1. Co-ordination Standard Grade Biology The Body In Action

2. Co-ordination All the organs and systems in a healthy human body are coordinated. They cooperate with one another and work efficiently to bring about the many functions that are essential to life. Give examples in life where coordination is important!! What coordinates the body?

3. What does your nervous system do for you?

4. The Nervous System

5. The nervous system controls our bodies and helps us respond to external stimuli. The nervous system works by sending electrical impulses along neurones (nerve cells).

6. The Nervous System There are two main parts: –Central nervous system – brain and spinal cord –A network of nerves

7. Reflex Arc A chain of events occurs in order for us to respond to a stimulus –Stimuli = changes in surroundings –Receptor = detect the changes –Co-ordination = decides what to do –Effector = action –Response = reaction to change

8. Example – reflex arc Example: sitting on a drawing pin Stimuli Receptor Co-ordination Effector Response Information from the receptors pass along neurones to the brain, the brain then co- ordinates a response.

9. Pupil Activity Using the information given, draw flow charts linking the following stimulus and responses, or in the following situations –Food and production of saliva –Fox hunting a rabbit By the rabbit By the fox –Kicking a conversion on the rugby field –Catching a ball –Crossing the road

10. Reflex Action Some responses to stimuli are automatic and rapid these are called reflex actions. In a reflex action three types of neurone are involved sensory, relay and motor neurones.

11. In a reflex action: 1. Impulses from a receptor pass along a sensory neurone to the central nervous system. 2. At a junction (synapse) between a sensory neurone and a relay neurone in the CNS, a chemical is released which causes an impulse to be sent along a relay neurone.

12. 3. A chemical is then released at the synapse between a relay neurone and a motor neurone in the CNS. This causes impulses to be sent along a motor neurone to the organ (effector), which brings about the response. 4. Effector is either a muscle or a gland. A muscle responds by contracting, a gland by releasing chemical substances.

13. Reflex Arc

15. More about Co-ordination Read all information given on the sheet. Answer questions 1 & 2 Using your knowledge MI 11 –Answer questions (a) and (b)

16. Synapse A synapse is the small gap between neurons, when an impulse reaches the end of an axon a chemical is produced. The chemical diffuses across the gap; it starts off an impulse in the next neuron. Only one end of a neuron can make this chemical, so synapses make sure the impulse can only travel in one direction.

17. Synapse

18. Synapses are easily affected by drugs: Can block them Can make them work too quickly Alcohol can affect synapses, which can slow down peoples ’ reactions.

19. Drugs and the nervous system There are 4 main categories of drugs which can affect our nervous system: –Sedatives slow down the brain making you feel sleepy. –Stimulants speed up the action of the brain making you more alert. –Hallucinogens cause hallucinations –Painkillers suppress the part of the brain that senses pain.

20. The Structure of the Eye

21. The Eye Sight is one of our most important senses. The eye lies in a socket in the skull, and is moved by the action of three pairs of eye muscles, which swivel the eye in their sockets.

22. Structure of the Eye The sclera is the tough, white protective layer which surrounds the eye. The cornea is the transparent region at the front of the sclera. The cornea allows light to enter the eye. The iris surrounds the pupil controlling its size and the amount of light which enters the eye.

23. Structure of the Eye The lens changes shape to focus light onto the retina, it is held in place by ciliary muscles and suspensory ligaments. The retina contains receptors cells which are sensitive to light. There are two types of receptor cells –Rods – work in dim light –Cones – detect colour and details

25. Seeing Things

26. Light enters the eye through the cornea It passes through the lens It is focused on the retina Receptor cells in the retina send impulses to the brain along sensory neurones along the optic nerve The brain interprets the impulse to make a picture

27. The Iris Reflex The Iris reflex prevents too much light entering the eye and damaging the retina Increased light reaches the retina –Light sensitive cells in retina send impulses along a neurone to the brain –Brain sends impulses along another neurone to the iris muscles –Size of pupil decreases

28. The Iris Reflex Stimulus Receptor Sensory neurone Brain Motor neurone Effector Response

29. Iris Reflex

30. Seeing things The eyes produce two overlapping images Carry out the exercise twice, once with both eyes open, once with one eye closed

31. The Eye

32. Optical illusions

33. Optical Illusions

35. What do you see? Hold the card so that your nose touches the star. What happens as you turn the card?

36. Are these letters straight?

37. Testing your blind spot

38. Focusing When light rays enter the eye they are refracted by the cornea and the lens. Ciliary muscles and suspensory ligaments control the shape of the lens.

39. Looking at a distant object Ciliary muscle relax Tightening the suspensory ligaments Lens is pulled into a thin shape Distant object is focused on the retina

40. Looking at a near object Ciliary muscles contract Slackens suspensory ligaments Elastic lens goes fatter Near object is focused on the retina

41. The Ear Hearing and Balance

42. Hearing Having two ears rather than one makes judging the direction of sound more accurate

43. ear drum – thin membrane which picks up the vibrations of sound waves bones of the middle ear –(hammer, anvil & stirrup) –amplify the vibrations and pass them on to the cochlea cochlea –long coiled tube in the inner ear filled with fluid –it picks up the vibrations and changes them to electrical signals

44. auditory nerve –connects the inner ear to the brain –it carries the electrical signals from the cochlea semi-circular canals –detect movements of the head –help control balance and tell us which way up we are

45. Balance The semi-circular canals are 3 tubes at right angles to each other - they pick up movements of the head by detecting movements of the fluid they contain

46. These movements are turned into electrical signals –since there are 3 canals at right angles the brain can use these signals to give 3-dimensional information to help control balance and tell us which way up we are.

47. The Brain

49. The brain The brain is at the top of the spinal cord and is protected by the skull. Cerebrum –Controls memory, personality, imagination and reasoning Cerebellum –Controls muscle coordination and balance Medulla –Controls heart rate and breathing