Chapter 2: Biological Foundations of BehaviorChapter 2: Biological Foundations of Behavior

Michael L. Farris

Psychology 101

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Nervous SystemNervous System

AutonomicAutonomic nervous system - The division of the nervous system that regulates the body’s inner environment (heart rate, blood pressureheart rate, blood pressure, digestion, pupil dilation, and electrical conductance of the skin.) Pgs. 50-51.

AfferentAfferent Nerves: (advance, arrive, approach) carry sensory signals from internal organs TO the CNS (brain and spinal cordTO the CNS (brain and spinal cord). UpUp. p.40.

EfferentEfferent nerves (Exit, Embark, Escape p. 52) carry motor signals away away from the central nervous system TO the skeletal muscles.from the central nervous system TO the skeletal muscles. Down. Down. P.41.

Afferent and efferent nerves are also known as sensory neurons (p. 40).

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The Blood-Brain BarrierThe Blood-Brain Barrier

Blood-Brain BarrierBlood-Brain Barrier: (Pinel, p. 55) The brain is a finely tuned electrochemicalelectrochemical organ whose function can be severely disturbed by the introduction of certain kinds of chemicals.

Fortunately, there is a mechanism that

impedes the passage of many toxic impedes the passage of many toxic substances from the blood into the brainsubstances from the blood into the brain; the blood-brain barrier.

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The Brain StemThe Brain StemBrain StemBrain Stem: The part of the brain on which the

cerebral hemispheres rest; in general, it regulates reflex activities that are criticalcritical for survival (heart heart rate and respirationrate and respiration). The Brain StemBrain Stem (particularly the medulla) regulates basic life basic life functions (heart rate and breathing, and such functions (heart rate and breathing, and such reflexes as swallowing, coughing, and reflexes as swallowing, coughing, and sneezing)sneezing). P. 53.

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Cerebral Hemispheres, Corpus CallosumCerebral Hemispheres, Corpus Callosum The brain is composed of two sides, or hemisphereshemispheres.

Left BrainLeft Brain: Controls languagelanguage, speech, writing, calculation, time sense, rhythm, and the ordering of complex movements.

Right BrainRight Brain: Non-verbal. Controls perceptual skills, visualization, recognition of patterns, faces, and melodies, recognition and expression of emotionemotion, spatial skills, and simple language comprehension.

The left and right hemispheres are joined together by the Corpus Corpus CallosumCallosum, a structure in the middle of the brain that enables hemispheres to share functions and information.

Please see pages 54-54 in your text for more information.

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Case StudiesCase Studies

Studies that focus on a single case or subject. Detailed In-depth Pro: Good source of testable hypothesesGood source of testable hypotheses. Con: not very easy to not very easy to generalizegeneralize to others to others.

Humans differ; be skeptical of any biopsychological theory based on only a few case studies. P.23.

Example: LobotomyLobotomy (1 primate study)

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CNS and Cerebral CortexCNS and Cerebral CortexCentral Nervous System (CNS):Central Nervous System (CNS): The portion of the

nervous system within the skull and spine.

Composed of 2 divisions: BrainBrain and Spinal CordSpinal Cord.

Cerebral CortexCerebral Cortex - The layer of neural tissue covering the cerebral hemispheres of humans and other mammals. Being the Being the OUTEROUTER layer, it is most layer, it is most likely to be damaged by accident or surgerylikely to be damaged by accident or surgery.

Please see pages 47-50 for more information.

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Thinking and LearningThinking and Learning

CerebrumCerebrum - The portion of the brain that sits on the brain stem; in general, it plays a role in complex adaptive processescomplex adaptive processes (like learninglearning, perception, and motivation). P.54.

CognitionCognition - Complex intellectual processes such as thoughtthought, memory, attention, and perceptual processing. p.11.

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Comparative PsychologyComparative Psychology

ComparativeComparative Psychology - The division of Biopsychology that studies the

evolution, genetics, and adaptiveness of behavior, often by using the comparative

method (The study of biological processes by comparison of different comparison of different speciesspecies). P.15.

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ConvolutionsConvolutions

FoldsFolds on the surface of the cerebral hemispheres.

Folds have increasedincreased over time greatly increased the volume of the

cerebral cortex (the outermost layer of cerebral tissue).

More surface area = more capacityMore surface area = more capacity

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DNA, EEG, and EvolutionDNA, EEG, and Evolution

Deoxyribonucleic acid (DNA)Deoxyribonucleic acid (DNA) Double Stranded, coiled molecules of geneticgenetic material. The basic chemical material in chromosomes that carries carries the individual’s genetic codethe individual’s genetic code. (p.72).

Electroencephalograph (EEGEEG) - A measure of the general electrical activity of the brainelectrical activity of the brain, often recorded through the scalp. Pgs. 58-59.

EvolveEvolve - To undergo gradual orderly changegradual orderly change. P.10.

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MyelinMyelin Myelinated Nerves carry signals 200 times FASTER than Myelinated Nerves carry signals 200 times FASTER than

unmyelinated onesunmyelinated ones. (Axons vary in length from 0.04 inches to 1 yardAxons vary in length from 0.04 inches to 1 yard.) The fastest fastest nerve signals travel at over 250 mphover 250 mph. Nerve signals enter a neuron through its dendrites and rush along

the axon. At the far end, called the nerve-ending, the axon has other dendrites that pass the message on to the dendrites of other neurons.

Neurons that have to carry urgent signals over long distances are surrounded by thick insulation to keep the signal strong, in the same way that the cable from a TV aerial to the TV is coated with insulating plastic.

In the case of neurons, the insulation is a the insulation is a myelinmyelin sheathsheath—a series of long, flat cells wrapped around the axon. In people with the crippling disease multiple sclerosismultiple sclerosis, the sheaths break down,

weakening the nerve signals. Pgs. 41-42.

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Natural SelectionNatural Selection Heritable traits that are associated with high rates of traits that are associated with high rates of

survivalsurvival and reproduction are preferentially passed onpassed on to future generations. (No magic here; simply good traits get reproduced.)

For example, fast horses are selected and bred by racehorse breeders, so each succeeding generation gets faster overall. The slow ones don’t get a chance to reproduce and pass on their slower genes. Nature is similar. The slow fish can’t outrun the shark, so doesn’t get to reproduce.

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Nature/Nurture and PNSNature/Nurture and PNS Nature-nurture issueNature-nurture issue - The debate about the relative

contributions of nature (genes)nature (genes) and nurture nurture (experience)(experience) to the behavioral capacities of individuals. Pgs. 72-73.

PPeripheral NNervous SSystem (PNS): The division located outsideoutside the skull and spine. Composed of 2 divisions:

1.1. SomaticSomatic nervous system (SNS) (the part of the PNS that interacts with the externalexternal environment)

2.2. AutonomicAutonomic nervous system (ANS), the part which participates in the regulation of the internalinternal environment. Pgs. 47-49.

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Lobotomy and Spinal CordLobotomy and Spinal Cord

Prefrontal Lobes - The large areas, left and right, at the very front of the brain.

Prefrontal LobotomyPrefrontal Lobotomy - A surgical procedure in which the connections between the prefrontal lobes and the rest of the brain are cut as a treatment for mental illness.

Spinal Cord comprises 2 different areas:

1. Gray Matter (composed largely of cell bodies and unmyelinated interneurons)

2. White Matter (composed largely of myelinatedmyelinated axons.) It is the myelin that gives the white matter It is the myelin that gives the white matter its glossyits glossy whitewhite sheensheen.

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Sympathetic and Parasympathetic Sympathetic and Parasympathetic NervesNerves

Sympathetic nerves stimulateSympathetic nerves stimulate, organize, and mobilize energy resources in threatening situations. Sympathetic changes are indicative of psychological arousalarousal.

ParasympatheticParasympathetic nerves act to conserve energy.

Parasympathetic changes are indicative of psychological relaxationrelaxation (think of a parachute).

Each autonomic target organ receives opposing sympathetic and parasympathetic input, and its activity is thus controlled by relative levels of sympathetic and parasympathetic activity. P.51.

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Brain AnatomyBrain AnatomyEarly brain development: 3 sections form (forebrain,

midbrain, and hindbrain).

Later, these grow into five major different swellings (telencephalon, diencephalons, mesencephalon (midbrain), metencephalon, and myelencephalon).

ENCEPHALON means within the headENCEPHALON means within the head. In humans, the telencephalon (right and left cerebral hemispheres) undergo the greatest growth during development.

The other 4 divisions are often referred to collectively The other 4 divisions are often referred to collectively as the Brain Stemas the Brain Stem, on which the cerebral hemispheres sit. The myelencephalon is often referred to as the medulla.

Again: Brain Stem = myelencephalon, metencephalon, mesencephalon, and

diencephalon. 4 of 5 divisions are in the stem4 of 5 divisions are in the stem.

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Brain and Spine ProtectorsBrain and Spine ProtectorsMeninges, Ventricles, and Cerebrospinal FluidMeninges, Ventricles, and Cerebrospinal Fluid (Pinel p. 53): The brain and spinal cord (the CNS) are the most protected The brain and spinal cord (the CNS) are the most protected organs in the bodyorgans in the body. They are encased in bone and covered by three protective membranes, the meninges.

Also protecting the CNS is cerebrospinalcerebrospinal fluid, which fills the

central canal of the spinal cord and the cerebral ventricles of the brain. It also fills the subarachnoid space, which contains many large blood vessels.

The cerebral ventriclesventricles are the four large internal chambersfour large internal chambers of the brain: 2 lateral ventricles, the third ventricle, and the fourth ventricle. It is believed that the ventricles are often enlarged in people with schizophreniaschizophrenia.

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Neural Conduction and Synaptic TransmissionNeural Conduction and Synaptic Transmission

Neural Conduction=ElectricalNeural Conduction=Electrical (the way a nerve impulse travels along a nerve cell.

Synaptic Transmission=ChemicalSynaptic Transmission=Chemical (the way neurotransmitters travel across the synapse (gap) to communicate with another nerve cell (neuron).

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Neural Conduction/Synaptic TransmissionNeural Conduction/Synaptic TransmissionNerve signals are constantly whizzing from neuron to neuron all

around your body – yet no two neurons ever actually touchno two neurons ever actually touch. Instead, there is a small gapgap between connecting neurons called a synapsesynapse.

When a nerve signal is passed on from one neuron to the next, it is carried across the gap by special chemicals called neurotransmittersneurotransmitters. The chemicals are released by the neuron that is sending the signal.

Droplets of neurotransmitters are stored inside the nerve-ending in tiny sacs called vesiclesvesicles. When a nerve signal arrives at the nerve-ending, the vesicles drift towards the synapse and spill out their contents into the gap. The neurotransmitters flood across the gap and wash up against the other nerve. Inside every nerve ending are sacs of chemical transmitters. These are released into the synapse when the nerve is activated, or “excited”, by a nerve signal. If the adjoining nerve has the right receptors (page 95), the signal will pass on.

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Neural Conduction and Synaptic TransmissionNeural Conduction and Synaptic Transmission The term exocytosisexocytosis (Pinel pages 94-95) refers to the process of

releasing a neurotransmitter. Neurotransmitter Neurotransmitter chemicals work a bit likechemicals work a bit like keys in locks keys in locks. In this

case, the “locks” are special receptor sites in the dendrites of the receiving neuron.

These sites accept only oneone kind of chemical. For the nerve signal to pass on, the neurotransmitter must be the right chemical that fits, or “unlocks”, the receptor site. If the neurotransmitter fits, it changes the chemistry of the receiving nerve’s membrane (skin). This starts off the electrical charges that pass the signal along the length of the neuron.

Because a receptor site responds only to one type of a receptor site responds only to one type of neurotransmitterneurotransmitter, an active nerve will pass on the signal only to neurons that have the right receptors, even though it is linked to many others. Pgs.40,43-44.

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Excitation and InhibitionExcitation and Inhibition

Different types of signals follow different routes through the body.

If every single nerve signal were passed If every single nerve signal were passed on by every single synapse, you would on by every single synapse, you would simply be overwhelmed by nerve signalssimply be overwhelmed by nerve signals. This is why at some synapses the receiving neurons react by passing on the signal, but at others they react by blocking it.

This is called excitationexcitation and inhibitioninhibition.

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NeurotransmittersNeurotransmitters There are more than 4040 different neurotransmitters Noradrenaline helps to control heartbeat and blood flow DopamineDopamine works in the areas of the brain that control

movement and coordinationmovement and coordination (when you’re making a tricky move on a skateboard, your nerve endings are releasing lots of dopamine, a neurotransmitter that helps muscles move more easily).

EndorphinsEndorphins are used by the brain to control paincontrol pain (they are called “endogenous opiates”—literally, opiumlike chemicals that are produced within the body; see page 100 for more information).

Acetylcholine Acetylcholine is involved in making muscles contract When you wake up in the morning, it is because certain

nerves are flooding your brain with the neurotransmitter serotoninserotonin—and any nerve that is receptive gets an alarm call!