HUMAN PHYSIOLOGY Sensory Physiology equilibrium vision Copyright 2004
HUMAN PHYSIOLOGY Sensory Physiology equilibrium & vision Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Equilibrium: Mechanoreceptor • Body balance • Body position • Body movement • Propioceptors • Vision • Vestibular apparatus Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Organs of Equilibrium · Receptor cells are in two structures · Vestibule · Semicircular canals Figure 8. 16 a, b Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Organs of Equilibrium · Equilibrium has two functional parts · Static equilibrium – sense of gravity at rest · Dynamic equilibrium – angular and rotary head movements Figure 8. 16 a, b Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
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 © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Function of Maculae Figure 8. 15 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Dynamic Equilibrium - Movement · receptors in the semicircular canals · Tuft of hair cells · Cupula (gelatinous cap) covers the hair cells Figure 8. 16 c Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
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. 16 c Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Equilibrium: Mechanoreceptor • Integration • Medulla • Cerebellum • Thalamus • Cortex Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings 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 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 10 -23 a, b: ANATOMY SUMMARY: Vestibular Apparatus
Equilibrium: Vestibular Apparatus Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 10 -23 c, d: ANATOMY SUMMARY: Vestibular Apparatus
The Eye and Vision · 70 percent of all sensory receptors are in the eyes, only see 1/6 th 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 © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Accessory Structures of the Eye · Eyelids · Eyelashes Figure 8. 1 b Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Accessory Structures of the Eye · Eyelashes =have modified sebacious glands produce an oily secretion to lubricate the eye Figure 8. 1 b Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Accessory Structures of the Eye · Conjunctiva · Membrane that lines the eyelids · Connects to the surface of the eye · Secretes mucus to lubricate the eye Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Accessory Structures of the Eye · Lacrimal gland · Tears: antibodies, lysozymes, stress? Figure 8. 1 a Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Extrinsic Eye Muscles · Muscles attach to the outer surface of the eye · Produce eye movements Figure 8. 2 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
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. 3 a Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
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 © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
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 © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Sensory layer (Retina) · Contains receptor cells (photoreceptors) · Rods · Cones · Signals pass from photoreceptors and leave the retina toward the brain through the optic nerve Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Neurons of the Retina Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings 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 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
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 © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Lens · Biconvex crystal-like structure · Held in place by a suspensory ligament attached to the ciliary body Figure 8. 3 a Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
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
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 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
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 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8. 9
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. Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Correct focus Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
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 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 10 -36: Photoreceptors in the fovea
Photoreception and Local Integration • Rods – night vision • Cones – color & details • Bipolar & ganglion cells converge, integrate APs Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Photoreception and Local Integration Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings 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 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Retina: More Detail Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 10 -38: Photoreceptors: rods and cones
Phototransduction • Photons "bleach" opsin, retinal released, cascade, Na+ channel closes, K+ opens , hyperpolarization • Reduces NT release Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Phototransduction Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings 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 -29 b, 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
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