how the brain governs behavior

This post was published to My College Class Notes at 4:56:36 AM 5/28/2008

How the Brain Governs BehaviorAccountCategory

Focus Questions

How do the neurons work and what do they do?

The brain governs all physical and psychological functions through its connection with other parts of the body.

The brain contains many billions of neurons, or neural cells; each neuron receives messages, processes them, and transmits them to thousands of other neurons throughout the body.

Some neurons act as glands and transmit into the bloodstream various hormones, which affect the bodily functioning in areas distant from the brain.

The brain also contains even more billions of glia, which performs functions such as regulating the biochemical environment of the brain, helping sustain neurons, modulating neural transmissions, and helping guide early brain development and maturation.

Each neuron in the nervous system is a fiberlike cell with receivers call dendrites at one end and senders call terminal braches at the other.

Stimulation of the neurons at its dendrites—or receptor sites on its cell body—sets off an electrical impulse that travels the length of the axon to the terminal branches.

There the stage is set for stimulation or inhibition of other neurons, as well as muscles or glands. Other important structures include the nucleus, myelin sheath, and nodes.

A neuron ordinarily fires in accord with the all-or-none principle.

The key to the transmissions of nervous messages is the synapse, a junction where the sender of one neuron is separated by only a microscopic distance from the receiver of another neuron.

When the neuron fires, it releases neurotransmitters, which flow across the synaptic cleft and act on receiving neurons.Crazy Joe’s Psych 101 Notes IV Prof. T.R. Tharney: PSY101 Chapter 2: pp. 1

Crazy Joe’s Psych 101 Notes IV Prof. T.R. Tharney: PSY101 Chapter 2: pp. 2

What constitutes the central nervous system?

The central nervous system (CNS) is made up of the brain and the spinal cord. The neurons of CNS affect functions and behavior throughout the rest of the body through the peripheral nervous system (PNS).

Afferent Neurons carry information from the sense organs to the brain; efferent neurons carry messages from the brain to the glands and muscles; and interneurons are the intermediaries between other neurons in the CNS.

Why do psychologist and other scientist place so much emphasis on understanding the functions of the brain’s outer surface?

The topmost and largest area of the brain is the cerebrum, which is covered by the cerebral cortex; each is divided down the middle into a left hemisphere and a right hemisphere.

The cerebral cortex, which is larger in relation to body size in human beings that in any other species, is the part of the brain primarily responsible for higher processes such as thinking, remembering, and planning. When damaged, it sometimes displays remarkable plasticity.


HOW THE BRAIN GOVERNS BEHAVIOR: NEURON DEFINITIONS

Neuron The Neural cell; the basic unit of the nervous system

Dendrites The primary “receiving” parts of a neuron.

Receptors Sites Spots on the cell body of a neuron that, like the dendrites, can be stimulated by other neurons.

Cell Body The part of a neuron that converts oxygen, sugars and other nutrients into energy

Nucleus The core of the cell body of a neuron or other cell, containing the genes.

Axon The fibrous body of a neuron that carries the neural impulse to the terminal branches.

Myelin sheath A whitish coating of fatty protective tissue that “insulates” the axons of neurons.

Nodes Constrictions of the myelin sheath of an axon that act as booster stations for neural impulses.

Terminal branches The parts of a neuron that send messages to other neurons or to muscles or glands.

Synapse The connecting point where a terminal branch of one neuron is only a microscopic distance from a dendrite or receptor site of another neuron.

Neurotransmitters Biochemicals released at neuron synapses that aid or inhibit neural transmission.

Hormone A biochemical that typically is released into the bloodstream to perform its function at locations distance form the brain, but that can also effect brain functioning itself.

GliaCells that perform a wide array of functions such as regulating the biochemical environment of the brain, helping sustain neurons, modulating neural transmissions, and aiding in the repair of neurons in case of injury. They are also important in early brain development.

All-or-none Principle The general rule that a neuron either fires or doesn’t


HOW THE BRAIN GOVERNS BEHAVIOR: CNS DEFINITIONS

Functions of the Cerebral Cortex

Many motor and sensory functions have been “mapped” to specific areas of the cerebral cortex, some of which are indicated here. In general, these areas exist in both hemispheres of the cerebrum, each serving the opposite side of the body. Less well defined are the areas of association, located mainly in the frontal cortex, operative in functions of thought and emotion and responsible for linking input from different senses. The areas of language are an exception: both Wernicke’s area, concerned with the comprehension of spoken language, and Broca’s area, governing the production of speech, have been pinpointed on the cortex.

Spinal Cord The thick cable of neurons that mostly connects PNS neurons to the brain.

Central Nervous System (CNS)

The brain and the spinal cord

Peripheral Nervous System (PNS)

The network of neurons outside of the CNS

Interneuron A CNS neuron that carries messages between neurons.

Cerebral cortex Among its many other functions, the part of the brain responsible for thinking, remembering, and planning.

Cerebrum The large brain mass that is covered by the cerebral cortex.

Plasticity The power of the brain to reorganize and shift functions.


Chapter 2: How Neuroscientist Study the Brain and Mind

Focus Questions

How does brain imaging work and what does it tell us?In mapping the brain and studying its structures and functions, researchers once had to rely on changes in behavior that were attributable to brain damage. They later began studying brain lesions in laboratory animals and using electrical brain stimulation (EBS) in humans. Computerized tomography (CT) and Magnetic resonance imaging (MRI) are methods of studying brain structures but not brain functioning.Positron emission tomography (PET) and Functional magnetic resonance imaging (fMRI) are methods of studying brain structures and pathways, as well as what they do, in an ongoing manner.

How do neuroscientists measure electrical changes and what do they tell us?Electroencephalography (EEG) is a method of measuring overall brain electrical activity. Quantitative Electroencephalography (QEEG) allows measurement of precise event-related potentials (ERPs).

HOW NEUROSCIENTIST STUDY THE BRAIN AND MIND: DEFINITIONS

MRI (Magnetic Resonance Imaging) Scan

Radiology uses X rays and other forms of radiant energy to both diagnose and treat diseases. This magnetic resonance imaging (MRI) scan of a normal adult head shows the brain, airways, and soft tissues of the face. The large cerebral cortex, appearing in yellow and green, forms the bulk of the brain tissue; the circular cerebellum, center left, in red, and the elongated brainstem, center, in red, are also prominently visible.

Computerized tomography (CT)

A structural brain imaging method that uses X-rays to produce two-dimensional images.

Magnetic resonance imaging (MRI)

A structural brain imaging method that uses the magnetic properties of brain tissue to produce two or three dimensional images.

Positron emission tomography (PET)

A functional brain imagining method that uses the brain’s metabolism of substances containing radioactive isotopes to produce ongoing brain images.

Functional magnetic resonance imaging (fMRI)

A functional brain imaging method that uses the brain’s natural metabolism of oxygen to produce ongoing brain images.

Electro-encephalography A method of measuring overall brain electrical activity using electrodes placed on the scalp.

Quantitative Electroencephalography

(QEEG)

A method of assessing brain activity that uses a large array of electrodes in a skull cap to measure and localize minute electrical reactions to areas of the brain.


Chapter 2: The Brain’s Functions I: Experiencing the World

Focus Questions

What brain structures process incoming sensory stimulation?

The specialized area of the cerebral cortex responsible for analyzing and interpreting messages from the sense organs is referred to as the somatosensory cortex.The thalamus is a relay and processing center for incoming sensory messages and outgoing bodily commands. The reticular activation system (RAS) is another sensory processing center; it helps keep the upper parts of the brain in an appropriate state of arousal, attention, and activity

What brain structures initiate and coordinate body movements?The specialized strip on the cerebral cortex that controls body movements and speech is the motor cortex. The cerebellum controls body balance and coordination of complex muscular movements; its two lobes are connected by the pons.


THE BRAIN’S FUNCTIONS I: EXPERIENCING THE WORLD: DEFINITIONS

Somatosensory complex The specialized area of the cerebral cortex responsible for analyzing and interpreting messages from the sense organ.

Thalamus The brain’s relay station for messages to and from the body.

Reticular activating system (RAS)

A network of neural cells in the brain stem that serves as a way station for messages from the sense organs.

Motor cortex The specialized strip on the cerebral cortex that controls body movement.

Cerebellum A brain structure involved in controlling balance and movement.

Pons The brain structure connecting the two hemispheres of the cerebellum.


Chapter 2: The Brain’s Functions II: Overseeing Emotions and Survival

Focus Questions

What brain structures are involved in experiencing emotion?The limbic system, a network of brain structures and pathways, helps regulate emotional behavior.One of these structures the amygdala comes into play in experience of such intense emotions as anger, fear, or joy.A prominent part of the limbic system is the hypothalamus—the brain’s most direct link to the body glands that are active in emotions. The master gland the pituitary gland, is connected to the hypothalamus.The hypothalamus plays a role in maintaining Homeostasis, the state of dynamic equilibrium among physiological processes.The medulla is also responsible for coordinating a number of essential bodily processes, including breathing, heart rate, and digestion.

How are our body functions regulated to keep us alive?The autonomic nervous system (ANS) exercises more or less independent control over the endocrine glands, the heart muscles, and the muscles of the body’s organs and blood vessels. It helps regulate breathing, heart rate, blood pressure and digestion; in times of emergency it works in conjunction with the endocrine glands to mobilize the body’s resources.The endocrine glands influence behavior by secreting hormones into the bloodstream. The most important endocrine glands are the following:

a) The pineal, which affects sleep-waking rhythms and mood.b) The pituitary, which produces hormones that control

growth, cause sexual development at puberty, and regulate other glands.

c) The parathyroid, which maintain a normal state of excitability of the nervous system.

d) The thyroid, which regulates metabolism and affects levels of body activity, temperature, and weight.

e) The adrenals, which secrete the powerful stimulants epinephrine (active in states of emergency or fear) and norepinephrine (active during physical effort or anger).

f) The pancreas, which governs blood sugar level.g) The female ovaries and male testes , which regulate sexual

characteristics and behavior.


THE BRAIN’S FUNCTIONS II: OVERSEEING EMOTIONS AND SURVIVAL: LIMBIC SYSTEM

Limbic System

The Limbic System is a group of brain structures that play a role in emotion, memory, and motivation. For example, electrical stimulation of the amygdala in laboratory animals can provoke fear, anger, and aggression. The hypothalamus regulates hunger, thirst, sleep, body temperature, sexual drive, and other functions.

Homeo-stasis A state of equilibrium, or balance, in the physiological systems within the human body.

Limbic System The set of interconnected structures and pathways in the brain involved with emotion and memory.

Amy-g-dala The part of the limbic system that plays a role in intense positive or negative emotions.

Hypo-thala-musThe portion of the limbic system that serves as a mediator between the brain and the body and helps control metabolism, sleep, hunger, thirst, body temperature, sexual behavior, and emotions.

Pit-u-i-tary Gland The master endocrine gland, which secrets hormones controlling growth and sexual development at puberty and regulating other endocrine glands.


THE BRAIN’S FUNCTIONS II: OVERSEEING EMOTIONS AND SURVIVAL: DEFINITIONS

Endocrine glands Glands that discharge hormones directly into the bloodstream, bringing about a variety of physiological and psychological changes.

Medulla The structure in the brain stem that helps regulates breathing, heartbeat, blood pressure, and digestion.

Autonomic nervous system (ANS)

The neural network connecting the CNS with glands and smooth muscles, involved in maintaining Homeostasis.

Para-sympathetic division of the ANS

A part of the nervous system made up of scattered ganglia near the glands of the muscles of organs. It helps maintain functions such as heartbeat and digestion.

Sympathetic division of the ANS

Long chains of ganglia that extend down the sides of the spinal cord and activate the glands and smooth muscle for “fight” or “flight”


Chapter 2: The Brain’s Functions III: Managing Thought & Memory

Focus Questions

What part of the brain process thoughts and memories?The association cortex which makes up the unspecified areas of the cerebral cortex, is concerned with consciousness—awareness of self and the ability to think about the past and imagine the future.The association areas called frontal lobes play a key role in such human capabilities as solving problems, planning, and relating the past to the present.The hippocampus appears to be essential in transforming new information into semantic and episodic memories, but not procedural memories.

In what ways does the brain grow and develop after birth?

How do the left and right hemispheres differ?The right hemisphere of the brain deals with the left side of the body. The left hemisphere controls the right side of the body and the use of language; in most people, it is the dominant hemisphere.The two hemispheres are in constant communication through the corpus callosum, a thick cable of interconnecting neurons.Experiments with patients whose corpus callosum has been cut—split-brain patients—indicate that the left hemisphere specializes in individual items of information, logic, and reasoning; the right hemisphere specializes in information about from, space, music, and entire patterns and is the intuitive half of the brain.


THE BRAIN’S FUNCTIONS III: MANAGING THOUGHT & MEMORY: DEFINITIONS

Association Cortex Diverse areas of the cortex that contribute to self-awareness and the ability to think about the past and imagine the future.

Frontal lobes The front portions of the brain that play a key role in problem solving and planning.

Hippocampus The part of the brain that transfers information from short-term memory to long-term memory.

Corpus callosum The structure of the brain that connects the right and left hemispheres of the cerebrum and enables these hemispheres to interact


Chapter 2: The Brain-Behavior Link

Focus Questions

What effects do the major neurotransmitters and other biochemicals have on behavior?Anything that alters the amount and effectiveness of neurotransmitters in the brain is likely to profoundly influence thoughts, feelings, and behavior in general.Among the best known neurotransmitters are acetylcholine, involved in PNS activities such as motor functions and also many CNS activities, and glutamate, known to play a role in learning and memory.The catecholamines include norepinephrine (involved in arousal as well as depression) and dopamine (involved in goal-directed motor behaviors and numerous mental and behavioral disorders). Serotonin is also involved in mental and behavioral disorders, including depression.Peptides act like neurotransmitter or like hormones. One important peptide, corticotrophin-release factor (CRF), is secreted by the hypothalamus, stimulates the pituitary, and leads to production of Cortisol by the adrenal glands. Another important group is the endorphins the body’s natural painkillers.

Why can’t the physical processes of the nervous system tell us everything we want to know about behavior?

Just as biological factors affect human behavior, psychological and environmental forces (behavioral factors), in reciprocal fashion, affect biology.

THE BRAIN-BEHAVIOR LINK: DEFINITIONS

Acetylcholine A neurotransmitter involved in motor activity and numerous CNS functions

Glutamate An abundant neurotransmitter known to play a primary role in learning and memory.

Nore-pine-phrine A neurotransmitter involved in arousal and depression.

Dopamine An abundant neurotransmitter involved in goal-related motor behaviors and various mental and behavioral disorders including schizophrenia.

Serotonin A neurotransmitter involved in various mental and behavioral disorders, including depression.

Peptides Essential biochemicals that may function like neurotransmitters or hormones.

Corticotrophin-release factor (CRF)

A neuropeptide secreted by the hypothalamus.

Cortisol The hormone secreted by the adrenal gland during emotional upset of in response to pain.

Endorphins Neuropeptide that serve as natural painkillers.


how the brain governs behavior

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