The Nervous System

1. The Nervous System KEYWORDS(Write these into your journal book and find the definition as part of your weeks homework) Gland, Hormone, Impulse, Nervous system, Effector, Stimulus, Receptor, Neurone, Synapse

2. STARTER ENDOCRINE SYSTEM Name the hormones – Using Figure 2 on page 24 of the Student Book, write down the names of the hormones secreted by the glands shown on the diagram. Time: 10 minutes Working Groups: Your choice of 1, 2 or 3

3. STARTER continued Name the hormones – Have you thought of any others? Time: 10 seconds to add them to your list

4. STARTER answers Pituitary gland – FSH, LH (stimulates the release and maturity of follicles during menstruation) Thyroid gland – Thyroxine(regulates the rate of metabolism) Adrenal gland - corticosteroids and catecholamines including cortisol and adrenaline and small amounts of testosterone(regulates stress levels) Pancreas – peptides (regulates the production of shorter active digestive enzymes) Ovary – oestrogen, progesterone and small amounts of testosterone (regulates the growth of eggs and stabilises the growing foetus during pregnancy) Testis – testosterone (plays a key role in the health and well-being of the man)

5. LEARNING OBJECTIVES • I AM LEARNING TO understand how the body is controlled • I WILL LEARN THAT • The nervous system enables humans to react to their surroundings and coordinate their behaviour. • • Receptors detect stimuli which include light, sound, changes in position, chemicals, touch, pressure, pain and temperature. • • Information from receptors passes along cells (neurones) in nerves to the brain. The brain coordinates the response. • • Many processes in the body are coordinated by chemical substances called hormones. Hormones are secreted by glands and are transported to their target organs by the bloodstream. • I CAN • Explain how the body control’s its functions and responses through hormones (chemicals) and nerves (electrical impulses)

6. Identification of the density of nerve endings– • AIM: To investigate the sensitivity of different areas of the skin. • Method: • 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. • The blindfolded student has to say whether it was one point or two points that touched them. • 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?

7. CONTROL SYSTEMS There are two main control systems in your body. • Nervous system – which has two main sections • central or CNS that is made up of the spinal cord and brain and functions to coordinate all actions of the body • peripheral or PNS that is made up of the bodies nerves and functions to connect the CNS to the rest of the body through neurones. PNS is further divided into • somatic or SNS which is associated with the voluntary control of body movements and is made up of all neurones, sense organs, skin, skeletal muscles • Autonomic or ANS which is associated with the 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) • Endocrine system – which is a system of glands that release a number of signalling chemicals known as hormones.

8. NERVOUS SYSTEM Say what? 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 Endocrine system releases chemical signals that are slow to react but the effects are long lasting. This does not involve the CNS. Messages are carried by the blood.

9. NERVOUS SYSTEM

10. 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.

11. 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! SIMPLES RIGHT!

12. 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 Can you think of any receptors? Nose picks up chemical signals through the nostrils Ear picks up sound waves through the eardrum

13. 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

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

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

16. Multiple-choice quiz

17. SYNAPSES Where two neurones meet, there is a tiny gap called a synapse. Signals cross this gap using chemicals. One neurone releases the chemical into the gap. The chemical diffuses across the gap and makes the next neurone 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

18. presynaptic cell postsynaptic cell What is a synapse? A synapse is a junction between two neurones across which electrical signals pass. The human body contains up to 500 trillion synapses.

19. synaptic vesicle neurotransmitter molecules The release of neurotransmitters When a nerve impulse arrives at the end of one neurone it triggers the release of neurotransmitter molecules from synaptic vesicles.

20. synaptic cleft nerve impulse receptor Continuing the impulse The neurotransmitters diffuse across the synaptic cleft and bind with receptors on the next neurone, triggering another impulse.

21. 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 a mean can be calculated. • Then change around so that everyone gets a turn. Write a report of the experiment. CONCLUSION AND DISCUSSION: What was the accuracy of the measurements, the calculation of means and the control of variables? 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?

22. 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! http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtml

23. 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.

24. The sequence of a reflex arc

25. 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. http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtml

26. The iris reflex

27. 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

28. REFLEX ACTION

29. PASS THE ZAP • Some volunteers get an A4 sheets on which the names of parts of the reflex pathway are to be written. • The students should then arrange themselves in the correct order. • Using a lightning-shaped zap, each student is to talk through their bit of the process as the impulse (zap) gets passed to them.

30. NERVE PATHWAY… Have a go at completing this worksheet effector Sense organ/ receptor

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

32. NERVOUS SYSTEM… answers 4c) sensory receptor in eye – sensory neurone – relay neurone - brain – motor neurone - effector 4a) 37m 55m/s = 0.67s 4b) RT = ds = 20m 40m/s = 0.5s 4d) i) brain, ii) takes too long iii) Stimulus sensory neurone relay neurone motor neurone effector

33. Glossary (1/2) • accommodation –The reflex reaction that keeps the lens the right shape to focus light on the retina. • CNS –The central nervous system, consisting of the brain and spinal cord. • iris –The part of the eye that limits the amount of light entering the eye. • lens –The part of the eye that focuses light on the retina. • motor neurone –A neurone that carries electrical impulses from the CNS to muscles and glands. • neurone – A specialized cell that carries electrical impulses.

34. Glossary (2/2) • neurotransmitter –A chemical that diffuses across synapses to continue an impulse in a connecting neurone. • reaction time –The time taken to respond to a stimulus. • reflex –A fast, automatic protective response. • retina –The part of the eye that contains light receptors. • sensory neurone –A neurone thatcarries electrical impulses from sense organs to the CNS. • synapse– The gap between two connecting neurones.

35. LEARNING OBJECTIVES • I AM LEARNING TO understand how the body is controlled • I WILL LEARN THAT • The nervous system enables humans to react to their surroundings and coordinate their behaviour. • • Receptors detect stimuli which include light, sound, changes in position, chemicals, touch, pressure, pain and temperature. • • Information from receptors passes along cells (neurones) in nerves to the brain. The brain coordinates the response. • • Many processes in the body are coordinated by chemical substances called hormones. Hormones are secreted by glands and are transported to their target organs by the bloodstream. • I CAN • Explain how the body control’s its functions and responses through hormones (chemicals) and nerves (electrical impulses)