After reviewing the Chp. 2 power point, please de
After reviewing the Chp. 2 power point, please describe the differences between the central nervous system, somatic nervous system, and autonomic nervous system. Also, describe the 4 lobes of the cebreral cortex and what each of their functions are.
Your discussions must be a minimum of 2 paragraphs. Please use proper grammar and punctuation.
Module 2.1 Neurons: The Body’s Wiring
Module 2.2 The Nervous System: Your Body’s Information Superhighway
Module 2.3 The Brain: Your Crowning Glory
Module 2.4 Methods of Studying the Brain
Module 2.5 The Divided Brain: Specialization of Function
Module 2.6 The Endocrine System: The Body’s Other Communication System
Module 2.7 Genes and Behavior: A Case of Nature and Nurture
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Module 2.1
Neurons:
The Body’s Wiring
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Myelin
Sheath
Axon
Terminal Buttons and Synapses
Dendrites
© Cengage Learning
Soma
There are two major types of cells in the nervous system: glial and neurons. Glial cells are a kind of “glue” that helps nourish neurons and helps hold them together, among other functions. Glial cells also make up the myelin sheath that insulates the axons of many neurons.
Neurons are cells that receive, integrate, and transmit information. In the human nervous system, the vast majority are interneurons-–neurons that communicate with other neurons. There are also sensory neurons, which receive signals from outside the nervous system, and motor neurons, which carry messages from the central nervous system to the muscles that move the body. A third type of neuron, called an interneuron, connects two other neurons. In the brain, they process information from sensory organs and control higher mental functions, such as planning and thinking. In the spinal cord, they connect sensory neurons and motor neurons.
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Soma
The soma, or cell body, contains the cell nucleus and much of the chemical machinery common to most cells.
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Dendrites
The branched structure is called a dendritic tree, and each individual branch is a dendrite. Dendrites are the parts of a neuron that are specialized to receive information
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© Cengage Learning
Axon
The long fiber is the axon. Axons are specialized structures that transmit information to other neurons or to muscles or glands.
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Myelin Sheath
Most human axons are wrapped in a myelin sheath. Myelin is a white, fatty substance that serves as an insulator around the axon and speeds the transmission of signals. In people suffering from multiple sclerosis, some myelin sheaths degenerate, slowing or preventing nerve transmission to certain muscles.
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Terminal Buttons and Synapses
The axon ends in a cluster of terminal buttons, which are small knobs that secrete chemicals called neurotransmitters. These chemicals serve as messengers that may activate neighboring neurons.
The points at which neurons interconnect are called synapses. A synapse is a junction where information is transmitted from one neuron to another.
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Glial Cells
© Cengage Learning
More numerous than neurons, glial cells come in a variety of forms. Their main function is to support the neurons by, among other things, supplying them with nutrients and removing waste material. In the human brain.
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Axon
Inside
Electrode
Outside
Electrode
The neuron at rest is a tiny battery, a store of potential energy. Inside and outside the axon are fluids containing electrically charged atoms and molecules called ions. Positively charged sodium and potassium ions and negatively charged chloride ions are the principal molecules involved in the nerve impulse.
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© Cengage Learning
Axon
Inside
Electrode
Outside
Electrode
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When the neuron is not conducting an impulse, it is said to be in a resting state. The cell membrane is polarized–negatively charged on the inside and positively charged on the outside. The charge difference across the membrane can be measured with a pair of microelectrodes connected to an oscilloscope. In a resting neuron, this difference, called the resting potential, is about –70 millivolts.
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Click to play animation. Make sure volume is turned up.
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Axon
Inside
Electrode
Outside
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© Cengage Learning
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When the neuron is stimulated, channels in its cell membrane open, briefly allowing positively charged ions to rush in. For an instant, the neuron’s charge becomes less negative and momentarily shifts to a positive charge. This change in polarization is called an action potential.
An action potential is a very brief shift in the neuron’s electrical charge that travels along an axon.
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© Cengage Learning
Here we see a representation of how positively charged sodium (Na+ ions) enter the cell, which has the effect of temporarily changing the cell’s charge from negative to positive, which results in propagation of an action potential. As the action potential passes, the cell restores its negative charge by closing sodium gates and pushing positively charged potassium ions (K+) through the membrane.
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Action Potential
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The size of an action potential is not affected by the strength of the stimulus—a weaker stimulus does not produce a weaker action potential. If the neuron receives a stimulus of sufficient strength, it fires, but if it receives a weaker stimulus, it doesn’t. This is referred to as the “all-or-none” principle.
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Synaptic Gap
Terminal Buttons and Synapses
The neural impulse is a signal that must be transmitted from one neuron to other neurons.
This transmission takes place at special junctions called synapses, into which chemical messengers called neurotransmitters are released by the terminal buttons.
The two neurons are separated by the synaptic gap, a microscopic gap between the terminal button of one neuron and the cell membrane of another neuron. Signals have to cross this gap for neurons to communicate.
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Synaptic
Vesicles
Neurotransmitter
Molecules
Neurotransmitters are chemicals that transmit information from one neuron to another.
Within the terminal buttons, neurotransmitters are stored in small sacs called synaptic vesicles.
Note that neurotransmitters can have both excitatory and inhibitory effects.
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© Cengage Learning
The neurotransmitters are released when an action potential causes sacs or vesicles at the end of the axon to spill its contents of neurotransmitters into the synaptic gap. After their release, neurotransmitters diffuse across the synaptic cleft to the membrane of the receiving cell, which stimulates the receiving (postsynaptic) cell to propagate an action potential of its own.
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Storage of neurotransmitter
Molecules in synaptic vesicles
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Release of neurotransmitter
molecules into synaptic cleft
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Binding of neurotransmitters
at receptor sites on
postsynaptic membrane
© Cengage Learning
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Reuptake of neurotransmitters
absorbed by the
presynaptic neuron
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Inactivation (by enzymes)
or removal (drifting away)
of neurotransmitters
After producing postsynaptic potentials, some neurotransmitters either become inactivated by enzymes, or drift away. Most neurotransmitters, however, are reabsorbed into the presynaptic neuron through reuptake – a process in which neurotransmitters are sponged up from the synaptic cleft by the presynaptic membrane.
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© Cengage Learning
Here we see a schematic representation of the process of neural transmission from one neuron to another and the reuptake process in which excess molecules of neurotransmitters are reabsorbed by the transmitting neuron.
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Agonists
Stimulants (caffeine, amphetamine, cocaine)
Antianxiety drugs
Antidepressants
Morphine, heroin
Antagonists
Antipsychotic drugs
Psychoactive drugs can be classified in terms of their effects on neurotransmitter functioning. Agonists mimic the effects of certain neurotransmitters or increase the availability of neurotransmitters. Antagonists work in the opposite fashion by blocking receptor sites for particular neurotransmitters. The specific neurotransmitters targeted by these drugs are discussed in the textbook.
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Neurotransmitters
Related Disorders
Dopamine
Parkinson’s disease
Schizophrenia
Norepinephrine
Depressive disorders
Serotonin
Depressive disorders
Obsessive-compulsive disorder
Eating disorders
GABA
Anxiety disorders
Specific neurotransmitters work at specific kinds of synapses – the study of which has led to interesting findings about how specific neurotransmitters regulate behavior.
Here are a few examples of physical and mental disorders linked to irregularities or dysfunction of neurotransmitter functioning.
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Module 2.2
The Nervous System:
Your Body’s Information Superhighway
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© Cengage Learning
The multitudes of neurons in your nervous system have to work together to keep information flowing effectively. The nervous system consists of two major parts, the central nervous system (brain and spinal cord) and the peripheral nervous system (the network of nerve pathways that connect the central nervous system to the muscles, glands, and other parts of the body).
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The central nervous system, or CNS, consists of the brain and spinal cord. We can see that the CNS is situated centrally in the body.
The spinal cord houses bundles of axons that carry sensory information from the peripheral nervous system to the brain and conveys commands from the brain to the peripheral nervous system.
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Spinal Cord
A column of nerves between the brain and peripheral nervous system
Brain
Divided into three major parts: the lower part or hindbrain, the midbrain, and the forebrain
Central Nervous System
The body’s master control unit
Here we see how the peripheral nervous system is organized. The autonomic nervous system is comprised of two divisions, the sympathetic and the parasympathetic nervous systems. These two divisions have largely opposite effects.
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© Cengage Learning
Sometimes it’s best not to use your brain before you act. A spinal reflex is controlled at the level of the spinal cord, allowing you to respond more quickly than would be case if the signal needed to be transmitted to the brain for processing.
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The withdrawal reflex is another example of a spinal reflex.
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The peripheral nervous system is made up of all the nerves that lie outside the brain and spinal cord. Nerves are bundles of neuron fibers or axons that are routed together in the peripheral nervous system.
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Autonomic Nervous System
Somatic Nervous System
The peripheral nervous system can be divided into two parts.
The somatic nervous system is made up of nerves that connect to voluntary skeletal muscles and sensory receptors. They carry information from receipts in the skin, muscles, and joints to the CNS, and from the CNS to the muscles.
The autonomic nervous system is made up of nerves that connect to the heart, blood vessels, smooth muscles, and glands. It controls automatic, involuntary, visceral functions that people don’t normally think about, such as heart rate, digestions, and perspiration.
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Somatic Nervous System
Carries information from sensory organs
to the central nervous system and relays motor (movement) commands to muscles
Sympathetic
Nervous System
Mobilizes bodily resources in response to threat by speeding up heart rate and respiration and drawing stored energy from bodily reserves
Parasympathetic
Nervous System
Replenishes bodily resources by promoting digestion and slowing down other bodily processes
Autonomic Nervous System
Regulates involuntary bodily processes, including heart rate, respiration, digestion and pupil contraction; operates automatically without conscious direction
Here we see how the peripheral nervous system is organized. The autonomic nervous system is comprised of two divisions, the sympathetic and the parasympathetic nervous systems. These two divisions have largely opposite effects.
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© Cengage Learning
Parasympathetic vs. Sympathetic Control
Pupils constricted
Pupils dilated
Salivation stimulated
Salivation inhibited
Bronchial passages constricted
Bronchial passages dilated
Decreased respiration
Increased Respiration
Decreased heart rate
Increased heart rate
Digestion stimulated
Digestion inhibited
Secretion of adrenal hormones
Bladder contracted
Increased secretion
by sweat glands
Hair follicles raised;
goose bumps
Bladder relaxed
When a person is aroused, automatic bodily functions speed up. This speeding up is controlled by the sympathetic division of the autonomic nervous system. The effects of sympathetic activation on shown on the right side of the diagram.
The sympathetic nervous system mobilizes the body’s resources for emergencies and creates the fight-or-flight response.
The parasympathetic nervous system, on the other hand, conserves bodily resources to save and store energy, as in the process of digestion. Parasympathetic effects are shown on the left side of diagram.
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Module 2.3
The Brain:
Your Crowning Glory
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© Cengage Learning
The Brainstem
Thalamus
Midbrain
Pons
Medulla
Spinal cord
Cerebellum
Medulla
Pons
The brain is organized in three major parts: the hindbrain, the midbrain, and the forebrain.
The hindbrain includes the cerebellum and two structures found in the lower part of the brainstem: the medulla and the pons.
The cerebellum is critical to the coordination of movement and to the sense of equilibrium, or physical balance. Damage to the cerebellum disrupts fine motor skills, such as those involved in writing or typing.
The pons contains several clusters of cell bodies that contribute to the regulation of sleep and arousal.
The medulla, which attaches to the spinal cord, has charge of largely unconscious but essential functions, such as regulating breathing, maintaining muscle tone, and regulating circulation.
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Midbrain
The midbrain is mostly concerned with relaying sensory information to the forebrain.
The midbrain helps to control the voluntary movement of the eyes. It is part of the brainstem, and also contains the reticular formation (or the reticular activating system, or RAS).
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The Reticular
Formation
Running through both the hindbrain and the midbrain is the reticular formation. Lying at the central core of the brainstem, the reticular formation is best known for its role in the regulation of processes of attention, alertness and arousal. It helps to screen visual and auditory sensory input so that irrelevant information is filtered out and not processed in the higher processing centers of the brain.
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Forebrain
The forebrain is the largest and most complex region of the brain, encompassing a variety of structures, including the thalamus, hypothalamus, limbic system, and the two cerebral hemispheres.
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Thalamus
Hypothalamus
© Cengage Learning
© Cengage Learning
The thalamus is a structure in the forebrain through which all sensory information, except smell, must pass to get to the cerebral cortex. This way station is made up of a number of clusters of cell bodies, or nuclei. Each cluster is concerned with relaying sensory information to a particular part of the cortex. The thalamus also receives information from the basal ganglia, which play a key role in regulating voluntary movement.
The hypothalamus performs many functions, including regulation of hunger, sleep, and the body’s stress response. As we will see later, it is also crucial in regulating the functions of the endocrine system.
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The limbic system is a loosely connected network of structures involved in emotion, motivation, memory, and other aspects of behavior. The structures of the limbic system include the amygdala, the hippocampus, parts of the thalamus and hypothalamus, and other nearby structures.
The amygdala is a set of two structures that trigger the emotional response of fear when we encounter a threatening stimulus.
The hippocampus is located just behind the amygdala and is involved in the formation of new memories.
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Occipital
Parietal
Frontal
Temporal
© Cengage Learning
The cerebral cortex is so large that it is divided into two halves, or hemispheres. These halves are connected by a thick, tough band of nerve fibers called the corpus callosum.
Each cerebral hemisphere is divided by deep fissures into four parts called lobes. To some extent, each of these lobes is dedicated to specific purposes.
The occipital lobe includes the primary visual cortex, which is a cortical area where most visual signals are sent and visual processing is begun.
The parietal lobe includes the primary somatosensory cortex, an area that registers the sense of touch.
The temporal lobe contains the primary auditory cortex, an area devoted to auditory processing.
The frontal lobes are the site of higher mental functions, including thinking, calculating, planning, problem solving, and decision making.
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The Lobes of the Cerebral Cortex
| Structure | Functions |
| Occipital lobes | Process visual information, giving rise to sensations of vision |
| Parietal lobes | Process information relating to sensations of touch, pressure, temperature (hot and cold), pain, and body movement |
| Frontal lobes | Control motor responses and higher mental functions, such as thinking, planning, problem solving, decision making, and accessing and acting on stored memories |
| Temporal lobes | Process auditory information, giving rise to sensations of sound |
Here we have a nice summary of the general functions controlled by each lobe of the cerebral cortex.
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Exciting new work on mirror neurons is discussed in this video.
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Module 2.4
Methods of Studying
the Brain
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Lesioning
Electrical recording
Electrical stimulation
Investigators also use more invasive means of studying brain functioning in laboratory animals used in experimental research.
Lesioning involves the destruction of a piece of the brain in order to observe what happens.
Electrical recording involves placing electrodes in brain structures to measure the electrical activity of various parts of the brain.
Electrical stimulation involves sending a weak electric current into the brain to observe the effects on particular brain structures.
EEG (electroencephalograph)
CT (computed tomography) scan
Also called a CAT scan
PET (positron emission tomography) scan
MRI (magnetic resonance imaging)
fMRI (functional MRI)
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Physicians today use many different types of brain imaging to diagnose neurological or brain disorders. Investigators use these technique to learn more about brain functioning.
In EEG (an electroencephalograph) a device that uses electrodes is attached to the scalp to measure brain wave activity
A computer tomography (CT) scan is a computer-enhanced X-ray that provides images of the internal brain structures.
A positron emission tomography (PET) scan uses computer-generated images of the brain, formed by tracing the amounts of glucose used in different parts of the brain during different types of activity.
A magnetic resonance imaging (MRI) produces computerized images of the brain and other body parts by measuring the signals they produce when placed in a strong magnetic field.
A newer form of MRI is called functional magnetic resonance imaging, or fMRI, which takes snapshots of the brain in action. It is used to assess both the function and structures of the brain.
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CT Scan
X-ray
Source
X-ray
Detectors
Fan
Shaped
Beam
© Cengage Learning
CT Scan
The CT scan provides a three-dimensional X-ray image of bodily structures. It can reveal structural abnormalities in the brain that may be associated with blood clots, tumors, brain injuries, or psychological disorders such as schizophrenia.
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Pascal Goetgheluck/Science Source
PET Scan
The PET scan measures the metabolic activity of the brain. More active regions are highlighted in yellow and red while less active regions appear as blue and green. This PET scan shows a patient suffering from withdrawal from alcoholism. As you move from the top to the bottom rows you can see how more brain activity appears as more time without alcohol in the system passes.
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© 2001 American Association for the Advancement of Science
fMRI
The red areas of these fMRI images indicate parts of the brain that are more active when a person is shown pictures of faces. The blue areas denote parts of the brain that are more active when the viewer is shown an image of buildings.
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Can functional magnetic resonance imaging (fMRI) help researchers to “read the minds” of subjects?
This video discusses how fMRI is helping to predict what people see and what they are paying attention to.
Also, how fMRI is helping neuroscientists to better understand the human visual system and related cognitive processes.
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Module 2.5
The Divided Brain: Specialization of Function
Left hemisphere: Specialized for language abilities, logical reasoning, and problem solving.
Right hemisphere: Specialized for nonverbal processing.
But note that people are not “left-brained” or “right-brained.” Information passes back and forth along the corpus collosum.
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Stimulus in Left
Half of Visual Field
Fixation Point
Left Eye
Left Hemisphere
(Control of Right Hand)
Optic Nerves
Information Delivered
to Left Visual Processing Area
Stimulus in Right
Half of Visual Field
Right Eye
Right Hemisphere
(Control of Light Hand)
Severed Corpus Callosum
Information Delivered
to Right Visual Processing Area
© Cengage Learning
Lateralization refers to the division of functions between the right and left hemispheres of the cerebral cortex.
Each hemisphere’s primary sensory and motor connections are to the opposite side of the body – the left hemisphere controls and communicates with the right hand, arm, etc. and the right hemisphere controls and communicates with the left side.
Vision is more complex. Stimuli in the right half of the visual field are registered by receptors on the left side of each eye that send signals to the left hemisphere.
Similarly, stimuli in the left half of the visual field are registered by receptors on the right side of each eye that send signals to the right hemisphere.
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Production
of Speech
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