131) When a neurotransmitter molecule binds briefly with a receptor site, changes occur in the receiving neuron’s membrane. If there is a voltage shift in a negative direction then the effect is: A) inhibitory, and so the probability that the receiving neuron will fire decreases. B) likely to lead to the development of multiple sclerosis. C) excitatory, and so the probability that the receiving neuron will fire increases. D) likely to lead to the development of Parkinson’s disease. 132) The image of a key fitting into a lock is useful in understanding how: A) two nerve cells physically touch each other at each end. B) neurotransmitters bind to receptor molecules. C) ion channels open and close. D) synaptic vesicles are opened by an action potential. 133) The “decision” as to whether a neuron will produce a response or not depends upon the: A) inhibitory inputs it receives. B) excitatory inputs it receives. C) excitatory and inhibitory inputs it receives. D) strength of the inputs it receives. 134) What any given neuron does at any given moment depends on the net effect of all the messages being received from other neurons. Whether a particular neuron fires or not does NOT depend on: A) what type of other neurons are firing. B) where the other neurons are located. C) how strongly the other neurons are firing. D) the rate at which the other neurons are firing. 135) Research on neurotransmitters has shown that: A) harmful effects can occur at too high or too low levels. B) there are 5 known and 10 suspected neurotransmitters. C) acetylcholine functions as a major inhibitory neurotransmitter. D) they exist only in the brain. 136) Three types of chemical messengers are: A) neurotransmitters, endorphins, and hormones. B) excitatory neurotransmitters, inhibitory neurotransmitters, and endorphins. C) sodium, potassium, and neurotransmitters. D) excitatory neurotransmitters, inhibitory neurotransmitters, and hormones. 137) The nature of the effect of a neurotransmitter depends on all of the following EXCEPT the: A) type of receptor the neurotransmitter binds to. B) charge of the neurotransmitter. C) location of the neurotransmitter. D) level of the neurotransmitter. 138) How many substances are known or suspected to be neurotransmitters? A) 8 to 10 B) thousands C) 15 to 20 D) hundreds 139) Our textbook points out that ________ are known or suspected to be neurotransmitters. A) hundreds of substances B) thousands of substances C) about 50 substances D) about 25 substances 140) Which of the following neurotransmitters affects neurons involved in sleep, appetite, sensory perception, temperature regulation, pain suppression, and mood? A) serotonin B) norepinephrine C) dopamine D) acetylcholine