The Brain and Cranial Nerves PDF

Principles of Anatomy and Physiology Gerard Tortora and Bryan Derrickson Sixteenth Edition Chapter 14 The Brain and Cranial Nerves This slide deck contains animations. Please disable animations if t...

Principles of Anatomy and Physiology Gerard Tortora and Bryan Derrickson Sixteenth Edition Chapter 14 The Brain and Cranial Nerves This slide deck contains animations. Please disable animations if they cause issues with your device. Copyright ©2021 John Wiley & Sons, Inc. Introduction The purpose of this chapter is to: 1. Understand how the brain is organized, protected, and supplied with blood 2. Compare and contrast the various areas of the brain and their functions 3. Discuss the functional organization of the brain 4. Learn about cranial nerve structure and function Copyright ©2021 John Wiley & Sons, 2 Inc.  Brain Organization, Protection, and Blood Supply Copyright ©2021 John Wiley & Sons, 3 Inc. Development of the Nervous System The development of the nervous system begins with a thickening of the ectoderm called the neural tube Table 14.1 Development of the Brain Copyright ©2021 John Wiley & Sons, 4 Inc.  Brain Organization The major parts of the adult brain are shown here Principal Parts of the Brain Anatomy Overview Principal Parts of the Brain Copyright ©2021 John Wiley & Sons, 6 Inc. Protection The brain is protected by: Cranial bones Cranial meninges o Pia, arachnoid, and dura mater Cranial dura mater is composed of 2 layers. External periosteal/internal meningeal (spinal only 1) Cerebrospinal fluid Copyright ©2021 John Wiley & Sons, 7 Inc. Cranial Bones and Meninges Dura mater Copyright ©2021 John Wiley & Sons, 8 Inc. Extensions of the Dura Mater Falx cerebri attaches onto the crista galla Copyright ©2021 John Wiley & Sons, 9 Inc. Blood Flow to the Brain Blood flows to the brain via the vertebral and carotid arteries and flows back to the heart via the jugular veins Circle of Willis Copyright ©2021 John Wiley & Sons, 10 Inc. Importance of Blood Flow to the Brain The brain utilizes about 20% of the body’s oxygen supply Any interruption of the oxygen supply can result in weakening, permanent damage, or death of brain cells Glucose deficiency may produce mental confusion, dizziness, convulsions, and unconsciousness Copyright ©2021 John Wiley & Sons, 11 Inc.  Brain Blood Flow The vascular endothelium around brain capillaries differs from most other organs of the body in that it forms tight junctions with the end-feet of nearby astrocytes. As a result of this unusual architecture, a blood brain barrier (BBB) is formed that serves to isolate the parenchyma of the brain from many substances in the blood that would normally be able to gain access.Encyclopedia of Life Sciences, © Wiley Blood –Brain Barrier (BBB) Copyright ©2021 John Wiley & Sons, 13 Inc. Blood –Brain Barrier (BBB) Copyright ©2021 John Wiley & Sons, 14 Inc. Blood –Brain Barrier (BBB) The BBB protects brain cells from harmful substances and pathogens by serving as a selective barrier to prevent passage of many substances from the blood into the brain The BBB can prevent the entry of therapeutic drugs Injury to the brain may cause a breakdown of the BBB, permitting the passage of normally restricted substances into the brain tissue Copyright ©2021 John Wiley & Sons, 15 Inc.  Brain Blood Flow The BBB can be used advantageously in certain pharmacological situations. For example, it is well known that certain older antihistamine drugs readily cross the BBB and cause sedation. This makes these drugs not very good antihistamines, but very helpful in cough and cold medications to induce sleep (NyQuil). Drug companies have devoted enormous resources to the development of newer 2nd and 3rd generation antihistamines that do not cross the BBB, and don’t (usually) cause somnolence – they also charge you Cerebrospinal Fluid (CSF) CSF is a liquid that protects the brain and spinal cord against chemical and physical injuries and it carries oxygen, glucose, and other important substances from the blood to nervous tissue cells Copyright ©2021 John Wiley & Sons, 17 Inc. Ventricles and the Choroid Plexus The ventricles of the brain contain CSF The choroid plexuses make CSF Copyright ©2021 John Wiley & Sons, 18 Inc. CSF Flow Copyright ©2021 John Wiley & Sons, 19 Inc. Frontal Section of the Brain and Spinal CordCranial subarachnoid space – 110 mL Spinal subarachnoid space – 25mL Lateral ventricle horn – 25 to 30 mL Third ventricle – 2-3 mL Fourth ventricle – 2- 3 mL Copyright ©2021 John Wiley & Sons, 20 Inc. _________ ___ ___ __ Production and Flow of CSF Failure of CSF to form and drain normally results in a buildup of pressure called hydrocephalus. Hydrocephalus occurs with congenital abnormalities, head injury, meningitis, and episodes of bleeding into the brain. Hydrocephaly Copyright ©2021 John Wiley & Sons, 22 Inc. Regions of the Brain Anatomy Overview The Nervous System: Overview Copyright ©2021 John Wiley & Sons, 23 Inc. The Brainstem and Reticular Formation Copyright ©2021 John Wiley & Sons, 24 Inc. The Brainstem (1 of 2) The brainstem is composed of the: Medulla oblongata Pons Midbrain Copyright ©2021 John Wiley & Sons, 25 Inc. The Brainstem (2 of 2) Anatomy Overview The Brainstem Copyright ©2021 John Wiley & Sons, 26 Inc. Medulla Oblongata (1 of 2) The medulla oblongata is continuous with the superior aspect of the spinal cord and contains portions of both motor and sensory tracts Copyright ©2021 John Wiley & Sons, 27 Inc. Medulla Oblongata (2 of 2) Cranial nerves o Vestibulocochlear (VIII) and hypoglossal (XII) Structural regions o Pyramids 90% of corticospinal axons decussate here (contralateral) o Inferior olivary nuclei Functional regions o Heart rate, respiratory rate, vasoconstriction, swallowing, coughing, vomiting, sneezing, hiccupping Copyright ©2021 John Wiley & Sons, 28 Inc. Pons (1 of 2) The pons is located superior to the medulla oblongata and it links parts of the brain with one another by way of tracts Copyright ©2021 John Wiley & Sons, 29 Inc. Pons (2 of 2) Cranial nerves o Trigeminal(V), abducens(VI), facial(VII), and vestibular branch of vestibulocochlear(VIII) Functional regions o Relays nerve impulses related to voluntary skeletal muscle movements from cerebrum to cerebellum o Pneumotaxic and apneustic areas (control of respiration) Copyright ©2021 John Wiley & Sons, 30 Inc. Midbrain (1 of 3) The midbrain is located superior to the medulla oblongata and extends from the pons to the diencephalon Copyright ©2021 John Wiley & Sons, 31 Inc. Midbrain (2 of 3) Cranial nerves = Oculomotor(III) and trochlear(IV) Structural regions o Cerebral peduncles, corpora quadrigemina, substantia nigra, red nuclei, andCopyright medial lemniscus ©2021 John Wiley & Sons, Inc. 32 Midbrain (3 of 3) Functional regions o Conveys motor impulses from the cerebrum to the cerebellum and spinal cord, sends sensory impulses from the spinal cord to the thalamus, and regulates auditory and visual reflexes Copyright ©2021 John Wiley & Sons, 33 Inc. Reticular Formation The reticular formation helps regulate muscle tone, alerts the cortex to incoming sensory signals from eyes and ears but not smell (smoke alarms should be loud), most deaths in fires is from smoke inhalation. It is responsible for maintaining consciousness and awakening from sleep, hence maintain muscle tone. Copyright ©2021 John Wiley & Sons, 34 Inc. Summary of Functions of Brainstem (1 of 3) Medulla oblongata: Contains sensory (ascending) and motor (descending) tracts. Cardiovascular center regulates heartbeat and blood vessel diameter. Medullary respiratory center (together with pons) regulates breathing. Contains gracile nucleus, cuneate nucleus, gustatory nucleus, cochlear nuclei, and vestibular nuclei (components of sensory pathways to brain). Inferior olivary nucleus provides instructions that cerebellum uses to adjust muscle activity when learning new motor skills. Other nuclei coordinate vomiting, swallowing, sneezing, coughing, and hiccupping. Contains nuclei of origin for vestibulocochlear (VIII), glossopharyngeal (IX), vagus (X), accessory (XI), and hypoglossal (XII) nerves.Copyright Reticular ©2021 John Wiley & Sons, 35 formation (also in pons, midbrain, and Inc. Summary of Functions of Brainstem (2 of 3) Pons: Contains sensory and motor tracts. Pontine nuclei relay nerve impulses from motor areas of cerebral cortex to cerebellum. Contains vestibular nuclei (along with medulla) that are part of equilibrium pathway to brain. Pontine respiratory group (together with the medulla) helps control breathing. Contains nuclei of origin for trigeminal (V), abducens (VI), facial (VII), and vestibulocochlear (VIII) nerves. Copyright ©2021 John Wiley & Sons, 36 Inc. Summary of Functions of Brainstem (3 of 3) Midbrain: Contains sensory and motor tracts. Superior colliculi coordinate movements of head, eyes, and trunk in response to visual stimuli. Inferior colliculi coordinate movements of head, eyes, and trunk in response to auditory stimuli. Substantia nigra and red nucleus contribute to control of movement. Contains nuclei of origin for oculomotor (III) and trochlear (IV) nerves. Copyright ©2021 John Wiley & Sons, 37 Inc. The Cerebellum Copyright ©2021 John Wiley & Sons, 38 Inc. The Cerebellum (1 of 3) The cerebellum occupies the inferior and posterior aspects of the cranial cavity and consists of two hemispheres and a central vermis Copyright ©2021 John Wiley & Sons, 39 Inc. The Cerebellum (2 of 3) Anatomy Overview The Cerebellum Copyright ©2021 John Wiley & Sons, 40 Inc. The Cerebellum (3 of 3) The cerebellum functions in the coordination of skeletal muscle contractions and in the maintenance and fine tune of normal muscle tone, posture, and balance. Copyright ©2021 John Wiley & Sons, 41 Inc. The Diencephalon Copyright ©2021 John Wiley & Sons, 42 Inc. The Diencephalon (1 of 2) The diencephalon is composed of the: Thalamus Hypothalamus Epithalamus Copyright ©2021 John Wiley & Sons, 43 Inc. The Diencephalon (2 of 2) Anatomy Overview The Diencephalon Copyright ©2021 John Wiley & Sons, 44 Inc. Thalamus (1 of 2) Copyright ©2021 John Wiley & Sons, 45 Inc. Thalamus – don’t need to know the parts The thalamus is located superior to the midbrain and contains nuclei that serve as relay stations for all sensory impulses (except smell) to the cerebral cortex Copyright ©2021 John Wiley & Sons, 46 Inc. Hypothalamus - don’t need to know the parts The hypothalamus is found inferior to the thalamus, has four major regions, controls many body activities, and is one of the major regulators of homeostasis. It contains axons which extend to the pituitary gland and secrete hormones. Therefore, it is considered to be a part of both the nervous and endocrine systems. Copyright ©2021 John Wiley & Sons, 47 Inc. Epithalamus The epithalamus lies superior and posterior to the thalamus and contains the pineal gland. The pineal gland secretes melatonin and the habenular nuclei are involved in olfaction. Copyright ©2021 John Wiley & Sons, 48 Inc. Circumventricular Organs (CVOs) of the Diencephalon Parts of the diencephalon, the CVOs, can monitor chemical changes in the blood because they lack a blood-brain barrier CVOs include a portion of the hypothalamus, the pineal gland, and the pituitary gland o CVOs coordinate homeostatic activities of the endocrine and nervous systems Copyright ©2021 John Wiley & Sons, 49 Inc. Summary of Functions of the Diencephalon Thalamus: Relays almost all sensory input to cerebral cortex. Contributes to motor functions by transmitting information from cerebellum and corpus striatum to primary motor cortex of cerebral cortex. Plays role in maintenance of consciousness. Hypothalamus: Controls and integrates activities of autonomic nervous system. Produces hormones, including releasing hormones, inhibiting hormones, oxytocin, and antidiuretic hormone. Regulates emotional and behavioral patterns (together with limbic system). Contains feeding and satiety centers (regulate eating), thirst center (regulates drinking), and suprachiasmatic nucleus (regulates circadian rhythms). Controls body temperature by serving as body’s thermostat. Copyright ©2021 John Wiley & Sons, 50 Epithalamus: Consists of pineal gland Inc. The Cerebrum Copyright ©2021 John Wiley & Sons, 51 Inc. The Cerebrum The cerebral cortex is composed of gray matter which contains billions of neurons o Gyri, fissures, and sulci can be identified on the cortex Deep to the cortex is white matter composed of tracts of neurons that connect parts of the brain to each other and the spinal cord o A bundle of white matter tracts called the corpus callosum connects the right and left hemispheres of the cerebrum Copyright ©2021 John Wiley & Sons, 52 Inc. Anatomical Details of the Cerebral Cortex Copyright ©2021 John Wiley & Sons, 53 Inc. Lobes of the Cerebrum The cerebrum can be divided into the: Frontal lobe Parietal lobe Temporal lobe Occipital lobe Insula Copyright ©2021 John Wiley & Sons, 54 Inc. Cerebral White Matter Tracts (Axons to & from cerebrum) Copyright ©2021 John Wiley & Sons, 55 Inc. Basal Nuclei (Corpus striatum) of the Cerebrum The basal nuclei are paired masses of gray matter in each cerebral hemisphere. Initiate/terminates movements, Suppress unwanted movements Regulates muscle tone. Copyright ©2021 John Wiley & Sons, 56 Inc. The Limbic System-emotional brain (pain/ pleasure/ docility/ anger/affection/smell/memory. The limbic system is found in the cerebral hemispheres and diencephalon Copyright ©2021 John Wiley & Sons, 57 Inc. Functional Organization of the Cerebral Cortex (1 of 2) Specific types of sensory, motor, and integrative signals are processed in certain regions of the cerebral cortex. There are: Sensory areas Motor areas Association areas Copyright ©2021 John Wiley & Sons, 58 Inc. Functional Organization of the Cerebral Cortex (2 of 2) Anatomy Overview: The Cerebral Cortex Copyright ©2021 John Wiley & Sons, 59 Inc. Functional Areas of the Cerebrum Copyright ©2021 John Wiley & Sons, 60 Inc. The Cerebrum For example, a larger region of the somatosensory area receives impulses from the lips and fingertips than from the thorax or hip. This distorted somatic sensory map of the body is known as the sensory homunculus (little man). This allows us to pinpoint (feel exactly) where somatic sensations originate. The Cerebrum The primary motor area (area 4 – located in the precentral gyrus of the frontal lobe) controls voluntary contractions of specific muscles or groups of muscles. The motor cortex also has a homunculus map, with more cortical area devoted to muscles involved in skilled, complex, or delicate movement. The Cerebrum The cerebral white matter consists primarily of myelinated axons in three types of tracts. Association tracts contain axons that conduct nerve impulses between gyri in the same hemisphere. Commissural tracts conduct nerve impulses between corresponding gyri from one hemisphere to another. Projection tracts convey impulses to lower parts of the CNS (thalamus, brain stem, or spinal cord) or visa versa. The Cerebrum The corpus callosum is one of the three important groups of commissural tracts (the other two being the anterior and posterior commissures) – it is a thick band of axons that connects corresponding areas of the two hemispheres. Through the corpus callosum, the left motor cortex (which controls the right body) is linked to the right motor cortex (which controls the left body).  The Cerebrum The outer surfaces of the gyri are not the only areas of gray matter in the cerebrum. Recall that the telencephalon consists of the cortex, and also the basal nuclei. The basal nuclei are conspicuous centers of cell bodies deep in the cortex. The 3 basal nuclei help initiate and terminate movements, suppress unwanted movements, and regulate muscle tone.  The Cerebrum The basal nuclei also control subconscious contractions of skeletal muscles. Examples include automatic arm swings while walking and true laughter in response to a joke. Summary of Functions of the Cerebrum Sensory areas of cerebral cortex are involved in perception of sensory information; motor areas control execution of voluntary movements; association areas deal with more complex integrative functions such as memory, personality traits, and intelligence. Corpus striatum helps initiate and terminate movements, suppresses unwanted movements, and regulates muscle tone. Limbic system promotes range of emotions, including Copyright pleasure,©2021 John Wiley & Sons, 67 Inc.  Hemispheric Lateralization  Although the brain is almost symmetrical on its right and left sides and shares performance of many functions, there are subtle anatomical and physiological differences between the two hemispheres.  Each hemisphere specializes in performing certain unique functions, a feature known as hemispheric lateralization. Despite some dramatic differences, there is considerable variation from one person to another. Also, lateralization seems less pronounced in females.  Hemispheric Lateralization  In most people, the left hemisphere is more important for reasoning, numerical and scientific skills, spoken and written language, and the ability to use and understand sign language.  Conversely, the right hemisphere is more specialized for musical and artistic awareness; spatial and pattern perception; recognition of faces and emotional content of language; discrimination of different smells; and generating mental images of sight, sound, touch, and taste. Hemispheric Lateralization Functional Differences between Right and Left Hemispheres Copyright ©2021 John Wiley & Sons, 71 Inc. Brain Waves The billions of communicating brain neurons constantly generate detectable signals called brain waves. Those we can more easily measure are generated by neurons close to the brain surface, mainly neurons in the cerebral cortex. Electrodes placed on the forehead and scalp can be used to make a record called an electroencephalogram. Brain Waves (1 of 2) Brain waves indicate electrical activity of the cerebral cortex. They are recorded via electroencephalogram (EEG). Copyright ©2021 John Wiley & Sons, 73 Inc. Brain Waves (2 of 2) Alpha waves occur when people are awake and resting with their eyes closed. They disappear during sleep. Beta waves appear when the nervous system is active; during periods of sensory input and mental activity Theta waves occur when children and adults experience emotional stress. Delta waves occur during deep sleep in adults and in awake infants. But in an alert adult, the Copyright ©2021 John Wiley & Sons, 74 Inc. Brain Waves Electroencephalograms are useful both in studying normal brain functions, such as changes that occur during sleep, and in diagnosing a variety of brain disorders, such as epilepsy, tumors, trauma, hematomas, metabolic abnormalities, sites of trauma, and degenerative diseases. The EEG is also utilized to determine if “life” is present, that is, to establish or confirm that brain death has occurred. Cranial Nerves Copyright ©2021 John Wiley & Sons, 76 Inc.  The Twelve Cranial Nerves Cranial Nerves Cranial Nerves Spinal Cranial C1-8, T1-12, L1-5, S1-5, Roman Numerals Designation Co1 I – XII Number 31 pairs 12 pairs Origin Spinal cord Brain Number of 2 - a dorsal and a ventral Single root root roots Most mixed; some Contents Mixed sensory only All in the Head/Neck Target Limbs/Trunk (vagus n leaves) Spinal and cranial nerves are compared in this table. The major Cranial functions of the 12 pairs of cranial Nerves nerves are detailed in the following slides. This is a picture of a masterful dissection, showing the cranial nerves in-situ (as they are “in place”). Cranial Nerves Copyright © 2017 John Wiley & Sons, Inc. All rights reserved. Cranial Nerves (1 of 8) Table 14.4 Summary of Cranial Nerves Cranial Component Principal Functions Nerve s Olfactory Special Olfaction (smell). (I) sensory Optic (II) Special Vision (sight). sensory Oculomotor Motor Movement of eyeballs and (III) (Somatic) upper eyelid. Adjusts lens for Motor near vision (accommodation). (autonomic) Constriction of pupil Trochlear Motor Somatic Movement of (IV) (Somatic) eyeballs. Copyright ©2021 John Wiley & Sons, 81 Inc. Cranial Nerves (2 of 8) Table 14.4 Summary of Cranial Nerves Cranial Components Principal Functions Nerve Trigeminal Sensory Touch, pain, and thermal (V) sensations from scalp, face, and oral cavity (including teeth and anterior two-thirds of tongue). Motor Chewing and controls middle (branchial) ear muscle. Abducens Motor Movement of eyeballs. (VI) (somatic) Copyright ©2021 John Wiley & Sons, 82 Inc. Cranial Nerves (3 of 8) Table 14.4 Summary of Cranial Nerves Cranial Components Principal Functions Nerve Facial Sensory Touch, pain, and thermal (VII) sensations from scalp, face, and oral cavity (including teeth and anterior two-thirds of tongue). Motor Control of muscles of facial (branchial) expression and middle ear muscle. Motor Secretion of tears and saliva. (autonomic) Vestibulo Special sensory Hearing and equilibrium. cochlear Copyright ©2021 John Wiley & Sons, 83 (VIII) Inc. Cranial Nerves (4 of 8) Table 14.4 Summary of Cranial Nerves Cranial Nerve Components Principal Functions Glossopharyn Sensory Taste from posterior one-third geal (IX) of tongue. Proprioception in some swallowing muscles. Monitors blood pressure and oxygen and carbon dioxide levels in blood. Touch, pain, and thermal sensations from skin of external ear and upper pharynx. Motor Assists in swallowing. (branchial) Motor Secretion of saliva. (autonomic) Copyright ©2021 John Wiley & Sons, 84 Inc. Cranial Nerves (5 of 8) Table 14.4 Summary of Cranial Nerves Cranial Components Principal Functions Nerve Vagus (X) Sensory Taste from epiglottis. Proprioception from throat and voice box muscles. Monitors blood pressure and oxygen and carbon dioxide levels in blood. Touch, pain, and thermal sensations from skin of external ear. Sensations from thoracic and abdominal organs. Motor (branchial) Swallowing, vocalization, and coughing. Motor Motility and secretion of (autonomic) digestive canal organs. Constriction of respiratory Copyright ©2021 John Wiley & Sons, passageways. 85 Inc. Cranial Nerves (6 of 8) Table 14.4 Summary of Cranial Nerves Cranial Components Principal Functions Nerve Accessory Motor (branchial) Branchial Movement of head and (XI) pectoral girdle. Hypoglossa Motor (somatic) Somatic Speech, manipulation of l (XII) food, and swallowing. Copyright ©2021 John Wiley & Sons, 86 Inc. Cranial Nerves (7 of 8) *Mnemonic for Cranial Nerves: Oh Oh Oh To Touch And Feel Very Green Vegetabl Ah! Olfactor Optic Oculomot Trochlea Trigemina Abduce Faci Vestibulocochl Glossopharyn es Accessory y or r l ns al ear geal Vagus Hypoglossa l Copyright ©2021 John Wiley & Sons, 87 Inc. Cranial Nerves (8 of 8) Anatomy Overview: The Nervous System: Overview Copyright ©2021 John Wiley & Sons, 88 Inc. Olfactory, I (1 of 2) Copyright ©2021 John Wiley & Sons, 89 Inc. Olfactory, I (2 of 2) Anatomy Overview Olfactory (I) Nerve Copyright ©2021 John Wiley & Sons, 90 Inc.  Black and white Optic, II (1 of 2) Colou r Blindspo t Copyright ©2021 John Wiley & Sons, 91 Inc. Optic, II (2 of 2) Anatomy Overview Optic (II) Nerve Copyright ©2021 John Wiley & Sons, 92 Inc. Oculomotor, III (1 of 2) Copyright ©2021 John Wiley & Sons, 93 Inc. Oculomotor, III (2 of 2) Anatomy Overview Oculomotor (III) Nerve Copyright ©2021 John Wiley & Sons, 94 Inc. Trochlear, IV (1 of 2) Copyright ©2021 John Wiley & Sons, 95 Inc. Trochlear, IV (2 of 2) Anatomy Overview Trochlear (IV) Nerve Copyright ©2021 John Wiley & Sons, 96 Inc. Trigeminal, V (1 of 2) Copyright ©2021 John Wiley & Sons, 97 Inc. Trigeminal, V (2 of 2) Anatomy Overview Trigeminal (V) Nerve Copyright ©2021 John Wiley & Sons, 98 Inc. Abducens, VI (1 of 2) Copyright ©2021 John Wiley & Sons, 99 Inc. Abducens, VI (2 of 2) Anatomy Overview Abducens (VI) Nerve Copyright ©2021 John Wiley & Sons, 100 Inc.  Facial, VII (1 of 2) CN VII is the facial nerve. It has 5 large somatic branches which innervate the muscle of facial expression. It also carries some taste sensations (anterior 2/3 of tongue). Paralysis of CN VII is called Bell’s Palsy and leads to loss of ability to close the eyes and impairment of taste and salivation. Copyright ©2021 John Wiley & Sons, 101 Inc. Facial, VII (2 of 2) Anatomy Overview Facial (VII) Nerve Copyright ©2021 John Wiley & Sons, 102 Inc. Vestibulocochlear, VIII (1 of 2) CN VIII is the vestibulocochlear nerve. From the inner ear, the vestibular component carries information on balance, while the cochlear component enables hearing. Damage of CN VIII causes vertigo, ringing in the ears, and/or deafness. Copyright ©2021 John Wiley & Sons, 103 Inc. Vestibulocochlear, VIII (2 of 2) Anatomy Overview Vestibulocochlear (VIII) Nerve Copyright ©2021 John Wiley & Sons, 104 Inc. Glossopharyngeal, IX (1 of 2) CN IX is the glossopharyngeal nerve. This nerve carries some taste sensations as well as ANS impulses to salivary glands and the mechanoreceptors of the carotid body and carotid sinus (senses changes in BP). Copyright ©2021 John Wiley & Sons, 105 Inc. Glossopharyngeal, IX (2 of 2) Anatomy Overview Glossopharyngeal (IX) Nerve Copyright ©2021 John Wiley & Sons, 106 Inc. Vagus, X (1 of 2) CN X is the vagus nerve (“the wanderer”), which carries most of the parasympathetic motor efferents to the organs of the thorax and abdomen. Copyright ©2021 John Wiley & Sons, 107 Inc. Vagus, X (2 of 2) Anatomy Overview Vagus (X) Nerve Copyright ©2021 John Wiley & Sons, 108 Inc. Accessory, XI (1 of 2) CN XI is the spinal accessory nerve. This nerve supplies somatic motor innervation to the Trapezius and Sternocleidomastoid muscles. Copyright ©2021 John Wiley & Sons, 109 Inc. Accessory, XI (2 of 2) Anatomy Overview Accessory (XI) Nerve Copyright ©2021 John Wiley & Sons, 110 Inc. Hypoglossal, XII (1 of 2) CN XII is the Hypoglossal nerve. This is a very large nerve (a lot of resources) to be devoted solely to the tongue – it takes a lot more coordination than you might guess to chew, talk, and swallow without injuring our tongue. Copyright ©2021 John Wiley & Sons, 111 Inc. Hypoglossal, XII (2 of 2) Anatomy Overview Hypoglossal (XII) Nerve Copyright ©2021 John Wiley & Sons, 112 Inc. Aging and the Nervous System Copyright ©2021 John Wiley & Sons, 113 Inc. Aging and the Nervous System Aging can result in: Loss of neurons Diminished capacity for sending nerve impulses to and from the brain Diminished ability to process information Decreased conduction velocity Slowing of voluntary motor movements Increased reflex time Degenerative changes in vision, hearing, sight, taste, smell, touch, and balance Copyright ©2021 John Wiley & Sons, 114 Inc. Cerebrovascular accident (CVA) or Stroke o Leads to death of brain cells due to lack of oxygen o 85% of strokes are ischemic (due to blood clot) o 15% of strokes are hemorrhagic (leaky or ruptured vessel) Copyright ©2021 John Wiley & Sons, 115 Inc. Transient ischemic attack (T I A) o Temporary cerebral dysfunction caused by impaired blood flow o Typically persists for 5-10 minutes o Symptoms include dizziness, weakness, numbness, etc. Copyright ©2021 John Wiley & Sons, 116 Inc.  Alzheimer’s disease o Progressive dementia, characterized by loss of reasoning and ability to care for oneself o Hallmarks include: neuronal degeneration, beta-amyloid plaques (aggregates of misfolded proteins that form in the spaces between nerve cells), neurofibrillary (Tau) tangles (aggregates of hyperphosphorylated tau protein). Copyright ©2021 John Wiley & Sons, 117 Inc. Disorders (3 of 3) Brain Tumor o Abnormal growth of brain tissue; malignant or benign o Symptoms depend on size, location and rate of growth Attention Deficit Hyperactivity Disorder (ADHD) o Learning disorder characterized by poor or short attention span, consistent level of hyperactivity and impulsiveness o Likely has a genetic component although the causes Copyright are not ©2021fully John Wileyunderstood Inc. & Sons, 118 Copyright © 2017 John Wiley & Sons, Inc. All rights reserved. Copyright © 2017