1. Physiology of the sensory system

5. Sensory

6. Types of Sensory Receptors
Mechanoreceptors
detect deformation
Thermoreceptors
detect change in temperature
Nociceptors
detect damage (pain receptors)
Electromagnetic
detect light
Chemoreceptors
taste, smell

7. Classification of Somatic Sensations
mechanoreceptive - stimulated by mechanical displacement.
tactile
touch
pressure
vibration
tickle and itch
position or proprioceptive
static position
rate of change

8. Classification of Somatic Sensations
thermoreceptive.
detect heat and cold.
nociceptive.
detect pain and are activated by any factor that damages tissue.

9. Receptor Potential the membrane potential of the receptor.
excitation of the receptor results from a change in this potential.
when the receptor potential rises above the threshold, action potentials appear and the receptor is active.
the greater the intensity of the stimulus, the greater the receptor potential, and the greater the rate of action potential generation.

10. Relationship between receptor potential and action potentials
Figure 46-2

11. Adaptation of Receptors
when a continuous stimulus is applied, receptors respond rapidly at first, but response declines until all receptors stop firing.

12. Adaptation of Receptors
when a continuous stimulus is applied, receptors respond rapidly at first, but response declines until all receptors stop firing.
Figure 46-5

13. Slowly Adapting (Tonic) Receptors
continue to transmit impulses to the brain for long periods of time while the stimulus is present.
keep brain apprised of the status of the body with respect to its surroundings.
will adapt to extinction as long as the stimulus is present, however, this may take hours or days.

14. Rapidly Adapting (Phasic) Receptors
respond only when change is taking place.
rate and strength of the response is related to the rate and intensity of the stimulus.
important for predicting the future position or condition of the body.
very important for balance and movement.

15. Types of sensation types of sensations General sensation
Somatic
visceral
Special senses
Smell, taste, vision etc

16. Types of sensation types of sensations General sensation
Somatic
visceral
Special senses
Smell, taste, vision etc
exteroceptor
proprioceptor

17. Types of sensation types of sensations General sensation
Somatic
visceral
Special senses
Smell, taste, vision etc
exteroceptor
Proprioceptor : muscle length and tension, joint position and their motion

18. Sensations receptors

19. Sensations modalities
FAST
SLOW
Prorioception
Fine touch & pressure
Vibration
Temperature
Crud touch (itch & rub)
Pain

20. Sensations modalities
FAST
SLOW
Prorioception
Fine touch & pressure
Vibration
Temperature
Crud touch (itch & rub)
Pain
Posterior Column-Medial lemniscus
Pathway
(PCML)

21. PCML Pathway

22. PCML Pathway

23. Sensations modalities
Important (critical)
Non critical
Prorioception
Fine touch & pressure
Vibration
Temperature
Crud touch (itch & rub)
Pain
Antero-lateral system (ALS)
Other name: Spinothalamic pathway

24. ALS Pathway

25. Conduction speed
Number of synapses
Myelination
Nerve axon size

29. Relationship Between Receptive Fields and Cortical Representation
Text Fig. 17-3
Text Fig
Smaller the receptive fields, greater the density of receptors. This relationship allows for greater discrimination in sensory inputs.
Inverse relationship in the cortex. Smaller the receptive fields larger the cortical area Larger the receptive fields smaller the cortical area

30. Visceral sensory & referred pain

31. Visceral sensory & referred pain

32. Visceral sensory & referred pain

33. Visceral sensory & referred pain

34. Referred pain
right
Left
liver

35. Sensory in the face
(Trigeminal system)

36. (Trigeminal system)
Carry all the sensation modalities from the face to the brain

37. (Trigeminal system)
Carry all the sensation modalities from the face to the brain