PSYCH Exam 2
From chapter 3:
Define DNA, chromosomes, genes, natural selection, genotype, phenotype, and alleles
DNA (Deoxyribonucleic acid): A complex molecule containing the genetic information that makes up the chromosomes. It is the blueprint for life, carrying instructions for the development, functioning, growth, and reproduction of all known organisms.
Chromosomes: Thread-like structures made of DNA molecules that contain the genes. Humans typically have 23 pairs of chromosomes (46 total) in most body cells.
Genes: The biochemical units of heredity that make up the chromosomes; a segment of DNA capable of synthesizing a protein. They are specific sequences of nucleotides that code for particular traits or functions.
Natural Selection: The evolutionary process by which heritable traits that best enable organisms to survive and reproduce in particular environments are passed to succeeding generations. "Survival of the fittest."
Genotype: An organism's complete set of genetic instructions, its genetic makeup. This refers to the specific genes an individual possesses.
Phenotype: An organism's observable characteristics or traits, such as its physical characteristics (e.g., eye color, height), behavioral traits, or psychological characteristics. This is the expression of the genotype influenced by environmental factors.
Alleles: Different forms of a gene. For example, a gene for eye color might have an allele for blue eyes and an allele for brown eyes. Individuals inherit two alleles for each gene, one from each parent.
Also define and differentiate genotype and phenotype.
Genotype vs. Phenotype: Genotype is the inherited genetic makeup (the blueprint), while phenotype is the observable expression of those genes, influenced by both genetic and environmental factors (the observable trait).
Describe the (general idea) of evolutionary theory and the role of natural selection.
Evolutionary Theory: Proposed by Charles Darwin, it suggests that species change over time through the process of natural selection. This theory explains the diversity of life on Earth by proposing that all life shares a common ancestor and has diverged over geological timescales.
Role of Natural Selection: Organisms with traits better suited to their environment are more likely to survive, reproduce, and pass those favorable traits to their offspring. Over generations, this leads to an increase in the prevalence of advantageous traits in the population, ultimately leading to adaptation and the formation of new species. Genetic mutations provide the raw material for variation upon which natural selection acts.
Report the number of chromosomes in egg/sperm and in our other bodily cells – know that chromosomes contain DNA
Bodily (somatic) cells: Contain 23 pairs of chromosomes, totaling 46 chromosomes. Each chromosome is composed of tightly coiled DNA.
Egg and Sperm (gametes): Contain half the number of chromosomes, specifically 23 individual chromosomes (not pairs). This ensures that when an egg and sperm fuse during fertilization, the resulting zygote has the correct total of 46 chromosomes.
Identify the structures of a neuron and describe what each does, including:
Cell body (Soma): The neuron's life-support center. It contains the nucleus and other organelles, carrying out metabolic functions to keep the neuron alive and functional. It integrates incoming signals.
Dendrites: Bushy, branching extensions that receive messages from other neurons and conduct them toward the cell body. They are the primary receptive surface of the neuron.
Axon: The neuron extension that passes messages through its branches to other neurons, muscles, or glands. It can be very long.
Myelin sheath: A fatty tissue layer segmentally encasing the axons of some neurons; enables vastly greater transmission speed as neural impulses hop from one node to the next.
What produces the myelin sheath: Glial cells (specifically oligodendrocytes in the CNS and Schwann cells in the PNS).
Axon terminal: The endpoint of an axon, where the axon branches out into numerous fine extensions.
Terminal buttons (or synaptic knobs): Small knobs at the end of the axon terminals that contain synaptic vesicles. They are responsible for transmitting signals across the synapse.
Synaptic vesicles: Sac-like structures within the terminal buttons that store neurotransmitters. When an action potential arrives, these vesicles release neurotransmitters into the synapse.
Synapse: The junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. The tiny gap at this junction is called the synaptic cleft. Neurotransmitters cross this gap to transmit signals.
Describe the electrochemical process by which neurons communicate with one another and the body.
Neural Communication: Neurons communicate through an electrochemical process. Electrical signals (action potentials) travel within a neuron, and chemical signals (neurotransmitters) transmit information between neurons across the synapse.
Steps of the action potential and role of Na+:
Resting potential: The neuron's normal state when not firing, maintained by a slightly negative charge inside the axon membrane (due to the action of the Na+/K+ pump, which pumps out more Na+ ions than it pumps in K+ ions). The membrane is polarized.
Depolarization (Threshold reached): If a neuron receives sufficient excitatory input, the membrane potential reaches a threshold. This triggers the opening of voltage-gated Na+ channels.
Rising phase (Action Potential Firing): Na+ ions rush into the axon, making the inside of the membrane positively charged relative to the outside. This rapid change in voltage is the action potential.
Repolarization: Voltage-gated Na+ channels close, and voltage-gated K+ channels open, allowing K+ ions to rush out of the cell. This restores the negative charge inside the axon.
Hyperpolarization (undershoot): K+ channels close slowly, causing a brief period where the membrane potential becomes even more negative than the resting potential before returning to rest. This is known as the refractory period, during which the neuron cannot fire another action potential.
Role of neurotransmitters in the action potential: Neurotransmitters are chemical messengers released from the terminal buttons of a presynaptic neuron into the synaptic cleft. They bind to receptor sites on the dendrites or cell body of the postsynaptic neuron, causing either excitatory (making it more likely to fire an action potential) or inhibitory (making it less likely to fire) graded potentials. If enough excitatory potentials accumulate and the threshold is reached, an action potential is triggered in the postsynaptic neuron.
Describe the function of these neurotransmitters: dopamine, acetylcholine, norepinephrine, serotonin, GABA, glutamate, and beta-endorphin.
Dopamine (DA): Involved in reward, motivation, pleasure, motor control, and voluntary movement. Dysregulation is linked to Parkinson's disease (low dopamine) and schizophrenia (high dopamine).
Acetylcholine (ACh): Plays a crucial role in muscle contraction (at the neuromuscular junction), learning, memory, and attention. Low levels are associated with Alzheimer's disease.
Norepinephrine (NE) / Noradrenaline: Involved in alertness, arousal, mood regulation, and the "fight-or-flight" response (stress). Low levels are linked to depression.
Serotonin (5-HT): Affects mood, hunger, sleep, and arousal. Imbalances are associated with depression, anxiety, and obsessive-compulsive disorder.
GABA (Gamma-aminobutyric acid): The primary inhibitory neurotransmitter in the brain. It slows down brain activity, reducing anxiety and promoting relaxation. Low levels are linked to anxiety disorders and seizures.
Glutamate: The primary excitatory neurotransmitter in the brain. Involved in learning and memory formation. High levels can lead to overstimulation, potentially causing migraines or seizures.
Beta-endorphin: Natural opioid-like neurotransmitter that reduces pain and promotes feelings of euphoria and well-being. Involved in the body's natural pain relief system.
Describe the function of afferent and efferent nerve fibers in the somatic nervous system.
Somatic Nervous System: Part of the peripheral nervous system responsible for voluntary control of skeletal muscles and conveying sensory information from the body to the brain.
Afferent Nerve Fibers (Sensory Neurons): Carry sensory information (e.g., touch, pain, temperature, pressure) from sensory receptors in the body (skin, muscles, organs) to the central nervous system (brain and spinal cord). They are responsible for sensation.
Efferent Nerve Fibers (Motor Neurons): Carry motor commands from the central nervous system to the skeletal muscles, initiating voluntary movement. They are responsible for movement.
Explain the function of the nervous system subdivisions: central (brain and spinal cord) and peripheral – somatic and autonomic are under (directed by) peripheral. Sympathetic and parasympathetic are under autonomic.
Nervous System: The body's communication network.
Central Nervous System (CNS):
Brain: The control center, responsible for thought, emotion, perception, memory, and movement. It processes sensory information, regulates body functions, and initiates responses.
Spinal Cord: A long, thin, tubular bundle of nervous tissue and support cells that extends from the brain. It transmits signals between the brain and the rest of the body (via peripheral nerves) and controls simple reflexes.
Peripheral Nervous System (PNS): Connects the CNS to the rest of the body, including organs, muscles, and glands. It carries sensory information to the CNS and motor commands from the CNS.
Somatic Nervous System: Controls voluntary movements of skeletal muscles and transmits sensory information to the CNS. (As described above, uses afferent and efferent fibers).
Autonomic Nervous System (ANS): Controls involuntary bodily functions such as heart rate, digestion, respiration, pupil dilation, and glandular activity. It operates largely outside conscious awareness.
Sympathetic Nervous System: Arouses the body, mobilizing its energy in stressful situations (e.g., "fight-or-flight" response). It increases heart rate, dilates pupils, inhibits digestion, and redirects blood flow to muscles.
Parasympathetic Nervous System: Calms the body, conserving its energy, and returning it to a resting state (e.g., "rest-and-digest"). It decreases heart rate, constricts pupils, stimulates digestion, and promotes general relaxation. These two systems often work in opposition to maintain homeostasis.
Identify the general location of major divisions of the brain and state what each is responsible for:
Two cerebral hemispheres: The brain is divided into left and right hemispheres, connected by the corpus callosum.
Left Hemisphere: Typically dominant for language, logic, analytical tasks, and sequential processing.
Right Hemisphere: Typically dominant for spatial reasoning, creativity, facial recognition, emotional processing, and holistic processing.
Forebrain (Prosencephalon): The largest and most complex part of the brain, containing the cerebral cortex, thalamus, hypothalamus, and limbic system. Responsible for higher-level cognitive functions, sensory processing, and regulation of vital functions.
Hindbrain (Rhombencephalon): Located at the base of the brain, containing the cerebellum, pons, and medulla. Responsible for vital bodily functions, balance, coordination, and sleep.
Midbrain (Mesencephalon): Located between the forebrain and hindbrain. Involved in relaying visual and auditory information, motor control, and sleep/wake cycles.
Four lobes of the cerebral cortex:
Frontal Lobe (includes prefrontal cortex): Located at the front of the brain. Involved in executive functions, planning, decision-making, personality, voluntary movement, and speech production (Broca's area). The prefrontal cortex in particular is crucial for working memory, attention, problem-solving, and social behavior.
Temporal Lobe: Located below the frontal and parietal lobes, near the temples. Involved in auditory processing, memory formation, facial recognition, and language comprehension (Wernicke's area).
Parietal Lobe: Located at the top rear of the brain. Processes sensory information such as touch, temperature, pain, and pressure (somatosensory cortex). Involved in spatial awareness and navigation.
Occipital Lobe: Located at the very back of the brain. Primarily responsible for visual processing.
Wernicke’s Area: Located in the left temporal lobe. Crucial for language comprehension. Damage leads to receptive aphasia (difficulty understanding spoken language).
Broca’s Area: Located in the left frontal lobe. Crucial for language production and articulation. Damage leads to expressive aphasia (difficulty producing coherent speech).
Cerebellum: Located at the rear of the brainstem, involved in voluntary movement, balance, coordination, posture, and motor learning. Often called the "little brain."
Thalamus: Located at the top of the brainstem, deep within the brain. It is the brain's sensory control center, relaying all sensory information (except smell) to the appropriate areas of the cerebral cortex for processing. Also involved in sleep and wakefulness.
Hypothalamus: Located below the thalamus. Regulates vital functions such as hunger, thirst, body temperature, sexual behavior, and endocrine system activity (by controlling the pituitary gland). Key for maintaining homeostasis.
Somatosensory Cortex: Located in the parietal lobe, directly behind the motor cortex. Processes bodily sensations such as touch, temperature, pain, and pressure. Different areas of the cortex correspond to different parts of the body, with more sensitive areas (e.g., fingertips, lips) having larger cortical representations.
Right Motor Cortex: Located in the frontal lobe, controls voluntary movements of the left side of the body.
Left Motor Cortex: Located in the frontal lobe, controls voluntary movements of the right side of the body.
Reticular Formation: A nerve network that extends from the spinal cord right up through the thalamus. Filters incoming sensory stimuli and relays important information to other brain areas, playing a crucial role in arousal, sleep, and consciousness.
Subcortical structures: Structures located beneath the cerebral cortex.
Medulla (part of the brainstem): Located at the base of the brainstem, controls essential involuntary life-sustaining functions such as heartbeat, breathing, blood pressure, and digestion.
Pons (part of the brainstem): Located above the medulla. Helps coordinate movements (especially facial expressions and eye movements), sleep, and arousal. Relays information between the cerebellum and the cerebral cortex.
Limbic System: A collection of structures involved in emotion, motivation, memory, and learning.
Amygdala: Two limbic system pea-sized clusters linked to emotion, particularly fear and aggression. Important for processing emotional memories.
Hippocampus: A structure in the limbic system linked to the formation of new explicit memories (facts and events). Its name comes from its seahorse-like shape.
Describe the general principle of brain lateralization (for example, the left side of the motor cortex controls the right side of the body and vice versa).
Brain Lateralization: Refers to the tendency for some neural functions or cognitive processes to be specialized to one side of the brain or the other. While both hemispheres work together, specific functions are often primarily handled by one side.
Contralateral Control: A key aspect of lateralization, particularly for motor and sensory functions. For example, the left cerebral hemisphere (including the left motor cortex) controls the movements and processes sensory input from the right side of the body, and the right cerebral hemisphere (including the right motor cortex) controls the movements and processes sensory input from the left side of the body. This cross-over generally occurs at the level of the brainstem or spinal cord.
Describe the role of the endocrine system in the body.
Endocrine System: The body's "slow" chemical communication system; a set of glands that secrete hormones into the bloodstream.
Hormones: Chemical messengers produced by endocrine glands that travel through the bloodstream and affect other tissues, including the brain. They regulate various bodily processes such as growth, metabolism, mood, reproduction, and stress responses.
Role: Works in parallel with the nervous system to maintain homeostasis and regulate long-term processes. It influences many aspects of behavior and physiology, often slower but with longer-lasting effects than neural communication. Key glands include the pituitary, thyroid, adrenal, pancreas, and gonads.
Define brain plasticity.
Brain Plasticity (Neuroplasticity): The brain's remarkable ability to reorganize itself by forming new neural connections throughout life, or by strengthening or weakening existing ones. This allows the brain to adapt, learn, recover from injury, and develop new skills by constantly modifying its structure and function in response to experience, learning, or damage.
Explain the purpose/function of the fMRI.
fMRI (functional Magnetic Resonance Imaging): A neuroimaging technique that measures brain activity by detecting changes in blood flow. When an area of the brain is more active, it requires more oxygenated blood. The fMRI detects the changes in magnetic properties of oxygen-rich blood, thus showing which brain regions are active during specific mental tasks.
Purpose/Function: To map brain activity in real-time, allowing researchers to study which parts of the brain are involved in various cognitive processes (e.g., thinking, feeling, perceiving), and to diagnose or monitor neurological conditions. It provides both structural and functional information.
From chapter 5:
Distinguish between sensation and perception.
Sensation: The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment. It's the raw physical input from the world interpreted by our senses (e.g., light waves, sound waves, pressure, chemicals).
Perception: The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events. It's how our brain makes sense of the raw sensory data, involving interpretation, selection, and organization of sensations. Sensation is bottom-up (data-driven), while perception is a combination of bottom-up and top-down (knowledge-driven).
Describe how the Ames Room and Muller-Lyer illusions work (generally).
Ames Room Illusion: A distorted room that appears rectangular when viewed from a specific vantage point, designed to trick the brain's reliance on familiar cues for depth and size constancy. People or objects inside appear to change size dramatically as they move from one corner to another. This illusion works because the room is actually trapezoidal, but its design forces the viewer's brain to assume it's a normal rectangular room, leading to misinterpretations of size based on perceived distance.
Muller-Lyer Illusion: An optical illusion consisting of a stylized arrow. When viewers are asked to place a mark on the figure at the midpoint, they invariably place it more towards the "tail" end. The illusion works because the brain misinterprets the lengths of lines based on the presence of inward- or outward-pointing "fins" at the ends, which are processed as depth cues influencing perceived length.
Describe how a sensation becomes a perception, including:
Stimulation of Sense Organ: The initial step where physical energy (e.g., light, sound, chemicals, touch) stimulates a sensory receptor in a specific sense organ (e.g., eye, ear, tongue, skin).
Transduction: The process of converting one form of energy into another. In sensation, it's the conversion of physical stimulus energy (like light waves or sound waves) into neural impulses that the brain can understand.
Specifically where this occurs in vision: In the retina of the eye, photoreceptor cells (rods and cones) transduce light energy into electrical signals.
Bottom-up Processing: Analysis that begins with the sensory receptors and works up to the brain's integration of sensory information. It is data-driven, focusing on the raw features of the stimulus (e.g., recognizing a face by first detecting individual features like eyes, nose, mouth).
Top-down Processing: Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations. It is conceptually driven, using existing knowledge to interpret sensory input (e.g., recognizing a familiar face at a distance based on overall shape and context, even if individual features aren't perfectly clear).
Explain the purpose of retinal cells "rods" and "cones" and cell locations.
Retinal Cells: Photoreceptor cells located in the retina (the light-sensitive inner surface of the eye).
Rods:
Purpose: Detect black, white, and gray; necessary for peripheral and twilight vision when cones don't respond. They are primarily responsible for vision in low light conditions (scotopic vision).
Location: More numerous than cones (about 120 million per eye), primarily found in the periphery of the retina. They are sensitive to dim light but do not discern color or fine detail.
Cones:
Purpose: Function in daylight or well-lit conditions. They detect fine detail and give rise to color sensations (photopic vision).
Location: Less numerous than rods (about 6 million per eye), mostly clustered in the fovea (the central focal point of the retina), which provides sharpest vision. Different types of cones are sensitive to different wavelengths of light (red, green, blue).
Describe the opponent process and trichromatic theories of color vision.
Trichromatic (Young-Helmholtz) Theory: The theory that the retina contains three different color receptors—one most sensitive to red, one to green, one to blue—which, when stimulated in combination, can produce the perception of any color. This theory explains color vision at the level of the cones in the retina.
Opponent-Process Theory: The theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green. This theory explains why we see afterimages and why some color combinations (like "reddish-green") seem impossible. This processing occurs in the ganglion cells of the retina and the neurons in the thalamus. These two theories are not mutually exclusive; color vision typically begins with trichromatic processing in the cones and then shifts to opponent-process processing as signals move to higher levels of the visual system.
Explain these sensory principles: Just noticeable difference, absolute threshold, and difference threshold.
Absolute Threshold: The minimum stimulation needed to detect a particular stimulus 50% of the time. It is the faintest detectable stimulus (e.g., the minimum volume of a sound you can hear, or the dimmest light you can see).
Difference Threshold (Just Noticeable Difference or JND): The minimum difference between two stimuli required for detection 50% of the time. It is the smallest noticeable change in a stimulus (e.g., how much brighter a light needs to be before you notice a change, or how much louder a sound needs to be).
Just Noticeable Difference (JND): Synonymous with the difference threshold. It refers to the smallest detectable change in a stimulus. Ernst Weber's Law states that for an average person to perceive a difference, two stimuli must differ by a constant minimum percentage or proportion, not a constant amount (\Delta I / I = K where \Delta I is the JND, I is the initial stimulus intensity, and K is a constant for a particular sense).
Describe perceptual constancy.
Perceptual Constancy: The ability to perceive objects as unchanging (having consistent shape, size, brightness, color) even as illumination and retinal images change. It allows us to perceive a stable world despite constantly changing sensory input.
Shape Constancy: We perceive the form of familiar objects as constant even while our retinal image of it changes (e.g., a door appears rectangular whether open or closed at an angle).
Size Constancy: We perceive objects as having a constant size, even while their distance from us varies (e.g., a car far away still looks like a full-sized car, not a small toy).
Brightness Constancy (Lightness Constancy): We perceive an object as having a constant lightness even when its illumination varies (e.g., a white shirt still looks white whether it's in bright sunlight or shadow).
Color Constancy: We perceive familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object (e.g., a blue car still looks blue under yellow streetlights).
Give examples of how cultural values, experiences, and expectations shape perceptions.
Cultural Values:
Example: In some cultures, individuals living in "carpenter worlds" (environments with many right angles and straight lines, like Western cities) are more susceptible to illusions like the Muller-Lyer illusion, as their brains are accustomed to interpreting angles as depth cues. People from cultures with fewer such cues may be less affected.
Example: Dietary preferences are shaped by culture; what is considered edible or delicious varies greatly, influencing the perception of taste and smell.
Experiences:
Example: A trained birdwatcher will quickly spot a rare bird in a cluttered environment where a novice would see only trees and leaves. Their experience allows them to organize and interpret visual information more effectively.
Example: Musicians can perceive subtle differences in pitch or rhythm that an untrained ear cannot, due to years of experience.
Expectations:
Example: If you expect to hear a particular word in a conversation, you might "hear" it even if the speaker actually said something slightly different that sounds similar (top-down processing).
Example: The "perceptual set" refers to a mental predisposition to perceive one thing and not another. If you're told to look for a face in an image, you're more likely to see a face, even if it's ambiguous. Context creates expectations that influence how we interpret stimuli.
Explain gestalt principles of perceptual organization, including closure, proximity, continuity, and similarity.
Gestalt Principles: A set of principles describing how humans tend to organize visual information into meaningful wholes (gestalts) rather than just perceiving individual components. "The whole is greater than the sum of its parts."
Closure: We tend to perceive complete figures even when parts of the image are missing. Our brains fill in gaps to create a whole object (e.g., seeing a complete circle even if segments are missing).
Proximity: We tend to group figures that are close to each other. Objects near each other are perceived as belonging together (e.g., rows of dots close together are seen as columns rather than individual dots).
Continuity: We perceive smooth, continuous patterns rather than discontinuous ones. We tend to see lines or shapes that follow a consistent direction as a single unit, even if they are interrupted (e.g., seeing a continuous curve even when it's intersected by another line).
Similarity: We tend to group together figures that are similar to each other in terms of shape, color, size, or orientation (e.g., seeing rows of alternating circles and squares as groups of circles and groups of squares, rather than a single alternating pattern).