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PRINCIPLES UNDERLYING THE BRAIN FUNCTIONS

PRINCIPLES UNDERLYING THE BRAIN FUNCTIONS. HUMAN NERVOUS SYSTEM controls all Human behavior. You are ‘ YOU ’ because of your NERVOUS SYSTEM , not because of your kidney or Heart or………………. NEURAL NETWORK. GENETICS. ENVIRONMENT. BRAIN.

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PRINCIPLES UNDERLYING THE BRAIN FUNCTIONS

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  1. PRINCIPLES UNDERLYING THE BRAIN FUNCTIONS

  2. HUMAN NERVOUS SYSTEM controls all Human behavior You are ‘YOU’ because of your NERVOUS SYSTEM ,not because of yourkidneyor Heartor………………

  3. NEURAL NETWORK GENETICS ENVIRONMENT BRAIN All BEHAVIOR is determined by the Human Nervous System HNS MALFUNCTION DISTURBANCE OF BEHAVIOR

  4. HUMAN NERVOUS SYSTEM EXTERNAL ENVIRRONMENT MOTOR SYSTEM SENSORY SYSTEM HUMAN BEHAVIOR MOTOR OUTPUT SENSORY RECEPTORS NEURAL NETWORK MUSCLES 10 11 NEURONS PRECISELY CONNECTED WITH EACH OTHER REFLEX ACTION OR DELAYED ACTION SENSORY CODING INFORMATION PROCESSING INFORMATION CREATION INFORMATION STORAGE

  5. Functional Unit of the Brain

  6. RESTING MEMBRANE POTENTIAL,ELECTROTONIC POTENTIALS, ACTION POTENTIAL 1. RestingMembranePotentialis a potential difference that exists across the membrane of a all cells. 2. Electrotonic Potentialis a voltage signal that is produced by passive changes in resting membrane potential of a cell (neuron or muscle). 3. Action Potentialis a voltage signal (an impulse) that is produced by a sudden and a transient reversal of resting membrane potential of an excitable active cell (neuron or muscle).

  7. HOW DOES CTION POTENTIAL LOOKLIKE?

  8. CHANGES IN MEMBRANE POTENTIAL Depolarization or Hypopolarization OUT - 50mV MEMBRANE - - - IN Resting Membrane Potential OUT - 70mV MEMBRANE - - - - - IN OUT - 80mV Hyperpolarization MEMBRANE - - - - - - - - IN The magnitude of potential depends on the degree of separation of the opposite charges

  9. PASSIVE CHANGES IN MEMBRANE POTENTIAL Electrotonic Potentials (IPSP) (EPSP) OR Hypopolarization

  10. ACETYLCHOLINE NICOTINIC RECEPTOR (CHANNEL)

  11. THE MAJOR NEUROTRANSMITTERS (Secretory granules)

  12. EXCITATORY POSTSYNAPTIC POTENTIAL (EPSP) At some excitatory synapses, closing of K+ or Cl- channels or both may cause ecxitation of the postsynaptic cell

  13. INHIBITORY POSTSYNAPTIC POTENTIAL (IPSP) At some inhibitory synapses, K+ channels open and hyperpolarize the postsynaptic cell

  14. TIME CONSTANT 63% τ In cells with longer time constant the signals decay slowly and therefore EPSPs have more time and better chance of integration – a process called “Temporalsummation”. In cells with shorter time constant the signals rapidly decay and therefore EPSPs have poor chance of integration.

  15. LENGTH CONSTANT In cells with longer length constant the signals spread to longer distances with minimal decay, and therefore EPSPs have better chance of integration – a process called “Spatial summation”. In cells with shorter length constant the signals spread to smaller distances, because of rapid decay and therefore EPSPs have poor chance of integration.

  16. ROLE OF EXCITATORY AND INHIBITORY POSTSYNAPTIC POTENTIAL INTEGRATION OF SIGNALS

  17. VIDIO OF INTEGRATION OF SYNAPTIC POTENTIALS

  18. Relationship between stimulus intensity and the receptor potential Graded Potential

  19. SPATIAL AND TEMPORAL SUMMATION

  20. VIDIOOF ACTION POTENTIAL CONDUCTION

  21. VIDIO OF SALTATORY CONDUCTION OF ACTION POTENTIAL

  22. SALTATORY CONDUCTION Local circuits cross the membrane only at the nodes of Ranvier. • Current density is greater. • Depolarisation is more rapid & threshold is reached more quickly • CV is raised • The AP appears to jump from node to node rather than propagate smoothly along the axon. • This process is Salatatory Conduction (Lat. saltere = to jump). • Local circuits can travel along the cytoplasm for several internodal lengths and still be strong enough to depolarise a node of Ranvier to threshold. Thus if one or more nodes are blocked, propagation is still possible over the inactive region. The axon has a large Safety Factor.

  23. ROLE CONVERGENCE AND DIVERGENCE IN INFORMATION PROCESSING

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