The Nervous System

1. The Nervous System Gland, Hormone, Impulse, Nervous system, Effector, Stimulus, Receptor, Neurone, Synapse

2. CONTROL SYSTEMS There are two main control systems in your body. • Nervous system – a system of electrical impulses organized into 2 main sections • Endocrine system – a system of glands that release signalling chemicals, or hormones

3. Nervous system central or CNS: spinal cord and brain; functions to coordinate all actions of the body peripheral or PNS: body’s nerves; functions to connect the CNS to the rest of the body through neurons. • PNS is further divided into • somatic or SNS: voluntary control of body movements and is made up of all neurons, sense organs, skin, skeletal muscles • Autonomic or ANS: involuntary control of body movements such as reflex and controls such things as heart rate, body temperature, digestion etc. The ANS is further divided into • Parasympathetic nervous system works in actions that do not require a fast response (fight or fight response) • Sympathetic nervous system works in actions that do require a fast response (rest and digest response)

4. Say what? NERVOUS SYSTEM CNS PNS Nervous system releases electrical impulses that are quick but the effects are short lived and it involves the CNS (either just spinal cord or both spinal cord and brain) messages are carried by neurones SNS ANS Parasympathetic Sympathetic

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

6. Parts of the nervous system For example; If you smell something burning… • Your nose (receptor) detects the stimulus (smell) • Nerve fibres send the message to the brain • Your brain then sends a message to move your body away or to put out the fire! SIMPLE RIGHT!

7. Lets look at some bits more closelyRECEPTORS • Receptors are sensors on the body that detect stimuli • They convert stimuli into electrical signals (messages) called impulses. Eyes pick up light waves through the retina Nose picks up chemical signals through the nostrils Ear picks up sound waves through the eardrum Can you think of any receptors?

8. EFFECTORS 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 • a gland releasing a hormone into the blood

9. NERVE FIBRES • Nerve fibres are bundles of nerve cells (neurons) that pass on electrical signals (impulses) to the brain. • From the brain, nerve fibres send impulses to effectors (muscles).

10. NEURONS 3 types of neurons • Sensory neuron – carries impulses from the receptors to the spinal cord. • Relay Neuron – carries impulses to and from the spinal cord and the brain • Motor Neuron – carries impulses from the brain to the effector

12. SYNAPSES Where two neurons meet, there is a tiny gap called a synapse. Signals cross this gap using chemicals. One neuron releases the chemical into the gap. The chemical diffuses across the gap and makes the next neuron transmit an electrical signal. http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev2.shtml Watch this video on synapses then draw a flow chart of the process

13. The stick drop test! METHOD: • Working in pairs, one student holds a metre rule vertically at the zero end, between the thumb and forefinger of another student, so that the 50 cm mark is level with the top of the forefinger. • Without warning, the first student drops the rule and the second student attempts to catch it between the thumb and forefinger, noting the distance on the ruler just above the forefinger. • Repeat several times, so that an average can be calculated. • Then change around so that everyone gets a turn. • Create a data table to record your results. CONCLUSION AND DISCUSSION: Do you think the measurements were accurate? Explain why/why Identify the parts of the body involved. What senses are being used? Can we train ourselves to react more quickly? Does practice make perfect? Can we alter reflex actions? – think of a situations where it is possible to alter the automatic response (not dropping a hot object, deliberately breathing more slowly, etc.). Are there some reflex actions over which we have no control? Name some examples.

14. REFLEX ARC • When your body needs to react to something very quickly (to protect itself) it uses a reflex arc (spinal reflex). • Instead of sending impulses from the receptor Spinal cord brain spinal cord effector • It sends impulses from the receptor spinal cord effector…Yup it bypasses the brain!

15. QuestionsHow are impulses sent through nerve cells?What is a synapse?What are two types of effectors?

16. ANSWERS • Electrical impulses along neurones, chemical (neurotransmitters) across the synapse. • The microscopic gap between two neurones. • By chemicals called neurotransmitters. • To pass the impulse onto the correct motor neurone. • Glands or muscle that produce the effect or make a response.

17. REFLEX ACTION The way the iris in our eye adjusts the size of the pupil in response to bright or dim light is also a reflex action.

19. Inside the eye cornea protects eye surface and focuses light rays suspensory ligaments hold lens in place lens focuses lighton retina retina senses light iris regulates amountof light entering eye ciliary muscles optic nerve transmits impulses to the brain change shape of the lens