Brain and Cranial Nerves (Part 1) PDF

The Brain and cranial nerves (Part 1) Principles of Anatomy and Physiology Chapter 14 (14.1-14.5) Levels of structural organization of the nervous system 1. Chemicals 2. Cells: Neuron and neuroglia (glia) Ch. 12 3. Tissues: Nervous tis...

The Brain and cranial nerves (Part 1) Principles of Anatomy and Physiology Chapter 14 (14.1-14.5) Levels of structural organization of the nervous system 1. Chemicals 2. Cells: Neuron and neuroglia (glia) Ch. 12 3. Tissues: Nervous tissue 4. Organs: Spinal cord and brain – Ch. 13-14 5. Systems – Ch. 15-17 6. Organism  Outline (Part 1) 1. Introduction 2. Protective coverings and blood brain barrier 3. Cerebrospinal fluid (CSF) 4. Brainstem Medulla oblongata Pons Midbrain Reticular formation 5. Cerebellum 6. Diencephalon  Outline (Part 1) 1. Introduction 2. Protective coverings and blood brain barrier 3. Cerebrospinal fluid (CSF) 4. Brainstem Medulla oblongata Pons Midbrain Reticular formation 5. Cerebellum 6. Diencephalon Organization of the nervous system 1. Central Nervous System (CNS) -- Brain and Spinal cord 2. Peripheral Nervous System (PNS) Cranial nerves -- Emerge from the brain; 12 pairs Spinal nerves -- Emerge from the spinal cord; 31 pairs Brain and cranial nerves Figure 12.1  Brain The center for registering sensations, correlating them with one another and with stored information, making decisions, and taking an action Also, the center for intellect, emotions, behavior, and memory  Principal parts of the brain Medulla oblongata* Pons* Cerebellum Midbrain* Diencephalon Cerebrum * Brain stem Figure 14.1  Development of the brain Neural tube Evolution of the vertebrate brain (Midbrain) https://www.macmillanhighered.com/BrainHoney/Resou rce/6716/digital_first_content/trunk/test/hillis2e/asset/im g_ch34/c34_fig25.html  Outline (Part 1) 1. Introduction 2. Protective coverings and blood brain barrier 3. Cerebrospinal fluid (CSF) 4. Brainstem Medulla oblongata Pons Midbrain Reticular formation 5. Cerebellum 6. Diencephalon Protective coverings of the brain Cranium Cranial meninges – Connective tissue Dura mater – two layers Arachnoid mater Pia mater Cerebrospinal fluid Figure 14.2 Cranial meninges Figure 14.2  Extensions of dura mater Figure 14.2 Falx cerebri – In the longitudinal fissure; separates the two cerebral hemispheres Falx cerebelli – Separates the two cerebellar hemispheres Tentorium cerebelli – Separates the cerebrum from the cerebellum  Blood flow to the brain In adult, the brain represents only 2% of total body weight, but it utilizes about 20% of the body’s oxygen and glucose used by the body. Neurons synthesize ATP almost exclusively from glucose. Any interruption of the oxygen supply can result in weakening, permanent damage to, or death of brain cells. Glucose deficiency may produce mental confusion, dizziness, convulsions, and unconsciousness.  Blood brain barrier (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 Consists of tight junctions between endothelial cells of brain blood capillaries, and processes of astrocytes Can prevent the entry of therapeutic drugs Injury to the brain may cause a breakdown of the BBB  Outline (Part 1) 1. Introduction 2. Protective coverings and blood brain barrier 3. Cerebrospinal fluid (CSF) 4. Brainstem Medulla oblongata Pons Midbrain Reticular formation 5. Cerebellum 6. Diencephalon  Cerebrospinal fluid (CSF) Clear colorless liquid that carries oxygen, glucose, and other important substances from the blood to nervous tissue cells Total volume -- 80 to 150 ml Functions: 1. Mechanical protection for the brain and spinal cord 2. Chemical protection 3. Circulation  Choroid plexus Figure 14.4 CSF is produced at the choroid plexus in brain ventricles (20 ml/hr (480 ml/day))  Brain ventricles – (1) Figure 14.3 Lateral ventricles – Cerebral hemispheres Third ventricle – Diencephalon (Thalamus, hypothalamus) Aqueduct of the midbrain – Midbrain Fourth ventricle – Pons, Medulla oblongata, Cerebellum Central canal – Spinal cord  Brain ventricles – (2) Figure 14.3 Interventricular foramen – Between lateral ventricles and third ventricle Lateral aperture, Median aperture – Forth ventricle to subarachnoid space  CSF circulation – (1) CSF continuously circulates through the brain ventricles and central canal of the spinal cord and around the brain and spinal cord in the subarachnoid space. Figure 14.4 CSF circulation – (2) Figure 14.4  Arachnoid villi Figure 14.2 CSF is reabsorbed into the blood through arachnoid villi  Outline (Part 1) 1. Introduction 2. Protective coverings and blood brain barrier 3. Cerebrospinal fluid (CSF) 4. Brainstem Medulla oblongata Pons Midbrain Reticular formation 5. Cerebellum 6. Diencephalon  Brainstem – (1) Figure 14.1 Brainstem – (2) Figure 14.5  Outline (Part 1) 1. Introduction 2. Protective coverings and blood brain barrier 3. Cerebrospinal fluid (CSF) 4. Brainstem Medulla oblongata Pons Midbrain Reticular formation 5. Cerebellum 6. Diencephalon  Medulla Oblongata Table 14.2 Continuation of the spinal cord Figure 14.5 Contains gray matter (nuclei) and white matter (sensory (ascending) and motor (descending) tracts) Structures in the medulla oblongata Gray matter: Cardiovascular center Medullary respiratory center Reflex centers for vomiting, coughing, swallowing (deglutition), sneezing, etc. Olive – Inferior olivary nucleus Cranial nerve nuclei (VIII-XII) White matter: Contains all the pathways connecting the brain and spinal cord Pyramids  Pyramids Anterior protrusions of white matter Figure 14.6 Corticospinal tracts – Control voluntary movement of limb and trunk muscles (Pyramidal pathway) Pyramidal decussation – 90% of the corticospinal axons cross the midline. The brain controls voluntary movement of the opposite side of the body. The name of tracts consists of two components: First component – Origin Second component – Termination e.g., Cortico-spinal tract -- from the cerebral cortex to the spinal cord Cerebello-cortical tract -- from the cerebellum to the cerebral cortex  Olive Inferior olivary nucleus Project axons to the cerebellum – Modulate cerebellar functions Figure 14.6 External view of medulla oblongata Olive Pyramids Central medulla oblongata http://what-when- how.com/neuroscience/brainstem-i-the-medulla- organization-of-the-central-nervous-system-part-2/  Outline (Part 1) 1. Introduction 2. Protective coverings and blood brain barrier 3. Cerebrospinal fluid (CSF) 4. Brainstem Medulla oblongata Pons Midbrain Reticular formation 5. Cerebellum 6. Diencephalon  Pons Table 14.2 Superior to the medulla Figure 14.5 oblongata; anterior to the cerebellum Contains gray matter (nuclei) and white matter (tracts)  Structures in the pons Adjective – Pontine Gray matter: Pontine respiratory center Pontine nuclei – Connection between cerebral cortex and cerebellar hemispheres Cranial nerve nuclei (V-VIII) White matter: Pathways connecting the brain and spinal cord Nerve fibers from the cerebral cortex to the cerebellum Central pons http://what-when- how.com/neuroscience/brainstem-ii-pons- and-cerebellum-part-2/  Outline (Part 1) 1. Introduction 2. Protective coverings and blood brain barrier 3. Cerebrospinal fluid (CSF) 4. Brainstem Medulla oblongata Pons Midbrain Reticular formation 5. Cerebellum 6. Diencephalon  Midbrain Table 14.2 Figure 14.5  Structures in the midbrain Tectum Gray matter: Substantia nigra Red nucleus Cranial nerve nuclei (III-IV) White matter: Cerebral peduncles Figure 14.7  Cerebral peduncles Figure 14.7 Nerve bundles from motor areas in the cerebral cortex to the pons, medulla oblongata, and spinal cord  Tectum Corpora quadrigemina Superior colliculus (pl. colliculi) - Visual reflex center - Involved in eye movements for tracking moving images and scanning stationary images Inferior colliculus - Part of auditory pathway Figure 14.7  Substantia nigra Figure 14.7 Neurons contain dopamine as a neurotransmitter Contains dark pigments Neurodegeneration in Parkinson’s disease  Parkinson’s disease brain Normal Degeneration of Parkinson’s dopaminergic disease neurons in substantia nigra Neuroscience: Exploring the Brain, Box 14.3, Figure A Parkinsonian gait demonstration https://www.youtube.com/watch?v=j86omOwx0Hk Gait impairments in Parkinson’s disease https://www.youtube.com/watch?v=pFLC9C-xH8E  Red nucleus Figure 14.7 Axons from the cerebellum and cerebral cortex -- Help control muscular movements Prefix “rubro-” and suffix “-rubral” are used to describe associated tracts Upper midbrain http://what-when- how.com/neuroscience/brainstem-iii-the- midbrain-organization-of-the-central-nervous- system-part-1/  Outline (Part 1) 1. Introduction 2. Protective coverings and blood brain barrier 3. Cerebrospinal fluid (CSF) 4. Brainstem Medulla oblongata Pons Midbrain Reticular formation 5. Cerebellum 6. Diencephalon  Reticular formation Scattered nuclei in the superior part of the spinal cord, brainstem, and inferior part of the diencephalon Reticular activating system (RAS) Ascending part of the reticular formation – Sensory axons to the cerebral cortex Functions – Consciousness, arousal, attention Damage to the RAS results in coma Reticular Formation Figure 14.7  Outline (Part 1) 1. Introduction 2. Protective coverings and blood brain barrier 3. Cerebrospinal fluid (CSF) 4. Brainstem Medulla oblongata Pons Midbrain Reticular formation 5. Cerebellum 6. Diencephalon  Cerebellum Table 14.2 Figure 14.5  Cerebellar functions Coordination of movements – Correct voluntary muscle contraction based on sensory data from body about actual movement Posture and balance (Equilibrium) Video: Cerebellar examination https://www.youtube.com/watch?v=4Ii_lFmd7hw  External structures of the cerebellum Vermis Cerebellar hemispheres Anterior lobe Posterior lobe Figure 14.8 Flocculo-nodular lobe Folia (sg. Folium) – narrow, leaf-like folds Cerebellar gray matter and white matter Cerebellar cortex – gray matter Arbor vitae – white matter Figure 14.8  Cerebellar peduncles Three sets of paired axon bundles that connect the cerebellum to the brainstem 1. Superior cerebellar peduncles 2. Middle cerebellar peduncles 3. Inferior cerebellar peduncles Figure 14.8  Outline (Part 1) 1. Introduction 2. Protective coverings and blood brain barrier 3. Cerebrospinal fluid (CSF) 4. Brainstem Medulla oblongata Pons Midbrain Reticular formation 5. Cerebellum 6. Diencephalon  Diencephalon Thalamus Epithalamus Hypothalamus Table 14.2  Structures in the diencephalon – (1) CEREBRUM DIENCEPHALON: Thalamus Hypothalamus Pineal gland (Part of Epithalamus) BRAIN STEM: Midbrain CEREBELLUM Pons Spinal cord Medulla oblongata (a) Midsagittal section, medial view Structures in the diencephalon – (2) Longitudinal fissure Cerebral cortex (gray matter) Lateral ventricles Thalamus Third ventricle Hypothalamus Optic tract (c) Frontal section  Thalamus Paired oval masses of gray mater with interspersed white matter The major relay station for most sensory information that reach the primary sensory cortex of the cerebrum  Thalamic nuclei Figure 14.9 Lateral geniculate nucleus – Visual impulses Medial geniculate nucleus – Auditory impulses Ventral posterior nucleus – Somatic sensations (touch, pressure, vibration, itch, tickle, temperature, pain, proprioception)  Hypothalamus Production of hormones -- Link between the nervous and endocrine systems Control of the autonomic nervous system Regulation of emotional and behavioral patterns Regulation of eating and drinking Control of body temperature Control of circadian rhythms Figure 14.10  Epithalamus Interthalamic adhesion Thalamus Hypothalamus Pineal gland Mammillary body Optic chiasm Infundibulum Pituitary gland (b) Sagittal section, magnified Pineal gland Secretes melatonin -- Endocrine organ Melatonin regulates the circadian rhythms  Pineal gland Secretes melatonin in a rhythmic pattern (low during the day and high at night) --- Endocrine system Melatonin helps regulate circadian rhythms The Brain and cranial nerves (Part 2) Principles of Anatomy and Physiology Chapter 14 (14.6-14.18)  Outline (Part 2) 7. Cerebrum Cerebral cortex Cerebral white matter Corpus striatum Limbic system 8. Cranial nerves  Outline (Part 2) 7. Cerebrum Cerebral cortex Cerebral white matter Corpus striatum Limbic system 8. Cranial nerves Cerebrum Direction terms for the cerebrum Dorsal Rostral (Anterior) Rostral Caudal Lateral Medial Lateral (Anterior) (Posterior) Ventral Caudal (Posterior) Lateral view (Left hemisphere) Dorsal view Cross sections through the brain Sections Dorsal (Superior) Coronal (frontal) Sagittal (anterior) (Posterior) (Anterior) posterior section Rostral Rostral section Caudal Horizontal section Ventral (Inferior)  The longitudinal axis of the central nervous system Dorsal (Superior) Dorsal Rostral Caudal (Anterior) (Posterior) Rostral Caudal (Anterior) (Posterior) Rostral Ventral Ventral (Inferior) Ventral Dorsal Dorsal (Anterior) (Posterior) Rostral Caudal (Anterior) (Posterior) Ventral Caudal From Principles of Neural Science (5th Ed.)  Cerebrum “Seat of intelligence” Cerebral cortex Corpus striatum Cerebral white matter  Outline (Part 2) 7. Cerebrum Cerebral cortex Cerebral white matter Corpus striatum Limbic system 8. Cranial nerves  Cerebral cortex A thin gray matter that forms the outer rim of the cerebrum Contains billions of neurons that are arranged in layers Gyri (sg. Gyrus; “ridges”) and Sulci (sg. Sulcus)/Fissures (grooves) Figure 14.11  Longitudinal fissure Longitudinal fissure separates the right and left hemispheres Figure 14.11  Lobes of the cerebral cortex Each hemisphere is divided into lobes by sulci/ fissures: Frontal lobe Insula Parietal lobe Temporal lobe Occipital lobe Figure 14.11 Major sulci/fissures separate lobes Figure 14.11 Functional areas of the cerebral cortex Motor areas – Execution of voluntary movement Primary motor cortex Broca’s area Sensory areas – Perception of sensory information Primary somatosensory cortex Primary auditory cortex Primary gustatory cortex Primary olfactory cortex Primary visual cortex Association areas – Integrative functions Wernicke’s area Somatosensory, visual & auditory association areas Primary somatosensory and primary motor cortices Figure 14.15 Major sensory areas – (1) Figure 14.15 Major sensory areas – (2) Figure 14.15  Primary motor area Primary motor cortex Central sulcus (in the precentral gyrus) ANTERIOR Left lateral view POSTERIOR  Cortical areas for speech and language Broca’s area Wernicke’s area (Language production) (Language comprehension) In most people, those areas are localized in the left hemisphere. Video: Broca’s aphasia https://www.youtube.com/watch?v=JWC-cVQmEmY Video: Wernicke’s aphasia https://www.youtube.com/watch?v=3oef68YabD0  Major functional areas of the cerebral cortex (Summary) Motor Somatosensory Taste Language comprehension Visual Language production Auditory  Outline (Part 2) 7. Cerebrum Cerebral cortex Cerebral white matter Corpus striatum Limbic system 8. Cranial nerves Types of tracts in the Cerebral white matter – (1) Association tracts – Transmit nerve impulses between cerebral gyri in the same hemisphere Commissural tracts – Transmit nerve impulses between the hemispheres Projection tracts – Transmit nerve impulses between the cortex and lower parts of the CNS Types of tracts in the Cerebral white matter – (2) Figure 14.12 Types of tracts in the Cerebral white matter – (3) Commissural fibers (Corpus callosum) Association fibers Projection fibers Lateral ventricles Third ventricle Cerebellum (a) Frontal section Major tracts in the cerebrum Figure 14.13 Corpus callosum – commissural fibers Internal capsule – projecting fibers  Outline (Part 2) 7. Cerebrum Cerebral cortex Cerebral white matter Corpus striatum Limbic system 8. Cranial nerves  Corpus striatum Nuclei deep within cerebral hemispheres (1) Lentiform nucleus (a) Globus pallidus (b) Putamen (2) Caudate nucleus Functions – “Extrapyramidal motor system” - Facilitate behavior and movements that are required and appropriate and to inhibit unwanted or inappropriate movements. - Help regulate initiation and termination of movements - Regulates muscle tone Anatomy of corpus striatum – (1) Figure 14.13 Anatomy of corpus striatum – (2) Figure 14.13  Outline (Part 2) 7. Cerebrum Cerebral cortex Cerebral white matter Corpus striatum Limbic system 8. Cranial nerves  Limbic system – “Emotional brain” In the cerebral hemispheres and diencephalon Figure 14.14 Emotions --- pain, pleasure, docility, affection, fear, anger Olfaction (smell) Memory  Outline (Part 2) 7. Cerebrum Cerebral cortex Cerebral white matter Corpus striatum Limbic system 8. Cranial nerves  Cranial nerves – (1) Anterior I. Olfactory nerve Olfactory bulb II. Optic nerve III. Oculomotor nerve IV. Trochlear nerve V. Trigeminal nerve VI. Abducens nerve VII. Facial nerve VIII. Vestibulocochlear nerve IX. Glossopharyngeal nerve X. Vagus nerve XI. Accessory nerve Posterior (b) Inferior aspect of brain XII. Hypoglossal nerve  Cranial nerves – (2) ANTERIOR I. Olfactory nerve Olfactory bulb Olfactory tract View III. Oculomotor nerve II. Optic nerve V. Trigeminal nerve IV. Trochlear nerve VII. Facial nerve VI. Abducens nerve VIII. Vestibulocochlear IX. nerve Glossopharyngeal nerve X. Vagus nerve XI. Accessory nerve XII. Hypoglossal nerve POSTERIOR (a) Cranial nerves of human brain  Olfactory (I) nerve Sensory nerve -- Olfaction (Sense of smell) Figure 14.17 Olfactory nerve Olfactory bulb Olfactory tract  Optic (II) nerve Optic nerve Optic chiasm Optic tract Figure 14.18 Sensory nerve -- Vision  Control of eye movement Cranial nerves Muscles Oculomotor (III) Superior rectus Trochlear (IV) Inferior rectus Medial rectus Abducens (VI) Lateral rectus III Superior oblique IV VI Inferior oblique III III III https://www.reddit.com/r/spongebob/comments/bl7syz/ti l_eyeballs_actually_do_have_muscles/ Oculomotor (III), Trochlear (IV), and Abducens (VI) nerves Motor nerves that control the muscles that move the eyeballs Figure 14.19 Trigeminal (V) nerve Mixed nerve Three branches 1. Ophthalmic nerve 2. Maxillary nerve 3. Mandibular nerve Somatosensory (touch, pain, thermal) information from the face Figure 14.20  Facial (VII) nerve Figure 14.21 Mixed nerve Gustatory (taste) senses from the anterior 2/3 of the tongue  Bell’s palsy Also known as acute peripheral facial palsy of unknown cause Sudden weakness in the muscles on one side of the face. Thought to be caused by swelling and inflammation of the facial (VII) nerve Symptoms usually start to improve within a few weeks, with complete recovery in c. 6 months. Vestibulocochlear (VIII) nerve Figure 14.21 Sensory nerve Two branches 1. Vestibular branch – Equilibrium (balance) 2. Cochlear branch – Hearing  Glossopharyngeal (IX) nerve Figure 14.23 Mixed nerve Gustatory senses from the posterior 1/3 of the tongue Proprioception from swallowing muscles  Vagus (X) nerve Mixed nerve The longest cranial nerve Wide distribution Main component of the parasympathetic nervous system Figure 14.24  Accessory (XI) nerve Figure 14.25 Figure 14.25 Motor nerve Movement of head and pectoral girdle (sternocleidomastoid and trapezius muscles)  Hypoglossal (XII) nerve Figure 14.26 Motor nerve Controls tongue muscles Speech, manipulation of food, and swallowing Summary of cranial nerves – (1) Summary of cranial nerves – (2)  Mnemonic Cranial nerve names Oh Once One Takes The Anatomy Final, Very Good Vacations Are Heavenly. On Occasion Our Trusty Truck Acts Funny, Very Good Vehicle Any How On Old Olympus' Towering Top, A Finely Vested German Viewed A Hawk  Mnemonic Cranial nerve functional types Some Say Marry Money, But My Brother Says Big Brains Matter More S: sensory M: motor B: both