Essentials of Anatomy & Physiology, 4th Edition Martini ... · The Lacrimal Apparatus • Lacrimal...

Essentials of Anatomy & Physiology, 4th EditionMartini / Bartholomew

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The General and

Special Senses

The General and

Special Senses99

Slides 1 to 106

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

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The General Senses

Sensory Basics

• Sensory receptors—Specialized cells or cell processes that monitor external or internal conditions. Simplest are free nerve endings.




The General Senses

More Sensory Basics

• Receptive field—The area monitored

by a single receptor cell

• Adaptation—Reduction in sensitivity

at a receptor or along a sensory

pathway in the presence of a

constant stimulus.




The General Senses

General versus Special Senses

• General senses—Temperature, pain, touch, pressure, vibration, and proprioception. Receptors throughout the body

• Special senses—Smell, taste, vision, balance, and hearing. Receptors located in sense organs (e.g., ear, eye).




The General Senses

Receptors and Receptive Fields

Figure 9-1



Key Note

Stimulation of a receptor produces

action potentials that propagate along the axon of a sensory neuron. The

frequency or pattern of action potentials contains information about the stimulus.

A person’s perception of the nature of

that stimulus depends on the path it takes inside the CNS.


The General Senses



The General Senses

Pain Definitions

• Nociceptors—Receptors for tissue damage to lead to the sensation of pain

• Referred pain—Perception of pain in a part of the body not actually stimulated

• Fast (prickling) pain—Localized pain carried quickly to the CNS on myelinated axons

• Slow (burning) pain—Generalized pain carried on slow unmyelinated axons




The General Senses

Referred Pain

Figure 9-2



The General Senses

Temperature

• Thermoreceptors detect temperature change

• Free nerve endings

• Found in dermis, skeletal muscle, liver,

hypothalamus

• Fast adapting

• Cold receptors greatly outnumber warm

receptors




The General Senses

Touch, Pressure, and Position

• Mechanoreceptors—Receptors that respond to physical distortion of their cell membranes.

• Tactile receptors—Sense touch, pressure, or

vibration

• Baroreceptors—Sense pressure changes in

walls of blood vessels, digestive organs,

bladder, lungs

• Proprioceptors—Respond to positions of

joints and muscle




The General Senses

Tactile Receptors

• Fine touch or pressure receptors

• Highly detailed information about a stimulus

• Crude touch or pressure receptors

• Poorly localized information about a

stimulus

• Important types: root hair plexus, tactile disks, tactile corpuscles, lamellated corpuscles, Ruffini corpuscles




The General Senses

Tactile Receptors in the Skin

Figure 9-3



The General Senses

Baroreceptors

• Provide pressure information essential for autonomic regulation

• Arterial blood pressure

• Lung inflation

• Digestive coordination

• Bladder fullness




The General Senses

Baroreceptors and the Regulation of Autonomic Functions

Figure 9-4



The General Senses

Proprioceptors

• Monitor joint angle, tension in tendons and ligaments, state of muscular contraction

• Include:

• Muscle spindles

• Golgi tendon organs




The General Senses

Chemical Detection

• Chemoreceptors respond to chemicals dissolved in body fluids that surround them and monitor the chemical composition of blood and tissues

• Chemicals that can be sensed include:

• Carbon dioxide

• Oxygen

• Hydrogen ion




The General Senses

Locations and Functions of Chemoreceptors

Figure 9-5



The Special Senses—Smell

Olfactory Organs

• Olfactory epithelium

• Olfactory receptor cells

• Neurons sensitive to odorants

• Supporting cells

• Basal (stem) cells

• Olfactory glands

• Mucus-secreting cells





Figure 9-6(a)

The Olfactory Organs




The Olfactory Organs

Figure 9-6(b)




The Olfactory Pathways

• Axons from olfactory receptors penetrate cribriform plate of ethmoid

bone

• Synapse in olfactory bulb

• Olfactory tract projects to:

• Olfactory cerebral cortex

• Hypothalamus

• Limbic System




The Special Senses—Taste

Taste (Gustatory) Receptors

• Taste buds

• Found within papillae on tongue,

pharynx, larynx

• Contain gustatory cells, supportive

cells

• Taste hairs (cilia) extend into taste

pores

• Sense salt, sweet, sour, bitter

• Also sense umami, water

• Synapse in medulla oblongata





Gustatory Receptors

Figure 9-7(a)




Figure 9-7(b)

Gustatory Receptors




Gustatory Receptors

Figure 9-7(c)



The Special Senses

Key Note

Olfactory information is routed directly

to the cerebrum, and olfactory stimuli have powerful effects on mood and

behavior. Gustatory sensations are strongest and clearest when integrated

with olfactory sensations.




The Special Senses—Vision

Accessory Structures of the Eye

• Eyelids (palpebra) and glands

• Superficial epithelium of eye

• Conjunctiva

• Lacrimal apparatus

• Tear production and removal

• Extrinsic eye muscles





The Lacrimal Apparatus

• Lacrimal gland produce tears

• Bathe conjunctiva

• Contain lysozyme to attack bacteria

• Tears drain into nasal cavity

• Pass through lacrimal canals,

lacrimal sac, nasolacrimal duct





Figure 9-8(a)

The Accessory

Structures

of the Eye




The Accessory Structures of the Eye

Figure 9-8(b)




Extrinsic Eye Muscles

• Move the eye

• Six muscles cooperate to control gaze

• Superior and inferior rectus

• Lateral and medial rectus

• Superior and inferior oblique





Figure 9-9(a)

The Extrinsic Eye Muscles




Figure 9-9(b)

The Extrinsic Eye Muscles




Layers of the Eye

• Fibrous tunic

• Outermost layer

• Vascular tunic

• Intermediate layer

• Neural tunic

• Innermost layer





Figure 9-10(a)

The Sectional Anatomy of the

Eye




Figure 9-10(b)

The Sectional Anatomy of the Eye




The Sectional Anatomy of the Eye

Figure 9-10 (c)




Layers of the Eye

• Fibrous tunic

• Sclera

• Dense fibrous connective

tissue

• “White of the eye”

• Cornea

• Transparent

• Light entrance

The Eye: Light Path


PLAY




Layers of the Eye

• Vascular tunic

• Iris

• Boundary between anterior and

posterior chambers

• Ciliary body

• Ciliary muscle and ciliary process

• Attachment of suspensory ligaments

• Choroid

• Highly vascular





Functions of the Vascular Tunic

• Provide a route for blood vessels

• Control amount of light entering eye

• Adjust diameter of pupil

• Secrete and absorb aqueous humor

• Adjust lens shape for focusing





The Pupillary Muscles

Figure 9-11




Layers of the Eye

• Neural tunic (Retina)

• Outer pigmented part

• Absorbs stray light

• Inner neural part

• Detects light

• Processes image

• Communicates with brain





Organization of the Retina

• Photoreceptor layer

• Bipolar cells

• Amacrine, horizontal cells

modify signals

• Ganglion cells

• Optic nerve (CN II)





Retinal Organization

Figure 9-12(a)




Figure 9-12(b)





Figure 9-12(c)





Chambers of the Eye

• Two cavities

• Ciliary body, lens between the two

• Anterior cavity

• Anterior compartment

Between cornea and iris

• Posterior compartment

Between iris and lens

• Posterior cavity

• Vitreous body





The Aqueous Humor

• Secreted by ciliary processes into posterior chamber

• Flows into anterior chamber

• Maintains eye shape

• Carries nutrients and wastes

• Reabsorbed into circulation

• Leaves at canal of Schlemm

• Excess humor leads to glaucoma





Figure 9-14

Eye Chambers and the Circulation of Aqueous Humor




The Lens

• Supported by suspensory ligaments

• Built from transparent cells

• Surrounded by elastic capsule

• Lens and cornea focus light on retina

• Bend light (refraction)

• Accommodation changes lens shape





Figure 9-15(a)

Focal Point, Focal Distance,

and Visual

Accommodation




Focal Point, Focal Distance,

and Visual

Accommodation

Figure 9-15(b)




Figure 9-15(c)

Focal Point, Focal Distance, and Visual

Accommodation




Figure 9-15(d)


Accommodation




Figure 9-15(e)


Accommodation




Figure 9-16(a)

Image Formation




Figure 9-16(b)

Image Formation




Figure 9-17(a)

Visual Abnormalities




Figure 9-17(b)





Figure 9-17(c)





Figure 9-17(d)





Figure 9-17(e)





Key Note

Light passes through the cornea, crosses the anterior cavity to the lens, transits the lens, crosses the posterior chamber, and then penetrates the retina to stimulate the photoreceptors. Cones, most abundant at the fovea and macula lutea, provide detailed color vision in bright light. Rods, dominant in the peripheral retina, provide coarse color-free vision in dim light.





Visual Physiology

• Photoreceptors—Cells specialized to respond to photons, packets of light energy

• Two types of photoreceptors

• Rods

• Highly sensitive, non-color vision

• In peripheral retina

• Cones

• Less sensitive, color vision

• Mostly in fovea, center of macula lutea

Site of sharpest vision





Photoreceptor Anatomy

• Outer segment

• Discs with visual pigments

• Light absorption by rhodopsin

• Opsin + retinal

• Inner segment

• Synapse with bipolar cell

• Control of neurotransmitter release

• Effect on bipolar cells





The Structure of Rods and Cones

Figure 9-19




Figure 9-201 of 7

Retinal andopsin are

reassembledto form

rhodopsin

Photon

Retinal changes shape

Bleaching(separation)enzyme

ADP ATP

Opsin Opsin

Opsininactivated

Regeneration

Retinalrestored




Figure 9-202 of 7


reassembledto form

rhodopsin




Figure 9-203 of 7


reassembledto form

rhodopsin

Photon




Figure 9-204 of 7


reassembledto form

rhodopsin

Photon





Figure 9-205 of 7


reassembledto form

rhodopsin

Photon



ADP ATP

Retinalrestored




Figure 9-206 of 7


reassembledto form

rhodopsin

Photon



ADP ATP

Opsin Opsin

Opsininactivated

Retinalrestored




Figure 9-207 of 7


reassembledto form

rhodopsin

Photon


Regeneration


ADP ATP

Retinalrestored

Opsin Opsin

Opsininactivated




The Visual Pathway

• Ganglion cells axon converge at optic disc

• Axons leave as optic nerve (CN II)

• Some axons cross at optic chiasm

• Synapse in thalamus bilaterally

• Thalamic neurons project to visual cortex

• Located in occipital lobes

• Contains map of visual field





Figure 9-21

The Visual Pathway



Equilibrium and Hearing

Sensory Functions of the Inner Ear

• Dynamic equilibrium

• Static equilibrium

• Hearing





Overview of the Ear

• Chambers, canals filled with fluid endolymph

• Bony labyrinth

• Surrounds membranous labyrinth

• Surrounded by fluid perilymph

• Consists of vestibule, semicircular canals,

cochlea

• External, middle ear feed sound to cochlea





Anatomy of the Ear

• External ear

• Pinna (auricle)

• External acoustic canal

• Tympanic membrane (eardrum)

• Middle ear

• Auditory ossicles

• Connect tympanic membrane to inner ear

• Auditory tube

• Connection to nasopharynx





Anatomy of the Inner Ear

• Vestibule

• Membranous sacs

• Utricle

• Saccule

• Receptors for linear acceleration, gravity

• Semicircular canal with ducts

• Receptors for rotation

• Cochlea with cochlear duct

• Receptors for sound





Receptors of the Inner Ear

• Hair cells

• Mechanoreceptors

• Stereocilia on cell surface

• Bending excites/inhibits hair cell

• Information on direction and strength

of mechanical stimuli





The Anatomy of the Ear

Figure 9-22




The Structure of the Middle Ear

Figure 9-23




Figure 9-24(a,b)





Figure 9-24(c)


The Ear: Ear AnatomyPLAY




Equilibrium

• Semicircular ducts

• Connect to utricle

• Contains ampulla with hair cells

• Stereocilia contact cupola

• Gelatinous mass distorted by fluid

movement

• Detects rotation of head in three planes

• Anterior, posterior, lateral ducts





Equilibrium (continued)

• Saccule and utricle

• Hair cells cluster in maculae

• Stereocilia contact otoliths

(heavy mineral crystals)

• Gravity pulls otoliths

• Detect tilt of head

• Sensory axons in vestibular

branch of CN VIII





The Vestibular Complex

Figure 9-25(a-c)




The Vestibular Complex

Figure 9-25(a, d)




Figure 9-25(e)1 of 4

Gravity

Gravity

Head in horizontal position

Head tilted posteriorly

Receptoroutput increases

Otolith moves

“downhill,”distorting

hair cell processes





Gravity






Gravity

Gravity



Otolith moves


hair cell processes





Gravity

Gravity



Receptoroutput increases

Otolith moves


hair cell processes

The Ear: BalancePLAY




Overview of Hearing

• Sound waves vibrate tympanic membrane

• Ossicles transfer vibration to oval window

• Oval window presses on perilymph in vestibular duct

• Pressure wave distorts basilar membrane

• Hair cells of organ of Corti press on tectorial membrane





The Cochlea and the Organ of Corti

Figure 9-26(a)




Figure 9-26(b)

The Cochlea and the Organ of Corti




Figure 9-271 of 7

Externalacoustic

canal

Movementof sound

waves

Malleus

Incus

Stapes

Ovalwindow

Cochlear branch ofcranial nerve VIII

Vestibular duct(perilymph)

Vestibular membrane

Cochlear duct(endolymph)Basilar membrane

Tympanic duct(perilymph)

Tympanicmembrane

Roundwindow

Sound waves arrive at tympanic membrane.

Movement of tympanic membrane causes displacement of the auditory ossicles.

Movement of the stapes at the oval window establishes pressure waves in the perilymph of the vestibular duct.

The pressure waves distort the basilar membrane on their way to the round window of the tympanic duct.

Vibrations of the basilar membrane causes vibration of hair cells against the tectorial membrane.

Information about the region and the intensity of stimulation is relayed to the CNS over the cochlear branch of cranial nerve VIII.




Figure 9-272 of 7

Externalacoustic

canal

Movementof sound

waves


Tympanicmembrane




Figure 9-273 of 7

Externalacoustic

canal

Movementof sound

waves

Malleus

Incus

Stapes

Tympanicmembrane






Figure 9-274 of 7

Externalacoustic

canal

Movementof sound

waves

Malleus

Incus

Stapes

Ovalwindow

Tympanicmembrane







Figure 9-275 of 7

Externalacoustic

canal

Movementof sound

waves

Malleus

Incus

Stapes

Ovalwindow

Tympanicmembrane

Roundwindow








Figure 9-276 of 7

Externalacoustic

canal

Movementof sound

waves

Malleus

Incus

Stapes

Ovalwindow


Vestibular membrane



Tympanicmembrane

Roundwindow








The Ear: Receptor ComplexesCopyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

PLAYFigure 9-277 of 7

Externalacoustic

canal

Movementof sound

waves

Malleus

Incus

Stapes

Ovalwindow

Cochlear branch ofcranial nerve VIII


Vestibular membrane



Tympanicmembrane

Roundwindow






Information about the region and the intensity of stimulation is relayed to the CNS over the cochlear branch of cranial nerve VIII.




Auditory Pathways

• Hair cells excite sensory neurons

• Sensory neurons located in spiral ganglion

• Afferent axons form cochlear branch of vestibulocochlear nerve (CN VIII)

• Synapses in cochlear nucleus in medulla

• Neurons relay to midbrain

• Midbrain relays to thalamus

• Thalamus relays to auditory cortex (temporal lobe) in a frequency map





Pathways for Auditory

Sensations

Figure 9-28




Key Note

Balance and hearing both rely on hair cells. Which stimulus excites a particular group depends on the structure of the associated sense organ. In the semicircular ducts, fluid movement due to head rotation is sensed. In the utricle and saccule, shifts in the position of otoliths by gravity is sensed. In the cochlea, sound pressure waves distort the basilar membrane.




Aging and the Senses

Impact of Aging on Sensory Ability

• Gradual reduction in smell and taste sensitivity as receptors are lost

• Lens changes lead to presbyopia

(loss of near vision)

• Chance of cataract increases

• Progressive loss of hearing sensitivity as receptors are lost (presbycusis)




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