Neuroanatomy Lecture Notes (Fall 2024) PDF

Neuroanatomy Chapter 7  Understand the importance of neuroanatomy & anatomical vocabulary Learn the anatomy of key regions of the nervous system and their functions Protective coverings (meninges) Spinal cord & p...

Neuroanatomy Chapter 7  Understand the importance of neuroanatomy & anatomical vocabulary Learn the anatomy of key regions of the nervous system and their functions Protective coverings (meninges) Spinal cord & peripheral nervous system Ventricles Hemispheres Learning Fiber tracts Lobes objectives Motor areas Sensory areas Association areas Basal ganglia Thalamus Hypothalamus Brainstem Cerebellum :D So you don’t feel – For each region that’s in bold letters in this lecture, be able to point out *generally* where it is in the nervous system, and overwhelmed be able to give me a 2-3 word functional correlation …  – The nervous system—the importance of neuroanatomy – The structure of the nervous system tells us about brain function. Introduction – Brain organization: the mammalian plan is what we’ll focus on learning & is what’s generally considered the most “advanced”  – Medial: towards the midline – Lateral: away from the midline – Posterior/dorsal: the back – Anterior/ventral: the front Anatomical – Cranial: towards the head positions & – Caudal: towards the tail direction – Superior: towards the head – Inferior: towards the feet – Superficial: at/near/close to the surface – Deep: towards the interior of the body  Left & Right Sides Frontal or coronal Sagittal plane plane Plane is oriented parallel to Plane is oriented long axis parallel to long axis A sagittal section separates right and left portions. You A frontal, or coronal, examine a sagittal section, section separates but you section sagittally. anterior and In a midsagittal section, the posterior portions of plane passes through the the body. Coronal midline. It separates the usually refers to body into equal right and sections passing left sides. through the skull. A parasagittal section Planes and misses the midline. It Directional term: separates the body into frontally or coronally unequal right and left sides. Midsagittal plane sections Directional term: sagittally Transverse, or horizontal, plane Plane is oriented Frontal plane perpendicular to long axis A transverse, or cross, Transverse plane section separates (inferior view) Front & Back superior and inferior portions of the body. Directional term: transversely or horizontally Top & Bottom 2015 Pearson Education Inc  – Be familiar with how the anatomical directions are similar & different between us 2-legged mammals and our 4-legged Basic mammal friends (since we use so many rodent models in neuroscience research. anatomical references  – Cephalization – Evolutionary development of rostral (anterior) portion of CNS – Resulted in increased number of neurons – Highest level reached in human brain Evolution of the nervous system  – Nervous system Organization divisions of the – Central nervous system (CNS) nervous – Peripheral nervous system system (PNS)  – Central nervous system – Cerebrum, cerebellum, brain stem – Spinal cord Organization of the nervous system  Meninges – Function of meninges: – Cover and protect CNS – Protect blood vessels and enclose venous sinuses – Contain cerebrospinal fluid (CSF) – Form partitions in skull – Consists of three layers (from external to internal): dura mater, Physical arachnoid mater, and pia mater protection of the brain  – Dura mater – Thick, leathery connective tissue layers – the strongest of the meninges – Gently attaches brain to inside of skull bones – Arachnoid mater Brain – Middle layer with spiderweb-like extensions meninges: – Separated from dura mater by subdural space Dura – Subarachnoid space contains CSF and largest blood vessels of brain Arachnoid – Arachnoid granulations protrude through dura mater into superior Pia sagittal sinus – Permit reabsorption of CSF back into venous blood – Pia mater – Delicate connective tissue that clings tightly to brain, following every convolution – Contains many tiny blood vessels that feed brain  – Cerebrospinal fluid (CSF) forms a liquid cushion of constant volume around brain – Functions – Gives buoyancy to CNS structures – Reduces weight of brain by 97% by floating it so it is not crushed under its Cerebrospinal own weight Fluid (CSF) – Protects CNS from blows and other trauma – Nourishes brain and carries chemical signals – Composed of watery solution formed from blood plasma, but with less protein and different ion concentrations from plasma  – Choroid plexus: cluster of capillaries that hangs from roof of each ventricle, enclosed by pia mater and surrounding layer of ependymal cells – CSF is filtered from plexus at constant rate Cerebrospinal – Ependymal cells use ion pumps to control fluid (CSF) composition of CSF and help cleanse CSF by removing wastes – Cilia of ependymal cells help to keep CSF in motion – Normal adult CSF volume of ~150 ml is replaced every 8 hours  – Choroid plexus: cluster of capillaries that hangs from roof of each ventricle, enclosed by pia mater and surrounding layer of ependymal cells – CSF is filtered from plexus at constant rate Cerebrospinal – Ependymal cells use ion pumps to control fluid (CSF) composition of CSF and help cleanse CSF by removing wastes – Cilia of ependymal cells help to keep CSF in motion – Normal adult CSF volume of ~150 ml is replaced every 8 hours  – Issues with the brain meninges can lead to: – Meningitis: inflammation of the meninges – May spread to CNS, which would lead to inflammation of the brain, referred to as encephalitis – Meningitis is usually diagnosed by observing Clinical microbes in a sample of CSF obtained via lumbar puncture connection: – Problems with CSF circulation can lead to: brain – Hydrocephalus: obstruction blocks CSF circulation or drainage, resulting in increased meninges & pressure CSF – In newborns, skull bones are unfused, so increased pressure causes head to enlarge – In adults, rigidity of the skull keeps pressure within, potentially leading to brain damage – Can compress blood vessels and crush soft nervous tissue – Treatment is to drain CSF with ventricular shunt to abdominal cavity  – Spinal cord – Location: attached to the brain stem – Conduit of information (brain–body) Spinal cord – Skin, joints, muscles – Spinal nerves – Dorsal root – Sensation – Ventral root – Motor control  – Peripheral nervous system – Nervous system outside the brain and spinal cord – Somatic PNS: innervates skin, joints, muscles – Dorsal root ganglia: clusters of neuronal cell bodies outside the spinal cord that contain somatic sensory axons Peripheral – Visceral PNS: innervates internal organs, blood nervous vessels, glands system  – Gray matter: short, nonmyelinated neurons and cell bodies – White matter: myelinated and nonmyelinated axons – Basic pattern found in CNS: central cavity surrounded by gray matter, with Gray and white matter external to gray matter white matter organization in the brain  – Fluid-filled chambers that are continuous to one another and to central canal of spinal cord – Filled with cerebrospinal fluid (CSF) – Lined by ependymal cells (neuroglial cells) – Paired lateral ventricles are large, C-shaped chambers located deep in each hemisphere Ventricles  – Each lateral ventricle is connected to the third ventricle via interventricular foramen – Third ventricle lies in diencephalon – Third ventricle is connected to the fourth ventricle via cerebral aqueduct – Fourth ventricle lies in hindbrain – Continuous with central canal of spinal cord – Three openings connect fourth ventricle to subarachnoid space that surrounds brain: Ventricles  – Cerebral hemispheres form superior part of brain – Account for 83% of brain mass Cerebral – Surface markings: – Gyri: ridges hemispheres – Sulci: shallow grooves (aka right side – Fissures: deep grooves – Longitudinal fissure & left side) – Separates two hemispheres – Transverse cerebral fissure – Separates cerebrum and cerebellum  – Cerebral hemispheres form superior part of brain – Account for 83% of brain mass – Surface markings: – Gyri: ridges Cerebral – Sulci: shallow grooves hemispheres – Fissures: deep grooves – Longitudinal fissure – Separates two hemispheres – Transverse cerebral fissure – Separates cerebrum and cerebellum  – Several sulci divide each hemisphere into five lobes – Frontal – Parietal – Temporal Cerebral – Occipital – Insula hemispheres – First four are named after overlying skull bones – Insular lobe is buried under portions of temporal, parietal, and frontal lobes  – Several sulci divide each hemisphere into five lobes – Frontal – Parietal – Temporal Cerebral – Occipital – Insula hemispheres – First four are named after overlying skull bones – Insular lobe is buried under portions of temporal, parietal, and frontal lobes  – Major sulci that divide lobes: – Central sulcus separates precentral gyrus of frontal lobe Major sulci of and postcentral gyrus of parietal lobe the brain – Parieto-occipital sulcus separates occipital and parietal lobes – Lateral sulcus outlines temporal lobes  – Each hemisphere has three basic regions: Cerebral – Cerebral cortex of gray matter superficially hemispheres – White matter internally – Basal nuclei deep within white matter  – Second of the three basic regions of cerebral hemispheres – Responsible for communication between cerebral areas, and between cortex and lower CNS – Consists of myelinated fibers bundled into large tracts – Classified according to direction they run: – Association, commissural, and projection fibers Fiber tracts of the cerebral hemispheres  – Association fibers: horizontal running fibers that connect different parts of same hemisphere – Corpus callosum / commissural fibers: horizontal fibers that connect gray matter of two hemispheres (what’s cut in a lobotomy) – Projection fibers: vertical fibers that connect hemispheres with lower brain or spinal cord – Internal capsule: projection fibers on each side of brain stem form compact band – Passes between thalamus and some of basal nuclei Fiber tracts of – Corona radiata: projection fibers that radiate through cerebral white matter to cortex the cerebral hemispheres  – Cerebral cortex is “executive suite” of brain – Site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory Cerebral storage, understanding cortex – Thin (2–4 mm) superficial layer of gray matter – Composed of neuron cell bodies, dendrites, glial cells, and blood vessels, but no axons – 40% of mass of brain  – Four general considerations of cerebral cortex: 1. Contains three types of functional areas: – Motor areas: control voluntary movement Cerebral – Sensory areas: conscious awareness of sensation cortex 2. – Association areas: integrate diverse information Each hemisphere is concerned with contralateral (opposite) side of principles 3. body Lateralization (specialization) of cortical function can occur in only one hemisphere 4. Conscious behavior involves entire cortex in one way or another  – Located in frontal lobe, motor areas act to control voluntary movement – Primary motor cortex in precentral gyrus – Premotor cortex anterior to precentral gyrus – Broca’s area anterior to inferior premotor area – Frontal eye field within and anterior to premotor cortex; superior to Broca’s area Motor areas of the cerebral cortex  – Primary (somatic) motor cortex – Located in precentral gyrus of frontal lobe – Pyramidal cells: large neurons that Primary allow conscious control of precise, skilled, skeletal muscle movements motor cortex – Somatotopy: all muscles of body can be mapped to area on primary motor cortex – Motor homunculi: upside-down caricatures represent contralateral motor innervation of body regions  – Premotor cortex – Helps plan movements – Staging area for skilled motor activities Premotor – Controls learned, repetitious, or cortex patterned motor skills – Coordinates simultaneous or sequential actions – Controls voluntary actions that depend on sensory feedback  – Broca’s area – Present in one hemisphere (usually the left) – Motor speech area that directs muscles of speech production – Active in planning speech and voluntary motor activities – Frontal eye field Broca’s area – Controls voluntary eye movements & frontal eye fields Parasagittal view of the cerebral cortex  – Damage to areas of primary motor cortex, as seen in a stroke, paralyzes muscles controlled by those areas – Paralysis occurs on opposite side of body from damage – Muscle strength or ability to perform discrete individual movements is not impaired; only control over movements is lost – Example: damage to premotor area controlling movement of fingers would still allow fingers to move, but voluntary control needed to type would be lost – Other premotor neurons can be reprogrammed to take over skill of Clinical damaged neurons – Would require practice, just as the initial learning process did connection: motor cerebral regions  – Areas of cortex concerned with conscious awareness of sensation – Occur in parietal, insular, temporal, and occipital lobes – Eight main areas include primary somatosensory cortex, somatosensory association cortex, visual areas, auditory areas, vestibular cortex, olfactory cortex, gustatory cortex, and visceral sensory area Sensory areas of the cerebral cortex  – Primary somatosensory cortex – Located in postcentral gyri of parietal lobe Sensory – Receives general sensory information from skin and proprioceptors of areas of the skeletal muscle, joints, and tendons – Capable of spatial discrimination: cerebral identification of body region being stimulated cortex – Somatosensory homunculus: upside-down caricatures represent contralateral sensory input from body regions Body maps of the motor and somato- sensory cortices Body maps of the motor and somato- sensory cortices  – Somatosensory association cortex – Posterior to primary somatosensory cortex – Integrates sensory input from primary somatosensory cortex for understanding of object – Determines size, texture, and relationship of parts of objects being felt Sensory areas of the cerebral cortex  – Visual areas – Primary visual (striate) cortex located on extreme posterior tip of occipital lobe – Receives visual information from retinas – Visual association area surrounds primary visual cortex – Uses past visual experiences to interpret visual stimuli (color, form, or movement) – Example: ability to recognize faces – Complex processing involves entire posterior half of cerebral hemispheres Sensory areas of the cerebral cortex  – Auditory areas – Primary auditory cortex – Superior margin of temporal lobes – Interprets information from inner ear as pitch, loudness, and location – Auditory association area – Located posterior to primary auditory cortex – Stores memories of sounds and permits perception of sound stimulus Sensory areas of the cerebral cortex  – OIfactory cortex – Primary olfactory (smell) cortex – Medial aspect of temporal lobes (in piriform lobes) – Involved in conscious awareness of odors Sensory areas of the cerebral cortex  – Vestibular cortex – Posterior part of insula and adjacent parietal cortex – Responsible for conscious awareness of balance (position of Sensory head in space) – Gustatory cortex areas of the – In insula just deep to temporal lobe cerebral – Involved in perception of taste – Visceral sensory area cortex – Posterior to gustatory cortex – Conscious perception of visceral sensations, such as upset stomach or full bladder  – Damage to the primary visual cortex results in functional blindness – By contrast, individuals with a damaged visual association area can see, but they do not comprehend what they are looking at Clinical connection: damage to visual cortex  – Receive inputs from multiple sensory areas – Send outputs to multiple areas – Allows us to give meaning to information received, store in memory, tie to previous experience, and decide on actions – Sensations, thoughts, emotions become conscious: makes us who we are – Broadly divided into three parts: anterior association area, posterior Multimodal association area, and limbic system association areas of the cerebral cortex  – Prefrontal cortex – Also called anterior association area – Most complicated cortical region – Involved with intellect, cognition, recall, and personality – Contains working memory needed for abstract ideas, judgment, reasoning, persistence, and planning – Development depends on feedback from social environment – Not done developing until late 20’s, possibly early 30’s! Prefrontal cortex  – Posterior association area – Large region in temporal, parietal, and occipital lobes – Plays role in recognizing patterns and faces and localizing us in space – Involved in understanding written and spoken language (Wernicke’s area) Posterior association area  – Limbic system – Involves cingulate gyrus, parahippocampal gyrus, and hippocampus – Provides emotional impact that makes a scene important to us and helps establish memories Limbic system  – Tumors or other lesions of the anterior association area may cause mental and personality disorders, including loss of judgment, attentiveness, and inhibitions – Affected individual may be oblivious to social restraints, perhaps becoming careless about personal appearance, or take risks – Different problems arise for individuals with lesions in the part of the posterior association area that provides awareness of self in space Clinical – Individual may refuse to wash or dress the side of the body opposite to lesion because “that doesn’t belong to me” connection: damage to association areas  – Lateralization of cortical functioning – Lateralization: division of labor between hemispheres – Hemispheres are not identical – Cerebral dominance: refers to hemisphere that is dominant for language Lateralization – 90% of humans have left-sided dominance – Usually results in right-handedness of cortical – In other 10%, roles of hemispheres are reversed – Left hemisphere functioning – Controls language, math, and logic – Right hemisphere – Visual-spatial skills, intuition, emotion, and artistic and musical skills – Hemispheres communicate almost instantaneously via fiber tracts and functional integration  – A collection of various nuclei (ganglia) ocated in the very middle of the brain in a 3D, C-shaped orientiation – Each hemisphere’s basal nuclei include a: – Caudate nucleus – Putamen – Globus pallidus – Caudate nucleus + putamen = striatum Basal ganglia  – Functions of basal ganglia are thought to: – Influence muscle movements – Play role in cognition and emotion – Regulate intensity of slow or stereotyped movements – Filter out incorrect/inappropriate responses – Inhibit antagonistic/unnecessary movements – Parkinson’s disease and Huntington’s disease are disorders of the basal nuclei Basal ganglia  – Bilateral egg-shaped nuclei that form superolateral walls of third ventricle – Main thalamic function is to act as relay station for information coming into cortex – Sorts, edits, and relays ascending input such as: – Impulses from hypothalamus for Thalamus regulating emotion and visceral function – Impulses from cerebellum and basal nuclei to help direct motor cortices – Impulses for memory or sensory integration – Overall, it acts to mediate sensation, motor activities, cortical arousal, learning, and memory  – Located below thalamus – The hypothalamus is the main visceral control and regulating center that is vital to homeostasis – Chief homeostasis controls: – Controls autonomic nervous Hypothalamus system – Examples: blood pressure, rate and force of heartbeat, digestive tract motility, pupil size – Initiates physical responses to emotions (Four F’s) – Part of limbic system: perceives pleasure, fear, rage, biological rhythms, and drives (sex drive)  – Consists of three regions: midbrain, pons, medulla oblongata – Controls automatic behaviors necessary for survival – Heartbeat Brain stem – Respiration – Reflexes – Vomiting – Hiccuping – Coughing – Sneezing – Swallowing  – 11% of brain mass but contains over 50% of the neurons in the brain! – The brain’s “editor” – Located dorsal to pons and medulla – Processes input from cortex, brain stem, and sensory receptors to provide precise, coordinated movements of skeletal muscles – Also plays a major role in balance (and possibly… everything?) – Controls ipsilateral part of the body – not contralateral Cerebellum!!!  – It’s next class! A note about – Format will be multiple choice, true/false, and short answer questions your first – 40 combined MC + T/F (2 pts each) – 4 short answer (5 pts each) neuro exam – PLEASE BRING A #2 PENCIL TO THE EXAM – There will be Scantrons to fill out for the MC/TF questions Questions?