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Concepts and definitions
1. What are the four main parts of the neuron?
Answer: The four main parts of the neuron are the soma (cell body), axon (carries the signal), dendrites (receive inputs), and terminals (output branches). You can read more about this topic in Section 17.1.
2. In what form is information encoded by neurons?
Answer: The unit of signalling is the all-or-none action potential, and the strength of the stimulus is signalled by the frequency of action potential discharge—frequency code. Section 17.3 will help you understand this topic.
3. Which ion is the main determinant of the resting potential?
Answer: The ion that is most determinant of the resting potential is potassium, since this is the ion to which the membrane is mainly permeable. Section 17.4 will tell you more about this topic.
4. What are the two main structural features that determine the conduction velocity along an axon?
Answer: The two main structural features that determine the conduction velocity along an axon are the diameter of the axon and the presence/absence of a myelin sheath. Section 17.6 has more on this topic.
5. What are the four main factors that affect post-synaptic summation?
Answer: The four main factors that affect post-synaptic summation are temporal and spatial summation, synaptic strength, and the occurrence of IPSPs as well as EPSPs. Section 17.6 explains more about this topic.
6. What are the two main classes of post-synaptic receptors?
Answer: The two main classes of post-synaptic receptors are ionotropic and metabotropic receptors. You can read more about this in Section 17.6.
7. What are the four main forms of chemical signalling?
Answer: The four main forms of chemical signalling are paracrine, endocrine, autocrine, and juxtacrine. You can learn more about chemical signalling in Section 17.7.
Apply the concepts
8. Explain the concept of the dynamic equilibrium.
Answer: The dynamic equilibrium is where there can be movement of ions in either direction across the membrane, but no net change in the membrane potential. Section 17.4 explains more about this topic.
9. How does the structure of ion channels affect their permeability to different ions?
Answer: To answer this question, think about the factors that can be determinants, such as size and charge of the ions. Section 17.3 will help you to understand this topic.
10. Describe the process of transmission at chemical synapses.
Answer: You can find a description of the process of transmission at chemical synapses in Section 17.6 of the chapter.
11. What determines the maximum rate of action potential discharge?
Answer: The maximum rate of action potential discharge is determined by two stages: absolute and relative. It is dependent on the inactivation of the Na+ channels. You can read about this in more detail in Section 17.4.
12. How are metabotropic receptors linked to intracellular mechanisms?
Answer: Metabotropic receptors, also known as GPCRs, can act through G-protein-gated ion channels and G-protein-activated enzymes. Section 17.6 explains more about this topic.
Beyond the concepts
13. Compare and contrast metabotropic and ionotropic mechanisms of cell signalling.
Answer: Review Section 17.6 on signalling and compare the two mechanisms. What are the similarities? For example, think about release and binding of neurotransmitters. What are the differences? For example, think about the nature of the post-synaptic receptor and the intracellular mechanisms.
14. Describe the properties of axons that determine the conduction velocity of the action potential.
Answer: Reread Sections 17.4 and 17.5 and reflect on the process of generation of the action potential and the physical properties that affect conduction, such as axonal diameter, and the presence or absence of myelin, and explain why these affect velocity.
15. Describe the structure of the voltage-gated sodium channel and explain its role in the conduction of the nerve impulse.
Answer: Review Section 17.4, explain the concept of voltage-gating, and describe the structure of the voltage-gated Na+ channel. Remember to consider the different activation states of the channel.
16. What is the resting membrane potential? Explain the neuronal properties that underpin the establishment and maintenance of the resting potential and the role of the Na+K+ATPase pump.
Answer: Review Section 17.3 and explain the physical properties of the membrane and its associated ion channels; consider in particular the role of the K+ channels. Describe the function of the Na+K+ATPase pump and explain its role in maintaining the resting potential.
17. Compare and contrast the different mechanisms of cellular signalling.
Answer: Review Section 17.7 and research examples of the different forms of cell signalling.