PSA 6

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Indiana University, Purdue University, Indianapolis *

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Mechanical Engineering

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Dec 6, 2023

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Pre-Session Assignment (PSA) #6 Name ________Makenna Hammack__________________ Complete the vocabulary-matching sections and at least the first three objectives for each chapter. Doing so will prepare you for recitations and for the quizzes. You are highly encouraged to complete the rest of the objectives to keep you on track and so you can ask for clarification during recitation. All answers can be found in the textbook, even if a section has not yet been covered in lecture. Please complete and turn in one hour before the designated weekly recitation time via canvas. Chapter 41 Objectives: Neuronal Signaling 1 __A__ stage in the repolarization time of an action potential when an additional repolarization event is not possible __C__ a branch of an axon __F__ an event that results in the depolarization and formation of an action potential __H__ an event that results in the hyperpolarization of a neuron and the prevention of an action potential __E__ motor neuron __B__ sensory neuron __D__ occurs in unmyelinated axons and is continuous along the length of the axon __G__ support cells of the CNS (not conducting cells) __J__ cell that myelinates neurons in PNS __L__ the neuron leaving a synapse __N__ stage in the repolarization time of an action potential when an additional depolarization event is possible but the threshold level will be higher than during a resting transmembrane potential __I__ combining incoming and outgoing information __K__ cell that myelinates neurons in the CNS __R__ channels that open and close based upon the charge difference across the membrane __O__ movement of an action potential along a myelinated axon where the action potential only occurs at the nodes __Q__ electrical charge difference across a membrane __L__ the neuron leading up to a synapse (the one coming into the synapse) __P__ electrical value at which the voltage-gated sodium channels will be stimulated to open resulting in depolarization A. Absolute Refractory Period B. Afferent Neuron C. Collateral D. Continuous Conductance E. Efferent Neuron F. Excitatory Post Synaptic Potential G. Glial Cells H. Inhibitory Post Synaptic Potential I. Integration J. Neurolemmocyte K. Oligodendrocyte L. Postsynaptic Neuron M. Presynaptic Neuron N. Relative Refractory Period O. Saltatory Conductance P. Threshold Q. Transmembrane Potential R. Voltage-activated Channels

1. Describe the structure of a typical neuron (multipolar) and give the function of each of its regions/parts ( drawing helpful! ) 1.) Dendrites: a. Branches of a neuron that receive and conduct nerve impulses toward the cell body b. Typically short, highly branched processes specialized to receive stimuli and send signals to the cell body 2.) Cell Body: a. The large portion of a neuron that contains most cytoplasm, the nucleus, and most of the other organelles b. 3.) Axon Collateral: a. When axon divides b. Allows individual neurons to make contacts with multiple neurons within a target and multiple targets 4.) Synaptic Terminals: a. A bulb at the end of an axon in which neurotransmitter molecule are stored and released 5.) Nucleus: a. Contains the nucleolus and chromosomes, necessary for coded production of proteins within the cell 6.) Axon: a. The long extension of the neuron that transmits nerve impulses away from the cell body b. May be 1m or mare in length 7.) Nodes of Ranvier: a. A gap in the myelin sheath of a nerve, between adjacent Schwann cells 8.) Schwann Cell: a. Supporting cells found in nervous tissue outside the central nervous system; produce the myelin sheath around peripheral neurons b. Schwann cell structures: i. Cytoplasm of Schwann Cell: ii. Axon: 1. Forms a myelin sheath by wrapping its plasma membrane concentrically around the inner axon iii. Myelin Sheath: 1. The white, fatty material that forms a sheath around the axons of certain nerve cells, which are then called myelinated fibers. iv. Nucleus: 1. Stored information for the cell 9.) Terminal Branches: a. The smaller extensions of axon collaterals 2

2. Describe the generation of an action potential and draw and label the events that occur during an action potential, compare and contrast the role of sodium and potassium voltage-gated channels in the generation of an axon potential, and explain what happens if either is blocked or stimulated Action Potential 1.) Generation a. When voltage reaches threshold level b. When a membrane of a neuron depolarizes by about 15mV to a potential of about -55mV, when depolarization is greater than -55mV, the threshold level is reached, and an action potential is generated i. Spike: the sharp rise and fall of the action potential ii. Positive feedback system: a system in which a change in some steady stage triggers a response that intensifies the changing condition iii. Repolarization: The process of returning membrane potential to its resting. Level iv. All-or-none response : the principle that no variation exists in the strength of a single action potential; only a stimulus strong enough to depolarize the membrane to its critical threshold level results in transmission of an action potential v. Continuous Conduction: the smooth progressive impulse transmission (occurs in unmyelinated neurons) vi. Saltatory Conduction : The transmission of a neural impulse along a myelinated neuron; ion activity at one node depolarizes the next node along the axon 2.) Location a. Neurons, muscle cells, and a few cells of the endocrine and immune system 3.) Blocked a. No signal going to the central nervous system 4.) Stimulated a. Produces nerve impulse b. Allows diffusion of ion channels Sodium and Potassium voltage-gated channels 1.) Generation a. When an action potential sends out a signal 2.) Location a. Neurons, cardiac and skeletal muscle cells b. As well as glial and neuroendocrine cells 3.) Blocked a. Prevent sensory communication between the airways and brainstem 4.) Stimulated a. Allows K+ to enter and exit and Na+ to enter an exit ion channels of a cell 4

3. Compare and contrast an absolute refractory period with a relative refractory period Absolute Refractory Period 1.) It cannot transmit another action potential no matter how great a stimulus is applied because the voltage- activated Na+ channels are inactivated Relative Refractory Period 1.) The axon can transmit impulses, but the threshold is higher (less negative). Even with the limits imposed by their refractory periods, most neurons can transmit several hundred impulses per second. 2.) Lasts for a few more milliseconds 4. Describe the processes involved in neural signaling: reception, transmission, integration, and action by effectorsth 5. Compare and contrast neurons according to their structure [unipolar, bipolar, and multipolar] and their functional roles 6. Name the main types of glial cells and describe the functions of each 7. Explain how the neuron develops and maintains a resting potential (transmembrane potential) and understand what happens if any the parameters (permeability or ion concentration) are changed 8. Compare and contrast three types of ion channels in neuron membranes 9. Describe the involvement of positive and negative feedback in nerve conductance 10. Describe the all-or-none response and what determines the intensity of a sensation 5

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