PSYC 220, WEEK 1 Notes
PSYC 220, WEEK 1 Notes PSYC 220
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This 9 page Class Notes was uploaded by Lynde Wangler on Saturday January 9, 2016. The Class Notes belongs to PSYC 220 at University of North Carolina - Chapel Hill taught by Meghan Jones in Spring 2016. Since its upload, it has received 43 views. For similar materials see Biopsychology in Psychlogy at University of North Carolina - Chapel Hill.
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Date Created: 01/09/16
PSYC 220: WEEK ONE Monday Lecture: Chapter 3 Neuroanatomy and Brain Research Methods Neuron parts: dendrites, axon terminal, myelin sheath, axon, soma (cell body), nucleus Structure of Vertebrate Nervous System o Central Nervous System (CNS): consists of brain & spinal cord o Peripheral Nervous System (PNS): consists of afferent sensory neurons and efferent motor neurons; facilitate communication between CNS and the rest of the body Somatic Nervous System: axons carry information from sensory organs to the CNS and from the CNS to the muscles Autonomic Nervous System: controls innate/unconscious bodily functions; i.e., breathing, digestion, heartbeat, etc. Terminology: o Dorsal(“back” – for humans closer to brain)/Ventral(“belly” – for humans downward or lower) o Anterior(front)/Posterior(back) o Rostral(towards the head)/Caudal(towards the tail) o Planes for Viewing the Brain: Horizontal(side to side), Sagittal(front to back), Coronal(top to bottom) Spinal Cord: (Bell-Magendie Law) o Dorsal root ganglia (collection of sensory neuron cell bodies): Carry sensory information to the CNS o Ventral roots: carry motor information to innervate muscles o Gray matter: center of spinal cord, densely packed cell bodies and dendrites o White matter: outer edge of spinal cord, mostly myelinated axons that carry information from gray matter to the brain and other parts of the spinal cord ***The dorsal roots carry sensory (afferent) information to the brain, while the ventral roots carry motor (efferent) information to command muscle movements. SAME – sensory, afferent, motor, efferent. Peripheral Nervous System (PNS): o Autonomic Nervous System (ANS): controls “automatic” bodily functions by commanding heart, lungs, intestines, and other organs o Divided into Sympathetic and Parasympathetic Nervous Systems: Sympathetic Nervous System: “fight or flight” Prepares body for activity by increasing blood pressure & heart rate and slowing digestion Communicates primarily via neurotransmitter norepinephrine Parasympathetic Nervous System: “rest and digest” Regulates activities including sexual arousal, salivation, urination, & digestion Communicates primarily via neurotransmitter acetylcholine The Vertebrate Brain: o Forebrain: Prosencephalon (“forward-brain”), Diencephalon (“between- brain”), & Telencephalon (“end-brain”) o Midbrain: Mesencephalon (“middle-brain”) o Hindbrain: Rhombencephalon (“parallelogram- brain”) Structures of Fore-, Mid-, and Hindbrain: o Forebrain: thalamus, hypothalamus, cerebral cortex, hippocampus, basal ganglia o Midbrain: tectum, tegmentum, superior colliculus, inferior colliculus, substantia nigra o Hindbrain: medulla, pons, cerebellum Hindbrain: o Medulla: Extension of spinal cord; controls vital bodily functions (breathing, heart rate, coughing/sneezing, salivating) o The Cranial Nerves (V-XII): Allow medulla to control sensations and muscles movements of the head; many parasympathetic outputs o Pons: Anterior and ventral; site of decussation (crossing over) of motor information – axons from each hemisphere of the brain cross to the contralateral side of the spinal cord Cranial Nerves: MEMORIZE I. Olfactory: smell II. Optic: vision III. Oculomotor: control of eye movements; pupil constriction IV. Trochlear: control of eye movements V. Trigeminal: skin sensations from most of the face; control of jaw muscles for chewing and swallowing VI. Abducens: control of eye movements VII. Facial: taste from the anterior 2/3 of the tongue; control of facial expressions; crying; salivation; and dilation of the head’s blood vessels VIII. Statoacoustic: hearing; equilibrium IX. Glossopharyngeal: taste and other sensations from posterior third of the tongue; control of swallowing, salivation, and throat movements during speech X. Vagus : sensations from neck and thorax; control of throat, esophagus, and larynx parasympathetic nerves to stomach, intestines, and other organs XI. Accessory: control of neck and shoulder movements XII. Hypoglossal: control of muscles of the tongue Hindbrain: o Reticular Formation Descending: controls motor areas of spinal cord Ascending: sends output to cerebral cortex Affects arousal and attention o Raphe System: Sends axons to forebrain; regulates attention/readiness (raphe nuclei origin of serotonergic system) o Cerebellum: Important for movement, balance, and coordination; shifting attention from one stimuli to another Many folds (gyri & sulci) (size/proportion) highly conserved across species Midbrain: o Tectum: roof of midbrain o Superior and inferior colliculus: structures important for processing sensory information; inferior colliculus: hearing & superior colliculus: vision o Tegmentum: contains nuclei for cranial nerves; part of reticular formation o Substantia nigra: critical for movement planning and control; lack of dopamine in this region associated with Parkinson’s and Huntington’s diseases Forebrain: o Outermost constitutes the cerebral cortex which is highly involved in processing sensory information and controlling movement of contralateral side of the body o Thalamus: “gateway to the cortex;” all sensory information is relayed through this region with the exception of olfaction o Pituitary gland: releases hormones into the blood stream (signaled by the hypothalamus) o Basal ganglia: caudate nucleus, putamen, and globus pallidus – critical for attention, planned movements, and learning (muscle memory) o Nucleus basalis (basal forebrain): critical for arousal, wakefulness, and attention The Limbic System o Surrounds the brainstem; consists of several structures (olfactory bulb, hypothalamus, hippocampus, amygdala, cingulate gyrus) o Limbic structures are associated with emotion and regulate motivated behaviors (eating, drinking, sexual activity, anxiety, aggression, etc.) The Cerebral Ventricles: o Cerebral Spinal Fluid (CSF) protects the brain from harm by absorbing the impact should the brain be jostled; provides hormones and nutrients to the brain and spinal cord; interconnected system divided (only by name) into regions – lateral ventricle, third ventricle, fourth ventricle, cerebral aqueduct, spinal canal Wednesday Lecture: Neuroanatomy and Research Methods Cerebral Cortex: o Most prominent in mammals; utilized for higher brain functioning and information integration o Divided into two hemispheres connected by anterior commissure and corpus callosum o Differences in size and folding between animals; more folds = greater surface area Organization of the Cerebral Cortex: six layers are divided into perpendicular columns; divisions are based on functions I. Molecular Layer – mostly dendrites and long axons II. External Granular Layer – small pyramidal cells III. Pyramidal Cell Layer – pyramidal cells IV. Internal Granular Layer – small cells; main site for incoming sensory information V. Inner Pyramidal Layer – large pyramidal cells; main source of motor output VI. (a., b.) Multiform Layer – spindle cells Human Cerebral Cortex: o Gyrus: ridges on cortex; hills; pl. gyri o Sulcus: groove on cortex; valley; pl. sulci o Four Lobes: Frontal (planning of movements, recent memory, aspects of emotion), Parietal (body sensations), Temporal (hearing and advanced visual processing), and Occipital (vision) o Precentral gyrus (primary motor cortex); Central Sulcus (divides Frontal and Parietal lobes); Postcentral gyrus (primary somatosensory cortex) Occipital Lobe: striate cortex/ primary visual cortex; heavily involved in visual processing; cortical blindness – people with this affliction have impaired visual cortices but intact visual structures so they can sense and detect visual stimuli to an extent but cannot perceive it; when asked to move out of the way when a ball is thrown at them, they are able to complete the task; also activated by visual imagery Parietal Lobe: postcentral gyrus (primary somatosensory cortex); spatial information; integration of information from eyes and head; contains cortical map of the body (homunculus – explains foot fetishes) Temporal Lobe: contains primary auditory cortex; language processing/production; damage can cause Kluver-Bucy Syndrome, which turns people into assholes – most common symptoms in humans include hyper orality, dietary changes, apathy or placidity, and may also cause agnosia and/or other memory disorders Frontal Lobe: precentral gyrus (primary motor cortex); prolific dendritic branching to facilitate integration of information; Phineas Gage – railway construction worker who had a pipe blasted through his frontal lobe causing severe damage and ultimately a changed personality negative effects (he became an asshole) Prefrontal Lobotomy: removal of parts of the brain that connect prefrontal cortex to the remainder of the brain; used as a treatment for seizures and schizophrenia with very poor results The Binding Problem o How do visual, auditory, and other parts of the brain operate to form a single perception of an object? Maybe: the brain binds activities in areas when there is synchronous waves of neuron activity; “neurons that fire together, wire together” For binding to occur, a person must perceive two sensations happening at the same time and same place (more information and examples in the book) Brain Research Methods: Examine the effects of brain damage Examine the effects of stimulating a brain region Record brain activity Examine the relationship between neuroanatomy and human behavior Brain Damage: o Natural damage – damage or impairment might occur as result of an accident; not always reliable as much of the time, many areas are damaged simultaneously and so it is hard to study the effects of one not in conjunction with the other o Ablation: surgical removal of parts of the brain (archaic/crude method) o Lesions: destroying neurons in a specific area to study the effects – there are now much more sophisticated ways of suppressing activity in very specific neurons (stimulation, GABA, optogenetics, etc.) o Transcranial Magnetic Stimulation (TMS) – application of strong magnetic field to portion of scalp to suppress neuronal activity below the magnet; important to include controls (study active vs. inactive minds) Gene Knock-out Approach: biochemical in nature; manipulates a gene of interest; can inactivate certain neurotransmitters or neuropeptide systems for a given phenotype or behavior Brain Stimulation: o Electrical Stimulation – activates neurons in targeted region o Optogenetics – insertion of a light-activated proteins called opsin (can be achieved with an injection of a virus) to activate or silence particular neurons in the brain with a beam of light (laser will either depolarize or hyperpolarize the cells) o DREADD (Designer Receptors Exclusively Activated by Designer Drugs) – gene manipulation is used to express muscarinic receptors (which would normally be activated by Acetylcholine) that are now activated by Clozapine-N-Oxide; not as specifically localized as optogenetics but can use G-proteins to hyperpolarize and depolarize a neuron (to activate or inhibit an action potential); slower but longer lasting effects Computerized Axial Tomography (CAT/CT Scan): o injects dye into the blood to increase imaging contrast; x-rays are passed through the head while the scanner rotates; used to diagnose/detect tumors, strokes, and atrophy in the brain provides structural information Recording Brain Activity: o Electroencephalograph (EEG) – measures neuronal electrical activity in the brain; displays average activity of a given population of cells; used to measure activity during a task (controls are necessary) o Magnetoencephalograph (MEG) – uses magnetic fields to measure neuronal activity; better temporal resolution than EEG; when used during a task, requires necessary controls Magnetic Resonance Imaging (MRI): o Hydrogen atoms exposed to magnetic field will align with said field; brief pulse of radio frequency applied; atoms will release energy as they return to their original positions; complex computer systems analyze the energy released and use it to map the structures of the brain and transform it into an image Recording Brain Activity: o PET (Positron-Emission Tomography) – creates an image of the most active brain regions; uses radioactive tracer to measure activity; detects collision of positron and electron (from the decaying radioactive tracer, usually glucose) and measures the radiation that is emitted; high radioactivity means higher blood flow, which indicates greater activity; risk because of exposure to radioactivity but can look at specific neurotransmitters o fMRI (functional MRI) – uses BOLD(blood oxygen level dependent) signal (deoxygenated hemoglobin) to measure brain activity; better temporal resolution; oxygenated and de-oxygenated blood react differently to the magnetic field; often used when subject is performing tasks in the scanner; measures areas of activity by locating regions with deoxygenated blood Relationship of Brain Mass to Body Mass Across Species: not very reliable Cortical Areas Whose Size Correlate With IQ: (.3) weak relationship between size of brain and IQ; certain brain regions do correlate with IQ; neither measure of IQ nor measures of cortical area mass are reliable enough at this point to produce significant experimental results Friday Lecture: Nerve Cells and Impulses Neurons: communication cells; humans have approximately 100 billion Santiago Ramon y Cajal: Father of Neuroscience; created detailed and complex drawings that were mostly accurate; discovered that neurons are not connected to one another; Neuronal Doctrine – neurons are the smallest functional unit of the nervous system Camillo Golgi – thought that neurons were connected (wrong); invented Golgi stain that uses silver chromate solution to stain individual neuronal cell bodies Cell Structure: o Plasma Membrane – phospholipid bilayer; selectively permeable; serves as a barrier between outside environment and inside of the cell o Nucleus – located in soma; contains DNA o Mitochondria – energy source for the cell’s activities; powerhouse of the cell o Ribosomes – molecules than synthesize proteins in the cell o Endoplasmic Reticulum – structure that houses many ribosomes Cellular Membrane: phospholipid bilayer (hydrophobic lipid tails and hydrophilic phosphate heads); have embedded protein channels (some voltage-gated) that either allow or do not allow certain molecules into the cell Neuronal Structure: o Neurons have many of the same organelles as other cells but have distinct structures o Muscles and sensory organs are reached by long axons o Components of the neuron include soma, axon (with terminal), and dendrites Dendrites: receive incoming cell signals; branching may be more or less extensive – the more branching there is, the more information can be received (more surface area for incoming “message”) Dendritic Spines in Disorders: the number and condition of dendritic spines can be indicative of pathology in the brain – some diseases associated with abnormal spines are ASD (autism spectrum disorders), schizophrenia, and Alzheimer’s disease Soma: contains the nucleus (and, accordingly, the cell’s DNA); determines cell differentiation; also contains other organelles such as mitochondria and ribosomes; densely packed site for synapses Axons: o Structure for carrying/transmitting messages from soma to other neurons o Myelin sheath covering speeds propagation down an axon; Nodes of Ranvier are breaks in the myelin sheath where ions can reenergize the action potential o Ex. A fibers carry pain information very quickly because they have myelination all along the fiber (initial pain felt), whereas C fibers transmit pain information more slowly and are less myelinated (aching pain felt – a reminder to the body to rest and recover) o Presynaptic terminals on the ends of axons release neurotransmitters that influence postsynaptic cells Motor Neuron vs. Sensory Neuron: o Sensory Neuron (afferent) – dendrites are sensitive to incoming sensory information; transmit information along axon to the spinal cord o Motor Neuron (efferent) – cell body is in the spinal cord; sends information along axon to innervate muscles Afferent vs. Efferent: think SAME (Sensory Afferent Motor Efferent) The Diverse Shape of Neurons: neurons can be many different shapes and have different numbers of neurites and different amounts of branching; structure correlates with function; ex. Purkinje cell versus bipolar cell – more branching (in the Purkinje cell) means less acuity but it other cells (bipolar cells in the retina) there are fewer dendritic branches resulting in a more specific message o Bipolar Neurons – two neurites: one axon and one dendrite branching away from the soma (connector cell in retina) o Unipolar Neurons – some is attached to one neuron with one end branching to receive information o Multipolar Neurons – one axon with many dendrites branching off of the soma Glia: o Astrocytes: Immune system of the brain; use cytokines (proteins), which can affect emotions; take up ions from the synapse and can release other molecules; remove waste materials when neurons die; “glue” ( really much more than that) Also involved in memory, learning, and regulation of stress and emotions Synchronizes the nervous system – tripartite synapse: glutamate regulation, gliotransmission, and calcium transients o Microglia: Main immune defense for the nervous system; phagocytes – gobble up waste and dead neurons Play a critical part in restructuring the brain with experience; neuroplasticity; “neurons that fire together wire together;” neurons not used may die and be consumed by microglia Early in development, many synapses are restructured by microglia as our brain builds more efficient neural circuits (removes weak synapses) Nervous system trauma incites immediate response from microglia (pro-inflammatory cytokines are released in abundance) Oligodendrocytes and Schwann Cells: cells that compose the myelin sheath around axons; oligodendroglia are only found in the CNS, whereas Schwann cells are in the PNS only; nourish cell Radial Glia: guide migration of neurons; most eventually differentiate into neurons but others become astrocytes and oligodendrocytes Fun Fact: Neurogenesis only occurs (as far as we know) in two regions of the brain – the olfactory bulb and an area of the dorsal hippocampus Neurons vs. Glia: neurons have axons and glia do not; neurons house synaptic vesicles and communicate at the synapse and glia possess neither of the features; glia have the ability to divide (in response to injury, for example), whereas neurons do not Blood-Brain Barrier: filtering mechanism of blood vessels that carry blood to brain and spinal cord o Why do we need a blood-brain barrier??? In much of the body, our immune systems fight pathogens by killing off infected cells… neurons do not regenerate readily, so this is NOT a viable option in the nervous system hence, we have a barrier to keep out unwanted viruses, molecules, other substances, etc. Microglia do have the ability to lead an immune response without killing neurons but it is often not completely effective (ex. chicken pox shingles) o What can get through the blood-brain barrier??? Small uncharged particles can get through (oxygen and carbon dioxide); any molecules that are fat-soluble and will dissolve in the membrane (this includes vitamins and drugs that act on the brain); active transport (requires energy so that a protein embedded in the membrane can transport a molecule across) allows useful chemicals such as glucose, amino acids, and hormones to cross o Why do we sometimes get annoyed with the blood-brain barrier??? It prevents molecules getting through that might be helpful in solving problems in the brain – for example, this is why brain cancer is so difficult to treat Nourishment of Vertebrate Neurons: o Glucose and Oxygen – readily available/accessible (more so than ketones or lactate); made with amino acids and carbohydrates; PET – glucose, fMRI – deoxygenated hemoglobin o Thiamine and Vitamin B (prerequisite to using glucose) – Korsakoff’s syndrome: neuronal death memory impairment The Nerve Impulse: neurons are responsible for transmitting information to all the remote regions of the body and often over long distances; message (action potential) is regenerated along the axon and does not decay as it is propagated to the axon terminal Balancing Electrochemical Forces: living cells possess electrical charges; anions are negative and cations are positive; vocab to know: ions, cations, anions, intracellular/extracellular fluid important for discussion of action potentials (neuron communication) Resting Membrane Potential: o Electrical Gradient (or Polarization) – the difference in charge across a membrane; the difference in electrical charge of the inside of the cell versus the outside environment o Voltage-gated ion channels in the semi-permeable cell membrane determine the state of the cell…(more to come)
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