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NERVOUS SYSTEM class 1.pptx
- 2. NERVOUS SYSTEM • MAINTAINS HOMEOSTASIS • RESPONSIBLE FOR PERCEPTION, BEHAVIOUR,MEMORIES&MOVEMENTS • NEUROLOGY • WT.2 Kg • CONSISTS OF CNS,PNS • NEURONS&NEUROGLIA
- 4. NERVOUS SYSTEM • CNS –BRAIN & SPINAL CORD • PNS –NERVES OUTSIDE BRAIN & SPINAL CORD • SENSORY • MOTOR • VOLUNTARY • INVOLUNTARY –ANS • SYMPATHETIC & PARASYMPATHETIC
- 6. • NERVE—BUNDLE OF AXONS COVERED WITH CONNECTIVE TISSUE & BLOOD VESSELS • OUTSIDE BRAIN & SPINAL CORD • GANGLIA—SMALL MASSES OF NERVOUS TISSUE-MAINLY CELL BODIES OUTSIDE BRAIN & SPINAL CORD NERVOUS SYSTEM
- 7. – SENSORY FUNCTION • RECEPTORS SENSE INTERNAL CHANGES LIKE SLOOD SUGAR, Ph & EXTERNAL STIMULI LIKE TOUCH,PAIN etc VIA SENSORY NERVES – INTEGRATIVE FUNCTION • PROCESSING OF INFORMATION TO MAKE APPROPRIATE RESPONSE---PERCEPTION— INTERNEURONS – MOTOR FUNCTION • ONCE THE SENSORY INFORMATION IS INTEGRATED MOTOR RESPONSE IS ELICITED—MUSCLE CONTRACTION /GLAND SECRETION VIA MOTOR NEURONS NERVOUS SYSTEM--FUNCTIONS
- 8. NEURONS • BASIC FUNCTIONAL UNIT OF NS • PARTS OF A NEURON – BODY – DENDRITES – AXON • SYNAPSE-JUNCTION BETWEEN TWO NEURONS / AXONS / NEURON & EFFECTOR CELL – CONTAINS NEUROTRANSMITTERS
- 10. NEURON--STRUCTURE • CELLBODY • CONTAINS NUCLEUS SURROUNDED BY CYTOPLASM WITH ORGANELLE LIKE MITOCHONDRIA, GOLGI APPARATUS, RIBOSOMES --SITE OF PROTEIN SYNTHESIS
- 11. • DENDRITES • DENDRITES RECEIVE MESSAGES / INPUT • SHORT TAPERING & HIGHLY BRANCHED • CYTOPLASM CONTAINS NISSL BODIES MITOCHONDRIA NEURON--STRUCTURE
- 12. • AXON • LONG THIN CYLINDRICAL PROJECTION WHICH CARRY IMPULSE TO ANOTHER NEURON, MUSCLE FIBRE OR GLAND • AXOPLASM • AXOLEMMA • AXON TERMINALS NEURON--STRUCTURE
- 14. NEURON • STRUCTURAL DIVERSITY • MULTIPOLAR • BIPOLAR • UNIPOLAR
- 16. FUNCTIONS OF NEURONS • ELECTRICAL EXCITABILITY &CONDUCTIVITY – ABILITY TO RESPOND TO STIMULUS & GENERATE ACTION POTENTIAL • STIMULUS IS A CHANGE IN THE ENVIRONMENT THAT IS ABLE TO GENERATE ACTION POTENTIAL • NERVE IMPULSE IS AN ELECTRICAL SIGNAL THAT TRAVELS ALONG THE NEURON DUE TO MOVEMENT OF IONS SPEED 1-1.5m/S
- 17. • NERVE IMPULSE -WHEN AN ACTION POTENTIAL OCCURS IN A NERVE • AP IS TRANSMITTED BY THE MOVEMENT OF IONS ACROSS THE CELLMEMBRANE • PLASMA MEMBRANE OF EXCITABLE CELLS EXHIBIT MEMBRANE POTENTIAL—ELECTRICAL VOLTAGE DIFFERENCE ACROSS THE MEMBRANE CALLED RESTING MEMBRANE POTENTIAL FUNCTIONS OF NEURONS
- 19. • WHEN A NERVE IS STIMULATED THE PERMEABILITY OF Na+, K+ INCREASE Na+ FLOODS IN TO THE NEURON AND DEPOLARISATION STARTS • THE INITIALLY –ve CHARGE WILL BECOME NEUTRAL AND THEN +ve • THIS CREATES AN IMPULSE THAT IS TRANSMITTED AWAY TO THE END OF THE AXON FAST • THEN REPOLARISATION OCCURS –CHANNELS OPEN AND K+ RUSHES OUT NERVE IMPULSE
- 20. NERVE IMPULSE • THE PLASMA MEMBRANE CONTAINS DIFFERENT KINDS OF ION CHANNELS THAT OPEN & CLOSE IN RESPONSE TO STIMULI • AT REST THE CHARGE ON THE OUTSIDE IS POSITIVE –Na+ AND INSIDE IS NEGATIVE • THERE IS A TENDANCY FOR THE IONS TO MOVE ACROSS THE MEMBRANE THAT CHANGES THE MEMBRANE POTENTIAL • TOGETHER THE MEMBRANE IS ELECTRICALY NEUTRAL
- 22. • AP IS ACCORDING TO ALL OR NONE PHENOMENON • IF THRESHOLD POTENTIAL IS CROSSED THEN DEPOLARISATION OCCURS AND ACTION POTENTIAL IS GENERATD & TRANSMITTED • REFRACTORY PERIOD—THE PERIOD OF TIME AFTER AN AP BEGINS DURING WHICH TIME AN EXCITABLE CELL CANNOY GENERATE ANOTHER AP NERVE IMPULSE
- 28. • AFTER REPOLARISATION Na+ IS PUSHED OUT OF THE CELL BY PUMP • IN MYELINATED NEURONS THE MOVEMENT OF IONS OCCUR ONLY AT NODES OF RANVIER CALLED SALTATORY CONDUCTION • CONDUCTION IS CONTINUOUS IN MUSCLES & NONMYELINATED NERVE FIBRES • SPEED OF CONDUCTION DEPENDS ON THE DIAMETER OF THE AXON • LARGER ONES CONDUCT FASTER NERVE IMPULSE
- 29. NERVE FIBRES • TYPE A—MYELINATED LARGE FIBRES FASTEST • MOTOR NERVES TO SKELETAL MUSCLES • TYPE B---MYELINATED MEDIUM SIZED • SENSORY & VISION • TYPE C—NONMYELINATED SMALL • AUTONOMIC FIBRES & SENSORY FROM SKIN
- 30. SYNAPSE • JUNCTION BETWEEN NEURONS OR NEURONS & END ORGANS – AXO-AXONIC – AXO-SOMATIC – AXO-DENDRITIC • ONE WAY CHANNELS • PRESYNAPTIC NEURON-SENDS • POST SYNAPTIC NEURON -RECEIVES
- 31. SYNAPSE • ELECTRICAL – THEY HAVE SMALL TUBULAR CONNECTION BETWEEN THEM THROUGH WHICH AP TRAVELS – FASTER & SYNCHRONISED • CHEMICAL – GAP JUNCTION – THERE IS SYNAPTIC CLEFT SPACE FILLED WITH INTERSTITIAL FLUID – INVOLVES NEUROYRANSMITTERS – THERE IS SYNAPTIC DELAY
- 33. NEUROTRANSMITTERS • CHEMICAL SUBSTANCES OR HORMONES • THEY ARE REMOVED BY – DIFFUSION BACK TO YHE CELL – ENZYMATIC DEGRADATION – UPTAKE BY CELLS
- 34. NEUROTRANSMITTERS • SMALL MOLECULE NEUROTRANSMITTERS – ACETYL CHOLINE • SECRETED BY NEURONES BOTH IN PNS & CNS • CAN BE INHIBITORY OR EXCITATORY • ACETYL CHOLINE ESTERASE INACTIVATES IT – BIOGENIC AMINES • AA ARE DECARBOXYLATED TO PRODUCE Eg DOPAMINE, EPINEPHRINE,NOREPINEPHRINE • CALLED CATECHOLAMINES HAVE AMINO GROUP & CATECHOL RING – AMINOACIDS-GLUTAMIC ACID, ASPARTIC ACID EXCITATORY • GABA,GLYCINE INHIBITORY – NITRIC OXIDE—USED AS ANESTHETIC AGENT
- 35. • NEUROPEPTIDES – SECRETED BY VESICLES BOTH PNS & CNS – 3-40 AA LINKED TOGETHER BY PEPTIDE BONDS – EXCITATORY & INHIBITORY – ENCEPHALINS & ENDORPHINS – FORMED FROM CELL BODY NEUROTRANSMITTERS
- 36. REGENERATION OF NEURONS • NEURONS EXHIBIT PLASTICITY • THEY CAN CHANGE ACCORDING TO ENVIRONMENT • POWER FOR REGENERATION IS VERY LIMITED • WHEN NEURONS ARE INJURED GLIAL CELLS PROLIFERATE FORMING A BARRIER FOR REGENERATION
- 38. NEUROGLIA • HALF OF THE VOLUME OF CNS IS NEUROGLIA • HOLD THE NERVE CELLS TOGETHER LIKE GLUE • IN INJURY GLIA PROLIFERATE TO FILL THE GAP • 4 TYPES DEPENDING ON THE SIZE & CYTOPLASMIC PROCESSES
- 40. • ASTROCYTES – STAR SHAPED—MANY PROCESSES – LARGEST & MOST NUMEROUS – CONTAIN MICROFILAMENTS, SUPPORTS NEURONS – FOOT PROCESSES FORM PART OF THE BLOOD BRAIN BARRIER – IN THE EMBRYO THEY SECRETE REGULATORY SUBSTANCES FOR THE NEURAL GROWTH – THEY REGULATE THE CHEMICAL ENVIRONMENT,LIKE CONCENTRATION OF K+,NUTRIENTS – FORMATION OF NEURAL SYNAPSES WHICH AFFECT LEARNING & MEMORY NEUROGLIA --CNS
- 41. • OLIGODENDROCYTES – SMALL CELLS WITH FEWER PROCESSES – FORM & MAINTAIN THE MYELIN SHEATH – CONTROL THE SPEED OF TRANSMISSION – ONE CELL CAN MYELINATE MANY AXONS • MICROGLIA – SMALL CELLS WITH SLENDER PROCESSES – PHAGOCYTOSIS—THEY REMOVE CELLULAR DEBRIS DURING DEVELOPMENT NEUROGLIA
- 42. • EPENDYMAL CELLS – CUBOID/COLUMNAR CELLS ARRANGED IN SINGLE LAYER – THEY HAVE CILIA & MICROVILLI – THEY LINE THE VENTRICLE – THEY PRODUCE & MONITOR CIRCULATION OF CSF NEUROGLIA
- 43. ORGANIZATION • GREY MATTER – NEURONALCELL BODIES, DENDRITES,UNMYELINATED AXONS, AXON TERMINALS & NEUROGLIA • WHITE MATTER – MYELINATED AXONS – WHITE COLOUR IS DUE TO MYELIN • NUCLEUS –CLUSTER OF NEURONAL CELL BODIES IN CNS • GANGLION--CLUSTER OF NEURONAL CELL BODIES IN PNS
- 45. • SCHWANN CELLS – THEY ENCIRCLE THE AXON & MYELINATE 1 AXON – HELP IN AXON REGENERATION • SATELLITE CELLS – FLAT CELLS AROUND GANGLIA – THEY SUPPORT & REGULATE EXCHANGE OF MATERIALS BETWEEN NEURONS & INTERSTITIAL FLUID NEUROGLIA --PNS