15_Brain and Cranial Nerves.pptx

Central and Peripheral Nervous System Chapter 12, Human Anatomy (LibreTexts) "Figure showing the base of the brain, Thomas Geminus Wellcome" by Wellcome Collection gallery is licensed under CC BY 4.0 Gray Matter and White Matter • Based on appearance and composition, nervous tissue is divided int...

Central and Peripheral Nervous System Chapter 12, Human Anatomy (LibreTexts) "Figure showing the base of the brain, Thomas Geminus Wellcome" by Wellcome Collection gallery is licensed under CC BY 4.0 Gray Matter and White Matter • Based on appearance and composition, nervous tissue is divided into gray matter and white matter. • Gray matter is composed of cell bodies (soma) of neurons and unmyelinated axons. It is located superficial covering the entire brain, in some deep regions (nuclei) of the brain and deep in the spinal cord. • White matter is made by myelinated axons of neurons; myelin has a high fat content and looks white. White matter is located deep in the brain and superficial in the spinal cord. • Brain has four major regions: Cerebrum, Diencephalon, Brainstem, Cerebellum Gray Matter and White Matter - Image "Human Brain" by Suseno is in the Public Domain / A derivative from the original work Protection of the CNS • The CNS is protected by multiple structures: 1. Bones of the skull enclose and house the brain, while the bones of the vertebral column protect the spinal cord. 2. Meninges are membranes made by connective tissue that support, stabilize and partition the nervous tissue. 3. Cerebrospinal fluid (CSF) circulates within and around the CNS to remove waste and provide nutrients, and to cushion the CNS. 4. Blood-brain barrier forms a privileged blood supply to protect this region from toxins and pathogens. Protective Structures Subarachnoid space containing CSF "Cranial meninges" by Chiara Mazzasette is licensed under CC BY 4.0 / A derivative from the original work Cranial Meninges • Three layers, from superficial to deep: • Dura mater: Anchored the inner surface of the cranium. The cranial dura mater is made of two layers (periosteal and meningeal) and forms cranial dural sinuses and septa. The region between the bones and the dura mater is called epidural space, while the region deep to the dura mater is called the subdural space. These spaces are potential spaces. • Arachnoid mater: thin fibrous tissue that forms a loose sac around the CNS. Beneath the arachnoid is a thin, filamentous mesh called the arachnoid trabeculae within the subarachnoid space. This space is a real space and is filled with CSF. • Pia mater, a thin fibrous membrane that follows the superficial convolutions of the brain and spinal cord, and fits into other grooves and indentations. Meningeal Layers of the Brain "Meningeal Layers" by OpenStax is licensed under CC BY 4.0 Cranial Dural Septa • The meningeal layer of the dura mater extends into the cranial cavity at four locations creating flat partitions called cranial dural septa 1. Falx cerebri goes through the midline separation of the cerebrum. 2. Tentorium cerebelli separates the cerebellum from the cerebrum, forming a shelf-like tent. 3. Falx cerebelli separates the two cerebellar hemispheres. 4. Diaphragma sellae surrounds the pituitary gland. "Falx Cerebri and Tentorum Cerebelli" by Powellle is licensed under CC BY-SA 4.0 Arterial blood supply to the brain Arterial blood fills branches from the internal carotid arteries and vertebral arteries which become the circle of Willis that maintains perfusion of the brain even if narrowing or a blockage limits flow through one part. "Arteries of the Brain" by OpenStax is licensed under CC BY 3.0 Venous blood supply to the brain Venous blood returns to the circulation through a series of dural sinuses which are spaces between the two layers of the dura mater. The superior sagittal sinus runs in the medial groove of the brain and drains to the confluence of sinuses, along with the occipital sinuses and straight sinus. The confluence drains into the transverse sinuses, which then connect to the jugular veins. "Brain Sinuses" by OpenStax is licensed under CC BY 4.0 CSF and Ventricular System • Cerebrospinal fluid (CSF) is a clear liquid that circulates around and within the brain. It provides buoyancy, protection and environment stability. • CSF is produced by a type of specialized membrane made of ependymal cells called a choroid plexus. • The choroid plexus lines open spaces within the brain called ventricles. "Choroid plexus" by Anatomist90 is licensed under CC BY-SA 3.0 Ventricles "Blausen 0896 Ventricles Brain" by BruceBlaus is in the Public Domain, CC0 CSF Circulation 1. Two lateral ventricles drain CSF into the interventricular foramina connected to the third ventricle. 2. Third ventricle opens into the cerebral aqueduct, and then into the fourth ventricle. 3. Fourth ventricle drains CSF into the subarachnoid space where CSF will be reabsorbed into the dural venous sinuses and drains into the central canal of the spinal cord. Cerebrospinal Fluid Circulation "CSF Circulation" by OpenStax is licensed under CC BY 4.0 Blood-Brain Barrier • Blood brain barrier (BBB) regulates what substances can enter interstitial fluid of brain • Astrocytes contribute to the BBB by maintaining the tight junction between endothelial cells of blood vessels. • BBB is missing or reduced in three locations of CNS: • Choroid plexus • Pituitary Gland • Pineal gland • BBB dysfunction contributes to pathologies i.e. multiple sclerosis, stroke, and epilepsy, Parkinson’s and Alzheimer's disease and schizophrenia. Blood-Brain Barrier Image "Blood Brain Barriere" by Ben Brahim Mohammed is licensed under CC BY 3.0 Cerebrum • Brain has four major regions: Cerebrum, Diencephalon, Brainstem, Cerebellum • Cerebrum is composed of cerebral cortex (outer wrinkled gray matter), basal nuclei (deep regions with neurons) and tracts (inner white matter). • Cerebrum shows ridges called gyri and grooves called sulci, which can be used as landmarks. • Left and right cerebral hemispheres separated by longitudinal fissure and connected by the corpus callosum. Coronal Section of the Brain "Brain Coronal Section" by Chiara Mazzasette is licensed under CC BY 4.0 / A derivative from the original work Cerebrum – Sulci and Gyri The main sulci are: • central sulcus • lateral sulcus • parieto-occipital sulcus The main gyri are: • precentral gyrus (anterior to the central sulcus) • postcentral gyrus (posterior to the ”Brain Lateral View" by Chiara Mazzasette is a derivative from the original work of Daniel Donnelly and is licensed by CC BY 4.0 central sulcus) Superior View of the Brain ”Brain Superior View" by Chiara Mazzasette is a derivative from the original work of Daniel Donnelly and is licensed by CC BY 4.0 Cerebral Cortex • Separated into lobes: 1. Frontal lobe (anterior to central sulcus): voluntary motor function, concentration, verbal communication, decision making, planning and personality reside. 2. Parietal lobe (posterior to central sulcus): somatosensation processing 3. Temporal lobe (inferior to lateral sulcus): processing of hearing, smell, and formation of memories 4. Occipital lobe (posterior to parieto-occipital sulcus): visual processing 5. Insula (deep to lateral sulcus): taste processing, emotional responses and empathy. Lobes of the Cerebral Cortex "Lobes of Cerebral Cortex" by OpenStax is licensed under CC BY 4.0 Brodmann’s, Primary and Association Areas • Phineas Gage: the “man who began neuroscience”. The most famous patient in the annals of neuroscience, because his case was the first to suggest a link between brain trauma and personality change. • In the early 1900s, a German neuroscientist named Korbinian Brodmann divided the cerebral cortex into 52 separate regions on the basis of the histology of the cortex. The regions are called Brodmann’s areas. • Subsequent studies have demonstrated a strong correlation between the Brodmann’s areas and the functions attributed to those regions. • Primary areas are where sensory information is initially received for conscious perception, or where descending commands are sent down to the brainstem or spinal cord to execute movements. The regions near the primary areas are each referred to as association areas. Phineas Gage "Phineas Gage GageMillerPhoto2010-02-17 Unretouched Color Cropped" by Unknown is in the Public Domain Frontal Cortex – Motor Function • In the frontal lobe, there are regions that control motor functions. • In the precentral gyrus is the primary motor cortex, which instructs the spinal cord to move skeletal muscles. • Anterior to the primary motor cortex is the motor association area or premotor cortex, which aids the primary area in its function. • Anterior to the premotor cortex, the frontal eye field controls eye movements that require both eyes. • A motor homunculus shows a representation map of the regions of the body controlled by this lobe. Motor Homunculus "Motor homunculus" by Penfield and Rasmussen is licensed under CC BY-SA 4.0 Parietal Cortex - Somatosensation • In the parietal lobe, there are regions that process information related to somatosensation (touch, pressure, tickle, pain, itch, vibration, proprioception and kinesthesia). • In the postcentral gyrus is the primary somatosensory cortex. • Posterior to the primary somatosensory cortex is the sensory association area, which helps the primary area to process somatosensation. • A sensory homunculus shows a representation map of the regions of the body perceived by this lobe. Sensory Homunculus "Sensory Homunculus" by OpenStax is licensed under CC BY 3.0 Occipital, Temporal, Insular Cortex – Special Sensation • In the occipital lobe, there are regions that process visual information. In the most posterior part, the primary visual cortex receives and processes visual information. Adjacent to that are visual association areas, which constitute subsequent regions of visual processing. • In the temporal lobe are the primary auditory cortex, followed by the auditory association area, which process auditory information and the primary olfactory cortex which processes smell. • In the insula, the primary gustatory cortex is responsible for processing taste information. Cortical Areas "Types of Cortical Areas" by OpenStax is licensed under CC BY 3.0 Other Cortices – Memory, Learning, Speech • Integrative areas: areas found in between other areas and help process sensory or motor information in more complex ways. • Memory and learning are largely functions of the temporal lobe, along with structures beneath the cerebral cortex such as the hippocampus and the amygdala. • The functions of language and speech are located in the left hemisphere in two regions: Wernicke’s areas is responsible for the understanding of language, both written and verbal, and Broca’s areas is responsible for the production of language, or controlling movements responsible for speech. Broca's and Wernicke's Areas "Brocas and Wernickes Areas" by OpenStax is licensed under CC BY 3.0 Aphasia • Aphasia is a language disorder that affects a person's ability to communicate. Aphasia affects a person's ability to express and understand written and spoken language. • It can occur suddenly after a stroke or head injury, or develop slowly from a growing brain tumor or disease. • Wernicke’s Aphasia prevents a person from understanding others or themselves when speaking, and leads to words put together in a random fashion. • Broca’s Aphasia prevents a person from forming clear words or sentences but it has little or no effect on the ability to understand others when they speak. White Matter Tracts • Myelinated axons that connect different regions of the cerebral cortex to integrate information and motor response. • They can be classified into three groups: 1. Association tracts can be classified into arcuate fibers when they connect gyri of the same lobe or longitudinal fasciculi when they connect gyri in different lobes of the same hemisphere. 2. Commissural tracts extend between the two hemispheres to connect left and right regions of the cerebrum (for example the corpus callosum) 3. Projection tracts extend from the cerebral cortex to the inferior regions of the brain and to the spinal cord. White Matter Tracts - Image ”White Matter Tracts" by Chiara Mazzasette is a derivative from the original work of Daniel Donnelly and is licensed by CC BY 4.0 Hemispheric Control and Lateralization • Both cerebral hemispheres generally receive their sensory information from and project motor commands to the opposite sides of the body • The two hemispheres appear to be mirror images, but display some functional differences called hemispheric lateralization. For example, speech. • You Are Two Basal Nuclei of Cerebrum • Deep gray matter regions of the brain • Caudate, putamen and globus pallidus are deep basal nuclei in the cerebrum and are responsible for control of movement. Together, the caudate and putamen are called the striatum. Basal Nuclei - Image "Cerebral Nuclei" by Chiara Mazzasette is licensed under CC BY 4.0 / A derivative from the original work Brain - Diencephalon • The diencephalon is deep beneath the cerebrum and constitutes the walls of the third ventricle. It is where the information is sent from the rest of the nervous system into the cerebrum (except for olfaction). • Composed of: • Epithalamus forms the posterior roof of the third ventricle and houses the pineal gland, an endocrine gland responsible for the secretion of melatonin that regulates sleep-awake cycles. • Thalamus is a pair of oval-shaped structures that each contain a dozen nuclei, called thalamic nuclei. All sensory information, except for the sense of smell, passes through the thalamus before processing by the cortex. • Hypothalamus is a collection of nuclei involved in autonomic nervous system and endocrine system, in memory and emotion as part of the limbic system. Brain - Limbic System • The limbic system is a collection of structures of the cerebrum and diencephalon involved in emotion, motivation and memory associated with emotions. • The structures mostly recognized in this system are the: • Cingulate gyrus is located in the longitudinal fissure, superior to the corpus callosum, surrounding the diencephalon. • Hippocampus is a nucleus shaped like a seahorse. • Amygdala is connected to the hippocampus. Limbic System - Image "Figure 35 03 06" by OpenStax is licensed under CC BY 4.0 Brain - Brainstem • The brainstem is inferior to the diencephalon and anterior to the cerebellum. It is part of the reticular activating system, which controls levels of wakefulness. • Composed of: • Midbrain • Pons • Medulla oblongata Brainstem - Midbrain • Midbrain makes the roof and floor of the cerebral aqueduct. • In the tectum, the superior and inferior colliculi are posterior enlargements. • The substantia nigra is part of the tegmentum. Degeneration of substantia nigra causes Parkinson’s disease. • On the anterior side, the cerebral peduncles connect the cerebrum to the spinal cord, while the superior cerebellar peduncle connects the midbrain to the cerebellum. • Integrates information from cerebrum and cerebellum. Affects movement, emotional response, ability to experience pleasure and pain. Brainstem – Pons and Medulla Oblongata • Pons is main connection with the cerebellum through the middle cerebellar peduncle. • Medulla oblongata is the most inferior part of the brainstem, continuous to the spinal cord. • Anteriorly, the pyramids house motor projection tracts. • In the posterior region, these pyramids cross to the opposite side at a point called the decussation of pyramids. • Inferior to each pyramid, a nucleus called inferior olive functions as a relay point for information on proprioception going to the cerebellum through the inferior cerebellar peduncle. • Both regions regulate several crucial functions, including the cardiovascular and respiratory systems. Diencephalon and Brainstem ”Brain Midsagittal Section" by Chiara Mazzasette is a derivative from the original work of Daniel Donnelly and is licensed by CC BY 4.0 Diencephalon and Brainstem - Image ”Brain Inferior View" by Chiara Mazzasette is a derivative from the original work of Daniel Donnelly and is licensed by CC BY 4.0 Brain - Cerebellum • The cerebellum lies posteriorly to the pons. The cerebellum is responsible for coordination of movement, alternating movement of arms and legs, balance, posture and gait. • Contains an outer layer of gray matter called the cerebellar cortex, an inner layer of white matter called the arbor vitae and deep to it cerebellar nuclei. • The folds of the cerebellar cortex are called folia. • The midline region of the cerebellum is called the vermis and connects the two cerebellar hemispheres. Cerebellum - Image Arbor vitae Folia "Cerebellum" by OpenStax is licensed under CC BY 4.0 General Organization of Nerves • Nerves are bundles of axons in the PNS. • Cranial nerves originate from the brain, while spinal nerves originate from spinal cord. • Composed of nervous tissue, connective tissue and blood vessels. • Outer surface of nerve is covered by a layer of fibrous connective tissue called the epineurium. • Within the nerve, axons are further bundled into fascicles, which are each surrounded by their own layer of fibrous connective tissue called perineurium. • Finally, individual axons are surrounded by loose connective tissue called the endoneurium. Nerve Diagram "Nerve Structure" by OpenStax is licensed under CC BY 3.0/Micrograph provided by the Regents of University of Michigan Medical School 2012 Nerve Histological Picture "Nerve Structure" by OpenStax is licensed under CC BY 3.0/Micrograph provided by the Regents of University of Michigan Medical School 2012 Cranial Nerves • Nerves attached to the inferior side of the brain. Part of PNS. • 12 pairs designated as CNI to CNXII based on the anatomical location, from anterior to posterior. • Classified as sensory nerves, motor nerves, or a combination of both. • Mnemonic for names: “Ooh Ooh Ooh To Touch And Feel Very Good Velvet… Amazing Heaven” • Mnemonic for functions: “Some Say Marry Money But My Brother Says Big Brains Matter More” Cranial Nerves – List and Functions # Name Function (S/M/B) I Olfactory Smell (S) II Optic Vision (S) III Oculomotor Eye movements (M) IV Trochlear Eye movements (M) V Trigeminal Sensation of face, Movement of mastication muscles (B) VI Abducens Eye movements (M) VII Facial Movement of face, Taste (B) VIII Vestibulocochlear Hearing and balance (S) IX Glossopharyngeal Movement of throat muscles and secretion of salivary glands, Taste (B) X Vagus Sensation from most internal organs, Movement of smooth and cardiac muscles (autonomic) (B) XI Accessory Movement of muscles in head and neck (M) XII Hypoglossal Movement of tongue (M) Cranial Nerves - Image "The Cranial Nerves" by OpenStax is licensed under CC BY 4.0 Clinical Anatomy: Stroke • Stroke is a sudden interruption of the blood supply to the brain. • Ischemic strokes are caused by an abrupt blockage of an artery. • Hemorrhagic strokes are caused by bleeding into brain tissue when a blood vessel bursts. More lethal but less common. • Embolic strokes are caused by a clot breaking off from the artery wall and blocking a smaller artery. • Strokes may cause sudden weakness, loss of sensation, or difficulty with speaking, seeing, or walking. Since different parts of the brain control different areas and functions, it is usually the area immediately surrounding the stroke that is affected. Stroke - Image "Types of Stroke" by Scientific animations is licensed under CC BY-SA 4.0 Clinical Anatomy: Glioma • Glioma is a type of tumor that occurs in the glial cells of the brain or spinal cord. • A glioma can affect the brain function and be lifethreatening depending on its location and rate of growth. • Types of glioma include: • Astrocytomas, involving astrocytes • Ependymomas, involving ependymal cells • Oligodendrogliomas, involving oligodendrocytes