Human Nervous System PDF

CHAPTER 1: STIMULUS AND RESPONSES The Human Nervous System 1. The nervous system is one of the systems found in humans. 2. The human nervous system consists of a network of nerve cells 3. The human nervous system is divided into two parts: Central nervous system (CNS) Peripheral nervous s...

CHAPTER 1: STIMULUS AND RESPONSES The Human Nervous System 1. The nervous system is one of the systems found in humans. 2. The human nervous system consists of a network of nerve cells 3. The human nervous system is divided into two parts: Central nervous system (CNS) Peripheral nervous system (PNS) 4. The function of the nervous system is to detect stimuli and send information in the body as well as coordinate body activities. Diagram 1.1: The human nervous system 5. How does the human nervous system work? Imagine someone presses the doorbell. You will be able to hear the bell ringing. In this case, sound is the stimuli. How does your brain react to the sound? The sound that you heard is detected by your ears. Your ear is called the sensory organ. Sensory organs have only 1 function, which is to detect stimuli. The ear will then generate nerve impulse (electrical signal) to the brain The brain then decides what to do by sending a new nerve impulse (electrical signal) to effector to carry out an action.  In this case, the muscles are the effectors. We will use our muscles to walk over to the door and open the door for the person who rang the bell. Walking over to the door and opening the door is known as a response. Here is another example: Imagine, when you look up into the sky and the sun is glaring at you. Your eyes close immediately because of the bright light. Why does this happens?  When too much light (stimulus) enters your eyes, the eyes sense it and sends nerve impulses (electrical signals) to the spinal cord. The spinal cord then sends new nerve impulses (electrical signals) to the muscles on your eyes to close so that lesser light can enter. 6. The brain coordinates many responses every day. 7. There are two types of responses: Voluntary responses (can be controlled by the brain) Involuntary responses (cannot be controlled by the brain) *voluntary responses are also known as voluntary actions *involuntary responses are also known as involuntary actions 8. Example of a voluntary action: 9. Example of an involuntary action: 10. Voluntary actions and involuntary actions are very important in our daily lives. 11. We depend on voluntary actions to carry out our daily tasks. 12. We depend on involuntary actions to survive. Activities in Class to Show the Importance of Voluntary & Involuntary Actions Catching a ruler (voluntary action) Changing size of pupils in our eyes in response to light Stimuli and Reponses in Humans 1. A sensory organ is an organ that detects stimuli. 2. Humans have 5 sensory organs which are the skin, nose, tongue, ears and eyes 3. The ability to sense is the ability of sensory organs to detect stimuli. 4. Each sensory organ is responsible for a different sense. 5. Therefore, humans have five senses which are touch, smell, taste, hearing and sight.