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PRINCIPLES OF THE NERVOUS SYSTEM

PRINCIPLES OF THE NERVOUS SYSTEM. “It is the brain that makes man a man” (Livingstone, 1976). “To understand a man we have to understand the brain” (Schmitt, 1967). ENVIRONTMENTAL CHANGES Internal External. THE BODY Constantly reacting and adjusting

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PRINCIPLES OF THE NERVOUS SYSTEM

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  1. PRINCIPLES OF THE NERVOUS SYSTEM

  2. “It is the brain that makes man a man” (Livingstone, 1976) “To understand a man we have to understand the brain” (Schmitt, 1967)

  3. ENVIRONTMENTAL CHANGES Internal External THE BODY Constantly reacting and adjusting HOMEOSTASIS BRAIN (afferent) INTEGRATION analyzed combined compared coordinated NERVES STIMULI SPINAL CORD HOMEO- STASIS Sensed & conveyed the messages (inputs) MUSCLES (skeletal/smooth/cardiac) GLANDS (endocrine/exocrine) (efferent) NERVES

  4. HOMEOSTASIS (Lat. homois: same; stasis: standing still) A state of inner balance and stability in the body, which remains relatively constant despite external environmental changes CNS (brain & spin. cord) * Processes sensory input from visceral organ aff. div.* AFF. (SENSORY) DIVISON VISCERAL NS processes sensory input aff. eff. (aff. div.) EFF. (MOTOR) DIV. (AUTONOMIC NS) SOMATIC NS PNS (periph. NS) eff. div.** (eff. div.) stimulates voluntary muscles (Comple- ment each other) SYMPATHETIC NS PARASYMP. NS ** triggers response in involunt. musc. & glands Responds to stress and emergency situations) Conserves & restore body resources

  5. GENERAL FUNCTIONS OF THE NERVOUS SYSTEM COMPLICATED STRUCTURES & FUNCTIONS COMPLICATEDCOMPLICATED (ASTRONOMICAL) STRUCTURES & INTERCONNECTIONS & FUNCTIONS INTERACTIONS(1 neuron 10,000 neurons) FUNCTIONS: INTERNAL 1. MONITORS:CNS (SENSORY)  RECEPTORS EXTERNAL 2. COORDINATES: APPROPRIATE RESPONSES (Processes, Integrates) 3. INSTRUCTS: CNS (MOTORIC)  EFFECTORS TO RESPOND muscles (skeletal, smooth, cardiac), glands (info)

  6. Complicated structures and interrelationships Convergence and divergence (the flow of info.)

  7. THE UNIQUENESS OF THE NERVOUS SYSTEM NEURONAL INTERCONNECTION COMPLEXITY INPUT: FROM HUNDREDS – 200.000 SYNAPSES N E U R O N OUTPUT: TO THOUSANDS - 10.000 NEURONS IN THE BRAIN: 100 BILLION (1011) OF NEURONS 100 TRILLION SYNAPSES (ASTRONOMICAL: STARS IN MILKWAY GALAXY) COUNTING: 1 sec./NEURON IT NEEDS 300.000 yrs.) THE BRAIN RECEIVES MILLIONS BITS OF INFORMATION FROM THE SENSORY ORGANS AND INTEGRATES THEM INTO VARIOUS RESPONSES

  8. NEURONS (NERVE CELLS): STRUCTURAL AND FUNCTIONAL UNITS OF THE NERVOUS SYSTEM • NEURONS (NERVE CELLS): • ARE SPECIALIZED TO TRANSMIT IMPULSES: • - FROM SHORT TO RELATIVELY LONG DISTANCES • - FROM ONE PART OF THE BODY OR CENTRAL NERVOUS SYSTEM TO ANOTHER • HAVE TWO IMPORTANT PROPERTIES: • EXCITABILITY (the ability to respond to stimuli) • CONDUCTIVITY (the ability to conduct a signal)

  9. CLASSIFICATION OF FUNCTIONAL COMPONENTS OF NERVES • The functional components of the neurons and their fibers • of peripheral nervous system may be clasified as follows: • GENERAL SOMATIC AFFERENT (GSA) FIBERS: • carry sensory information from somatic tissues • (skin, voluntary/skeletal muscles, joints, connective tissues) • to the CNS • 2. GENERAL VISCERAL AFFERENT (GVA) FIBERS: • carry information from the visceral organs to the CNS (aff.) GENERAL /SOMATIC RECEPTORS CNS (aff.) CNS VISCERORECEPTORS

  10. 3. GENERAL SOMATIC EFFERENT (GSE) FIBERS: carry nerve impulses from CNS to the most of the voluntary/skeletal muscles of the body (- the muscles contract - the muscles derived from masses of cells called myotomes) 4. GENERAL VISCERAL EFFERENT (GVE) FIBERS: carry impulses from the CNS that modify the activities of the heart, smooth muscles (included vasa), and glands (the fibers of autonomic nervous system) (eff.) CNS EFFECTORS: SKELETAL MUSCLES (eff.) EFFECTORS: SMOOTH/VASA & CARDIAC MUSLES.,GLANDS CNS

  11. 5. SPECIAL VISCERAL EFFERENT (SVA) FIBERS: carry impulses from the brain to the voluntary muscles derived from embryonic branchiogenic (gill) arches (this “visceral” musculature is found in the jaw, muscles of facial expression, pharynx, and larynx 6. SPECIAL SOMATIC AFFERENT (SSA) FIBERS: carry neural information from the receptors of the olfactory (smell), optic (sight), auditory (hearing), vestibular (balance), and gustatory (taste) systems to the CNS (eff.) CNS EFFECTORS: “BRANCHIAL/VISCERAL” MUSC. RECEPTORS: SPECIAL SENSORY ORGANS (aff.) CNS

  12. (Info) SENSORY/AFFRENT SYSTEM(CNS  RECEPTOR) (INFO.) (events/stimuli) (CNS) RECEPTOR EXTERNAL (somatosensory) RECEPTORS CONTACT (pain, temp., touch, pressure) DISTANT (sound, light, odours) * COLLECTING * PROCESSING INTERNAL (viscerosensory) RECEPTORS Tension, blood pressure, pressure, chemical composition of the blood (hormones, glucose, CO2, ions/electrolytes)

  13. MOTOR/EFFERENT SYSTEM( CNS  EFFECTOR) (INFO.) SOMATOMOTORIC  SKELETAL MUSCLES VISCEROMOTORIC  VISCERA, VASA Smooth muscles Myocardium ExocrineEnzymes Glandular cells EndocrineHormones MOTOR/ AFFERENT SYSTEM EFFECTORS

  14. Three functional classes of neurons: 1. Afferent neuron, 2. Interneuron (in the CNS), and 3. Efferent neuron

  15. DIVISIONS OF THE NERVOUS SYSTEM BRAIN (encephalon) Within the cranial cavity (structural) CNS SPINAL CORD (medulla spinalis) Within the vertebral canal NERVOUS SYST. (neurons: 1011 neuroglia: 1012 ) CRANIAL NERVES:12 pairs (from the brain) PNS (functional) SPINAL NERVES: 31 pairs (from the spinal cord) VISCERAL (unconscious) SOMATIC (conscious) Somatic tissues (skeletal muscles,skin, bones) AFFERENT SYMPATHETIC EFFERENT (AUTONOMIC) smooth & cardiac muscles, glands PARASYMPATHETIC Smooth & cardiac muscles, glands

  16. SPINAL NERVES (31) Cervical (8: C1-C8) Thoracal (12: T1-T12) Lumbar (5: L1-L5) Sacral (5: S1-S5) Coccygeal (1: co.)

  17. Principal parts of the brain (medial aspect)

  18. PERIPHERAL NS: CRANIAL NERVES (N I – N XII)

  19. AUTONOMIC NS* SYMPATHETIC NS Center: thoracolumbar PARASYMPATHETIC NS Center: cranisacral *ANS: unconscious component of the NS (regulates the internal organs/viscera)

  20. THE HUMAN BRAIN • MIND • (learning, memory, thought/ • intellect, emotion) • CONSCIOUSNESS • COGNITION • PERCEPTION • PERSONALITY • BEHAVIOR (Produces)

  21. NEURON (NERVE CELL) Fig. 1-2 • STRUCTURAL AND FUNCTIONAL UNIT OF NS* SOMA (cell body) (collective: gray matter/sustantia grisea) • COMPONENT DENDRITES PROCESSES AXON (collective: white matter/ substantia alba) TERMINAL  SYNAPSE (contact with other neuron/ effector cells) *NEURON: Specialized to receive info. Transmits electrical impulses (action potentials) Influences other effector tissues (neuron, muscle (skeletal, smooth, cardiac, glands)

  22. CLASSIFICATION & GROUPS OF NEURONS • CELL BODIES • Nucleus (pl. nuclei) A cluster of functionally related nerve cell bodies • Column (columna) (in cerbral cortex and spinal cord) • Layers (lamina/stratum) (in the spinal cord) CNS • AXONS • Tract/fasciculus (pl. fasciculi) Funiculus System A bundle of axons of a specific populations of a functionally related fibers • Lemniscus (pl. lemnici)

  23. CELL BODIES • Ganglion (pl. ganglia) A collection of cell bodies (Dorsal root /spinal ganglion Cranial nerve ganglion) PNS • AXONS • Nerves • Ramus A bundle of axons • Radix/Root

  24. Dendrite Nucleus Axon hillock Cell body/soma Axon Collateral Axon terminal NEURON (EM SCANNING)

  25. Nissl’s bodies Peripheral (myelinated) nerve

  26. CELLULAR COMPONENTS OF A NEURON

  27. CELLULAR COMPONENTS OF A NEURON (cont.)

  28. SYNAPSES (interneuronal contacts) • Axosomatic 2. Axodendritic 3. Axoaxonic 4. Dendrodendritic Axon terminal

  29. PRESYNAPTIC INHIBITION CONVERGENCE & DIVERGENCE

  30. Types of neuron: 1. Unipolar 2. Bipolar 3.Pseudounipolar4. Multipolar

  31. HOW NEURONS COMMUNICATE TO EACH OTHER ? Neurotransmitter (NT) • SYNAPSE CONSISTS OF: • Presynaptic element (part of axon terminal) • Synaptic cleft/space • Postsynaptic region (receptor at the postsynaptic membrane of the innervated neuron or effector structure) Electrochemical communication: action pot. propagation (electrical) + chemical (NT) transmission

  32. NERVOUS SYST. NEURONS NEUROGLIA NEUROGLIA (GLIAL CELL) 1.Oligodendrocyte 2. Astrocyte 3. Microglia 4. Ependymal cell (4) (2) (3) (1) NEUROGLIA BBB Astrocyte

  33. THE FUNCTIONS OF NEUROGLIA • CONTROL ENVIRONMENT (MICROENVIRONMENT) WITHIN THE CNS • Shuttle nutritive molecules (blood neuron) • Remove waste products of neurons • Maintain electrochemicals surround of neurons • Guiding developing neurons (migration) • Phagocytosis • Structural support for neurons BLOOD-BRAIN BARRIER (BBB): a system of tight junctions in the endothelial cells of brain capillaries that form a semipermeable membrane, allowing only certain substances to enter the brain

  34. Neuroglia Brain capillaries (BBB) Most capillaries in the body Oligodendro cyte Astrocyte Ependyma Neuron Microglia Blood-Brain Barrier (BBB) is formed by: 1. Astrocyte end feet 2. Basal membran 2. Endothelial cells (of brain capillary)

  35. TYPES OF NEUROGLIA CENTRAL NEUROGLIA (in the CNS) PERIPHERAL (in the PNS) 3. MICROGLIA in gray & white matters 1. ASTROCYTE (protoplasmic) in gray matter Schwann cells myelin sheath Satellite cells 2. OLIGODENDROCYTE (fibrous) in white matter 4. EPENDYMA lining cerebral ventricles

  36. SPINAL CORD • INSIDE THE VERTEBRAL COLUMN (in the vertebral canal) • 31 SEGMENTS 31 PAIRS OF SPINAL NERVES CERVICAL (C) : 8 THORACAL (T) : 12 LUMBAR (L) : 5 SACRAL (S) : 5 COCCYGEAL (Co) : 1 • CONTAINS: - SENSORY FIBERS - MOTOR NEURONS - ASCENDING/DESCENDING FIBERS (PATHWAYS/TRACTS TO AND FROM THE BRAIN) • REFLEX CENTER

  37. CROSS-SECTION OF THE SPINAL CORD Gray matter (substantia grisea) White matter (substantia alba)

  38. Histology of neuroglia

  39. BRAIN • The largest organ of the body • Composed of soft tissue (jelly) Needs strict protection • In adult: 1,300 g • Mushroom-shaped Medial aspect of the brain

  40. BRAIN BRAIN STEM DIENCEPHALON CEREBRUM CEREBELLUM CEREBRAL CORTEX BASAL GANGLIA MEDULLA OBLONGATA PONS THALAMUS HYPOTHALAMUS MESENCEPHALON

  41. A B Surface anatomy of the brain (A. lateral & B. medial)

  42. PROTECTION & COVERINGS OF CNS (protection against injury) • PROTECTION • BONES: - CRANIAL BONES (CRANIUM) (for the brain) • - VERTEBRAL COLUMN (for the spinal cord) • 2. MENINGES: - CRANIAL MENINGES (surround the brain) • - SPINAL MENINGES (surround the spinal cord) • 3. CEREBROSPINAL FLUID (CSF) • - Circulates through the subarachnoid space • - Formed by filtration and secretion from CHOROID PLEXUSES (network of capillaries); located in the ventricles of the brain • BLOOD-BRAIN BARRIER (BBB): - permits certain substances to enter the CSF but prohibits the others Protects the brain and spinal cord from harmful substances • - formed by various components : astrocyte end feet, capillary basal membr. & capillary endothelial cells (nonfenestrata)

  43. MENINGES & CEREBROSPINAL FLUID (CSF)/LIQUOR CEREBROSPINALIS (LCS)

  44. CEREBAL VENTRICLES • Lateral ventricles (right/left, in the cerebral hemispheres) • Third ventricle (between right& left diencephalon) • Aqueductus cerebri (Sylvius) • Fourth ventricle (ventral to cerebellum, dorsal to pons and med. Obl.) CSF CIRCULATION Choroid plex. (in the V Lat. + V III) V III Cerebral aqueduct V IV ( For. Magendie , For. Lushka) Subarachnoid space (around the brain + spinal cord) Arachnoid granulations vv. emmissariae V. jugularis int. Cor

  45. BBB Fenestrated capillary Nonfenestr. cap. Circulus Willisi a. comm. ant. a. Cerebri ant. a. carotis interna a. communicans post. a. basilaris a. cerebri post. a. vertebralis

  46. CORTICAL LOBES

  47. FUNCTIONAL AREAS OF THE CERBRAL CORTEX

  48. HORIZONTAL SECTION OF THE CERBRUM Basal ganglia LATERAL VENTRICLES AND LATERAL VIEW OF THE THALAMIC NUCLEI

  49. Insula

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