Week 6 Brain & Behavior Notes
Week 6 Brain & Behavior Notes Natural Science 2
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Natural Science 2
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This 10 page Class Notes was uploaded by Willow Frederick on Thursday October 13, 2016. The Class Notes belongs to Natural Science 2 at New York University taught by Andre Fenton in Fall 2016. Since its upload, it has received 18 views. For similar materials see Brain and Behavior in CORE at New York University.
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Date Created: 10/13/16
Lecture 9: Neural Communication 5: Neurotransmission & Hormones Neural communication is mediated by exchange, receipt, & transduction of chemical signals. Neurons communicate thru synaptic transmission Neural-hormone interactions: action at a distance Endocrine cells release hormones Chemical Structure of the 3 Types of Hormones –how do these get into cells? 1. Chemical Structure of Protein/Peptide Hormones a. Peptides: short amino acid chains (ex. ACTH, Oxytocin, vasopressin, growth hormone) i. Oxytocin- trust, closeness, social bonding 2. Chemical structure of amine hormones a. Modified single amino acids: ex. Thyroxine, melatonin, adrenaline 3. Chemical structure of steroid hormones a. Derived from cholesterol, which dissolves in fat i. Can get into the cell very easily bc of its shape- does not need a receptor b. Chicken experiment: proves that: i. The hormone testosterone is released into the blood supply by the testes –if you cut them off the chicken does not grow into a big muscular rooster ii. Hormones can enter the bloodstream, reach elsewhere in the body, and effect growth, for example 2 Main Mechanisms of Hormone Action 1. Second messengers ~ peptide hormone action a. Amino acids in the lipid bilayer tend to be non-polar; inside & outside the cell: polar b. Cyclic adenosine monophosphate (cyclic AMP or cAMP) c. Cyclic guanosine monophosphate (cyclic GMP or cGMP) d. May lead to relase of secondary hormones e. May lead to regulation of receptors 2. Steroid hormone action a. Act slower than peptide & amine hormones (hours) b. Act as a transcription factor: controlling expression of specific genes c. Leads to an increase or decrease of protein d. May have nongenomic effects: effects neurons without effecting genes (ex. Estradiol, testosterone) 3. Direct action on the expression of genes Endocrine Feedback Loops- like thermostats, regulating our hormones Hormone Production by the Posterior Pituitary crying becomes a conditioned stimulus to the mother the baby’s crying becomes enough for oxytocin release & milk 2-Stage Hormone Release by the Anterior Pituitary Neuroendocrine cells in the hypothalamus trigger releasing hormones into bloodstream Blood vessels (not axons) carry info (hormones) to the anterior pituitary Releasing hormones trigger anterior pituitary to release tropic hormones Tropic hormones act on organs o Tropic hormones: prolactin, gonadotropic hormones, thyroid- stimulating hormone, AFTH, growth hormone Secretions of the Anterior Pituitary –don’t really need to know this slide (last on ppt) Lecture 10: Evolution Brain circuits & behaviors are all biological traits! They evolve & are subject to natural & sexual selection. Part 1: Sensing the Environment & the Integration of Information Neurons are larger than bacteria Rate of diffusion vs. transfer of info from brain to muscles o What do soccer players & jellyfish have in common that bacteria do not? a nervous system! That’s what allows our complicated behaviors- if we didn’t have a nervous system we couldn’t do the crazy things we do - Neurocommunicat ion via action potentials is what a lottt of species do. action potentials & signal transmission are conserved across species o bacteria sense the environment & react o more complex, interconnected networks of cells need a mechanism to transmit info bw cells in the network the action potential voltage-gated Na+ channels (jellyfish have ‘em too) Networks of neurons to transmit, compute, & store info Brains form an environmental buffer bw us & the outside world—allows body to adapt to the environment Each advance in evolution has a cost o Longer dev period, fewer offspring, metabolic & genetic cost Evolution of human brain complexity depends on the establishment of social & reproductive grouping o Learning & memory for survival Species differences are due to genetic differences (i.e. specific genes & more often relative expression of genes) We learn & remember to adapt to our environment & have better lives, which is what all species do Where we differ from other species is the expression of genes NATURAL SELECTION: Peppered moths’ traits: example of natural selection o Trees in an industrial area became dark so darker moths could hide better from birds in those areas o Trees in the agricultural area were more advantageous for peppered moths –they blend in better with lighter tree bark SEXUAL SELECTION: peacocks o Females prefer males with large feather displays (even tho those aren’t protective against predators or anything) o So the large feather display becomes the norm, is passed onto offspring So what’s the mechanism of variation & evolution? DNA! James Watson & Francis Crick –structure & function Nucleotides held together by weak, electrostatic forces—so it’s not surprising that sometimes the wrong molecule slips into place One of the nucleotides changes Key Idea: specific differences are due to genetic differences i.e. specific genes & more often relative expression of genes Part 2: Comparing Brains & Behaviors The brain helps buffer against variations in the environment There are many hazards that threaten survival—the brain is essential! o Senses the environment o Stores info & remembers past places & events o The brain can provide adaptive responses (the brain can provide adaptive responses)—ex. Inherent & learned aversion to snakes Some behaviors that mammals have in common: o Complex range of movements o Eating, feeding, feeding milk to the young o Sleeping, sleep/wake cycle o Sexual behavior Behaviors that differ bw animal species o Primates have reaching, manipulative movements o Complex language in humans o Higher cognitive function & abstract reasoning (playing chess, for ex) o Sensory specializations in different species Bat has echolocation Rat has a sensitive sense of smell Platypus has keen mechano- & electro-sensation on its bill Brain features that are common across species o Develop from hollow neural tube o Bilateral organization – symmetrical o Segmentation o Hierarchal control- head to tail o Localization of functions Brain comparisons across species o Chemicals: NTs & neuromodulators conserved o Size & weight: brain/body ratio—relationship to behavioral capacity o Shape & structure: major regions conserved, relative size related to capacity, circuit evolution, specialization within a region Serotonin aka 5-HT o Example of a NT & evolutionary conservation o Discovered 1948 by Maurice Rapport Blood vessel constriction, gut movement o Made from the amino acid tryptophan – an essential amino acid that is found in meat/poultry o Serotonergic cells in nearly all vertebrates have the same position at the base of the brain. 500 million years old… o Digestion, blood pressure regulation, sleep/wake cycle, activity cycle, OCD & Tourette’s, grooming, status support/social status (monkeys tend to be less subordinate & rise up in the social hierarchy when given serotonin) o Serotoninergic Circuits: such processes may have been conserved throughout the evolution of the animal kingdom! Humans have a lot more brain proportional to body size compared to other primates o Shape & structure: major regions conserved, relative size related to capacity, circuit evolution, specialization within a region o Size correlates with functional capacity Lecture 11: Sensation & Touching in Your Head (pt.1): Perception, Transduction, Coding Sensations are determined by specialized cells that translate external events into neural events for stereotyped, predetermined info processing by the brain. an adequate stimulus is the type of stimulus to which a sensory organ is particularly adapted o ex. Photic light energy for the eye sensory systems have a restricted range of responsiveness o ex. Frequency range for hearing, which varies with species o specification: the range at which a tool can operate o for example, elephants hear low frequencies that humans do not, and cats hear high frequencies that humans do not why are these ranges so specific? How is this signal transuced from energy in the world to energy in your brain? –Membrane potential changes Law of Specific Nerve Energies: Receptors & neural channels for different senses are independent. o Each sense uses a different ‘nerve energy’ in your nervous system, you have transmembrane potentials. The info representing different kinds of energies stays segregated in the brain o but all senses use the same type of energy—action potentials o the concept of labeled lines says that the brain recognizes distinct senses because action potentials travel along separate nerve tracts receptors for different kinds of touch, then those have axons, and they travel along separately from other types of signals So wherestoes the presynaptic cell get its info? o 1 presynaptic cell in a system= primary sensory neuron o Receptor cell: a specialized cell that responds to a particular external or internal energy (I’m hungry) or substance by sensory transduction o Sensory transduction: the conversion of presence or energy from a stimulus into a change in membrane potential in a receptor cell In other words, To change the kind of energy that is being presented into neural energy o Receptor potentials/ generator potentials: local changes in membrane potential i.e. a type of local graded potential –may turn into Aps ex. Pacinian Corpuscle: skin receptor that detects vibration o stimulus to the PC produces a graded electrical potential o when the potential is big enough, the receptor reaches threshold generates an Action Potential all sensory info enters the spinal cord thru the dorsal, leaves thru ventral o There are proteins that act as ion channels o o o you don’t experience weak stimuli consciously or unconsciously – it’s not enough to tell your brain so you don’t know about it but if a bunch of weak stimuli are grouped together, you may become aware of it we don’t have any control over the membrane stretching/excitatory signal o Coding: patterns of action potentials in a sensory system that reflect a stimulus A single neuron can convey stimulus intensity by changing the frequency of its action potentials Intensity coding: response rate vs. stimulus intensity for 3 neurons w/different thresholds 100 action potentials per second= highest magnitude possible
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