Anatomy of the Nervous System PDF

Anatomy of the Nervous System Austen Smith If the human brain were so simple that we could understand it, we would be so simple that we couldn’t. - Emerson M. Pugh 2 Resources https://bigbrainproject.org...

Anatomy of the Nervous System Austen Smith If the human brain were so simple that we could understand it, we would be so simple that we couldn’t. - Emerson M. Pugh 2 Resources https://bigbrainproject.org 3 Outline Overview Nervous system divisions Anatomical directions CNS Surface features of the Brain stem brain Forebrain Internal features of the SNS brain ANS ENS Ten Principles of Nervous System Function 4  (A) 1. CNS 2. PNS (B) 1. CNS 2. SNS 3. ANS 4. ENS 5 Dissection of the entire human nervous system, removed from the body and left intact. The dissection was done by two students at the Kirksville Osteopathic College in the 1920s. Image courtesy of the Still National Osteopathic Museum, Kirksville, Missouri 6 Flow of Neural Information Afferent Sensory Towards CNS Efferent Motor Leaves CNS (Exit) 7 Anatomical Directions Anterior Lateral Caudal Medial Coronal Posterior Dorsal Rostral Frontal Sagittal Horizontal Superior Interior Ventral 8 9  Coronal section (Frontal): Cuts on the vertical plane. 10  Horizontal section: Cuts on the horizontal plane (horizon), usually viewed from above. 11  Sagittal section: Lengthwise cut. When the cut is right down the middle it is midsagittal. 12 Protecting the CNS Layers 13 Surface Features ~ 2.5 square feet at 3mm thick 14 Surface Features 15 Surface Features Cerebral circulation Anterior cerebral artery (ACA) Middle cerebral artery (MCA) Posterior cerebral artery (PCA) Extensive branching from each of the 3 major arteries 16 Internal Features Gray matter: Predominately cell bodies & blood vessels White matter: Predominately axons (fat-sheathed, myelin) 17 Cortical Connections Anatomy: corpus callosum Body of the corpus Genu callosum Splenium Rostrum 18 Internal Features 19 Internal Features Tract = collection of nerve fibers in brain and spinal cord Nerve = bundle of fibers outside the CNS 20 Development 21 The Brainstem 1. Hindbrain 2. Midbrain 3. Diencephalon 22 1. The Hindbrain Contains: Medulla Pons Cerebellum Reticular formation 23 2. The Midbrain a) Tectum Superior colliculi Inferior colliculi b) Tegmentum Red nucleus Substantia nigra Periaqueductal gray 24 3. The Diencephalon Consists of: Hypothalamus Thalamus The between brain, which integrates sensory and motor information on its way to the cerebral cortex. 25 The Forebrain Consists of: Cerebral cortex Neocortex Allocortex Basal ganglia Limbic system (?) 26  Neocortical Layers 6 layers of gray matter 1. Different layers have different cell types. 2. Density of cells varies among layers. 3. Differences in appearance relate to function and region Korbinian Brodmann (1909) Cytoarchitectonic map: Map of neocortex based on the organization, structure, and distribution of the cells. 27 Neocortical Layers Layer IV: relatively thick in the sensory cortex and relatively thin in the motor cortex, because abundant afferent sensory information from the thalamus connects to layer IV. 28 Neocortical Layers Layers V & VI: relatively thick in the motor cortex and thin in the sensory cortex. Efferent motor information in layer V makes up the corticospinal track, connecting the motor neocortex to the spinal cord to generate movement, and layer VI connects to other cortical areas. 29 Basal Ganglia Collection of nuclei just below the white matter of the neocortex Controls voluntary and involuntary movement 30  Somatic Nervous System (SNS) Monitored and controlled by the CNS: Cranial nerves by the brain Spinal nerves by the spinal cord segments 31  Cranial Nerves # Name Name Function mnemonic mnemonic 1 Olfactory Smell On Some 2 Optic Vision Old Say 3 Oculomotor Eye movements Olympus’ Marry 4 Trochlear Eye movements Towering Money 5 Trigeminal Face Top But 6 Abducens Eye movements A My 7 Facial Face Fin Brother 8 Auditory Vestibular Hearing & balance And Says 9 Glossopharyngeal Tongue & pharynx German Big 10 Vagus Heart, viscera View Brains 11 Spinal accessory Neck movements Some Matter 12 Hypoglossal Tongue movements Hops More 32 Spinal Nerves 33  SNS Connections Law of Bell & Magendie Posterior (dorsal): Afferent, sensory Anterior (ventral): Efferent, motor 34 Autonomic Nervous system (ANS) Regulates internal functions Sympathetic system Arouses the body for action (e.g., increases heart rate and blood pressure) Mediates the fight-or-flight response Parasympathetic system Opposite of sympathetic: prepares the body to rest and digest Reverses the fight-or-flight response 35 Autonomic Nervous system (ANS) 36 Enteric Nervous System (ENS) Like the ANS, running in the background Part of the ANS, but operating independently Controlling the gut bowel motility, secretion, and blood flow to permit fluid and nutrient absorption and to support waste elimination The brain and ENS connect extensively through the ANS, especially via the vagus nerve. 37 38 Ten Principles of Nervous System Function 1. Neuronal circuits are the functional units of the nervous system 2. Sensory and motor divisions pervade the nervous system 39 Ten Principles of Nervous System Function 3. The CNS functions on multiple levels and is organized hierarchically and in parallel 4. Many brain circuits are crossed 40 Ten Principles of Nervous System Function 5. Brain functions are localized and distributed 6. The brain is symmetrical and asymmetrical 41 Ten Principles of Nervous System Function 7. The nervous system works by juxtaposing excitation and inhibition 8. The brain divides sensory input for object recognition and movement 42 Ten Principles of Nervous System Function 9. The nervous system produces movement in a perceptual world the brain constructs 10. Neuroplasticity is the hallmark function of nervous system functioning 43