Week 3 - Nervous System PDF

NERVOUS SYSTEM Zaitunnatakhin Zamli 2 Learning outcomes The student should be able to:  Describe the organization of nervous system.  Describe the properties, structure, classification and functions of nervous tissues.  State the structure and functions of nerv...

NERVOUS SYSTEM Zaitunnatakhin Zamli 2 Learning outcomes The student should be able to:  Describe the organization of nervous system.  Describe the properties, structure, classification and functions of nervous tissues.  State the structure and functions of nervous organs.  Differentiate between the cranial and spinal meninges.  Describe the formation, circulation and absorption of CSF.  Differentiate between the blood- and CSF-brain-barriers.  Describe the general characteristics of ANS and PNS.  Distinguish between sympathetic and parasympathetic divisions.  INTRODUCTION NERVOUS SYSTEM: neuroglia neuron Nervous tissues ~ …………………………… brain spinal cord nerve receptor Nervous organs ~ …………………………… FUNCTIONS: Sensory Integrative Motor send formation to effetor  ORGANIZATION OF NERVOUS SYSTEM ANATOMICALLY: 1. Central nervous system (CNS) Brain Spinal cord 2. Peripheral nervous system (PNS) Nerves Ganglia collection of cell body in PNS Sensory receptors 1 Iii  ORGANIZATION OF NERVOUS SYSTEM sheath FUNCTIONALLY:  The Peripheral Nervous System (PNS) is divided into: i. Sensory/Afferent division Sensory receptors bring information of internal / external environment to the CNS. Subdivisions: iii a on a. Somatic – skin, muscle, bone and joint in thecentral b. Visceral – thoracic and abdominopelvic organs nervous systems c. Special - eye, ear, nose and tongue i. Motor/Efferent division Carry motor commands from the CNS to effectors.  ORGANIZATION OF NERVOUS SYSTEM FUNCTIONALLY …cont…:  The Motor/Efferent division is divided into: i. Somatic nervous system (SNS) Motor neuron  to skeletal muscle Subdivisions: a. Voluntary contraction b. Involuntary contraction ii. Autonomic nervous system (ANS) Motor neuron  to smooth and cardiac muscle & glands Subdivisions: a. Sympathetic nervous system b. Parasympathetic nervous system  iii c.is i errector organ internal carryinformation forourskeletal thenote throughout muscle carrytothe specificorgan  motor intergative motor sensory sensory sensory NERVOUS TISSUES  CELLS OF THE NERVOUS SYSTEMS - NEURONS PROPERTIES Excitability; Conductivity; Secretion CLASSIFICATION Anatomically a. Cytoplasmic processes / dendrites - Unipolar / pseudounipolar - Bipolar - Multipolar - Anaxonic b. Position and length of axon - Type I Golgi (e.g. Purkenji and pyramidal cells) - Type II Golgi (e.g. Granule cells) Functionally a. Sensory neuron (afferent) b. Motor neuron (efferent) c. Interneuron unipolar O O 12  CELLS OF THE NERVOUS SYSTEMS - NEURONS STRUCTURE OF A NEURON i. Cell body / perikaryon / soma - Nucleus – single and centrally located, with a large nucleolus - Cytoplasm – rich in Nissl bodies (RER), mitochondria, Golgi complex, lysosomes, inclusion and cytoskeleton. o Inclusion – pigments e.g. melanin, lipofuscin, lipid droplets, glycogen granules. o Cytoskeleton – microtubules and neurofibrils - Function – protein synthesis i. Dendrites - short and branched processes - contain most of the cytoplasmic components - Function - receiving signals  CELLS OF THE NERVOUS SYSTEMS - NEURONS iii. Axon - cylindrical and long projection - usually one per neuron - origin : axon hillock - may branched distally – axon collaterals - √ axolemma - √ axoplasm – contains mitochondria, microtubules and neurofibrils - √ terminal arborization - fine branches at the distal end of an axon. Each branch consists of synaptic knobs. - Function – sending impulse  CELLS OF THE NERVOUS SYSTEMS - NEUROGLIA NEUROGLIA / GLIAL / SUPPORTING CELLS Function – to protect the neuron and support their function Types i. Oligodendrocytes ii. Astrocytes iii. Microglia iv. Ependymal cells v. Schwann cells vi. Satellite cells  CENTRAL NERVOUS SYSTEM  CENTRAL NERVOUS SYSTEMS - BRAIN GENERAL FEATURES: BRAIN CAVITIES ~ 2.5% of body mass Lateral ventricles continuous with spinal cord Interventricular foramen via foramen magnum 3rd ventricle covers by meninges Cerebral aqueduct PARTS: 4th ventricle Cerebrum CROSSECTION: Cerebellum Gray matter – cortex Diencephalon White matter – subcortex Brainstem CRANIAL MENINGES: Dura mater Arachnoid mater Pia mater  BRAIN- CEREBRUM GENERAL FEATURES: largest part of the brain cerebral hemispheres - connected by corpus callosum covered by meninges PARTS: frontal lobe parietal lobe occipital lobe temporal lobe insula  BRAIN- CEREBELLUM General features: inferior to the cerebrum posterior to medulla and pons attaches to brain stem via cerebellar peduncles PARTS: R and L cerebellar hemispheres, connected by vermis Anterior, posterior and flocculonodular lobes CROSSECTION: Gray mater – folia White mater – arbor vitae  BRAIN - DIENCEPHALON PARTS: Thalamus – dorsal, egg- shaped Hypothalamus – anterior, forms the inferior wall and floor of 3rd ventricle Epithalamus – mainly occupied by pineal gland.  BRAIN - BRAIN STEM PARTS: ◦ Midbrain Transverses by cerebral aqueduct Anterior surface – cerebral peduncle Posterior surface – 2 superior colliculi (visual reflex) and 2 inferior colliculi (auditory reflex) ◦ Pons Anterior to cerebellum Posteriorly, upper border of 4th ventricle ◦ Medulla oblongata Cone-shaped √ median fissure, pyramids and olive  Thalamus Diencephalon Cerebral peduncle Optic tract Superior colliculus Mesencephalon / Midbrain Inferior colliculus Pons Optic chiasm Infundibulum Choroid plexus Thalamus Medulla Thalamus oblongata Third ventricle Cerebral peduncle Pineal gland Optic tract Superior colliculi Spinal Inferior cord N IV colliculi 1 Cerebral peduncle Pons Lateral view 2 3 Median fissure Choroid plexus in roof Olive of fourth ventricle Pyramids Medulla oblongata 1 Superior cerebellar peduncle 2 Middle cerebellar peduncle Spinal cord Anterior view 3 Inferior cerebellar peduncle Posterior view  CENTRAL NERVOUS SYSTEMS – SPINAL CORD FUNCTIONS: Conduction Integration and Reflexes GENERAL FEATURES: arises from the brainstem ends at L1 give rise to 31 pairs of spinal nerves CROSSECTION: √ median sulci and central canal Gray matter H-shaped, gray commissure Dorsal, lateral* and ventral horns White matter Surrounding white columns * Only in thoracic and lumbar regions.  CENTRAL NERVOUS SYSTEMS – SPINAL CORD SPINAL MENINGES: 1. Dura mater outermost layer √ epidural space 2. Arachnoid middle layer c.t. layer and lines with epithelium √ subarachnoid space – contain CSF 3. Pia mater innermost layer delicate and translucent membrane √ coccygeal and denticulate ligament  CENTRAL NERVOUS SYSTEMS – SPINAL CORD SPINAL TRACTS Def. …………………………………………. Types: i. Ascending tracts Sensory Consist of first- , second- and third-order neurons ii. Decending tracts Motor Consist of upper and lower motor neurons if decussation  contralateral tract if not decussation  ipsilateral tract Upper motor neurons Lower mo tor neurons  Dura meter Pin meter fat ligament Dorsal root ganglion  PERIPHERAL NERVOUS SYSTEM  PERIPHERAL NERVOUS SYSTEMS – NERVES GENERAL FEATURES Arrange in bundles Covers by c.t. – endoneurium, perineurium and epineurium NERVE FIBRES (AXONS) ◦ Myelinated or unmyelinated ◦ Classification of nerve fibres: Afferent and efferent fibres, OR Somatic and visceral fibres, OR General and specific fibres TYPES OF NERVES Spinal nerves Cranial nerves 45  NERVES – CRANIAL NERVES GENERAL FEATURES Cranialnervemnemonic 12 pairs (I - XII) Old …Olfactory (I) arise primarily from the base of Opie …Optic (II) brain Occasionally…Oculomotor (III) Tries…Trochlear(IV) CLASSIFICATION: Trigonometry…Trigeminal(V) - Sensory and…Abducens(VI) Feels…Facial(VII) - Motor Very …Vestibularcochlear(VIII) Gloomy, …Glossopharyngeal(IX) Vague…Vagus (X) - Mixed nerve and…Accessory(XI) Hypoactive …Hypoglossal(XII)  NERVES – SPINAL NERVES EE.ttII GENERAL FEATURES: 31 pairs – C (8), T (12), L (5), S (5) and C (1) √ nerve roots: - anterior/ventral - efferent/motor fibers of spinalcord - posterior/dorsal - afferent/sensory fibers √ rootlets Inferiorly - the nerve roots vertical  cauda equina Laterally - the nerve roots unite  spinal nerve Spinal nerve divides  anterior ramus and posterior ramus Certain area: the anterior rami branch and anatomose repeatedly  nerve plexus (i.e cervical, brachial, lumbar, sacral and coccygeal plexus)  White matter Gray matter Ventral root Spinal nerve Dorsal root Dorsal root ganglion Pia mater Arachnoid mater Dura mater Posterior view 50 PERIPHERAL NERVOUS SYSTEM – GANGLIA & SENSORY RECEPTOR GANGLION Capsulated B A Satellite cells around each cell body Types: - Dorsal root ganglia - Paravertebral ganglia - Prevertebral ganglia - Terminal ganglia SENSORY RECEPTORS will be discussed in general and special senses  AUTONOMIC NERVOUS SYSTEM  AUTONOMIC NERVOUS SYSTEM – ANS GENERAL FEATURES Def.: - a visceral / involuntary / motor nervous system that control glands, cardiac and smooth muscles. Functions: - To regulate heart rate, blood pressure, body temperature, respiratory airflow, pupillary diameter, digestion, energy metabolism, defecation and urination. Subdivisions: - Sympathetic nervous system - Parasympathetic nervous system * Both subdivisions differ anatomically and physiologically. However, they may:  innervate the same target organs  have similar or contrasting effects  AUTONOMIC NERVOUS SYSTEM – SYMPATHETIC NERVOUS SYSTEM SYMPATHETIC NERVOUS SYSTEM Prepare for emergency - “fight or flight” Functions: - increase heart rate, blood pressure and pulmonary airways, and constricts blood vessels, inhibits peristalsis and closes the sphincters, etc. Components: thoracic lumbar - Preganglionic neurons (thoracolumbar - T1 – L2) - Postganglionic neurons - Sympathetic chain of ganglia or paravertebral ganglia Neural pathways: - Efferent o Myelinated preganglionic fibres  white rami communicantes  sympathetic chain ganglia o At the ganglia, the fibre has 3 possibilities:  Synapse with postganglionic neuron  Travel up or down the ganglia before synapsing with the postganglionic neuron  Pass through the ganglia without synapsing. However, it synapses with postganglionic neuron in the ganglia outside the chain. Prevertebral Ganglion AUTONOMIC NERVOUS SYSTEM – PARASYMPATHETIC NERVOUS SYSTEM PARASYMPATHETIC NERVOUS SYSTEM Restore normal function - “resting and digesting” Functions: slows heart rate, increases peristalsis, and open sphincters, etc. Components: Preganglionic neurons (craniosacral – cranial nerves III, VII, IX and X, spinal nerves S2 – S4) Postganglionic neurons Terminal ganglia Neural pathways: Efferent Myelinated preganglionic fibers synapse with ganglia in OR near the viscera they innervate brain 57