Neuroanatomy Introductory Lecture PDF

NEUROANATOM Y INTRODUCTORY LECTURE Dr. Jamal Tariq PT DPT, MS OMPT LECTURER HHIRST Recall that the main bones of the cranium are the frontal, parietal, occipital and temporal.  The floor of the cranial cavity is divided into three distinct depressions...

NEUROANATOM Y INTRODUCTORY LECTURE Dr. Jamal Tariq PT DPT, MS OMPT LECTURER HHIRST Recall that the main bones of the cranium are the frontal, parietal, occipital and temporal.  The floor of the cranial cavity is divided into three distinct depressions. They are known as the anterior cranial fossa, middle cranial fossa and posterior cranial fossa The forebrain (cerebrum) can be divided into lobes that rest in the corresponding cranial fossa. The frontal lobe lies under the frontal bone in the anterior cranial fossa, the temporal lobe lies under the temporal bone in the middle cranial fossa and the occipital lobe lies under the occipital bone in the posterior cranial fossa, along with the cerebellum. The parietal lobe lies under the parietal bone. The cerebellum (little brain) lies below the occipital lobe. It has much thinner gyri than the cerebrum Ventral view of a human brain Anterior Lateral Lateral Harvard Brain Tissue Resource Center, McLean Hospital, Belmont, MA. Posterior Dorsal view of a human brain Anterior Lateral Lateral Credit: Harvard Brain Tissue Resource Center, McLean Hospital, Belmont, MA. 1-800-BRAIN BANK Posterior Medial view of a left half brain Dorsal Anterior Posterior Credit: Harvard Brain Tissue Resource Center, McLean Hospital, Belmont, MA. 1-800-BRAIN BANK Ventral Lateral view of a left half brain Dorsal Anterior Posterior Credit: Harvard Brain Tissue Resource Center, McLean Hospital, Belmont, MA. 1-800-BRAIN BANK Ventral 2 Forebrain and Hindbrain Cerebrum (forebrain) Brainstem (hindbrain) Credit: Harvard Brain Tissue Resource Center, McLean Hospital, Belmont, MA. A fresh brain with dura removed. Note the numerous superficial blood vessels running in the arachnoid. Dorsal view Ventral view Cerebrum (forebrain) If we strip off the meninges we see the brain has a heavily folded surface or cortex (in latin: cortex =bark)  The outwardly rounded ridges of cortex are GYRI (singular GYRUS) The grooves between the gyri are SULCI (singular SULCUS)  The two main sulci are also known as fissures. These are the central sulcus (fissure) between the frontal and parietal lobes, and the lateral sulcus (fissure) between the frontal and temporal lobes Cerebral Cortex Each cerebral hemisphere is divided into:  The Cerebral Cortex Frontal (Forehead to top)  Motor Cortex Parietal (Top to rear)  Sensory Cortex Occipital (Back)  Visual Cortex Temporal (Above ears)  Auditory Cortex The lobes of the cerebral hemispheres Planning, decision Sensory making speech Vision Auditory Damage to the frontal lobes can result in Loss of simple movement of various body parts (Paralysis) Inability to plan a sequence of complex movements needed to complete multi-stepped tasks, such as making coffee (Sequencing) Loss of spontaneity in interacting with others Inability to express language (Broca's Aphasia) Loss of flexibility in thinking and persistence of a single idea or behaviour (Perseveration) Inability to focus on a task and to filter out distractions (Attention) Mood fluctuations (Emotional lability) Difficulty problem solving Difficulty inhibiting or controlling a response or impulse (Disinhibition) Reduced motivation, initiation and persistence on activities (Adynamia) Reduced awareness/insight into difficulties Changes in social behaviour Changes in personality  Damage to the Parietal lobes can result in Difficulty with drawing objects (Constructional apraxia) Difficulty in distinguishing left from right Spatial disorientation and navigation difficulties Problems with reading (Alexia) Inability to locate the words for writing (Agraphia) Difficulty with doing mathematics (Dyscalculia) Lack of awareness of certain body parts and/or surrounding space (Neglect) Inability to focus visual attention Difficulty with motor planning and complex movements(Apraxia)  Damage to the occipital lobe can include Difficulty with locating objects in environment Difficulty with identifying colours (Colour Agnosia) Production of hallucinations Visual illusions - inaccurately seeing objects Word blindness - inability to recognise words Difficulty in recognizing drawn objects Inability to recognize the movement of an object (Movement Agnosia) Difficulties with reading and writing  Damage to the temporal lobes can result in Difficulty in understanding spoken words (Receptive Aphasia) Disturbance with selective attention to what we see and hear Difficulty with identification and categorisation of objects Difficulty learning and retaining new information Impaired factual and long-term memory Persistent talking Difficulty in recognising faces (Prosopagnosia) Increased or decreased interest in sexual behaviour Emotional disturbance (e.g. Aggressive behaviour)  Motor/Sensory Cortex Contralateral Unequal representation Sensory Areas – Sensory Homunculus Figure 13.10  The Cerebral Cortex  Aphasia  impairment of language, usually caused by left hemisphere damage either to Broca’s area (impairing speaking) or to Wernicke’s area (impairing understanding)  Broca’s Area  an area of the left frontal lobe that directs the muscle movements involved in speech (they probably know what they want to say but can not articulate)  Wernicke’s Area  an area of the left temporal lobe involved in language comprehension  Language Areas wernicke broca Broca  Expression Wernicke  Comprehension and reception Aphasias LEFT HEMISPHERE  Techniques to examine functions of the brain 1. Remove part of the brain & see what effect it has on behavior 2. Examine humans who have suffered brain damage 3. Stimulate the brain 4. Record brain activity Contra-lateral division Right hemisphere controls left side of body and visual field Left hemisphere controls right side of body and visual field  Brain Plasticity The ability of the brain to reorganize neural pathways based on new experiences Persistent functional changes in the brain represent new knowledge Age dependent component Brain injuries Sensation and Perception  Sensation The process by which the central nervous system receives input from the environment via sensory neurons Bottom up processing  Perception The process by which the brain interprets and organizes sensory information Top-down processing  The five major senses Vision – electromagnetic – Occipital lobe Hearing – mechanical – Temporal lobe Touch – mechanical – Sensory cortex Taste – chemical – Gustatory insular cortex Smell – chemical – Olfactory bulb  The sixth sense And the seventh…and eighth…and ninth…. Vestibular  balance and motion – Inner ear Proprioceptive  relative position of body parts – Parietal lobe Temperature  heat – Thermoreceptors throughout the body, sensory cortex Nociception  pain – Nociceptors throughout the body, sensory cortex  The Retina The retina at the back of the eye is actually part of the brain! Rods – brightness Cones – color  Damage to the brain stem can result in: Decreased vital capacity in breathing, important for speech Swallowing food and water (Dysphagia) Difficulty with organisation/perception of the environment Problems with balance and movement Dizziness and nausea (Vertigo) Sleeping difficulties (Insomnia, Sleep apnoea) Locked-in syndrome Death  Cerebellum The cerebellum (Latin for little brain) is located just above the brain stem and tucked underneath the cerebral cortex towards the back of the brain. It is involved in the co-ordination of voluntary motor movement, balance and equilibrium and muscle tone. It is relatively well protected from trauma compared to the frontal and temporal lobes and brain stem.  Damage to the cerebellum can cause: Loss of ability to co-ordinate fine movements Loss of ability to walk Inability to reach out and grab objects Tremors Dizziness (Vertigo) Slurred Speech (Dysarthria) Inability to make rapid movements  The Limbic System Hypothalamus, pituitary (growth and metabolism), amygdala, and hippocampus all deal with basic drives, emotions, and memory Hippocampus  Memory processing Amygdala  Aggression (fight) and fear (flight) Hypothalamus  Hunger, thirst, body temperature, pleasure; regulates pituitary gland (hormones)  The Limbic System  Hypothalamus  neural structure lying below (hypo) the thalamus; directs several maintenance activities  eating  drinking  body temperature  helps govern the endocrine system via the pituitary gland  linked to emotion  The Limbic System Amygdala – two almond-shaped neural clusters that are components of the limbic system and are linked to emotion and fear  Thalamus located on top of the brainstem, a joined pair of egg-shaped structures, Receives sensory info, routes it to higher brain regions that deal with seeing, tasting, touching etc. directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla – the brain’s sensory switchboard, located on top of the brainstem – it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla SUMMARY Note appearance of cerebellum; the gyri are thinner and straighter than in cortex Most of the gyri and sulci have individual names but for now we only need to remember the central and lateral sulci. Inside the lateral fissure there is a hidden area of cortex, the insula or ‘Island of Reil’.  Insula The insular lobe is a part of the cerebral cortex located in both hemispheres. The insula forms the floor of the lateral sulcus, so in order to visualize it macroscopically, parts of the frontal, parietal and the temporal lobe must be removed. Function: desires, cravings, and addiction. Also, it has been proved that the insula plays an important role in a wide range of psychiatric disorders, such are schizophrenia, mood, panic, post-traumatic stress and obsessive-compulsive disorders. This is a brain cut in the frontal plane. Unstained brain tissue shows up as grey (actually pinky-grey) and white matter Staining the brain tissue is essential to differentiate structures. In this stain cell bodies are stained blue. Thus the cortex can be seen to contain large numbers of nerve cell bodies Grey matter = cell bodies & processes White matter = axons  Nowadays MRI enables us to see a histology-like picture in the living brain. Stained post-mortem Living The corpus callosum is the most important landmark in the brain. It is a bridge of axons that joins the two hemispheres and allows communication between them. Corpus Callosum The corpus callosum is very easy to identify in the mid- sagittal plane (below). Corpus callosum is easy to see on an MRI  The Brain’s Protective Coverings: The Meninges The Dura Mater ( Latin for “Tough mother”, as in durable) – Outermost very tough covering – Contains the venous sinuses The Arachnoid layer (Spider-like layer) – Middle, thinner layer The Sub-arachnoid space – Contains cerebro-spinal fluid and blood vessels The Pia Mater (Latin for “Tender mother”) – Inner-most delicate covering – Follows the contours of the brain closely  The Dura Mater and its Venous Sinuses Credit: Carpenter’s Human Neuroanatomy, Ninth Edition by Andre Parent. Williams and Wilkins, Publisher: 1996 The Dura Mater contains the venous sinuses. These are spaces which receive venous blood from the veins draining the brain, and which pass the blood on to the internal jugular veins.  The Arachnoid Layer Image credit:http://www.profelis.org/vorlesungen/neuroanatomy_1ns.html: 2013 Beneath the Dura Mater lies the Arachnoid Layer, the translucent milky membrane through which one can see the cerebral cortex. Beneath the Arachnoid Layer lies the sub-arachnoid space, which contains cerebro-spinal fluid and the blood vessels lying on the surface of the cerebral cortex. Cerebral Hemisphere with Blood Vessels and Pia Mater Credit: “The Human Brain” by Henri M. Duvernoy, Publisher: Springer-Verlag/Wien; 1999. Cells of the Cerebral Cortex Neurons (nerve cells) – Principle neurons Nerve cells that communicate with other neurons by exciting them. – Interneurons Inhibitory nerve cells that control principle neurons and other interneurons. Neuroglia (cells that support the neurons) – Astrocytes controls communication between neurons at synapses.. – Oligodendrocytes make myelin protein that insulates nerve cell axons – Microglia immune system surveillance cells Endothelia – cells that line the inner wall of blood vessels  The Neuron Cell Body Dendrites White Matter Credit: Santiago Ramon y Cajal: The histology of the Nervous System of Humans and Vertebrates: Publisher: Maloine, Paris, 1911 Oligodendrocyte and Nerve Cell Axons Oligodendrocytes are a type of large glial cell found in the central nervous system. Oligodendrocytes produce the myelin sheath insulating neuronal axons Credit: Samantha Barton, Nature Reviews Neuroscience. Publisher: Nature Publishing Group: 1996 Microglia are the brain’s surveillance cells. They are part of the immune system and they monitor brain tissue for signs of disease or tissue damage. When they detect a pathological change, they multiply, migrate to the diseased or damaged site, and engulf and digest the pathogens and/or cellular debris they find there, in an attempt to clear the tissue of this material. In the left hand image, microglia (stained green) surrounding blood vessels (stained red) in the retina of a mouse, search for signs of disease or cell damage. On the right are microglia (stained blue and green) surrounding and digesting the beta amyloid protein (stained red), that is found in the senile plaques of Alzheimer’s disease. THANK YOU