Neuroscience: Exploring the Brain- Chapter 2

Number of Neurons in Human Brain

Approximately 100 billion

Number of Glial Cells in Human Brain

Approximately 1 trillion

Neurons

Cells that sense changes in the environment, communicate these changes to other neurons, and command the body's responses to these sensations

Glia/Glial Cells

Insulate, support, and nourish neighboring neurons

Compound Micrscope

Allowed for study of cellular neuroscience due to small size of neurons

Fixation/Microtome

Fixation in formaldehyde allowed for strengthening of brain tissue and microtome allowed for cutting of brain into thin slices

Histology

Microscopic study of the structure of tissues

Nissl Stains

Class of basic dyes that would stain nuclei of all cells and clumps of material surrounding the nuclei of neurons

Nissl Bodies

Clumps of material surrounding nuclei which are stained by Nissl Stain (Rough endoplasmic reticulum)

Uses of Nissl Stain

(1) Allow for differentiation of neurons and glia

(2) Allow for study of cytoarchitecture

Cytoarchitecture

arrangement of cells

Golgi Stain

Stain consisting of silver chromate solution which darkened the color of neurons in their entirety

Cell Body/Soma/Perikaryon

Swollen region of neuron which contains the cell nucleus

Neurites

Thin tubes which radiate away from the soma

Axon

Single structure extending from cell body with uniform diameter and branches (if branches occur) that extend at right angles; typically have long length (can be up to 1 meter)

Dendrites

Shorter branches (2 mm) which extend from cell body and taper into fine points; typically near axons

Golgi's View on Neurons

Believed that neurons violated cell theory and were a system fused together to form a continuous reticulum

Cajal's View on Neurons

Believed that neurons are not continuous and that they communicate by contact, not continuity

Neuron Doctrine

Idea that the neurons satisfied cell theory

Limit of Resolution of Human Eye

0.1 mm or 100 um

Neuronal Membrane

Structure which lays over the internal scaffolding of the neuron and separates the inside of the neuron from the outside

Cytosol

Salty, watery fluid in cell which is potassium rich and separated from the outside by the neuronal membrane

Organelles

Membrane-enclosed structures which lie in the soma

Cytoplasm

Everything within the cell membrane including the organelles, but excluding the nucleus

Nucleus

Spherical, centrally located, 5-10 um organelle contained in the cell body

Nuclear Envelope

Double membrane in which the nucleus is enclosed

Nuclear pores

Pores measuring 0.1 um which perforate the nuclear envelope through which mRNA travel to the cytoplasm

Chromosomes

46 structures found in the nucleus which contain genetic material (DNA)

Deoxyribonucleic Acid (DNA)

Double-stranded braid, 2 nm wide, found in the chromosomes

Genes

Specific segments of DNA which are used to assemble specific cells (ie. neuronal cells have different genes for assembly than liver cells)

Gene Expression

Reading of the DNA

Proteins

Structures existing in wide variety of shapes and sizes, and perform many different functions

Protein Synthesis

Assembly of protein molecules occurring in the cytoplasm

Messenger Ribonucleic Acid (mRNA)

Intermediary which carries genetic message from the nucleus to sites of protein synthesis in specific chain sequences of nucleic acids

Transcription

Process of assembling pieces of mRNA that contains gene information

Transcript

Resulting mRNA following transcription

Promoter

Section of DNA which does not encode for protein but is the region where RNA polymerase binds to initiate transcription

Transcription Factors

Proteins which regulate the binding of RNA polymerase to the promoter

RNA Polymerase

RNA synthesizing enzyme

Terminator

End-point for transcription recognized by RNA polymerase

Introns

Interspersed regions of DNA within the gene itself which cannot be used to code for proteins

Exons

Coding sequences in a gene

RNA Splicing

Process in which the introns are removed and exons are fused together

Alternatively Spliced mRNA

Specific exons are removed with introns giving a different mRNA and different protein

Amino Acids

Building blocks of proteins of which there are 20 kinds

How are proteins assembled?

By linking together amino acids

Translation

Assembling of proteins under direction of mRNA

Molecular Biology

Study of the process in which DNA is turned into proteins

Central Dogma of Molecular Biology

Molecular Neurobiology

Use information contained in genes to determine the structure and function of neuronal proteins

Rough Endoplasmic Reticulum

Enclosed stacks of membrane, also known as Nissl bodies, dotted with ribosomes; found a lot in neurons more than glia; major site of protein synthesis in neurons