AL_sensory_physiology_3

THIRD EDITION

HUMAN PHYSIOLOGY AN INTEGRATED APPROACH Dee Unglaub Silverthorn, Ph.D.

Chapter 10, part C Sensory Physiology

PowerPoint® Lecture Slide Presentation by Dr. Howard D. Booth, Professor of Biology, Eastern Michigan University Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Equilibrium: Mechanoreceptor

• Body balance

• Body position • Body movement • Propioceptors

• Vision • Vestibular apparatus

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Organs of Equilibrium

 Receptor cells are in two structures  Vestibule  Semicircular canals

Figure 8.16a, b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

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Organs of Equilibrium

 Equilibrium has two functional parts  Static equilibrium – sense of gravity at rest  Dynamic equilibrium – angular and rotary head movements

Figure 8.16a, b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

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Static Equilibrium - Rest

 Maculae – receptors in the vestibule  Report on the position of the head  Send information via the vestibular nerve

 Anatomy of the maculae  Hair cells are embedded in the otolithic membrane  Otoliths (tiny stones) float in a gel around the hair cells  Movements cause otoliths to bend the hair cells Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Slide 8.31

Function of Maculae

Figure 8.15 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Slide 8.32

Dynamic Equilibrium - Movement

 Crista ampullaris – receptors in the semicircular canals  Tuft of hair cells  Cupula (gelatinous cap) covers the hair cells Figure 8.16c

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Dynamic Equilibrium

 Action of angular head movements  The cupula stimulates the hair cells  An impulse is sent via the vestibular nerve to the cerebellum Figure 8.16c

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Equilibrium: Mechanoreceptor • Integration • Medulla • Cerebellum • Thalamus • Cortex

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Figure 10-26: Central nervous system pathways for equilibrium

Equilibrium: Vestibular Apparatus • Otolith organs • Gravity • Calcite crystals • Hair cells • Semicircular canals

• Fluid moves • Cristae • Cupula • Hair cells Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Equilibrium: Vestibular Apparatus

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Figure 10-23a, b: ANATOMY SUMMARY: Vestibular Apparatus

Equilibrium: Vestibular Apparatus

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Figure 10-23c, d: ANATOMY SUMMARY: Vestibular Apparatus

The Eye and Vision

 70 percent of all sensory receptors are in the eyes, only see 1/6th of eye

 Each eye has over a million nerve fibers  Protection for the eye  Most of the eye is enclosed in a bony orbit  A cushion of fat surrounds most of the eye Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Slide 8.2

Accessory Structures of the Eye

 Eyelids  Eyelashes

Figure 8.1b

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Slide 8.3a

Accessory Structures of the Eye

 Eyelashes =have modified sebacious glands produce an oily secretion to lubricate the eye Figure 8.1b

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Slide 8.3b

Accessory Structures of the Eye

 Conjunctiva  Membrane that lines the eyelids  Connects to the surface of the eye  Secretes mucus to lubricate the eye

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Slide 8.4a

Accessory Structures of the Eye

 Lacrimal gland

Tears: antibodies, lysozymes, stress?

Figure 8.1a

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Slide 8.4b

Extrinsic Eye Muscles

 Muscles attach to the outer surface of the eye  Produce eye movements

Figure 8.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Slide 8.6

Structure of the Eye

 The wall is composed of three layers  Sclera&Cornea fibrous outside layer  Choroid – middle layer  Sensory (retina) inside layer Figure 8.3a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Slide 8.7

The Fibrous layer

 Sclera  White connective tissue layer  Seen anteriorly as the “white of the eye”

 Cornea  Transparent, central anterior portion  Allows for light to pass through

 Repairs itself easily  The only human tissue that can be transplanted without fear of rejection Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Slide 8.8

Choroid Layer

 Blood-rich nutritive layer  Pigment prevents light from scattering  Modified interiorly into two structures  Cilliary body – smooth muscle  Iris

 Pigmented layer that gives eye color  Pupil – rounded opening in the iris Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Slide 8.9

Sensory layer (Retina)

 Contains receptor cells (photoreceptors)  Rods  Cones

 Signals pass from photoreceptors and leave the retina toward the brain through the optic nerve

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Slide 8.10

Neurons of the Retina

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Slide 8.11

Neurons of the Retina and Vision

 Rods  Most are found towards the edges of the retina  Allow dim light vision and peripheral vision  Perception is all in gray tones

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Slide

Neurons of the Retina and Vision

 Cones – 3 types detect different colors  Most dense at the center of the retina

 Fovea centralis – area of the retina with only cones  Lack of one type = color blindness

 No photoreceptor cells are at the optic disk, or blind spot Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Slide

Lens

 Biconvex crystal-like structure

 Held in place by a suspensory ligament attached to the ciliary body

Figure 8.3a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Slide 8.14

Internal Eye Chamber Fluids

 Aqueous humor in Anterior Segment  Watery fluid found in chamber between the lens and cornea  Similar to blood plasma  Helps maintain intraocular pressure

 Provides nutrients for the lens and cornea  Reabsorbed into venous blood  Blocked drainage = glaucoma Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Slide

Internal Eye Chamber Fluids

 Vitreous humor in Posterior Segment  Gel-like substance behind the lens

 Keeps the eye from collapsing  Lasts a lifetime and is not replaced

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Slide

Lens Accommodation

 Light must be focused to a point on the retina for optimal vision  The eye is set for distance vision (over 20 ft away)  The lens must change shape to focus for closer objects Figure 8.9 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Slide 8.16

Correcting the Eye • Nearsightedness = myopia • Focus of light in front of retina • Eyeball too long or lens too thick • Distant objects are blurry

• Farsightedness = hyperopia • Focus of light beyond the retina • Short eyeball or lens too thin

• Near objects are blurry.

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Correct focus Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

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Hyperopia Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

• Unequal curvatures in cornea & lens

Astigmatism Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Vision: Photoreceptors • Reflected light translated into mental image • Pupil limits light, lens focuses light • Retinal rods and cones are photoreceptors

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Figure 10-36: Photoreceptors in the fovea

Photoreception and Local Integration

• Rods – night vision • Cones – color & details

• Bipolar & ganglion cells converge, integrate APs

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Photoreception and Local Integration

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Figure 10-35: ANATOMY SUMMARY: The Retina

Retina: More Detail

• Rod cells: monochromatic

• Cone cells: red, green, & blue • Discs: visual pigments • Pigmented epithelium

• Melanin granules • Prevents reflection

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Retina: More Detail

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Figure 10-38: Photoreceptors: rods and cones

Phototransduction

• Photons "bleach" opsin, retinal released, cascade, Na+ channel closes, K+ opens , hyperpolarization

• Reduces NT release

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Phototransduction

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Figure 10-40: Phototransduction in rods

Vision: Integration of Signals to Perception • Bipolar • Ganglion • Movement • Color • Optic nerve

• Optic chiasm • Optic tract • Thalamus • Visual cortex Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 10-29b, c: Neural pathways for vision and the papillary reflex

Summary • Sensory pathway: receptor, sensory neuron(s) & CNS • Somatic senses: touch, temperature, pain & proprioception communicate body information to CNS • Special senses: taste, smell, hearing, equilibrium, & vision • Outside conditions for CNS integration into perception • Receptors transduce mechanical, chemical or photon energy into GPs then to APs Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings