chapter 27--campbell biology

1. too little of the neurotransmitter dopamine has been linked to what disease; 2. and too much of dopamine has been linked to what other disease?

1. parkinson's disease 2. schizophrenia

What 2 general functions does the hypothalamus control?

A complex integrating center, the hypothalamus regulates the autonomic nervous system and controls the secretion of hormones from the pituitary gland and other organs.

What common condition may reflect delayed maturation of the brain?

A delay in the maturation of the brain could explain a common brain disorder. Attention deficit hyperactivity disorder (ADHD) is conservatively estimated to affect 1 in 20 school-age children. The disorder is characterized by a lack of focus, impulsive behavior, and restlessness. In one study, scientists examined brains of over 400 youths, some with ADHD and others with no signs of the disorder. They concluded that identical regions of the brain thicken in the same order, yet the maturation of the brain is delayed by approximately 3 years in youths with ADHD.

what is an axon? how long can it be?

A different type of extension, a single long fiber called an axon, or nerve fiber, transmits signals toward a receiving cell, such as a muscle cell. Some nerve fibers, for example, the ones that reach from your spinal cord to muscle cells in your feet, can be over a meter long.

how might you design a drug to treat schizophrenia, which is caused by too much dopamine?

A drug may physically block a receptor, preventing a neurotransmitter from binding, thereby reducing its effect. For instance, some drugs used to treat schizophrenia block dopamine receptors.

What might account for the riskier, more stupid, decisions made by teenagers compared to adults/parents.

In a typical brain, the association areas of the frontal lobe are some of the last areas to mature. One association area, involved in decision making, likely continues to develop into our 20s. This might account for the riskier decisions made by teens and young adults compared to older adults.

what is the name of the membranes that surround and protect the brain and spinal cord?

Protecting the brain and spinal cord are layers of connective tissue called meninges.

Are we usually under parasympathetic control or sympathetic control

Relaxation and the fight-or-flight response are opposite extremes. Your body usually operates somewhere in between, with most of your organs receiving both sympathetic and parasympathetic signals.

What are the "functional areas" found in each lobe?

Researchers have identified a number of functional areas within each lobe: Primary sensory areas receive and process sensory information (taste, hearing, etc.), association areas integrate the information, and motor areas transmit instructions to other parts of the CNS and eventually the body. Look at labeled areas in different lobes in the figure.

define sensory input, give 3 examples

Sensory input (shown in blue) is the process of sending signals from external or internal stimuli to the CNS. Examples of stimuli include an increase or decrease in light, a soft or loud sound, or a change in the pH of the body fluids.

where are sensory neurons found and what do they do?

Sensory neurons are nerve cells often located in the PNS that convey information about a stimulus to the CNS. In the figure, a mosquito bite causes sensory neurons in the skin to send signals of pain to the spinal cord and then the brain.

how can abuse of amphetamine and cocaine lead to symptoms resembling schizophrenia

Stimulants such as amphetamines and cocaine increase the release and availability of norepinephrine and dopamine at synapses. Abuse of these drugs can therefore produce symptoms resembling schizophrenia.

what are the names of the 3 parts of the brainstem?

Structures of the brainstem, including the medulla oblongata, the pons, and the midbrain,

name two broad types of synapses

Synapses come in two varieties: electrical and chemical.

What does the autonomic system regulate? Is it voluntary or involuntary

The autonomic nervous system regulates the internal environment by controlling smooth and cardiac muscles and the glands of several body systems. This control is generally involuntary.

If a doctor declares that a patient has sustained central nervous system injuries, what structures in the CNS might be damaged?

The brain and or spinal cord

why is the brain called the master control center?

The brain functions as the master control center for the nervous system, integrating data from the sense organs and sending out commands from motor control centers.

what is found in the nerve cell body

The cell body houses the nucleus and other organelles.

define central nervous system? what two anatomical parts does it consist of? what does the CNS do?

The central nervous system (CNS) consists of the brain and spinal cord. The CNS is the control center of the nervous system, interpreting stimuli and sending out responses.

What does the cerebellum do?

The cerebellum serves as a planning center for body movements. The cerebellum receives input—for instance, visual cues about a moving tennis ball and body awareness of arm position—and uses the input to coordinate movement and balance—such as swinging a racket toward a tennis ball. Individuals who have damage to their cerebellum often have trouble with coordinated movements, such as balance or hand-eye coordination; for example, they can follow a tennis ball with their eyes but are not able to move the racket toward the ball.

What is the significance of the two hemispheres of the cerebral cortex? Does the left cerebral cortex control the left or right side of the body? Does the left cerebral cortex receive information from the left or right side of the body?

The cerebral cortex is divided into right and left hemispheres (Figure 27.11). Each half receives information from and controls the movement of the opposite side of the body. So, the left hemisphere receives information from right side of the body and controls the right side of the body.

What is the difference between the cerebrum and the cerebral cortex?

The cerebrum is the largest and most sophisticated part of our brain. The outer layer of the cerebrum, the cerebral cortex, is a thin, highly folded ("wrinkled") layer of tissue that accounts for over 80% of the total brain mass yet is thinner than the width of a pencil.

Which brain structure— the cerebellum or the cerebrum—contains sophisticated thinking centers?

The cerebrum.

what what functions does cerebrospinal fluid serve?

The fluid supplies nutrients and hormones to the CNS and carries away wastes, before draining into the veins.

Name some more specific functions functions that the hypothalamus regulate.

The functions of the hypothalamus affect body temperature, blood pressure, hunger, thirst, sex drive, and the fight-or-flight response. The hypothalamus also helps us experience emotions, such as rage and pleasure. The pleasure center of the hypothalamus is strongly affected by certain addictive drugs. Another area of the hypothalamus functions as an internal timekeeper that maintains our daily biological rhythms, such as cycles of sleepiness and hunger.

what do dendrites do

The numerous short and highly branched extensions, called dendrites, receive incoming messages from other neurons and convey this information toward the cell body.

what are the two output components of the peripheral nervous system?

The output components of the vertebrate PNS are divided into two functional units: the motor system and the autonomic nervous system

what does the parasympathetic system do?

The parasympathetic division, primes the body for activities that gain and conserve energy for the body ("rest and digest"). These effects include stimulating the digestive organs, decreasing the heart rate, and narrowing the bronchi, which correlates with a decreased breathing rate.

define peripheral nervous system

The peripheral nervous system (PNS) is made up mostly of nerves (bundles of axons) in the rest of the body that carry signals into and out of the CNS.

Define the spinal cord. In what way is it conducting information in 2 different directions?

The spinal cord is a bundle of nerve fibers running through the bony spinal column, acting as a communication conduit between the brain and the rest of the body. Millions of nerve fibers within the spinal cord convey sensory information (such as pain) from the body to the brain, while other fibers carry motor information (such as movement) from the brain to the muscles and organs.

what does the sympathetic systems do?

The sympathetic division, tends to have the opposite effect (of the parasympathetic), preparing the body for intense, energy-consuming activities, such as fighting or fleeing ("fight or flight"). When this division is stimulated, the digestive organs are inhibited, the bronchi dilate so that more air can pass through, and the adrenal glands secrete the hormones epinephrine (also called adrenaline) and norepinephrine. (Note--norepinephrine is both a neurotransmitter and a hormone)

how do action potentials relay different intensities of stimuli (given that an action potential is an all or nothing event)?

Varying intensities can be achieved by sending more action potentials in a given amount of time. For example, in the neurons connecting your ears to your brain, loud sounds generate more action potentials per second than quiet sounds.

describe the flow of information from a mosquito biting you to your response

When a mosquito bites you (sensory input), interneurons in your brain process the information (integration) to produce a response by your muscles (motor output), resulting in you slapping the mosquito away.

What determines whether a neuron is affected by a specific neurotransmitter?

Whether it has receptors for that neurotransmitter.

what is a concern regarding drugs that have neuroactive properties

While the drugs mentioned here have the ability to increase alertness and a sense of well-being or to reduce physical and emotional pain, they also have the potential to disrupt the brain's finely tuned neural pathways, altering the chemical balances that are the product of millions of years of evolution.

Do neurotransmitters have multiple functions?

Yes, Neurotransmitters result in many different actions, and a single neurotransmitter, such as dopamine, can play a role in pleasure, attention, memory, sleep, movement, and learning.

how fast do nerve impulses travel and how fast can a stimulus lead to a response

You drop a heavy object toward your foot, and without thinking you jerk your foot out of harm's way. What allows for such a fast response? Electrical transmission occurs at over 330 mph in our bodies—that's over 100 mph faster than a NASCAR racer—which means that a command from your brain can make you move your foot in just a few milliseconds. 330 mph a few milliseconds

1. how many neurons does your brain contain? 2, how many other neurons can a single neuron interact? 3. define neural network

Your brain, for instance, contains an estimated 100 billion neurons, nerve cells that carry electrical signals from one part of the body to another. Each neuron may communicate with thousands of others, forming networks that enable us to move, perceive our surroundings, learn, and remember.

Beethoven, Van Gogh, and Hemingway all had periods of great creativity followed by depression. Based on this information, what disorder would you diagnose them with?

bipolar disorder

what are the two main anatomical divisons of the nervous system

central nervous system and peripheral nervous system

what is the name of the fluid that surrounds the brain and spinal cord?

cerebrospinal fluid

What are two ways neurotransmitter action on a receiving cell may be terminated

enzymatic breakdown or reuptake

In what disease is the corpus callosum thinned?

example, the corpus callosum is often reduced in size and sometimes even absent in autistic individuals.

In a resting neuron, the interior of the neuron is more _________ than the exterior. A stimulus causes _________ charged ions to move inward through ion channels.

negative; positively

depression has been linked to reduced levels of what neurotransmitters?

norepinephrine and serotonin

What are the two distinct sets of neurons of autonomic system?

sympathetic and parasympathetic

define nervous system

the organ system that forms a communication and coordination network throughout an animal's body.

define neurotransmitter

A neurotransmitter is a chemical "messenger" that carries information from a nerve cell to a receiving cell. When the action potential (an electrical signal) reaches the end of the sending neuron, it is converted to a chemical signal consisting of molecules of neurotransmitter. Once a neurotransmitter conveys a chemical signal from the sending neuron, an action potential may then be generated in the receiving cell.

define resting potential and how it is created where is it found is the inside of a nerve cell negative or positive with respect to the outside

A resting neuron has potential energy that exists in the form of an electrical charge difference across the neuron's plasma membrane. The inside of the cell is negatively charged relative to the outside. Because opposite charges are pulled toward each other, the membrane stores energy by holding opposite charges apart, much like a battery. This difference in charge (voltage) that exists across the plasma membrane of a resting neuron is called the resting potential.

define action potential

A stimulus of sufficient strength can trigger an action potential, a nerve signal that carries information along a neuron. The signal is actually a self-propagating change in the voltage across the plasma membrane.

define threshold in the context of generating an action potential

A stimulus triggers the opening of a few of the first set of ion channels in the membrane (represented by the blue arrows), allowing a few positive ions to enter the neuron. This tiny change makes the inside surface of the membrane slightly less negative than before. If the stimulus is strong enough, a sufficient number of channels open to reach the threshold, the minimum change in a membrane's voltage that must occur to trigger the action potential.

What is Alzheimer's disease? What lobe is prominently affected? How common is Alzheimer's in people over 85? Over 65?

Alzheimer's disease is a form of mental deterioration, or dementia, characterized by confusion, memory loss, and a variety of other symptoms. One particularly common characteristic of Alzheimer's disease is the loss of neurons in the temporal lobe. Its incidence is usually age related, rising from about 12% at age 65 to almost 50% at age 85. The disease is progressive; patients gradually become less able to function. There are also personality changes, almost always for the worse. Patients often lose their ability to recognize people, even family members, and may treat them with suspicion and hostility.

how could the complexity of synapses play a role in the nervous systems ability to process large amounts of complex stimuli and formulate appropriate responses?

Chemical synapses can process extremely complex information. A neuron may receive input from hundreds of other neurons via thousands of synaptic terminals (Figure 27.6). The inputs can be highly varied because each sending neuron may secrete a different quantity or kind of neurotransmitter. These factors account for the nervous system's ability to process huge amounts of complex stimuli and formulate appropriate responses.

define synaptic cleft

Chemical synapses have a narrow gap, called the synaptic cleft, separating the synaptic terminal of the sending neuron from the receiving cell

How does the human brain compare to the most sophisticated computer?

Composed of up to 100 billion intricately organized neurons, with a much larger number of supporting cells, the human brain is more powerful than the most sophisticated computer.

Some disorders cause changes in the activity of neurons rather than deterioration or loss of cells. Name a disorder that doesn't result in loss of neurons, but rather a change in activity of certain brain regions.

Depression Rather than causing large structural changes, other neurological disorders alter the activity of certain brain regions. A prominent area of research is determining how the brain's physiology changes during depression (Figure 27.15). Nearly 20 million American adults are affected by depression.

why do action potentials propogate in only one direction?

Dominoes that have fallen need to be set upright before they can be knocked down again. Similarly, an action potential cannot be generated in regions where resting potential is being restored (green in figure). Once the resting potential is reestablished (yellow), an action potential can be generated again.

define integration, where does it occur, what type of neurons are involved?

During integration (green), sensory signals are interpreted and appropriate responses are planned. The nerve cells that integrate the sensory input, interneurons, are typically located in the CNS. Most neurons in the brain are interneurons.

How can the brainstem be injured indirectly when other parts of the brain are injured?

The brainstem is particularly vulnerable when other parts of the brain are injured, because as an injured part of the brain swells, it pushes downward and compresses the brainstem. (The brain has very little room to swell outward because of the hard skull.) This compression of the brainstem in large part explains why a patient's health may deteriorate hours and even days after an initial brain injury.

What does the brainstem control?

The brainstem is the core of the brain, and it receives and sends information to other major regions. It regulates some very vital and basic functions, including breathing and consciousness. Thus individuals with severe brainstem damage may lose the ability to breathe on their own and may become comatose.

What connects the left and right hemispheres?

The corpus callosum, a thick cable of nerve fibers, bridges the two sides and enables them to process information together.

What are the two general types of depressive illness?

Two broad forms of depressive illness have been identified: major depression and bipolar disorder.

Arrange the following neurons into the correct sequence for information flow, from stimulus to response: interneuron, sensory neuron, motor neuron.

sensory neuron to interneuron to motor neuron

In what way is an action potential an example of positive feedback?

the opening of channels causes a change in membrane potential and this causes more channels to open. Hence the result of a process stimulates more of that process, which is the definition of positive feedback.

The debilitating autoimmune disease multiple sclerosis (MS) leads to a gradual destruction of the myelin sheath by the affected individual's own immune system. What symptoms might you predict with MS and why?

trouble moving muscles and coordinating movements because the myelin sheath is damaged.

1. how do drugs such as caffeine and chocolate act on the brain? 2. where does nicotine act? 3. Where does alcohol act?

1. Many common substances, such as caffeine, nicotine, and alcohol, affect the actions of neurotransmitters at the brain's trillions of synapses. For example, caffeine, found in coffee, chocolate, and many soft drinks and energy drinks, counters the effects of neurotransmitters that normally suppress nerve signals. This is why caffeine tends to stimulate you and keep you awake. 2. Nicotine acts as a stimulant by binding to and activating receptors for a neurotransmitter called acetylcholine. 3. Alcohol is a strong depressant; its effect on the nervous system is complex, affecting the function of several neurotransmitters.

define neuron

A nerve cell, the fundamental structural and functional unit of the nervous system, specialize for carrying signals from one area of the body to another

an action potential is a localized event. So, how does it propogate? How is it like a chain of dominoes?

An action potential is a localized event—a change from the resting potential at a specific place along the neuron. A nerve signal starts as an action potential generated near a neuron's cell body. To function as a long-distance signal, this local change must be propagated, that is, passed along the length of the neuron. Propagation of the signal is like tipping the first domino in a standing row: The first domino does not tip over all the other dominos in the row; rather, its fall causes each domino in the row to hit and knock down the next.

what is meant by an action potential is an all or nothing event?

An action potential is an all-or-nothing event. Just as either a light tap or forceful flick of your finger knocks over just one domino, an action potential is the same no matter how weak or strong the stimulus is that initiates it (as long as threshold is reached).

What is the condition that results from repeated head injuries in sports? How is it like Alzheimer's disease?

Another disorder that causes structural changes to the brain is chronic traumatic encephalopathy (CTE). Frequently with CTE, the frontal lobe and temporal lobes show significant deterioration. CTE is caused by repeated brain trauma, particularly concussions, and numerous deceased football players, including well known NFL linebacker Junior Seau, have been diagnosed with CTE posthumously. It's still unclear how forceful a hit to the head must be to cause CTE to develop or how many head injuries it takes to affect progression of the disease. Like Alzheimer's disease, early symptoms include personality changes. Depression, loss of impulse control, and, eventually, memory loss and dementia are prominent features of CTE.

What is the significance of the "association areas" found in the cortex?

Association areas are the sites of higher mental activities—roughly, what we call thinking. Extremely complex interactions among several association areas of different lobes are involved in some activities you might take for granted—such as recognizing a familiar face. When you walk toward a person you know on the street, a visual area processes the information about the person's face, an association area plans for how you'll greet them, and the motor areas send information to muscles that cause you to smile and wave.

What distinguishes major depression from bipolar disorder?

Bipolar disorder includes a manic phase as well as a depressive phase: People with major depression may experience sadness, loss of interest in pleasurable activities, changes in body weight and sleep patterns, and suicidal thoughts. Major depression is extreme and persistent, leaving the sufferer unable to live a normal life. Bipolar disorder, or manic-depressive disorder, involves extreme mood swings. The manic phase is characterized by high self-esteem, increased energy, a flood of thoughts and ideas, as well as behaviors that often involve increased risk taking. The depressive phase is marked by sleep disturbances, feelings of worthlessness, and decreased ability to experience pleasure.

Name the four major lobes found in each cerebral hemisphere of the brain.

Both the right and left hemispheres of the cerebral cortex have four major lobes, each named for a nearby skull bone: the frontal, parietal, temporal, and occipital lobes (represented by different colors in Figure 27.12). Look at the figure.

how might you treat depression with a drug if it is caused by too little serotonin?

Other drugs block the reuptake of neurotransmitters from the sending neuron, effectively increasing the time it is active at the synapse. For example, the most commonly prescribed class of antidepressant medications—the selective serotonin reuptake inhibitors (or SSRIs)—block the reuptake of serotonin. Zoloft and Prozac are examples of SSRIs.

how does the nerve cell membrane create charge separation

How does the membrane keep ions apart in a resting neuron? The hydrophobic interior of the membrane's phospholipid bilayer doesn't let ions pass through (Chapter 4). However, the membrane has protein channels and pumps that can allow positive ions across. By selectively allowing the outflow of positive ions, the membrane's interior becomes negative, and a charge separation is created in a resting neuron.

Are most vertebrate synapses electrical or chemical? What is an advantage of chemical synapses?

However, most synapses in the nervous system of vertebrates are chemical synapses. Chemicals provide more diverse and subtle responses than electrical synapses.

what is an advantage of electrical synapses? where are they found?

In an electrical synapse, electric currents pass directly from one neuron to the next and provide very rapid responses. These synapses are common in invertebrates and are found in some organs of vertebrates, where they help maintain rhythmic muscle contractions.

what accounts for the speed of nerve impulses in humans and many vertebrates?

In humans and many other vertebrates, the speed of nerve signals can be attributed to the myelin sheath, a chain of bead-like supporting cells that wrap around and insulate nerves. Nerve signals are only generated at gaps in the myelin sheath and are transmitted from one gap to the next.

what are the more common causes of spinal cord injuries?

In the United States, males suffer the majority of spinal cord injuries (more than 80%), which are caused primarily by car accidents, falls, and gun shot wounds.

How have brain injuries helped clarify the role of certain brain areas? What did the case of Phineas Gage tells us about the role of the frontal lobes?

Injuries to the brain provide scientists with clues about the function of certain association areas. A well-known example is Phineas Gage (Figure 27.13). In 1848, an explosion propelled a 3-foot-long railroad spike through his head. Incredibly, after recovery from the trauma, it appeared he was able to think normally. However, changes in his personality soon appeared, including a propensity for meanness and impulsiveness. A few years after his death, Gage's remains were exhumed and his skull preserved. Since the 1990s, numerous computer models of his injury have been produced. Although it was once thought that the spike had pierced both frontal lobes, new models of the injury suggest only the left side was affected. Nonetheless, people with frontal lobe injuries often exhibit irrational decision making and difficulty processing emotions, similar to what was first seen with Phineas Gage. The link between the frontal lobes and personality continues to be an active area of neuroscience research, especially in understanding degenerative neurological disorders.

Define quadriplegia and paraplegia and how they occur.

Injury to the CNS is often permanent. Although protected by the bony spinal column, a traumatic blow to the spine can crush delicate nerve bundles. Such trauma may cause quadriplegia (paralysis from the neck down) or paraplegia (paralysis of the lower half of the body), depending where on the spinal column the injury occurs.

define motor output, what neurons mediate it, how is it generated

Integration leads to motor output (purple), the sending of signals from the CNS to the PNS that result in the body's response. Motor neurons are nerve cells that carry output signals to muscles and glands of the body.

How would a drug that inhibits the parasympathetic nervous system affect your heart rate?

It would increase your heart rate.

how might LSD, mescaline act to produce hallucinatory effects? How is marijuana thought to act?

LSD and mescaline may produce their hallucinatory effects by activating serotonin and dopamine receptors. The active ingredient in marijuana binds to brain receptors normally used by other neurotransmitters that seem to play a role in pain, depression, appetite, memory, and fertility.

How is the motor system voluntary?

Neurons of the motor system carry signals to skeletal muscles, mainly in response to external stimuli. When you lift an object, for instance, these neurons carry commands that make your arms move. The control of skeletal muscles is usually voluntary.

What is neuroplasticity? How is neuroplasticity relevant to brain injuries or surgeries of the brain?

Neuroplasticity is the brain's ability to reorganize its neural connections. Neuroplasticity explains much of the recovery that can sometimes be seen in patient's when a portion of the brain is lost or injured.

where are synaptic terminals found

Notice that the axon ends in a cluster of branches. A typical axon has hundreds or thousands of these branches, and each branch ends with a synaptic terminal, which relays signals to a receiving cell.

describe how the opening and closing of two sets of ions channels accounts for a nerve signal or action potential

Once threshold is reached, more of these channels open and more positive ions rapidly rush in. As a result, the interior of this region of the cell becomes positively charged with respect to the outside. This electrical change triggers the closing of the first set of channels. Meanwhile, a second set of channels opens (green arrows), allowing other positive ions to diffuse rapidly out and returning the membrane to its resting potential. Within a living neuron, this whole process takes just a few milliseconds, meaning a neuron can produce hundreds of nerve signals in a second.

How does the structure of a synapse ensure that signals pass only in one direction, from a sending neuron to a receiving cell?

Only the sending cell is specialized to release neurotransmitter. In contrast, the receiving cell has specialized receptors for the neurotransmitter

how are opiates (heroin) thought to reduce pain and cause euphoria?

Opiates— morphine, codeine, and heroin—bind to the receptors for the neurotransmitter endorphin, reducing pain and producing euphoria. Opiates are thus usually prescribed to relieve pain.

what determines the effects of a traumatic injury to the brain, why can such trauma have a variety of different effects?

Trauma to the brain can have a variety of effects—such as personality changes, coma, or death— depending on what part of the brain is affected.

What does the cerebrum or cerebral cortex do?

The intricate neural circuitry of the cerebral cortex helps produce our most distinctive human traits: reasoning and mathematical abilities, language skills, imagination, artistic talent, and personality traits. Integrating information it receives from our senses, the cerebral cortex creates our sensory perceptions—what we are actually aware of when we see, hear, smell, taste, or touch. The cerebral cortex also regulates our voluntary movements.

what is meningitis? What forms can it take? How is it diagnosed?

The meninges may become inflamed (termed meningitis) if the cerebrospinal fluid becomes infected. Infection is confirmed by inserting a needle into the spinal column to collect a sample of cerebrospinal fluid. Viral meningitis is generally not harmful, but bacterial meningitis can be deadly. Bacterial meningitis is not highly contagious, spreading only through direct contact, when sharing drinks or kissing, for example.

define synapse name 3 types of receiving cells

To continue conveying information, the signal must be passed to another cell. This occurs at a synapse, a relay point between a neuron and a receiving cell. The receiving cell can be another neuron or another cell type such as a muscle cell or a hormone secreting cell.