2 Learning objectivesDefine the nervous system and understand how it worksThe general function of the nervous systemThe pathway by which sensory information reaches the brainThe basic principles of neuronal communication
3 Clicker question #1Which of the following is controlled by the nervous system?ReadingDigestionKnee-jerk reflexBreathingAll of the aboveThe answer is E. The aim of this question is to engage students in thinking about the diverse functions of the nervous system.Reading (A) is a motivate behavior that most students will get right.Digestion and Breathing (B and D) are necessary for life and also controlled by the nervous system.Knee jerk reflex is an involuntary, instantaneous response but controlled by the nervous system.Depending on the clicker question response, misconception will be addressed accordingly.
4 Other Modulatory Neurons Nervous systemThe Central Nervous System (CNS): brain & spinal cordThe Peripheral Nervous System (PNS): sensory receptors & motor effectors.The communication between CNS and PNS.The Central Nervous System (CNS): brain and spinal cordThe Peripheral Nervous System (PNS): sensory receptors and motor effectorsSensory receptors detect changes in the environment and communicates them to the CNS.The CNS, in turn, communicates desired behavior such as muscle movement to the PNS (via motor nerves) using motor effectors.Dopaminergic NeuronsKenyon cellsOutput NeuronsOther Modulatory Neurons
6 Concept mapping/sorting You are about to enjoy a hot steaming cup of espresso freshly brewed and prepared for you.Place the post it cards given to your group in three categories on the white board:CNS, PNS, and/or Both.Work in groups of 4
7 You smell the espresso You see the coffee I am sleepy I need that coffee nowSip the coffeeTaste the coffeeThis coffee is bitterThe Goal of this activity is for students to think about how these small sub-activities of the coffee drinking experience involve the nervous system. Students will work in groups to discuss how each of these activities involve the CNS, PNS and both. To further extend this activity they can divide the activities as which part involves the sensory system, CNS and motor neurons/muscle effectors. (The instructor can choose to make this activity big or small but we allotted 5 minutes to it and the students were able to finish it).Some of these are clearly CNS functions: I need that coffee now, I am sleepyPNS: You pick up the cupCNS and PNS: Coffee feels hot, taste the coffee, sip the coffee, Espresso tastes good etc.One thing that students will realize is that most activities involve both the CNS and PNS because these systems work closely together to accomplish everyday tasks. The instructor can take pictures of each group’s work and post them online to start a discussionYou pick up the cupCoffee feels hotEspresso tastes good
8 Clicker question #2Which of the following activities involve Central Nervous System (CNS)?Knee-jerk reflexUsing the clickerPupil DilationAll of the aboveThe correct answer is B. A and C are involuntary actions and do not involve the CNS (although they DO involve the PNS).
9 A neuron and its parts Electrical Signal Myelin Axon Chemical Signal NikkiThe main cellular unit of the nervous system is the neuron. A neuron is a cell that has a very specific shape to perform its task of transferring information from the environment, to the brain, and back to the periphery. Information comes in at the dendrites then is passed through the cell body and down the axon where it reaches the next neuron at a synapse. The signal that is passing through the neuron itself is electrical but once it gets to the synapse the electrical signal causes the release of chemicals to communicate with the next neuron. Additionally, the axon is covered with myelin, which insulates it and allows the signal to jump from node to node between myelin, rather than moving all the way along the axon, which could be several feet long.Dendrites
10 Clicker Question #4Have you ever stubbed your toe and said “Ouch!” before it actually started hurting? With your knowledge of the nervous system, how might you explain this phenomenon?Your response is a reflex that doesn’t involve the CNS (Central Nervous System)Saying “Ouch” might make it hurt lessC. Your toe nerves are directly connected to your mouth nervesD. Pain sensation travels through un-myelinated axons while normal touch travels through myelinated onesThe correct answer is D. because pain information is transduced from the periphery to CNS by C-fibers that are unmyleinated (unlike most other fibers in the nervous system). The lack of myleination reduces the speed of information transfer. On the other hand touch itself is conducted by nerve fibers that are myleinated. A. is incorrect because the CNS is involved. B. is incorrect because even if it were somehow true, that has nothing to do with why you can say “ouch” before you feel the pain. C. is incorrect because these toe nerves are connected to the sensory area of the brain, not to the mouth.This is a higher bloom level question that allows students to think about this actual phenomena that we have all encountered but don’t understand why. The knowledge of the mylein, CNS and PNS together will help students thinks about how 2 pathways one that carries pain information while the other that carries touch information reach the CNS but one goes faster and hence the ouch response.Another concept that this question addresses is that of what is a reflex and what is a perception of pain. Reflex is almost instantaneous response to a stimuli.
11 Activity Un-myelinated axon Synapse Neuron B Myelinated axon Synapse To illustrate how neuronal signals are transferred and to demonstrate the purpose of myelin, the instructor will split the class up into 2 groups to represent a myelinated axon and a non myelinated axon.The myelinated axon has 4 people standing several feet apart who represent the nodes where the electrical signal is passed, while the un-myelinated axon has 10 people standing right next to each other because the electrical signal has to move down the entire axon. The first person in each group will receive a green ball representing the electrical signal, then the students will pass the ball to their neighbor until it reaches the axon terminal. The person at the axon terminal/synapse with Neuron B holds a red ball representing the chemical signal. They cannot pass this signal on to Neuron B until they have received the green electrical signal. The goal is to pass the signal to Neuron B as quickly as possible. A Teaching Assistant could be Neuron B and announce which axon delivered the signal faster.Myelinated axonSynapse
12 Clicker Question #3What is the fastest way to pass a signal through a neuron?With chemicalsFrom node to nodeBy diffusionVia radioactivityThe correct response is the B. A. is how the signal is passed between neurons, not through an individual neuron. C. would be much slower – imagine how long it would take for ions to diffuse all the way from your spinal cord to your toe. D. is irrelevant because there is no radioactivity in neurons.