Chapter 3 The Nervous System

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Nervous System

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The body's electrochemical communication circuitry.

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Dendrite

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Treelike fibers projecting from a neuron, which receive information and orient it toward the neuron's cell body.

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Cell Body

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The part of the neuron that contains the nucleus, which directs the manufacture of substances that the neuron needs for growth and maintenance.

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Complexity

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Your brain is carrying out a multitude of functions, including seeing, reading, learning, and breathing. Extensive assemblies of nerve cells participate in each of these activities, all at once.

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Integration

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The brain does a wonderful job of pulling information together. Sounds, sights, touches, tastes, and smells the brain integrates all of these sensory inputs so that you can function in the world.

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Plasticity

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The brain’s special capacity for change

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Electrochemical Transmission

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The brain and the nervous system function essentially as an information-processing system powered by electrical impulses and chemical messengers.

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Central Nervous System

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The brain and spinal cord

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Peripheral Nervous System

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· The network of nerves that connects the and spinal cord to other parts of the body

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Somatic System

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· The body system consisting of the sensory nerves, whose function is to convey information from the skin and muscles to the CNS about conditions such as pain and temperature, and the motor nerves, whose function is to tell muscles what to do.

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Autonomic System

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· The body system that takes messages to and from the body’s internal organs, monitoring such processes as breathing, heart rate and digestion.

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Sympathetic Nervous System

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The part of the autonomic nervous system that arouses body to mobilize it for action and thus is involved in the experience of stress.

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Parasympathetic Nervous System

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· The part of the autonomic nervous system that calms the body.

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Neuron

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One of the two types of cells in the nervous system; neurons are the nerve cells that handle the information-processing function.

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Axon

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The part of the neuron that carries information away from the cell body toward other cells

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Myelin Sheath

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A layer of fat cells that encases and insulates most axons.

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Neural Impulse

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A neuron sends brief electrical impulses through its axon. By changing the rate of the signals the neuron can vary its message. Those impulses traveling down the axon are electrical. The axon is a tube encased in a membrane filled with ions. The sodium and potassium carry positive charges and negatively charged ions like chlorine. The membrane semipermeable.

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Action Potential

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The brief wave of positive electrical charge that sweeps down the axon.

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Resting Potential

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The stable, negative charge of an inactive neuron.

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Threshold

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Electrical impulse reaches a certain level of intensity

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All-or-Nothing Principle

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· The principle that once the electrical impulse reaches a certain level of intensity (its threshold), it fires and moves all the way down the axon without losing any intensity.

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Synaptic Transmission

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At the synapse, neurotransmitters are released from the sending neuron, and some of these attach to receptor sites on the receiving neuron, where they stimulate another electrical impulse.

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Synapses

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· Tiny spaces between neurons; the gaps between neurons are referred to as synaptic gaps.

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Terminal Buttons

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Each axon branches out into numerous fibers that end in structures

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Synaptic Vesicles

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Store various neurotransmitters that are released at the synapse.

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Neurotransmitters

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· Chemical substances that are stored in very tiny sacs within the terminal buttons and involved in transmitting information across a synaptic gap to the next neuron.

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Reuptake

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Some of the neurotransmitter is used up in the production of energy and some of it is reabsorbed by the axon that release it to await the nest neural impulse. The reabsorption is called this.

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Acetylcholine

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Stimulates the firing of neurons and is involved in muscle action, learning, and memory. Found throughout the CNS and PNS. A deficiency in this is attributed with Alzheimer disease.

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GABA

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Found throughout the central nervous system. Plays a key function in the brain by inhibiting many neurons from firing. Low levels are linked with anxiety.

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Glutamate

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Excites many neurons to fire and is especially involved in learning and memory. Too much can overstimulate the brain and trigger migraine headaches or even seizures.

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Norepinephrine

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Stress stimulates the release of another of the body's neurotransmitters. It inhibits the firing of neurons in the CNS but it simultaneously excites the heart muscle, intestines, and urogenital tract. Controls alertness, too much triggers agitation or jumpiness. Too little is associated with depression.

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Dopamine

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Helps to control voluntary movement and affects sleep, mood, attention, learning, and the ability to recognize opportunities for rewarding experiences in the environment . Low levels are associated with Parkinson disease. High levels and receptors are associated with schizophrenia.

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Serotonin

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Involved in the regulation of sleep, mood, attention, and learning.

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Endorphins

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Are natural opiates- substances that depress nervous system activity and eliminate pain- that mainly stimulate the firing of neurons. Shields the body from pain and elevate feelings of pleasure. Long-distance runner, a woman giving birth, and a person in shock after a car wreck all have elevated levels.

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Oxytocin

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A hormone and neurotransmitter that plays an important role in the experience of love and social bonding. A surge of this is released in mothers who just gave birth, related to the onset of lactation, released as part of sexual orgasm, and formed emotional bonds.

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CAT Scan

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Imaging technique produces a 3D image obtained from X rays of the head that are assembled into a composite image by a computer. Provides valuable information about the location and extent of damage involving stroke, language disorder, or loss of memory.

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PET Scan

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Based on metabolic changes in the brain related to activity. Measures the amount of glucose in various areas of the brain and sends this information to a computer analysis. Neurons use glucose for energy, so glucose levels vary with the levels of activity throughout the brain.

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MRI

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Involves creating a magnetic field around a person's body and using radio waves to construct images of the person's tissues and biochemical activities. H found in H2O act as magnets when they encounter a very strong magnetic field, they align with it.

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fMRI

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Allows scientists literally to see what is happening in the brain while it is working. The field of cognitive neuroscience has benefited from this scan. Tells us about the brain activity associated with a mental experience is a correlational statement.

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TMS

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Method for studying brain functioning and one that does allow for causal inferences. Used to establish causal links between brain activity and behavior to examine neuronal functioning following brain-injuring events such as accidents and strokes, and treat some neurological and psychological disorders. Virtual lesions are created by bursts of action potentials activity in the targeted brain area is inhibited.

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Medulla

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Begins where the spinal cord enters the skull. Controls many vital functions, such as breathing and heart rate. Also regulates our reflexes.

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Pons

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A bridge in the hindbrain that connects the cerebellum and the brain stem. Contains several clusters of fibers involved in sleep and arousal.

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Cerebellum

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Extends fro the rear of the hindbrain. It consists of two rounded structures thought to play important roles in motor coordination.

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Reticular Formation

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A system in the midbrain comprising a diffuse collection of neurons involved in stereotyped patterns of behavior such as walking, sleeping, and turning to attend to a sudden noise.

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Amygdala

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An almond shaped structure within the base of the temporal lobe that is involved in the discrimination of objects that are necessary for the organism’s survival, such as appropriate food, mates, and social rivals.

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Hippocampus

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· The structure in the limbic system that has a special role in the storage of memories.

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Thalamus

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The structure in the limbic system that has a special role in the storage of memories.

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Basal Ganglia

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· Large neuron clusters located above the thalamus and under the cerebral cortex that work with the cerebellum and the cerebral cortex to control and coordinate voluntary movements.

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Hypothalamus

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A small forebrain structure, located just below the thalamus, that monitors three pleasurable activities-eating, drinking, and sex-as well as emotion, stress, and reward. Olds and Milner implanted an electrode in the hypothalamus of a rat's brain. When the rat ran to a corner a mild electric current was delivered to its hypothalamus. They found out this area is involved in pleasurable feelings.

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Cerebral Cortex

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Part of forebrain, the outer layer of the brain, responsible for the most complex mental functions, such as thinking and planning.

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Hemispheres

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The wrinkled surface of the cerebral cortex is divided into two halves

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Lobes

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Each hemisphere is subdivided into four regions

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Occipital Lobe

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Structures located at the back of the head that respond to visual stimuli.

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Temporal Lobe

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· Structures in the cerebral cortex that are located just above the ears and are involved in hearing, language processing, and memory.

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Frontal Lobe

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The portion of the cerebral cortex behind the forehead, involved in personality, intelligence, and the control of voluntary muscles.

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Parietal Lobe

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· Structures at the top and toward the rear of the head that are involved in registering spatial location, attention, and motor control.

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Somatosensory Cortex

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A region in the cerebral cortex that processes information about sensation, located at the front of the parietal lobes.

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Motor Cortex

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A region in the cerebral cortex that processes information about voluntary movement, located just behind the frontal lobe.

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Association Cortex

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The region of the cerebral cortex that is the site of the highest intellectual functions, such as thinking and problem solving.

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Broca's Area

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Located in the brain's left hemisphere and is involved in the control of speech. Individuals with damage to this area have problems saying words correctly.

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Wenicke's Area

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The portion of the left hemisphere that is involved in understanding language. Individuals with damage to this area cannot comprehend words, they hear the word but do not know what they mean.

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Corpus Callosum

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· The large bundle of axons that connects the brain’s two hemispheres, responsible for relaying information between the two sides.

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Left Hemisphere

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Specialized in Verbal processing, speech, grammar. Includes Broca's and Wernicke's Area.

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Right Hemisphere

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Specialized in spatial perception, visual recognition, and emotion. The simple comprehension area.

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Endocrine System

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The body system consisting of a set of glands that regulate the activities of certain organs by releasing their chemical products into the bloodstream.

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Glands

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Organs or tissues in the body that create chemicals that control many of our bodily functions.

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Hormones

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Chemical messengers that are produced by the endocrine glands and carried by the bloodstream to all parts of the body

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Three Methods of Repair

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Collateral sprouting- the process by which axons of some healthy neurons adjacent to damaged cells grow new branches.

Substitution of Function- the process by which the damaged region's function is taken over by another area or areas of the brain.

Neurogenesis- the process by which new neurons are generated.

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Brain Grafts

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Implants of healthy tissue into damaged brains. Have a greater potential success when the brain tissue used is from the fetal stage- an early stage in prenatal development.

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Stem Cells

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· Unique primitive cells that have the capacity to develop into most types of human cells.

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Stress

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The responses of individuals to environmental stressors

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Stressors

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Circumstances and events that threaten individuals and tax their coping abilities and that cause physiological changes to ready the body to handle the assault of stress.

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Acute Stress

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The stress that occurs in response to an immediate perceived threat. When the stressful situation ends, so does the stress.

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Chronic Stress

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Stress that goes on continuously- may lead to persistent autonomic nervous system arousal.