Functional Classes of Neurons

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Sensory Systems Chapter 22 1. Sight 2. Hearing 3. Smell 4. Taste 5. Touch 6. Balance?? 7. Pain?

nervous system Differences between Nerve Cells and Receptor Cells 1 3 Sensory (afferent) neurons conduct signals from receptors to the CNS.

1 Sensory Systems Chapter Sight 2. Hearing 3. Smell 4. Taste 5. Touch 6. Balance?? 7. Pain?? Subdivisions of Nervous System Central nervous system (CNS) Spinal cord Brain Peripheral nervous system (PNS) Nerves Ganglia 12-2 Functional Classes of Neurons Peripheral nervous system Central nervous system Differences between Nerve Cells and Receptor Cells 1 3 Sensory (afferent) neurons conduct signals from receptors to the CNS. Motor (efferent) neurons conduct signals from the CNS to effectors such as muscles and glands. 2 Interneurons (association neurons) are confined to the CNS. Nervous System: 1) Detect stimuli and send to brain (sensory) 2) Interpret the information received 3) Respond to information (motor) Nerve Cells: - Action Potential - Electrical current runs down the cell - Triggers release of neurotransmitters 12-3 Sensory receptors are located throughout the body can be classified by: 1. Based on origin of stimuli: Exteroceptors (external) Interoceptors (within body organs) Proprioceptors 2. Based on energy they respond to (modality): - Mechanorecptor - Thermoreceptor - Chemoreceptor - Osmoreceptors - Photoreceptor - Nociceptors Classification of Receptors 3. by distribution general (somesthetic) senses - widely distributed special senses - limited to head vision, hearing, equilibrium, taste, and smell Some receptors are neurons

two-point touch discrimination Neuron 1 2 3 Neuron 1 Neuron 2 Neuron 3 (a) One large receptive field (arrow) (b) Three small receptive fields (arrows) 16-7 16-8 Receptors Transmit Four Kinds of

2 Receptors Transmit Four Kinds of Information 1. Modality - type of stimulus or the sensation it produce vision, hearing, taste Receptive Fields 2. Location encoded by which nerve fibers are issuing signals to the brain receptive field area that detects stimuli for a sensory neuron receptive fields vary in size fingertip versus skin on back two-point touch discrimination Neuron Neuron 1 Neuron 2 Neuron 3 (a) One large receptive field (arrow) (b) Three small receptive fields (arrows) Receptors Transmit Four Kinds of Information 3. Intensity which fibers are sending signals how many fibers are firing how fast these fibers are firing 4. Duration how long the stimulus lasts 1. phasic receptor generate a burst of action potentials when first stimulated, then quickly adapt and sharply reduce or stop signaling even though the stimulus continues smell, hair movement, and cutaneous pressure 2. tonic receptor - adapt slowly, generate nerve signals more steadily proprioceptors - body position, muscle tension, and joint motion 16-9 Fig.41.8 Vestibule (Utricle & Saccule) Bony labyrinth 2

direction 41-6 Gravity and speed Vestibular

receptors in the cochlea endolymph - Hair

waves) Vibrations Fluid in cochlea Basilar

3 Saccule and Utricle - macula Macula 41.6 Endolymph Turning Movements Change in direction 41-6 Gravity and speed Vestibular apparatus Another Mechanoreceptor - Auditory receptors in the cochlea endolymph - Hair cells respond to pressure waves (sound waves) Vibrations Fluid in cochlea Basilar membrane vibrates 41.7 Hair cells are stimulated Info. to brain 3

4 Fig.41.8 scala vestibuli Cochlear duct Vestibular membrane scala tympani Organ of corti Fig.41.9 Scala vestibuli Vestibular Membrane Scala tympani Fig

Cochlear nerve, division of the vestibulocochlear (VIII) nerve (b) Tympanic canal (contains perilymph) Oral window (a) Organ of Corti

Organ of Corti membrane Basilar membrane Coc hlear duc t Cilia Force Hair cell Cochlear nerve Basilar membrane Please note that due to

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08 Gustatory Sensation: Taste Chemoreceptors: Sesory receptors that respond to chemicals Taste (gustation) (taste buds) Smell (olfaction)

5 Cochlear nerve, division of the vestibulocochlear (VIII) nerve (b) Tympanic canal (contains perilymph) Oral window (a) Organ of Corti Vestibular canal (contains perilymph) Vestibular membrane Cochlear duct (contains endolymph) Vestibular canal Tectorial membrane Tectorial Organ of Corti membrane Basilar membrane Coc hlear duc t Cilia Force Hair cell Cochlear nerve Basilar membrane Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the Normal or Slide Sorter views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at player. (c) Fluid vibrations Tympanic canal Fig Gustatory Sensation: Taste Chemoreceptors: Sesory receptors that respond to chemicals Taste (gustation) (taste buds) Smell (olfaction) (olfactory cells) Taste requires dissolving of substances Four classes of stimuli-- sour, bitter, sweet, and salty 10,000 taste buds found on tongue, soft palate & larynx Found on sides of circumvallate & fungiform papillae 3 cell types: supporting, receptor & basal cells Dad!! Flavor Flav!! Taste bud: 1. Support cells 2. Gustatory receptor cells 3. Basal cells Umami Meaty/savory 5

Olfactory epithelium Adaptation???? cilia tapetum lucidum Fig. 41.

lens thins to focus light on the retina Close object: the lens fattens to

humor lens eyelash pupil (b) Distant object: light is focused in front of the

object is focused on the retina cornea optic nerve aqueous humor Lens muscle

eye (short eyeball) Convex lens converges light rays, so the object is focused

6 Olfactory epithelium Adaptation???? cilia tapetum lucidum Fig retina The human eye sclera ligaments (a) Normal eye Distant object: the lens thins to focus light on the retina Close object: the lens fattens to focus light on the retina choroid retina iris fovea blood vessels vitreous humor lens eyelash pupil (b) Distant object: light is focused in front of the retina Nearsighted eye (long eyeball) Concave lens diverges light rays, so the object is focused on the retina cornea optic nerve aqueous humor Lens muscle (ciliary body) (c) Close object: light is focused behind the retina Farsighted eye (short eyeball) Convex lens converges light rays, so the object is focused on the retina Fig Red green blue cones Fig Rods = dim light Cones = color Fig

photoreceptor layer bipolar neuron layer ganglion neuron layer 2 other cell

7 Layers of Retina Pigmented epithelium nonvisual portion absorbs stray light & helps keep image clear 3 layers of neurons (outgrowth of brain) photoreceptor layer bipolar neuron layer ganglion neuron layer 2 other cell types (modify the signal) horizontal cells amacrine cells Brain Pathways of Vision 7

Special Senses. Accessory Structures of the Eye. The Eye and Vision. Accessory Structures of the Eye. Accessory Structures of the Eye

Special Senses. Accessory Structures of the Eye. The Eye and Vision. Accessory Structures of the Eye. Accessory Structures of the Eye 8 PART A Special Senses PowerPoint Lecture Slide Presentation by Jerry L. Cook, Sam Houston University ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY EIGHTH EDITION ELAINE N. MARIEB The Senses General senses