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Sensory systems 1

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Sensory systems 1

  1. 1. PHYSIOLOGY DEPARTMENT Ass. Prof. VASTYANOV Rooslan
  2. 2. SENSORY SYSTEMS #1SENSORY SYSTEMS #1 GENERAL PROPERTIES OF SENSORY SYSTEMS
  3. 3. PLEASE, MOBILES SHOULD BE OFF
  4. 4. Reception, perception and transmission of information Reception, perception and transmission of information
  5. 5. ANALYZER - it`s specific sensory (receptory) system of neurons that consist of: • Peripheral part - receptors • Conductive part – pathways and afferent neurons • Central part – cerebral cortex
  6. 6. Classification of sensation organs: • Vision organs • Hearing organs • Eqvilibrium organs • Smell organs • Taste organs • Viscerosensation • Touch organs • Temperature sensation • Pain sensation • Posture sensation somato- sensory analyzer
  7. 7. GENERAL STRUCTURE OF ANALYZERS - NEURAL ENDINGS - RECEPTOR CELLS - PARTICULARIZED SENSATION ORGANS PERIFERAL PART CONDUCTIVE PART CENTRAL PART - CONDUCTIVE WAYS - CEREBRAL STRUCTURES
  8. 8. Main principles of the analyzers composition • Each analyser has a lot of neurons levels that are related by the pathways • Each level has a lot of neuronal fibers – pathways • Each level has a different amount of the cells – they work according principles of convergence and divergens • Each level has a different function: peripheral part – reception, middle part – conduction, central part – analyse.
  9. 9. MAIN PROPERTIES OF THE ANALYSERS: • Detection of the stimuli by receptors • Ability to form a receptor (generator) potential • Perception of the stimulies according to a definite increasing force of the irritation. • Transmission (spreading) of the stimulies. • Conversion information into a special system – code • Adaptation to stimulies • Cortical and subcortical information analyse
  10. 10. 2. Peripheral part of analyzers
  11. 11. ANALYZER PERIPHERAL PART • Receptors – specific neural cells or ending of neural fibers that are adaptated to perception of irritation.
  12. 12. Receptor classification #1 1. By localization: - external- - internal: - contact (taste, touch) - visceroreceptors - distance (visual, hearing) - vestibuloreceptors (equilibrium) - proprioreceptors (muscles) - tissue receptors - vessels receptors 2. By nature of irritation: 3. By adaptation: - baroreceptors (tension) - high adaptation speed - chemoreceptors - low adaptation speed - thermoreceptors - nonadaptive receptors - mechanoreceptors 4. By stimulies specifity: - photoreceptors - adequate - inadequate
  13. 13. Receptor classification #2 5. By specificity of irritation perception: - specific receptors - nonspecific receptors 6. By mechanism of excitation generating: - Primary perceptive receptors (generate GP) - Secondary perceptive receptors (generate RP) 7. By ability to percept of irritation types: - Monomodal receptors - Polymodal receptors
  14. 14. MAIN RECEPTOR PROPERTIES 1. EXCITABILITY – ability to excitation  generation (RP, GP, AP)  2.   SPECIFICITY – ability to percept only  specific irritation  3. Ability to TRANSFORMATE specific  irritation in electric impulse (coding) 4. Ability to ADAPTATION – increasing of  irritation threshold
  15. 15. MAIN RECEPTOR FUNCTIONS • Perception of the irritation • Excitation generating • Primary analysis of excitation • Coding information of irritation parameters
  16. 16. MECHANISM OF RECEPTOR EXCITATION • Irritation impulse + receptor →↑membrane permeability for Na→ depolarization (repolarization is in photoreceptors!) and - generator potential (GP) develops in primary receptors - receptor potential (RP) develops in secondary receptors→ RP+RP+RP=GP → GP+GP+GP=AP
  17. 17. Stimulus, sensor and action potential relationships
  18. 18. Graphical representation of the sensory nerve activity in case of stimuli applying of different intensities and durations
  19. 19. General properties of local potentials (LP) - it doesn’t spread along the nerve fibers - it works according to law of gradation - it has ability to summation - it hasn’t refractory period - short-time duration of LP (but RP has long-time duration)
  20. 20. PRIMARY ANALYSIS IS PROVIDED for - Different areas of receptive fields, - Specific perception of irritation by receptors - Different levels of receptor excitations - Different levels of receptors adaptation, - Different time of excitation development in receptors, - Mechanisms of feed-back connection between receptors and neural
  21. 21. Coding information • - it`s a conversion information into a specific system – code. Transmission of impulses is effected by a binary code. Presence of an impulse – is 1, its absence equals to 0. The information about the stimulies is transmitted in the form of individual groups or “volleys” of impulses. The amplitude and duration of the individual impulses passing identical along the same fiber, but the frequency and number of impulses in volley may be different.
  22. 22. 1. By change of number of AP: If the sound has frequency less then 1000 Hz, the cells form equal amount of AP. If the sound has frequency more then 1000 Hz, the cells start to code impulses. 2. By change of impulses speed transmission Types of information coding
  23. 23. The scheme of stimulus processing and information coding
  24. 24. RECEPTORS ADAPTATION it’s the increasing of irritation threshold under the specific impulse action, which acts a long period of time Adaptation mechanisms: - ↓amount of working receptors - ↓ RP amplitude - ↓ frequency of impulse conduction - change of neural centres condition
  25. 25. The scheme of adaptation of slow- and fast- adapting receptors on dependence with their stimulation
  26. 26. 3. Conductive part of analyzers
  27. 27. COMPOSITION OF ANALYSERS CONDUCTIVE PART 3 NEURONS: - dendrites of 1-st sensor neurons - axon of 1-st sensor neurons - axon of 2-d sensor neurons (Т-neurons) - axon of 3-d sensor neurons Somato-sensor analyzer: 1-st neuron – spinal ganglies 2-nd neuron – cornu posterior of spinal cord, Goll's and Burdach's nuclei
  28. 28. MAIN FUNCTIONS of ANALYZERS CONDUCTIVE PART - Excitation conduction - Secondary analysis of irritation - Encoding irritation information
  29. 29. LAWS OF IMPULSES CONDUCTION in NERVES - The law of anatomical and physiological continuity of a nerve - The law of two-way conduction - The law of isolated conduction along a nerve
  30. 30. 4. Central part of analyzers
  31. 31. ANALYSER CENTRAL PART Subcortical information analyse
  32. 32. Cortical information analysis Motor areas involved with the control of voluntary muscles Motor speech area (Broca`s area) Sensory areas involved with cutaneous and other senses Understanding speech, using word Parietal lobe General interpretative area
  33. 33. Motor and sensory gyrus Parietal lobe Sensory area Central sulcus
  34. 34. Motor and sensory areas trunk neck Upper arm Lower arm Hand, fingers, and thumb Upper face Sensory areasMotor areas
  35. 35. FUNCTIONS OF ANALYSERS CENTRAL PART - tertiary analisis of excitation - transformation of excitation into sensation - formation of perceptible image - memorization of perceptible image
  36. 36. PARAMETERS OF ANALYSIS • Intensity threshold (force) of irritation – it’s min force of irritation, caused sensation • Differential threshold of irritation – it’s min force increment of irritation, caused sensation • Spatial threshold of irritation – it’s min distance between two irritation stimulus, that permits these two stimulus to percept separately The less receptive field the less spatial threshold • Temporal threshold – it’s min time between two irritation stimulus, that permits these two stimulus to percept separately
  37. 37. Perception of the stimulies according a definite increasing proportion • 1834 y. – Weber formulated the law that states: S= a log R + b Receptors in organism percept difference force of the irritation if the index between stimulies increases according a definite proportion 100g – 3g 200g – 6g 600g – 18g
  38. 38. 4. Proprioceptive sensory system
  39. 39. MechanoreceptorsMechanoreceptors
  40. 40. Mechanical sensationMechanical sensation The pacinian corpuscle is a very rapidly adapting receptor with a large receptive field that is used to encode high-frequency (100–400 Hz) vibratory sensation. The receptor is located on the end of a group B myelinated fiber, which is inser- ted into an onion-like lamellar capsule The pacinian corpuscle is a very rapidly adapting receptor with a large receptive field that is used to encode high-frequency (100–400 Hz) vibratory sensation. The receptor is located on the end of a group B myelinated fiber, which is inser- ted into an onion-like lamellar capsule The spindle-shaped Ruffini's corpuscle is a slowly adapting receptor that encodes pressure. It has a large receptive field that is used to encode the magnitude of a stimulus. The receptor is located on the terminal of a group B axon that is covered by a liquid-filled collagen capsule. Collagen strands within the capsule make contact with the nerve fiber and the overlying skin. The spindle-shaped Ruffini's corpuscle is a slowly adapting receptor that encodes pressure. It has a large receptive field that is used to encode the magnitude of a stimulus. The receptor is located on the terminal of a group B axon that is covered by a liquid-filled collagen capsule. Collagen strands within the capsule make contact with the nerve fiber and the overlying skin. Meissner's corpuscle is a rapidly adapting receptor that participates in the touch sensation and low- frequency (10–100 Hz) vibration. The receptor is located at the end of a single group B afferent fiber that is inserted into a small capsule. Meissner's corpuscle is a rapidly adapting receptor that participates in the touch sensation and low- frequency (10–100 Hz) vibration. The receptor is located at the end of a single group B afferent fiber that is inserted into a small capsule. Merkel’s disk is a slowly adapting receptor with a small receptive field that is also used to encode the touch sensation. The epithelial sensory cells form synaptic connections with branches of a single group B afferent fiber. Merkel’s disk is a slowly adapting receptor with a small receptive field that is also used to encode the touch sensation. The epithelial sensory cells form synaptic connections with branches of a single group B afferent fiber.
  41. 41. Skin receptors localizationSkin receptors localization

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