Neuroanatomy Introduction PDF

Neuroanatomy Nick Hurst  Neurological anatomy and physiology Aims and To understand the structure of a nerve cell objective Be able to explain how information is transmitted To be able to explain the development of the nervous system Be able to explai...

Neuroanatomy Nick Hurst  Neurological anatomy and physiology Aims and To understand the structure of a nerve cell objective Be able to explain how information is transmitted To be able to explain the development of the nervous system Be able to explain the organisation of the nervous system Identify regions of the brain and spinal cord and their functions Investigate the central nervous system and peripheral nervous system and how they relate to medical conditions What is the Complex!! Versatile achievement of evolution nervous Detects changes to external and internal environment system Brings appropriate responses in muscles, organs and glands Higher functions Learning/memory/cognition/self-awareness Can be damaged by inherited or developmental abnormalities, diseases or traumatic injury We still have a lot to learn!! Inherited conditions: Huntington's disease (single gene mutation) → Behavioural changes (normally 30-40yrs old) Tay-Sachs disease (degeneration of the brain) → Affects children Developmental abnormalities Spina bifida (Spinal cord doe not form properly) Microcephaly (Brain growth inhibited) Diseases Alzheimers Bells Palsy Epilepsy MS  Basic structure and functional unit of the Nervous System is the nerve cell – NEURONE Human body contains 1010 (100,000,000,000) Neurone Function Receive and integrate incoming information from sensory receptors or other neurones Transmit information to other neurones or EFFECTOR organs  Separate entity Highly specialised to fulfil their function Has a limiting cell membrane Neurone structure Information passed between neurones at specialist region – SYNAPSES Wide diversity of shapes and sizes of neurones All share common characteristics Single cell body Variable number of branching process DENDRITES – receptive function Majority sensory dendrites AXON – carries information away from cell body NERVE TERMINAL – end of the Axon Limiting cell membrane Semipermable K+ highly permeable Cl & Na slightly permeable Discuss myelin sheath LATER Nerve terminal = Axon terminal  Coded information – changes in electrical activity Neurone at rest Resting potential Minus 60 to 70mV Stimulated neurone Reversal in polarity of its membrane potential (Action potential) Action potential propagates down the axon Invades the nerve terminals Transmission of information Almost always by chemical means Chemicals (Neurotransmitters) stored in Synaptic Vesicles pre-synaptic endings Via the synapses – between the Axon and the Dendrite Neurotransmitters – diffuse across narrow gap of pre and post-synaptic membranes Bind to receptors in post-synaptic cell inducing changes to membrane potential Either: Depolarise membrane Hyper-polarise membrane  Myasthenia gravis: Specific conditions Autoimmune attack on postsynaptic acetylcholine receptors (destruction of them) Disrupts neuromuscular transmission Lambert-Eaton Myasthenic Trigger is unknown syndrome (LEMS) Associated with: Abnormalities in the Thymus Autoimmune hyperthyroidism Other autoimmune disorders Myasthenia gravis Presentation: Common: Ptosis Diplopia Muscle weakness after use of affected muscles Weakness resolves at rest Ocular muscles affected in 40% pts, eventually 80% Hand grip alternates between weak and normal (milkmaid’s grip) Weakened neck and limbs Bulbar symptoms Sensation and deep tendon reflexes normal LEMS: Autoimmune disease affecting voltage-gated calcium channels on the presynaptic motor nerve terminal Result – reduced acetylcholine transmitted Irregular or no muscle contractions Presentation: Proximal muscle weakness/affected gait Respiratory and bulbar muscles usually spared Depressed tendon reflexes Initial presentation similar to myasthenia gravis  Neuroglia cells (or Glia) No direct role in information processing Essential for normal functioning of the neurone 3 main types Other major Oligodendroglia (Oligodendrocytes) – Form the Myelin sheath Assist with increasing rate of conduction of action potential Astroglia (Astrocytes) – Believed to form the “blood-brain barrier” cells of the Microglia – Phagocytic role in local tissue response to nervous system damage nervous Blood brain barrier High density cells restricting passage of substances from system bloodstream in other parts of the body. Separates blood from cerebrospinal fluid Phagocytes – ingest harmful foreign bodies Microglia - these cells mediate immune responses in the central nervous system by acting as macrophages, clearing cellular debris and dead neurons from nervous tissue through the process of phagocytosis (cell eating)  Afferent Neurones – Carry information from peripheral receptors to the CNS If information reaches a conscious level – Sensory neurones Efferent Neurones – Carry impulses away from the CNS If innovert skeletal muscle – Motor Neurones Interneurones – Vast amount of neurones located entirely within CNS Picture: https://neupsykey.com/introduction-and-overview/  Development https://www.youtube.com/watch?v=Tp25wrm- of the nervous AoA&feature=youtu.be system Week 3: Week 5: Week 7: Outer layer of grey matter Divides into 2 (Cerebral Cortex) Telencephalon cerebral hemispheres Prosencephalon Inner mass of white matter (Cerebrum/ forebrain) Diencephalon Contains mainly the Thalamus Ectoderm Mesencephalon Stays relatively undifferentiated (Midbrain) (surrounded by grey matter) Metencephalon Pons Rhombenciephalon Cerebellum (Hindbrain) Myelencephalon Medulla oblongata (Medulla)  Brain stem = Medulla, Pons and midbrain Central cavity develops into system of chambers – Ventricles Contains Cerebrospinal fluid (CSF) What is CSF? Ventricles – - 4 chambers - Communicating network of cavities - Located in brain parenchyma (The brain parenchyma refers to the functional tissue in the brain that is made up of the two types of brain cell, neurons and glial cells. Damage or trauma to the brain parenchyma often results in a loss of cognitive ability or even death) - Continues with central canal and spinal cord - Lined with Ependyma (special form of epithelium) - a thin membrane of glial cells lining the ventricles of the brain and the central canal of the spinal cord. - Concerned with production and circulation of CSF Picture: https://www.pinterest.co.uk/pin/378513543657940374/  Acts as a cushion – basic mechanical and immunological barrier Produced by Choroid Plexus (1 in each ventricle) 150ml volume (produced several times a day) Reabsorbed at Arachnoid villi – increased hydrostatic pressure here in subarachnoid space Hydrocephalus – obstruction of flow of CSF within ventricular system Causes? Treatment? Hydrocephalus Causes: Cerebral Aquired: Bleeding (subarachnoid haemorrhage) Venus thrombosis (Blood clots) Spinal Fluid Meningitis Brain tumours Head injury Congenital: With Spina bifida Some babies have bleeding on the brain causing it Arachnoid cysts – between brain and arachnoid membrane Treatments: Surgery Shunt – brain to tummy – reabsorb into circulatory system Endoscopic Third Ventriculostomy (ETV) – Make hole in brain – CSF flows out to surface of brain and reabsorbed  Grey matter – Enriched with nerve cell bodies eg. Central portion of spinal cord, surface of cerebral hemisphere White matter – Mostly nerve processes (usually axons) Usually myelinated (covered in myelin – pale in colour) 1 = Right side cerebral hemisphere 2 = Grey matter 3 = White matter Nuclei – Nerve cells bodies with similar anatomical connections and functions ie. Motor neurones innovating related muscles tend to be located in groups Picture: http://w-radiology.com/white-gray-matter.php Picture: https://neupsykey.com/introduction-and-overview/ Organisation of the nervous system Nervous system Central nervous system Peripheral nervous system (CNS) (PNS) Brain Spinal Cord Cranial Nerves Spinal nerves Cervical Sacral Thoracic Lumbar  Automatic Nervous System (ANS) Present in both CNS and PNS Neurones that detect changes in and control activity of the viscera Innovate smooth muscle, cardiac muscle and secretory glands Automatic Nervous System Sympathetic Has opposite effects of functions Parasympathetic  Sympathetic – “Fight or flight” Principally release ‘Noradrenaline’ – Prolonged activation release ‘Adrenaline’ from Adrenal Medulla Binds to adrenergic receptors on peripheral tissue → pupil dilation, increased sweating, heart rate and BP Parasympathetic – “Rest and digestive system” Conserves energy, Decreased Heart rate, Increased intestinal and gland activity and relaxes sphincter muscle in GI tract Acetylcholine (Ach) is the neurotransmitter Acts on muscarinic and nicotinic receptors M2 muscarinic receptors – in heart activated →slows heart down M3 muscarinic receptors → vasodilation and decreased BP  Central Nervous System (CNS) Coverings of brain and spinal cord Bones of skull and vertebral column 3 layers = meninges (dura mater, Arachnoid, Pia mater) Periosteal dura mater – link skull to duramater Dura mater – loose fitting bag Arachnoid mater – reabsorbs CSF Pia mater – Microscopic thickness adhered to brain and spinal cord Subarachnoid space – CSF flows in this space Bleed in this space – subarachnoid bleed – uncommon type of CVA Meningitis – Acute inflammation of meninges Causes – common viral, but can be bacterial, rarely fungal Symptoms – Fever, headache, neck stiffness, confusion, altered LOC In 205 – 8.7 million cases worldwide Picture:https:// www.tho ughtco.com/brain-anatomy-men in ges-4018883  Blood supply to the brain Supplied by: Internal carotid (from common carotid artery) Vertebral arteries (from subclavian artery) Circle of Willis https://neupsykey.com/introduction-and-overview/ https://www.s cienceabc.com/ humans/ circle-of-willis-anatomy-diagram-and-functions.html  Venous drainage of the brain No valves Deep cerebral veins forebrain Superficial veins Lie in subarachnoid space Dural venous sinuses Deep and superficial veins drain in to this Internal jugular vein : https://www.s lides hare.net/indiandentalacademy/veins-of-head-neck-ppt  Brain stem https://www.youtube.com/watch?v=T2zjlB4ctu4 Picture: http://pmcanatomy.blogspot.com/2014/02/brainstem-neuroanatomy.html  Most important part of the brain Transfers messages to and from the thalamus and spinal cord Medulla Involuntary functions Such as? Oblongata Sensory and motor neurons from forebrain and midbrain travel through medulla Regulates: 3 sections Breathing Caudal medulla Heart Blood vessels Mid-medulla Digestion Rostral medulla Sneezing Swallowing Rostral medulla – Dorsal aspect floor of 4th ventrical (“Area Postrema”) 4 cranial nerves originate Blood-brain barrier absent at this point Glossopharyngeal nerve (CN IX) Vagus nerve (CN X) Accessory nerve (CN XI) Hypoglossal nerve (CN XII)  2.5cm long Pons Specific function Sort and relay messages between different sections of the brain Contains nuclei – 4 cranial nerves originate Trigeminal nerve (CN V) Abducens nerve (CN VI) Facial nerve (CN VII) Vestibulocochlear nerve (CN VIII) Associated with: Respiration eye movement Swallowing facial expression Bladder control facial sensation Hearing posture Equilibrium sleep Taste  Function for motor movement Midbrain Particularly eye movement and auditory and visual processing Divided into 2 sections Dorsal portion – Tectum Contains Inferior Colliculi and Superior Colliculi (part of visual system) Ventral portion – Tegmentum Contains Trochlear and Oculomotor nuclei 2 cranial nerves originate (III and IV)  Complex matrix of neurones Extends throughout length of brain stem Widespread afferent and efferent connections Has long axons Reticular Necessary for survival! Formation Controls: Level of consciousness Cardiovascular system Respiratory system Long axons allow profuse interaction with other neuronal systems Allow for rapid transmission of signals https://s tudy.com/academy/ les son/reticular-formation-definition-functions-quiz.h tml  Main function – process information to and from the Thalamus spinal cord and cerebellum Surrounded by cerebral hemispheres Size of a small hens egg! (5-7cm) Largest component of the dicephalon Supplied by blood by 4 branches of the posterior cerebral artery Polar artery Thalomo-gericulate artery Posterior choroidal arteries Thalamic-subthalamic arteries Myelinated nerve fibres “Lamellae” separate thalmus into individual sections Benefits – increased rate of conduction of action potential → increased speed of information transfer https://www.s ciencedirect.co m/topics/ neuroscience/posterior-cerebral-artery Brain stem lesions Unilateral brain stem lesion Causes: CVA, tumour, MS Outcome: Ipsilateral cranial nerve dysfunction Contralateral spastic hemiparesis Hyperreflexia and extensor plantar response Contralateral hemisensory loss Bilateral lesions Destroys vital centres for respiration and circulation →coma and death https://www.grepmed.com/images/3568/brownsequard-patterns-loss-diagnosis-bilaterality-neurology-sens ory Picture: https://www.neuropsychotherapist.com/the-limbic-system/ Limbic system AC Anterior commissure AN Anterior nucleus of thalamus DG Dentate gyrus FR Fasciculus retroflexus IN Interpeduncular nucleus LT Lamina terminalis MB Mammillary body MD Mediodorsal thalamic nucleus MF Medial forebrain bundle MT Mammillothalmic tract NA Nucleus accumbens OB Olfactory bulbs OC Optic chiasm OL Olfactory striae lateral OS Olfactory striae medial OT Olfactory tract PG Pituitary gland PT Paraterminal gyrus SA Subcallosal area SM Stria medullaris SN Septal nuclei SP Septum pellucidum ST Stria terminallis 4 Main structures Amygdala Hypothalamus Basal Ganglia Hippocampus  Amygdala –involved in cognitive process Episodic-autobiographical memory (EAM) Attentional and emotional processes Link to Fear, anxiety, aggression Social processing – facial evaluation Right Amygdala Left Amygdala - ? Induce negative emotions - ?induce pleasant (happiness) (fear and sadness) or unpleasant (fear, anxiety, - Role in declarative memory sadness) emotions  Hippocampus – consolidation of information for short and long term memory – Spatial memory (enable navigation) Damage to hippocampus Vast effects on overall cognitive functioning -leads to dementia (short term memory loss – inability to make new memories) - Schizophrenia and severe depression - Hippocampus has shrunk Hippocampus nerve cell before(a) and after (b) oestrogen treatment - Oestrogen effects neurological connections - Recent study shown increase in neural connections within hippocampus ?a treatment for preventing Alzheimer's? Picture: http://psycheducation.org/brain-tours/memory-learning-and-emotion-the-hippocampus/  Basal Ganglia Group of structures deep within cerebral hemispheres In the cerebrum Caudate Putamen Globus pallidus In the midbrain Substantia nigra In the diencephalon Subthalamic nucleus Collective function: facilitate movement and inhibit competing movement Ie – allow reaching and grasping and pen, Inhibiting countermovement – ie flexion Results in smooth movement Facilitate behaviours Diseases effecting basal ganglia Parkinson's disease Dopaminergic neurons of substantia nigra degenerate Contradictory movement inhibited – leads to rigidity and slow movement Huntington’s disease Globus pallidus unusually active (degeneration of the neurons) Jerky and writing involuntary movements Now being investigated to better understand Tourette’s syndrome, schizophrenia and obsessive-compulsive disorder  Ensure preservation of internal environment of the body Interoceptor signals – initial homeostatic response Hypothalamus From internal organs and body fluids 2 types of inputs Neural and circulatory Circulatory – circulating blood provides: Physical Chemical Hormonal signals Interoceptor signals = sensory signals Circulatory – circulating blood provides: Physical = Temperature, osmolaty Chemical = Blood glucose, acid base state Hormonal signals = State of the body, its growth and development, readiness for action (ie suckling, defence)  Neural – 2 sources Nucleus solitarius of the medulla to hypothalamus – signals from barorecptors and chemoreceptors Neural arousal communicated by 2 structures (in midbrain) Reticular formation (direct and indirect) Monoaminergic nuclei (via medial forebrain Hypothalamus bundle) Intimate relationship with pituitary gland Size of a pea “Master gland” Produces hormones Directs certain processes Stimulates other glands  Pituitary gland Orchestrator of the endocrine system Posterior pituitary Receives vasopressin and oxytocin from hypothalamus Anterior pituitary Produces: Adrenocorticotropic hormone Luteinising hormone Follicle-stimulating hormone Thyroid-stimulating hormone Growth hormone Prolactin  Receives vasopressin and oxytocin from hypothalamus – Produced by hypothalamus and stored in pituitary gland then released into blood stream Vasopressin – anti-diuretic hormone controls water balance and BP Oxytocin – Stimulate uterine contractions during labour and milk secretion during breast feeding Adrenocorticotropic hormone - stimulates adrenal glands to excrete steroids (ie Cortisol) Luteinising hormone and Follicle-stimulating hormone – “Gonadotrophins” – act on ovaries/testes – stimulate sex hormone production and egg and sperm maturity Thyroid-stimulating hormone – Stimulate thyroid gland to secrete thyroid hormone Growth hormone – Regulates growth, metabolism, body composition Prolactin – Stimulates milk production  Lead to under or over production of circulating hormones Growth disorders – dwarfism, gigantism Sexual dysfunction – precocious puberty Body water control – diabetes insipidus, Tumours of pathological drinking Eating – obesity, bulimia hypothalamus Adrenal cortical control – cushing’s disease, adrenal insufficiency and pituitary gland Adjacent to optic chiasma Pituitary adenomas – may lead to bitemporal visual field loss  Picture: https://www.haikudeck.com/the-brain--education-presentation-IS6ZoQ2jhq Cerebellum - Largest part of hindbrain - Connected to brain stem - Inferior, middle and superior cerebellar peduncles - Medulla, Pons and midbrain respectively - Motor function – unconscious level - Maintenance of equilibrium (balance) - Influences posture - Muscle tone - Co-ordinates movement  Midline lesion (ie tumour) Loss of postural control – topple over Unilateral cerebellar hemispheric lesion Ipsilateral incoordination Arm (intention tremor) Leg (unsteady gait_ Bilateral dysfunction (caused by alcoholic intoxication, hypothyroidism, inherited cerebellar degeneration, MS) slowness and slurring of speech (dysarthria) Lesions of the Incoordination of both arms cerebellum Staggering, wide based, unsteady gait (cerebellar ataxia) Lesion can also impair: Coordination of eye movement (Nystagmus) – common symptom of MS  Picture: https://antranik.org/the-cerebral-hemispheres/ Cerebral Hemispheres Largest part of the forebrain Superficial layer grey matter Cerebral cortex Complex patter of: Ridges (Gyri) Furrows (Sulci) Maximises surface area Extensive mass of white matter (Axons) under the surface Cerebral hemisphere divided into 4  Cerebral cortex - Forms the outer surface of the cerebral hemisphere - Several millimetres thick - Necessary for conscious awareness, thought, memory and intellect - Most sensory modalities ascend (via the thalamus) - Consciously perceived and interpreted - Highest level at which motor system is represented - Actions are conceived and initiated Functions of the lobes Frontal cerebral lesions Stroke or tumours produce 3 kinds of symptoms 1 – Focal epileptic seizures Simple focal, complex partial, generalised 2 – sensory/motor deficits 3 – Psychological deficits If focal lesion is space occupying Raised intracranial pressure