Cns Intro Davidson Plus1.


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Medical college lectures 5th year neurology

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Cns Intro Davidson Plus1.

  1. 1. 5 th year neurology lectures: Around 30 Lectures: 1. Dr. Mohammad Shaikhani: 8. 2. Dr. Mohammad Tahir: 7. 3. Dr. Rasul M.Hasan: 7. 4. Dr. Akram Mahdawi: 7.
  2. 2. 5 th year neurology lectures: 1 lecture/week every Saturday 8-9 AM. <ul><li>My lectures: </li></ul><ul><li>Introduction 1: anatomy/physiology. </li></ul><ul><li>Introduction 2: investigations of NS. </li></ul><ul><li>Peripheral neuropathies. </li></ul><ul><li>Myopathies. </li></ul><ul><li>Mysathenia gravis. </li></ul><ul><li>Movement disorders & parkinsonism 1. </li></ul><ul><li>Movement disorders & parkinsonism 2. </li></ul><ul><li>Multiple sclerosis. </li></ul>
  3. 3. 5 th year neurology lectures: Introduction: ANATOMY / PHYSIOLOGY: Dr. Mohammad Shaikhani. Assistant professor. M. B. Ch. B/ C.A.B.M
  4. 4. NS Cells <ul><li>The nervous system includes: </li></ul><ul><li>1.Neurons of different types. </li></ul><ul><li>2.Specialised blood vessels. </li></ul><ul><li>3.Ependymal cells lining the cerebral ventricles </li></ul><ul><li>4.Glial cells, of 3 types: </li></ul><ul><li>A. Astrocytes: form the structural framework for the neurons & control their biochemical environment&their foot processes closely associated with the blood vessels to form BBB. </li></ul><ul><li>B. Oligodendrocytes are responsible for the formation & maintenance of the myelin sheath, which surrounds axons &is essential for the rapid transmission of action potentials& myelin is also made by Schwann cells . </li></ul><ul><li>C. Microglia are blood-derived mononuclear macrophages. </li></ul>
  5. 6. GENERATION /TRANSMISSION OF NERVOUS IMPULSE <ul><li>Functioning of the NS by 2 physiological processes: </li></ul><ul><li>1.The generation of action potential with conduction down axons. </li></ul><ul><li>2.The synaptic transmission of impulses between neurons &/or muscle cells. </li></ul><ul><li>These processes depend upon the energy-demanding maintenance of an electrochemical gradient across neuron cell membranes effected by specialised ion channels in the membrane. </li></ul><ul><li>Synaptic transmission involves the release from a neuron of neurotransmitter molecules that bind to specific receptors on the membrane of the receptor cell. </li></ul><ul><li>These molecules alter either that cell's membrane potential via effects upon ion channel permeability, or its metabolic function. </li></ul><ul><li>There are > 20 different neurotransmitters known to act at different sites in the NS, all potentially amenable to pharmacological manipulation. </li></ul>
  6. 7. GENERATION /TRANSMISSION OF NERVOUS IMPULSE <ul><li>The neuronal cell bodies are acted upon by synapses with large numbers of other neurons. </li></ul><ul><li>Each neuron therefore acts as a microprocessor, reacting to the influences upon it by changes to its cell membrane potential, causing it to be more or less ready to discharge an impulse down its axon(s). </li></ul><ul><li>The synapsing neuron terminals are also subject to regulation by receptor sites on their pre-synaptic membrane, which modify the release of transmitter across the synaptic cleft. </li></ul><ul><li>The effect of some neurotransmitters is to produce long-term modulation of metabolic function or gene expression rather than simply to change the membrane potential. </li></ul><ul><li>This effect probably underlies more complex processes in cognition, as long-term memory. </li></ul>
  7. 9. Neurotransmission / neurotransmitters. (1) An action potential arriving at the nerve terminal depolarises the membrane & opens voltage-gated calcium channels. (2) Entry of calcium causes the fusion of synaptic vesicles containing neurotransmitters with the pre-synaptic membrane & release of the neurotransmitter across the synaptic cleft. (3) The neurotransmitter binds to receptors on the post-synaptic membrane to either (A) open ligand-gated ion channels which, by allowing ion entry, depolarise the membrane& initiate an action potential (4), or (B) bind to metabotrophic receptors, which activate an effector enzyme (e.g. adenylyl cyclase)& thus via the intracellular second messenger system modulate gene transcription, leading to changes in synthesis of ion channels or modulating enzymes. (5) Neurotransmitters are taken up at the pre-synaptic membrane &/or metabolised.
  9. 11. Pesticide toxicity     injections Botulinum toxicity     Cataplexy     Anticholinergics, e.g. oxybutinin Bladder control     Anticholinergics, e.g. hyoscine Motion sickness     Huntington's chorea     Anticholinergics, e.g. benztropine, orphenadrine, procyclidine Parkinson's disease     Peripheral acetylcholinesterase inhibitors, e.g. edrophonium, pyridostigmine Myasthenia gravis     Central acetylcholinesterase inhibitors, e.g. donepezil, rivastigmine Alzheimer's disease Excitatory Acetylcholine Pharmacology Clinical relevance Effect Neurotransmitter
  10. 12. Used therapeutically as i.m. botulinum toxin Metoclopramide Vomiting     Antipsychotics Schizophrenia     Alzheimer's disease     dopamine agonists Parkinson's disease Excitatory Dopamine Motor neuron disease     Memantine Alzheimer's disease     Memory     Epilepsy   Aspartate Cerebral ischaemia Excitatory Glutamate Dexamfetamine Sleep disorders     Tizanidine Spasticity     Multi-system atrophy     Amphetamines, sibutramine Appetite     (α-blockers) Bladder control     (β-blockers), (α-blockers) Cardiovascular control     Antidepressants Mood disorders     β-blockers Migraine Excitatory Noradrenaline/adrenaline
  11. 13. Uncertain Inhibitory Histamine Startle syndromes Inhibitory Benzodiazepines Spasticity     Benzodiazepines Anxiety     vigabatrin Epilepsy Inhibitory GABA Sleep     Ondansetron Vomiting     Pain     SSRI antidepressants Depression     Pizotifen, triptans Migraine Excitatory (5-HT, serotonin)
  12. 14.    Dynorphins Morphine    Enkephalins Morphine    Endorphins Morphine Opioid peptides (> 20) Pain Substance P Melanocyte-stimulating hormone (MSH) Adrenocorticotrophic hormone (ACTH) Memory Uncertain Excitatory/ inhibitory Neuropeptides Vasopressin
  14. 16. Cerebral hemispheres <ul><li>The cerebral cortex constitutes the highest level of nervous function, the anterior half dealing with executive ('doing') functions & the posterior half constructing a perception of the environment ('receiving/ perceiving'). </li></ul><ul><li>Each cerebral hemisphere has four functionally specialised lobes. </li></ul><ul><li>Many of the functions are lateralised. </li></ul><ul><li>To which side depends on which of the two hemispheres is 'dominant', i.e. where language function is represented. </li></ul><ul><li>In right-handed individuals this is almost always the left hemisphere while in left-handers either hemisphere may be dominant with about equal frequency </li></ul>
  15. 17. Cerebral hemispheres : frontal lobes <ul><li>Concerned with executive function, movement & behaviour,it has: </li></ul><ul><li>Primary. </li></ul><ul><li>Supplementary motor cortex </li></ul><ul><li>Specialised areas for eye movements, speech (Broca's area) & micturition control. </li></ul>
  16. 18. Cerebral hemispheres : Parietal lobes <ul><li>Concerned with the integration of sensory perception. </li></ul><ul><li>The primary sensory cortex lies in the post-central gyrus of the parietal lobe. </li></ul><ul><li>Much of the remainder is devoted to 'association' cortex, which integrates the input from the various sensory modalities. </li></ul><ul><li>The supramarginal/ angular gyri of the dominant parietal lobe form part of the language area. </li></ul><ul><li>Close to these are regions dealing with numerical function. </li></ul><ul><li>The non-dominant parietal lobe houses areas concerned with spatial awareness / orientation. </li></ul>
  17. 19. Cerebral hemispheres : Temporal lobes <ul><li>Are the primary auditory cortex & primary vestibular cortex. </li></ul><ul><li>On the medial side lie the olfactory cortex & parahippocampal cortex involved in memory function. </li></ul><ul><li>Also contain many structures associated with the limbic system, including hippocampus & amygdala, involved in the processing of memory / emotions. </li></ul><ul><li>The dominant temporal lobe also participates in language functions, particularly verbal comprehension (Wernicke's area). </li></ul><ul><li>Music processing occurs in both temporal lobes, rhythm being processed on the dominant side& melody/pitch more on the non-dominant side. </li></ul>
  18. 20. Cerebral hemispheres : Occipital lobes <ul><li>Are principally concerned with visual processing. </li></ul><ul><li>The contralateral visual hemifield is represented in the primary visual (striate) cortex&areas immediately surrounding this are involved in the processing of specific visual submodalities as colour, movement or depth& the analysis of more complex visual patterns as faces. </li></ul>
  19. 21. Cerebral hemispheres : Basal ganglia <ul><li>Collections of cells in the depths of the hemispheres deal with: </li></ul><ul><li>Motor control (the basal ganglia). </li></ul><ul><li>The appropriate attention to sensory perception (the thalamus). </li></ul><ul><li>Emotion & memory (the limbic system). </li></ul><ul><li>Control over internal bodily functions (the hypothalamus). </li></ul>
  20. 22. Cerebral hemispheres : ventricles <ul><li>The cerebral ventricles contain the choroid plexus; producing CSF, which cushions the brain within the cranium. </li></ul><ul><li>From the fourth ventricle the CSF leaves through foramina in the brain stem to circulate down around the spinal cord& over the surface of brain, where it is reabsorbed into the cerebral venous system. </li></ul>
  21. 23. The brainstem: <ul><li>Containing: </li></ul><ul><li>1.All the sensory & motor pathways entering / leaving the hemispheres. </li></ul><ul><li>2.The nuclei of the cranial nerves: providing motor control to head muscles (including face / eyes) & some in the neck, along with coordinating sensory input from the special sense organs & the face, nose, mouth, larynx & pharynx. They also control autonomic functions including pupillary, salivary & lacrimal functions. </li></ul><ul><li>3.Nuclei projecting to the cerebrum& cerebellum. </li></ul><ul><li>4. The reticular formation: predominantly involved in the control of conjugate eye movements, the maintenance of balance, cardiorespiratory control & the maintenance of arousal. </li></ul>
  22. 24. The SC: <ul><li>Contains: </li></ul><ul><li>1.The afferent / efferent fibres arranged in functionally discrete bundles. </li></ul><ul><li>2.Collections of cells in the grey matter responsible for lower-order motor reflexes & the primary processing of sensory information, including pain. </li></ul>
  23. 25. The PNS: <ul><li>The sensory cell bodies of peripheral nerves are situated in the dorsal root ganglia in the spinal exit foramina, whilst the distal ends of their neurons are invested with various specialised endings for the transduction of external stimuli into nervous impulses. </li></ul><ul><li>The motor cell bodies are in the anterior horns of the spinal cord. Motor neurons initiate muscle contraction by the release of acetylcholine across the NMJ which results in change in potential in the muscle end plate. </li></ul><ul><li>To increase the speed of impulse conduction, peripheral nerve axons are variably invested in myelin sheaths consisting of the wrapped membranes of Schwann cells& any peripheral nerve is made up of a combination of large, fast, myelinated axons (which carry information about joint position sense & commands to muscles)& smaller, slower, unmyelinated axons (which carry information about pain , temperature& autonomic function). </li></ul>
  24. 26. The Autonomic NS: <ul><li>The unconscious neural control of the body's physiology is effected through the autonomic system. </li></ul><ul><li>This innervates the cardiovascular/ respiratory systems, smooth muscle of GIT& glands throughout the body. </li></ul><ul><li>The autonomic system is controlled centrally by diffuse modulatory systems in the brain stem, limbic system & frontal lobes, which are concerned with arousal & background behavioural responses to threat. </li></ul><ul><li>The output of the autonomic system is divided functionally & pharmacologically into two divisions: the parasympathetic/ sympathetic systems. </li></ul>
  25. 27. The major anatomical components of the nervous system
  26. 28. The anatomy of the cerebral cortex.
  27. 29. CORTICAL LOBAR FUNCTIONS Focal sensory seizures Contralateral hemisensory loss Dysphasia Language Calculation Parietal: dominant Versive seizures Focal motor seizures (Jacksonian march) Continuous partial seizures (epilepsia partialis continua) Impaired smell Contralateral hemiparesis Frontal release signs Disinhibition Lack of initiation Antisocial behaviour Impaired memory Expressive dysphasia Incontinence Personality Emotional control Social behaviour Contralateral motor control Language Micturition Frontal Positive phenomena Associated physical signs Cognitive/behavioural Function Lobe Effects of damage
  28. 30. CORTICAL LOBAR FUNCTIONS lower quadrantanopia Dressing apraxia     Contralateral homonymous Constructional apraxia     Agraphaesthesia Spatial disorientation     Focal sensory seizures Contralateral hemisensory loss Astereognosis Neglect of contralateral side Spatial orientation Constructional skills Parietal: non-dominant
  29. 31. CORTICAL LOBAR FUNCTIONS Complex hallucinations (smell, sound, vision, memory) Contralateral homonymous upper quadrantanopia Receptive aphasia Dyslexia Impaired verbal memory Auditory perception Language Verbal memory Smell Balance Temporal: dominant
  30. 32. CORTICAL LOBAR FUNCTIONS Complex hallucinations (smell, sound, vision, memory) Contralateral homonymous upper quadrantanopia Impaired non-verbal memory Impaired musical skills (tonal perception) Auditory perception Melody/pitch perception Non-verbal memory Smell Balance Temporal: non-dominant
  31. 33. CORTICAL LOBAR FUNCTIONS Simple visual hallucinations (e.g. phosphenes, zigzag lines) Homonymous hemianopia (macular sparing) Visual inattention Visual loss Visual agnosia Visual processing Occipital
  32. 34. NS Exam: