Study Guide for Chapter 5

1.       What type of site is a “gap junction?” How common are gap junctions in mammals? What benefits do electrical synapses confer? What limitations?

2.       What are the major differences between synaptic vesicles and secretory granules?

3.       What is an active zone? What takes place at the postsynaptic density?

4.        What are the different types of CNS synapses? What is the most common PNS synapse?

5.       What takes place at the neuromuscular junction? Of what practical and clinical significance are neuromuscular junctions?

6.       Are chemical or electrical synapses more common in the adult human brain?

7.       What are the three chemical categories into which most known neurotransmitters fall? What is the obvious difference between the peptides and the amines & amino acids?

8.       What is a transporter?

9.       What series of events triggers the release of neurotransmitters from the presynaptic cell?

10.      Do dendrites have electrically-(voltage-)gated channels or chemically-gated ones? What about axons?

11.      What is an EPSP? An IPSP? How are these integrated? (Know the two types of summation.) How do the properties of dendrites contribute to integration? (a brief overview is all that is necessary here.)

12.      It is very important that you understand the general concepts of second messenger systems. For example:  If the neurotransmitter norepinephrine (NE) binds to its receptor, the first messenger is the norepinephrine. But it doesn’t stop there—the binding of NE triggers a cascade of events. After NE binds, a G-protein is activated that causes adenyl cyclase (an effector protein) to catalyze a chemical reaction wherein ATP (which literally is a straight molecule) changes to cAMP (cyclic AMP, which is a ring-shaped molecule). When ATP is converted into cAMP, an enzyme called protein kinase causes phosphate groups to move from ATP to specific sites on certain proteins. These proteins cause potassium (K⁺) channels to close.  Or it may cause sodium (Na⁺) channels to remain open. The net result is that excitatory synapses are facilitated. This will serve to amplify a weak or distant excitatory signal. Keep in mind, however, that there are other second messengers as well as cAMP, and not all will produce an excitatory effect. This is simply one example of a second messenger system.  This is also discussed in Chapter 6, and in greater detail.

13.        How does synaptic modulation differ from synaptic activation?

14.        Using the information in Box 5.5 on page 121, how would you surmise Botox (botulinum toxin) works?

15.        How are neurotransmitters removed from the synapse once they have done their job?

16.         What is shunting inhibition?

As always, study the key terms and review questions on pages 131 and 132 in your text.