We can think of the neuron as a miniature decision-making device because the cell body of the neuron has to decide whether or not to generate an electrical impulse based on the incoming information from other neurons. If the excitatory input outweighs the inhibitory input by a sufficient amount, the cell body will decide to generate an impulse.
Neural impulses are faster in neurons with myelinated axons than unmyelinated axons because the electrical impulse leaps from gap to gap in the myelin sheath rather than traveling continuously down the axon.
Drugs that block the reuptake of neurotransmitters are considered agonists because they keep the neurotransmitters active in the synaptic gap (they keep carrying their messages over and over again to the receiving neuron), which increases the activity of the neurotransmitters.
L-dopa leads to side effects that resemble the thought disorder symptoms of schizophrenia because L-dopa increases the activity of dopamine in the brain and the schizophrenic symptoms are the result of too much dopamine activity. Similarly, traditional antipsychotic drugs lead to side effects resembling Parkinson’s disease symptoms because these drugs globally reduce the activity of dopamine in the brain. Thus, dopamine activity in the movement system involving the basal ganglia is reduced, leading to movement problems similar to those of Parkinson’s disease.
Concept Check 2
With respect to location, sensory neurons and motor neurons are only in the PNS, and interneurons are only in the CNS. With respect to function, sensory neurons carry information to the CNS from the sensory receptors and internal organs, muscles, and glands of the body. Motor neurons carry movement commands from the CNS out to the rest of the body. Interneurons integrate the information within the CNS.
The sympathetic nervous system is referred to as the “fight-or-flight” system because it prepares us for these actions in an emergency situation. The parasympathetic nervous system is referred to as the “rest-and-digest” system because its actions (the opposite of those in the sympathetic nervous system) allow us to rest and let functions such as digestion go back to normal.
Both hormones and neurotransmitters are chemical messengers, but the hormones are much slower because they carry their message through the bloodstream to their distant targets. Neurotransmitters are released within the nervous system directly to their targets.
The pituitary gland is referred to as the “master gland” because it releases hormones that direct the other endocrine glands to release their hormones. It functions like the master of the endocrine system.
According to the James-Lange theory of emotion, we use the autonomic arousal and behavioral responses to determine the emotion. The emotional feeling occurs after and as a result of these responses. The specific emotion experienced depends upon the particular pattern of the arousal and behavioral responses. But, according to the Cannon-Bard theory, arousal patterns are too similar to be used to differentiate specific emotions. Cannon and Bard propose that arousal, behavioral response, and emotional feeling occur simultaneously and independently. Thus, contrary to the James-Lange theory, the arousal and behavioral responses and the emotional feeling happen at the same time.
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Concept Check 3
To feel a slap on the left cheek of your face, the area devoted to the cheek in the lower half of the somatosensory cortical strip in the parietal lobe in the right hemisphere would be activated. Refer to Figure 2.9 to see the exact location of the cheek in the somatosensory homunculus and thus the activation. Remember that the activation would be at this location in the right hemisphere because your left cheek was slapped.
When you shadow someone’s speech, the auditory sensory input from the person’s speech goes first to the primary auditory cortex in the temporal lobes, next to Wernicke’s area to be understood, and then to Broca’s area to produce the appropriate motor programs, which are then sent to the motor cortex, which then executes the programs to activate your speech muscles to produce the speech.
A person who suffered damage to her cerebellum would have problems in motor coordination and balance. Her movements would be jerky and uncoordinated, and she would have great difficulty maintaining her balance.
You would ask him to identify the object by the sense of touch with his left hand. He could identify it by matching the tactile input (the information gathered from touching the object) with his knowledge of what had been presented, both in the right hemisphere.
If Vertumnus were flashed briefly in a split–brain person’s left visual field, it would be processed in his right hemisphere. Hence he would use his left hand to respond because the right hemisphere’s motor cortex controls that hand. Because the right hemisphere specializes in face recognition and engages in visual, holistic processing, he would point to “face” because the overall global impression of the painting is a face. However, if the painting had been flashed briefly in his right visual field, he would use his right hand because the painting would be processed in the left hemisphere, which controls that hand. Because the left hemisphere engages in analytic processing of the elements of a stimulus, the painting would be analyzed into its component elements (fruits, flowers, and vegetables) so he would point to “fruits,” one of the main elements of the face. Gazzaniga has actually conducted some experimental trials using some of Arcimboldo’s paintings with a split-brain participant and found these predicted results.
REM sleep is sometimes referred to as paradoxical sleep because your bodily muscles are relaxed and immobilized, but many parts of your brain are active with both oxygen consumption and cerebral blood flow increasing. The brain appears to be awake, but you are behaviorally asleep.