The document discusses sensory perception and the role of receptors. It describes the basic process of stimulus reception, transduction, and transmission via receptors and sensory neurons. It classifies receptors by structure, location, modality, and adaptation properties. Receptors convert stimuli into receptor potentials, which may generate action potentials. Rapidly adapting receptors signal changes in stimuli while slowly adapting receptors signal sustained stimuli.

4. Sequence of Events in a Receptor Stimulus Basic Function Amplification Integration, perception Receptor Protein Activated Enzyme Cascade (in some cases) Receptor Ion Channels opened (or closed) Receptor Current Receptor Potential Modulated Impulse Frequency in Second Order Neuron Reception Transduction Transmission Modulated Impulse Frequency in Receptor Cell Axon Modulated Transmitter Release from Receptor Cell

5. Sensory Receptors

6. Sensory Receptor Types

7. Which receptor?

10. Sensory Receptor Types

16. Receptor potentials : Changes in the transmembrane potential of a receptor caused by the stimulus. Generator Potential : A receptor potential that is strong enough (reaches threshold) to generate an action potential. Remember that APs are all-or-none . The stronger the sitmulus (above threshold) the more APs are fired over a given time period; this is translated by the CNS as a strong sensation. Receptor/Generator Potential

34. Each type of receptor is highly sensitive to one type of stimulus for which it is designed and yet is almost nonresponsive to normal intensities of other type of stimuli. The stimulus to which a given receptor has the lowest threshold is termed the adequate stimulus of the sensory receptor. . Adequate Stimulus of Sensory Receptors

37. SENSORY REPRESENTATIONS

39. STIMULUS INENSITY

40. STIMULUS DURATION

41. STMULUS LOCATION

48. Sensory Adaptation is one form of Integration Phasic receptors quickly adapt. The frequency of action potentials diminishes or stops if the stimulus is unchanging. Tonic receptors adapt slowly or not at all. Most exteroreceptors (receptors that monitor the external environment) are phasic receptors .

51. Encoding of Sensory Receptor The quality of the stimulus is encoded in the frequency of the action potentials transmitted down the afferent fibre and the number of sensory receptors activated.

52. Stretch Receptors: Weak stretch causes low impulse frequency on neuron leaving receptor. Strong stretch causes high impulse frequency on neuron leaving receptor. Time Membrane potential Frequency Code

57. 10-25

58. THE END