator

Accommodation of the lensAccommodation of the lens

Action of photoreceptorsAction of photoreceptors

RodsRods

Concentrated at the periphery of the retina

Active in dim light Responsible for night

vision Cannot distinguish

colors from each other

ConesCones

Concentrated in the center of the retina

Active in bright light Responsible for sharp

vision Responsible for color

vision

Transmission of impulsesTransmission of impulses

The bending of light rays so they focus precisely on the retina is called:

A.convergence.B.accommodation.C.constriction.D.refraction.

Correct answer: D

Rationale:Convergence lines up the visual axis of each eye. Accommodation occurs when the lens changes its curvature. Constriction occurs when the pupil narrows to restrict light entering the eye.

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