1. Coordination & Response

2. Nervous or Endocrine System? Information is passed through hormonal signals. Information is passed through electrical signals. Information takes seconds to travel through the body. Information takes minutes, hours, or days to travel through the body.

3. The Nervous System

4. Includes: brain, spinal cord, nerves, receptors. Receptors = a cell that can sense something about its environment Stimulus = information sensed by receptors – Light, sound, touch, temperature, chemicals Information is converted into electrical (nerve) signals.

5. Receptor Cells and Sense Organs Stimulus (detected by Receptor Cells) Light Temperature Sound Touch Taste/Smell Sense Organ (including Receptor Cells) Eye(s) Skin Ear(s) Skin Mouth/Nose

6. Sense Receptor Cells

7. The Human Eye The light-sensitive receptors in the eye are in the retina. They are called rods and cones. Rods detect dim light. Cones detect bright light in many colors.

8. Rods & Cones

9. Light Detection The retina is in the back of the eye. Light falling onto the cells in the retina (rods & cones) in converted into electrical signals. These signals travel to the brain through the optic nerve.

11. Focusing the Eyes The cornea focuses light onto the retina. It is like a converging lens; it bends (or refracts) the light rays inwards.

12. Focusing the Eye

13. Accommodation Accommodation = how your eye adjusts to focus on objects at different distances The cornea does not change shape. The lens takes care of accommodation. The lens needs to be thin to focus on distant objects, and fat to focus on nearby objects.

14. The Lens

16. But how does the lens change its shape? A ring of muscles called the ciliary muscles surrounds the lens. The lens is connected to the ciliary muscles by the suspensatory ligament. The muscle contracts to make the lens fat, and relaxes to make the lens thin.

18. Focusing the Lens Distant Objects Ciliary muscle relaxes Suspensatory ligament tightens Lens is stretched thin Light is refracted less Nearby Objects CM contracts SL relaxes Lens gets fat Light is refracted more

20. Do you know… What contains receptor cells sensitive to light? What refracts light rays as they enter the eye (can’t change shape) What is responsible for fine adjustments to focusing? What holds the lens in position? What is the ring of muscles that changes the shape of the lens? What is the colored part of the eye? Retina Cornea Lens Susp. Ligs Cil. Musc. Iris

21. The Optic Nerve and Blind Spot There are no rods or cones in the place where the optic nerve joins the retina. This is the blind spot! Light from an object will never fall on both blind spots at one time. Let’s all find our blind spots and measure them!

22. The Human Eye

23. More Eye Games Find your Near Point of Vision! – The closest you can focus on an object Find your Dominant Eye! – The eye you use when you have to pick

24. What is the Nervous System made up of? Brain, spinal cord, nerves, and receptors. The brain and spinal cord make up the central nervous system (CNS). Everything else is part of the peripheral nervous system.

25. CNS

26. Central & Peripheral NS

27. Nerves and the CNS When receptors pick up information, they send it along nerves to the CNS. The CNS processes and coordinates all the information. Then the CNS sends new messages along other nerves to tell muscles and glands what to do. Effectors carry out messages from the CNS.

28. Neurons Nerve cells are called neurons. Sensory neurons carry messages from receptor cells to the CNS. Motor neurons carry messages from the CNS to the effectors (like muscles).

29. Nerve Cell (Neuron)

30. Motor & Sensory Neurons

31. Neurons Nerve cells, like other cells, have a cell membrane, cytoplasm, and nucleus. Axon = long thread of cytoplasm for passage of electrical signals Dendrites = shorter threads of cytoplasm for receiving signals from other cells Motor end plate = passes signals into muscle to make them contract

34. How do “Nerve Agents” work?

38. How does “Botox” work?

39. Nerves A nerve is a bundle of axons of many neurons (many nerve cells). When you sense things, the message travels: – receptor cell  sensory nerve  spinal cord  brain When you move, the message travels: – Brain  spinal cord  motor nerve  muscle (effector)

41. Reflexes A reflex action is a quick, automatic response to a stimulus. It is involuntary. It does not involve the brain; just the spinal cord.

42. Reflex

43. Reflex Arc A reflex involves a sensory neuron, a relay neuron, and a motor neuron. The relay neuron passes the signal from the sensory to motor neuron inside the spinal cord (NOT in the brain) This pathway is the reflex arc.

46. Reflex Response to Tendon Stretch

47. Pupil Reflex Iris = colored part of eye Pupil = hole in middle of iris Pupil reflex = the pupil gets smaller in bright light and wider in dim light This ensures the right amount of light will hit the retina.

48. Pupil Reflex

50. But how do you control the Iris? Circular muscles = run around the iris Radial muscles = run out from center of iris When circular muscles contract, the iris closes in. When radial muscles contract, the iris opens up.