The Biological Perspective

Chapter 2The Biological PerspectiveWhat is Biological Psychology?Neuroscience science that deals with the structure and functioning of the brain and the neurons, nerves, and nervous tissue that form the nervous system

Biological Psychology or Behavioral Neuroscience branch of neuroscience that focuses on the biological bases of psychological processes, behavior, and learning

How the nervous system works provides information about what is going on inside the body when you engage in a specific behavior, feel an emotion, or have an abstract thought

Overview of the Nervous SystemNervous system a network of cells that carries information to and from all parts of the body (4 levels)Central nervous system (CNS) brain and spinal cordBrain interprets and stores information and sends orders to muscles, glands, and organsSpinal cord pathway connecting the brain and the peripheral nervous systemPeripheral nervous system transmits information to and from the CNSAutonomic nervous system automatically regulates glands, internal organs and blood vessels, pupil dilation, digestion, and blood pressureParasympathetic division maintains body functions under ordinary conditions; saves energySympathetic division prepares the body to react and expend energy in times of stressSomatic nervous system carries sensory information and controls movement of the skeletal muscles

Structure of the Neuron: The Nervous Systems Building BlockNeuron the specialized cell in the nervous system that receives and sends messages within that systemOne of the bodys messengers, therefore it has a very special structure3 main parts of a neuronDendrites branchlike structures that receive messages from other neuronsSoma the cell body of the neuron responsible for maintaining the life of the cellAxon tube-like structure that carries the neural messages out to other cells Structure of the Neuron

AxonDendritesSomaStructure of the NeuronNeurons only make up 10% of cells in the brainOther 90% is glial cellsGlial cells cells that provide structure for the neurons to grow on and around, deliver nutrients to neurons, and produce myelinMyelin fatty substances produced by glial cells that coat the axons of neurons to insulate, protect, and speed up the neural impulse

Structure of the Neuron2 types of glial cells produce myelin for the neurons in the nervous systemOligodendrocytes produce myelin for the neurons in the brain and spinal cord (CNS)Schwann cells produce myelin for the neurons of the body (PNS) Axons travel all over the body like cables, carrying messagesMyelin wraps around the axon forming a protective sheath (myelin sheath)Nerves bundles of axons coated in myelin that travel together through the body

Structure of the NeuronHow do neurons send messages?When a neuron is at rest (not firing an impulse or message) it is actually electrically chargedInside and outside the cell, charged particles called ions are in a semi-liquid (jelly-like) solution The relative charge of ions inside the cell is mostly negativeThe relative charge of ions outside the cell is mostly positive

Structure of the NeuronCell membrane is semipermeable meaning that tiny substances inside and outside the cell can pass through channels in the membrane Inside the cell, there are smaller positively charged potassium ions and larger negatively charged protein ionsNegatively charged protein ions are too big to go through the channels when the cell is at rest, leaving the inside of the cell with a mostly negative chargeOutside the cell, there are lots of positively charged sodium ions and negatively charged chloride ionsUnable to go into the cell when it is at rest because the channels are closed

Structure of the NeuronPositively charged sodium ions cluster around the outside of the cell because the inside of the resting cell is mostly negatively charged and opposite charges attractThis difference in charges creates an electrical potential Resting potential the state of the neuron when not firing a neural impulse

http://www.youtube.com/watch?v=YP_P6bYvEjE

Structure of the NeuronWhen the cell receives a strong enough stimulation from another cell (meaning the dendrites are activated) the channels in the cell membrane open up all down the cell and allow the sodium ions (positively charged) to rush into the cellCauses reversal in electrical charge - the inside of the cell becomes mostly positive and the outside becomes mostly negative (because many of the positive sodium ions are now inside the cell)Sodium ions begin entering the cell through the first channel that opens up, the channel closest to the soma The rest of the ion channels open up all down the axon in a kind of chain reaction Change in electrical charge is called the Action Potential because the electrical potential is now in action, rather than at rest (like in resting potential)

http://www.youtube.com/watch?v=R0TdXkxBOkE&feature=related

Structure of the NeuronDuring action potential, the cell becomes positive inside and negative outsideAfter the action potential passes, the cell has to return back to its resting potential, meaning it has to get the positively charged sodium ions outIon channels close immediately after the action potential passesThen, the cell membrane literally pumps the positive sodium ions outMeanwhile, small positively charged potassium ions inside the neuron move out rapidly helping to restore the negative charge inside the cellhttp://www.youtube.com/watch?v=GTHWig1vOnY Structure of the NeuronTo start an action potential, the neuron must receive a signal strong enough to break the threshold for firingNeurons are receiving Fire! and Dont Fire! messages from other neurons constantly When the Fire! messages are great enough to cancel out the Dont Fire! messages, the threshold is crossed and the neuron firesNeurons fire in a sort of all-or-none fashion, either firing at full strength or not firing at allLike a light switch, when its on, its on and when its off, its off. No dimmer switchSending the Message to Other Cells: The Synapse The end of the axon fans out into several short fibers that have swellings or little knobs on the ends called synaptic knobs or axon terminalsThe synaptic knobs are filled with little saclike structures called synaptic vesiclesSynaptic vesicles are filled with chemical substances called neurotransmitters (the message carriers)

Sending the Message to Other Cells: The Synapse Next to the synaptic knob is the dendrite of another neuron, in between them is a fluid-filled space called the synapse or the synaptic gapRemember, in the synaptic knob are vesicles full of neurotransmittersThe dendrite next to the synaptic knob contains ion channels that have receptor sitesReceptor sites proteins that allow only particular molecules of a certain shape to fit into it

Sending the Message to Other Cells: The Synapse When the action potential reaches the synaptic knob, it causes the vesicles to release their neurotransmitters into the synapse The neurotransmitters float across the synapse and many of them fit themselves into the receptor sitesThis opens the ion channels and allows sodium ions to rush in, activating the next cell The next cell may be another neuron, or a cell on a muscle or glandhttp://www.youtube.com/watch?v=HXx9qlJetSU Sending the Message to Other Cells: The Synapse When neurotransmitters bind to receptor sites they have one of two possible effects (remember the Fire! and Dont Fire! signals?) which depend on what kind of synapse they are release intoExcitatory synapse ion channels open causing the next cell to fireInhibitory synapse ion channels close causing the next neuron to stop firinghttp://www.youtube.com/watch?NR=1&v=LT3VKAr4roo Start a 1:07Neurotransmitters: Messengers of the NetworkAt least 50 100 different types of neurotransmitters in the human bodyAcetylcholine - 1st neurotransmitter to be discoveredExcitatoryCauses muscles to contract Roles in cognition, particularly memoryGABA (Gamma Amino Butyric Acid) Inhibitory Decreases the activity level of neurons in the brain

Neurotransmitters: Messengers of the NetworkSerotonin Both excitatory and inhibitory Linked with sleep, mood, and appetiteDopamine Both excitatory or inhibitoryInvolved in control of movement and sensations of pleasureLow levels have been found to cause Parkinsons diseaseIncreased levels linked to schizophreniaEndorphinsSpecial type of neurotransmitter called a neural regulator Controls the release of other neurotransmitters When endorphins are released in the body, the neurons transmitting information about pain are not able to fire action potentials

Neurotransmitters: Messengers of the NetworkSome chemicals not naturally found in the body can either enhance or block the effects of neurotransmitters on receptor sitesFit into receptor sites on target cells2 types Agonists mimic or enhance the effects of a neurotransmitterAntagonists block or reduce a cells response to the action of a neurotransmitterNeurotransmitters: Messengers of the NetworkAntagonist Example: Acetylcholine neurotransmitter found at the synapses between neurons and muscle cells, causes muscles to contractIf acetylcholine receptor sites on the muscle cells are blocked, then the acetylcholine cant get to the site and the muscle will be incapable of contracting (meaning the muscle is paralyzed)Curare a drug used on poison blow darts is just similar enough to fit into the receptor site without actually stimulating the cellThis blocks acetylcholine from its receptor sites causing paralysis

Neurotransmitters: Messengers of the NetworkAgonist Example: Acetylcholine causes most muscles to contract, but actually slows the contraction of the heart muscleBlack widow spiders venom stimulates the release of excessive amounts of acetylcholine and causes convulsions and possible death

Reuptake and Enzymes After neurotransmitters are released into the synapse they must be taken back into the axon they came from before the next stimulation can occurReuptake process by which neurotransmitters are taken back into the synaptic vesicles However acetylcholine which simulates muscles must be cleared out of the synapse more quickly (no time for the sucking up process)A special enzyme specifically designed to break apart acetylcholine clears the synapse very quickly (called enzymatic degradation)

The Central Nervous System: The Central Processing UnitCNS = brain and spinal cordBrain core of the nervous systemSpinal cord long bundle of neuronsDivided into 2 areas that serve 2 vital functionsOuter area composed mainly of myelinated axons and nervesMessage pipeline - Carries messages from the body up to the brain and from the brain down to the bodyInner area mainly composed of cell bodies separated by glial cellsPrimitive brain responsible for certain reflexes, very fast, lifesaving reflexes

Inside of the spinal cord contains 3 types of neurons that make up the reflex arcAfferent (sensory) neurons carry messages from the senses to the spinal cordEx. If you burn your finger, afferent neurons relay information about the sharp pain in your fingerEfferent (motor) neurons carry messages from the spinal cord to the muscles and glandsEx. Send command to pull your finger back from the painful stimulus Interneurons connect the afferent (sensory) neurons to the efferent (motor) neuronsHelp coordinate signals between sensory neurons and motor neurons

The Central Nervous System: The Central Processing UnitNeuroplasticity the ability of the brain and spinal cord to change in structure and functionCan change the structure and function of many cells in response to experience and trauma Stem cells cells that can become other cells (blood cells, nerve cells, and brain cells)Facilitate neuroplasticity If stem cells can be successfully implanted into damaged areas in the spinal cord, the newly developed neurons may be able to assume the roles that the damaged neurons can no longer performThe Central Nervous System: The Central Processing UnitThe Peripheral Nervous System: Nerves on the EdgePeripheral nervous system (PNS) made up of all the nerves and neurons that are NOT in the brain and spinal cordIncludes all the nerves that connect to your eyes, ears, skin, mouth, and muscles Allows the brain and spinal cord to communicate with these sensory systems Divided into 2 major systems Somantic nervous system controls the senses and voluntary musclesAutonomic nervous system controls organs, glands, and involuntary musclesThe Somantic Nervous System2 partsSensory pathway all the nerves carrying messages from the senses to the CNS (nerves containing afferent neurons)Nerves from the body going to the CNS to relay information

Motor pathway all the nerves carrying messages from the central nervous system to the skeletal muscles of the body (nerves containing efferent neurons)Nerves from the CNS going out to the body telling the body what to do

The Autonomic Nervous System2 systemsSympathetic division turns on the bodys fight-or-flight reactions, including increased heart rate, increased breathing, and dilation of your pupilsfight-or flight systemActive during times of stress

Parasympathetic division controls the body when its in a state of rest to keep the heart beating regularly, to control normal breathing, and to coordinate digestioneat-drink-rest systemActive most of the time

Distant Connections: The Endocrine GlandsSort of the 2nd messenger system in the bodyEndocrine glands have no ducts and secrete chemicals called hormones directly into the blood streamHormones are carried by the blood stream to organs in the bodyCompared to communication between neurons, the hormonal system is slower, and has more widespread effects on the body and behavior

The Pituitary: Master of the Hormonal UniversePituitary Gland master gland, controls or influences all of the other endocrine glandslocated in the brain just below the hypothalamusHypothalamus controls the glandular system by influencing the pituitary gland Secretes the hormones that control milk production and salt levels in the body and growth from infancy to adulthood

The Pineal & Thyroid GlandsPineal glandLocated in the brain, near the back, directly above the brain stemSecretes melatonin hormone that helps track day length and contributes to the regulation of the sleep-wake cycle in humansThyroid glandLocated in the neckSecretes a hormone that regulates metabolism (how fast the body burns its available energy)

The Pancreas & GonadsPancreasControls the level of blood sugar in the body by secreting insulin and glucagonsToo little insulin = diabetes Too much insulin = hypoglycemia

GonadsSex glands, secrete hormones that regulate sexual behavior and reproduction Called ovaries in females Called testes in males

Adrenal Glands2 Adrenal glands - located on the top of each kidneyCritical role in regulating the bodys response to stress Adrenal glands are divided into 2 partsAdrenal medulla releases epinephrine and norepinephrine when people are under stress and aids in sympathetic arousal Adrenal cortex produces over 30 different hormones called corticoidsMost important is cortisol released when the body feels both physical and psychological stress

Looking Inside the Brain: Deep Lesioning How can psychologists find out about what parts of the brain do? In animals deliberately damage a part of the brain then test the animal to see what has happened to its abilitiesDeep lesioning - a thin wire, insulated everywhere except the tip, is surgically inserted into the brain. Then an electrical current strong enough to kill off the target neurons is sent through the tip of the wire In humans study and test people who already have brain damageNot ideal no 2 injuries are exactly the same Brain Stimulation Electrical stimulation of the brain (ESB)Less harmful than lesioning Temporarily disrupt or enhance the formal functioning of specific brain areas through electrical stimulation Invasive techniques deep brain stimulation (DBS)Surgically implant electrodes in specific deep-brain areas which are connected to an impulse generator that is surgically implanted under the collar boneUsed in treatment for Parkinsons disease and seizure disorders Noninvasive techniques repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS)rTMS magnetic pulses are applied to the cortex using special copper wire coils positioned over the headtDCS uses scalp electrodes to pass very low amplitude direct currents to the brain

Mapping Brain StructureComputed Tomography (CT) series of brain x-rays Involves mapping slices of the brain using a computerMagnetic Resonance Imaging (MRI) uses a magnetic field to take pictures of the brain More detail than CT scans

MRI scanCT scanMapping Brain FunctionElectroencephalogram (EEG) provides a record of the electrical activity of groups of neurons just below the surface of the skullFunctional Magnetic Resonance Image (fMRI) uses magnetic fields in the same way as an MRI, but goes a step further and pieces the pictures together to show changes over a short period of timePositron Emission Tomography (PET) involves injecting a person with a low dose of radioactive substance and then recording the activity of that substance in the persons brainSingle Photon Emission Computed Tomography (SPECT) similar to PET but uses somewhat different radiotracer technique

EEGfMRIPETSPECTFrom the Bottom Up: The Structures of the BrainThe brain can be roughly divided into 3 sectionsBrainstem lowest part of the brain that connects to the spinal cordCortex outer wrinkled covering of the brainStructures under the cortex (subcortical structures) includes everything between the brainstem and the cortex

Brainstem4 important structures Medulla controls life-sustaining functions such as heart beat, breathing, and swallowing Pons influences sleep, dreaming, and coordination of movementsReticular formation plays crucial role in attention and arousal, such as attending to certain kinds of information in the environmentCerebellum controls all involuntary, rapid, fine motor movement (ex. People can sit upright in a chair because the cerebellum controls all the little muscles that keep you from falling out of the chair)

Structures Under the CortexLimbic system involved in emotions, motivation, memory, and learningThalamus round structure in the center of the brainHypothalamus just below the front of the thalamus Hippocampus in the temporal lobes on each side of the brainAmygdala near the hippocampus Cingulate cortex in the cortex, right above the corpus callosum in the frontal and parietal lobes

The Limbic SystemThalamus receives input from sensory systems, processes it, and then passes it on to the appropriate areaEvery sensation passes through the thalamus except for smellHypothalamus interacts with the endocrine system to regulate body temperature, thirst, hunger, sleeping, sexual activity, and moodHippocampus critical in the formation of long-term memories and for memories of the locations of objectsAmygdala involved in response to fearCingulate cortex important role in emotion and cognition

The CortexCortex outermost part of the brain (wrinkly part)Made up of tightly packed neurons and is actually only about 1/10 of an inch thickCorticalization refers to the fact that the cortex is wrinkled, allowing a much larger area of cortical cells to exist in the small space inside the skullDivided into right and left sections called cerebral hemispheresCerebral hemispheres communicate with each other through the corpus callosumCorpus callosum thick bank of neurons (axons)

The CortexEach cerebral hemisphere can be roughly divided into 4 sections called lobesOccipital lobesParietal lobesTemporal lobesFrontal lobes

Occipital LobesVisual informationPrimary visual cortex processes visual information from the eyesVisual association cortex helps identify and make sense of the visual information from the eyesExample: a patient who had a tumor in the right occipital lobe area in the visual association cortex could see and even describe objects in physical terms but couldnt identify themDescribed a rose as a red inflorescence with a green tubular projection

Parietal LobesProcess information regarding touch, temperature, body position, and possibly tasteSomatosensory cortex processes information from the skin and internal body receptors for touch, temperature, and body position

Temporal LobesProcess auditory informationPrimary auditory cortex processes auditory information coming in from the earsAuditory association area - helps identify and make sense of the auditory information from the ears

Frontal LobesResponsible for higher mental functions such as planning, personality, and decision making, as well as language and motor movements Motor cortex band of neurons that control the movements of the bodys voluntary muscles by sending commands out to the somatic division of the peripheral nervous systemMirror neurons recent research: neurons that fire while an individual is performing an action as well as when an individual is watching someone else perform that same action

The Association Areas of the CortexAssociation areas made up of neurons in the cortex that are devoted to making connections between the sensory information coming into the brain and stored memories, images, and knowledgeIn other words, help people make sense of incoming sensory input2 important association areasBrocas area left frontal lobeWernickes area left temporal lobe

Association Areas of the CortexBrocas area responsible for speech productionAllows people to speak smoothly and fluently Brocas aphasia - Damage to Brocas area causes a person not to be able to produce the words they want to speakCan understand what others say, but cannot speak fluently http://www.youtube.com/watch?v=1aplTvEQ6ew (teenage stroke)Wernickes area involved in understanding the meaning of wordsWernickes aphasia damage to Wernickes area causes a person to use words that dont make sense and sometimes have trouble making sense of what others sayCan still speak fluently, but will use the wrong words http://www.youtube.com/watch?v=aVhYN7NTIKU (dentist)

Specialization of the Cerebral HemispheresRoger Sperry discovered that the right and left hemispheres are not identicalSplit-brain research cut through the corpus callosum (the communication point between the hemispheres)Right and left hemispheres cannot communicate with each otherThis research has revealed that the right and left hemispheres are lateralized, meaning that they specialize in different thingsLeft HemisphereRight HemisphereControls the right handControls the left handSpoken languageNonverbalWritten languageVisual-spatial perceptionMathematical calculationsMusic and artistic processingLogical thought processesEmotional thought and recognitionAnalysis of detailProcesses the wholeReadingPattern recognitionFacial recognitionLeft hemisphere processes information in a sequence and is good at breaking things down into smaller parts for analysisRight hemisphere processes information all at once and simultaneously, a more global or holistic style of processingApplying Psychology to Everyday LifeAttention-deficit/hyperactivity disorder (ADHD) developmental disorder involving behavioral and cognitive aspects of inattention, impulsivity, and hyperactivityBrain areas involved in ADHD are typically divided:Areas responsible for regulating attention and cognitive controlAreas responsible for alertness and motivationNeuroimaging studies: Cortical areas involved in attention and cognition are found to be smaller in people with ADHDPrefrontal cortex (primarily right side)Basal ganglia (involved in response control)CerebellumCorpus callosum Applying Psychology to Everyday LifeMost problematic aspects of attention and cognition in people with ADHD: Vigilance (being able to watch out for something important)Being able to effectively control ones own cognitive processes such as staying on task, maintaining effort, or engaging in self-controlNew research is examining the possibility that ADHD may have multiple causesEnvironmental factors (such as low-level lead exposure)Genetic influencesThe role of heredity and familial factorsPersonality factors