Neurobiology Study Guide Exam 1 PDF

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Neurobiology Exam 1

Introduction & Brain Organization I What were some of the early views on neuroscience and how have they changed? Aristotle: Believed brain was used to cool the blood and heart controls thoughts. ! Hippocrates: “Father of Medicine”; Studied patients with brain damage; Believed behavioral problems arise when brain is too humid or too dry & inhaled air passes to the brain first and is then distributed to the body. ! Phineas Gage: Railroad worker who survived a metal rod through the head which partially damaged his frontal lobe and reportedly caused a change in his personality. Influenced discussion about mind and brain being correlated as well as influencing discussion about the brain contributing to personality and damage to different regions may induce different changes in personality.

How do neuroscientists study the brain? Gross Dissection: As the brain decays quickly, tissue preservatives such as alcohol, acids, and aldehydes allow for macroscopic (seen with the naked eye without microscope) comparison of brain matter. Histology: The study of the microscopic anatomy of cells and tissues and their details. -Microtome: An instrument that allows hardened tissues to be cut into slices only a few microns thick and then can be stained to see certain areas or examined under microscope. Immunohistochemistry: A technique used to examine molecular features of neurons and glial cells. You can see proteins (antigens) expressed by using antibodies due to the fact the antibodies will bind only to specific antigens and staining them with enzymes. Immune-References antibodies used in the procedure, Histo- meaning tissue. Golgi Staining: An anatomical technique, invented by Camillo Golgi in the 1800’s, that stains a relatively small fraction of all neurons but stains those neurons completely, often revealing both dendrites and axons. This labels individual neurons and their axons which allows us to trace them to the brain and discover how they are connected.

What is the value of the “WHY” questions? It is necessary to be able to answer why questions to gain a full understanding of the subject matter. -Why is the nervous system organized in this specific way? -Why are its parts laid out as they are? -Why do the parts act as they do? -What are its functions in the life of the organism? !1

Neurobiology Exam 1 What was Charles Darwin’s core idea? The origin of heritable variation, such as genetic mutation, may be random, but whether an organism created by this variation survives and leaves its own offspring is decidedly nonrandom. Organisms generally produce more offspring than an ecosystem can sustain. An offspring’s chance for survival and reproduction in the Darwinian “struggle for existence” depend at least in part on the organism’s traits. Some adaptive - boost individual’s chance of survival and reproduction; Some detrimental - decrease chances of survival and reproduction. Darwin realized that the adaptive traits, as long as they are heritable, will over time become more common in the population. Given enough time, these changes in trait frequency cause each species to be well suited for its niche. This is the essence of the Darwin’s concept of natural selection. According to Darwin, Over time, heritable adaptive traits will become more common in the population. Heritable Variation: Genetic mutation that will determine the characteristics of your offspring. -These mutations are RANDOM. -If the organism created by this variation survives and reproduces is NON-RANDOM. Adaptive Trait: Boosts individual’s chance for survival and reproduction. Detrimental Trait: Causes harm to the individuals survival and reproduction. Natural Selection: Darwin’s theory that heritable traits that boost an individual’s chance of survival and reproduction will, over the course of many generations, become more common in the population. As natural selection is not an agent but a process, we cannot say that natural selection explicitly designed organisms to live in their specific niche. We can say it leads to improvements in organismal design. -The process whereby organisms better adapted to their environment tend to survive and produce more offspring. -Doesn’t design the organisms to live in a specific niche. -Leads to improvements in organismal design.

Design Principles: Physical or engineering principles that can be used to argue that a biological feature is “well designed” How do design principles help to shape the organismal form? The idea that biological structures appropriately serve the intended function and work well for the organism. Some principles reflect laws and concepts seen in other areas of life. Some are completely made up by nature to fit the organism’s need.

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Neurobiology Exam 1 What is the nomenclature we use to describe the brain? -Spatial Orientation Nomenclature: Non-Humans: Humans: Superior Dorsal Caudal

Rostral

Posterior

Anterior

Ventral Inferior -Brain Section Plane Orientation Nomenclature: Axial / Horizontal Plane (halved horizontally) Coronal / Frontal Plane (front to back) Midsaggital / Medial Plane (toward midline)

-Brain Sides Orientation Nomenclature: Ipsilateral: On or to the same side. Contralateral: On or to opposing side.

Nervous System: A complex network of nerves and cells that carry messages to and from the brain and spinal cord to various parts of the body. **Vertebrate brains are highly centralized, meaning there are many neurons clumped into one space. This allows for more rapid neural communication due to the fact there is a shorter distance to travel. This also save metabolic energy. Neurobiology: The study of the nervous system and its function. Evolution: The process by which different kinds of living organisms are thought to have developed and diversified from earlier forms. Based on random genetic variation including mutations, gene duplications, and genomic rearrangements.

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Neurobiology Exam 1

Nervous System

Central Nervous System! (Brain, spinal cord, retina/optic nerve)

Autonomic Nervous System! (Communicates with internal organs and glands; INVOLUNTARY reactions)

Peripheral Nervous System! (Axons and neurons outside of brain)

Somatic Nervous System! (Communicates with sense organs and muscles; VOLUNTARY reactions)

Motor Nervous System! (Motor Output)! EFFERENT!

Sympathetic Division! (Arousal)

Parasympathetic Division! (Calming)

Sensory Nervous System! (Sensory Input)! AFFERENT!

Efferent: Conducting impulses EXITING from the central nervous system. Afferent: Conducting impulses APPROACHING the central nervous system. Gray Matter: Contains neuronal cell bodies and dendrites; it also contains un-myelinated axons glial cells and most synapses. Not homogenous. Different features found everywhere. White Matter: Contains myelinated axons and axon bundles called fiber tracts. *If the brain is considered a city, the gray matter is the people and the white matter is the roads that people travel on. *Neurons are clustered into specific regions of gray matter separated by fiber tracts of white matter. !4

Neurobiology Exam 1 Brain Nuclei: Clusters of neuronal cell bodies with similar features, typically segregated from cell bodies that exhibit different sets of features. They are the fundamental units of brain structure and function. The neurons within these brain nuclei have a unique set of connections and physiological properties which brings them together. Neuron: An electrically excitable cell that possesses and transmits information through electrical and chemical signals. Information processor of the body. Glial Cells: Non-neuronal cells within the brain. Includes astrocytes, microglia, oligodendrocytes, and Schwann cells.

CNS

Microglial: small star-shaped glial cells that multiply in response to brain injury, migrate to the site of injury, secrete inflammatory molecules, and engulf cellular debris. -Macrophage of the brain -Smallest of the glial cells -Mesodermally derived -Defensive function ! Astroglia/Astrocyte: star-shaped glial cells that perform a variety of functions including secretion of inflammatory molecules, control of local blood flow, recycling of neurotransmitters, and forming glial scars. -Large, star-shaped -Nutritive & support function -Protect from injury!

PNS

Oligodendrocyte: glial cell that wraps itself around axons and produces the myelin sheath around myelinated axons in the central nervous system. -Asymmetrical -Form sheath around axons in brain and spinal cord ! Schwann Cells: glial cell that produces myelin sheaths around axons in the peripheral nervous system. -Asymmetrical -Form sheath around axons in the peripheral nervous system.

*Neurons and glial cells are the functional subunits of the nervous system. Found in 1:1 ratio. *Only 1-2% of the genes found in the human genome are uniquely expressed in the brain. Synapse: The junction between the terminal of a neuron and either another neuron or a muscle or gland cell, over which a nerve impulse passes.

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Neurobiology Exam 1 Action Potential: An all-or-none electrochemical signal generated by neurons in response to above-threshold stimulation. Neurotransmitter: Any substance responsible for sending nerve signals across a synapse between two neurons. Neuronal Connections: -Neurons communicate through a web of axons but everything is NOT connected to each other. It would cause too much axon connections which takes up valuable space. -These connections must be strategic

Topographic Projections: An axonal projection in which neighboring neurons project to neighboring neurons in the target region. This allows neighboring neurons to process information and minimizes the length of axons which saves space and metabolic energy. Divergence Pathway: Axons may split into two or more branches that project to different targets. -Allows for information from one neuron to be transmitted to several other neurons, which can then use the information differently. Convergence Pathway: Neurons may receive input from two or more other neurons via two or more different axons. -Allows for information from different neurons to be integrated.

Lecture Summary: • The vertebrate nervous system is divided into two systems: CNS & PNS. • The CNS is divisible into the brain, spinal cord and retina. • Important orientation terms include: dorsal, ventral, superior, inferior, ipsilateral, contralateral, sagittal, axial, and coronal. • The nervous system contains neurons and glial cells. The neurons have distinctive dendrites, axons, and synapses. Despite these specializations, only 1-2% of human genes are “brainspecific”. • Neural circuits tend to be replete/stocked with diverging, converging, and reciprocal connections.

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Neurobiology Exam 1 Brain Organization II What are the basic components of the nervous system?

Central Nervous System

Brain

Spinal Cord

Forebrain

Midbrain

Colliculi

Telencephalon

Tegmentum

Diencephalon

Preoptic Area

Cerebral Cortex

Hindbrain

Olfactory Bulb

Cerebellum

Retina

Neocortex

Hypothalamus

Medulla

Thalamus

Telencephalic Nuclei

Pallidum

Piriform Cortex

Pons

Striatum

Septum

Amygdala

Hippocampus

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Neurobiology Exam 1 What functions do the major brain areas serve? -Frontal: Motor control/personality -Parietal: Somatosensory Cortex -Temporal: Auditory and speech processing -Occipital: Visual processing -Insula: Creates emotional responses to stimuli

Frontal

Parietal Insula Occipital Temporal

What is the brain’s functional architecture? Similar/compared usually to that of a computer. ! Neurons, dendrites and axons. What are the characteristics of a “typical” neuron? Cell Body/Soma Lipid Plasma Membrane Nucleus Organelles Nissl Body: Granules of rough endoplasmic reticulum and ribosomes found in the soma which will be the site of protein synthesis! Micro and Neurofilaments, Microtubules: in dendrites leading to soma forming a neural cytoskeleton. Primary and Secondary Dendrites: Branched extensions of a nerve cell along which impulses received from other cells at synapses are transmitted to the cell body. Axon Hillock: A small mound (hillock) on neuronal cell bodies where the axon typically emerges; it typically contains a high density of voltage-gated ion channels, making it a spike initiation zone or trigger zone of the neuron. Axon: A long and thin neuronal process that remains relatively constant in thickness along its length; its main function is to conduct action potentials over long distances. Axon Collateral: A major branch of an axon, distinct from the smaller branches that axons typically form near their targets. Terminal Arborizations: A set of small branches that axons typically form near their target area.

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Neurobiology Exam 1 Diagram of ! a Neuron:

How can scientists “reverse engineer” the brain? Reverse Engineer: The process of trying to understand the inner workings of a system by starting with observations about its behavior. Neurobiology Research: They break down the brain as a whole into individual portions and ask what does this part do and how does it affect the brain as a whole? Then they can deactivate the area to observe what happens and draw conclusions regarding its function by comparing the deactivated individuals to those who are wild-type. Functional Decomposition: Break the organisms down to specific components/functions that it can perform and then determine how they relate to one another in order to understand the organism as a whole. Its how people who build robots do it. Neuropsychology: The science of exploring the neural basis of a psychological process. Phrenology: A Pseudoscience whereby the brain is composed of distinct “cerebral organs”, the size of which is reflected in the shape of the skull. Franz Gall was the first to do this. He broke the mind into 27 mental “faculties” which corresponded to 27 “cerebral organs”. He studied the shape and bumps/ indents of peoples brains and correlated them to their skills/deficiencies. Neuroethology: The science of exploring the neural basis of behavior. By studying animal behavior in their natural habitat and taking into account that to succeed evolutionarily, all organisms must survive long enough to produce viable offspring, research into how an organism knows or is triggered to behave a certain way (find food !9

Neurobiology Exam 1 and water, find out what risks there are, figure out how to reproduce successfully) gives insight into the neurology side. How do brains evolve? A combination of high-level conservation with low-level change is apparent in the evolution of brain regions. Higher regions of the brain tend to be broadly conserved. Small cell groups that are low in the structural hierarchy are often difficult to homologize across species and even if identified they usually vary in size or connectivity. The changes tend to be in genetic differences found in individual genes, gene expression patterns, gene regulation, and protein interactions. Slowly overtime. Rene Descartes: First to propose distinction between mind and body. Thought that external sensory events evoked delicate fluids called “Spirit Animals” within the Pineal Gland to flow through the body to the muscles to make movement or within the brain to evoke thoughts or realize senses. Schwann & Sheldon: Discovered that all tissues were made of cells and proclaimed that the brain is a continuous web of cells. Ramon y Cajal: Proposed that electrical signals pass from cell to cell. Also contributed/evolved Golgi Staining and found the following: -The processes emerging from cell bodies did not fuse into one meshed web -Axons and dendrites are separated by a gap -Dendrites tend to be directed toward the sensory input -Axons tend to be directed toward the brain center -Neurons are functionally polarized — meaning inputs terminating on dendrites and outputs streaming through axons. Camillo Golgi: Created the Golgi Stain (technique that stains a small fraction of all neurons but stains those neurons completely, often revealing dendrites and axons) and believed that the fibers in the brain connected to form one reticulum/massive web. *Together Golgi & Cajal suggested the presence of contact between cells used for communication as well as observing tiny gaps between axons and dendrites. Charles Sherrington: Suggested there are tiny one way valves in the pathways which introduce a time delay and proposed the term synapse to describe the gaps between axons and dendrites. Neuron Doctrine: The idea that each neuron is a distinct cell which is not continuous with other neurons. *Together Cajal and Sherrington contributed to the neuron doctrine with their findings.

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Neurobiology Exam 1

Lecture Summary: • Neural circuits tend to be replete/stocked with diverging, converging, and reciprocal connections. • The brain is comprised of the forebrain, midbrain and hindbrain, which consist of even smaller subdivisions which serve different functions • Forebrain: • Diencephalon (Preoptic Area, Retina, Hypothalamus, Thalamus) • Telencephalon (Cerebral Cortex, Olfactory Bulb, Telencephalic Nuceli) • Cerebral Cortex (Piriform Cortex, Neocortex, Hippocampus) • Telencephali Nuclei (Pallidum, Striatum, Septum, Amygdala) • Midbrain: • Colliculi (Superior and Inferior) • Tegmentum • Hindbrain: • Cerebellum, Pons, Medulla • Major players in our understanding of neurons: Descartes, Schwann & Scheldon, Ramon y Cajal, Camillo Golgi, Charles Sherrington • Studying the brain requires some sort of framework: informed by neuropsychology and neuroethology.

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Neurobiology Exam 1

Resting and Action Potential What is a resting potential vs. an action potential? Resting Potential (Membrane Potential): The voltage difference (electrical potential) across the cell membrane that a cell exhibits when it is not receiving external inputs (resting) -The voltage difference between the inside and outside of the neuron -Resting Potential = -70mV Action Potential: An all-or-none electrochemical signal generated by neurons in response to above-threshold stimulation. -A brief, transient reversal of polarity of the membrane potential that sweeps along the membrane of a neuron. -Action Potential = +40mV Ion: An atom or molecule with a net positive or negative electrical charge (K+ or Na+) What mechanisms generate resting potentials?

Resting Potentials Ionic Basis of the Resting Potential: (Key discovery made on squid giant axons) The axon’s intracellular fluid differs from the extracellular fluid in ion composition. Means that the neurons are actively pumping sodium ions out across their cell membranes and pumping potassium in. Concentration of K+ much higher INSIDE axon ! Concentration of Na+ much higher OUTSIDE axon Changing this relative concentration of an ion across the membrane can affect the resting potential. Resting Potential Membrane Diagram:

Factors Which Induce an Ion to Cross a Membrane: 1.) Action of an ion pump 2.) A difference in the concentration of ions on two sides of the membrane (due to the selectively permeable membrane) 3.) An electrical potential difference across the membrane !12

Neurobiology Exam 1 Ion Pumps: Specialized transporter molecules that pump ions into and out of neurons which requires energy in the form of ATP due to the fact they are moving ions against their concentration gradients. *ATP is the brain’s main currency of metabolic energy Na+/K+-ATPases: Enzyme that moves K+ in and Na+ out of a cell. 2 Po...