Nervous System Your body’s communication network & control center Peripheral Nervous System (PNS)-gathers info from inside & outside the body Central Nervous System (CNS)- receives this info & initiates a response-composed of the brain & spinal cord Messengers & receivers of these transmissions are NEURONS

BASIC STRUCTURE OF NEURON Cell body-contains nucleus & cell membrane Dendrites-branching projections of the cell body, carry impulses into the cell Axon-Threadlike extension carries impulses to & from the cell, at the end of axon is the axon terminal Myelin Sheath-Insulates the axon & speeds up transmission of the impulses Synapse-point of contact at which impulses are passed from one cell to another

Voluntary Actions vs Reflex Actions Impulses passed via the brain What is the chain of events that happens from the instant you hear the phone ring until you pick up the phone? Every time a stimulus—such as a ringing telephone—is detected, the body's neurons send a nerve impulse through the nervous system. If the safety of our body requires a very quick response, the signals may pass directly to a motor neuron for instant, unthinking action. This is a reflex action. Signals sent via the spinal cord reflex action

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REACTION TIME: The Ruler Test The nervous system helps information travel through your body. It consists of the 5 senses, your brain, your spinal column, and the nerves that connect them all together. Suppose your eyes see a baseball sailing toward your head. They send a message about the approaching ball to your brain. This message travels to a part of your brain called the cerebrum through nerves. Your cerebrum sends this information to the cerebellum, which has to choose whether to move away, duck, or put a hand up to catch the ball. It finally decides that you should catch it—after all, you’re wearing your baseball glove! The cerebellum sends this decision as message through other nerves to the arm and hand, activating the muscles used to catch the ball. The time it takes from when your eye first notices the ball to when your arm reaches up to catch it is an example of reaction time. Even though stimuli— or changes in your environment that you react to—travel very quickly along your nervous system as messages, your body doesn’t react instantly. Many athletes spend hours practicing to improve their reaction time. In this activity, you will conduct a simple, measurable experiment (the ruler drop test) to study reaction time and determine how it can be improved with practice.

Problem: How can reaction time be measured and improved? Volunteercm trial 1cm trial 2cm trial 3cm trial 4 cm trial 5cm trial 6 NAME Procedure 1. volunteer sits in a chair with good upright posture 2. volunteer places forearm so it extends over the edge of the table. 3. volunteer to places thumb and index (pointer) finger on either side of the bottom of the vertically placed ruler. The number “ 1 ” should be on the bottom, the “ 30 ” near the top. 4.Let your volunteer practice holding the ruler with those two fingers. 5.Now, ask the volunteer to remove their fingers from the ruler while you continue hold it so that the bottom of the ruler is at a height of 2cm above their fingers. 6.Tell your volunteer that you will release the ruler without telling them. Their job will be to catch it with the thumb and forefinger as soon as they senses it dropping. 7.Drop the ruler. When your volunteer catches it, record the number on the ruler displayed just over their thumb. The lower the number, the faster their reaction time. 8.Conduct several trials with the same volunteer. 9.Make sure to record the results for each trial in a table similar to the following:

Results Your results will vary depending on technique and which volunteers you used, but you should expect that many of your volunteers will show a slight improvement with practice. Why? When we begin to acquire a new physical skill through repetition, our nervous system creates new neural pathways. Here’s an example: when we practice something like catching a ruler over and over again, all the members of that neural pathway (eye, brain, muscles) become more well-connected and efficient. This phenomenon is often referred to as muscle memory. However, no matter how good your muscle memory for this task becomes, it will always take some time for the falling ruler to travel as a message from your eyes to your brain and from your brain to your fingers!