Internal Anatomy of the Brain PDF

Internal anatomy of the brain PTY213 Lecture Outline  General arrangement  Gray matter  White matter  Internal features of specific regions  A. The Brainstem 1. Medulla 2. Pons 3. Reticular Formation  B. Thalamus/ Hypothalamus  Fro...

Internal anatomy of the brain PTY213 Lecture Outline  General arrangement  Gray matter  White matter  Internal features of specific regions  A. The Brainstem 1. Medulla 2. Pons 3. Reticular Formation  B. Thalamus/ Hypothalamus  From external: the cortex to deep inside  The cortex contains neurons (grey matter),  They are interconnected to other brain areas by axons (white matter).  The cortex has a folded appearance.  A fold is called a gyrus and the valley between is a sulcus. Deep structures of the brain 4 White matter tracts connect areas of the cortex to each other. Messages can travel from one gyrus to another, from one lobe to another, from one side of the brain to the other, and to structures deep in the brain  Mid-Sagittal view 5 A midsagittal section of the brain. All four cerebral lobes are visible, as in the cingulate gyrus, which extends through the medial aspects of the frontal and parietal lobes. The corpus callosum sits beneath the cingulate gyrus. Below the cerebrum lies the midbrain, pons, medulla, and cerebellum. ‘Internal Brain Regions’ by Casey Henley is licensed under a Creative Commons Attribution Non-Commercial Share-Alike (CC BY-NC-SA) 4.0 International Licen  Mid sagittal view 6 - The diencephalon region of the brain consists of the region around the thalamus and hypothalamus - The fornix is a nerve fiber bundle allows information to cross from one hemisphere to the other - The mamillary bodies sit in the posterior part of the hypothalamus and are important for memory. - The optic nerves from the retina cross at the optic chiasm are important for vision and hearing. - the reticular formation is located throughout the brainstem. Networks within the reticular formation are important for regulating sleep and consciousness, pain, and motor control. Coronal Section View 7 Coronal sections of the brain allow deep tissue structures to be visible. - The amygdala, a region important for emotion, located in the medial temporal lobe - The regions of the basal ganglia are also visible: the striatum (which consists of the caudate and the putamen) and the globus pallidus. - The lateral ventricle sits medial to the basal ganglia and below the corpus callosum. - The third ventricle is located in the middle of the brain, inferior to the lateral ventricle. Coronal Section View 8 A coronal section taken closer to the central sulcus will make the hippocampus visible. The hippocampus is known for its role in memory and spatial awareness.  Corpus collosum 9  The Corpus Callosum is a wide band of maxon fibers that connect the two hemispheres and allow them to communicate Corpus collosum Splitting the brain = procedure in which the two hemispheres of the brain are isolated by cutting the connecting fibers (mainly those of the corpus callosum) between them. Usually done to prevent uncontrollable seizures in patients with severe epilepsy Thalamus “A mass of Grey matter” , large number of Thalamic Nuclei. A gateway between cortical grey matter and other parts of the brain A relay station, allowing fine tuning and modulation of inputs and outputs Thalamus 11  Thalamus: serves as a relay station for almost all information that comes and goes to the cortex.  It plays a role in pain sensation, attention, alertness and memory. Thalamus  Receives Sensory inputs  Sensory gating  Inputs from Cerebellum, Basal ganglia  Motor coordination  Inputs from Hypothalamus and Mammillary bodies The hypothalamus 13 1. The Hypothalamus lies below (hypo) the thalamus 2. Hypothalamus: is the master control of the autonomic system. 3. It plays a role in controlling behaviors such as hunger, thirst, sleep, and sexual response. It also regulates body temperature, blood pressure, emotions, and secretion of hormones. 4. It helps control the endocrine system by giving directions to the pituitary gland. Hypothalamus The hypothalamus lies beneath the thalamus. The Brainstem 15  The Medulla is the base of the brainstem that controls heartbeat and breathing.  Pons helps with movement and facial expression.  Reticular Formation is a nerve network in the brainstem that plays an important role in controlling arousal.  IT is responsible for automatic survival functions. Brainstem  Brainstem nuclei  Including Cranial Nerves  Transmitted tracts  Descending (motor) – CORTICOSPINAL  Ascending (sensory) – MEDIAL LEMNISCUS, SPINOTHALAMIC Brainstem  Three groups of brainstem nuclei  Cranial nerves (III to XII)  Other macroscopically discrete collections of neurons eg. Red nucleus, Olives  Reticular formation, diffuse, some of its cells form “vital centres” Pituitary gland 18  Pituitary gland: lies in a small pocket of bone at the skull base called the sella turcica.  The pituitary gland is connected to the hypothalamus of the brain by the pituitary stalk. Known as the “master gland,”  it controls other endocrine glands in the body. Pituitary gland  It secretes hormones that control sexual development, promote bone and muscle growth, and respond to stress.  Hippocampus 19 The Hippocampus processes memories.  Basal ganglia 20  Basal ganglia: includes the caudate, putamen and globus pallidus.  These nuclei work with the cerebellum to coordinate fine motions, such as fingertip movements. Basal ganglia Amygdala 21  The Amygdala consists of two almond-shaped neural clusters linked to the emotions of fear and anger. Limbic system  Collection of several structures located in the inner brain beneath the cortex  The limbic system acts as the link between higher cognitive functions, such as reasoning, and more primitive emotional responses, such as fear.  Main components  Hippocampus, fornix  Mammillary bodies  Parahippocampal, cingulate gyri  Lecture Outline  Internal features of specific regions  A. The Brainstem 1. Medulla 2. Pons 3. Reticular Formation  B. Thalamus/ Hypothalamus  C. Cerebellum  D. The Limbic System  E. CSF and ventricles  F. Meninges Cerebrum “Expanded part of forebrain” CORTEX of gray matter enclosing tracts of nerve fibres Two hemispheres connected by a “bridge”, CORPUS CALLOSUM Cavity within each hemisphere the LATERAL VENTRICLE Adjacent to the ventricles are some deep gray matter, BASAL GANGLIA  Cerebellum  “Little Brain”  Two hemispheres joined by VERMIS (worm) in the midline  Three PEDUNCLES connect it to brainstem  ANTERIOR LOBE and POSTERIOR LOBE separated by PRIMARY FISSURE ▪ Helps coordinate voluntary movements and balance. ▪ It also plays a part in memory, emotion regulation, timing, emotional modulation and sensory discrimination Brain stem Cerebellar S Peduncles M I  Anterior Lobe Posterior Lobe Flocculonodular Lobe 28 GREY MATTER WHITE MATTER Association Cortex fibres Projection Basal ganglia fibres (Diencephalon Commissural Nuclei) fibres (Brainstem nuclei) Corpus Callosum joins two sides of the brain Association fibres join different parts of the hemisphere Internal Capsule joins the cortex to brainstem and spinal cord Internal capsule Afferent – Sensory to parietal Projection lobe fibres Efferent – Motor from frontal lobe Anterior limb Consists of Genu (“knee”) Posterior limb Relation to “a hand holding a bunch of caudate flowers” nucleus Caudate N (Basal ganglia) Genu (Internal Capsule ) Lentiform N (Basal ganglia) Thalamus (Diencephalon) Head of Caudate Putamen Globus Pallidus  Diencephalon  The “unexpanded” part of forebrain, the cavity is the THIRD VENTRICLE  The THALAMUS forms the lateral wall  The roof is formed by the floor of Lateral ventricles  The floor is HYPOTHALAMUS Corpus Callosum CN P GP HT MB HC Hippocampus Fornix Midbrain  Cavity is the Aqueduct  Nuclei of CN III and IV  Superiorand inferior Colliculi Light and sound reflexes  Substantial Nigra Functionally part of basal ganglia  R = Red nucleus Sn = Substantia Nigra C = Corticospinal tract CN III, IV R R Sn C  Pons  Cavity is the FOURTH VENTRICLE  Reticular formation – Vital centres  Cranial nerve nuclei CN V CN VI CN VII CN VIII  M = Middle Cerebellar Peduncle Cs = Corticospinal Tract IV CN V, VI, VIII, VIII M M Cs Cs Medulla oblongata  Cavity is the continuation of Fourth Ventricle into Spinal Canal  Contains the PYRAMIDS (Corticospinal tract)  More laterally are the OLIVES  CN IX, X, XI and XII exit CN IX, X, XI, XII Cs = Corticospinal Tract O = Olivary Nucleus O Cs Cs  Meninges 44  The meninges are the three membranes that envelop the brain and spinal cord and separate them from the walls of their bony cases (skull and vertebral column)  three meningeal layers. From superficial to deep the meninges are the: ▪ Dura mater ▪ Arachnoid mater ▪ Pia mater The function of the meninges is to protect the brain and spinal cord from mechanical trauma, to support the blood vessels and to form a continuous cavity through which the cerebrospinal fluid (CSF) passes. Ventricles and CSF 45 ▪ The brain has hollow fluid-filled cavities called ventricles. ▪ Inside the ventricles is a ribbon-like structure called the choroid plexus that makes clear colorless cerebrospinal fluid (CSF). ▪ CSF flows within and around the brain and spinal cord to help cushion it from injury. This circulating fluid is constantly being absorbed and replenished. CSF is produced inside the ventricles deep within the brain. CSF fluid circulates inside the brain and spinal cord and then outside to the subarachnoid space. Common sites of obstruction: 1) foramen of Monro, 2) aqueduct of Sylvius, and 3) obex.