Psych chapter 2

Other methods: (a) Cell body or tract (myelin) staining, (b) Microinjections, and (c) Intrabrain electrical recordings

(a) Colors/stains selected neurons or nerve fibers. (b) Injects chemicals into specific areas of the brain. (c) Records activity of one or a group of neurons inside the brain. Increases overall information of structure and function through direct observation and measurement. Intrabrain wire probes allow scientists to "see" individual neuron activity.

PET (positron emission tomography) scan

A radioactive form of glucose is injected into the bloodstream; a scanner records the amount of glucose used in particularly active areas of the brain and produces a computer-constructed picture of the brain. Originally designed to detect abnormalities, now used to identify brain areas active during ordinary activities (such as reading or singing).

Motor control

At the very back of the frontal lobes lies the motor cortex, which sends messages to the various muscles that instigate voluntary movement. When you want to call your friend on your cell phone, the motor control area of your frontal lobes guides your fingers to press the desired sequence of numbers.

Norepinephrine (NE) [or noradrenaline (NA)] Cocaine, methamphetamine, amphetamine, ecstasy (MDMA), Adderall (treatment for ADHD)

Attention, arousal learning, memory, dreaming, emotion, stress; low levels of NE associated with depression; high levels of NE linked with agitated, manic states

Endocrine continued

Before going on, it's important to know that in spite of the previously mentioned differences between the nervous system and the endocrine system, they're actually close relatives that are intricately interconnected. In times of crisis, the hypothalamus sends messages through two pathways—the neural system and the endocrine system (primarily the pituitary gland)

Spinal Cord

Beginning at the base of our brains and continuing down our backs, the spinal cord carries vital information from the rest of the body into and out of the brain.

hypothalamus

Beneath the thalamus lies the kidney bean-sized hypothalamus. (Hypo- means "under.") This organ has been called the "master control center" for emotions and for many basic motives such as hunger, thirst, sex, and aggression (Falkner & Lin, 2014; Maggi et al., 2015; Presti, 2016). See the Psychology and You feature. The hypothalamus also controls the body's internal environment, including temperature, which it accomplishes by regulating the endocrine system. Another well-known function of the hypothalamus is its role as part of the so-called "pleasure center," a set of brain structures whose stimulation leads to highly enjoyable feelings (Naneix et al., 2016; Olds & Milner, 1954; Stopper & Floresco, 2015). Even though the hypothalamus and other structures and neurotransmitters are instrumental in emotions, the frontal lobes of the cerebral cortex also play an important role.

Speech production

Broca's area, located in the left frontal lobe near the bottom of the motor control area, plays a crucial role in speech production. In 1865, French physician Paul Broca discovered that damage to this area causes difficulty in speech, but not language comprehension. This type of impaired language ability is known as Broca's aphasia.

reflexes, or reflex arcs

But the spinal cord doesn't simply relay messages. It can also initiate certain automatic behaviors on its own. We call these involuntary, automatic behaviors because the response to the incoming stimuli is automatically sent to the spinal cord, and then "reflected" back to the appropriate muscles. This allows an immediate action response without the delay of routing signals first to the brain. How the Spinal Reflex Operates In a simple reflex arc, a sensory receptor responds to stimulation and initiates a neural impulse that travels to the spinal cord. This signal then travels back to the appropriate muscle, which then reflexively contracts. Note that the reflex response is automatic and immediate because the signal only travels as far as the spinal cord before action is initiated, not all the way to the brain. The brain is later "notified" when the spinal cord sends along the message, which, in this case of the hot pan, leads to a perception of pain. What might be the evolutionary advantages of the reflex arc? We're all born with numerous reflexes, many of which fade over time (Figure 2.7). But even as adults, we still blink in response to a puff of air in our eyes, gag when something touches the back of the throat, and urinate and defecate in response to pressure in the bladder and rectum. If you have a newborn or young infant in your home, you can easily (and safely) test for these simple reflexes. (Most infant reflexes disappear within the first year of life. If they reappear in later life, it generally indicates damage to the central nervous system.)

Lobes of the brain This is a view of the brain's left hemisphere showing its four lobes—frontal, parietal, temporal, and occipital. The right hemisphere has the same four lobes. Divisions between the lobes are marked by visibly prominent folds. Keep in mind that Broca's and Wernicke's areas occur only in the left hemisphere.

By far the largest of the cortical lobes, the two frontal lobes are located at the top front portion of the two brain hemispheres—right behind the forehead. The frontal lobes receive and coordinate messages from all other lobes of the cortex, while also being responsible for at least three additional functions

CT (computed tomography) scan This CT scan used X-rays to locate a brain tumor, which is the deep purple mass at the top left.

Computer-created cross-sectional X-rays of the brain or other parts of the body produce 3-D images. Least expensive type of imaging and widely used in research. Reveals the effects of strokes, injuries, tumors, and other brain disorders.

Epinephrine (or adrenaline) Amphetamines, ecstasy (MDMA), cocaine

Emotional arousal, memory storage, metabolism of glucose necessary for energy release

Split-brain research

Experiments on split-brain patients often present visual information to only the patient's left or right hemisphere, which leads to some intriguing results.

How poisons and drugs affect neural transmission

Foreign chemicals, like poisons and drugs, can mimic or block ongoing actions of neurotransmitters, thus interfering with normal functions.

pituitary gland

Hanging down from the hypothalamus, the pituitary gland is usually considered the master endocrine gland because it releases hormones that activate the other endocrine glands. The hypothalamus influences the pituitary through direct neural connections and through release of its own hormones into the blood supply of the pituitary. The hypothalamus also directly influences some important aspects of behavior, such as eating and drinking patterns.

Biological Tools for Research

How do we know how the brain and nervous system work? Beginning in early times, scientists have dissected the brains and other body parts of human and nonhuman animals. They've also used lesioning techniques (systematically destroying bodlily tissue to study the effects on behavior and mental processes). By the mid-1800s, this research had produced a basic map of the nervous system, including some areas of the brain. Early researchers also relied on clinical observations and case studies of living people who had experienced injuries, diseases, and disorders that affected brain functioning. Modern researchers still use such methods, but they also employ other techniques to examine biological processes that underlie our behavior (Table 2.2). For example, recent advances in brain science have led to various types of brain-imaging scans, which can be used in both clinical and laboratory settings. Most of these methods are relatively noninvasive—that is, their use does not involve breaking the skin or entering the body

action potential)

If a resting neuron receives a combined signal (from the senses or other neurons) that exceeds the minimum threshold, it will be activated and "fire," thus transmitting an electrical impulse

GABA (gamma-aminobutyric acid) Alcohol, GHB, rohypnol, valium (treatment for anxiety)

Learning, anxiety regulaton; key role in neural inhibition in the central nervous system; tranquilizing drugs, like Valium, increase GABA's inhibitory effects and thereby decrease anxiety

Glutamate Alcohol, phencyclidine, PCP, ketamine (an anesthetic)

Learning, movement, memory; key role in neural excitation in the central nervous system; factor in migraines, anxiety, depression

Endorphins Heroin, morphine and oxycodone (treatments for pain)

Mood, pain, memory, learning, blood pressure, appetite, sexual activity

Serotonin Ecstasy (MDMA), LSD, cocaine, SSRIs, like Prozac (treatment for depression)

Mood, sleep, appetite, sensory perception, arousal, temperature regulation, pain suppression, impulsivity; low levels of serotonin associated with depression

Higher functions

Most complex, higher functions, such as thinking, personality, and memory, are controlled primarily by the frontal lobes. Damage to the frontal lobe also affects motivation, drives, creativity, self-awareness, initiative, and reasoning. Abnormalities in the frontal lobes are often observed in patients with schizophrenia (Chapter 12). For example, patients with schizophrenia often show overall loss of gray matter, as well as increases in cerebrospinal fluid in the frontal lobes

Dopamine (DA) Cocaine, methamphetamine, LSD, GHB, PCP, marijuana, Ecstasy (MDMA), L-Dopa (treatment for Parkinson's disease), chlorpromazine (treatment for schizophrenia)

Movement, attention, memory, learning, emotion; excess DA associated with schizophrenia; too little DA linked with Parkinson's disease; key role in addiction and the reward system

Acetylcholine (ACh) Nicotine, amphetamines, LSD, PCP, marijuana

Muscle action, learning, attention, memory, REM (rapid-eye-movement) sleep, emotion; decreased ACh plays a suspected role in Alzheimer's disease

fMRI (functional magnetic resonance imaging) The yellow highlighted areas in this fMRI are "lit up," which tells us that oxygen from the blood is being heavily used in this region.

Newer, faster version of MRI that detects blood flow by picking up magnetic signals from blood, which has given up its oxygen to activate brain cells. Measures blood flow, which indicates areas of the brain that are active and inactive during ordinary behaviors or responses (like reading or talking); also shows changes associated with various disorders.

Association Areas

One of the most popular myths in psychology is that we use only 10% of our brains. This myth might have begun with early research which showed that approximately three-fourths of the cortex is "quiet" (with no precise, specific function responsive to electrical brain stimulation). These areas are not dormant, however. They are clearly engaged in interpreting, integrating, and acting on information processed by other parts of the brain. They are called association areas because they associate, or connect, various areas and functions of the brain. The association areas in the frontal lobes, for example, help in decision making and planning. Similarly, the association area right in front of the motor cortex aids in the planning of voluntary movement.

endorphins

Perhaps the best-known neurotransmitters are the endogenous opioid peptides, commonly known as endorphins (a contraction of endogenous [self-produced] and morphine). These chemicals mimic the effects of opium-based drugs such as morphine: They elevate mood and reduce pain In fact, drinking alcohol causes endorphins to be released in parts of the brain that are responsible for feelings of reward and pleasure ex. The researchers attributed these findings to the release of endorphins. They also hypothesized that singing and dancing may have evolved over time because they encourage social bonding with strangers! Endorphins also affect memory, learning, blood pressure, appetite, and sexual activity. For example, rats injected with an endorphin-like-chemical eat considerably more M&Ms than they would under normal conditions, even consuming as much as 17 grams (more than 5% of their body weight; DiFeliceantonio et al., 2012). Although this may not seem like a lot of chocolate to you, it is the equivalent of a normal-sized adult eating 7.5 pounds of M&Ms in a single session!

Neuroplasticity

Rather than being a fixed, solid organ, the brain is capable of changing its structure and function as a result of usage and experience. This "rewiring," officially known as neuroplasticity, is what makes our brains so wonderfully adaptive. For example, when infants suffer damage to the speech area of their left hemisphere, the right hemisphere can reorganize and pick up some language abilities. Remarkably, this rewiring has even helped "remodel" the adult brain following strokes. Psychologist Edward Taub and his colleagues (2004, 2014) have had notable success working with stroke patients

STeps of neuron

Step 1 Neurons are normally at rest and ready to be activated, which explains why this resting stage is called the "resting potential." Step 2 If a resting neuron receives a combined signal (from the senses or other neurons) that exceeds the minimum threshold, it will be activated and "fire," thus transmitting an electrical impulse (called an action potential). (Note that in Process Diagram 2.1, we're only demonstrating how an action potential "fires"—also known as "excitation." However, this resting neuron also receives simultaneous messages telling it NOT to fire—a process called "inhibition." Given these contradictory messages, the neuron does something simple—it goes with the majority! If it receives more excitatory messages than inhibitory, it fires—and vice versa.) Step 3 The beginning action potential then spreads and travels down the axon. As the action potential moves toward the terminal buttons, the areas on the axon left behind return to their resting state. Note that this firing of an action potential is similar to a light switch, where once you apply the minimum amount of pressure needed to flip the switch, the light comes on. There is no "partial firing" of a neuron. It's either on or off. This neural reaction of either firing with a full-strength response or not at all is known as the all-or-nothing principle. But if this is true, how do we detect the intensity of a stimulus, such as the difference between a rock and a butterfly landing on our hand? A strong stimulus (like the rock) causes more neurons to fire and to fire more often than does a butterfly. PG.37. the neurotransmitters then unlock tiny channels in the receiving neuron, and send either excitatory ("fire") or inhibitory ("don't fire") messages. (The receiving neuron is called a post-synaptic neuron.)

autonomic nervous system (ANS)

The ANS is responsible for involuntary tasks, such as heart rate, digestion, pupil dilation, and breathing. Like an automatic pilot, the ANS can sometimes be consciously overridden. But as its name implies, the autonomic system normally operates on its own (autonomously). The ANS is further divided into two branches, the sympathetic and parasympathetic, which tend to work in opposition to each other to regulate the functioning of such target organs as the heart, the intestines, and the lungs. Like two children on a teeter-totter, one will be up while the other is down, but they essentially balance each other out. Figure 2.8 illustrates a familiar example of the interaction between the sympathetic and parasympathetic nervous systems. The ANS is responsible for a variety of independent (autonomous) activities, such as salivation and digestion. It exercises this control through its two divisions—the sympathetic and parasympathetic branche

axon

The axon then carries information away from the cell body to the terminal buttons.

Information crossover Our brains' right hemisphere controls the left side of our bodies, whereas the left hemisphere controls the right side.

The full cerebral cortex and the two cerebral hemispheres beneath it closely resemble an oversized walnut. The division, or fissure, down the center marks the separation between the left and right hemispheres of the brain, which make up about 80% of the brain's weight. The hemispheres are mostly filled with axon connections between the cortex and the other brain structures. Each hemisphere controls the opposite side of the body

cerebral cortex

The gray, wrinkled cerebral cortex, the surface layer of the cerebral hemispheres, is responsible for most complex behaviors and higher mental processes. It plays such a vital role that many consider it the essence of life itself. Although the cerebral cortex is only about one-eighth of an inch thick, it's made up of approximately 30 billion neurons and nine times as many glial cells. Its numerous wrinkles, called convolutions, significantly increase its surface area. Damage to the cerebral cortex is linked to numerous problems, including suicide, substance abuse, and dementia (Flores et al., 2016; Presti, 2016; Sharma et al., 2015). Evidence suggests that such trauma is particularly common in athletes who experience head injuries in sports like football (see photo), ice hockey, boxing, and soccer

cell body

The information then flows into the cell body, or soma (Greek for "body"). If the cell body receives enough information/stimulation from its dendrites, it will pass the message on

central nervous system (CNS).

The main branch includes the brain and a bundle of nerves that form the spinal cord. Because this system is located in the center of the body (within the skull and spine), it is called the central nervous system (CNS). The CNS is primarily responsible for processing and organizing information. But thanks to our CNS, we can process information and adapt to our environment in ways that no other animal can. Unfortunately, our CNS is also incredibly fragile. Unlike neurons in the PNS that can regenerate and require less protection, neurons in the CNS can suffer serious and permanent damage. As we'll see later in this chapter, repeated head trauma, particularly when associated with loss of consciousness, can lead to debilitating and potentially fatal illnesses

corpus callosum

The primary connection between the two cerebral hemispheres is a thick, ribbon-like band of neural fibers under the cortex called the corpus callosum (Figure 2.18). In some rare cases of severe epilepsy, when other forms of treatment have failed, surgeons cut the corpus callosum to stop the spread of epileptic seizures from one hemisphere to the other. Because this operation cuts the only direct communication link between the two hemispheres, it reveals what each half of the brain can do in isolation from the other. The resulting research has profoundly improved our understanding of how the two halves of the brain function. Although most split-brain surgery patients generally show very few outward changes in their behavior, other than fewer epileptic seizures, the surgery does create a few unusual responses. For example, one split-brain patient reported that when he dressed himself, he sometimes pulled his pants down with his left hand and up with his right (Gazzaniga, 2009). The subtle changes in split-brain patients normally appear only with specialized testing. See Figure 2.19 for an illustration and description of this type of specialized test. Keep in mind that in actual split-brain surgery on live patients, only some fibers within the corpus callosum are cut (not the lower brain structures), and this surgery is performed only in rare cases of uncontrollable epilepsy.

peripheral nervous system (PNS)

The second major branch of the nervous system includes all the nerves outside the brain and spinal cord. This peripheral nervous system (PNS) carries messages (action potentials) to and from the CNS to the periphery of the body.

all-or-nothing principle

There is no "partial firing" of a neuron. It's either on or off. This neural reaction of either firing with a full-strength response or not at all is known as the

MRI (magnetic resonance imaging) Note the fissures and internal structures of the brain. The throat, nasal airways, and fluid surrounding the brain are dark.

Using a powerful magnet and radio waves linked to a computer, a scanner creates detailed, cross-sectional images.. Produces high-resolution 3-D pictures of the brain useful for identifying abnormalities and mapping brain structures and function.

Electrical recordings Electrical activity throughout the brain sweeps in regular waves across its surface, and the electroencephalogram (EEG) is a read out of this activity.

Using electrodes attached to the skin or scalp, brain activity is detected and recorded on an EEG. Reveals areas of the brain most active during particular tasks or mental states such as reading or sleeping; also traces abnormal brain waves caused by brain malfunctions, such as epilepsy or tumors.

lateralization

We mentioned earlier that the brain's left and right cerebral hemispheres control opposite sides of the body. Each hemisphere also has separate areas of specialization. This is another example of localization of function, technically referred to as lateralization. Early researchers believed the right hemisphere was subordinate or nondominant to the left, with few special functions or abilities. In the 1960s, landmark split-brain surgeries began to change this view.

Stem cell therapy

Will stem cell transplants allow people paralyzed from spinal cord injuries to walk again? Scientists have had some success transplanting stem cells into spinal cord-injured nonhuman animals (Gao et al., 2016; Raynald et al., 2016; Sandner et al., 2015). When the damaged spinal cord was viewed several weeks later, the implanted cells had survived and spread throughout the injured area. More important, the transplant animals also showed some improvement in previously paralyzed parts of their bodies. Medical researchers are also testing the safety of embryonic stem cell therapy for human paralysis patients, and future trials may determine whether these cells will repair damaged spinal cords and/or improve sensation and movement in paralyzed areas (

hippocampus

a key part of the limbic system, is involved in forming and retrieving our memories

amyotrophic lateral sclerosis (ALS)

a neurological disease caused by degeneration of motor neurons (later commonly called "Lou Gehrig's disease"). However, scientists now think that Lou Gehrig may not have had ALS. Instead, he may have developed symptoms that were similar to those of ALS because he was so often hit in the head with baseballs

reuptake

a neurotransmitter's reabsorption by the sending neuron most of the "leftovers" are reabsorbed by the axon and stored until the next neural impulse

the adrenal glands then release cortisol

a stress hormone that boosts energy and blood sugar levels, epinephrine (commonly called adrenaline), and norepinephrine (or nonadrenaline). (Remember that these same chemicals also can serve as neurotransmitters.)

myelin sheath

a white, fatty coating around the axons of some neurons, is not considered one of the three key features of a neuron, but it plays the essential roles of insulating and speeding neural impulses -white, fatty coating around the axons of some neurons, is not considered one of the three key features of a neuron the essential roles of insulating and speeding neural impulses -The layer of fatty insulation wrapped around the axon of some neurons that increases the rate at which neural impulses travel along the axon., a white, fatty coating around the axons of some neurons, is not considered one of the three key features of a neuron, but it plays the essential roles of insulating and speeding neural impulses. As you'll discover in the next section, our human body is essentially an information-processing system dependent upon electrical impulses and chemical messengers. Just as the wires in data cables are insulated from one another by plastic, the myelin sheath provides insulation and separation for the numerous axons that travel throughout our bodies. And just as the data cable wires are bundled together into larger cables, our myelin-coated axons are bundled together into "cables" called <i>nerves</i>. The importance of myelin sheaths becomes readily apparent in certain diseases, such as <i>multiple sclerosis, in which myelin progressively deteriorates and the person gradually loses muscular coordination. Thankfully, the disease often goes into remission, but it can be fatal if it strikes the neurons that control basic life-support processes, such as breathing or heartbeat. Myelin is also very important in the first few weeks and months of life. Research shows that social isolation during these critical periods (as occurs for babies who are neglected in some orphanages, see photo) prevents cells from producing the right amount of myelin. Sadly, this loss of normal levels of myelin leads to long-term problems in cognitive functioning

limbic system

an interconnected group of forebrain structures, known as the limbic system, is located roughly along the border between the cerebral cortex and the lower-level brain structures (Figure 2.13). Although opinion is divided upon whether other structures, such as the hypothalamus and thalamus, should be included as part of the limbic sytem, its two most important structures are the hippocampus and amygdala. The limbic system is generally responsible for emotions, drives, and memory

occipital lobes

are responsible for, among other things, vision and visual perception. Damage to the occipital lobes can produce blindness, even if the eyes and their neural connection to the brain are perfectly healthy.

sympathetic nervous system

arouses and mobilizes bodily resources to respond to the stressor. This emergency response is often called the "fight or flight" response. (Note this response has recently been expanded and relabeled as the "fight, flight, or freeze" response, which will be fully discussed in Chapter 3.) If you noticed a dangerous snake coiled and ready to strike, your sympathetic nervous system would increase your heart rate, respiration, and blood pressure; stop your digestive and eliminative processes; and release hormones, such as cortisol, into the bloodstream. The net result of sympathetic activation is to get more oxygenated blood and energy to the skeletal muscles, thus allowing you to cope with the stress—to either fight or flee.

glial cells

cells in the nervous system that support, nourish, and protect neurons

neurotransmitters

chemical messengers that cross the synaptic gaps between neurons

somatic nervous system (SNS)

consists of all the nerves that connect to sensory receptors and skeletal muscles. The name comes from the term soma, which means "body," and the somatic nervous system plays a key role in communication throughout the entire body. In a kind of two-way street, the somatic nervous system (also called the skeletal nervous system) first carries sensory information to the brain and spinal cord (CNS) and then carries messages from the CNS to skeletal muscles.

three basic features of neurons

dendrites, the cell body, and an axon

antagonist drugs

drugs that block or change the effects of an addictive drug

agonist drugs

enhance a particular neurotransmitter

medulla

essentially an extension of the spinal cord, with many neural fibers passing through it carrying information to and from the brain. Because the medulla controls many essential automatic bodily functions, such as respiration and heart rate, serious damage to this area is most often fatal

cerebellum

he cauliflower-shaped cerebellum (Latin for "little brain") is, evolutionarily, a very old structure. It coordinates fine muscle movement and balance (Figure 2.11). Researchers using functional magnetic resonance imaging (fMRI) have shown that parts of the cerebellum also are important for memory, sensation, perception, cognition, language, learning, and even "multitasking" (Garrett, 2015; Ng et al., 2016; Presti, 2016). Interestingly, researchers have found that people who play videogames for 30 minutes a day for 2 months show increases in gray matter in the cerebellum, right hippocampus, and the right prefrontal cortex (see photo) (Kühn et al., 2014). Gray matter is critical for higher cognitive functioning, and we'll study more about these three brain areas in the next section. For now it's enough to know that these brain sections are largely responsible for spatial navigation, strategic planning, and fine motor skills in the hands. In short, research suggests that playing video games may actually be good for your brain! Walk the line Asking drivers to perform tasks like walking the white line is a somewhat common part of a field sobriety test for possible intoxication. Why? The cerebellum, responsible for smooth and precise movements, is one of the first areas of the brain to be affected by alcohol.

midbrain

helps us orient our eye and body movements to visual and auditory stimuli, and it works with the pons to help control sleep and level of arousal. It also contains a small structure, the substantia nigra, that secretes the neurotransmitter dopamine. Parkinson's disease, an age-related degenerative condition, is related to the deterioration of neurons in the substantia nigra and the subsequent loss of dopamine.

brainstem

important to note that the reticular formation passes through the diffuse, stem-shaped area of the midbrain, known as the brainstem, which also includes the pons and medulla in the hindbrain (see again Figure 2.10). At its lower end, the brainstem connects with the spinal cord, and at its upper end it attaches to the thalamus.

pons

involved in respiration, movement, sleeping, waking, and dreaming (among other things). It also contains axons that cross from one side of the brain to the other (pons is Latin for "bridge").

forebrain

largest and most prominent part of the human brain. It includes the cerebral cortex, limbic system, thalamus and hypothalamus (Figure 2.12). The last three are located near the top of the brainstem. The cerebral cortex (discussed separately, in the next section) is wrapped above and around them. (Cerebrum is Latin for "brain," and cortex is Latin for "covering" or "bark.")

Dendrites

leafless branches of a tree. In fact, the word dendrite means "little tree" in Greek. Each neuron may have hundreds or thousands of dendrites, which act like antennas to receive electrochemical information from other nearby neurons.

thalamus

located at the top of the brainstem. It integrates input from the senses, and it may also function in learning and memory (McCormick et al., 2015; Schroll et al., 2015; Zhou et al., 2016). The thalamus receives input from nearly all sensory systems, except smell, and then directs the information to the appropriate cortical areas. The thalamus also transmits some higher brain information to the cerebellum and medulla. Think of the thalamus as the switchboard in an air traffic control center that receives information from all aircraft and directs them to appropriate landing or takeoff areas. Because the thalamus is the brain's major sensory relay center to the cerebral cortex, damage or abnormalities in the thalamus might cause the cortex to misinterpret or not receive vital sensory information. As you'll discover in Chapter 12, brain-imaging research links thalamus abnormalities to schizophrenia, a serious psychological disorder characterized by problems with sensory filtering and perception (Buchy et al., 2015; Kim et al., 2015; Ramsay & MacDonald, 2015).

second system

made up of a network of glands, called the endocrine system Why do we need two communication systems? Neurotransmitters are like emails that we only send to certain people—they only deliver messages to certain receptors. Hormones, in contrast, are like a global e-mail message that we send to everyone in our address book. Our hormone-releasing endocrine system has several important functions. It helps regulate long-term bodily processes, such as growth and sexual characteristics, while also changing or maintaining short-term processes, such as digestion and elimination.

neurons

microscopic nerve cells

stem cells

new neurons in the brain. The source of these newly created cells, rare, immature cells that can grow and develop into any type of cell. Their fate depends on the chemical signals they receive. Experiments and clinical trials on both human and nonhuman animals have used stem cells for bone marrow transplants, and to repopulate or replace cells devastated by injury or disease This research offers hope to patients suffering from strokes, Alzheimer's, Parkinson's, epilepsy, stress, and depression (Alenina & Klempin, 2015; Belkind-Gerson et al., 2016; Kim et al., 2016a). In addition, stem cell injections into the eyes of patients with untreatable eye diseases and severe visual problems have led to dramatic improvements in vision

Wernicke's area

part of the left temporal lobe called Wernicke's area aids in language comprehension. About a decade after Broca's discovery, German neurologist Carl Wernicke noted that patients with damage in this area could not understand what they read or heard, but they could speak quickly and easily. However, their speech was often unintelligible because it contained made-up words, sound substitutions, and word substitutions. This syndrome is now referred to as Wernicke's aphasia.

oxytocin

pituitary gland also releases another important hormone, oxytocin, which plays a very interesting role in love, attachment, and social bonding. Oxytocin enables contractions during birth, nursing, and sexual orgasm, and high oxytocin levels are also found during hugging, cuddling, and emotional bonding with romantic partners. One study even discovered that men who receive a spray of the hormone oxytocin rate their female partners as more attractive than unfamiliar women—thus suggesting oxytocin may increase faithfulness (Scheele et al., 2013). Perhaps even more interesting is the research showing that dogs who stare at their owners show elevated levels of oxytocin (see photo), and after receiving these dog gazes, the human's level of oxytocin also increases

parietal lobes

receive and interpret bodily sensations including pressure, pain, touch, temperature, and location of body parts. A band of tissue on the front of the parietal lobes, called the somatosensory cortex, receives information about touch in different body areas. Areas of the body with more somatosensory and motor cortex devoted to them (such as the hands and face) are most sensitive to touch and have the most precise motor control

sensory neurons

respond to physical stimuli by sending neural messages to our brains and nervous systems.

motor neurons

respond to sensory neurons by transmitting signals that activate our muscles and glands. For example, light and sound waves from the text messages that we receive on our cell phones are picked up by our sensory neurons, whereas our motor neurons allow our fingers to almost instantaneously type reply messages.

parasympathetic nervous system

responsible for calming our bodies and conserving energy. It returns our normal bodily functions by slowing our heart rate, lowering our blood pressure, and increasing our digestive and eliminative processes. The sympathetic nervous system provides an adaptive, evolutionary advantage. At the beginning of human evolution, when we faced a dangerous bear or an aggressive human attacker, there were only three reasonable responses—fight, flight, or freeze. The automatic mobilization of bodily resources can still be critical, even in modern times. However, less life-threatening events, such as traffic jams, also activate our sympathetic nervous system. As the next chapter discusses, ongoing sympathetic system response to such chronic, daily stress can become detrimental to our health. For a look at how the autonomic nervous system affects our sexual lives

temporal lobes

responsible for hearing, language comprehension, memory, and some emotional control. The auditory cortex, which processes sound, is located at the top front of each temporal lobe. This area is responsible for receiving incoming sensory information and sending it on to the parietal lobes, where it is combined with other sensory information.

reticular formation (RF)

running through the core of the hindbrain and midbrain is the reticular formation (RF). This diffuse, finger-shaped network of neurons helps screen incoming sensory information and alert the higher brain centers to important events. Without our reticular formation, we would not be alert or perhaps even conscious.

hormones

second type of communication system that uses hormones as its messengers

note that the PNS is subdivided into the

somatic nervous system and the autonomic nervous system.

The pituitary sends hormonal messages to

the adrenal glands (located right above the kidneys)

Neurogenesis

the formation of new neurons

synapse

the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron

amygdala

the limbic system's major focus of interest is the amygdala, which is linked to the production and regulation of emotions-especially aggression and fear

it's important to note that neuroplasticity and neurogenesis are NOT the same as neuroregeneration,

which refers to the regrowth or repair of neurons, glia, or synapses. This process is fairly common within the peripheral nervous system (PNS). You've undoubtedly watched a cut heal on your skin and/or known of someone who slowly regained his or her feeling and function after a serious motor vehicle accident or severe fall. . In contrast, regeneration after damage within the central nervous system (CNS) is far less common.

hindbrain

yoou're asleep and in the middle of a frightening nightmare. Your heart is racing, your breathing is rapid, and you're attempting to run away but find you can't move! Suddenly, your nightmare is shattered by a buzzing alarm clock. All your automatic behaviors and survival responses in this scenario are controlled or influenced by parts of the hindbrain. The hindbrain includes the medulla, pons, and cerebellum.