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PowerPoint Presentation to Accompany © 2010 Delmar, Cengage Learning 1 Chapter 11 The Nervous System The Brain, Cranial Nerves, Autonomic Nervous System and the Special Senses © 2010 Delmar, Cengage Learning 2 Introduction • Brain is divided into four main parts – Brainstem ( Medulla oblongata, Pons, Midbrain) : controls breathing, heartbeat rates and reactions to auditory and visual stimuli – Diencephalon: controls homeostasis – Cerebrum: controls intellectual processes and emotions – Cerebellum: maintains body posture and balance © 2010 Delmar, Cengage Learning 3 Blood supply and the Brain Barrier System: • Although the brain constitutes only 2% of the adult body weight, it receives 15% of the blood (750 ml/min) • Consumes 20% of the body’s oxygen and glucose. • 10 seconds of interruption in blood flow can cause unconsciousness (4 min = irreversible brain damage) • A blood-brain barrier regulates what substances can get from the blood stream into the brain. Injury, inflammation, toxins may break it down. • Permeable to water, glucose, oxygen, carbon dioxide, alcohol, caffeine, nicotine and anesthetics. © 2010 Delmar, Cengage Learning 4 The Principal Parts of the Brain © 2010 Delmar, Cengage Learning 5 The Principal Parts of the Brain (cont’d.) • Main parts: brainstem, diencephalon, cerebrum and cerebellum • Protection – Cranial bones (fontanels close ~2 yrs old) – Meninges – Cerebrospinal fluid • Ventricles – Interventricular foramen © 2010 Delmar, Cengage Learning 6 The Principal Parts of the Brain (cont’d.) © 2010 Delmar, Cengage Learning 7 Ventricles of the brain: • 4 internal chambers called ventricles • Several “canals” interconnect the ventricles and a central canal extends through the medulla oblongata into the spinal cord. • These ventricles and canals are lined with ependymal cells – CSF • Each ventricle contains a choroid plexus – network of blood capillaries anchored to the floor or wall of the ventricle and covered by ependymal cells. © 2010 Delmar, Cengage Learning 8 © 2010 Delmar, Cengage Learning 9 Cerebrospinal fluid /CSF • Serves as a shock absorber – fills the arachnoid space so the brain & spinal cord “float” • Provides some nutrients and removes some wastes • Optimizes chemical levels for accurate neuronal signaling • Produced by the ependymal cells of the choroid plexus which is located in some ventricles within the brain. • Production equals reabsorption so the volume of CSF remains the same. © 2010 Delmar, Cengage Learning 10 The CSF circulates Through the ventricles and then flows to the Sub-arachnoid space where it will flow around the brain & spinal cord – finally it will be reabsorbed by villi within the arachnoid layer © 2010 Delmar, Cengage Learning 11 The Anatomy and Functions of the Brainstem © 2010 Delmar, Cengage Learning 12 The Anatomy and Functions of the Brainstem (cont’d.) • Medulla oblongata – – – – – Ascending and descending tracts Connects spinal cord with the brain Some tracts cross over in medulla Reticular formation: controls consciousness Reflex centers – involuntary, simplest path able to receive a stimulus & produce a response. • Vital=heart rate, breathing & blood vessel size, BP. • Less vital=vomiting, swallowing, coughing, sneezing and hiccuping © 2010 Delmar, Cengage Learning 13 The Anatomy and Functions of the Brainstem (cont’d.) • Pons varolii – Connects spinal cord with brain – between medulla and midbrain – Connects parts of brain with each other – relays impulses from one side of cerebellum to the other – Helps control breathing (back up) along with Medulla oblongata –even breaths © 2010 Delmar, Cengage Learning 14 The Anatomy and Functions of the Brainstem (cont’d.) • Midbrain – Ventral cerebral peduncles: convey impulses from cortex to pons and spinal cord – Dorsal tectum: reflex center – Controls movement of head and eyeball (visual stimuli) – survival activity – Controls movement of head and trunk (auditory stimuli) – you automatically turn toward a noise or movement © 2010 Delmar, Cengage Learning 15 Inferior (underside) of brain: © 2010 Delmar, Cengage Learning 16 The Anatomy and Functions of the Diencephalon © 2010 Delmar, Cengage Learning 17 Location of Diencephalon: © 2010 Delmar, Cengage Learning 18 The Anatomy and Functions of the Diencephalon (cont’d.) • Optic tracts • Mamillary bodies: memory and emotional responses • Thalamus – Relay station for sensory impulses – Interpretation center for pain, temperature and touch (if damaged, sensitivity to pain or loss of consciousness) • Epithalamus: contains pineal gland © 2010 Delmar, Cengage Learning 19 Example of relaying information: © 2010 Delmar, Cengage Learning 20 The Anatomy and Functions of the Diencephalon (cont’d.) • Hypothalamus: homeostasis – Lies inferior to the thalamus and attached by a small stalk to the pituitary gland – Controls and integrates autonomic nervous system – Receives sensory impulses from internal organs – Controls thirst, hunger, body temp, memory, emotion ( rage) and sleep – Controls pituitary gland and links endocrine and nervous systems © 2010 Delmar, Cengage Learning 21 The Anatomy and Functions of the Diencephalon (cont’d.) • Pineal gland: – Pine cone shaped growth attached to the roof of the third ventricle. – Decreases in size with age. – Regulates the gonads and the annual breeding cycle. – Produces serotonin by day and melatonin at night. – May regulate timing of puberty. © 2010 Delmar, Cengage Learning 22 Sagittal cut: © 2010 Delmar, Cengage Learning 23 Other areas: Reticular formation (or activating system) • neural network” involves neurons from the medulla, pons, hypothalamus, midbrain and cerebrum & cerebellum – Controls consciousness – Stimulates nerve cells to be active’ – During sleep, RAS shuts down areas so they can recover (form more neurotransmitters). Sleep runs in 90 minute cycles (REM vs. non-REM sleep) – Coordination – as you get tired, you slump – “filters” incoming sensory information and passes on only important stuff (like pain) © 2010 Delmar, Cengage Learning 24 Means “network” © 2010 Delmar, Cengage Learning 25 The Cerebrum: Structure and Function © 2010 Delmar, Cengage Learning 26 The Cerebrum: Structure and Function (cont’d.) © 2010 Delmar, Cengage Learning 27 The Cerebrum: Structure and Function (cont’d.) • Cerebral cortex: gray matter surface • Longitudinal fissure separates two hemispheres (R & L) – Control muscles on opposite sides – Right: artistic, spatial & pattern awareness – Left: language, scientific, reasoning, logic • Premotor area involved in learning –how to walk before doing it) • Gyri: folds • Sulci: grooves • Corpus callosum: bridge connecting two hemispheres (coordinates) – women’s larger (intuition?) © 2010 Delmar, Cengage Learning 28 The Cerebrum: Structure and Function (cont’d.) • Surface of the cortex – Motor areas control muscular movements – Sensory areas interpret sensory impulses – Association areas process emotions and intellect © 2010 Delmar, Cengage Learning 29 The Cerebrum: Structure and Function (cont’d.) • Basal ganglia/cerebral nuclei – Composed of structures from the cerebrum, thalamus, and midbrain – Basal ganglia are not easily seen and work with the cerebellum to coordinate muscle activities associated with rhythmic movements like walking, running, etc. – Limits unwanted muscle activity © 2010 Delmar, Cengage Learning 30 The Limbic System; • Involved in the involuntary emotional aspects of behavior – memories of past pleasant or unpleasant experiences affect how we act in certain situations. • Associated with emotions such as pain, pleasure, fear, rage, sorrow, sexual feelings, affection, anger and docility depending on the area of the “system” which is stimulated. • Amygdala – emotion • Hippocampus – memory (determines where a memory is to be stored) – Alzheimers? © 2010 Delmar, Cengage Learning 31 Way inside the brain… © 2010 Delmar, Cengage Learning 32 The Cerebrum: Structure and Function (cont’d.) • Cerebral hemispheres – Frontal lobe: • • • • • • • muscle movement (planned – like dancing) moods, aggression (lobotomy?) Smell Motivation & personality (part is genetic…) problem solving, reasoning (right from wrong) visual scanning (phone book) Broca’s area – motor speech center (thoughts into words) – stroke? © 2010 Delmar, Cengage Learning 33 The Cerebrum: Structure and Function (cont’d.) • Parietal lobe: – touch, pain, balance, taste, temperature (sensory) – Common integration center – gathers information from different areas of cerebrum and analyzes see someone in the hall ( visual, perfume, voice, etc) © 2010 Delmar, Cengage Learning 34 The Cerebrum: Structure and Function (cont’d.) • Temporal lobe: – hearing, smell, memory, abstract thought, judgment – Taste center – taste buds – Olfactory center – nasal receptors – Wernicki’s area – sensory speech – determines if it is speech being heard or something else (music, noise) © 2010 Delmar, Cengage Learning 35 The Cerebrum: Structure and Function (cont’d.) • Occipital lobe: • posterior part of the brain • Visual center – info from eyes ( color, shape & movement) • Visual association area: uses past visual experiences in memory to recognize what is being seen © 2010 Delmar, Cengage Learning 36 The Cerebrum: Structure and Function (cont’d.) • Insula – 5th lobe: – Also called “Island of Reil” – Inside lobe of cerebrum – Deep to the parietal, frontal & temporal (these need to be removed in order to see it) – Not sure of function, but has been associated with spoken language, taste, sensing info from visceral receptors. – Social emotions – disgust, pride, moral intuition, craving drugs (cigarettes?) – being human? © 2010 Delmar, Cengage Learning 37 The Cerebellum: Structure and Function © 2010 Delmar, Cengage Learning 38 The Cerebellum: Structure and Function (cont’d.) • Butterfly-shaped – clump of cauliflower? • Two partially separated hemispheres connected by vermis • Functions – same side control (ipsilaterally) – Coordinating muscular movements – Maintaining posture – Maintaining balance © 2010 Delmar, Cengage Learning 39 The Cerebellum: Structure and Function (cont’d.) • Arbor vitae – called the “tree of life” • is the cerebellar white matter, so called for its branched, tree-like appearance. It brings sensory and motor information to and from the cerebellum. • Proprioception – awareness of the location and action of a particular body part (gymnast) © 2010 Delmar, Cengage Learning 40 Arbor vitae © 2010 Delmar, Cengage Learning 41 The Autonomic Nervous System © 2010 Delmar, Cengage Learning 42 The Autonomic Nervous System (cont’d.) • Subdivision of efferent PNS • Functions without conscious effort • Controlled mostly by hypothalamus, some by medulla • Regulates functions of internal organs • Assists in maintaining homeostasis • Helps deal with emergency situations © 2010 Delmar, Cengage Learning 43 General Characteristics of the ANS: • It is a two-neuron pathway: – Sensory signals from viscera and skin send signals to autonomic neurons in brain and spinal cord. – A preganglionic neuron cell body is located within the CNS (brain stem or spinal cord). – Preganglionic fibers (efferent fibers) synapse with a ganglionic neuron located in the PNS – A postganglionic fiber terminates on the effector organ (heart, stomach, etc). © 2010 Delmar, Cengage Learning 44 The Autonomic Nervous System (cont’d.) • Includes nerves, ganglia, and plexuses which carry impulses to all smooth muscle, secretory glands, and heart muscle. • Regulates the activities of the visceral organs (heart and blood vessels, respiratory organs, alimentary canal, kidneys, bladder, and reproductive organs) • The sympathetic and parasympathetic may be antagonistic in their action: – The sympathetic may accelerate the heartbeat in response to fear whereas the parasympathetic slows it down.(dual innervation) – You wont knit and run from a tiger at the same time! © 2010 Delmar, Cengage Learning 45 The Autonomic Nervous System (cont’d.) • Sympathetic – Energy and stressful situations – FIGHT or FLIGHT! – Increases heartbeat, BP and breathing rates – Neurotransmitters: acetylcholine and norepinephrine – occurs in the ganglions • Causes an increase in activity in most organs ( except digestive system) – uses lots of energy – Preganglionic neurons in the thoracic and lumbar regions of spinal cord – Synapse alongside vetebrae or collateral (bonus) ganglion © 2010 Delmar, Cengage Learning 46 © 2010 Delmar, Cengage Learning 47 The Autonomic Nervous System (cont’d.) • Parasympathetic – Restores body to nonstressful state – Neurotransmitter: acetylcholine – Stimulates digestion, urination and defecation, decreases others (Rest and Repose) – Preganganglionic neurons in brain stem or sacral regions – Over 75% are found in the Vagus nerve (CN X) – Synapse (ganglia) close to target organs © 2010 Delmar, Cengage Learning 48 © 2010 Delmar, Cengage Learning 49 The 12 Cranial Nerves and Their Functions © 2010 Delmar, Cengage Learning 50 Cranial Nerves: • Part of the Peripheral Nervous System • 12 pairs of nerves which begin in the brain. More precise & accurate than other nerves. • Designated by number and name (gives clue to the function) • Most are “mixed” nerves; they carry both sensory and motor fibers. • The olfactory, optic and vestibulocochlear nerves only carry sensory fibers (pick up only the stimuli) • SEE HANDOUT © 2010 Delmar, Cengage Learning 51 KNOW THESE! © 2010 Delmar, Cengage Learning 52 © 2010 Delmar, Cengage Learning 53 The 12 Cranial Nerves and Their Functions (cont’d.) • (I) Olfactory: smell • (II) Optic: sight • (III) Oculomotor: movement of eyeball, constriction of pupil • (IV) Trochlear: movement of eyeball © 2010 Delmar, Cengage Learning 54 The 12 Cranial Nerves and Their Functions (cont’d.) • (V) Trigeminal: chewing, sensations in teeth – Ophthalmic V1 – Maxillary V2 – Mandibular V3 • (VI) Abducens: movement of eyeball (outward) • (VII) Facial: facial expression, taste, tear and salivary glands • (VIII) Vestibulocochlear: equilibrium, hearing © 2010 Delmar, Cengage Learning 55 The 12 Cranial Nerves and Their Functions (cont’d.) • (IX) Glossopharyngeal: swallowing, taste, salivary glands • (X) Vagus: certain muscle movements – throat, affects heart, digestive system, sensory impulses • (XI) Accessory: swallowing, head movement, voice • (XII) Hypoglossal: swallowing, speech, tongue © 2010 Delmar, Cengage Learning 56 An aid to memory: • • • • • • • Old = Olfactory (I) Opie = Optic (II) Occasionally= Oculomotor (III) Tries = trochlear (IV) Trigonometry = trigeminial ( V) and =abducens (VI) feels = facial (VII) Very= vestibulocochlear ( VIII) Gloomy, = glossopharyngeal ( IX) Vague = vagus ( X) And = accessory ( XI) Hypoactive = hypoglossal (XII) © 2010 Delmar, Cengage Learning 57 Neurological Diseases & Disorders • • • • • • • • • • • Hydrocephalus Aging Seizures/convulsions Alzheimer’s disease Parkinson’s disease Reye syndrome TIA Cerebrovascular accident/CVA Concussion Shingles Multiple Sclerosis © 2010 Delmar, Cengage Learning 58 Hydrocephalus: • Excessive build-up of CSF • Either excessive production or inability to reabsorb the fluid (perhaps a tumor) • Results in pressure on the brain tissue and eventual damage to the neurons • Treatment usually a shunt and fluid drains into abdomen. © 2010 Delmar, Cengage Learning 59 Treatment: © 2010 Delmar, Cengage Learning 60 Aging: • Neurons lost – up to 1000 a day! (minor considering we have several billion) so may not see changes until over 75 yrs old • Studies show better function & decision making at 60 than 30! • Decreased capacity for sending impulses (esp. hearing, vision, smell, taste) • Voluntary muscular activity can decrease significantly © 2010 Delmar, Cengage Learning 61 Seizures/convulsions: • Caused by abnormal neuronal signaling. • 2 types: – Petit mal – “blanking out” – Grand mal – violent muscle contractions • Causes: – Epilepsy- certain parts of the brain are overactive, producing convulsive seizures & possible loss of consciousness. – Brain trauma – Fever – Allergic reactions – Increased intercranial pressure – due to hemorrhage, tumor or swelling © 2010 Delmar, Cengage Learning 62 Alzheimer’s disease: • Disabling senile dementia – unknown cause but most patients have similar things in common: – Loss of neurons in certain brain area – especially those that use ACH – Abnormal protein deposition within the neurons – Tangled protein filaments within the neurons © 2010 Delmar, Cengage Learning 63 CAT scan of Alzheimer’s brain: © 2010 Delmar, Cengage Learning 64 Parkinson’s Disease • Common with aging • Caused by a deficiency of dopamine • Characterized by tremors, a shuffling gait, pill-rolling (movement of thumb and index finger), and muscular rigidity. • Has difficulty initiating movement • Treated with the drug L-dopa & other drugs for the symptoms. © 2010 Delmar, Cengage Learning 65 © 2010 Delmar, Cengage Learning 66 Reye Syndrome; • Swelling with certain viral infections (chicken pox, flu) in children. • Aspirin use appears to increase risk – could result in irreversible damage to the liver (toxins) and brain - can be fatal. • Cerebral edema, high ammonia levels, other toxic wastes in serum • Results in lethargy, headache, vomiting, disorientation, seizures, coma © 2010 Delmar, Cengage Learning 67 TIA = Transient ishemic attack • Episode of temporary interruption of blood supply to the brain • A sign of impending stroke © 2010 Delmar, Cengage Learning 68 Cerebrovascular accident /CVA • Stroke: destruction of brain tissue following an interruption of blood supply due to: – Clot formation – hemorrhage © 2010 Delmar, Cengage Learning 69 Concussion: • Traumatic injury to the brain • Leading to brain edema (swelling) © 2010 Delmar, Cengage Learning 70 Shingles: • Acute infection of nerves of the PNS caused by the herpes virus which causes chicken pox • Causes severely painful blisters and discoloration. © 2010 Delmar, Cengage Learning 71 Multiple Sclerosis: • Sclerosis: Greek > sklero means “hard”, scarring • • • • • or plaques result from demyelination. Myelin sheath is slowly deteriorating Autoimmune disease: body confuses virus proteins and own myelin Increased protein in CSF Fatigue, spasticity, bladder & bowel dysfunction, tremors, facial & other pain, sexual dysfunction, depression,etc. Drugs used: steroids, immunosuppresants © 2010 Delmar, Cengage Learning 72 © 2010 Delmar, Cengage Learning 73 The Special Senses © 2010 Delmar, Cengage Learning 74 Sensations: • Interpretation of impulses in the cerebral cortex – Determined by the area of the cortex ( frontal =smell, occipital=sight) • Intensity depends on frequency of stimuli – More stimuli, more receptors are active ( a “touch” is less, a “punch” stimulates more receptors) © 2010 Delmar, Cengage Learning 75 Factors in sensation: • Projection (helps out) – Sensation is recognized where the stimulus occurs ( hurt finger or cookies smell from kitchen) • Adaptation – With repeated stimuli the receptor decreases its response – This prevents over-stimulation (frequently with smell – perfumes, barn, etc.) © 2010 Delmar, Cengage Learning 76 General Senses: • Found throughout the body, esp. skin, muscles, tendons and visceral organs (guts) i.e. heartburn felt in torso • Proprioceptive – awareness of location & action of a part of the body (driving a car) – Thermal – temperature • Heat receptors – sensitive above 77 degrees, above 113 degrees painful • Cold receptors – sensitive below 68 degrees, below 50 degrees painful • Comfort zone (Rm temp) 69-76 degrees – no adjustment (no shiver, no sweat) © 2010 Delmar, Cengage Learning 77 General Senses: Mechanoreceptors • Tactile: touch, pressure, vibration, tickle – Stereognosis – ability to identify an object by touch only • Pacinian corpuscles (pressure) – Deep in dermis or hypodermis – more force • Meissner’s corpuscles – In dermal papillae (fingerprint bumps) – Detect very light touch (lips) • Free nerve endings – in epithelial & connective tissue – Some attached to hair to detect bending (fly on arm) – Other detect pain in guts (spleen has pain , not itchy) © 2010 Delmar, Cengage Learning 78 Pain: • Free nerve endings are stimulated whenever tissue is damaged (protective detectors) – Acute – sudden, rapid onset – Chronic – slow onset>worsens • Referred pain: – Occurs if projection is not accurate – feels pain “originating” from an area where stimulus is not occuring (heart attack or appendicitis) – Probably occurs because some nerves carry impulses from the body wall and internal organs © 2010 Delmar, Cengage Learning 79 Common sites for referred pain: © 2010 Delmar, Cengage Learning 80 The Sense of Smell • Molecules in air dissolve in nasal mucus • Bipolar sensory neurons transfer chemical impulse • Olfactory bulbs receive impulse • Impulse sent to olfactory tract, which carries impulses into the cerebral cortex • Odor variety dependent on brain interpretation – adapts quickly for perfume, slowly for smoke (toxic) © 2010 Delmar, Cengage Learning 81 © 2010 Delmar, Cengage Learning 82 The Sense of Taste • Taste buds on tongue, palate and pharynx & epiglottis ( maybe esophagus?) • Taste buds (on papillae) cell types – Exterior capsule: epithelial cells – Interior: taste cells • Taste depends on chemicals dissolved in saliva (chemoreceptors) • Taste influenced by olfactory sensations • Spicy foods can stimulate pain receptors! © 2010 Delmar, Cengage Learning 83 The Sense of Taste • Impulses are sent to cerebral cortex for evaluation – Receptors adapt fairly quickly (can over eat) – 5 primary tastes • Salty, bitter, sweet, sour and umani ( metallic MSG) – “flavors” are a combination of basic tastes – pepperoni pizza (salty & sweet) • Decreased saliva due to drugs can change taste © 2010 Delmar, Cengage Learning 84 © 2010 Delmar, Cengage Learning 85 The Sense of Sight • Eyes protected by eyelids and eyelashes • Tears – Lubricate the eyes – Contain bacteriolytic lysozyme enzyme – Contain salt and gamma globulin • The inner lining of the eyelid is the conjuctiva. When inflamed = pink eye • The extrinsic eye muscles move the eye around within the orbit. You don’t always have to turn your head! © 2010 Delmar, Cengage Learning 86 Vision:Internal eye structures: • Outer fibrous layer: puncture resistance – Sclera – white portion – Cornea – clear window-like structure on anterior of the eye • Middle vascular layer – Choroid – provides nutrients and has melanin which will absorb light rays after they have been “seen” by the receptors – Iris – colored part that controls the amount of light by regulating the size of the pupil. – Ciliary body – controls shape of the lens to assist with focusing of the image in the eye. © 2010 Delmar, Cengage Learning 87 The Sense of Sight (cont’d.) © 2010 Delmar, Cengage Learning 88 © 2010 Delmar, Cengage Learning 89 Vision: Internal eye structures • Inner neural layer: – Retina: Contains the photoreceptors • Rods: non-color, low light stimulus, crude image. Located in nearly all areas of retina • Cones: color, high light stimulus, detailed image. Located primarily in the macula region but randomly scattered throughout retina © 2010 Delmar, Cengage Learning 90 Vision:Internal eye structure – Macula lutea: area of best visual acuity- high concentration of cones. Located directly opposite the pupil. The fovea centralis is a depression in the center – Optic disc: lacks photoreceptors, no light can be detected (blind spot) where the beginning of the optic nerve is. • Optic nerve (CN II): transmits information from the eye to the brain. • Optic fluids: – Aqueous humor: between cornea & lens – Vitreous humor: gelatinous mass between lens and retina © 2010 Delmar, Cengage Learning 91 © 2010 Delmar, Cengage Learning 92 Vision: • As light enters the eye, refraction occurs> REFRACTION is a bending of light which occurs as the light passes through different densities. – 60% of refraction caused by the cornea, this is fixed and cannot be changed without reshaping the cornea. – 40% of refraction takes place in the lens, this is adjustable. • Accommodation: changing the shape of the lens to adjust focusing • Image which eye detects is upside down and backward (inverted) due to refraction. © 2010 Delmar, Cengage Learning 93 © 2010 Delmar, Cengage Learning 94 Disorders of the eye: • Myopia: nearsightedness – Focal point in front of the retina • Hyperopia: farsightedness – Focal point is behind the retina • Presbyopia: old age –loss of accommodation so it is difficult to focus on near objects • 20/20 vision means at 20 feet you are seeing what a normal eye can see at 20 feet. • 20/30 means at 20 feet, you are seeing what the normal eye would see at 30 feet away (you need to be 10 feet closer!) © 2010 Delmar, Cengage Learning 95 MYOPIA Presbyopia corrected With glasses © 2010 Delmar, Cengage Learning 96 The Sense of Hearing and Equilibrium • Outer ear – Auricle: external, visible, flexible part • Sound waves enter – External auditory meatus • Lined with hair and ceruminous glands which make cerumen (ear wax) – Tympanic membrane: vibrates in response to sound © 2010 Delmar, Cengage Learning 97 The Sense of Hearing and Equilibrium (cont’d.) • Structures of the ear shown in cross section © 2010 Delmar, Cengage Learning 98 The Sense of Hearing and Equilibrium (cont’d.) • Middle ear – Auditory ossicles: malleus, incus and stapes • Amplifies vibrations to oval window – Openings: oval and round windows – Eustachian tube: equalizes pressure • children have a tube parallel to the ground which means more infections: otitis media © 2010 Delmar, Cengage Learning 99 Myringotomy – drainage tube © 2010 Delmar, Cengage Learning 100 The Sense of Hearing and Equilibrium (cont’d.) • Inner ear – Cochlea: hearing • Fluid moves against round window which releases sound waves from inner ear, this also causes movement of “hair’ receptors (bends) which send impulses to the brain – Equilibrium – unconscious • Combines with visual input & info on body position • Static: vestibule • Kinetic: semicircular canals © 2010 Delmar, Cengage Learning 101 © 2010 Delmar, Cengage Learning 102