Physiology

1. Physiology XiaoLan HU (胡晓兰), MD & PhD Associate Professor of Department of Physiology Email: huxiaolan@zju.edu.cn

2. Two Chapters • Functions of the Sensory Organs • Functions of the Nervous System

3. Functions of the Sensory Organs • Section 1: Physiology of the Receptor and Sensory Organs • Section 2: Somatic Sensation • Section 3: Visual Function of the Eye • Section 4: Function of the Auditory System • Section 5: Vestibular function

4. Section 1: Physiology of the Receptor and Sensory Organs What isReceptor? Some structure or device that is distributed inside body surface or internal tissue, specifically sense the change from internal and external environment.

5. Section 1: Physiology of the Receptor and Sensory Organs Pacinian corpuscle Meissner's corpuscle Muscle spindle

6. Section 1: Physiology of the Receptor and Sensory Organs

7. Section 1: Physiology of the Receptor and Sensory Organs Classification of Receptors 1.By Location Exteroceptor: Visceral receptor: Proprioceptor: receive 2. By Stimulus Type *Mechanoreceptor:. *Thermoreceptor: *Nociceptor : *Photoreceptor: *Chemoreceptor: 3. By Complexity *Simple receptor: *Complex receptor:

8. Section 1: Physiology of the Receptor and Sensory Organs Adequate Stimulus of the receptor Conception: each receptor has its own the most sensitive stimulus. when the stimulus act on some receptors, the minimal intensity stimulus that can cause the corresponding sensation, is called adequate stimulus of the receptor.

9. Section 1: Physiology of the Receptor and Sensory Organs • Sensory threshold Intensity threshold: Temporal threshold: Area threshold: Discrimination threshold:

10. Section 1: Physiology of the Receptor and Sensory Organs Transducer function of the receptor Conception: Receptor detect a stimulus and convert the stimulus energy (light, pressure) into electrical signals (action potentials) in afferent nerve, this kind of energy conversion is called transducer function of the receptor. • brain only deals with bioelectrical impulses so transducer must occur • Sense organs convert sensory energy into neural (bioelectrical) energy • transduction process is that one type energy is converted into another type energy

11. Section 1: Physiology of the Receptor and Sensory Organs Transducer function of the receptor • Receptor potential and generator potential Receptor potential: membrane potential in receptor cells. Generator potential: membrane potential in afferent nerve endings. • Features of receptor potential: like local potential  Not “all or nothing”  Electrotonic propagation  Temporal & spatial summation

12. Section 1: Physiology of the Receptor and Sensory Organs Coding function of the receptor Conception: Receptors not only convert the external stimulus into nerve action potential, but also convert the environmental changes into the sequence of action potential signals, this is the coding function of the receptor. In same sensory system, stimulus intensity or quantity are how to be coded?

13. Section 1: Physiology of the Receptor and Sensory Organs Code pattern of stimulus intensity in the frog muscle spindle Frequency of action potentials Tetrodotoxin Receptor potential Receptor potential Stimulus (stretch) Stimulus (Stretch) Dynamic stage Static stage time stimulus intensity can be encoded by the frequency of action potential in single nerve fiber

14. Section 1: Physiology of the Receptor and Sensory Organs Adaptation of the receptor Conception: When a fixed strength stimulus act on a receptor, the frequency of the action potentials in afferent nerve fiber will gradually reduce. This phenomenon is called adaptation of the receptor Classification: rapidly adapting receptor(touch) and slowly adapting receptor(stretch and pressure )

15. Section 1: Physiology of the Receptor and Sensory Organs General Characteristics of the Receptors • Adequate Stimulus of the receptor • Transducer function of the receptor • Coding function of the receptor • Adaptation of the receptor

16. Section 2: Somatic Sensation Conception: The body accept different stimulus through the skin receptors and its affiliation, and produce various kinds of sensation Classification: Superficial somatic sensation: touch or pressure, temperature and pain Deep somatic sensation: proprioception (position and movement )

17. Section 2: Somatic Sensation Proprioception • Conception: • Proprioceptor: in the muscle, tendon and joint Muscle spindle: Tendon organ:

18. Section 2: Somatic Sensation Touch and pressure Conception: a kind of sensation that caused by mechanical stimulus (touch and pressure) Receptor types:

19. Section 2: Somatic Sensation Touch and pressure • Adequate stimulus: mechanical stimulus • Mechanism.

20. Section 2: Somatic Sensation Temperature Conception: caused by cold and warm stimulus Receptor: cold receptor and warm receptor. Warm receptor is free nerve endings, the warm sensory signals are transmitted by C fibers Cold receptor is also free nerve endings, the cold sensory signals are transmitted by Aδ fibers Which factors will impact on our temperature senses? When we have a temperature senses?

21. Section 2: Somatic Sensation Pain Conception: caused by internal and external noxious stimulus, often accompanied by emotion activities and defense response. Biological significance: defense response • Receptor: nociceptor • The characteristics of nociceptor: *No adequate stimulus. *Slowly adapting receptor. Discovered by Charles Scott Sherrington in 1906

22. Section 2: Somatic Sensation Pain • Classification of nociceptor *Mechanical nociceptor: only response to strong mechanical stimulus. Especially sensitive to needle stimulus *Mechanical temperature nociceptor: moderate responses to mechanical stimulus, especially responses to the temperature between 40 and 51 ℃ stimulus. With the temperature increase , reaction gradually strengthen *Polymodal nociceptor: responses to various nociceptive stimulus(mechanical, warm, and chemical ), is widely distributed in the skin, skeletal muscle, joint and internal organs.

23. Section 2: Somatic Sensation Pain • The afferent fibers of pain sense Aδ fibers for fast pain & C fibers for slow pain

24. Section 2: Somatic Sensation Pain • Algogenic substance Conception: Classification: Exogenous algogenic substance: Endogenous algogenic substance:

25. Section 2: Somatic Sensation Somatic Sensation • Proprioception • Touch and pressure • Temperature • Pain

26. Section 3: Visual Function of the Eye

27. Section 3: Visual Function of the Eye Section 3: Visual Function of the Eye 1.Dioptric System of Eye and its regulation 2.Photosensory and Transduction System of Eye 3. Other Visual Phenomena

28. Section 3: Visual Function of the Eye Dioptric System of Eye and its regulation • Optic Characteristics of Dioptric System • Reduced Eye • Accommodation of Eye • Error of eye refractive power

29. Section 3: Visual Function of the Eye Dioptric System: • Optic characteristics of dioptric system Four refractive interface : anterior surface of cornea posterior surface of cornea anterior surface of crystalline lens posterior surface of crystalline lens

30. Section 3: Visual Function of the Eye According to the calculating results from the geometrical optical principle, when normal adult eyes do not accommodate under quiet condition, the posterior focus of dioptric system just is on the retina. In the normal eye, light from an object more than 6 meters away may be considered as parallel rays, automatic focusing on the posterior focus (on the retina) to produce a clear image • Optic characteristics of dioptric system

31. Section 3: Visual Function of the Eye Dioptric System of Eye and its regulation • Reduced Eye bn ab = Bn AB

32. Section 3: Visual Function of the Eye • Far point of vision: • Near point of vision: • Accommodation of Eye The process that near objects are brought to a focus on the retina is called accommodation of eye, including the accommodations of crystalline lens, accommodation of pupil, and convergence reflex.

33. Section 3: Visual Function of the Eye crystalline lens is a transparent, elastic ,biconvex lens • Accommodation of Eye 1. Accommodation of crystallinelens

34. Section 3: Visual Function of the Eye • Accommodation of Eye 1. Accommodation of crystallinelens *The accommodation is mainly through increasing lens curvature . *The accommodation power is limited. If a object is close enough to the eye, the increased refractive power of the lens can not overcome the light divergence, and the object image will be blurred. *at near point. the accommodation is at a maximum.

35. Section 3: Visual Function of the Eye • Accommodation of Eye 2. Accommodation of pupil Types:Pupillary accommodation reflex, Pupillary light reflex, Consensual pupillary light reflex

36. Section 3: Visual Function of the Eye Pupillary accommodation reflex Conception: when eyes see the near object, pupil size will be reduced though neural reflex. Function: reduce the amount of light entering the eyes and reduce the spherical/chromatic aberration of dioptric system, the image on the retina is more clear.

37. Section 3: Visual Function of the Eye • Accommodation of Eye 3. Convergence reflex Conception: When the eyes look at a object that move from far to near, optic axis will converge to the nasal side. Function: eyes see near object, through convergence reflex, the object can fall on symmetric point of two retina, avoiding diplopia.

38. Dioptric System of Eye and its regulation • Optic Characteristics of Dioptric System • Reduced Eye • Accommodation of Eye • Error of eye refractive power

39. Section 3: Visual Function of the Eye What is emmetropia? • Error of refractive power What is ametropia? when the dioptric power of eye is abnormal or the morphology of eye is abnormal, the parallel light rays can not be focused on the retina, this eyes are called ametropia, including myopia, hyperopia and astigmatism.

40. Section 3: Visual Function of the Eye Myopia Conception: because the axial length of eyes are too long or the refractive power of lens are too strong, when eyes see far object, the parallel light focus in front of retina to form blurred image. Types: axial myopia and refractive myopia

41. Section 3: Visual Function of the Eye Hyperopia Conception: because the axial length of eyes are too short or the refractive power of lens are too weak, when eyes see far object, the parallel light focus at back of retina to form blurred image. Types:axial hyperopia and refractive hyperopia

42. Section 3: Visual Function of the Eye Astigmatism Conception:because the curvature of the cornea or lens are abnormal , Light from different direction do not be focused in the same point, form the blurred image or deformed image. Astigmatism can be corrected by the cylindrical lens.

43. Section 3: Visual Function of the Eye Dioptric System of Eye and its regulation • Optic Characteristics of Dioptric System • Reduced Eye • Accommodation of Eye • Error of refractive power

44. Section 3: Visual Function of the Eye Section 3: Visual Function of the Eye Dioptric System of Eye and its regulation Photosensory and Transduction System of Eye Other Visual Phenomena

45. Section 3: Visual Function of the Eye Photosensory and Transduction System of Eye • Structure of Retina • Two Photoreceptor System of Retina • Mechanism of Photoreception of the Rod • The Cone System and Color Vision

46. Section 3: Visual Function of the Eye Thickness of retina is only 0.1-0.5mm • Structure and function of Retina

47. Section 3: Visual Function of the Eye Main functions of four layers Pigment epithelium: Pigment epithelium do not belong to the nerve tissue, this layer contain melanin granules and VitA that have protective and nutritional effects on photoreceptor cells. Features of the layer are easy to cause detachment. In clinical practice, we see the retinal detachment, happen in this layer. Photoreceptor cell layer:: rods and cones, sensitive to light, are connected with bipolar cell through chemical synaptic connection. Bipolar cell layer:carry signal from photoreceptor to ganglion cell. Ganglion cell layer :axon of ganglion cell form the optic nerve.

48. Section 3: Visual Function of the Eye The distribution of rod and cone cells

49. Section 3: Visual Function of the Eye The structure of rod cells

50. Section 3: Visual Function of the Eye The structure of cone cells synaptic terminal