Nervous System. Lesson Structure вЂў Lesson 1 вЂ“ Nervous system and the reflex arc. вЂ“ Reaction time practical. вЂў Lesson 2 вЂ“ Hearing and waves. вЂ“ Worksheets вЂ“ Senses movie. Lesson Objectives. 1. List the sense organs and their receptors. 2. Describe the difference between a controlled reaction and a reflex action. 3. Label and explain the reflex arc. The Nervous System. вЂўThe nervous system is composed of 5 sense organs, neurones, brain and spinal cord. вЂўSense organs detect stimuli and the Central Nervous System (CNS) coordinates a response. Sense organ Receptors Eyes Light Ears Sound and Balance Nose Smell Tongue Taste Skin Pressure and Pain The CNS (central nervous system) consists of the brain and spinal cord. Controlled Actions. Stimulus Receptor Cells Sensory Neuron Spinal Cord вЂў This is the way we usually respond to changes in the world around us. вЂў The process takes about 0.7 seconds. Neurons: вЂў Sensory neurons вЂ“ Carry electrical impulses from the receptors to the CNS вЂў Relay Neurons вЂ“ carry electrical impulses from sensory neurons to the motor neurons (Only found in CNS) вЂў Motor neurons вЂ“ carry impulses from the CNS to the effectors. Motor Neuron Brain Effector Response Effectors can be muscles or glands: They produce a response. Reflex Actions. Stimulus Receptor Cells Sensory Neuron Spinal Cord вЂў Reflex actions are automatic, they happen without you thinking about them. вЂў They do not involve the brain, therefore they are much quicker (around 0.2 seconds) вЂў They are usually used to avoid damage. Motor Neuron Effector Response Reflex Arc. 1. Stimulus is detected by receptor. 2. Sensory neurone to relay neurone to motor neurone. 3. Effector produces a response. Synapse Receptor Sensory Neuron Relayneurone. Neuron Relay Muscles responds by contracting. Gland responds by secreting. Motor Neuron Effector (e.g. Muscle) The Eye. Very bright light can damage your eye вЂ“ so you have a reflex to protect it. вЂў In bright light, circular muscles contract to make pupil smaller (Lets less light in) вЂў In dim light, radial muscles contract making pupil larger (Lets more light in). The Eye. вЂў Focusing the eye, another reflex: The eye focuses by changing the shape of the lens, this is called accommodation. Binocular Vision. Bi = two Ocular = vision вЂў Having two eyes which work together is known as binocular vision. вЂў This allows us to judge speed and distances. вЂў Handy for crossing the road! вЂў ItвЂ™s only binocular if your eyes are on the front of your head. Summary Questions. вЂў Match the statements: Part of the nervous system Function Receptor cells Cause a response Effectors Carry electrical impulses Neurons Decides on a response. Brain Detects changes in your environment. Are the following reactions controlled or reflex? 1. 2. 3. 4. Pupils in your eyes shrinking in bright light. _______________________ Tying your show lace. __________________ Signing your name. __________________ Taking your hand of a hot plate. _____________________ Hearing and Waves. Lesson Objectives вЂў Describe how sound travels in longitudinal waves. вЂў Understand how excessive sound can affect hearing. вЂўWhen a drum is hit, it vibrates. вЂўThe vibrations make the air molecules parallel to the drum vibrate. вЂўThe vibrating air molecules cause neighbouring particles to also vibrate вЂўThis continues out ward from the drum in a longitudinal wave. Sound can travel anywhere there is a particles; through solids, gasses and liquids. Therefore sound cannot travel through space as it is a vacuum. Rarefaction Compression As the vibration passes, some particles are squashed together. This is called a compression.. In other places particles spread out. This is called rarefaction. вЂў We measure how quickly something vibrates (itвЂ™s frequency) in hertz. вЂў 1 cycle per second = 1 hertz. вЂў Humans can only hear between 20 and 20,000 hertz. вЂў Noise levels are measured in decibels. вЂў For ever 10 decibel increase the sound is 10x louder. i.e. 60 decibels is ten times louder than 50 decibels. Prolonged exposure to loud sounds damages your hearing. вЂў Tinnitus (High pitched ringing in the ears). вЂў You can lose the ability to hear certain frequencies (common to lose the ability to hear conversations). Summary Questions 1. Complete these sentences by choosing the right word. a) Sound waves travel as Longitudinal/electromagnetic waves. b) With Longitudinal waves, particles vibrate parallel/at right angles to the way the energy travels. Explain why sounds cannot travel through space.