Biological Bases of Behavior PDF Unit 1 Bio Psych CED

Biological Bases of Behavior AP Psychology Unit One Learning Target Checklist Explain the relationship between heredity and environment in shaping behavior and mental processes. Differentiate among the subsystems of the human nervous system and their functions. Explain how the structure...

Biological Bases of Behavior AP Psychology Unit One Learning Target Checklist Explain the relationship between heredity and environment in shaping behavior and mental processes. Differentiate among the subsystems of the human nervous system and their functions. Explain how the structures and functions of typical neurons in the central nervous system affect behavior and mental processes. Explain how the basic process of neural transmission is related to behavior and mental processes. Explain how psychoactive drugs affect behavior and mental processes. Explain how the structures and functions of the brain apply to behavior and mental processes. Explain how the sleep/wake cycle affects behavior and mental processes throughout the day and night. Explain how the process of sensation is related to behavior and mental processes. Explain how the structures and functions of the visual sensory system relate to behavior and mental processes. Explain how the structures and functions of the auditory sensory system relate to behavior and mental processes. Explain how the structures and functions of the chemical sensory systems relate to behavior and mental processes. Explain how the structures and functions of the touch sensory system relate to behavior and mental processes. Explain how the structures and functions of the pain sensory system relate to behavior and mental processes. Explain how the structures and functions that maintain balance (vestibular) and body movement (kinesthetic) relate to behavior and mental processes. Interaction of Heredity & Environment Nature vs. Nurture One of the largest and most highly contested debates in psychology is the nature versus nurture issue, arguing which plays a greater role in psychological traits or behaviors - genes and heredity or environment? A favorite topic of psychology students and researchers is serial killers. Evil is fascinating. But are evil people born that way or made that way? Survival of the Fittest Behavior geneticists explore the genetic and environmental roots of human differences. Evolutionary psychologists, however, focus on what makes us alike as humans, primarily by exploring the principles established by Charles Darwin. Natural selection: the principle that inherited traits that better enable an organism to survive and reproduce in a particular environment will (in competition with other trait variations) most likely be passed on to the succeeding generations “Survival of the fittest” ○ Adaptation: the process by which a species becomes fitted to its environment through natural selection ○ Mutation: a random error in gene replication that leads to a change Encouraged the idea of eugenics: practice of selective breeding to create ideal specimens → largely considered outdated and discriminatory In other words, Everything psychological is biological. Twin & Adoption Studies Evolutionary psychologists presume all human behaviors reflect the influence of physical and psychological predispositions that helped human ancestors survive and reproduce. To study this, researchers observe twins. Identical vs. Fraternal Twins Identical or monozygotic twins develop from a single fertilized egg that splits, meaning all the genes are the same. Fraternal or dizygotic twins develop from different eggs that were fertilized simultaneously, so they share the same genes as siblings but are not identical. Twin studies are a favorite of psychologists because they provide the perfect opportunity to test the nature vs. nurture debate. Identical twins raised in the same household should be the same, right? Not always. Just as identical twins separated at birth and raised in different environments often have many similarities. This is a new field of research known as epigenetics, or the study of environmental influences on gene expression that occur without DNA change. The Nervous System The Nervous System The nervous system is the body’s speedy, electrochemical communication network, consisting of all nerve cells and is divided into several smaller systems based on function. Central nervous system (CNS): brain and spinal cord Peripheral nervous system (PNS): sensory and motor neurons that connect to brain and spinal cord ○ Autonomic nervous system: controls involuntary functions such as heartbeat, digestion, breathing, etc. Parasympathetic nervous system → rest and digest; Automatically slows the body down after a stressful event Sympathetic nervous system → fight or flight response; Automatically accelerates heart rate, breathing, dilates pupils, slows down digestion ○ Somatic nervous system: controls voluntary functions Sympathetic Nervous System Parasympathetic Nervous System Pupils dilate; inhibits tear production Pupils constrict; tear production stimulated Heart rate increases Heart rate slows Respiration increases Respiration slows Inhibits digestion Stimulates digestion Bladder relaxes Bladder contracts Release of adrenaline+noradrenaline Stimulates elimination, sexual arousal Activates sweat glands Reduces sweat gland functioning Fight or flight reflex Return to homeostasis Other Parts of the Nervous System Afferent Nerves: sensory neurons Efferent Nerves: motor neurons Interneurons: neurons in the brain and spinal cord that serve as an intermediary between sensory and motor neurons; carry info around the brain for processing. Reflexes → Reflex Arc: automatic responses to stimuli; sensory neurons take info up through spine to the brain → Some reactions occur when sensory neurons reach just the spinal cord. The Neuron & Neural Firing Neurons The nervous system is made up of billions of neurons, or nerve cells. While there are several different types of neurons, their key components are the same: Soma/Cell body: contains nucleus & DNA Dendrites: receives signals from other neurons Axon (covered in Myelin Sheath: insulates & protects axon): carry signals from one end to the other Axon Terminals/Terminal Buttons: send signals to next neuron Other Parts of the Neuron Schwann cells produce myelin for the myelin sheath and the Nodes of Ranvier are the spaces between Schwann cells. Glial cells (glia) are support cells for the nervous system, providing extra protection and nourishment to neurons. If nerve cells are queen bees, glial cells are the worker bees. Neural Communication Neurons transmit messages when stimulated by our senses or by neighboring neurons. Although this process has several steps, it happens in a fraction of a second. 1. When not firing (or at rest), a neuron has a slightly negative charge → resting potential. The ions are aligned or polarized. 2. If stimulation reaches the threshold (minimum stimulation needed to trigger a neural impulse), a neuron will fire. When firing an impulse, a neuron is active and ions are exchanged → action potential. The ions are scrambled or depolarized. a. All-or-Nothing Law/Response: a neuron’s reaction of firing or not firing is not determined by the strength of stimulation, as long as the threshold is met 3. Before a neuron can fire again, the ions need to return to their original position, or repolarized. This brief pause between firings is called the refractory period. 4. Once polarized, the neuron is back to resting potential. Exchanging Energy Communication between neurons is chemical, while communication within a neuron is chemical, so a conversion from electrical energy to chemical and back again has to take place with each message. Axon terminals convert electrical signals to chemical messengers or neurotransmitters. These neurotransmitters are released into the synapse or synaptic gap, a small space between the neurons. Once they reach the dendrites of the next neuron, the neurotransmitters are absorbed and the chemical signal is converted back to an electrical one, which is then carried down the axon. Once the conversion is complete, the neurotransmitters are released by the neurons and travel back across the synapse to be reabsorbed by the axon terminals, in a process called reuptake. Nervous System Disorders Multiple Sclerosis (MS): chronic autoimmune disease in which the immune system mistakenly attacks the myelin sheath Myasthenia Gravis (MG): chronic autoimmune neuromuscular disorder characterized by weakness and rapid fatigue of the voluntary muscles caused by a breakdown in the normal communication between nerves and muscles Excitatory vs. Inhibitory Excitatory neurotransmitters increase the likelihood that the postsynaptic neuron will fire an action potential. They do this by causing depolarization of the postsynaptic membrane, making the inside of the neuron more positive and closer to the threshold for firing an action potential. Inhibitory neurotransmitters decrease the likelihood that the postsynaptic neuron will fire an action potential. They do this by causing hyperpolarization of the postsynaptic membrane, making the inside of the neuron more negative and farther from the threshold for firing an action potential. Neurotransmitter Function Malfunctions Acetylcholine (ACh) Enables muscle action, learning, and Undersupply linked to Alzheimer’s disease memory Oversupply linked to paralysis (Black Widow venom) Dopamine Influences voluntary movement, learning, Undersupply linked to Parkinson’s attention, and emotion Oversupply linked to schizophrenia Serotonin Affects mood, hunger, sleep, and arousal Undersupply linked to depression Norepinephrine Helps control alertness and arousal Undersupply linked to depression Oversupply linked to anxiety/mania GABA Inhibitory neurotransmitter; natural Undersupply linked to seizures, tremors, and tranquilizer involved in calming you down insomnia Glutamate Excitatory neurotransmitter; involved in Undersupply linked to concentration problems memory Oversupply linked to seizures and migraines Endorphins Influence the perception of pain and Undersupply linked to depression pleasure Oversupply can make people anxious/wired Substance P Pain transmission Undersupply linked with pain insensitivity The Endocrine System The endocrine system is the body’s slow chemical communication system, which consists of a series of glands that secrete hormones into the bloodstream. Neurotransmitters are the chemical messengers of the nervous system, and hormones are the chemical messengers of the endocrine system. The nervous system has a quicker reaction, but the sensation quickly fades, while the endocrine has a slower response but lingers longer.  Hormones Release Point(s) Function Adrenaline Adrenal glands Prepare body for emergencies → fight or flight Ghrelin Stomach Feelings of hunger Leptin Fat Cells Feelings of satiety Melatonin Pineal Gland Regulate the sleep/wake cycle Oxytocin Pituitary Gland Facilitate lactation and improve relationships → bonding hormone How do drugs work? Psychoactive drugs primarily work by stimulating, inhibiting, or mimicking neurotransmitter activity. Many drugs work because they either increase/mimic a neurotransmitters action (agonists) or block receptor sites (antagonists). Reuptake inhibitors block the reuptake process, leaving the drug/neurotransmitter in the synaptic gap longer. Mouse Party Altering Consciousness Psychoactive drugs are chemical substances that alter perceptions and moods. While some psychoactive drugs can be used in moderation to help with concentration or pain relief, others can lead to addiction and substance use disorder (a disorder characterized by continued substance craving and use despite significant life disruption and/or physical risk. When is drug use a disorder? Diminished control & social functioning More is needed to get the desired effect It is hazardous to use Types of Drugs Hallucinogens - distort perception ○ Cause false sensory hallucinations, impair memory, feelings of relaxation and/or euphoria ○ Ex. marijuana, mushrooms, LSD, ecstasy/MDMA (also a stimulant) Depressants - reduce neural activity ○ Increase relaxation, decrease mood and arousal ○ Slow down (depress) bodily processes ○ Ex. alcohol, barbiturates, Opiates ○ Decrease feelings of pain ○ Ex. heroin, morphine Stimulants - excite neural activity ○ Increase energy, decrease appetite, brief feelings of euphoria ○ Speed up (stimulate) bodily processes ○ Ex. caffeine, nicotine, cocaine, amphetamines (meth) Drug Type Pleasurable Effects Negative After-Effects Alcohol Depressant Initial high followed by relaxation and Depression, memory loss, organ disinhibition damage, impaired reactions Caffeine Stimulant Increased alertness and wakefulness Anxiety, restlessness, and insomnia in high doses; uncomfortable withdrawal Cocaine Stimulant Rush of euphoria, confidence, energy Cardiovascular stress, suspiciousness, depressive crash Marijuana Mild Enhanced sensation, relief of pain, Impaired learning and memory, (THC) hallucinogen distortion of time, relaxation increased risk of psychological disorders Heroin Depressant Rush of euphoria, relief from pain Depressed physiology, agonizing withdrawal  Addiction is a complex condition characterized by compulsive drug use or behaviors despite harmful consequences. Factors related to addiction: Tolerance: diminished psychoactive effects after repeated use Withdrawal: painful symptoms of the body re-adjusting to the absence of the drug. impact on daily life of substance use physical and psychological dependence The Brain The Brain Stem The oldest part of the brain is the brain stem, found at the base of the skull above the spinal cord, that is responsible for automatic survival functions. Reticular Formation: a nerve network that travels through the brainstem into the thalamus and plays an important role in controlling arousal ○ Reticular activating system: If severed or damaged, you could be in a state of permanent sleep or wakefulness. Medulla: the base of the brainstem that controls breathing and heartbeat ○ If severed or damaged, you’ll most likely die or be on life support. Pons: Connects hindbrain, midbrain, forebrain together; involved in respiration and REM sleep, also serves as a communications and coordination center between the two hemispheres of the brain The Cerebellum “Little brain” Section at the rear of the brain stem Coordinates movement and balance, processes sensory input, judgment of time, and enables nonverbal learning and memory One of the first parts of the brain impacted by alcohol, thus explaining why people stagger and struggle to react quickly when intoxicated. The Thalamus Sensory “switchboard” Located at the top of the brainstem Directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla ○ Receives sensory information from all senses except smell The Limbic System The limbic system is a neural system located below the cerebral hemispheres that is associated with emotions and drives. Amygdala: responsible for survival emotions of fear and aggression Hippocampus: responsible for processing and storing explicit memories of facts and events Hypothalamus: below the thalamus; direct several maintenance behaviors, like eating, drinking, and maintaining optimal body temperature, helps regulate the endocrine system via the pituitary gland, and is linked to emotion and reward Pituitary & Pineal Glands The pituitary gland, or “master gland”, is controlled by the hypothalamus and is responsible for the release of hormones throughout the body by controlling all endocrine glands. The pineal gland produces melatonin, regulating the body’s sleep cycle. The Corpus Callosum Network of fibers connecting the two hemispheres of the brain together, allowing for communication between them Can be severed as a treatment for epilepsy, but has some interesting effects (see split-brain studies) The Cerebral Cortex The cerebral cortex is the intricate fabric of interconnected neural cells covering the cerebral hemispheres that functions as the body’s ultimate control and information-processing center. It plays a key role in memory, attention, perceptual awareness, thinking, speaking, and consciousness, and is organized into lobes based on function: Frontal Parietal Temporal Occipital Frontal Lobe Behind your forehead, largest lobe The prefrontal cortex is a critical region of the brain located at the front part of the frontal lobes. It is involved in a variety of complex behaviors and executive functions: ○ Ability to recognize future consequences ○ Making judgements ○ Planning & decision making ○ Abstract thought ○ Personality Contains Broca’s Area: responsible for controlling muscles that produce speech ○ Broca’s Aphasia: problems with fluency in speech production due to damage Contains motor cortex: sends signals to our body controlling muscle movements. Parietal Lobe Top of the head Receives sensory input for touch sensations (pain, pressure, temperature) and body position Contains somatosensory cortex: specified area of the parietal lobe that takes in sensory input from corresponding body parts Angular gyrus: written language and number processing, spatial recognition, and elements of memory Temporal Lobes Above the ears Includes auditory areas, each receiving input from the opposite ear Assists with memory Auditory cortex: organization and processing of auditory information Contains Wernicke’s Area: responsible for language comprehension ○ Wernicke’s aphasia: problems with meaning of speech due to damage; the syntax and grammar jumbled Occipital Lobes Back of the head, above the cerebellum ○ This is why a hit to the back of your head could make you “see stars” or temporarily blur your vision Receives information from the visual fields of opposite eyes for visual processing (see contralateral control) Visual cortex: organization and processing of visual information Neuroplasticity & Neurogenesis Your brain is not only sculpted by your genes but by your life. Your brain is constantly changing, reorganizing itself for your needs without your awareness. Sometimes the brain has to produce new neurons, a process known as neurogenesis. Neuroplasticity refers to the brain’s ability to change, build, and reorganize after damage or experience. This process is easier for children than it is for adults. The whole “you can’t teach an old dog new tricks” thing. Aphasia: lack of speech production and/or comprehension due to brain damage Viewing the Brain Only in recent years have scientists had the ability to view the brain in an non-invasive and painless way. Prehistoric skulls show evidence of trephination, or drilling holes into the skull to “release evil spirits”. In some cases today, skulls will be drilled into and brain tissue destroyed (lesioned), but that is for the purpose of behavior modification and only as a last resort. Otherwise, research on the brain involves the following techniques: Electroencephalogram (EEG) Magnetoencephalography (MEG) Computed tomography (CT) Positron Emission tomography (PET) Magnetic resonance imaging (MRI) ○ Functional Magnetic Resonance Imaging (fMRI) Name How Does It Work? Example Electroencephalogram (EEG) Electrodes placed on the scalp measure Symptoms of depression and anxiety correlate with increased electrical activity in neurons activity in the right frontal lobe, a brain area associated with behavioral withdrawal and negative emotion Magnetoencephalography A head coil records magnetic fields from the Soldiers with posttraumatic stress disorder (PTSD), compared (MEG) brain’s natural electrical currents with those who do not have PTSD, show stronger magnetic fields in the visual cortex when they view trauma-related images Computed tomography (CT) X-rays of the head generate images that may Children’s brain injuries, shown in CT scans, predict locate brain damage impairments in their intelligence and memory processing Positron emission tomography Tracks where a temporarily radioactive form Monkeys with an anxious temperament have brains that use (PET) of glucose goes while the brain of the person more glucose in regions related to fear, memory, and given it performs a given task expectations of reward and punishment Magnetic resonance imaging People sit or lie down in a chamber that uses People with a history of violence tend to have smaller frontal (MRI) magnetic fields and radio waves to provide a lobes, especially in regions that aid moral judgment and map of brain structure. self-control Functional magnetic Measures blood flow to brain regions by Years after surviving a near plane crash, passengers who viewed resonance imaging (fMRI) comparing continuous MRI scans material related to their trauma showed greater activation in the brain’s fear, memory, and visual centers than when they watched footage related to 9/11 terrorist attacks Split Brain Research Patients with severe epileptic seizures found treatment in the form of the split-brain procedure, where their corpus callosum was cut. It eliminated their seizures, but caused some difficulty in basic tasks as the two hemispheres couldn’t communicate with each other. Split Brain Research (continued) In an early experiment, Gazzaniga asked split-brain patients to stare at a dot as he flashed HE·ART on a screen. Thus, HE appeared in their left visual field (which transmits to the right hemisphere) and ART in the right field (which transmits to the left hemisphere). When he then asked them to say what they had seen, the patients reported that they had seen ART. But when asked to point to the word they had seen, they were startled when their left hand (controlled by the right hemisphere) pointed to HE. Given an opportunity to express itself, each hemisphere indicated what it had seen. The right hemisphere (controlling the left hand) intuitively knew what it could not verbally report. Brain Lateralization The lateralization of brain function is the tendency for some neural functions or cognitive processes to be specialized to one side of the brain or the other. The left hemisphere of the brain controls movements and receives sensory input from the right side of the body, while the right hemisphere controls movements and receives sensory input from the left side of the body → contralateral control. Sleep Consciousness Today’s science explores the biology of consciousness - our subjective awareness of ourselves and our environment. Consciousness offers a reproductive advantage by helping us cope with novel situations, read the emotions of others, and follow through on long-term goals. Cognitive neuroscience is the study of the brain activity linked with cognition, including language, perception, memory, and thinking. Sleep Sleep is a periodic, natural loss of consciousness - as distinct from unconsciousness resulting from a coma, general anesthesia, or hibernation. In other words, even in sleep, you still have some level of awareness, that’s why you don’t roll off the top bunk, the music from your headphones might end up in your dreams, or why that prank of putting a sleeping friend’s hand in warm water works. Why do we sleep? Protection Recuperation Restore/rebuild memory Feeds creative thinking Growth Biological Rhythms Sleep is part of our circadian rhythm - our biological clock that regulates our mood, temperature, and arousal through a 24-hour cycle. As morning approaches, our body temperatures rise and we begin to wake up. Our temperature and arousal peak around midday, then start to dip as we approach dusk. This is why most people prefer to sleep in colder temperatures - it helps you fall asleep faster. Circadian rhythms can be thrown off by a change of time zones (jet lag) or a certain work schedule. They can also vary by age and individual (night owls vs. morning larks). Other biological rhythms include: 90-minute sleep cycles 28-day menstrual cycles Annual → Hibernation/Migration Mating seasons Stages of Sleep About every 90 minus, we cycle through distinct sleep stages: NREM or non- rapid eye movement sleep and REM or rapid eye movement sleep. NREM-1: light sleep, easily awoken → alpha waves ○ Can experience hallucinations (false sensory experiences) and hypnagogic sensations (bizarre experiences such as jerking with a sensation of falling) NREM-2: fully asleep → theta waves with sleep spindles (random short bursts of activity) & k-complexes (random tall bursts of activity) NREM-3: deep sleep → delta waves REM: body relaxed as if paralyzed but brain as active as if it was awake (paradoxical sleep) → beta waves ○ Becomes longer & more frequent as night progresses ○ Vivid dreams occur ○ REM Rebound: If deprived of REM sleep, a person will spend more time in REM the next time they go to sleep. Dreams Dreams are sequences of images, emotions, and thoughts passing through a sleeping person’s mind. Although dreams can occur at any stage of sleep, they are most vivid during REM sleep. Why do we dream? Wish-Fulfillment Information Processing Activation Synthesis Physiological Function Cognition Activation Synthesis Dreams are merely the result of neural activity during sleep, which our brain crafts into a narrative. Developed by Allan Hobson and Robert McCarley. Why dreams sometimes make no sense Memory Consolidation Theory Dreams are the expression of a person's thoughts/experiences, allowing them to convert necessary information into long-term memory. Studies have found that sleep, specifically REM sleep, is essential for memory storage. Sleep Disorders & Experiences Insomnia: recurring problems falling or staying asleep Narcolepsy: a sleep disorder characterized by uncontrollable sleep attacks; sufferer may lapse directly into REM sleep Sleep Apnea: a sleep disorder characterized by temporary cessations of breathing during sleep and repeated momentary awakenings REM Sleep Behavior Disorder: a rare sleep disorder in which the person is not immobilized during REM sleep, physically “acting out” their dream Night Terrors: a sleep disorder characterized by high arousal and an appearance of being terrified; unlike nightmares, night terrors occur during NREM-3 sleep and are not remembered Somnambulism: sleepwalking Sensation Processing Sensation & Perception Sensation is the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment. Perception is the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events. Thresholds In order for a neuron to fire, the threshold to trigger an impulse must be reached. This principle continues with sensation. The absolute threshold is the minimum amount of stimulus energy needed to detect a particular stimulus 50% of the time. The concept of absolute thresholds was studied by Gustav Fechner. Difference Threshold Absolute thresholds deal with detection of one stimulus, while difference thresholds (a.k.a. just noticeable difference) note the minimum difference between two stimuli required for detection 50% of the time. Ernest Weber described this phenomenon with a new principle - Weber’s law. Weber’s law states that, to be perceived as different, two stimuli must differ by a constant percentage rather than a constant amount. Consider playing with light dimmers. How much do you need to move the dimmer switch to see something as darker or lighter than before? Sensory Adaptation Earlier, we stated that if our brain was giving equal attention to all the information it received, we’d go crazy. This is one of the reasons our brain is primed to detect change and ignore constants. Sensory adaptation is diminished sensitivity as a consequence of constant stimulation or exposure. When you know the water is cold, you are hesitant to jump in, but all the adults say the same thing - “you’ll get used to it after a few minutes”. You jump in, are frozen for a moment, and then start to acclimate to the water. Up until now, you have ignored much of your senses because they’ve been exposed to constants, but now that I’m bringing it to your attention (the smell of the room or your perfume, the feeling of the clothes on your skin), you notice it again. Synesthesia Synesthesia is a neurological condition in which stimulation of one sense leads to automatic, involuntary experiences in a second sensory system or cognitive pathway. might experience sounds or see letters or numbers as colors, and/or perceive tastes when hearing certain words Transduction All of our senses receive sensory stimulation, transform that information into neural impulses, and deliver information to the brain. The process of converting one form of energy to another (or, in this case, converting sensory stimulation into neural signals) is called transduction. Transduction of all senses involves three steps : Receiving sensory stimulation, transforming that stimulation into neural Physical World Psychological World impulses, and finally delivering those neural impulses to the brain. Light Brightness The field of psychophysics studies the Sound Volume relationships between the physical characteristics of stimuli and our psychological experience of Pressure Weight them. Sugar Sweet The Eye Light enters the cornea (the eye’s clear, protective layer) and then the pupil (adjustable opening of the eye allowing light to pass through) whose size is determined by the iris (colored ring of muscle tissue). Light is then focused by the lens (transparent structure which changes shape to focus images) on the retina (the light sensitive inner surface of the eye with layers of neurons to convert light into neural impulses). The process of focusing these images is called accommodation. These neural impulses are carried to the brain via the optic nerve. Information Processing in the Eye Rods: retinal receptors that detect black, white, and gray, are sensitive to movement and are necessary for peripheral vision Cones: retinal receptors concentrated near the center of the retina responsible for daylight/color vision Blind Spot: the point at which the optic nerve exits the eye so there is an absence of receptor cells Fovea: the central focal point in the retina, around which the eye’s cones cluster → where visual acuity is greatest Ganglion cells: final output neurons of the retina which collects the electrical messages concerning the visual signal from the two layers of nerve cells preceding it Bipolar cells: transport information from rods and cones to ganglion cells Perfect and Imperfect Vision If you have perfect vision, you will have a perfectly spherical eyeball where all images fall perfectly on the retina. Nearsighted/myopic people (those who see things clearly up close, but struggle with things farther away) will have a longer eyeball while farsighted/hyperopic people (those who can clearly see things from far away but struggle with things up close) will have a taller eyeball. Color Processing This apple is obviously red, right? Of course! But actually, the apple is everything but red, because it rejects the wavelengths we process as red and absorbs the rest. Light waves are colorless but our brain perceives them in color. Color vision is largely a mystery, but we have some theories to explain how we see a world in color. Young-Helmholtz Trichromatic Theory states that the retina contains three different types of color receptors for three basic colors - red, green, and blue - which when stimulated can come together to form every color. ○ Why not yellow? Because when both red and green receptors are stimulated, we see yellow. Opponent Process Theory But why do people blind to red and green often still see yellow? And why does yellow appear to be a pure color and not a mixture of red and green, the way purple is of red and blue? Opponent-process theory states that color vision depends on three sets of opposing retinal processes—red-green, blue-yellow, and white-black. As impulses travel to the visual cortex, some neurons in both the retina and the thalamus are turned “on” by red but turned “off” by green. If exposed to one color for an extended period, the opposite will appear in the afterimage. X Stare at the red circle for 30 seconds. Look at nothing else. After the 30 seconds are up, move your eyes to the X. You should see an afterimage of a red background with a green spot. 88 Light Energy Light travels in waves, and the shape of those waves influences what we see. Light’s wavelength (distance from the peak of one wave to the next) determines the hue (color). The wave’s amplitude (height) determines the intensity (the amount of energy the wave contains) or brightness. The purity of the wave determines how vivid the color appears. Color Blindness About 1 person in 50 is “colorblind.” That person is usually male, because the defect is genetically sex linked. Most people with color-deficient vision are not actually blind to all colors. They simply lack functioning red- or green-sensitive cones, or sometimes both. Their vision—perhaps unknown to them, because their lifelong vision seems normal—is monochromatic (one-color) or dichromatic (two-color) instead of trichromatic, making it impossible to distinguish the red and green. Dogs, too, lack receptors for the wavelengths of red, giving them only limited, dichromatic color vision. Feature Detection Feature detectors are nerve cells in the visual cortex respond to specific features, such as edges, angles, and movement. For humans, we have specialized feature detectors for faces. Damage to these feature detectors or the area of the temporal lobe responsible for facial recognition could lead to prosopagnosia (also known as face blindness or facial agnosia)- a neurological disorder characterized by the inability to recognize faces. Blindsight Blindsight is a condition in which a person can respond to a visual stimulus without consciously experiencing it. This is used to help explain how those without sight can sense objects in their environment. Sound Waves Audition is our sense of hearing. Like light, sound travels in waves. Sound waves are composed of compression and rarefaction of air molecules. The height of the wave, or amplitude, determines the volume of the sound, measured in decibels. The frequency (number of wavelengths that pass a point in a given time) determines the pitch (highness or lowness of tone). The Ear Sound waves are funneled into the auditory canal by the pinna (exterior part of ear). Once in the ear canal, sound waves vibrate the eardrum (tight membrane preceding the middle ear), then the hammer/malleus, anvil/incus, and stirrup/stapes (also known as the ossicles), finally vibrating the oval window of the cochlea (the coiled, bony, fluid-filled tube of the inner ear responsible for transduction of sound). The cochlea is lined with a basilar membrane (a layer of hair cells which convert the sound waves into neural impulses). Neural impulses are carried to the brain via the auditory nerve. Seated above the cochlea but not involved in auditory processing are the semicircular canals - fluid-filled tubes used by the vestibular sense to sense body position. Hearing Loss There are two types of hearing loss or deafness: Sensorineural hearing loss (a.k.a. Nerve deafness): inability to hear due to damage to the cochlea’s receptor cells or to the auditory nerves ○ Can be caused by repeated/prolonged exposure to loud sounds ○ Can be helped by a cochlear implant Conduction hearing loss: inability to hear due to damage to mechanical elements of the ear (parts other than the cochlea) ○ Can be helped by a hearing aid Losing Audition How is our sense of hearing impacted by high frequency sounds? Because high frequency sounds create more movement among hair cells, they overwork the cells and can cause them to decay faster than they would normally. How does hearing change as we age? Hearing has a critical period, meaning that it will decline as we age. Hearing can be protected by avoid continuous loud and/or high-pitched sounds, and can be preserved by the use of hearing aids or cochlear implants. Sound Localization Because we have two ears, sounds that reach one ear faster than the other ear cause us to localize the sound, or determine the direction of the sound’s source. Theories of Hearing Place theory states that the pitch Frequency theory states that the of a sound we hear is due to activation entirety of the basilar membrane of specific hair cells on the basilar vibrates in response to sound, and the membrane (like a piano). speed of the vibration is how we perceive pitch (like a drum). Volley Principle When high frequency sounds are experienced too frequently for a single neuron to adequately process and fire for each sound event, the organ of Corti combines the multiple stimuli into a "volley" in order to process the sounds. The volley principle states that groups of neurons of the auditory system respond to a sound by firing action potentials slightly out of phase with one another so that when combined, a greater frequency of sound can be encoded and sent to the brain to be analyzed. Smell Olfaction, or our sense of smell, is also a chemical sense and works closely with taste through a process called sensory interaction (when one sense influences another). This is why if you plug your nose or have a bad sinus infection and can’t smell, you also lose your sense of taste. Odorants enter the nasal cavity to stimulate 5 million receptors in the olfactory bulb to sense smell, and then it bypasses the thalamus and goes straight to the temporal lobe to be processed. Scientists suspect this is an evolutionary trait, as smell is our first indication that food has spoiled and will likely make us ill if consumed. This could also explain why smell is closely connected to memory; if something made us ill in the past, its smell will be a reminder not to eat it again (taste aversion). Taste Gustation, or our sense of taste, is a chemical sense. There are six identified taste sensations: Sweet - helps us identify sugary foods for energy Sour - helps us identify foods that have gone bad or could make us sick Salty - sodium is essential for physiological functioning Bitter - helps us identify poison or foods that could make us sick Umami (savory) - helps us identify foods high in protein which help grow/repair tissue Oleogustus - carbs/fats for energy, insulation, & cell growth The small bumps on the surface of the tongue are called papillae. They serve as our taste receptors. People who have more than average taste receptors and are more sensitive to taste sensations are known as supertasters. Sensory Interaction Sensory interaction refers to the ability of one sense to influence or interact with another. Two senses that commonly interact with each other are taste and smell. So, the taste of strawberry interacts with its smell and its texture on the tongue to produce flavor. Touch Touch, our tactile sense, is vital to our development and survival. Contact comfort helps us establish bonds with caregivers, and premature babies have a better chance of survival if they are held. The tactile sensations include pain, pressure, touch and temperature, and are processed by our parietal lobe. Phantom Limbs & Endorphins Pain is not merely a physical phenomenon of injured nerves sending impulses to a definable brain or spinal cord area. The brain can also create pain, as it does in phantom limb sensations after a limb amputation. Without normal sensory input, the brain may misinterpret and amplify spontaneous but irrelevant central nervous system activity. As the dreamer may see with eyes closed, so 7 in 10 such people feel pain or movement in nonexistent limbs. As we learned last unit, endorphins serve as natural painkillers, thus preventing pain signals from going to the brain. Gate-Control Theory of Pain Pain tells the body that something has gone wrong, usually resulting from damage to the skin and other tissues. Pain begins at sensory neurons known as nociceptors. Melzak and Wall (1965, 1983) proposed that our spinal cord contains neurological “gates” that either block pain or allow it to be sensed. Gate-control theory states that the spinal cord acts as a buffer between pain and the brain, deciding which signals will pass through; pain is a function of the balance between the information traveling into the spinal cord through large nerve fibers and information traveling into the spinal cord through small nerve fibers. Vestibular vs. Kinetic Senses The vestibular sense monitors the The sense of our individual body head and body position, as well as, our parts’ position and movement is called sense of balance. kinesthetic sense. Receptors in the semicircular Receptors in the muscle tissues canals and vestibular sacs of the and joints ear Works with cerebellum Sensory System Source Receptors Key Brain Areas Vision Light waves striking the eye Rods and cones in the retina Occipital lobes Hearing Sound waves striking the Cochlear hair cells (cilia) in the inner ear Temporal lobes outer ear Touch Pressure, warmth, cold, Receptors (including pain sensitive nociceptors), Somatosensory cortex harmful chemicals mostly in the skin, which detect pressure, warmth, (Parietal Lobe) cold, and pain Taste Chemical molecules in the Basic taste receptors for sweet, sour, salty, bitter, and Frontal temporal lobe mouth umami border Smell Chemical molecules Millions of receptors at top of nasal cavities Olfactory bulb & Temporal breathed in through the nose Lobe Body position— Any change in position of a Kinesthetic sensors in joints, tendons, and muscles Cerebellum & Parietal kinesthesia body part, interacting with Lobe vision Body Movement of fluids in the Hair-like receptors in the ears’ semicircular canals Cerebellum movement— inner ear caused by and vestibular sacs vestibular sense head/body movement  AP Psychology. AP Psychology – AP Students | College Board. (n.d.). https://apstudents.collegeboard.org/courses/ap-ps ychology Myers, David G. and Nathan DeWall. Exploring Citations Psychology. 11th edition. 2019. New York: Worth. Myers, David G. and Nathan DeWall. Psychology. 12th edition. 2018. New York: Worth. Weiten, Wayne. Psychology: Themes and Variations. 10th edition. 2017. Belmont, CA: Wadsworth, Cengage Learning.