Introduction to Neurons PDF

What Are the Nervous System’s Functional Units? Chapter 3 Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition What Are the Nervous System’s Functional Units? Cells of the Nervous System Internal Structure of a Cell...

What Are the Nervous System’s Functional Units? Chapter 3 Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition What Are the Nervous System’s Functional Units? Cells of the Nervous System Internal Structure of a Cell Genes, Cells, and Behavior Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Internal Structure of a Cell NET! NEURON! GOLGI CAJAL Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Two Views of a Cell Cajal used the Golgi stain to show that the nervous system was made up of discrete cells, thereby supporting the neuron hypothesis. Cajal’s neuron theory Neurons are the nervous system’s functional units; now the accepted theory of brain organization. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Basic Structure of a Neuron Branching extensions, or dendrites, collect information from other cells. Core region called the cell body, or soma Main root is the single axon, which carries messages to other neurons. A neuron has only one axon, but most have many dendrites. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition The Basis of Information Processing: Neurons Neurons Most behaviors are produced by groups of hundreds or thousands of neurons. Functional groups of neurons, or neural networks, connect wide areas of the brain and spinal cord. An ongoing effort aims to map the structural connectivity—the physical wiring, or connectome—of the entire human brain. Each neuron’s appearance is distinctive, but neurons are also the essence of plasticity. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition A NEURON Neurons are the building blocks of the brain. They a structured in way that allows them to communicated with each other and with other components of the body, even over long distances. They come in many shapes and sizes, but this is the classic presentation of a neuron. DENDRITES Dendrites stretch out from the neuron like the branches of a tree, increasing the surface area of the neuron. They are coated in many receptors, which allow them to detect the presence of a neurotransmitter. This is where a neuron receives an incoming signal. SOMA (CELL BODY) This part of the neuron contains the nucleus, which stores all the DNA in the cell. This area also include many of the key components of any cell, like mitochondria, golgi bodies, and endoplasmic reticulum. AXON HILLOCK The axon hillock is the part of the neuron where the soma meets the axon. This part of the neuron is very sensitive to the changes that happen when a neurotransmitter binds to the receptors on the dendrites. This is where an action potential begins.  AXON The axon is like an electrical cable. It carries electrical current from wherever the soma is to wherever the terminals are – from where the signal needs to start to where the message needs to be delivered.  MYELIN Myelin insulates the axon to make the neuron better able to send its electrical messages quickly and efficiently.  NODES OF RANVIER Nodes of Ranvier are areas of the axon that are exposed between gaps in the myelin. These are regions that allow the electrical signal traveling down the axon to refresh its strength and carry on to the end of the axon. TELODENDRIA Telodendria are the end branches of an axon TERMINALS Terminals, or terminal buttons, are where neurotransmitters like dopamine and serotonin live. When the action potential reaches the end of the axon, these neurotransmitters are released onto the dendrites of another neuron, allowing the signal to carry on. Synapse Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Information Flow Through a Neuron It’s all about direction Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Three Functions of Neurons Sensory neurons Carry information from the sensory receptors in or on the body to the spinal cord. Interneurons (association neurons) Include associate sensory and motor activity within the central nervous system. Motor neurons Send signals from the brain and spinal cord to muscles. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Neuron Shape and Function “FORM FOLLOWS FUNCTION” Cells below are not drawn to scale. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Sensory Neurons Bipolar neuron from the retina Contains one axon and one dendrite Transmits afferent (incoming) sensory information from the retina’s light receptors to the neurons that carry information into the brain’s visual centers. Unipolar somatosensory neuron Is a brain cell that brings sensory information from the body into the spinal cord. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Interneurons (Association Cells) Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Motor Neurons These neurons have extensive dendritic networks, large cell bodies, and long axons that connect to muscles (multipolar) All efferent neural information must pass through motor neurons to reach the muscles. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Neuronal Networks Neural networks are created by connecting these different kinds of neurons to each other. Sensory neurons collect afferent (incoming) information from the body and connect to interneurons that process the information and pass it on to motor neurons. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition The Language of Neurons: Excitation and Inhibition Each neuron receives thousands of excitatory and inhibitory signals every second. Neurons sum these signals and respond accordingly, becoming active or not. A wide range of behavior possibilities emerge from the simple yes/no language of neurons. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Classes of Glial Cells Glial cell Provides insulation, nutrients, and support and that aids in repairing neurons and eliminating waste products. Is produced throughout an organism’s life, and errors in their replication are a main source of abnormal growths (brain tumors). Five classes Ependymal cell Astrocyte Microglial cell Oligodendroglial cell Schwann cell Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Ependymal Cells Small cells found in the walls of the ventricles Make and secrete cerebrospinal fluid (CSF) Hydrocephalus Buildup of pressure in the brain and swelling of the head caused if the flow of CSF is blocked; can result in severe intellectual impairment Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Astrocytes (or Astroglia) Functions Star shaped; provide structural support for neurons Transport substances between neurons and capillaries (blood–brain barrier) Enhance brain activity by providing fuel to active brain regions Promote healing of damaged brain tissue. Newest area of research into astrocyte function is tripartite synaptsomics (the role astrocytes play in neuron-to-neuron communication) Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Blood–Brain Barrier Astrocyte processes attach to neurons and to blood vessel cells, stimulating them to form tight junctions and so form the blood–brain barrier. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Microglia Involved in scavenging of debris and dead cells; phagocytosis. Monitor the health of brain tissue and play the role of its immune system. Identify and attack foreign tissue Invade the area to provide growth factors that aid in repair when brain cells are damaged Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Oligodendroglia and Schwann Cells Myelin Glial coating that surrounds axons in the central and peripheral nervous systems; prevents adjacent neurons from short-circuiting Oligodendroglia cells Glial cells in the CNS that myelinate axons Schwann cells Glial cells in the PNS that myelinate axons Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Neuron Repair Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Internal Structure of a Cell To a large extent, a cell’s proteins determine its characteristics and functions. Each cell can manufacture thousands of proteins. Water, salts, and ions play prominent parts in the cell’s functions. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Chemistry Review: Elements, Atoms, and Ions Element Naturally occurring substance Atom Smallest quantity of an element that retains the properties of that element Contains a nucleus Neutrons have a neutral charge. Protons carry a positive (+) charge. Electrons carry a negative (−) charge. Electrons orbit the nucleus. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Ion Formation Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Chemistry Review Molecules: Salt Molecules Formed when atoms bind together Smallest units of a substance that contain all of that substance’s properties Salts (NaCl) When NaCl is formed, sodium (Na+) gives up an electron to chloride (Cl−). Positively and negatively charged ions are tightly held together by their electrical connection. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition The Basics: Chemistry Review Molecules: Water Water (H2O) Atoms held together by shared electrons Polar molecule Opposite charges at opposite ends Chemical properties of water enable it to dissolve salt crystals into their component ions. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition  Terms to Learn The Cell as a Factory Cell membrane Semipermeable membrane Extracellular fluid Intracellular fluid Nuclear membrane Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Cell Membrane: Barrier and Gatekeeper Cell membrane Separates intracellular and extracellular fluid. Regulates movement of substances into and out of the cell (most cannot pass). Proteins embedded within membrane allow substances into and out of cell. Is made up of phospholipids. Hydrophilic head: phosphorus Hydrophobic tail: lipids (fat molecules) Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Bilayer Cell Membrane Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Bilayer Cell Membrane Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition The Nucleus and Protein Synthesis Nucleus The cell’s executive office Gene Segment of DNA that encodes the synthesis of particular proteins Sequence of nucleotides determines which amino acids are to be joined to form the particular protein. Chromosome Double-helix structure that holds an organism’s entire deoxyribonucleic acid (DNA) sequence; contains the genes Four nucleotide bases Adenine (A), thymine (T), guanine (G), and cytosine (C) Human somatic cells come in 23 chromosome pairs. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Chromosome Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Protein Synthesis Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition The Endoplasmic Reticulum and Protein Manufacture Ribosomes Protein structures that act as catalysts for protein synthesis Translation Later phase of protein synthesis in which the messenger RNA (mRNA) travels from the nucleus to the ER mRNA is translated into a particular sequence of amino acids to form a protein. Transcription (making a copy) Early phase of protein synthesis in which the DNA strands unwind and a complementary strand of messenger RNA (ribonucleic acid) is produced Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Protein Synthesis Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Transcription and Translation in Protein Synthesis Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Four Levels of Protein Structure A protein’s shape and its ability to change shape and to combine with other proteins are central to its function. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Golgi Bodies and Microtubules: Protein Packaging and Shipment Golgi bodies Package proteins in membranes (vesicles) and give them a label indicating where they are to go. Microtubules Transport the vesicles to their destination inside or outside of the cell. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Crossing the Cell Membrane: Channels, Gates, and Pumps Some proteins change shape when other chemicals bind to them; others change shape in response to changes in electrical charge. The protein molecule’s ability to change shape is analogous to a lock in a door. When a key of the appropriate size and shape is inserted into the lock and turned, the locking device activates and changes shape, allowing the door to be closed or opened. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Transmembrane Proteins Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Genes, Cells, and Behavior Genotype Genetic makeup Phenotype Physical and behavioral traits Mendelian genetics Studies how genes influence our traits Named for Gregor Mendel, whose research led to the concept of the gene Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Human Chromosomes Human somatic cells: 23 pairs of chromosomes Chromosome pairs 1 through 22 are called autosomes, and they contain the genes that contribute most to our physical appearance and behavioral functions. The twenty-third pair consists of the sex chromosomes, which contribute to our physical and behavioral sexual characteristics. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Chromosomes and Genes Allele A cell contains two copies of every gene, one inherited from the mother, the other from the father; matching copies are alleles. Dominant allele: the member of the gene pair that is routinely expressed Recessive allele: the member of the gene pair that is routinely unexpressed Homozygous Having two identical alleles for a trait Heterozygous Having two different alleles for the same trait Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Genetic Mutations Involve errors in nucleotide sequence when reproductive cells make gene copies. May be as small as a change in a single nucleotide base or single nucleotide polymorphism (SNP) Can be beneficial, disruptive, or both; may be specific or widespread BRCA1; sickle-cell anemia Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Acquired Genetic Mutations Acquired mutations Not inheritable Have potential to affect behavior May be due to mitotic errors Errors At 1 year of age, a neuron may have up to 300 to 900 mutations; by 80 years of age, it may have as many as 2000 mutations. Aging may be the result of all these genetic mutations; genosenium Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Applying Mendel’s Principles Gregor Mendel introduced the concept of dominant and recessive alleles; Mendelian genetics. Many kinds of brain disorders associated with this form of inheritance. Tay-Sachs disease Huntington disease Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Allele Disorders That Affect the Brain Tay-Sachs disease Inherited birth defect caused by loss of genes that encode the enzyme necessary for breaking down certain fatty substances Appears 4 to 6 months after birth; results in intellectual disability, physical changes, and death by about age 5 Caused by a recessive allele Huntington disease Autosomal disorder that results in motor and cognitive disturbances Caused by an increase in the number of CAG (cytosine-adenine- guanine) repeats on chromosome 4 The buildup of an abnormal version of the huntingtin protein kills brain cells, especially in the basal ganglia and the cortex. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Inheritance Patterns Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Chromosome Abnormalities Genetic disorders Result from an aberration in part of (or all of) a chromosome rather than a single defective allele. Down syndrome Chromosomal abnormality resulting in intellectual impairment and other abnormalities, usually caused by an extra copy of chromosome 21 (trisomy). One parent (usually the mother) passes on to the child two copies of chromosome 21 rather than the normal single chromosome. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Chromosome Aberration Left: Down syndrome, also known as trisomy 21, is caused by an extra chromosome 21 (colored red, bottom row at left). Right: Chris Burke, the first person with Down syndrome to play a leading role on a television series—Life Goes On, in the 1990s— is now in his fifties and remains an advocate for individuals with Down syndrome. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Genetic Engineering Modification of a gene Adding or removing genes from a genome Approaches Selective breeding Cloning Transgenic techniques Knockouts Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Genetic Engineering Approaches: Selective Breeding Selective breeding Effective way to alter gene expression Maintenance of spontaneous mutation Neural and genetic bases of the altered behavior in the mice studied systematically Aids in understanding and treating human disorders Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Genetic Engineering Approaches: Cloning Uses Preserving valuable traits, studying relative influences of heredity and environment, or producing new tissue or organs for transplant to the donor Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Genetic Engineering Approaches: Transgenic Technique Genetic engineering Introduction of genes into an embryo or removal of genes from it Knock-in technology Genes from one species added to the genome of another species and expressed in subsequent generations; transgenic animals Genes used to inactivate a gene so that a line of mice fails to express it. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Genetic Engineering Approaches: Gene Modification Gene modification Modifying genes by altering its code (base pairs) Discovery of the CRISPR/Cas9 genetic scissors Jennifer Doudna of the United States and Emmanuelle Charpentier of France awarded the 2020 Nobel Prize CRISPR machinery Discovered as part of the immune system of bacteria CRISPR RNA base sequence in bacteria seeks out a matching DNA sequence in an invading virus and cuts the virus DNA, thereby inactivating the virus. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition 3-24 CRISPR Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Applying the Epigenetic Code The environment can allow a gene to be expressed or prevent its expression. Epigenetics is viewed as a second code. Describes how a single genetic code produces each different somatic cell type Explains how a single genome can code for many phenotypes Describes how cell functions go astray to produce diseases ranging from cancer to brain dysfunction Describes how experience throughout a lifetime produces changes in behavior. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Applying the Epigenetic Code Epigenetic mechanisms influence protein production. By blocking a gene so that it cannot be transcribed By unlocking a gene so that it can be transcribed An environmental influence can induce or remove one or more blocks, allowing the environment to regulate gene expression. Histone modification Gene (DNA) methylation mRNA modification Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition A Case of Inheriting Experience Reprogramming Allows the cells of the fetus to essentially start afresh and make their own genetic and epigenetic future. Transgenerational epigenetic inheritance Shows that some life experience of ancestors can be inherited in their offspring, at least for a few generations. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition A Case of Inheriting Experience Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Epigenetic Mechanisms Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition Study Guide 1. What do neurons have in common with other kinds of cells? 2. What is it about neurons that make them distinct from other cells in the body? 3. Identify the parts of the neuron and the function of each. 4. In what direction does information flow in a neuron? 5. What is a synapse? How is it structured? Where would you expect to find a synapse on a neuron? Do neurons synapse with one other cell or is it usually many? 6. What are the three types of neurons? How do they differ from each other? 7. Are motor neurons unipolar, multipolar, or bipolar? What about sensory neurons? 8. What does it mean to say that a phospholipid bilayer is “semi-permeable”? 9. Summarize the location (CNS vs PNS) and function of the 5 kinds of glial cells discussed. 10. Is regeneration of axons possible in the CNS? In the PNS? Why? 11. What is the functional role of myelin? What happens if it is damaged? 12. What cell type contributes to blood brain barrier? 13. What qualities do proteins possess that make them able to do their jobs? 14. What are the three types of transmembrane proteins we care about in this chapter? 15. Genotype vs phenotype 16. What is an allele disorder? How does someone get one? 17. Summarize very briefly how genes can be altered through natural occurrences, experiences, and direct manipulation. Psychology in Everyday Life David G. Myers C. Nathan DeWall | Sixth Edition