GENERAL REFLEX ARC. Sense Organs. Lecture Overview. Senses. Melissa Gonzales McNeal 1

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1 Nervous System Central Nervous System Peripheral Nervous System Sense Organs One definition of man is an intelligence served by organs Ralph Waldo Emerson Brain Spinal Cord Cranial Nerves Anatomical Classification Spinal Nerves Afferent touch, pressure vibration, temp pain, proprioception Somatic Nervous System Efferent skeletal muscles Functional Classification Afferent visceral receptors Autonomic Nervous System Efferent smooth muscle cardiac muscle glands 1 Sympathetic Parsympathetic 2 Overview of Sensation Sensation Definitions Characteristics Pathway components Sensory receptors Locations Modality Distribution General Senses Modalities Nociceptors Thermoreceptors Mechanoreceptors Chemoreceptors Structural classes Specific examples Special Senses Vision Hearing and Equilibrium Gustation Olfaction Lecture Overview 3 Sensory neuron Sensory receptor Integrating Center (gray matter of CNS) GENERAL REFLEX ARC Effector Organ Skeletal muscle Smooth muscle Cardiac muscle Gland Motor Neuron 4 Melissa Gonzales McNeal 1

2 Sensation Sensation: the conscious or subconscious awareness of external or internal stimuli Perception: the conscious awareness and the interpretation of meaning of senses 5 Characteristics of Sensation Projection: sensation seems to come from area where receptors were stimulated Phantom pain Referred pain: pain sensation projected down the same pathway, but not to the correct area Intensity: some sensations are felt more distinctly and to a greater degree After-image: the sensation remains in the consciousness even after the stimulus is stopped Adaptation: becoming unaware of a continuing stimulus (peripheral and general) Contrast: the effect of a previous or simultaneous sensation on the current sensation 6 Sensory neuron Integrating Center (gray matter of CNS) Cerebral Cortex => for perception Sensory receptor Sensory Pathway Remember Sensory Pathways First order neurons: conduct impulses from somatic receptors into the spinal cord and brain stem Second order neurons: conduct impulses from the spinal cord and brain stem to the thalamus Third order neurons: conduct impulses from thalamus to the cerebral cortex 7 8 Melissa Gonzales McNeal 2

3 Components of Sensation Stimulation: change in environment capable of initiating a nerve impulse Transduction: change in receptor s transmembrane potential Receptor potential: graded potential Generator potential: a receptor potential large enough to generate an action potential Conduction: movement of impulse along neuronal pathway Interpretation: translation of impulse into sensation (grey matter) 9 Sensory neuron Integrating Center (gray matter of CNS) Cerebral Cortex => for perception Sensory receptor Sensory Pathway 10 Receptors Receptors - detect changes (stimuli) and generate impulses Receptor versus Sense Organ Tonic receptors: always active Phasic receptors: normally inactive Classification Location or origin of stimulus Modality: type of stimulus Complexity 11 Receptor Classes Location or origin of stimulus Exteroceptors: located at or near the external surface of the body Vision, hearing, touch Interoceptors: located in blood vessels, visceral organs, muscles, and the nervous system Proprioceptors: located in muscles, tendons, joints, and the inner ear 12 Melissa Gonzales McNeal 3

4 Receptor Classes Modality: type of stimulus Nociceptors pain Thermoreceptors temperature Mechanoreceptors physical distortion Chemoreceptors chemical concentration Photoreceptors light 13 Which receptors will the following organs use? Eyes Stomach Taste buds 14 Receptor Classes Complexity General senses (somatosensory, somesthetic senses) Receptors are relatively simple in structure Special senses Relatively complex sense organs Vision Hearing Taste Smell 15 GENERAL SENSES 16 Melissa Gonzales McNeal 4

5 Nociceptors Fast pain (first) Modality Myelinated type A fibers Injections, deep cuts Often triggers somatic reflexes Slow pain (second) Type C fibers Burning, aching pain Information travels through reticular formation and thalamus Tonic receptors No peripheral adaptation General adaptation in perception of pain Endogenous opioids Purpose: awareness, activation of reactions to promote healing Modality Thermoreceptors Free nerve endings Heat sensitive ( degrees F) Cold sensitive ( degrees F) Location Dermis Skeletal muscles Liver Hypothalamus Phasic receptors Adapt quickly Travel on same pathways as pain sensation 19 Modality Mechanoreceptors Mechanically regulated ion channels Classes Tactile receptors: touch, pressure and vibration Fine touch and pressure Crude touch and pressure Tickle and itch Phasic receptors Baroreceptors/stretch receptors: pressure changes Phasic receptors - Adapt rapidly Proprioreceptors: position of joints and muscles Tonic receptors No adaptation 20 Melissa Gonzales McNeal 5

6 Modality Chemoreceptors Specialized neurons Only respond to dissolved substances water soluble lipid soluble Peripheral and general adaptation 21 Corpuscles of touch Meissner s corpuscles, tactile corpuscles Root hair plexuses hair follicle receptors, hair receptors, peritrichial endings Lamellated corpuscles Pacinian corpuscles, lamellar corpuscles Type I cutaneous mechanoreceptors Merkel discs, tactile discs Type II cutaneous mechanoreceptors Ruffini s corpuscles, bulbous corpuscles Muscle spindles Golgi tendon organs Warm receptors Cold receptors nociceptors Specific Examples of Sensory Receptors 22 Type I cutaneous mechanoreceptor or Merkel disc Touch and pressure Corpuscle of touch or Meissner s Corpuscle Changes in texture Type II cuteneous mechanoreceptor or Ruffini s Corpuscle Root Stretching hair plexus of digits and limbs Position change of hairs Lamellated corpuscle or Pacinian corpuscle vibration and pressure Muscle Spindle Golgi Tendon Organ Melissa Gonzales McNeal 6

7 Can you identify the specific receptors (A-B)? A For every beauty there is an eye somewhere to see it. For every truth there is an ear somewhere to hear it. For every love there is a heart somewhere to receive it. Ivan Panin (Russian mathematician ) B THE SPECIAL SENSES VISION 27 External Anatomy Eyelids (palpebrae) Conjunctiva Lacrimal apparatus Lacrimal glands Lacrimal canals (Lacrimal canaliculi) Lacrimal sac Nasolacrimal duct Lacrimal secretions (tears) Lysozyme Extrinsic eye muscles Superior rectus Inferior rectus Medial rectus Lateral rectus Superior oblique Vision Inferior oblique 28 Melissa Gonzales McNeal 7

8 Vision External Anatomy Eyelids (palpebrae) Conjunctiva Vision External Anatomy Eyelids (palpebrae) Conjunctiva Lacrimal apparatus Lacrimal glands Lacrimal canals (Lacrimal canaliculi) Lacrimal sac Nasolacrimal duct Lacrimal secretions (tears) Lysozyme Can you identify the structures (A-D)? D C B A Vision External Anatomy Extrinsic eye muscles Superior rectus Inferior rectus Medial rectus Lateral rectus Superior oblique Inferior oblique Melissa Gonzales McNeal 8

9 Draw and label the exterior eye Be sure to include the following structures: Palpebrae Conjunctiva Lacrimal gland Lacrimal canal Lacrimal sac Nasolacrimal duct Superior rectus Inferior rectus Medial rectus Lateral rectus Superior oblique Inferior oblique Internal Anatomy of the Eye Layers of Wall of Eyeball Fibrous tunic Vascular tunic Retina (sensory tunic) Fibrous Tunic Cornea Sclera Melissa Gonzales McNeal 9

10 37 38 Vascular Tunic 39 Choroid Ciliary body Ciliary muscle Ciliary processes Suspensory ligaments Lens Iris Circular smooth muscles Radial smooth muscles pupil 40 Melissa Gonzales McNeal 10

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12 Sensory Tunic Ora serrata Optic disc Blind spot Central vein and artery Macula lutea Central fovea Retina (sensory tunic) Pigmented epithelial layer Neural (nervous layer) Photoreceptor layer Rods Cones Bipolar cell layer Bipolar neurons Ganglion cell layer Ganglion cell bodies Melissa Gonzales McNeal 12

13 A B C D E Can you identify the layers (A-E)? Anterior cavity Aqueous humor Anterior chamber Posterior chamber Canal of schlemm Vitreous chamber Vitreous humor Interior of Eyeball Melissa Gonzales McNeal 13

14 Draw and label a cross section of the eye Be sure to include the following structures: 53 Fibrous tunic Vascular tunic Retina Cornea Sclera Choroid Ciliary body Ciliary muscle Ciliary processes Suspensory ligaments Lens Iris Pupil Ora serrata Optic disc Central vein Central artery Macula lutea Central fovea Anterior cavity Anterior chamber Posterior chamber Canal of schlemm Vitreous chamber Aqueous humor Vitreous fluid 54 Visual Pathways to the Brain Photoreceptors Bipolar neurons Ganglion cells Axons of ganglion cells Optic disc Optic nerve Optic chiasm Optic tracts Thalamus Visual cortex on occipital lobe 55 In order to see Physiology of Vision light rays must be focused on retina resulting nerve impulses must be transmitted to visual areas of cerebral cortex 56 Melissa Gonzales McNeal 14

15 Light rays must be focused on retina Refraction - the deflection or bending of a ray of light as it passes through one object and into another object of greater or lesser density cornea, aqueous humor, lens, and vitreous humor Lens Accommodation: An alteration in the curvature of the lens of the eye to focus an image on the retina. Ciliary muscles Relaxed: lens elongated and thin Distant objects Contracted: lens recoils and bulges in middle Near objects Pupil Two sets of smooth muscle fibers in iris change diameter of pupil Radial fibers dilate pupil Sympathetic response Circular fibers constrict pupil Autonomic reflex --- protective effect Permits more accurate near vision 59 Nerve impulses must be transmitted Light rays stimulate chemical reactions in rods and cones which generate electrical impulses Bipolar neurons, ganglion cells, axons of ganglion cells, optic disc, optic nerve, optic chiasm, optic tracts, thalamus, occipital lobe cerebral cortex 60 Melissa Gonzales McNeal 15

16 Binocular vision Spare eye One human eye has 160 o field of view Both eyes have 200 o field of view Increases detection of faint objects and precise depth perception Blind spot Visual acuity Emmetropic Hypertropic Myopic Astigmatism Presbyopia Colorblindness Night blindness Visual Tests The eyes, constantly moving by imperceptible amounts, amplify the difference between the two patterns and create the illusion of motion. Corrected Corrected Corrected Melissa Gonzales McNeal 16

17 Emmetropic Short-wavelength (S) cones, blue cones Medium-wavelength (M) cones, green cones Long-wavelength (L) cones, red cones 65 Color perception is a mixture of nerve signals representing cones 66 with different absorption peaks Blue/pink stripes Green/orange stripes 67 The "green" and "blue" colors in this spiral are exactly the same. They appear different because of the way our eyes perceive them in relation to the contrasting orange and pink stripes. Our eyes contain millions of 'cones' which decode light wavelengths to determine colors. When certain colors are combined, our brain is unable to process the 68 information properly. Melissa Gonzales McNeal 17

18 Eye Reflexes Photopupillary reflex bright light, pupils constrict Accommodation pupillary reflex pupils constrict to focus far to near Night Blindness: Vitamin A deficiency Aging Convergence reflex eyeballs move to change focus from near to far External ear Auricle (pinna) External auditory canal Tympanic membrane Middle ear Auditory oscicles Malleus Incus Stapes Oval window Round window Auditory tube Internal ear HEARING AND EQUILIBRIUM 72 Melissa Gonzales McNeal 18

19 73 Internal Ear Bony labyrinth Perilymph Main regions Vestibule Semicircular canals Cochlea Membranous labyrinth Endolymph Utricle Saccule Semicircular ducts Cochlear duct Vestibulocochlear nerve 74 Bony labyrinth Vestibule Semicircular canals Cochlea Vestibulocochlear nerve Melissa Gonzales McNeal 19

20 Bony labyrinth Perilymph Main regions Vestibule Semicircular canals Cochlea Membranous labyrinth Endolymph Utricle and Saccule Semicircular ducts Cochlear duct 77 Scala vestibule Vestibular membrane Cochlear duct Spiral organ of corti Hair cells Stereocilia Supporting cells Tectorial membrane Basilar membrane Scala tympani Internal Ear Cochlea Scala vestibule Vestibular membrane Cochlear duct Basilar membrane Scala tympani 80 Melissa Gonzales McNeal 20

21 Can you identify the structures (1-6)? Scala vestibule Vestibular membrane Cochlear duct Spiral organ of corti Hair cells Stereocilia Supporting cells Tectorial membrane Basilar membrane Scala tympani Semicircular duct Cristae Hair cells Supporting cells Stereocilia Cupula Utricle and saccule Maculae Hair cells Supporting cells Stereocilia Otolithic membrane Otoliths Inner Ear 84 Melissa Gonzales McNeal 21

22 Can you identify the structures (1-9)? 6 Bony labyrinth Hearing Cochlea Dynamic Equilibrium Semicircular Canals Static Equilibrium Head Position Vestibule Fluid Perilymph Perilymph Perilymph Membranous labyrinth Cochlear duct Semicircular ducts Utricle and saccule Fluid Endolymph Endolymph Endolymph Sensory organ Spiral organ of corti Cristae Macula Membrane Tectorial membrane Cupula Otolithic membrane with otoliths Hair cells Hair cells Hair cells Hair cells Stereocilia Stereocilia Stereocilia Stereocilia Macula Crista 85 Supporting cells Supporting cells Supporting cells Supporting cells 86 Physiology of Hearing In order to hear Sound waves must reach hair cells in spiral organ of corti External auditory meatus, tympanic membrane, malleus, incus, stapes, oval window of inner ear, perilymph and endolymph of cochlea, basilar membrane and hair cells of Organ of Corti Resulting nerve impulses must be transmitted to auditory areas of cerebral cortex when stereocilia bend, they generate impulses that are carried by 8th cranial nerve to auditory areas in temporal lobes of cerebral cortex Melissa Gonzales McNeal 22

23 Physiology of Equilibrium Vibrations must reach equilibrium receptors Ampulla of semicircular canals Acceleration and deceleration Utricle and saccule of vestibule Position of head Resulting nerve impulses must be transmitted to cerebral cortex Information carried by vestibular branch of 8 th cranial nerve Cerebellum, midbrain, temporal lobes of cerebrum 89 Acceleration / Deceleration Ampulla: Crista 90 Position of Head Utricle and Saccule: Macula There is no doubt in my mind that sweet receptors evolved with the sole purpose of identifying highly caloric food sources and bitter receptors to warn the organism of noxious stimuli Charles Zuker, Ph.D. GUSTATION Melissa Gonzales McNeal 23

24 Taste Buds Tongue Papillae Vallate (circumvallate) Fungiform Foliate Filiform tactile receptors Taste buds Gustatory cell Gustatory hair Taste pore Nerves Facial nerve Glossopharyngeal nerve Vagus nerve 93 Foliate papilla Umami Water Life span 7-10 days Melissa Gonzales McNeal 24

25 97 98 Filiform Papillae Physiology of Gustation In order to taste Chemicals must reach chemoreceptors Taste buds located on papilla of tongue Resulting nerve impulses must be transmitted to cerebral cortex Cranial nerves XII Facial nerve IX Glossopharyngeal X Vagus Parietal and temporal cortex Pass through medulla and thalamus 99 I am thankful for laughter, except when milk comes out of my nose. Woody Allen OLFACTION 100 Melissa Gonzales McNeal 25

26 Nose Olfactory epithelium Olfactory receptor cells Bipolar neurons Olfactory hairs branches of dendrites Olfactory bulb Olfactory tract Uncus of cerebral cortex Physiology of Olfaction In order to smell Chemicals must reach chemoreceptors Olfactory epithelium in superior region of nasal cavity Resulting nerve impulses must be transmitted to cerebral cortex I - Olfactory cranial nerve Olfactory nerve fibers travel through ethmoid bone, olfactory bulb, olfactory tracts, temporal lobes of cerebral cortex Pass through limbic system and thalamus 103 Melissa Gonzales McNeal 26