Receptor Classification, Electrical and Ionic Events.pdf

The presemntation deals with classification of sensors/recptors, their basic qualia and the neurophysiological events inclusivew of graded potentials and action potential that profile respective receptors.

1. Amitabh Dube, M.D.
Receptor Classification,
Electrical and Ionic Events
Sensorial Mechanisms

2. Receptor/Transducer
Classification

3. Types of Receptors
•Exteroceptors
•Interoceptors
•Proprioceptors

4. Exteroceptors
•Detection of Stimuli Near Outer Surface of Body
•Receptors on Skin Respond to
•May Also Include
•Cold and Hot (Warmth)
•Touch
•Pressure and Vibration
•Special Receptors For Hearing and Vision

5. Exteroceptors
•Mechanoreceptors
•Mechanosensitive Ion Channles
•Thermoreceptors
•Nociceptors
•Teloceptors
•Receptors of Electromagnetic Radiation
•Chemoceptors
•Taste
•Smell

6. Types of Receptors
•Mechano Receptors
•Chemo Receptors
•Electromagnetic Receptors
•Nociceptors
•Thermo Receptors

7. Mechano Receptors
•Pacinian Corpuscles: Vibration
•Meisseners Corpuscles: Touch
•Hair Follicles Receptors: Touch
•Merkels Disc: Pressure
•Rufini End Organs/Corpuscle: Pressure
•Tactile Disk: Pressure
•Free Nerve Endings

8. Mechano Receptors
•Muscle Spindles
•Golgi Tendon Organs
•Cochlear Receptors
•Vestibular Receptors
•Baro-Receptors

10. Thermo Receptors
•Krause End Bulb: Cold
•Free Nerve Endings: Cold
•Ruffini Endings: Warmth
•Free Nerve Endings: Warmth

11. Proprioceptors
•Muscle Spindle
•Golgi Tendon Organ
•Jont Receptor
•Vestibular Hair Cell

12. Proprioceptors
•Location
•Skeletal Muscles
•Tendons
•Ligaments and Joint Capsules

13. Proprioceptors
•Sensitive to
•Muscle Stretch
•Muscle Tone
•Position
•Angle of Joints
•Provides Sense of Body Position

14. Interoceptors
•Receptors Detect Stimuli From Deep Inside Body and Respond to
•pH
•Oxygen Level in Arterial Blood
•Carbon Dioxide Concentration
•Osmolality of Body Fluids
•Distention and Spasm: GIT
•Flow: Urethra

15. Interoceptors
•Visceral
•Baroreceptors
•Chemoreceptors
•Osmoreceptors
•Pain

16. Interoceptors
•Proprioceptors
•Muscle Spindle
•Golgi Tendon Organs
•Vestibular
•Joint Receptors

17. Electromagnetic Receptors
•Vision
•Rods
•Cones

18. Chemoreceptors
•Taste
•Smell
•Olfaction
•Aortic and Carotid Body Chemoreceptors
•Hypothalamic

19. Nociceptors
•Free Nerve Endings: Pain

20. Receptors
•Superficial
•Skin, Mucus Membrane & Subcutaneous Tissue
•Deep Receptors
•Proprioceptors
•Muscles, Tendons, Ligaments, Joint Capsule

21. Receptors
•Visceral
•Nociceptors
•Stretch Receptors
•Chemoreceptors
•Special
•Vision
•Olfaction
•Taste and Hearing
•Vestibular

22. Receptors
•Exteroceptors
•Telereceptors
•Olfaction, Audition, Vision
•Cutaneous Receptors
•Touch, Pain, Temperature, Tickle, Itch, Pressure

23. Stimulus Transduction
•Differential Sensitivity of Receptors
•Each Receptor Highly Receptive to One Type of Stimulus
•Appraises Nervous System of One Kind of Modality of
Sensation: Adequate Stimulus
•Primary Receptors
•Bare Nerve Endings For Pain
•Secondary Receptors
•Taste Receptor Involving Non-Neural Tissue

24. Adequate Stimulus: Physical Energy To Which A Receptor Is
Tuned
Receptor Adequate Stimulus
Eye Light
Ear Sound
Touch Deformation
Muscle Spindle Change in Ms Length
Golgi Tendon Organs Changes in Ms Tension

25. Transduction of Sensory Signal to Nerve Impulse
•Regardless of Type of Stimulus
•Effect on All Receptors is Same
•Change in Electrical Potential of Receptor
•Receptor Potential

26. Transduction of Sensory Signal to Nerve Impulse
•Stimuli Producing Change in Electrical Potential in
Receptor Types
•Heat and Cold
•Electromagnetic Radiation and Mechanical Deformation
•Oxygen COntent of Blood
•Depolarisation
•Except in Retina: Rods and Cones

27. Action Potential Initiation
•Receptor/Generator
Potential
•Depolarising
•Hyperpolarising
•Threshold
•Action Potential

28. Membrane Potential As Signals
•Cells Use Changes in Membrane Potential To
Exchange Information
•Voltage Changes
•Change in Membrane Permeability to Ions
•Change in Ion Concentration on Either Side of
Membrane

29. Membrane Potential As Signals
•Cells Use Changes in Membrane Potential To Exchange
Information
•Changes Made By Ion Channels
•Passive Channels: Leaky K Channels
•Active Channels
•Chemically Gated
•Voltage Gated

30. Receptor Potential
•Adequate Stimulus
•Graded Response
•Hypo and Hyperpolarisation
•Generate At at First Node of Ranvier
•Summation: Temporal and Spatial
•Adaptation

31. Adaptation
•Fast Adapting Receptors
•Phasic Receptors
•Slow Adapting Receptors
•Tonic Receptors
•Non-Adapting Receptors

32. Adaptation
•ViscoElastic Properties
•Accommodation
•Closure of Na+ Channels
•Change in Light Sensitive Chemicals
Concentration in Photoreceptors

33. Receptors
•Meissners Corpuscles
–Present on Non Hairy Part of Skin
–Fast Adapting Receptors
–Detect Movement of Objects over Skin
–Vibration Sense
–Abundant on Finger Tips, Lips & Other Places

34. Receptors
•Merkels Disc
•Expanded Tip Tactile Receptors
•Hairy & Non Hairy Skin
•Initially Transmit Strong Signal than Partially Adapting
•Weak Signals
•Slow Adapting Receptors
•Detect Continues Touch
•Help Tactile Localization
•Grouped together as Iggo Dome Receptors

35. Receptors
•Ruffini End Organ
–Present Deeper in Skin, Deep Internal Tissue & Joint Capsules
–Encapsulated, Slow Adapting
–Signal Continues Deformation of Skin & Deep Tissue
–Stimulated by Heavy Prolonged Touch & Pressure
–Signal Joint Rotation & Position Sense

36. Receptors
•Hair End Organ
•Rapidly Adapting
•Detect Slight Movement of Hair
•Tickle & Itch
•Served by Free Nerve Endings
•Found in Superficial Layers of Skin
•Fast Adapting Mechanoreceptors
•Transmitted by non Myelinated C Fibers

37. Receptors
•Position Sense
•Static
•Kinesthesia (Movement of Body Parts)
•Sensed by Mechanoreceptors of Joint Capsules,
Muscles, Tendons, Ligaments, Skin
•Neck Proprioceptors & Vestibular Apparatus

38. Receptor: Cellular and Molecular
Physiology

39. Receptors
•Receptors
•Ligand Gated
•Voltage Gated
•Receptors
•Metabotropic
•Ionotropic

42. Types of Membrane Potentials
○Graded Potentials
●Graded = Different Levels
of Strength
●Dependent on Strength of
Stimulus
○Action Potentials
●in Response to Graded
Potentials of Significant
Strength
●Signal over Long Distances
●All or None

44. Graded Potential
●Vary in Amplitude According to
Strength of Stimulus
●Short Distance Communication

45. Graded Potentials
○Graded Potentials Either
●Hyperpolarizing
•↑ Membrane Polarity
•Make Inside ↑ Negative
●Depolarizing
•↓ Membrane Polarity
•Make Inside ↓ Negative (↑
Positive)

48. Graded Potentials
●Receptor Potential/Postsynaptic Potentials/End
Plate Potentials
●Short Lived & Transient
●Local Changes in Membrane Polarisation
Status
●Voltage Change Varies With Stimulus Intensity

49. Graded Potential Propagation
○Electrotonic Propagation
○Ions Move Down Membrane
○A Decrement of Signal

52. Nerve Action Potential
●Amplitude Fixed
●All-or-None Event
●Electrical Impulses that Travel via
Axons
●Travel both Short & Long Distances

53. Properties of Action Potentials
○Nerve Impulse (Action Potential) Generated in Response to
Threshold Graded Potential
○Depolarization
●Change in Membrane Polarization
●Stimuli Reach Threshold Limit & Opens Voltage-Gated Na
+
Channels
●Na
+ Ions Rush into Cell  Down Na
+ Concentration & Electrical
Gradients
●Cytoplasm Becomes ↑ Positive
●Changes Membrane Potential to +30 mV
○Local Anesthetics Prevent Opening of Voltage-Gated Na
+
Channels - Prevent Depolarization

54. The All-or-None Principle
○Stimuli/Neurotransmitters Arrive & Open Some of
Chemically-Gated Na
+ Channels
●Stimuli Reach Threshold Level  Depolarization
Occurs
•Voltage-Gated Na
+ Channels Open
•Action Potential is Generated → Constant Amplitude
●Stimuli Do Not Reach Threshold Level  Nothing
Happens

55. Repolarization
○Re-establishing Resting Membrane Polarization State
●Threshold Depolarization Opens Na
+ Channels
•Na
+ Ions Flow Inward, Making Interior ↑ Positive
●A Few Milliseconds Later, K
+ Channels also Open
•K
+ Channels Open More Slowly & Remain Open Longer
●K
+ Ions Flow Out Along Concentration & Charge Gradients
•Carries Positive (+) Charges Out, Making Cell Interior ↑ Negative (-)
●Ion Movements Drive Membrane Potential Back Toward RMP Value
●Na
+/K
+ ATPase Continue Pumping Ions, Adjusting Levels Back to
Resting Equilibrium Levels
●Hyperpolarization – Briefly Exterior of Membrane ↑ Negative Than
Resting Potential Voltage Level

56. Refractory Periods
○Absolute Refractory Period
●Time Period during which
Second AP Cannot be Initiated
●Due to Closure of Inactivation
Gate on V-gated Na
+ Channel
●V-gated Na
+ Channels must be
Reset before they can Respond
to Next Stimulus
Many Consider this to be Start
of Absolute Refractory Period

58. Refractory Periods
○Relative Refractory Period
●Time Period During which a
Second AP can be Initiated with
a Supra-Threshold Stimulus
●K
+ Channels are Open, Na
+
Channels are Reset
●Membrane Remains
Hyperpolarized

60. Comparing Electrical Signals
Graded Potentials
●Cell Body & Dendrites
●Ligand & Mechanical Gates
●Shorter Propagation
●Variable Amplitude
●Longer Lasting than AP
●Hyperpolarizing to
Depolarizing
●No Refractory Period
●Adaptation
●Summation: Temporal &
Spatial
Action Potentials
●Axon Hillock & Axon
●Voltage Gated Na
+ & K
+
●Longer Propagation
●All-or-None Amplitude
●Shorter Lasting than GP
●Depolarization to
Repolarization
●Has Refractory Period

61. Thank You For
Your Kind Attention