03 - NEURONS - A little neural cell biology A little neural...

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Unformatted text preview: A little neural cell biology A little neural cell biology Cells – basic, single structural, self­ sustaining unit in organisms Mammalian nervous system has two kinds of cells Neurons Glia Neurons are cells (almost) like any other Specialized to create, receive, conduct and send electrochemical signal Communication in the nervous Communication in the nervous system The Neuron Nerve cells basic elements of nervous system. 1 trillion Communicate w/other cells, transmit info, control behavior Parts of the Neuron Parts of the Neuron Axon Dendrite Cell Body Dendrites & Cell Body Dendrites & Cell Body Dendrites carry info from other neurons to cell body. Many dendrites/neuron Cell Body contains nucleus Axon Hillock­ where the soma and axon meet, where the AP begins DENDRITES AXON HILLOCK CELL BODY The Axon The Axon Single tube extends from cell body Carries info from neuron to other neurons. Varies in length Myelin AXON Action Potential Action Potential IF cell membrane rises above certain voltage (threshold), AP is triggered, release of NT. All­or­none event Refractory Period Nerves carry electric signals Nerves carry electric signals Excitatory­ ↑ chance neuron will generate an AP. Inhibitory­ ↓ chance neuron generates AP End Foot/Terminal Button End Foot/Terminal Button The tip of the axon that conveys info to other neurons Creates the synapse with the neighboring dendritic spines Where NT is released End Feet Synapse Synapse Space btw 2 neurons Axon of sending neuron communicates w/ dendrites of receiving neuron Synapse Review of Neurons Review of Neurons Axon – transmits signal Myelin sheath – insulation Nodes of Ranvier – gaps btw the insulation Synaptic terminal – end of the road Dendrites­receive signals from other neurons Cell body = soma Axon hillock – decider in Neurotransmitters Neurotransmitters Chemicals that carry messages across synapse to dendrite of receiver neuron Communicate in mili sec. Very Fast Types of neurons Types of neurons Types of neurons Types of neurons Sensory neuron­ highly sensitive to a particular type of stimulation (touch, temperature, odor etc.) Interneurons­ link info btw sensory and motor cells Include pyramidal, Purkinje, and Stellate cells Motor neuron­ sends signals from the brain and spinal cord to muscles Glial cells Glial cells The support cells of the nervous system Provides insulation, nutrients, support, and repair Regenerate Out number neurons 10 to 1 Types of Glia Types of Glia Astrocytes (orig. in brain; support for CNS) Microglia (orig. in blood & migrate) Blood brain barrier preventing toxins from entering Structural support; hold neurons in place ↑brain activity; signal to blood vessels to expand “janitors and maids;” monitor health of brain tissue Clean up, aid in repair Removal of dead tissue/debris; immune process phagocytosis Ependymal cell (on walls of ventricles) secrete CSF, which acts as a shock absorber; helps eliminate waste, may act as cooling mechanism, source of Other types of Glia Other types of Glia Oligodendrocytes­ myelinate axons in CNS, enclose/separate neurons (oligo, means few; branches compared to astrocytes) Schwann cells­ myelinate axons in PNS; on both sensory and motor axons Myelin Insulation Faster neurotransmission and conductions, less degradation of the signal Multiple Sclerosis (MS) damage of myelin academic.kellogg.cc.mi.us/herbrandsonc/bio201... Quick and dirty Chemistry Quick and dirty Chemistry 92 natural elements Atoms­ smallest quantity of element Oxygen, Hydrogen, Carbon make up 90% of cell Atoms can carry a + or ­ electric charge → Ions Lose electron: atom becomes positive (Na+ ) Gain electron: atom becomes negative (Cl­ ) Atoms combine to make molecules Ex. 2 H + O→ H2 O Non­polar/Polar molecules Non­polar/Polar molecules Non­polar: an equal sharing of electrons between two different atoms Ex. NaCl Polar: unequal sharing of electrons. Opposite charges at opposite ends. Ex. H2 O Polar molecules attract to one another → hydrogen bonds hydrophilic The Cell Membrane: Barrier & The Cell Membrane: Barrier & Gatekeeper Separates intracellular/ extracellular fluid Selectively permeable: allows some chemicals to pass more freely than others Phosopholipids­ Phosphorous head (polar), bound to two lipid tails (nonpolar) Lipid bilayer Hydrophilic polar head Hydrophobic tails Proteins make up channels of cell Proteins make up channels of cell membrane The Nucleus The Nucleus Contains DNA of Cell; site of gene transcription Chromosomes­ contain genes and hold entire DNA sequence (23 pairs) Genes­ segments of DNA that encodes for a protein Nucleotide bases: Adenine­Thymine; Guanine­Cytosine Spells out in nucleic acid the protein sequence Messenger RNA (mRNA) Transcription­ to copy the genetic code Carries genetic info to ER for protein production Transcription Transcription Process of transcribing DNA into RNA sequence. Uses complementary language, the info is simply copied, from one molecule to the other. Endoplasmic Reticulum Endoplasmic Reticulum Site of protein synthesis mRNA sent to ribosome (on ER) for genetic code reading Translation The ribosome translates the mRNA bases into sequence of amino acids Proteins: long chains of amino acids Fig. 3­17 Golgi Bodies and Microtubules Golgi Bodies and Microtubules Golgi wrap proteins in membranes (vesicles) that indicate where they end up Microtubules carry proteins to destination Fig. 3­21 Proteins make up channels of cell Proteins make up channels of cell membrane The Genetics of Behavior The Genetics of Behavior Both genes and environment interact to shape human behavior. The fundamental issue: how much of a role do genetics play in shaping human behaviors? Ex’s: psych disorders, weight gain, personality, sexual orientation? Chromosome and Genes Chromosome and Genes Genes are basic units of heredity on chromosome that code for a trait (ex: eye color) Alleles are variations of genes. dominant allele shows a strong effect in either the homozygous or heterozygous condition. recessive allele shows its effect only in the homozygous condition. Each gene pair contains an allele. Genotype and Phenotype Genotype and Phenotype Genotype is the set of genes/alleles an organism carries. Ex: genotype Bb allele for brown eye color (B) and allele for blue eye color (b). Homozygous– it carries 2 of same allele (BB or bb) Heterozygous ­­ it carries 2 diff alleles (Bb or bB) Phenotype is the expression of a gene. w/Bb ­the dominant allele (B) will mask the recessive allele (b) and you will have brown eyes Genetic Mutation Genetic Mutation Mutation: alteration of an allele Defect in a Single Allele Ex. Tay­Sachs and Huntington disease Chromosome abnormalities Ex. Down’s syndrome (extra copy of #21) The Genetics of Behavior Genes do not directly produce behaviors. Genes produce proteins that increase the probability that a behavior will develop under certain circumstances. Genes can also have an indirect affect. Genes can alter your environment by producing behaviors or traits that alter how people in your environment react to you. ...
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