HSS2011 Human Anatomy PDF

HSS2011 Human Anatomy Nervous System III: Senses and 1 Autonomic nervous system Dr. Benson Lau Associate Professor, Department of Rehabilitation Sciences Nervou...

HSS2011 Human Anatomy Nervous System III: Senses and 1 Autonomic nervous system Dr. Benson Lau Associate Professor, Department of Rehabilitation Sciences Nervous System III: Senses and Autonomic nervous system 2 III.1 Sense organs III.1.1 General Senses a , 10 12 , III.1.2 Chemical Senses: Taste and smell S III.1.3 Hearing and equilibrium III.1.4 Eye and Vision 2 3 : , 46 III.2 Autonomic Nervous system III.1 Senses 3 III.1 Senses 4 Sensory receptors: Structures specialized to detect a stimulus Can be: Free nerve endings (simple) or Sense organs (complex) III.1 Senses 5 Classification of receptors: Type of stimulators they detect 1. By modality: 1. Thermoreceptor: Senses heat/cold 2. Photoreceptor: light 3. Chemoreceptor: respond to chemicals (e.g. odor taste) 4. Nociceptors: pain receptors, response to damage, ischemia, excess - stimulation EBER 5. Mechanoreceptors: physical deformation III.1 Senses 6 1. By origins of stimuli: 1. Exteroceptors: external to body 2. Interoceptors: internal organs 3. Proprioceptors: position, movement of body parts III.1 Types of Senses 7 1. General Senses: Employ simple receptors in skin, muscle, tendons, joint and viscera; Modalities: Touch Pressure Stretch Temperature Pain 2. Special senses: EEX1 Employ more complex sense organs; Vision Hearing & equilibrium Taste and smell III.1.1 General Senses 8 Receptors (nerve endings) are relatively simple Receptors classified into: Unencapsulated: dendrites lacking connective tissue wrapping - Encapsulated: dendrites wrapped in glial cells/connective tissue III.1.1 General Senses 9 Types of unencapsulated nerve endings: 1. Free nerve endings: senses warm, cold and pain 2. Tactile discs: light touch & pressure 3. Hair receptors (aka root hair plexuse): movement & bending of hairs X neurone itself III.1.1 General Senses 10 Encapsulated nerve endings: Modified by connective tissues/glial cells, more selective to type of stimulus 1. Tactile corpuscles: in sensitive skin regions, e.g. finger-tip, palm, eyelids, lips 2. End bulbs: in mucous membranes Oval cavity olfactoral ? - , Both respond to light touch and texture III.1.1 General Senses 11 Encapsulated receptors (con’t) 3. Bulbous Corpuscles: heavy touch, pressure, joint movements 4. Lamellar Corpuscles: deep pressure, stretch, tickle, vibration Both found in dermis and joints; combine to feel shape and texture of objects III.1.1 General Senses 12 Encapsulated receptors (con’t) 5. Muscle spindles: in skeletal muscles, near tendon; senses muscle tensions 6. Tendon organs: in tendons; sense tendon tensions Both sense stretch and tension III.1.1 General Senses 13 Receptive field: The area supplied by a single sensory neuron Smaller receptive field higher density of receptors  much sensitive to sensation finer two-point touch discrimination  III.1.1 General Sense 14 Whole picture of Sensory projection pathway: pain receptors Pain received by nociceptors (free nerve endings) Nerve impulse transduced by first-order neuron Synapse at gray matter of spinal cord; Second-order neuron decussate in the spinal cord, nerve impulse sent via axons in the ascending tracts; Second synapse with third-order neurons in reticular formation (brainstem) or thalamus; Signal sent to primary somatosensory cortex by third-order neurons; Pain sensation interpreted by somatosensory association area III.1.2 Chemical Senses: Taste and smell 15 III.1.2 Chemical Senses 16 Chemical senses: detect environmental chemicals Gustation (taste): respond to chemicals in food and drinks Olfaction (smell): respond to chemicals in air III.1.2 Chemical Senses: Gustation Lingual papillae: O ! Visible bumps on tongue Taste buds: Clustered in lingual 1 Back of papillae tongue Found on tongue, and oral cavity (cheeks and soft palate, pharynx and epiglottis) Taste cells (sensory cells): Clustered in taste buds Respond to chemicals 17 III.1.2 Chemical Senses: Gustation 18 Types of lingual papillae: 1. Filiform: - Tiny spikes - No taste buds - - Sense texture of food 2. Foliate: E - Leaf-like - taste buds degenerate after 3 years old - Tn[  III.1.2 Chemical Senses: Gustation 19 taste met Types of taste bud (con’t) 3. Fungiform: is ty - Mushroom-like - Each has about 3 taste buds - for both taste and texture G 4. Vallate: - Large papillae Texture -- spire W - - arranged in a V at rear tongue - Deep circular trench - contains half of the taste buds - III.1.2 Chemical Senses: Gustation 20 Taste Buds: Sense organ for gustation Contains: Taste cells: as taste hairs, as receptor surfaces for taste molecules Replace taste Epithelial cells, not neurons; synapse with nerve cells (stem Cell - fibers short Each lives for 7-10 days Basal cells: Stem cells to replace taste cells - Supporting cells: unclear role  III.1.2 Chemical Senses: Gustation Five primary taste sensation: Sweet Salty Sour Bitter Umami (Meaty taste, stimulated by certain amino acids, glutamate and - aspartate) - All primary taste can be detected throughout the tongue Flavor is the result of combining primary - tastes, smell, food texture, temperature, appearance 21 III.1.2 Chemical Senses: Gustation 22 i Cranial nerves and gustation: CN VII facial nerve: taste of anterior 2/3 of tongue 9 CN IX glossopharyngeal nerve: taste of posterior 1/3 of tongue CN X Vagus nerve: taste from taste buds of palate, pharynx and epiglottis "I Sensory signals set to medulla, then to Hypothalamus and amygdala: autonomic reflexes Thalamus and insula: interpret taste - III.1.2 Chemical Senses: Olfaction 23 Airborne chemicals detected by receptor cells in the olfactory mucosa Receptor cells: O The only neurons directly exposed to the - - - external environment Lives for about 60 days, replaced by basal PNS : usual continuous replacement of cells stem cells (Just taste cells like Has cilia (olfactory hairs), with olfactory receptors for odor molecules CN I: collection of axons of receptor cells III.1.2 Chemical Senses: Olfaction Receptor cells with same collection of fibres receptor type (i.e. V synapse respond to a particular odor) send axons to a same structure called glomerulus ↳ next to nasal They synapse with 2 other types of neurons: mitral and tufted cells; signal sent through these cells to the brain via olfactory tract 24  III.1.2 Chemical Senses: Olfaction 25 & Olfactory tract sends signals to Primary olfactory cortex directly (not through thalamus) From primary olfactory cortex, signals sent to Insula interpretion of smell Limbic system (amygdala and Memory hippocampus) ↓ Emotion Smell may trigger emotion directly (e.g. bad smell) III.1.3 Hearing and equilibrium 26 III.1.3 Anatomy of the Ear 27 Three sections of ear: outer, middle and inner ear Outer and middle: conducting sound to inner ear Inner: sense organ for hearing and equilibrium Outer Ear: Begins with auricle, supported by elastic cartilage Direct sound into auditory canal (external acoustic meatus) Protected by guard hairs and cerumen  III.1.3 Anatomy of the Ear 28 Middle Ear: Transmit vibrations : outer Ceardrum > inner - Begins with tympanic membrane, attached to- three ear-bones (auditory ossicles) The 3 ossicles: (Ear bone) Malleus: hammer like Incus: Anvil like Malleus Stapes: stirrup like; attach to oval window Connected to nasopharynx with auditory tube (eustachian tube) Incus Two muscles (tensor tympani and stapedius) inserts on malleus and stapes respectively, dampen vibration if needed when sound is too loud stapes  III.1.3 Anatomy of the Ear 29 Inner ear: Housed in bony labyrinth (maze) of cranium Membranous labyrinth in bony labyrinth: tube-in-tube structure Begins at oval window, lead to: Vestibule Semicircular canals Cochlea  III.1.3 Cochlea 30 Sense organ for hearing (i.e. Spiral organ Spiral organ) located in cochlear duct (blue) Above cochlear duct: vestibular membrane and scala vestibule Below cochlear duct: Basilar membrane and scala tympani  Inside cochlea III.1.3 Spiral organ 31 Thick epithelium, generates auditory nerve signals - Structures: Hair cells, with stereocilia Inner hair cells: arranged in a row, supplies 90- 95% of sensory fibers of cochlear nerve Outer hair cells: 3 rows, adjust response to - different frequencies Stereocilia covered by tectorial membrane III.1.3 Auditory function anid tymP bran as = eardrum Sound waves vibrate tympanic membrane Auditory ossicles transfer the vibrations Fluid in the inner ear vibrated, moves basilar membrane vibrate up and down Hair cells are thrust up and down - Rocking of stereocilia opens makes potassium ions go into the hair cells and excite the cells - Neurotransmitter from hair cells creates nerve signal 32  III.1.3 Saccule and Utricle Sense organ for static equilibrium and - linear acceleration G Macula: 2 X 3 mm patch of hair cells and supporting cells Diff in head orientation Macula Sacculi: vertical. [ Macula utriculi: horizontal Hair cells in macula: -Call Stereocilia embedding in otolithic membrane Otolith: calcium carbonate and protein Movement of head  move otolithic membrane M bending stereocilia >  generate nerve signals  interpret head orientation by combining - signals from saccule and utricle A - 33  III.1.3 Semicircular ducts 34 Sense organ of angular acceleration Utricle Filled with endolymph Saccule Have dilated sac called ampulla Inside an ampulla: Hair cells with stereocilia embedded in cupula, gelatin-like structure Ampulla Supporting cells Detection of angular movement: Head turns  semicircular ducts -rotate  endolymph lags behind  push cupula  bends stereocilia and stimulate hair cells  nerve signal to the cranial nerve III.1.4 Eye and Vision 35 III.1.4 Accessory structures of Orbit 36 Orbit: bony socket housing the eyeball Structures of orbit: sweat Eyebrows: shield the eyes from glare/perspiration Eyelashes: guard hairs Eyelid (palpebrae): moisten eyes, block foreign objects/lights Separated by palpebral fissure; meet at medial/lateral commisusures Tarsal plate: fibrous margin Tarsal glands: oily secretion, prevent tear evaporation III.1.4 Accessory structures of Orbit 37 Conjunctiva: Transparent, mucous membrane covers inner - surface of eyelid and anterior eyeball Two contact surfaces: Palpebral conjunctiva: to eyelid Bulbar conjunctiva: to eyeball - Prevent eyeball from drying - - III.1.4 Accessory structures of Orbit 38 secretion of tears Lacrimal apparatus: Produce and drain tears into nasal cavity Direction of tear flow: Lacrimal gland secret tears ↓ Conjunctiva (cleaning and lubricate) Lacrimal caruncle near medial commissure Lacrimal punctum Lacrimal canaliculus Lacrimal sac Nasolacrimal duct Nasal cavity III.1.4 Accessory structures of Orbit 39 Extrinsic eye muscles: For movement of eyes Rectus (straight) muscle X4, Oblique muscles X 2 Rectus: superior, inferior, medial, lateral Move eyeballs in 4 directions Oblique: h Superior: tendon passes through a loop called trochlea Inferior + Rotate the eyeballs III.1.4 Anatomy of the eyeball 40 Three principal components: 1. O Three layers (tunics), form the wall vitreous humor > Retina lens conjunctiva numor Transparent - comea , , aqueous , 2. Optical components, admit and focus light , , 3. Neural components, retina and optic nerve, produce and transduce neural signals  III.1.4 Anatomy of the eyeball: tunics 41 Three tunic layers: -. 1. Outer fibrous layer Sclera and cornea Sclera: dense collagenous connective tissue, protect eyeball - -b 2. Middle vascular layer (aka uvea) Choroid: vascular, pigmented layer Ciliary body: supports the lens via ciliary muscle Iris: adjustable diaphragm, - control amount of light through pupil by pupillary constrictor/dilator 3. Inner layer: Retina III.1.4 Anatomy of the eyeball: optical components 42 Transparent 1. Cornea: anterior region admits ②light 2. Aqueous humor: Serous fluid secreted by ciliary processes Flows from posterior to anterior chamber 3. Lens: suspended by suspensory ligament -Focus of image - suspensory 4. Vitreous body: ligament Transparent jelly filling vitreous chamber Maintain intraocular pressure III.1.4 Anatomy of the eyeball: neural components 43 Neural components consists retina and optic nerve Retina: Attach to wall of eyeball at - Optic disc: where optic nerve leaves; Ora serrata: anterior margin Layered structure: Pigment epithelium: absorb stray light - Photoreceptor cells: Convert light signal to& nerve signal Rods: night, monochromatic vision Cones: day,-trichromatic vision  - III.1.4 Anatomy of the eyeball: neural components 44 Retina (con’t) Bipolar cells: Interneurons, send signals from photoreceptors to ganglion cells or amacrine cells Ganglion cells: Axons form optic nerve Contains melanopsin, for circadian rhythm - Other cell types in retina: Amacrine cells: connecting bipolar cells (receives rod input) to ganglion cells Horizontal cells: diverse roles, e.g. in perception of contrast Muller glial cells: structural and metabolic support III.1.4 Visual projection pathway 45 (interneurone) First-order neuron: bipolar cells Second-order neuron: retinal ganglion cells Axons of ganglion cells form optic nerve, form optic chiasm with hemidecussation ent open Most axons from optic tract end at the thalamus (lateral genicular nucleus), - cansuous visaa , - synapse with third-order neuron] optin radiation mangporGangis Third-order neurons form the optic radiation, project to the primary visual cortex ins Melanopsin-containing ganglion cells: to pretectal nucleus and superior colliculus, & cexvinsivage musues for visual reflex III.2 Autonomic Nervous system 46 III.2 Autonomic Nervous system (ANS) 47 Regulate fundamental life processes, e.g. heart rate, blood pressure, temperature, digestion etc. unconsciously Works through visceral reflexes III.2 Visceral reflex 48 Unconscious, automatic, stereotyped responses to stimulation Involves visceral receptors and effectors Somewhat slower response - Receptors detect Stretch Tissue damage Blood chemicals Body temperature Other internal stimuli Afferent neurons leading to CNS, interneurons in the CNS, efferent neurons and effectors III.2 visceral reflex 49 Example: high blood pressure (X) activates visceral baroreflex III.2 Division of the ANS 50 Traditionally ANS divided into sympathetic and parasympathetic divisions Sympathetic: Prepare for ‘’fight-or-flight’’ Increase alertness, heart rate, blood pressure, etc Parasympathetic: Calming effect: ‘’rest and digest’’ Reduce energy expenditure and for bodily maintence  III.2 Neural Pathways of ANS Motor pathways different between ANS and somatic motor system of diff PNS : collection neurones ↑ Presence of autonomic ganglion in ANS Preganglionic neuron [ Soma in brainstem or spinal cord Axon terminates in ganglion - Postganglionic neuron Soma in ganglion Axon extends to target 14-51  III.2 Motor pathway of Sympathetic Division · Thoracolumbar division: Nuclei arise at THEthoracic and lumbar spinal cords 11-15 Relatively short preganlionic fibers Relatively long postganglionic fibers O 14-52 Sympathetic chain ganglia (paravertebral ganglia) III.2 Motor pathway of Parasympathetic Division ② Craniosacral division Motor pathway arise from C 4 cranial/sacral spinal cord - S1-S5 Long preganglionic fibers End in terminal ganglia in or near the target organ Very short postganglionic fibers Innervation to head Oculomotor nerve (III) 3 Facial nerve (VII) 7 Glossopharyngeal nerve (IX) 9 Innervation to viscera Internal Organs Vagus nerve (X) 5 Summary: Module 3 – Nervous system 54 Lecture I: Basic units of nervous system; nerves and spinal cord Lecture II: Brain and cranial nerves Lecture III: Senses and ANS Reference: 55 Textbook Chapter 16 and 17