Notes: MCB 61 / Brain, Mind, Behavior

19 minute read

Published:

These notes are for Summer 2022’s Brain, Mind, and Behavior, taught by David Presti. I took notes up to chapter 13 on Presti’s Foundational Concepts in Neuroscience textbook.

Midterm

Chapter 1

Chauvet Cave: cave in Southern France with drawings from Paleolithic humans deep in the cavern; darkness of cave enabled inner exploration Shamans: healers “skilled in accessing states of mind that are sources of knowledge and power, which may then be used in the service of others in the community” opening scenes of Stanley Kubrick’s 2001: A Space Odyssey: one group of hominins (protohumans, including ardipithecus, australopithecus, and homo) discovers bones as weapons HAL: AI aboard spaceship, open question about whether it counts as “concious” size of brain rapidly expanded in last 2 mm years, with more sophisticated behaviors mind: the collection of mental experiences, or our subjective (first-person, internal) experiences, including our thoughts, feelings, perceptions (visual, auditory, olfactory, gustatory, tactile), mental images, and sense of self. consciousness: the capacity to be aware; closely related but not the same, e.g. in a dream or Freudian unconcious mind-body problem: what is the relationship between our mental experience and the physiology of our body and brain?

Chapter 2

William James: “pioneer in the modern scientific study of mind,” found that damage to brain impairs senses The nervous system is a network within the body that functions to manipulate external and internal information. Neurons are involved in the signal transduction in the nervous system whereas neuroglia are the supporting cells of the neurons Hydra and worms have basic nueral networks, insects more complex Vertibrates all have forebrain, midbrain, and hindbrain regions; cerebrum is larger in the evolutionarily recent birds and mammals Mammalian cerebrum has bumps (gyri) and grooves (sulci) Four lobes of the cerebral cortex: frontal, parietal, occipital, and temporal. Corpus callosum: a bundle of approximately 200 million nerve fibers connecting the right and left cerebral hemispheres Andreas Vesalius: Italian physician who carefully disected bodies, producing illustrations meninges: comprised of, from outside to inner, dura mater, arachnoid, and pia mater; cerebrospinal fluid (CSF) rests between arachnoid and pia layers; meningitis is an infection of this area Descartes thought signaling might happen via fluid pressure Luigi Galvani: Italian physician, found evidence that electricity drives signaling by animating legs of dead frogs; work carried on by other physicians, helped by rigorous theories of electricity Camillo Golgi: developed technique for brain staining involving potassium dichromate, silver nitrate, and silver chromate Santiago Ramon y Cajal worked with Golgi to show that brains were densely packed with nuerons and glias

Chapter 3

chemistry: the scientific endeavor concerned with the nature of matter and its transformations; “chemistry investigates the conditions of how these elemental constituents (atoms) interact to form larger entities called molecules” alchemy was also concerned with the nature and transformation of matter (e.g. Boyle/Newton sought Philosopher’s Stone), but by Lavoisier and Priestley, it mostly transitioned Dmitri Mendeleev organized chemitcal elements into periodic table elements of humans by weight: oxygen ~ 65% carbon ~ 18.5% hydrogen ~ 9.5% nitrogen ~ 3.2% calcium ~ 1.5% phosphorus ~ 1.0% potassium ~ 0.4% sulfur ~ 0.3% sodium ~ 0.2% chlorine ~ 0.2% without water, carbon dominates ions have net positive (cations) or negative charge (anions) covalent chemical bonds: “sharing of electrons between atoms” organic molecules contain mostly carbon (which defines the structure) and hydrogen (most numerous); molecules with only carbon and hydrogen are hydrocarbons (e.g. methane, petroleum, ethylene) rules for diagrams: covalent bonds = lines, carbon and hydrogen are implicit, polarity: separation of charge between different parts of the molecule, e.g. in water in hydrogen bonds, “the slightly negative oxygen atom of one water molecule is attracted to the slightly positive hydrogen atom of another” hydrophobic / lipophilic = avoids water, drawn to lipids; hydrophilic / lipophobic; avoids lipids, drawn to water lipids / fats, phospholipids: medium-size molecules composed primarily of carbon and hydrogen atoms in long chains, generally sixteen to twenty-four carbon atoms long a fatty acid is a hydrocarbon chain with a carboxylic acid group attached phospholipid bilayer membrane: “the hydrophilic head groups form the exterior surfaces (in contact with one another and in contact with the water environment), and the hydrophobic tail groups are inside the layers (in contact with one another and shielded from contact with the water environment by the hydrophilic heads)” quaternary amine: “positive charge comes from an electron deficit arising from the nitrogen having four bonds with other atoms, rather than its customary three” amino acids: “a molecule that contains both an amine group (-NH2) and a carboxylic acid group (-COOH)”; amino acids can join together with peptide bonds to form a chain of amino acids called a polypeptide proteins: “large molecules built from amino acids linked into long chains by covalent chemical bonds, called peptide bonds.” levels of description for protein structure: primary (list of amino acids forming the protein), secondary (interactions to produce local folding, e.g. alpha helix), tertiary (overall shape), quaternary (multiple polypeptide subunit,) carbohydrates: enormous molecules, such as glycogen, starches, and cellulose, storing lots of energy nucleic acids: deoxyribonucleic acid (DNA), ribonucleic acid (RNA); composed of chains of nucleotides, denine (A), cytosine (C), guanine (G), and thymine (T)

Chapter 4

Charles Darwin: proposed theory of evolution, including variation in attributes and natural selection Gregor Mendel: experimented with plants, showed that characteristics are stored in genes gene: fundamental unit of heriditary information Niels Bohr suggested that studying genes/living organisms could fundamentally disrupt the cell, corrupting results Max Delbrück hypothesized that genes are stored in large molecules, mutated by x-rays, towards which Erwin Schrödinger drew attention; he later studied bactiophages, which were composed of DNA and RNA Oswald Avery first demonstrated that DNA can carry information, not protein, but it wasn’t widely accepted until the Hershey-Chase experiment, which used radioactive markers Francis Crick and James Watson proposed the double-helical structure of DNA: “adenine (A), thymine (T), guanine (G), and cytosine (C),joined by covalent bonds to a very long backbone of sugar molecules (deoxyribose) and phosphates (phosphorus-oxygen groups).” triplets of necleoties, or codons, corresponding to amino acids, of which there are only 20, so there is duplication DNA is converted to RNA by substituting G-C, C-G, T-A, A-U (transcription); then carried by mRNA to ribosomes to synthesize proteins (translation)

Chapter 5

Electricity = movement of charge major ions for neural function: Na+, K+, Cl-, Ca++ diffusion: thermal agitation produces random movements that distribute particles uniformly, e.g. milk in tea ion channels: proteins embedded in cell membrane that allow certain ions ion pumps: proteins that use energy to move ions, e.g. Na/K pump (moves Na+ out, brings K+ in) ATP: adenine and a ribose sugar, storing substantial energy energy consumption by human brain is 25 percent of the total basal consumption, or about 360 kilocalories per day ion concentration differences inside and outside a neuron result in electric charge differences membrane potential and resting potential:voltage across the nerve cell membrane, measured by placing one electrode from a voltmeter inside the cell and a second voltmeter electrode outside the cell hyperpolarization: creation of a greater separation of charge across a cell membrane, e.g. opening K+ or Cl- channels depolarization: positive voltage enters the neuron, decreased separation of chage, e.g. Na+ or Ca++ entering Alan Hodgkin, Andrew Huxley directly measured action potential action potential: a depolarization large enough to reach about -50 mV causes the membrane potential to rapidly become positive, peaking at +30mV voltage-gated ion channels: closed when the membrane potential is at rest and opens at some voltage, e.g. -50mV for Na+ and +30mV for K+ action potential propagation along axon/soma: local depolarization triggers the voltage-gated channels in the adjacent axonal region to open axon hillock: the region where the axon emerges from the soma of the cell, where voltage-gated sodium and potassium channels occur in high density. refractory period: “after the voltage-gated sodium and potassium channels are triggered to open and close, they require several milliseconds to return to a state that can be triggered again to open.” myelin: layers of lipid bilayer membrane, covers many nerve cell axons, contributes to structural integrity and fluidity oligodendrocytes, Schwann cells: myelinating cells of the central nervous system nodes of Ranvier: gaps along the axon with high conceptrations of ion channels saltatory conduction: action potential leaps from one node to the next, incoming potnetials rapidly jump across nodes

Chapter 6

electrical synapse: built from clusters of proteins that form channels in the membranes of two adjacent cells, a.k.a. gap single channel is called a connexon, and each connexon is made up of several component proteins called connexins chemical synapse: more complex and provides opportunities for additional kinds of regulation, such as changes in strength, feedback, and varied effects on different target cells; a.k.a. “synapse”, without qualification SNARE complex is comprised of synaptic vesicle, small spheres formed of lipid bilayer membrane, filled with several thousand neurotransmitter molecules, and synaptic cleft, which separates presynaptic axon terminal and the postsynaptic cell neurotransmitter receptor: located in the cell membranes of postsynaptic neurons, recieves transmittors like a key and lock reuptake transporter: proteins that move nuerotransmitters from the exterior of the cell back into the interior, and so out of the synaptic cleft dendritic spine: a bulge on a dendrite that increases the surface area available for receiving signalss Otto Loewi: proved existence of neurotransmitters by stimulating frog hearts and transplanting fluids Vagusstoff (also acetylcholine, the first molecule recognized as a neurotransmitter) was found to mediate signal from vagus nerve to the heart glutamate: most abundant neurotransmitter molecule, also a building-block amino acid GABA: gamma-amino-butyric acid, major inhibitory neurotransmitter glutamic acid decarboxylase ionotropic receptor: spans the cell membrane, has donut like hole, composed of four or five protein subunits, closed and opens with nuerotramitter binds to a site, a.k.a. ligand-gated channel receptor, EPSP: excitatory postsynaptic potential IPSP: inhibitory postsynaptic potential, commonly by way of GABA spatial and temporal summation of neuronal input metabotropic receptor: affect chemistry inside the cell, e.g. ion channels may open or close, enzymes may be activated or inactivated, gene transcription may be turned on or off, and so forth GPCR (G-protein-coupled receptors) signaling: molecule of GDP (guanosine diphosphate) attached to the G-protein comes off and is replaced with a molecule of GTP (guanosine triphosphate, a chemical relative of ATP), pieces of G-protein then move around on the inner surface of the cell membrane and bind to other things G-protein pieces can bind with adenylate cyclase. catalized cAMP, which can activate protein kinase, among other proteins cAMP, cGMP, IP3 and DAG are sometimes called intracellular messengers or second messengers

Chapter 7

neuromuscular junction: mediate communication between nerves and skeletal muscles in humans and other vertebrate animals CNS: brain and spiral cord PNS: all other parts of the body’s neural networks, sensory systems, sensory input from skin; receptors in muscles; connections from CNS to muscles (nueromuscular system) cranial nerves: connect CNS and PNS, 12 pairs entering/exiting the brain autonomic nervous system: regulates various body organs and internal functions, such as heart rate, blood pressure, respiration, and digestion sympathetic (fight or flight), parasympathetic (return to calm) sympathetic ganglia: clusters of nerve cells just outside the spinal cord all along its length, sends out signals parasympathetic ganglia: located farther from the CNS than are the sympathetic ganglia agonist: a molecule that binds to a neurotransmitter receptor and activates it antagonist: molecule that binds to a neurotransmitter receptor and blocks the action of the neurotransmitter at the receptor sympathomimetic: has a stimulating effect on the sympathetic nervous system sympatholytic: opposite of sympathomimetic parasympathomimetic: has a stimulating effect on the parasympathetic nervous system parasympatholytic: opposite of parasympathomimetic autonomic neurotransmitters (NT): norepinephrine, acetylcholine:

  • produced and released by a relatively small number of neurons that send highly branched axons throughout large parts of the brain
  • choline acetyltransferase catalyzes the synthesis of ACh from acetate and choline,
  • acetylcholinesterase is responsible for the rapid cleavage of ACh back to acetate and choline after its release at axon terminals
  • basal forebrain nuclei, midbrain pontine nuclei are known to release acetylcholine monoamines possess an amine group located at the end of a short chain of carbon atoms serotonin: located in several clusters of cells in the brainstem called the raphe nuclei, highly branched axons extending throughout the brain. dopamine: ventral tegmentum, substantia nigra norepinephrine: locus coeruleus biosynthesis of monoamine neurotransmitters: phenylalanine, tyrosine, DOPa, dopamine, norepinephrine, epinephrine peptide neurotransmitters: polypeptides, ranging in length from five to thirty-one amino acids, not much is known Most receptors are GPCrs, there’s ionotropic receptors to serotonin (5HT3) and ATP/ADP/AMP (purine receptors) seizure:
  • could be manifestation of runaway excitation, resulting in changes in sensory perception, emotional/cognitive changes, involuntary movement
  • most seizures are idiopathic, meaning that they is no known cause, constitutes 1 percent of the US population epilepsy: clinical condition of recurring seizures antiseizure medications: reduces the amount of excitation, or enhances the amount of inhibition, via interference with voltage-gated sodium, potassium, and calcium channels; facilitation of the inhibitory action of GABA; and reduction of the excitatory action of glutamate. excitotoxicity: overexcitation of neurons by glutamate, associated with activation of ionotropic glutamate receptors

Chapter 8

drug: chemical that in small amounts has a significant effect on body function pharmacology: scientific study of drugs (origins, compositions, effect on body) Paracelsus: Swiss physician & alchemist, “poisons may be medicines and that medicines are also poisons” tetrodotoxin (TTX): poison made by bacteria in many animals (incl. pufferfish), sticks to and blocks sodium channel, leading to numbness, does not effect heartbet or brain blood-brain barrier:

  • how blood vessels are constructed in CNS to regulate exchange of material between blood and brain
  • walls of blood vessels are tight in CNS
  • crosses via transporter proteins or dissolution (if hydrophobic) TTX resistance: variants of NA+ channel reduce sensitivity saxitoxin similarly blocks NA+ channels PSP: paralytic shellfish poisoning caused by STX, like TTX batrachotoxins (BTXs): interacts with channel protein, used by Amazonian tribes, might be from insects local anesthesia: produce loss of sensation locally, first one was cocaine, inteferes with Na+ channels nicotinic: activates one kind of AChR (acetylcholine receptor) muscarinic AChRs: derived from mushroom (Atropa belladonna), antagonized by atropine Atropine crosses blood-brain barrior, ipratropium nearly identical psychoactive drugs: top 5
    1. caffeine, 2. ethyl alcohol, 3. nicotine, 4. areca nut, 5 cannabis

Chapter 8

caffeine:

  • in coffee, sodas, etc.
  • increases wakefulness, stimulates cardiovascular system, blocks adenosine receptors (GPCRs) nicotine:
  • isolated from tobacco (Nicotiana tabacum)
  • binds an agonist at nAChRs, produces relaxation, alertness alcohol:
  • ethyl alcohol
  • sedative-hypnotic drugs, in high doses produces sleep
  • barbiturates are one of the first synthesized drugs
  • benzodiazepines and general anesthetics are similar sedative hypnotic drugs opium:
  • opium poppy (Papaver somniferum) used for millenia
  • morphine symthesized by Friedrich Wilhelm Sertürner
  • opioids include heroin (semisynthetic) diacetylmorphine, fentanyl ( synthetic opioids)
  • endorphins function as agonists to opioid receptors cocaine:
  • Erythroxylum coca is the source
  • effects of cocaine include: blockhing reuptake of transportators of norepinephrine and dopamine at synapses, producing CNS stimulant effects (positive mood, overarousal) and autonomic (cardiovascular stress), psychosis (from stress) amphetamine and related molecules:
  • makes reuptake receptors leaky, creating similar effects psychedelics:
  • produces complex effects, including intensified thoughts
  • Arthur Heffter discovered mescaline from peyote cactus
  • LSD was synthized by Albert Hofmann
  • Maria Sabina convined Gordon Wasson to take Psilocybe mushrooms, which contain psilocybin
  • DMT is brewed into ayahuasca Cannabis:
  • tetrahydrocannabinol (THC) is the major psychoactive element
  • endocannabinoids (e.g. anandamide) are not directly related, but act as agonist to the same receptor
  • retrograde signaling: information is carried in the opposite of expected direction

Chapter 10

human genome: 3*10^9 nucleotide base pairs, of which >85% is transcribed, <3% is translated transcription factors stem cells, cell differentiation neural progenitor cells: become various nuerons or glia, called neurogenesis and gliogenesis neural tube: within 3 weeks of conception, becomes CNS growth cone: progresses via the extension of fingerlike structures called filopodia, propelled by cytoskeleton, microtubule and microfilament, made by actin and tubulin Roger Sperry: studied regeneration, made chemoaffinity hypothesis that nerve cells use chemical signals to guide development neurotrophins, nerve growth and guidance factors, promote growth and survival of nuerons neuroplasticity refers to evolution of brain, which includes synaptic pruning embryonic neurogenesis: myelination of axons through twenty years of age adult neurogenesis

Chapter 11

sensation: the collection of information from the environment via sensory organs and receptors perception: the analysis and interpretation of this information by the nervous system, contributing to the experience of mental states of perceptual awareness. bacterial chemotaxis is when bacteria will swim towards greater concentrations E. coli chemotaxis: runs and tumbles similar examples are phototropism (moving towards light) and phototaxis (bending towards light) naive realism: “what we perceive is identical to what actually exists in the world” electromagnetic spectrum: spans from very high-energy gamma rays and xrays to moderately high-energy ultraviolet radiation, to visible light, to infrared radiation, to microwaves, and finally to relatively lowenergy radio waves Karl von Frisch demonstrated that honeybees have color vision pit vipers have pit organs that detect infrared radiation in a way similar to how eyes detect visible light light polarization: vibration of the electromagnetic field aligned along specific angles in relation to the direction of propagation audition: very low and very high frequency sound detection electroreception in sharks: used to detect the electical signals of fish magnetic field sensitivity and animal navigation: used by pigeons

Chapter 12

olfaction: sense of smell olfactory receptor cells: dendrites of the receptor cells branch into cilia containing olfactory receptor proteins; cilia extend into the mucus lining the nasal passage, and their filamentous structure provides a large surface area containing olfactory receptor proteins olfactory stem cells: allow the receptor cells to be regularly replaced, something that happens about every one to two months cilia olfactory receptor proteins: G-protein-coupled receptors, in varying quantities, corresponding to molecules with specific shapes pseudogene: nonfunctional genes, altered so as to not encode functional receptor proteins essential oil: oily concentrate of aromatic molecules from a plant aromas: usually comprised of mixtures of molecules, but often one or two molecules dominate sulfur-hydrogen groups define thiols—they stank anosmia: specific (loss of sensitivity to a specific kind of smell) and general (loss of sensitivity to a large variety of aromas) olfactory bulb: receptor cells send axons into the olfactory bulb, right above nose pheromones: chemicals that carry signal information related to social communications between members of the same species vomeronasal organ: responds somewhat selectively to pheromone molecules

Chapter 13

taste bud: cluster of receptors cells in the mouth stem cells: adjacent to the taste receptor cells; can differentiate into the various types of taste receptor cells taste categories and receptor cell types:

  • salt: NaCl mostly, channels that allow sodium ions to flow across the membrane.
  • sour: associated with release of hydrogen ions (H*) in solution, channels sensitive to hydrogen ions
  • bitter: 30+ G-protein-coupled receptors
  • sweet: dimer of two GPCRs, hackable by sweeteners
  • umami: responds to glutamate with taste receptor proteins that are metabotropic (GPCR) glutamate receptors. salt, sour, bitter, sweet, umami taste receptor proteins: ion channels and GPCRs perception of spicyness enter via the fifth cranial nerve (trigeminal nerve) menthol: enters via separate signaling pathway for cold TRP channels: associated with spiciness and mintiness, temperature, etc.