Chapter 2 notes: Neuroscience
Chapter 2 notes: Neuroscience PSYC 1300
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This 6 page Class Notes was uploaded by anonymous112 on Sunday February 7, 2016. The Class Notes belongs to PSYC 1300 at Southern Methodist University taught by Susan Hornstein in Spring 2016. Since its upload, it has received 19 views. For similar materials see Introduction to Psychology in Psychlogy at Southern Methodist University.
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Date Created: 02/07/16
Chapter 2 notes: The Biology of the Mind Neural and hormonal systems Biology, behavior and mind Phrenology: proposed by Franz Gall, the study of the bumps on the skull and how they could reveal a person’s mental abilities and character traits Reminder of our need for critical thinking and scientific analysis Successful in its idea of localization of function: idea that various brain regions have particular functions Biological perspective: concerned with the links between biology and behavior - Nerve cells conduct electricity and send chemical messages - Specific brain systems serve specific functions - We integrate information processed in different brain systems to construct our experiences - Our adaptive brain is wired by our experiences Biophsychosocial systems: each system is part of an even larger system Neural communication Neurons: a nerve cell, the basic building block of the nervous system Vary, but based on same theme: each consist of cell body Dendrite: a neuron’s branching extensions that receive messages and conduct impulses toward the cell body Axon: the neuron extension that passes messages through its branches to other neurons or to muscles or glands (Dendrites listen, axons speak) Myelin sheath: fatty tissue layer that insulates neurons and speeds their impulses (if myelin sheath degenerates, multiple sclerosis results) Glial cells (glia): nerve cells that support, nourish, and protect neurons, may also play a role in learning, thinking, and memory (more glial cells, more intelligent/complex brain) The neural impulse Action potential: a neural impulse, a brief electrical charge that travels down an axon Ions (electrically charged atoms) are exchanged in neuron’s chemistry-to-electricity process Positive charge outside axons membrane, negative charge inside (resting potential) Axons surface is selectively permeable When a neuron fires, the first section of the axon opens, positively charged ions flood in, depolarization (loss of inside/outside charge difference) causes next axon channel to open, and domino effect occurs Refractory period: a period of inactivity after a neuron has fired (When the neuron pumps the positively charged sodium ions back outside, and then it can fire again) Threshold: the level of stimulation required to trigger a neural impulse (minimum intensity that excitatory signals exceed inhibitory signals) Neuron’s reaction is an all-or-none response: firing or non-firing A strong stimulus can trigger more neurons to fire and fire more often, but does not affect action potential’s strength or speed How neurons communicate Synapse: meeting point between neurons (tiny gap at junction is called synaptic gap or synaptic cleft) Neurotransmitters: chemical messengers that cross the synaptic gaps between neurons, when released they travel across the synapse and bind to receptor sites on the receiving neuron, influencing whether that neuron will generate a neural impulse Reuptake: a neurotransmitter’s reabsorption by the sending neuron (rids of excess neurotransmitters) How neurotransmitters influence us Avetylcholine (ACh): neurotransmitter that plays a role in learning and memory When ACh is released, muscles contract, when ACh is blocked, we are paralyzed Endorphins: natural, opiate-like neurotransmitters linked to pain control and to pleasure - How drugs and other chemicals alter neurotransmission When flooded with opiate drugs, the brain may stop producing its own natural opiates Agonist: a molecule that increases a neurotransmitter’s action Antagonists: a molecule that decreases (inhibits or blocks) a neurotransmitter’s action (e.g. Botox, blocks ACh) Enough like natural neurotransmitters to occupy its receptor site and block its effect, but not similar enough to stimulate the receptor The nervous system: the body’s speedy, electrochemical communication network consisting of all the nerve cells of the peripheral and central nervous systems Central nervous system (CNS): brain and spinal cord (body’s decision maker) Peripheral nervous system (PNS): sensory and motor neurons that connect the central nervous system to the rest of the body Nerves: bundled axons that form neural cables connecting the CNS with muscles, glands, and sense organs Sensory (afferent) neurons: neurons that carry information from body’s tissue and sensory receptors inward to the brain and spinal cord Motor (efferent) neurons: carry instructions from the CNS out to the body’s muscles and glands Interneurons: neurons in the CNS that communicate internally and process information between sensory inputs and motor outputs The peripheral nervous system Two components: somatic and autonomic 1. Somatic nervous system: enables voluntary control of our skeletal muscles 2. Autonomic nervous system (ANS): controls glands and internal organ muscles (e.g. heartbeat, digestion), its sympathetic division arouses, parasympathetic division calms) - Sympathetic nervous system: arouses and expands energy (stress: speeds heartbeat, raises blood pressure, slows digestion, etc.) - Parasympathetic nervous system: conserves energy to calm - Sympathetic and parasympathetic systems work together to maintain homeostasis The central nervous system The brain’s neurons cluster into work groups called neural networks Spinal cord: ascending neural fibers send up sensory information, descending fibers send back motor-control information Reflex: an automatic response to a sensory stimulus The endocrine system: the body’s “slow”” chemical communication system, a set of glands that secrete hormones into the blood stream The endocrine system’s glands secrete hormones: chemical messengers that travel through the bloodstream and affect other tissues Both the endocrine system and the nervous system produce molecules that act as receptors elsewhere Adrenal glands: a pair of endocrine glands that sit above the kidneys and secrete hormones (epinephrine and norepinephrine) that help arouse the body at times of stress Pituitary gland: the endocrine system’s most influential gland, under the influence of the hypothalamus, the pituitary regulates growth and other endocrine glands (e.g. oxytocin) The nervous system directs endocrine secretions, which then affect the nervous system Tools of Discovery and Older Brain Structures The tools of discovery: Having our head examined Lesion: tissues destruction Electroencephalogram (EEG): an amplified recording of the waves of electrical activity sweeping across the brain’s surface, measured by electrodes placed on the scalp PET (positron emission tomography) scan: a visual display of brain activity that detects where a radioactive form of glucose goes while the brain performs a given task, shows “hot spots” in the most active brain areas in response to stimuli MRI (magnetic resonance imaging): uses magnetic fields and radio waves to produce computer-generated images of soft tissue, show brain anatomy fMRI (functional MRI): reveals blood flow, compares successive MRI scans (shows brain function and structure) Older brain structures Brainstem: the oldest part and central core of the brain, beginning where the spinal cord swells as it enters the skull, responsible for automatic survival function Begins where spinal cord swells slightly after entering the skull Medulla: the base of the brainstem, controls heartbeat and breathing Pons: sits above medulla, helps coordinate movements and controls sleep The brainstem is a crossover point, where nerves from each side of the brain connect with the body’s opposite side Thalamus: brain’s sensory control center, located on top of brainstem, directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla Receives messages from all senses except smell (A hub through which traffic passes en route to various destinations) Reticular formation: nerve network that travels through the brainstem into the thalamus and plays an important role in controlling arousal Extends from spinal cord through thalamus Cerebellum: “little brain” at the rear of the brainstem, functions include processing sensory input, coordinating movement output and balance, and enabling nonverbal learning and memory Basal ganglia: deep brain structures involved in motor movements, works with cerebellum Older brain functions occur without any conscious effort, our brain processes most information outside of our awareness Limbic system: neural system located below the cerebral hemispheres, associated with emotions and drives (between oldest and newest brain) Hippocampus: neural center located in the limbic system, helps process explicit memories for storage (people who lose hippocampus lose ability to form new memories of facts or events) - Amygdala: two lima bean-sized neural clusters in the limbic system linked to emotion (role in fear and rage) - Hypothalamus: neural structure lying below the thalamus, directs several maintenance activities, helps govern the endocrine system via the pituitary gland, linked to emotion and reward (influence hunger, thirst, body temperature, help maintain a homeostatic internal state) The Cerebral Cortex and Our Divided Brain Cerebral cortex: intricate fabric of interconnected neural cells covering the cerebral hemispheres, the body’s ultimate control and information-processing center The larger the cortex, the more complex the abilities Structure of the cortex The brain’s left and right hemispheres are filled mainly with axons connecting the cortex to the brain’s other regions Each hemisphere’s cortex is divided into four lobes, separated by prominent fissures, or folds - Frontal lobes: portion of the cerebral cortex lying just behind the forehead, involved in speaking and muscle movements and in making plans and judgments - Parietal lobes: at the top and rear, receives sensory input for touch and body position - Occipital lobes: at the back, includes areas that receive information from the visual fields - Temporal lobes: above the ears, includes the auditory areas, each receiving information primarily from the opposite ear Functions of the cortex Motor functions Stimulating parts of the left or right sides of the cortex caused movements of specific body parts on the opposite side of the body Motor cortex: an area in the rear of the frontal loves that controls voluntary movements - Mapping the motor cortex Brain has no sensory receptors, able to map the motor cortex in awake patients by stimulating different areas and recording responses The body areas that require more precise control (e.g. fingers and mouth) occupy the greatest amount of cortical space - Brain-computer interfaces Cognitive neural prosthetics are being tested for people who have suffered paralysis or amputation If everything psychological is also biological, if every thought is also a neural event, then perhaps microelectrodes could detect thoughts well enough to enable people to control their environment with ever-greater precision Sensory functions Somatosensory cortex: area at the front of the parietal lobes that registers and processes body touch and movement sensations Motor cortex sends messages out to the body, somatosensory cortex receives incoming messages The more sensitive the body region, the larger the somatosensory cortex area devoted to it - Association areas: areas of the cerebral cortex that are not involved in primary motor or sensory functions, rather they are involved in higher mental functions such as learning, remembering, thinking, and speaking Cannot be neatly mapped, when probed electrically, they won’t trigger any observable response The brain is an integrated system, with no dead spots for stray bullets (use all parts of the brain) Prefrontal cortex enables judgment, planning, and processing of new memories (damage can also alter personality and inhibitions—Phineas Gauge) Parietal lobes enable mathematical and spatial reasoning (unusually shaped in Einstein’s brain) Our perception of moving flows not from the movement itself, but rather from our intention and the results we expected Complex mental functions don’t reside in any one place Your memory, language, and attention result from the synchronized activity among distinct brain areas and neural networks *Our mental experiences arise from coordinated brain activity The brain’s plasticity Our brains are sculpted by our genes and by our experiences Plasticity: the brain’s ability to modify itself after damage Brain damage effects: 1. Severed brain and spinal cord neurons usually do not regenerate 2. Some brain functions seem preassigned to specific areas Some neural tissue can reorganize in response to damage Constraint-induced therapy aims to rewire brains and improve the dexterity of a brain-damaged child or even an adult stroke victim, by restraining fully functioning limb, therapists force patients to use the “bad” hand or leg Plasticity explains why deaf people have enhanced peripheral and motion- detection vision Neurogenesis: the brain sometimes attempts to mend itself by producing new brain cells Our divided brain Lateralization: left and right hemispheres look alike, but serve different functions Right hemisphere damage has less visible dramatic effects Splitting the brain Corpus callosum: large band of neural fibers connecting the two brain hemispheres and carrying messages between them Split brain: condition resulting from surgery that isolates the brain’s two hemispheres by cutting the fibers (mainly those of the corpus callosum) connecting them (patients are still normal), leaves them with two separate minds Data by either hemisphere is transmitted to the other across the corpus callosum Right-left differences in the intact brain Left hemisphere: adept at making quick, literal interpretations of language Right hemisphere: - Excels in making inferences - Helps us modulate our speech (make meaning clear) - Orchestrate our self--awareness *Everything psychological is simultaneously biological
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