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Chapter Cha Chapter Chapte hapte apte ter te er Stimuli and 11 Responses What do you know about the human nervous system? How are stimuli related to responses in humans? How are stimuli related to responses in plants? What is the importance of responses...

Chapter Cha Chapter Chapte hapte apte ter te er Stimuli and 11 Responses What do you know about the human nervous system? How are stimuli related to responses in humans? How are stimuli related to responses in plants? What is the importance of responses to stimuli in animals? Let’s study Human nervous system Stimuli and responses in humans Stimuli and responses in plants Importance of responses to stimuli in animals 2  1.1 Human Nervous System In a game of badminton… 2 The brain interprets the impulse, estimates the speed 1 The movement of of the shuttlecock and determines the direction and the shuttlecock the pattern of body serves as a stimulus movement. that is detected by the eye. An impulse is triggered and 3 The brain then sends sent to the brain. impulses to the hand and leg muscles to respond. The human nervous system is an important control system in body coordination. Other than sight, thinking and body movement, the human nervous system also controls and coordinates organ functions in the body and maintains a balanced internal environment through a process. What is this process? Structure of the Human Nervous System Look at Figure 1.1. The human nervous system consists of: Brain Cranial nerves Peripheral nervous Central system nervous Spinal nerves system Spinal cord Peripheral nervous system consists of: t

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: nerves connecting the spinal cord to the , skeletal muscles. 7( Figure 1.1 Human nervous system 4 1.1.1  Chapter 1: Stimuli and Responses Functions of the Human Nervous System The human nervous system controls and coordinates organs and parts of the body. The human nervous system: detects stimuli sends information in the form of impulses interprets impulses produces appropriate responses Photographs 1.1, 1.2 and 1.3 show examples of daily activities that involve detection of stimuli and production of responses to the stimuli detected. State the stimulus and response in each of the daily activities shown. Photograph 1.1 Collecting garbage Photograph 1.2 Sneezing Photograph 1.3 Surfing the Internet 1.1.1 5 Voluntary and Involuntary Actions The responses of the human body to stimuli can be divided into voluntary actions and involuntary actions. Observe the examples of responses of the human body in Figure 1.2. RAFIQ (a) Reading a book (b) Withdrawing hand from (c) Peristalsis in oesophagus a hot object Figure 1.2 Examples of responses of the human body Based on Figure 1.2, which response is a voluntary action and which is an involuntary action? Voluntary Actions Voluntary actions are conscious actions and conducted under one’s will. All voluntary actions are controlled by the brain. Examples of voluntary actions include reading, writing, speaking, eating, drinking, walking, running and exercising. Figure 1.3 shows the pathway of impulse in a voluntary action. Affector (receptor) Stimulus ne r v in human ear e im puls e Phone rings e puls e im Effector ne r v Response (muscle or gland) Brain Touch the screen Direction of the pathway of impulse from the affector (receptor) to the effector Figure 1.3 Pathway of impulse in a voluntary action Let us learn more on voluntary actions by carrying out Activity 1.1 on page 7. 6 1.1.2  Chapter 1: Stimuli and Responses Activity 1.1 Inquiry-based activity Measuring the reaction time by catching a free-falling ruler (voluntary action) Aim: To measure reaction time Apparatus Half metre rule Instructions 1. Work with a partner. 2. Ask your partner to hold the end of a half metre rule as shown in Figure 1.4. Safety 30 Precautions 50 48 46 44 40 42 38 Make sure that the hand used 36 34 32 30 to catch the ruler remains 28 26 24 stationary on the table. 22 18 20 16 Be careful when releasing or 14 12 10 catching the ruler. 8 6 4 2 0 Table Figure 1.4 3. Place your hand at the end of the ruler close to the zero mark without touching it as shown in Figure 1.4. 4. Your partner will release the ruler without warning and you must try to catch the ruler as quickly as possible. 5. Record the distance the ruler fell, x, that is, the scale on the ruler when you catch it. The distance, x, is the measurement of your reaction time. 6. Repeat this activity four times. Then, calculate the average distance, xaverage. Questions 1. In this activity, state the stimulus and its response. Is the response a voluntary action or an involuntary action? Explain. 2. Why is the distance the ruler fell considered as the reaction time? 3. Explain the difference in the reaction time among the students in the class. 4. What is the importance of reaction time in our daily life? Conclusion Draw a conclusion on the reaction time of the students in your class. 1.1.2 7  Involuntary Actions SCIENCE INFO Involuntary actions are actions that occur immediately without conscious control or prior thoughts. Involuntary actions can be classified into two. Involuntary actions Medulla oblongata Involving medulla Involving spinal cord Spinal cord oblongata (reflex actions) Heartbeat Withdrawing hand Breathing when it accidentally touches a hot object Peristalsis Withdrawing foot when it accidentally steps on a sharp object Secretion of saliva Sneezing when dust enters the nose Affector (receptor) Hot object Spinal cord Effector Direction of impulse Direction of impulse from the affector (receptor) to the effector Figure 1.5 Pathway of impulse in an involuntary action (reflex action) Let us learn more on involuntary actions by carrying out Activity 1.3 on page 9. Activity 1.2 To create a presentation on: the parts involved in the transmission of impulse from the affector ICS to the effector Innovation- based activity the pathway of impulses in voluntary and involuntary actions Instructions 1. Work in groups. 2. Each group is required to create a presentation to illustrate the following: The parts involved in the transmission of impulse from the affector to the effector The pathway of impulses in voluntary and involuntary actions 8 1.1.2  Chapter 1: Stimuli and Responses Activity 1.3 Inquiry-based activity Detecting changes in the size of the pupil in the eye towards light intensity (involuntary action) Aim: To observe changes in the size of the pupil of the eye towards different light intensities Apparatus Mirror and lamp Instructions 1. Identify the pupil of the eye in Figure 1.6. Pupils Figure 1.6 2. Observe the pupil using a mirror in bright light. Sketch the size of the pupil. 3. Observe the pupil in dim light. Sketch the size of the pupil. 4. Compare and contrast the size of the pupils in bright and dim lights. Questions 1. In this activity, state the stimulus and its response. Is the response a voluntary or an involuntary action? Explain. 2. What is the relationship between the size of the pupil and light intensity? 3. What is the importance of this response? Conclusion Draw a conclusion about the changes in the size of the pupil towards light intensity. SCIENCE INFO The pupil in the human an eye is circular. Is the pupil in other animals’ an eye circular as well? (a) Goat: (b) Stingray: (c) Crocodile: (d) Squid: Rectangular Crescent Vertical slit W-shaped 1.1.2 9  BRAIN Importance of the Network of Human TEASER Nervous System in Daily Life Other than the nervous system, The network of the human nervous system controls and what other body systems help in body and internal organ coordinates the organs and parts of the body to carry movements? out processes in the body such as breathing and body movements. A damaged nervous system normally causes a person to become temporarily, partially or completely paralysed. For example, if the nerves in the muscles of a leg or hand - Science, Technology, Engineering, Mathematics are injured, the person will face difficulty in moving his leg or hand. In the case of a more serious problem, he might Humanoid robot have to depend on machines to carry out his physiological 5 processes such as breathing or heart beating. *( : Humans are blessed with a nervous system, so they should use and take good care of it. ,.      7( Photograph 1.4 Partially- Photograph 1.5 Patient using a breathing paralysed individual machine Formative Practice 1.1 1. State two main parts of the human nervous system. 2. (a) What is voluntary action? Give one example of a voluntary action. (b) What is involuntary action? Give one example of an involuntary action. 3. What happens if a person has brain injury? 4. What is the importance of the network of human nervous system in life? 10 1.1.3