Biopsychology: Genetics, Neurons, and Brain Structures (Vocabulary Flashcards)
Genetics and Biopsychology
Biopsychology studies the biological mechanisms underlying behavior.
Key focus areas include:
Genetics: how inherited genes affect physiological and psychological traits.
Structure and function of the nervous system.
Interactions between the nervous system and the endocrine system.
Human genetics aims to understand how biological bases influence behaviors, thoughts, and reactions.
Questions explored include:
Why do individuals with the same disease have different outcomes?
Are there genetic components to psychological disorders (e.g., depression)?
How are genetic diseases passed through families?
Charles Darwin linked inheritance to evolution via natural selection.
Theory of Evolution
Natural selection: organisms better suited for their environment survive and reproduce; poorly suited individuals die off.
Characteristics that impact survival and reproduction include:
Traits that protect against predators.
Traits that increase access to food.
Traits that help keep offspring alive.
Quote: "It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is most adaptable to change." — Charles Darwin
Genetic Variation and DNA Basics
Genetic variation: genetic difference between individuals; contributes to a species’ adaptation to its environment.
Fertilization basics:
An egg contains 23 chromosomes and a sperm contains 23 chromosomes; when fertilized, the zygote has 46 chromosomes (23 pairs).
Chromosome: a long strand of genetic information, i.e., DNA.
DNA (Deoxyribonucleic acid): a helix-shaped molecule made of nucleotide base pairs.
Genes: sequences of DNA that control or partially control physical characteristics (traits) such as eye color or hair color.
Alleles: different versions of a gene (e.g., variants that determine hair color).
Example: A gene coding for hair color may have multiple alleles, leading to different hair colors.
Gene–Environment Interactions
Nature and nurture interact like pieces of a complex puzzle.
Interaction models include:
Range of reaction: genes set the boundaries within which our environment operates; environment influences where in that range we fall.
Genetic–environment correlation: genes influence our environment, and the environment influences gene expression.
Epigenetics: study of how gene–environment interactions can lead to different phenotypes from the same genotype.
Neurons & Neurotransmission
Neuron structure and function:
Semi-permeable membrane: allows passage of smaller or non-charged molecules; restricts larger or highly charged molecules.
Dendrites: receive incoming electrical signals; transmit toward the cell body.
Axon: conducts electrical impulses away from the cell body.
Myelin sheath: fatty insulating layer that speeds signal transmission along the axon.
Terminal buttons: at the ends of axons; contain synaptic vesicles storing neurotransmitters.
Synapse: the space between the terminal button of one neuron and the dendrite of another neuron.
Each synaptic vesicle contains approximately ~10{,}000 neurotransmitter molecules.
Resting and active states:
Resting potential: the electrical charge inside the neuron at rest.
General ionic distinction:
More Na⁺ outside the cell; more K⁺ inside the cell.
Overall membrane charge: inside is negatively charged relative to outside (about
ext{inside} \, < \, ext{outside}), commonly around -70\,\text{mV} at rest.
The synapse and neurotransmission:
Neurotransmitters are chemical messengers released by neurons to communicate with other neurons.
Two primary neurotransmitters:
Glutamate: excitatory signal to post-synaptic neurons.
GABA: inhibitory signal to post-synaptic neurons.
Other notable neurotransmitters include:
Acetylcholine: muscle action and memory.
Dopamine: mood, sleep, and learning.
Norepinephrine: heart, intestines, and alertness.
Serotonin: mood and sleep.
Beta-endorphin: pain and pleasure.
Reuptake and neurotransmitter balance:
After release, excess neurotransmitters in the synapse can drift away, be broken down, or be reabsorbed (reuptake) back into the axon terminal.
Reuptake = movement of a neurotransmitter from the synapse back into the originating axon terminal.
Action Potentials and Neural Signaling
Action potential dynamics (simplified):
When the membrane potential reaches the threshold of excitation, an action potential occurs.
Key values:
Resting potential: V_{rest} \approx -70\,\text{mV}
Threshold of excitation: V_{threshold} \approx -55\,\text{mV}
Peak potential: V_{peak} \approx +30\,\text{mV}
Process: Na⁺ channels open; Na⁺ rushes into the cell, making the inside more positive (depolarization).
All-or-none principle: an action potential either occurs fully or not at all; no partial firing.
After-peak processes include repolarization and hyperpolarization to reset the neuron for another potential.
Depolarization vs. hyperpolarization:
Depolarization: membrane potential becomes less negative, increasing likelihood of firing.
Hyperpolarization: membrane potential becomes more negative, decreasing likelihood of firing.
Reuptake and Neurotransmitter Dynamics
Reuptake and clearance:
Following neurotransmitter release, reuptake returns neurotransmitters to the presynaptic terminal.
Other clearance mechanisms include enzymatic breakdown.
Neurotransmitters and Psychopharmacology
Biological perspective on disorders:
Psychological disorders (e.g., depression, schizophrenia) are often associated with imbalances in neurotransmitter systems.
Notable neurotransmitters and roles:
Acetylcholine: muscle action and memory.
Dopamine: mood, sleep, and learning; involved in reward pathways.
Norepinephrine: heart function, alertness, and arousal.
Serotonin: mood and sleep.
Psychotropic medications:
Agonists mimic or enhance the effects of a neurotransmitter.
Antagonists block or impede the normal activity of a neurotransmitter.
Application examples:
Parkinson's disease: typically involves low dopamine; dopamine agonists are used as treatment.
Schizophrenia: often involves excess dopamine activity; many antipsychotics act as dopamine antagonists.
The Nervous System: Overview
Nervous system organization:
Central Nervous System (CNS): brain and spinal cord.
Peripheral Nervous System (PNS): nerves to and from the CNS.
Somatic nervous system: relays sensory and motor information to/from the CNS.
Autonomic nervous system: regulates internal organs and glands; divided into sympathetic and parasympathetic systems.
Homeostasis: the autonomic system complements itself to maintain a stable internal environment.
Autonomic nervous system divisions:
Sympathetic nervous system: mediates stress-related activities and the fight-or-flight response; prepares the body for action by mobilizing energy and increasing sensory readiness.
Parasympathetic nervous system: supports routine, day-to-day operations under relaxed conditions; associated with rest and digestion.
Central Nervous System: The Brain and Spinal Cord
Brain basics:
Comprised of billions of interconnected neurons and glia; bilateral (two-sided).
Interacts across regions; left-right specialization (lateralization).
Basic orientation terms:
Dorsal: toward the top of the brain.
Ventral: toward the bottom.
Anterior: toward the front.
Posterior: toward the back.
Lateral: toward the sides.
Medial: toward the middle.
Spinal cord:
Delivers messages to and from the brain.
Contains reflexes independent of brain input for rapid responses.
Functionally organized into 30 segments, each connected to a body region via the Peripheral Nervous System.
Sensory nerves bring information up to the brain; motor nerves send commands to muscles and organs.
Corpus callosum and hemispheric lateralization:
Corpus callosum connects the left and right hemispheres.
Lateralization: left hemisphere typically controls the right side of the body; right hemisphere controls the left side.
The Brain: Three Main Divisions
Forebrain: largest part; contains:
Cerebral cortex: higher-level processing (consciousness, thought, emotion, language, memory).
Thalamus: sensory relay center.
Hypothalamus: maintains homeostasis (e.g., temperature, appetite, blood pressure).
Pituitary gland: master gland of the endocrine system.
Limbic system: emotion and memory circuitry.
Midbrain: structures involved in movement, arousal, reward, and mood; includes:
Reticular formation: regulates sleep–wake cycle, arousal, alertness, motor activity.
Substantia nigra: dopamine production; movement control; degeneration linked to Parkinson's disease.
Ventral tegmental area (VTA): dopamine production; mood, reward, addiction.
Hindbrain: critical life-support functions; includes:
Medulla: controls breathing, blood pressure, heart rate.
Pons: connects brain and spinal cord; regulates brain activity during sleep.
Cerebellum: balance, coordination, movement; contributes to some types of memory.
These three structures form the brainstem.
Cerebral Cortex and Lobes
Frontal lobe:
Executive functions (planning, organization, judgment, attention, reasoning).
Motor control: Motor Cortex.
Prefrontal Cortex: higher-level cognitive functions and impulse control.
Broca’s area (left hemisphere): language production; damage leads to Broca’s aphasia (nonfluent speech).
Phineas Gage (example): frontal lobe damage led to personality changes and impulsivity, illustrating frontal lobe role in self-control; raises questions about localization of function and generalizability.
Parietal lobe:
Primary somatosensory cortex: processes touch, temperature, pain; somatotopically organized.
Involved in processing various sensory and perceptual information.
Temporal lobe:
Associated with hearing, memory, emotion, and aspects of language.
Auditory Cortex: processes sound.
Wernicke’s area: language comprehension; damage leads to Wernicke’s aphasia (receptive aphasia).
Occipital lobe:
Visual processing; primary visual cortex; retinotopic organization.
Limbic System (emotion and memory):
Amygdala: processes emotions, especially fear; assigns emotional meaning to memories.
Hippocampus: learning and memory, particularly spatial memory.
Hypothalamus: regulates homeostasis and drives (e.g., hunger, thirst, fight/flight).
Thalamus (see above): sensory relay; considered by some as part of limbic system in certain contexts.
Imaging and Recording Techniques
CT (Computerized Tomography) Scan:
Uses X-rays to create brain images; shows structure, not function; can detect tumors.
PET (Positron Emission Tomography) Scan:
Injects mildly radioactive substance to monitor blood flow changes; shows brain activity (function).
MRI (Magnetic Resonance Imaging) and fMRI (Functional MRI):
MRI: uses magnetic fields to image brain structure.
fMRI: measures changes in metabolic activity over time; shows brain function.
EEG (Electroencephalography):
Records electrical activity via scalp electrodes; high temporal resolution to study timing of brain activity.
Cap-based EEG enables precise timing analysis of brain waves.
Connections to Real-World Relevance and Ethics
Genetic information informs understanding of behavior and mental health but also raises ethical considerations about privacy, discrimination, and use of genetic data.
Epigenetics highlights how environment can influence gene expression, underscoring the importance of early-life experiences and social determinants of health.
Neurotransmitter systems underpin many psychiatric disorders and their treatments; pharmacological manipulation (agonists/antagonists) can alleviate symptoms but may also cause side effects and ethical considerations about long-term impacts.
Brain lateralization and localization of function inform clinical approaches to language and motor disorders, as well as educational strategies.
Imaging techniques provide powerful insights into brain structure and function but come with limitations (e.g., CT shows structure, not function; PET involves radiation).
Key Formulas and Numerical References
Resting potential: V_{rest} \approx -70\,\text{mV}
Threshold of excitation: V_{threshold} \approx -55\,\text{mV}
Peak action potential: V_{peak} \approx +30\,\text{mV}
Ionic distribution (qualitative):
More Na⁺ ions outside the neuron than inside.
More K⁺ ions inside the neuron than outside.
Membrane potential dynamics involve depolarization (less negative) and hyperpolarization (more negative) during action potentials.
Summary of Core Concepts
Biopsychology connects genetics, neural structure, neurotransmission, and brain imaging to explain behavior and mental processes.
Genetic variation arises from chromosomal arrangements and alleles; gene–environment interactions shape phenotypes through mechanisms like range of reaction, gene–environment correlation, and epigenetics.
Neurons communicate via electrical signals (action potentials) and chemical signals (neurotransmitters) across synapses; balance between excitatory and inhibitory signals shapes neural network activity.
The nervous system is organized into the CNS and PNS, with the autonomic branch regulating internal states via sympathetic and parasympathetic systems, maintaining homeostasis.
The brain comprises the forebrain, midbrain, and hindbrain, with specialized structures (cortex lobes, limbic system, brainstem) supporting cognition, emotion, memory, movement, and autonomic functions.
Imaging and electrophysiological techniques (CT, PET, MRI/fMRI, EEG) enable study of brain structure, function, and timing, each with strengths and limitations.
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