Neurophysiology 1 Functional Neuronanatomy 2024 PDF

Neurophysiology 1 An introduction to functional neuroanatomy Overview – 10 Topics 1. Introduction & functional neuroanatomy 2. Neuronal support and protection systems 3. Neurotransmitters and their receptors 4. Consciousness and sleep 5. Pain 6. LMNs & spinal reflexes 7. UMNs & control of movement...

Neurophysiology 1 An introduction to functional neuroanatomy Overview – 10 Topics 1. Introduction & functional neuroanatomy 2. Neuronal support and protection systems 3. Neurotransmitters and their receptors 4. Consciousness and sleep 5. Pain 6. LMNs & spinal reflexes 7. UMNs & control of movement 8. Cranial nerves and the neuroexaminaiton 9. Descending (Part 1) and ascending (Part 2) pathways 10. Special senses: I Vestibular II Hearing III Vision III Taste & Smell  Neurology is the study of FUNCTIONAL NEUROANATOMY Functional = PHYSIOLOGY of neurons, their chemical impulses and collective behaviour Neuroanatomy = the anatomy of the brain, spinal cord, peripheral and visceral nervous systems and sensory apparatus Purpose = the diagnosis & treatment of disease Neurology is complex and there are no easy tricks to find the correct diagnosis (clin path and imaging will only give you part of the story, if any clues at all........) so you need to UNDERSTAND these systems to know how they will manifest during states of disease / injury / degeneration. What does the nervous system do? Collects sensory information (internal or external environment) Integrates this information Consciously or unconsciously to formulate a response plan Produces a final motor output that can either - Change the environment (external or internal) - Keep it constant Collecting sensory info and final motor output – PNS Integration – CNS A multifunctional, complex, integrated system that decodes and controls: Movement and posture Thought – cognition (think, reason, remember), perception, attention, learning Emotions and behaviour ‘Special’ Senses - sight - hearing (balance) - smell - taste - touch - proprioception A multifunctional, integrated system Movement and posture Thought – cognition perception, attention, learning Emotions and behaviour ‘Special’ Senses - sight - hearing (balance) - smell - taste - touch - proprioception Regulation of body systems, homeostasis Neuroanatomy Nervous system divisions Central Nervous System - Brain - Spinal cord PNS - Spinal nerves - Cranial nerves A little bit of embryology… A little bit of embryology… Central nervous system Generally considered to have 7 major parts 1. Telencephalon cerebral hemispheres “the forebrain” 2. Diencephalon Epithalamus;thalamus;hypothalamus 3. Midbrain “the brainstem” 4. Pons 5. Medulla 6. cerebellum 7. Spinal cord 1. Telencephalon Cerebral cortex + some deeper structures Telencephalon – the cerebral cortex Cerebral cortex 4 main lobes Frontal Parietal Occipital Temporal + Subcortical structures Telencephalon – the cerebral cortex Subcortical structures Basal ganglia corpus striatum (largest component) Caudate nuclei Lenticular nuclei Putamen Globus pallidus Substantia nigra (midbrain) Subthalamic nuclei Ventral striatum (nucleus accumbens) Hippocampus (limbic system)  Cerebral Cortex - function 6 layered structured an ‘inside to outside’ manner, developing from the dorsal telencephalon, which is sensory in origin. This part becomes a major link between sensory and motor function: the processing in between! Specific regionalisation of motor and sensory input Higher coordination of motor output Learning Memory Emotion Integration and modulation of complex input from all brain regions Basal ganglia - function Primarily motor control - ‘the gatekeeper’ for initiation of motor movement - Choses what actions to allow and inhibit Also has a range of functions associated with reward and cognition Dorsal striatum Primarily involved in control over conscious motor movement and executive functions Ventral striatum Limbic functions Basal ganglia – communication Source Inputs https://nba.uth.tmc.edu/neuroscience/m/s3/chapter04.html Outputs And communication between these areas (2 main pathways – net opposite effects. Inhibitory and excitatory)  Diseases Clinical signs: hypertonia, rigidity (esp of head); Function of basal ganglia best seen with unable to eat properly (may diseases that affect them demonstrate purposeless chewing movements) Animals: Centaurea solstitialis (St Barnaby’s thistle / yellow star thistle) poisoning in horses Destruction of the substantia nigra and globus pallidus Humans Parkinsons disease Huntingtons chorea 2. Diencephalon epithalamus, thalamus, hypothalamus Epithalamus Connects limbic system to other parts of the brain Not super relevant to us  Thalamus Paired egg shaped structure near the centre of the brain Connected left and right via ‘interthalamic’ adhesion) Several subnuclei Somatosensory nuclei Lateral geniculate nucleus (vision) Medial geniculate nucleus (auditory and visual reflexes) Ventral posteriomedial nucleus Ventral posteriolateral nucleus all sensory tracts pass through here…. Thalamus – function Functionally, the thalamus divides into five major functional Our focuses components as: Reticular and intralaminar Relays sensory and motor signals nuclei dealing with arousal and Receive sensory or motor info from pain regulation rest of body Sensory nuclei regulating all Every sensory system has a thalamic sensory domains except nucleus that receives processes and olfaction sends information. EXCEPT olfactory Effector nuclei governing Spinothalamic tract – goes through motor language function ventral posterolateral nucleus Associative nuclei connoting Present selected information to cognitive functions Limbic nuclei encompassing cerebral cortex. mood and motivation Regulates consciousness and alertness Hypothalamus Below the thalamus Multiple nuclei Afferent pathways Brainstem Thalamus Basal ganglia Cerebral cortex Olfactory  Hypothalamus – function Hypothalamus - homeostasis - neuroendocrine link - pituitary function - behaviour (hunger, satiety, thirst) - (interaction with the limbic system) - ANS inputs (direct and indirect) - circadian rhythm (via pineal and suprachiasmic nucleus) 3. Midbrain 4. Pons 5. medulla  Midbrain Part of the brain stem (along with medulla and pons) Several nerves, pathways, reflex centres and nuclei Tegmentum Midbrain Reticular formation Primitive nuclei forming a network. Networks lie in core of brainstem and project to whole brain Functional ascending pathway ARAS* Descending pathways through reticulospinal pathways* Occulomotor n. nuclei + Trochelear n. nuclei Periaqueductal gray matter Ascending and descending pathways (spinothalamic tract; corticospinal tract; rubrospinal tract) Red nucleus Substantia nigra Ventral tegmental area Tectum Superior and inferior colliculi Pons Between the midbrain and medulla Has a ventral and dorsal section Ventral portion Pontine nuclei Cortiopontine and cortiospinal tracts Dorsal portion Tegmentum Reticular formation as in the midbrain  Medulla Connection between brain and spinal cord Multiple important functional centres Cardiovascular-respiratory regulating systems, Descending motor tracts Ascending sensory tracts Cranial nerve origins Motor neuron crossing. Again divided Tectum – inferior medullary velum Tegmentum – inferior olivary nucleus, cranial nerve nuclei Basis – cross over point for pyramidal tract  Brainstem functions Reflexes of meiosis and mydriasis Passes impulses from nervous system between spinal cord and brain Conduit for the extrapyramidal tracts Sensory and motor control pathways. Relay of information from cerebrum to cerebellum (pons) Extrapyramidal pathways important for movement regulation. Reticular formation – across all 3 structures Visceral control, movement control and consciousness and sleep wake cycles also pain modulation (ARAS) Cranial nerve efferent and afferents Life support functions of respiratory and cardiovascular systems Feeding, taste, tongue, movement ,swallowing Visual and auditory information (superior and inferior colliculi) Cerebellum  Cerebellum The ‘little brain’ Separated from cerebrum by tentorium cerebelli (dura matter) Two hemispheres jointed by vermis Subdivided into three lobes Anterior Posterior Flocculonodular Neuron rich 80% of the brains neurons organised here. Cerebellum - function Smooth accurate and coordinated movement Co-ordinates Gait Maintains Posture Controls muscle tone Controls voluntary muscle activity BUT not able to initiate muscle contraction Motor learning Balance control  Brain region Normal Function Dysfunction 1. Cortex Conscious thought Unconsciousness Depression Seizures Motor cortex Planning & initiation of movement Paralysis 2. Thalamus Integration of neural pathways Behavioural changes Satiety / eating disorders Damage to motor / sensory tracts Hypothalamus Homeostasis, integration Narcolepsy Endocrine / limbic dysfunction 3. Limbus Behaviour, emotions Psychosis Addictive / repetitive behaviours Stress / anxiety 6. Brain stem Cranial nerve nuclei Abnormal cranial nerve function Autonomic nuclei [Autonomic dysfunction] Reticular formation Depression Axon tracts Abnormal motor function 7. Cerebellum Co-ordination/corrects Hypermetria / dysmetria movements Ataxia Spinal cord  Spinal cord Still part of the CNS Within the spinal colum Spans from brainstem down to lower back Terminates in ‘cauda equina’ Spinal cord function Conduct information from the brain to periphery (and back) Peripheral nerves penetrate into spinal cord at intervertebral foramina Synapse with nerves of the CNS And other neurons – interneurons Neurons of the CNS form tracts within spinal cord (white matter) Specific sections contain specific tracts Grey matter Divided into four main columns Dorsal horn, intermediate column, lateral horn, ventral horn Spinal cord tracts Peripheral nervous system A little more of embryology… Peripheral nervous system Spinal nerves Segmental arrangement Cranial nerves Can classify by direction afferent versus efferent Can classify by fuction Motor Somatic (motor neve axons) Visceral (ANS ganglia and axons) Sensory Somatic Visceral proprioception  PNS - Spinal Nerves Paired spinal nerves each have a dorsal (sensory) and ventral (motor) root Segmental arrangement The muscle or muscle group innervated by one spinal nerve is called a myotome  Spinal Nerves http://academic.kellogg.cc.mi.us/herbrandsonc/bio201_McKinley/f16-4_neuron_pathways_a_c.jpg White matter = axons (white from myelin) Grey matter = cell bodies Note internuncial neurons (interneurons) – these complete the reflex arc circuit Segmental Sensory Neurons Sensory neurons located in dorsal root ganglia along spinal cord Area of skin innervated by one spinal nerve is called a dermatome Handbook of Veterinary Neurologic Diagnosis, Oliver & Lorenz, 1st Edition, 1983, WB Saunders Co, Fig 3.40, p 51 The Cranial nerves Hypoglossal Trigeminal Accessory Abducens Olfactory Trochlear Vestibulocochlear Optic Occulomotor Glossopharyngeal Facial Vagus  A Bidirectional information / action system: Efferent (away from the CNS) Afferent (towards the CNS) Integration / routing of information The circuitry neuroactivity The outcome = movement! The stimulus http://www.felsteadgundogs.com/a_nervous02.gif PNS - sensory (afferent) system somatic (changes in external environment) - general (GSA) = CNV & all spinal nerves - specialised (SSA) = CNII, CNVIII (cochlear division) visceral (changes in internal environment) - general (GVA) = CNVII CNIX head CNX Spinal nerves body - special (SVA) = CNVII, IX, X and CNI proprioception - general (GP) = spinal nerves & CNV - special (SP) = CNVIII (vestibular division) PNS - motor (efferent) system after de Lahunta et al somatic (voluntary movement – skeletal muscle) general (GSE) all nerves except CN I, II & VIII visceral (involuntary movement/regulation - ANS) general (GVE) CNIII – symp & parasymp innervation of eye CNVII, IX and X All spinal nerves Functional Systems are based on their peripheral components. Some important definitions: AFFERENT SYSTEMS (information travelling TO the CNS) Sensory (afferent) The sensory portion of the PNS is classified on the basis of the location of dendritic zones in the body (the origin of impulse). Somatic afferent Has its dendritic zone on or near the surface of the body and receives stimulation from the environment General Somatic Afferent (GSA) Neurons distributed primarily by the 5th cranial nerve to the surface of the head and spinal nerves to the surface of the body and limbs all of which are sensitive to touch, temperature and noxious stimuli Special Somatic Afferent (SSA) Comprises the dendritic zones of specialised sensory organs limited to one deep to the surface of the body but stimulated by change in the external environment (CNn II and VIII). These definitions can be found on pages 3-4 of de Lahunta’s Veterinary Neuroanatomy and Clinical Neurology, Saunders Elsevier. Functional Systems are based on their peripheral components. More important definitions: AFFERENT SYSTEMS (information travelling TO the CNS) Sensory (afferent) Visceral afferent The visceral system, or afferent, has its dendritic zones in the viscera body and are stimulated by changes in the internal environment. General Visceral Afferent (GVA) Neurons distributed primarily by the 7th, 9th and 10th cranial nerves to visceral structures in the head and by the 10th cranial nerve and the spinal nerves to visceral structures in the body as well as blood vessels throughout the neck, trunk and limbs: In general the stimuli are either stretch or [chemical] changes. Special Visceral Afferent (SVA) Comprises the dendritic zones of CNn VII, IX & X limited to specialised receptors for taste; and CNI olfactory receptors. Functional Systems are based on their peripheral components. More important definitions: AFFERENT SYSTEMS (information travelling TO the CNS) Sensory (afferent) Proprioception The special proprioceptive system’s dendritic zones respond to change in position information from the limbs, body and head and neck. General Proprioceptive System (GPS) Dendritic zones are widely distributed in tissues of the head, neck, trunk and limbs, including joints deep to the body surface. Found in all spinal nerves and CNV, its receptors sense changes in lengths and position at their origin (muscles, tendons and ligaments). Special Proprioceptive System (SPS) Limited to specialised receptors that respond to position and movement of the head; and located in portions of the labyrinth of the inner ear, and send their afferent system via the vestibular portion of CN VIII. Functional Systems are based on their peripheral components. Still more important definitions: EFFERENT SYSTEMS (information travelling AWAY FROM the CNS) Motor (efferent) The motor or efferent portion of the PNS is classified on the basis of where the motor neuron terminates. These are also called Lower Motor Neurons (LMNs) as these are the neurons that actually innervate muscle cells. General Somatic Efferent (GSE) (Skeletal Muscle Nn) Dendritic zones are in the spinal cord ventral grey matter and motor nuclei in the brain. Their axons are in spinal nerves and cranial nerves and they innervate skeletal muscle cells. They are found in all nerves except cranial nerves I, II and VIII (SSA). General Visceral Efferent (GVE) (Autonomic Nn) Dendritic zones widespread throughout CNS. Motor end plates are in visceral muscles, blood vessels and glandular tissues. A 2-neuron chain, its first synaptic connection is located in the spinal or cranial nerve ganglia. Axons are found in all nerves. So, information is travelling in a number of directions with a number of different outcomes depending on the system (GSA, proprioceptive, GSE etc)....... ALL at the same time....... CNS - brain UMN - spinal cord PNS - motor systems LMN - sensory system