Ch. 48 Vocabulary Terms (optional) 10% bonus

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1 Neurons Ch. 48 Chapter 48 Neurons Required Chapter tasks that will be turned in: Reading & Activity questions (20 pts) Self-Quiz (10 pts) Vocabulary (optional) (10% bonus) Take the online Quizzes & Tests for this Chapter (optional) Ch. 48 Vocabulary Terms (optional) 10% bonus acetylcholine axon axon hillock biogenic amine depolarization dopamine endorphin epinephrine excitatory postsynaptic potential (EPSP) gamma aminobutyric acid (GABA) ganglion gated ion channel glia glutamate hyperpolarization interneuron motor neuron myelin sheath neuropeptide neurotransmitter nodes of ranvier norepinephrine peripheral nervous system (PNS) postsynaptic cell presynaptic cell refractory period resting potential saltatory conduction Schwann cell sensory neuron serotonin spatial summation synapse synaptic cleft synaptic terminal synaptic vesicle temporal summation voltage-gated ion channel 1

2 Reading Questions Read the chapter and Complete the online activities to answer the questions. 1. What makes a cone snail one of the deadliest organisms in the ocean? Define a neuron and explain why cone snail venom interferes with neuron function. 2. Neurons can be placed into three groups, based on their location and function. Type of Neuron Function Sensory Motor Neurons Connect the sensory and motor neurons; integrate information with the brain or spinal cord; entirely w/in the CNS. 3. Which division of the nervous system includes the brain and spinal cord? Label the diagram and explain how the CNS and the PN work together This sketch shows two neurons. Label the following: cell body, dendrites, axon, synapse, presynaptic cell, postsynaptic cell, synaptic vesicles, synaptic terminal, and neurotransmitter. 2

3 Watch the BioFlix video: How Neurons Work. Complete the Activity: Nerve Signals: Action Potentials 5. All cells have a membrane potential across their plasma membrane. What is the typical resting potential of a neuron? On the sketch below, label the following: outside cell, inside cell. Show where the concentrations of Na + and K + are highest. How are these concentration gradients of Na + and K + maintained? 6. Signal conduction occurs along the axon of a nerve cell in the following way: If positively charged ions flow out, the difference in charge between the two sides of the membrane becomes greater. What is the increase in the magnitude of the membrane potential called? In a resting neuron, the of the membrane is charged compared to the inside. When a stimulus is applied, voltage-gated sodium ion channels will, allowing positively charged ions to flow in. The membrane is said to depolarize. If depolarization causes the membrane potential to drop to a critical value called the a wave of depolarization called will follow. What is the critical value in mammalian cells? The all-or-none response to stimuli is a result of the fact that if the threshold is reached the depolarization of the membranes causes the voltage-gated Na+ channels to open. This results in a feedback loop that triggers further depolarization of the membrane triggering an potential. 7. What causes the membrane potential to be restored to its normal resting value? What is this period following the action potential called? 3

4 8. Analyze Figure a. Label Na+, K+, and their respective ion channels. b. Label the Resting state figure. Are the Na+ and K+ channels open, or closed? c. Label Depolarization. What triggers depolarization? What channels open? What occurs if the depolarization threshold is reached? d. Label Stage 4 in the figure Repolarization. How is the charge on the membrane reestablished? e. Label these regions of the graph: x- and y-axes, threshold, resting potential, depolarization, action potential, and repolarization. f. Draw in another line on the graph to show what the change in membrane potential would look like if a stimulus were applied that did not reach the depolarization threshold. 4

5 9. What factors affect the speed of action potentials? Name and describe the special adaptation in vertebrates that enables fast conduction in narrow axons? 10. What are the two types of glial cells that produce myelin sheaths? Use the figure below to explain how a myelin sheath speeds impulse transmission? Also include a discussion of saltatory conduction and nodes of Ranvier in your response. 11. In the disease multiple sclerosis, the myelin sheaths harden and deteriorate. How would this affect nervous system function? Neurons communicate with other cells at synapses 12. What is a synapse? Is this type of signal conducted electrically or chemically? Explain. 5

6 13. Analyze Fig When the wave of depolarization arrives at the synaptic terminal, Ca 2+ ion channels open. What occurs to the synaptic vesicles as the Ca 2+ level increases? What is contained within the synaptic vesicles? 14. Label the figure below: synaptic vesicle, neurotransmitter, calcium ion channel, presynaptic membrane, postsynaptic membrane, and synapse. 15. Summarize the 6 steps of transmitting an action potential from one cell to another across a synapse. 16. There are two classes of neurotransmitters: and. Describe the effect of each type on the postsynaptic membrane. 17. What determines whether an action potential is generated in the posynaptic neuron? Define and explain summation. 6

7 18. is the most common neurotransmitter in both vertebrates and invertebrates, and it is released by the neurons that synapse with muscle cells at the neuromuscular junction. If you look ahead to Chapter 50, Figure 50.29, you will see a synapse between a neuron and a muscle cell, resulting in depolarization of the muscle cell and its contraction. Explain the general way in which this neurotransmitter functions Describe the relationship of each of the following to the functioning of acetylcholine. a. Nicotine from cigarette smoke - b. Toxins from the bacterium, Clostridium botulinum c. Heart muscle cells - 7