Biological Psychology I: Genetics, the Nervous System and Neurotransmitter Processes Overview of Today’s Lecture – Introduction to the role of genetics – Structure of the Nervous System – Review of elementary Neuronal Structure and Physiology – Neurotransmitters and Their Neuronal and PsychologicalWe also discuss several other topics like cse 311 uw
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Functions – A Few Practical Illustrations/Applications Some Orienting Concepts on Genetics in Psychology: 1* Every cell in our body contains chromosomes which contain DNA which contain the genes. Human body – Cell – Chromosomes – DNA Genes – What is “Genetics”? 2* A) Heredity of specific characteristics: – e.g. Mendel’s peas: A monk, he developed projects known as Mendelian genetics. Basis for calculating specific probability of a particular train showing up in the next generation based on the previous generation – Recessive and Dominant Genes – Precise mathematical rules – Conditions under which the characteristics show up (hair color, eye color, balding...) Depression, schizophrenia are also genetic but we do not understand those combinations as well – Very, very limited in predicting complicated traits (heart disease, cancer, genetic model of learning?) – Only good when there are single genes in control (often untrue) Fig. 3.2 – Peas and the color of their flowers 3* B) Processes involved in turning genes on and off: Genetic switching, operate in complicated ways in response to environmental conditions. Genes do not operate separate from their environments. Development: why does one cell turn into one type and another a different type? 4* C) polygenic effects: Most illness processes influence us through the simultaneous operation of genes – Chromosomes: 23 pairs in every cell. – What Genes are: Segments of DNA, designed to code for specific proteins. – What Genes do: Regulate the expression of protein (how we think, dream, imagine, hate, create, love….) – Gene Expression: Coding for specific protein product. A segment that gene is momentarily exposed (unwrapped) to its surrounding environment and expression is allowed. RNA polymerase When methyl chemical groups (chemical packages) attach to the DNA there is reduced accessibility to genes Genes not expressed, but repressed. Repression of gene expression can occur through DNA methylation. Methyl groups prevent DNA from unwinding and being exposed, therefore cannot be expressed. “Epigenetic” modifications of genes and the impact for human health (cancer, stressreactivity, etc): Above genome. Events that affect genes but don’t change them. No change of DNA but expression is altered. Comes through experiences (food, toxins, other substances, behavioral effects) All of our cells have the same genes but they’re all different DNA is wrapped around a cluster of proteins called histones. Underlying cancer and stress reactions are epigenetic effects. Tumor suppressing cells are constantly fighting cancer – Can be turned off by an epigenetic modification of the genome. If they’re methylated they are unexpressed (can’t prevent cancer)– Genes are silenced/repressed – Environmental origin – HPA axis – need a health stressresponse to be a healthy person. Healthy stress response genes can be silenced by environmental consequences. – Studies have shown that stressed rat mothers ON EXAM o Rats that don’t get the “rat love” experience have reduced glucocorticoid receptors o Epigenetic modification of the healthy stress response (turned off, cannot handle stress) Genes Affect Behavior – Behavioral Genetics Methods: Differences between identical and nonidentical twins 5* Twin Studies Compare MZ(identical, monozygotic) and DZ(not identical, dizygotic) Twins: 6* Adoption Studies: MZ and DZ adopted in different environments. When some kinds of traits are looked at – the adopted children are much more like their biological parents than their adoptive parents (personality traits, etc.) – Heritability: The degree to which an underlying genetic characteristic in a population accounts for differences in the expression of that trait (don’t tell us anything at all about individuals) only tell us about that trait in a group – Ex. IQ, weight, etc) are hereditable – in a group (population) genetic differences account for differences in the variable Gene Expression Can Be Modified – Manipulating Genes: 7* Pick your Mouse (or person?) You can make them the way you want them to be. 8* Alcohol preferences video: – Manipulating Environments: 9* “Mother Nurture” article: Two groups of mice, calm vs anxious. Crossfostered – Changed to a different mother of different group. Took the pups and switched them after birth. Dip the pups in alcohol to take their smell away so that the mother doesn’t kill the pups that aren’t hers. The pups were more like the mother they were raised by than the one they were biologically related to. Genetically calm pups with anxious mothers became anxious. Environment trumps genetics? IQ, FADS 2 Breastfeeding increases IQ? 10* “epigenetics” again, stressreactivity: A genetic tendency is not expressed because of an environmental effect. How Are Neural Messages Integrated into Communication Systems? – Three systems are coordinated: 11* 1)The Central Nervous System (CNS) Brain and spinal cord12* 2) The Peripheral Nervous System (PNS) 13* 3) The Endocrine System Structure of the Nervous System: The Central Nervous System (CNS) Consists of the Brain and Spinal Cord The Peripheral Nervous System (PNS) connects the CNS to the rest of the body through subdivisions: – 1) The Somatic Nervous System, which acts on skeletal muscles (the muscles attached to bone) Sensory and motor – 2) The Autonomic Nervous System, which acts on visceral muscles (e.g., heart, arteries, gastrointestinal tract) and glands (e.g., salivary, sweat) In the Somatic Nervous System: 1) Sensory Neurons (Afferent Neurons) transmit somatosensory (Bodily information) information from peripheral sensory organs to CNS; and 2) Motor Neurons (Efferent Neurons) bring motor informational commands from CNS to the muscles: Take information and send it to the muscles. Output from brain/spinal cord Sensory Afferent Motor Efferent Fig. 3.8 Touch something – afferent message to spinal cord – reflex (efferent) (don’t need the brain to know it hurts) In the Autonomic Nervous System:All of the organ systems 1) The Sympathetic Nervous System is activating (“Fight or Flight”) Activated under stress, activation of HPA axis 2) The Parasympathetic Nervous System is deactivating (“Rest and Digest”) Calms you down Cannot digest when energy is needed for other things (example: zebra running from lion) Activation – calming – activation – calming… The Endocrine System Communicates Through Hormones Actions of the Nervous System and Endocrine System Are Coordinated – The hypothalamus is a critical integrating structure, as will be explored in the next lecture on brain structure and function. – Central and peripheral systems have to be coordinated with the endocrine system Hypothalamus(Brain) – CRF Anterior Pituitary Gland (Endocrine system) – ACTH – Adrenal Glands – Glucocorticoids (Stress hormone) “Stress” and The HPAAxis – HPA stands for: – Example of StressResponse: – The consequences of dysregulation in the human stress response: 1. Increased visceral fat 2. Lowering of immune system functions 3. Increased arterial plaque (fat in blood vessels) 4. Decreased hippocampal neurogenesis (less likely to produce new hippocampal brain cells, memory function) Neurons, Nerves, and “Tracts”: – Neuron: A cell that’s specialized for communication within the nervous system. – 3 general parts: 1. Input dendrites 2. Cell body 3. Axon – Nerve: Bundles of axons in the peripheral nervous system – Tract: Bundle of axons within the brain in the central nervous system Peripheral Nervous System consists of entire set of “nerves” (cranial and spinal) 12 Cranial Nerves Spinal Nerves Neurons are specialized for communication: What happens at the: – Dendrites? Information coming in – Cell Body? Information is integrated – Axons? Information is communicated further. Axon Hillock: Junction of ?? the Information is gathered and integrated to make a physiological decision if an action potential is generated. If it is, the membrane depolarizes and the action potential is sent downstream Allornone principle Hyperpolarized resting state Some neurons have “myelin sheaths” Insulating globs of fat. and “nodes of ranvier”: What are those? A “node of ranvier” is the space between two myelin sheaths on an axon where depolarization and action potentials occur Spaces in between (nodes of Ranvier)Brief alteration of the resting potential of the membrane (Online tutorial) Normal resting state: outside is hyperpolarized resting state, when a neuron is at rest, it is more negative on the inside ionically. When an action potential is generated, the charge briefly reverses. A Myelin sheath: Protect axons Opportunity for info to be transferred much more quickly Is made from glial cells Provides insulation for axons Speeds up neural transmission by causing action potentials to “jump” across the “nodes of ranvier” (called “saltatory conduction”) (To jump in Spanish is saltar) From the axon hillock to synapsis Action potentials move much more rapidly Saltatory conduction produces faster neural speed and thereby increases how quickly effects at the synapse can occur Myelin sheaths are made from glial cells Neurons are supported by glial cells, but are different Glial Cells – Called Glia – Outnumber Neurons 10:1 in CNS They are the most numerous cell in the nervous system. Outnumber neurons a lot – Form Myelin Sheaths, Blood/Brain Barrier(Filtering out poisons), Help Supply Nutrients to Neurons, etc. – Different Varieties, Different Functions There are more than these 3 types Illustration: 3 Types of glial cells and their structures and functions: – Oligodendrocytes: Myilate neurons (CNS) Asymmetrical; forms myelin around axons in brain and spinal cord– Schwann Cells: Myilate neurons (PNS) Asymmetrical; wraps – Astrocytes: Star shaped; symmetrical, nutritive and support function. Fill up a lot of space. Attach to the blood flow, take sugar and oxygen and bring it to neurons The other half image: Different types of neurons serve different purposes 3 Classes of Neurons: – Motor Neurons Efferent nerves CNS – muscles/glands (movement) – Sensory Neurons Afferent nerves CNS – (perceive) – Interneurons Within CNS transmission – 1) Motor Neurons ( also called efferent nerves): CNS > muscles/glands (enable us to move, e.g.) – 2) Sensory Neurons (also called afferent nerves) : Sensory Organs > CNS (enable us to perceive sensory inputs, like touch) – 3) Interneurons: Within CNS Transmission 14* perform integration and organization functions 15* vastly outnumber Motor and Sensory Neurons (several millions of each compared to 100 billion interneurons) Most numerous neuron but not most numerous cell Tracks, highways of informationAnimation of Neurotransmitters in Brain Review of Handout (Roberts’ “Elementary Lesson in Neurophysiology”) Monoamine Oxidase Inhibitors and SSRI’s both are agonists of Serotonin, but have different mechanisms of action: See figure 3.15 for review Neurotransmitters are synthesized in cell body: how far south would we have to go to find the cell body? Very far away. It’s a miracle the way things work. Neurotransmitters are critical molecules. Synthesized by genetic regulatory processes. Coding by genes. Synaptic vesicles are filled with neurotransmitters Action potentials are generated at the axon hillock when the summed electrical potentials at the site of the axon hillock exceeds a threshold (Hyperpolarized: more Na+ ions on the outside) Resting state = 70 mJ Brief depolarization of the membrane: (Lecture available on course website) More positive on the inside for a brief moment (action potential, ends quickly because the Na+ gates close and K gates open up) Sodium/potassium pump pumps 3 sodium ions out and 2 potassium ions get pumped in Action potentials get propagated and wind up at the end of the axon at the synaptic knob (terminal button) then there’s a set of process that cooccur Calcium ions come into the cell : Exocytosis – synaptic vesicles move to the membrane, bind, open up, and dump neurotransmitters into the synaptic space (trillions) MAGIC Synaptic Space 3 Processes: – Make it to postsynaptic receptors, bind to them briefly, change electrical potentials. Neurotransmitters are like keys that fit in locks (receptors, binding) Either an excitatory change or inhibitory change. Neurotransmitter stays a key, does not become one with the lock/receptor. Releases – Reuptake: Recycling, energy management. It takes energy to transport a neurotransmitter. NT get taken back up into the terminal button and repackaged in vesicles – Catabolism: Breaking stuff down into its parts through the use of enzymes. Enzyme break down NT then the NT are now NT parts (enzymatic deactivation)Drugs Two main classes: Agonists and Antagonists Agonists: Increases NT effects ∙ A. ON EXAM LDopa: molecule that is natural synthesized in the body. Precursor molecule for the development of dopamine. Works in the cell body affecting the synthesis of dopamine itself. o Parkinson’s Disease: patients with PD have a group of neurons that are dopamine containing and they are dying slowly. Not producing sufficient dopamine to have control of their motor processes. Basal Ganglia (Substancia nigra is rapidly deteriorating). Symptoms: trouble initiating and seizing movement. LDopa, in the early stages of PD, increases the production of dopamine for a while. ∙ B. Amphetamines, Cocaine release massive amounts of dopamine. Increase the rates of exocytosis massively ∙ C. Antidepressants influence monoamine NT processes o 1. Tricyclic antidepressants – inhibit reuptake of norepinephrine (and serotonin but not as much) Blocking NT from being taken back, more of the NT in the synaptic space so there can be more effect postsynaptically o 2. SSRI’s Selective Serotonergic Reuptake Inhibitors inhibit 5HT (serotonin) reuptake (also norepinephrine but stronger on serotonin) o 3. Monoamine oxidase inhibitors (MAOI’s) slow “enzymatic deactivation” ∙ D. Ecstasy releases massive amounts of serotonin Antagonists: Decreases NT effects A. Curare (competes with Ach at junction motor nerve and muscle) B. Antipsychotic medications (block postsynaptic DA receptors) Neurotransmitters and Psychological Function STUDY NEUROTRANSMITTERS IN THE BOOK TOO An Unquiet Mind What is a neuron and how does it operate? It is a specialized cell for communication within the nervous system. It has three parts that work together to send information from the brain and for information to arrive from the environment to the brain. Neurotransmitters: Acetylcholine (Ach) – Links Motor Neurons and Muscles (synapse at muscle) Slide 35 Allows us to move our muscles. PNS and CNS – PNS Curare is Ach antagonist, leading to temporary muscle paralysis – CNS Ach is involved in Learning and Memory in CNS – Monoamine oxidase MAO Monoamine deficiency theory states that a deficiency of the monoamine NT are broken down. There is a drug that inhibits this breaking down. (norepinephrine/serotonin/dopamine) – Alzheimer’s Patients Have Low Levels of Ach Video Example: – This Experiment by Joseph Martinez’ explores the causal relationships between CNS Acetylcholine Processes and Learning and Memory Processes (“consolidation” of learning) Role of acetylcholine in learning and memory Scopolamine: Antagonistic, causes “experimental amnesia” – Be sure to take detailed notes to be able to reconstruct the specific details of the experiment: Analysis/Reconstrtuction of Martinez’ Experiment From Video Inject drugs that they know have specific consequences – What is the operational IV? The drug – A: Scopolomine (action: Ach Antagonist) vs. Saline (Question: Why the saline injection?) Saline injection is the control. Without saline injection there may be a confound of sticking the animal with a needle, which is stressful and painful – Implied Physostygmine (Ach Agonist Acetylcholinesteraste inhibitor) – It increases NT in the synapsis. Mechanism: blocks the enzyme that breaks down Acetylcholine. Enzyme: Acetylcholinesteraste ) Could be Another Level of IV – How might subjects and experimenters have been blind? They didn’t know which drug it was Analysis of Martinez’ (continued) – What is the operational DV? 16* (A: “Time” to find food) Because amnesia cannot be measured quantitatively – What is the theoretical DV? 17* (A: “Memory” as a function of biochemical variables) – Results and Conclusions: 18* Scopolomine Caused blockage of post synaptic acetylcholine receptors, leading to an antagonistic effect of CNS acetylcholine, animals took longer to find food (evidence of amnesia) 19* Physostygmine Caused an agonistic affect, the inhibition of Acetylcholinesterase, leading to more NT in synapsis, find food more quickly (evidence of memory enhancement) Neurotransmitters: Dopamine (DA) Involved in muscular activity Motor movement, pleasure and reward, In Parkinson’s Disease, tracts of DA neurons degenerate in Basal Ganglia, (Substantia nigra) leading to abnormally low levels in brain LDopa creates more synthesis in healthy neurons Excesses involved in Schizophrenia? Too much dopamine Antipsychotic Medications are DA antagonists, interfering with DA at postsynaptic receptors Could cause Parkinsonianlike side effects DA Tracts “project” widely through areas of brain (limbic system and cortical structures) dealing with emotion/motivation and thinking/planning/judgment/language Can alter more than motor pathwaysNeurotransmitters: Norephinephrine (NE) – Increases Arousal – Increased levels may be involved in Mania – Decreased levels may be involved in Depression Monoamine deficiency theory states that low levels of NE and serotonin cause depression – Tricyclic antidepressant medications inhibit reuptake, thus functioning as NE agonists Neurotransmitters: Serotonin (5HT) Involved in sleepwakefulness rhythms Massively depleted by Ecstacy (terminal buttons often destroyed) Lots of serotonin is released when you take the drug but serotonin terminal buttons are being destroyed Decreased Levels may lead to depression Increase vulnerability to depression Reuptake Inhibited by Prozac (Fluoxetine) Prozac is in a class of drugs called SSRI’s (Selective Serotonergic Reuptake Inhibitors), all of which are 5HT agonists Neurotransmitters: Gamma Aminobutyric Acid (GABA) – Lowers arousal – Reduces anxiety So does alcohol. Antianxiety drugs are addictive – GABA is the main inhibitory NT in nervous system Decrease the likely hood of transmission downstream What is the main excitatory NT in the nervous system? ON EXAM Glutamate Conclusion: All Psychological Functions (behavioralmotor activation, attention, anxiety, mood, thought, speech, consciousness, intentionality and impulsivity, etc.) are supported and regulated by complex interactions between the CNS and PSN, with diverse types of CNS neurotransmitters playing a central and critical role in our psychological existence, identity, and experience of the world The machinery of mind underlies psychological realities