1. The Nervous System and Reflex Arcs IGCSE Biology

2. STARTER: Which of these actions do you need to think about? Blinking

3. Parts of the nervous system nervous system The nervous system is made up of three main parts; The brain The spinal cord Nerve fibres stimuli It detects stimuli such as light, sounds, temperature, pressure, pain and co- ordinates the bodies response.

4. Base of brainSpinal cordVertebrae (bones)

5. The nervous system sorts out information from the senses and sends messages to those muscles/glands which make the appropriate response What are the 5 sense organs and what can they sense? Smell Sound Touch SightTaste

6. sound light temperature Chemicals in air Chemicals in mouth pressure

7. Identification of the density of nerve endings Identification of the density of nerve endings – AIM: To investigate the sensitivity of different areas of the skin. Method: 1.Working in pairs, one student looks in a different direction, while another student touches them on the back of the hand with either one or two pieces of blunt pencil about 1 cm apart. 2.The blindfolded student has to say whether it was one point or two points that touched them. 3.Place a cross on the hand for each point felt. Results: Map the density of sensory receptors by drawing it into your book. Conclusion: Are the receptors in groups? Or randomly placed? What can you say about the density of the receptors identified?

8. What is happening? Your body’s sense organs contain receptors. and send messages (nerve impulses) along nerves to the brain and spinal cord (CNS). Receptors (sensory neurons) detect changes in the environment called stimuli

9. EFFECTORS effectorresponse An effector is any part of the body that produces the response. Here are some examples of effectors: a muscle contracting to move the arm a muscle squeezing saliva from the salivary gland hormone a gland releasing a hormone into the blood

10. What would happen if…. You were walking along the street listening to your iPod Suddenly this appears on the path in front of you! You task as a group: -how would detect this? -what process would your nervous system go through? -how would you avoid it! Fill in the boxes below! ReceptorStimulusEffectorResponse

11. NERVE FIBRES (neurones) (impulses) Nerve fibres are bundles of nerve cells (neurones) that pass on electrical signals (impulses) to the brain. effectors From the brain, nerve fibres send impulses to effectors (muscles/glands).

12. NEURONES There are three types of neurones 1.Sensory neurone 1.Sensory neurone – carries impulses from the receptors to the spinal cord. 2.Relay Neurone 2.Relay Neurone – carries impulses to and from the spinal cord and the brain 3.Motor Neurone 3.Motor Neurone – carries impulses from the brain to the effector Relay neurone

13. 2 TYPES OF OF NERVE PATHWAY… SENSORY NEURONE Takes impulses from the sense organ to the relay neurone. RELAY NEURONE Takes impulses to the brain and from the brain. MOTOR NEURONE Takes impulses from the relay neurone to the effector. BRAIN Receives impulses from the spinal cord and sends out new impulses. SENSE ORGAN/ RECEPTOR Senses stimuli from our surroundings.EFFECTOR The muscle that receives the impulse from motor neurone. SPINAL CORD Where the relay neurones are found. VOLUNTARYINVOLUNTARY

14. Reflex Arc Automatic responses to stimuli are called reflex actions. A reflex response is rapid and its function is protection The spinal cord mediates reflex responses to some sensory impulses directly ie. without going to the brain. This makes it much faster. The messages pass through a reflex arc:

16. Tasks for the rest of the lesson: 1.Make sure all your notes on your sheet are filled in 2.Now try the multiple choice questions on your sheet! 3.Don´t forget to mark off the Learning Outcomes we have covered in class today!

17. Quiz on the reflex arc This quiz has 10 multiple choice questions Click on the answer box you think is correct BEWARE ! One mistake and you have to start again! Click here to start quiz

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19. 1. Typically a muscle is an....... receptor effector synapse sensory neurone motor neurone relay neurone

20. Correct answer !

21. 2. Carries impulse away from a receptor receptor effector synapse sensory neurone motor neurone relay neurone

22. Correct answer !

23. 3. Can detect chemicals in the air liver skin nose muscle motor neurone relay neurone

24. Correct answer !

25. 4. The neurone in the spinal cord receptor effector synapse sensory neurone motor neurone relay neurone

26. Correct answer !

27. 5. Produces the response receptor effector synapse sensory neurone motor neurone relay neurone

28. Correct answer !

29. 6. Responds to the stimulus receptor effector synapse sensory neurone motor neurone relay neurone

30. Correct answer !

31. 7. Eg a cell of the retina in the eye receptor effector synapse sensory neurone motor neurone relay neurone

32. Correct answer !

33. 8. Carries an impulse away from the spinal cord receptor effector synapse sensory neurone motor neurone relay neurone

34. Correct answer !

35. 9. The first neurone to carry an impulse in a reflex arc receptor effector synapse sensory neurone motor neurone relay neurone

36. Correct answer !

37. 10. Found at the end of a relay neurone receptor effector motor neurone sensory neurone brain relay neurone

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40. Carries the impulse away from the receptor This is linked to the receptor and carries an electrical signal ( the message) away from the receptor towards the spinal cord. sensory neurone

41. Typically a muscle The effector has to produce the required response – eg your arm muscle must lift your hand away from a hot surface. (The effector can also be a gland which releases a hormone) effector

42. Can detect chemicals in the air Your nose contains lots of different chemical receptors that help you smell AND taste! nose

43. The neurone in the spinal cord The relay neurone hands on the message from the sensory neurone to the motor neurone, just like a baton is passed on in a relay race. relay neurone

44. Produces the response This is a definition of effector – it can be a muscle or a gland which releases a hormone effector

45. Responds to the stimulus This is a definition of receptor. It is often a sense cell receptor

46. Eg a cell in the retina of the eye This is an example of a receptor. Others might be the pain- and temperature- sensitive cells in your skin receptor

47. Carries impulse away from the spinal cord If the impulse if going away from the spinal cord, it must be going to an effector eg a muscle. The muscle will get a message to move – hence the term “motor neurone” motor neurone

48. First neurone to carry an impulse in a reflex arc There are three neurones in a reflex arc : sensory neurone, then relay neurone and finally motor neurone sensory neurone

49. Found at the end of a relay neurone The relay neurone is found in the spinal cord. It passes its signal to a motor neurone which in turn, triggers a response in an effector. Motor neurone

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51. xx receptor effector synapse sensory neurone motor neurone relay neurone

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