Section 1 --- Neurons: The Basic Elements of Behavior
MAIN IDEA QUESTIONS
Why do psychologists study the brain and the nervous system?
What are the basic elements of the nervous system?
How does the nervous system communicate electrical and chemical messages from one part to another?
VOCABULARY
neurons - Nerve cells, the basic elements of the nervous system
dendrite - A cluster of fibers at one end of a neuron that receives messages from other neurons
axon - The part of the neuron that carries messages destined for other neurons
terminal buttons - Small bulges at the end of axons that send messages to other neurons
myelin sheath - A protective coat of fat and protein that wraps around the axon
all-or-none law - The rule that neurons are either on nor off
resting state - The state in which there is a negative electrical charge of about -70 millivolts within a neuron
action potential - An electric nerve impulse that travels through a neuron's axon when it is set off by a "trigger," changing the neuron's charge from negative to positive
mirror neurons - Specialized neurons that fire not only when a person enacts a particular behavior, but also when a person simply observes another individual carrying out the same behavior
synapse - The space between two neurons where the axon of a sending neuron communicates with the dendrites of a receiving neuron by using chemical messages
neurotransmitters - Chemicals that carry messages across the synapse to the dendrite (and sometimes the cell body) of a receiver neuron
excitatory message - A chemical message that makes it more likely that a receiving neuron will fire and an action potential will travel down its axon
inhibitory message - A chemical message that prevents or decreases the likelihood that a receiving neuron will fire
reuptake - The reabsorption of neurotransmitters by a terminal button
STRUCTURE OF THE NEURON
~Messages from the brain which make up any meaningful physical activity, as well as thinking, remembering, and emotions, are passed through specialized cells called neurons. Most neurons communicate with other neurons which regulates behavior. Dendrites are the part of the neuron that detects and receives messages from other neurons, while the axon carries messages away from the cell to other neurons. Terminal buttons are at the end of the long, tubelike axon. These buttons send messages to other neurons. Axon tubes are insulated by a myelin sheath, which is a casing of fat and protein (like links of sausage). More important axons have more myelin sheath (EX: if you touch a hot stove, the axon sending the message to recognize pain is a heavily insulated one).
HOW NEURONS FIRE
~Just like a gun, neurons either fire or they don't - there must be enough force from a trigger for the neuron to fire (all-or-none law). Resting state neurons have more negatively charged ions within it, with more positively charged ions outside of it. When a message arrives at a neuron, gates along the cell membrane briefly allow positively charged ions to rush in at high rates (as many as 100 million per second). When the positive charge reaches a critical level, the "trigger" is pulled, and an electrical impulse (action potential) travels along the axon of the neuron. Axons with smaller diameters carry impulses at 2 mph, while longer and thicker ones can average speeds of 225 mph or greater. Some neurons can fire 1,000 times per second (bright light or sound) - intensity of stimulus determines how much fo a neuron's potential firing rate is reached. There is a variation of impulses (being tickled by a feather vs. someone standing on our toes).
Mirror Neurons
~Mirror neurons fire when a person simply observes another individual carry out a behavior. They may fire when we view someone doing something, helping us predict their goals and what they may do next. Mirror neurons allow us to imitate - and may be at the root of empathy (feelings of concern, compassion, and sympathy for others).
WHERE NEURONS MEET: BRIDGING THE GAP
~A chemical connection bridges the gap, or synapse, between two neurons. Neurons send chemical messages to the dendrites of another neuron. The terminal buttons will release a neurotransmitter (a chemical which carries messages to the dendrites). Messages travel electrically within a neuron, and chemically outside of it. Neurotransmitters can only fit precisely into certain neurons (like a jigsaw puzzle). An excitatory message means the neuron will likely fire an action potential down its axom, while an inhibitory message will do the opposite (prevents or decreases the likelihood of an action potential). If there is an overload of neurotransmitters at the terminal button through a process called reuptake (chemical recycling). Neurons reabsorb the neurotransmitters clogging up the synapse (all of this occurs at lightning speed - several milliseconds). Our understanding of this has allowed for the creation of some anti-depressant drugs - SSRIs or selective serotonin reuptake inhibitors, permit certain neurotransmitters to remain active longer.
NEUROTRANSMITTERS: MULTITALENTED CHEMICAL COURIERS
Section 2 --- The Nervous System and the Endocrine System: Communicating Within the Body
MAIN IDEA QUESTIONS
How are the structures of the nervous system linked?
How does the endocrine system affect behavior?
VOCABULARY
central nervous system (CNS) - The part of the nervous system that includes the brain and spinal cord
spinal cord - A bundle of neurons that leaves the brain and runs down the length of the back and is the main means for transmitting messages between the brain and the body
reflex - An automatic, involuntary response to an incoming stimulus
sensory (afferent) neurons - Neurons that transmit information from the perimeter of the body to the central nervous system
motor (efferent) neurons - Neurons that communicate information from the nervous system to muscles and glands
interneurons - Neurons that connect sensory and motor neurons carrying messages between the two
peripheral nervous system - The part of the nervous system that includes the autonomic and somatic subdivisions; made up of neurons with long axons and dendrites, it branches out from the spinal cord and brain and reaches the extremities of the body
somatic division - The part of the peripheral nervous system that specializes in the control of voluntary movements and the communication of information to and from the sense organs
autonomic division - The part of the peripheral nervous system that controls involuntary movement of the heart, glands, lungs, and other organs
sympathetic division - The part of the autonomic division of the nervous system that acts to prepare the body for action in stressful situations, engaging all the organism's resources to respond to a threat
parasympathetic division - The part of the autonomic division of the nervous system that acts to calm the body after an emergency has ended
evolutionary psychology - The branch of psychology that seeks to identify behavior patterns that are a result of our genetic inheritance from our ancestors
behavioral genetics - The study of the effects of heredity on behavior
endocrine system - A chemical communication network that sends messages throughout the body via the bloodstream
hormones - Chemicals that circulate through the blood and regulate the functioning or growth of the body
pituitary gland - The major component of the endocrine system, or "master gland," which secretes hormones that control growth and other parts of the endocrine system
THE NERVOUS SYSTEM: LINKING NEURONS
Estimates of neural connections within the brain fall in the neighborhood of 10 quadrillion (a 1 followed by 16 zeros).
Central And Peripheral Nervous Systems
The nervous system has two main parts; central nervous system and peripheral nervous system. The central nervous system is composed of the brain and spinal cord (thickness of a pencil which runs down from the brain along the back). It is a communication channel that also controls reflexes. Reflexes involve three neurons; sensory (afferent) neurons, motor (efferent) neurons, and interneurons. Sensory transmits information from the periphery of the body to the brain while motor transmits information from the nervous system to the muscles and glands. Interneurons connect sensory and motor. Injury to the spinal cord can cause quadriplegia (loss of voluntary muscle movement from the neck down) or paraplegia (loss of movement in the lower half of the body). The peripheral nervous system consists of all other parts of the nervous system (excluding brain and spinal cord), reaching the extremities of the body. There are two major divisions; somatic and autonomic. Somatic specializes in voluntary movements (like you reading and writing this) and the autonomic specializes in vital body parts - heart, blood vessels, glands, lungs, and other organs which function involuntary without our awareness.
Activating The Divisions Of The Autonomic Nervous System
The autonomic division is divided into two parts; sympathetic division ("fight or flight" response) and the parasympathetic division (calms the body after an emergency).
THE EVOLUTIONARY FOUNDATIONS OF THE NERVOUS SYSTEM
The spinal cord has developed over millions of years through evolution. The spinal cord today had become hierarchically organized - the newer parts of the brain control the older parts of the nervous system. Researchers who study evolutionary psychology seek to identify how behavior is influenced and produced by our genetic inheritance from our ancestors. These studies show how evolutionary factors have an influence on our everyday behavior. They work in conjunction with scientists studying genetics, biochemistry, and medicine.
Behavioral Genetics
Behavioral genetics studies how behavioral habits are affected by their genetic heritage. There is growing and increasing evidence that cognitive abilities, personality traits, sexual orientation, and psychological disorders are determined to by genetic factors. This branch lies at the heart of the nature v. nurture debate. Furthermore, new research is indicating that genetics influence such diverse behavior as family conflict, schizophrenia, learning disabilities, and general sociability. Much of this discovery is due in large part to understanding the basic structure of the human genome - a "map" of humans total genetic makeup. Some 25,000 genes have been identified, each of which appears in a certain sequence on a chromosome (a rod shaped structure which transmits genetic information across generations.
-Molecular Genetics and Psychological Disorders. Molecular genetics seeks to identify certain genes that are associated with behavior. Molecular geneticists have already found that the risk of developing autism is increased by the presence of a gene related to early brain development, HOXA1, which doubles the likelihood a child will develop the disorder. Questions about the existence of genetic influences on criminality, intelligence, and homosexuality raise considerable emotion and it is unclear what social and political consequences such discoveries would create.
-Behavioral Genetics, Gene Therapy, and Genetic Counseling. The advancement of knowledge in genetics has led to gene therapy and gene counseling. Gene therapy allows scientists to inject into a patient's bloodstream genes which are meant to cure a certain disease. When genes arrive at the site of defective genes, this triggers a production of chemicals which can cure the disease. Genetic counselors help people deal with issues related to inherited disorders. EX: Consulting prospective parents about the potential risks in future pregnancy based on their family history of birth defects and hereditary illnesses.
THE ENDOCRINE SYSTEM: OF CHEMICALS AND GLANDS
The endocrine system is a chemical communication system which sends messages via the bloodstream. Its job is to secrete hormones, which regulate the functioning or growth of the body. It influences, and is influenced by, the functioning of the nervous system. Hormonal neurotransmissions move slower, taking minutes and travel throughout the body like radio waves (as opposed to specific lines like neural messages through neurons). Hormones affect only those cells which are receptive or "tuned" to the appropriate hormonal message. The pituitary gland, found near and regulated by the hypothalamus, is a master gland which controls the functioning of the endocrine system. Hormones secreted by the pituitary glands control growth - very tall and very short people have pituitary gland abnormalities. Different hormones have different purposes; Oxytocin is at the root of many pleasures and satisfactions, EX: Cuddling between species members, mother's urge to nurse newborn offspring, etc. Testosterone in males adds muscle weight and strength.
Section 3 --- The Brain
MAIN IDEA QUESTIONS
How do researchers identify the major parts and functions of the brain?
What are the major parts of the brain, and for what behaviors is each part responsible?
How do the two halves of the brain operate interdependently?
How can an understanding of the nervous system help us find ways to alleviate disease and pain?
VOCABULARY
central core - The "old brain," which controls basic functions such as eating and sleeping and is common to all vertebrates
cerebellum - The part of the brain that controls bodily balance
reticular formation - The part of the brain extending from the medulla through the pons and made up of groups of nerve cells that can immediately activate other parts of the brain to produce general bodily arousal (heightened awareness after a loud noise or filtering out background stimuli while sleeping).
thalamus - The part of the brain located in the middle of the central core that acts primarily to relay information about the senses
hypothalamus - A tiny part of the brain, located beneath the thalamus, that maintains homeostasis (a steady internal environment for the body) and produces and regulates vital behavior, such as eating, drinking, and sexual behavior
limbic system - The part of the brain that controls eating, aggression, and reproduction
cerebral cortex - The "new brain," responsible for the most sophisticated information processing in the brain; contains four lobes
lobes - The four major sections of the cerebral cortex; frontal, parietal, temporal, and occipital
motor area - The part of the cortex that is largely responsible for the body's voluntary movement
sensory area - The site in the brain of the tissue that corresponds to each of the senses, with the degree of sensitivity related to the amount of tissue
association areas - One of the major regions of the cerebral cortex; the site of the higher mental processes, such as thought, language, memory, and speech
neuroplasticity - Changes in the brain that occur throughout the life span relating to the addition of new neurons, new interconnections between neurons, and the reorganization of information-processing areas
neurogenesis - The creation of new neurons
hemispheres - Symmetrical left and right halves of the brain that control the side of the body opposite to their location
lateralization - The dominance of one hemisphere of the brain in specific functions, such as language
biofeedback - A procedure in which a person learns to control through conscious thought internal pysiological processes such as blood pressure, heart and respiration rate, skin temperature, sweating, and the constriction of particular muscles
STUDYING THE BRAIN'S STRUCTURE AND FUNCTIONS: SPYING ON THE BRAIN
Brain-scanning techniques provide a window into the living brain.
1) EEG - records electrical activity in the brain through electrodes placed on the outside of the skull (allows for precise diagnosis of disorders such as epilepsy and learning disabilities.
2) fMRI - produces 3D images of brain structures and activity (allows for improved diagnosis of chronic back pain, nervous system disorders (strokes, multiple sclerosis, and Alzheimer's.
3) PET - show biochemical activity within the brain at a given moment by injecting a radioactive chemical into the bloodstream, ending up in the brain (may be used in cases of memory problems, seeking to identify the presence of tumors)
4) TMS - a strong magnetic field which causes a momentary interruption of electrical activity. These magnetic pulses create temporary virtual cuts in the brain, which can help to treat disorders such as depression and schizophrenia
THE CENTRAL CORE: OUR "OLD BRAIN"
The central core is a part of the brain common with all vertebrates (species with a backbone). It can be traced back 500 million years to primitive nonhuman species. It controls breathing, sleeping, eating, etc. The cerebellum, which controls balance, is the part of the brain affected by alcohol leading to the movement of drunkenness. Consists of; cerebellum, reticular formation, thalamus, hypothalamus.
THE LIMBIC SYSTEM: BEYOND THE CENTRAL CORE
The limbic system includes the amygdala and hippocampus and borders at the top of the central core. It deals with self-preservation, aggression, and reproduction. Injury to the amygdala (which deals with fear and aggression) could cause tame and docile species to become aggressive, while turning aggressive wild animals into obedient ones. (Experimentation in rats has shown that mild electric shocks to the limbic system from en electrode implanted in the brain has produced pleasurable feelings). The hippocampus and limbic system play an important role in memory and learning. The limbic system, dealing with self-preservation, memory, learning, and pleasure, is not unique to humans... it is therefore also known as the "animal" brain because it is found in other humans.
THE CEREBRAL CORTEX: OUR "NEW BRAIN"
This portion of the brain allows you to think, evaluate, and make complex judgments. This is the part of the brain unique to humans. The cerebral cortex has four major sections called 'lobes.' These lobes are; frontal, parietal, temporal, occipital. Three major areas are known; the motor areas, the sensory areas, and the association areas.
The Motor Area Of The Cortex
This area is largely responsible for voluntary movement. It controls everything from the movement of a knee or hip to small, precise movements of facial expressions and finger movements. It can further direct body parts into complex postures, such as the stance of a lineman in football.
The Sensory Area Of The Cortex
This area includes three regions; one that deals with body sensations (touch and pressure), one relating to sight, and a third relating to sound.
The Association Areas Of The Cortex
These are the sites of higher mental processes such as thinking, language, memory, and speech. These areas control executive functions, such as planning, goal setting, judgment, and impulse control. Injury to these areas can produce personality changes, decrease their ability to make moral judgments and process emotions, and cause language problems.
NEUROPLASTICITY AND THE BRAIN
Neuroplasticity is a process in which the brain reorganizes itself. Neurogenesis allows neurons to renew themselves during the adulthood (while it used to be believed that brain cells could not be renewed). Drugs which could be created to trigger the development of new neurons could help combat diseases such as Alzheimer's. The brain adapts and grows according to activities; i.e. if you read Braille, the amount of tissue in your cortex relating to sensation will grow. Another example would be playing the violin, your sensation to your fingertips will grow, but only for those that are moving across the strings of the violin.
Parkinson's disease, tremors and loss of motor control are disorders in which future research of a cure appears promising. When stem cells - immature cells from human fetuses that have the potential to develop into a variety of specialized cell types, depending on where they are implanted - are injected into Parkinson's sufferers, the stimulate dopamine production. When stem cells divide, each newly created cell has the potential to repair damaged cells. As most disease is the result of damaged cells, the revolutionizing of medicine could eb significant. The use of stem cells is controversial due to the fact that they come from aborted fetuses. The issue remains politicized.
THE SPECIALIZATION OF THE HEMISPHERES: TWO BRAINS OR ONE?
The brain is divided into two mirror image halves - or hemispheres - which control motion in (and receive information from) the side of the body opposite their location. When behaviors are lateralized, it means they are more likely to reflect activity in one hemisphere than the other.
LEFT hemisphere - verbal competence (speaking, reading, thinking, reasoning)
RIGHT hemisphere - spatial relationships, recognition of patterns and drawings, music, emotional expression
~Men and women may experience different degrees of lateralization. EX: Language is centered in the left hemisphere in males and is more balanced in females. Culture may also give rise to differences in lateralization. EX: Native speakers of Japanese lateralize vowel sounds in the left hemisphere, while Americans and Europeans handle vowels principally in the right hemisphere.
THE SPLIT BRAIN: EXPLORING THE TWO HEMISPHERES
The corpus callosum connects the left and right hemispheres. When the corpus callosum is cut, split brain patients provide scientists with many research opportunities. EX: Because the right side of the brain corresponds to the language-oriented left side fo the brain, blindfolded patients who touched an object with their right-hand were able to name it, but were not able to with the left hand.
Psychologists have discovered a process called biofeedback in which a person can control - through conscious thought - processes such as blood pressure, heart and respiration rate, skin temperature, etc. This is accomplished when someone is hooked up to electronic sensors that provide continuous feedback relating to the physiological response in question. This procedure has also been successful in controlling emotions.