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33 Cards in this Set
- Front
- Back
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Neurons
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• Neurons are specialized cells that detect sensory events, relay messages to the brain, and control our muscles
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•Neurons are composed of three major parts:
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–Cell body (soma), controls the synthesis of transmitters and other cell functions
–Dendrites receive information from adjacent neurons –Axons form synapses with other neurons |
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Overview of Neuron Structure
Microphotograph of Interconnected Neurons Action Potential |
• Ions are charged particles that are separated by the axon membrane
–Sodium (NA+): high concentration outside cell –Potassium (K+): high concentration inside cell |
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•The axon membrane is normally negatively charged inside with respect to the outside
–Resting value is about –70 mV; reflects a slight diffusion of potassium ions out of the neuron |
•During an action potential, voltage-gated channels open along the membrane, allowing sodium into the cell (inside is now positive)
•Potassium channels then open to restore the resting membrane potential |
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Action Potential
Neural Communication Microphotograph of Synaptic Connections on a Cell Body Synaptic Function |
•The synapse is a physical gap between an axon terminal and a dendrite
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• Passage of a neural message (“action potential”) to the next neuron requires that a chemical (transmitter) be released into the synapse
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–Transmitter molecules attach to and activate receptors on the dendrite
–Receptor activation induces an electrical event in the dendrite that can cause an action potential in its axon •The process is repeated within the next neuron |
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• Two major divisions of the nervous system
– Central nervous system • Brain • Spinal cord |
– Peripheral nervous system
• Somatic division: controls voluntary muscles • Autonomic division: control of smooth muscle and glands |
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• Brain stem: regulates basic survival mechanisms
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– Medulla: controls breathing and heart rate
– Pons: controls sleep and arousal – Cerebellum: fine motor control |
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Forebrain
• Hypothalamus |
– The hypothalamus regulates eating and temperature and controls the autonomic nervous system
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• Thalamus
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– The thalamus is a key relay center for sensory information en route to the cortex
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• Limbic system
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– Hippocampus: involved in memory
– Amygdala: involved in emotion |
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The Limbic System
Cerebral Cortex – The cerebral cortex is the outer surface of the brain – Human cortex has grooves and bumps that increase the surface area – Cortex forms “lobes” (frontal, parietal, occipital, temporal, and limbic lobes) |
• Each lobe modulates different functions
• In some instances, the functions of the lobes are lateralized – Left hemisphere is specialized for language – Right hemisphere is specialized for spatial tasks and for the expression of emotion |
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Results of Split Brain Research
• Left side of the brain: – seems to control language, writing, logical thought, analysis, and mathematical abilities, – processes information sequentially, – can control speech. |
• Right side of the brain
– controls emotional expression, spatial perception, recognition of faces, patterns, melodies, and emotions, – processes information globally, – cannot control speech. |
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Cortical Lobes
• Occipital: visual cortex • Parietal: somatosensory cortex • Frontal: motor cortex, planning, execution of behavior, processing new memories, aspects of personality. • Temporal: auditory cortex, speech, facial recognition |
• Temporal: auditory cortex, speech, facial recognition
• Association cortex: cortex that is not devoted to a specific sensory/motor function (may be as much as 75% of cortex) |
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Methods of Study:
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• Analysis of deficits shown by persons with naturally-induced brain damage
• Selective inactivation by a drug of the right hemisphere reduces emotional expression • EEG: recording the overall activity of brain • Imaging of the intact brain – PET scans measure blood flow in discrete brain regions • Brain areas that are active have greater blood flow |
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Localization of Function
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• Neurons form circuits in brain that perform functions
– One brain region may be part of multiple circuits (i.e., the thalamus) • Certain functions appear to be lateralized – Speech is usually a function of the left hemisphere • Damage to Broca’s area, a cortical region,results in difficulty in speech. – Spatial functions are mediated by the right hemisphere |
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Language Circuits
Heredity |
• Chromosomes carry the genetic instructions
• Strategies to study the role of heredity – Twin studies: compare the concordance of a trait for identical and for fraternal twins • Identical: share 100% of their genes • Fraternal: share 50% of their genes • Concordance: if one twin has a trait, how often will the other twin have the same trait? – Adoption studies: compare concordance rates for a person with a trait with their biological relatives and their adopted families |
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Genetic Structures
Fraternal vs. Identical Twins Monozygotic vs. Dizygotic Evolutionary Psychology |
• As a product of evolution, our species has acquired psychological mechanisms that may be adaptive
• Psychological mechanisms may confer a selective survival advantage – Dominance motivation: seeking high status – Prosocial behavior: helping others • Caution: an evolved mechanism may not always be adaptive… |
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Sensation
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• Our bodies are organized to detect important stimuli in the outside world
• Sensation refers to the raw outputs of our sensory receptors in response to sensory stimuli • Perception refers to the processes by which our brain organizes and interprets our sensations – Perception is an active process |
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• Sensory stimuli represent different forms of energy
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– Light (vision)
– Heat (tactile) – Pressure (tactile) – Chemical (tactile, olfactory, gustatory) |
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Sensory Thresholds
• Each sensory system has a threshold level (“limen”) of energy that is required to activate receptors |
– Absolute threshold is the smallest amount of energy that can be detected by a sensory system 50% of the time.
– Difference threshold is the smallest difference in sensory energies that can be detected |
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• Sensory thresholds can vary between different people (and are therefore not really “absolute”).
• Sensory thresholds can change within a person over time and as a function of hormone status |
– Our ability to taste foods changes as we get older
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• Signal Detection Theory: absolute thresholds can vary due to:
– An individual’s motivation – rewards and costs. |
– Homeostasis – our daily variation in arousal and other bodily functions.
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Difference Thresholds
• Difference Threshold: The amount of change in a stimulus Refers to the smallest required to produce a Just Noticeable Difference (JND). amount of change required to notice a difference between a stimulus and the next higher or lower stimulus. These amounts vary by type of stimuli. The larger the stimuli, the larger the JND. • Examples of just noticeable differences: |
– Lights – 8%
– Weights – 2% – Tones - .3% |
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Subliminal Perception
• Stimuli that are weak or that are shown for a short period of time (20-40 ms.) are not consciously registered |
– Subliminal perception refers to a presumed influence of non-conscious stimuli on human behavior
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• Subliminal visual stimuli may alter subsequent emotional processing
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– Negative (dangerous or aversive) subliminal stimuli are easier to detect than positive stimuli
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• Repeated exposure to subliminal stimuli can enhance their effects
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Subliminal Persuasion?
• Can we perceive subliminal stimuli? • Yes • Can we be persuaded by them (can they alter our behavior significantly? • No – 1956 false report of subliminal advertising. “Drink Coca-Cola” and “Eat Popcorn” were supposedly presented during a movie and increased sales. It was a hoax, admitted to by an advertising specialist. Attempts to replicate the effect failed. |
Sensory Adaptation
• A key function of our sensory systems is to detect change within the sensory environment – Movement in the periphery of your visual field may signal a food source or may signal danger – A stimulus that rapidly moves across the skin may be a snake, whereas the constant pressure exerted by your socks is not important • Sensory adaptation refers to a reduced sensitivity to a constant sensory stimulus – We do not notice the pressure of our watch or rings – We quickly adapt to persistent odors |
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Anatomy of the Human Eye
Cells of the Retina Human Photoreceptors Retinal Photoreceptors |
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• Photoreceptors are light-sensitive cells found within the retina
– Rods (100 million) are sensitive to light, but not to color – Rods are active under low-light conditions – Cones (6.5 million) are sensitive to color, are not active in low-light conditions, and allow for the perception of fine detail – Rods and cones use different photopigments that react to light in order to generate nerve potentials |
• Photoreceptors and bipolar cells conduct potentials to the ganglion cells, which in turn initiate action potentials that are transmitted to the thalamus and then to the occipital cortex
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Rod and Cone Density
Visual Functions |
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• Eye movements allow the visual field to be shifted across the retina
– Version: both eyes move together – Saccadic movements – Involuntary movements – Pursuit movements – Vergence: the lines of sight for the two eyes converge or diverge. Informs brain of distance to objects. • When we move from light into dark, it takes some time for our eyes to adapt – Rods take longer (30 minutes) than cones (5 minutes) to adapt. |
Color Vision
• Humans can discriminate millions of colors • Trichromatic theory – Eye contains 3 different color sensitive elements • Blue, green, or red elements • Trichromatic theory accounts for color mixing of lights • Opponent-Process (OP) theory – Visual system is organized into red-green, blue-yellow, and black-white units • OP theory can account for negative color afterimages. |
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Negative Color Afterimage
Vision is Hierarchical and Modular |
• Blindsight – subject has knowledge of the visual field but is unaware of the stimuli.
• Motion Agnosia – Subject is unable to experience motion. Life appears as a sequence of still photographs. • Prosopagnosia – subject can no longer recognize faces but vision otherwise normal |
