2009 6 th IJSO BIOLOGY

1. 2009 6th IJSO BIOLOGY • Responding Part 1

2. Notes to Teachers: Learning Objectives: • The five senses - the meaning of the terms stimuli and respond (0.25 hr) • The eye - mechanism of vision: function of rods and cones, color vision (0.5 hr) • The ear - the structure of the ear, the mechanism of hearing: the role of the organ of Corti, investigation on senses (0.75 hr) • The sensory functions of skin (0.5 hr) • The structure and functions of different types of neurone (0.5 hr) • Nerve impulse - generation and transmission of nerve impulse, the role of sodium and potassium ions, production of resting and action potentials, all-or-nothing nature of the action potential, concept of threshold (1.5 hrs) • Central nervous system - the organization of the nervous system into the central and the peripheral nervous system, structure and functions of human brain, spinal cord, and medulla (2 hrs) • Autonomic nervous systems - the control of involuntary activities by the sympathetic and parasympathetic nervous systems with reference to their antagonistic actions (1 hr) • Reflex action and voluntary actions (0.25 hr) • How muscles move (0.25 hr)

3. Learning Outcomes After studying this topic students should be able to: • describe the various senses in our body • define the terms stimulus and respond • explain the roles of various parts of eyes in detecting light • state and compare the functions of rods and cones • explain the roles of various parts of ear in hearing • perform investigation on senses e.g. sensitivity of skin of different body parts, hearing range of different ages • explain the sensory functions of skin • state the structure and functions of the neurons • state the nature of nerve impulse • describe the mechanism of generation and conduction of nerve impulse. • describe the mechanism of synaptic transmission • aware the complex organization of the nervous system

4. Learning Outcomes (cont’d) After studying this topic students should be able to: • identify the various parts of the human brain and spinal cord • state the functions of various parts of the central nervous system • state the role of the autonomous nervous system • explain the functioning of a spinal reflex and the types of neurons involved • state the significance of reflexes • cite examples of reflex action, conditional reflex and voluntary action and outline their importance in everyday life • describe the role of joints and muscles in locomotion • use the sliding-filament hypothesis to explain muscle contraction • investigate how fast our muscles react

5. Responding • Contents • -Understanding of how our bodies’ senses help us respond to our environment • -Describe the various senses in our body • -Define the terms stimulus and respond and how they relate • -Describe how nerves carry messages • -Explain how muscles move arms and legs • -Investigate the senses • -Investigate how fast our muscles react

6. Case study: A boy is reading ….. @#$^*??

7. Some terms • Stimuli • Responses • Receptors • Sense organs • Effectors • Coordination

8. A. The process of coordination Stimuli  receptors nervous system effectors -> response endocrine system

9. Sense, stimulus, receptor and sense organ

10. Skin – touch receptor, thermoreceptor(heat, cold receptor), pain receptor, pressure receptor • EpidermisB. DermisC. Subcutis/HypodermisD. Blood and Lymph VesselsE. Stratum Germinativum • 1.Hair Shaft2.Stratum Corneum3.Pigment Layer4.Stratum Spinosum5.Stratum Basale6.Arrector Pili Muscle7.Sebaceous Gland8.Hair Follicle9.Papilla of Hair10.Nerve Fiber11.Sweat Gland12.Pacinian Corpuscle13.Artery14.Vein15.Sensory Nerve ending (for touch)16.Dermal Papillary17.Sweat Pore18.Acidic Fluids/> Wikipedia file

11. Eye pupil iris Wikipedia file

12. Eye Wikipedia file

13. Rods and cones in retina Wikipedia file

14. photochemical reaction Light Rhodopsin Scotopsin + retinene (colourless) (purple) Dark Nerve impulse Under light, retinene undergoes isomeric change, rhodopsin breaks down to scotopsin and retinene (both colourless)  Bleaching of visual pigments  nerve impulse

15. Differences between rods and cones

16. Wikipedia file Each cone synapses with only one bipolar neurone  low visual sensitivity / tightly packed  high visual acuity Many rod synapses with one bipolar neurone  high visual sensitivity / less tightly packed  low visual acuity

17. trichromatic theory of colour vision • Sensation of any given colour is determined by the relative frequency of impulses reaching the brain from each type of cone • stimulate both green and red cones  yellow -Colour blindness -Red-green colour blindness

18. Ishihara test charts Wikipedia file

19. Accommodation – near / distant objects Wikipedia file

20. Pupil reflex Wikipedia file

21. Short sight and its correction Wikipedia file

22. Long sight and its correction Wikipedia file

23. Ear Wikipedia file

24. Organ of corti – sensory hair cell Wikipedia file

25. Wikipedia file

26. Mechanism of hearing Wikipedia file

27. Mechanism of hearing • - pinna collects sound waves - eardrum is set into vibrations -ear ossicles amplify the vibration -vibrations of oval window set the fluid in inner ear into motion • -pressure waves in fluid set the basilar membrane into vibrations. • - hairs of sensory hair cells in the Organ of Corti to brush against the tectorial membrane • - hairs bend and this shearing force causes the excitation of sensory hair cells • - excites the auditory nerve (the auditory part of VIIIth cranial nerve) and initiates action potential. -The auditory nerve conducts the action potential to auditory cortex of cerebrum where the pitch, quality and loudness of the sound are detected.

28. taste buds - chemoreceptors Wikipedia file

29. Chemoreceptors in nose Wikipedia file

30. Distribution of taste buds sensitive to different tastes • 1 . Bitter 2. Sour 3. Salty 4. Sweet Wikipedia file

31. 6th IJSO BIOLOGYPART 1.2 • Nerves • Function of nervous system

32. Chasing by a dog Wikipedia file Stimulus Light Receptor Photoreceptors Coordinating system ?? Effector ?? Response Skeletal muscles contract Running

33. Human nervous system Wikipedia file

34. Mammalian nervous system Wikipedia file

35. Mammalian nervous system • Central nervous system • Peripheral nervous system • Autonomic nervous system

36. Neuron(e) 神經元 Wikipedia file

37. Neuron(e) 神經元 Wikipedia file

38. Structure of a neurone • 1.Cell body – controls cellular activities found in grey matter (灰質) • 2.Nerve fibre – in white matter(白質) • -dendrons 樹突 • -axon 軸突 • -myelin sheath surrounded by Schwann cell plasma membrane, for insulation and increase the rate of conduction of nerve impulse

39. Myelinated VS unmyelinated nerve fibre Wikipedia file

40. 3 types of neurones • Motor neurone

41. Sensory neurone – olfactory sensory neurone Wikipedia file

42. Nerves – sensory/motor/mixed Wikipedia file

43. Nerve Wikipedia file

44. Spinal cord Wikipedia file

45. Wikipedia file

46. Wikipedia file

47. Wikipedia file

48. Functions of spinal cord • 1.relays these sensory impulses to the brain • 2. relay the motor impulses from the brain to • the limb muscles (e.g. leg muscles) via the • spinal nerves to effect coordinated movement • and to keep body in equilibrium posture. •  3. a passage for nerve fibres to allow the • 2-way conductionof nerve impulses to and from the brain and the limb muscles (e.g. leg muscles).  • 4. The spinal cord is the site for control of somatic reflexes(e.g. withdrawal reflex) which are involuntary actions.

49. Brain Wikipedia file

50. Wikipedia file