Neurons are brain cells that senses changes in the environment, communicate changes, and command's the body to respond.
What are Glial Cells (Glia)?
Glial cells are ten times more abundant than neurons. They are thought to:
What is histology?
Histology is the microsopic study of tissues.
What is the Nissl Stain? Why was it important?
The Nissl Stain refers to the method of staining the nuclei of cells in order to study it. It was named after the German Neurologist Franz Nissl.
The Nissl stain distinguished neurons and glia from one another.
The Nissl stain also enabled histologist to study the arrangements of neurons in different parts of the brain.
What is Cytoarchitecture?
Cytoarchitecture is the study of the arrangement of cells.
Who is Camillo Golgi? What is the Golgi Stain? What is the Reticular Theory?
Golgi was an Italian histologist who discovered that soaking brain tissue in a silver chromate solution wll darken a small percentage of the neuron in its entirety.
The Golgi Stain is a silver chromate solution that stains neurons in its entirety (including neurites).
The Reticular Theory was the theory Golgi championed that believed the brain was an exception to the Cellular Theory. The Reticular Theory believed that the neurites of different cells are fused together to form a continuous reticulum or network (similar to arteries).
Who is Santiago Ramon y Cajal? What is the Neuron Doctrine?
Cajal was a Spanish histologist and artist that ended up illustratining the many circuitry of the brain using the Golgi Stain.
Cajal championed the Neuron Doctrine where the neurities of different neurons are not continuous with one another and must communicate by "contact" and not continuity. Cajal was correct.
What is the Soma? Cytosol? Cytoplasm? Organelles?
The Soma or Perikaryon is the cell body and it contains the cell nucleus.
The Cytosol is the watery fluid inside the cell that is composed of potassium-rich solution that is separated from the outside by the nueronal membrane.
The Cytoplasm is everything that is contained within the cell membrane, including organelles, except the cell nucleus.
Organelles are membrane-enclosed structures inside the Soma, i.e. Rough Endoplasmic Reticulum, Mithochondria, Golgo Apparatus, etc.
What is the Nucleus? What function does it play? What is DNA?
The Nucleus is a double membrane structure located roughly at the center of the Soma where DNA is stored and where mRNA is synthesized.
DNA is deoxyribonucleic acid and contains information on how to build proteins.
What is Transcription?
What is a Transcript?
What is Translation?
Transcription is the process of assembling a piece of mRNA that contains gene information.
A Transcript is a resulting mRNA after transcription.
mRNA is Messenger Ribonucleic Acid and is an intermediary that carries the genetic message to the sites of protein synthesis.
Translation is the process of assembling of proteins from amino acids under the direction of the mRNA.
What are the various types of Organelles?
What are their functions?
The major Organelles are Rough Endoplasmic Reticulum, Ribosomes, Smooth Endoplasmic Reticulum, and the Golgi Apparatus.
The Rough Endoplasmic Reticulum are enclosed stacks of membrane dotted with Ribosomes and is a major site of protein synthesis.
Ribosomes translates the instruction contained in the mRNA to assemble a protein molecule. Free Ribosomes are freely floating ribosomes not attached to the Rough ER and makes proteins that stay inside the cytosol of the neuron. Another type of Ribosome is the Polyribosome which is a free ribosome that appears to be attached to a thread that is an mRNA.
The Smooth ER is a stack of membrane that does not have ribosomes and performs different functions depending on its location.
The Golgi Apparatus is located furthest away from the Nucleus and is involved with "post-translational" chemical processing of proteins.
The Mitochondria is the site of cellular respiration; it is the energy source. The mithochondria takes in pyrufic acid and oxygen that floats in the cytosol and exhales 17 Adenosine Triphosphate (ATP) molecules for every molecule of pyruvic acid.
What is the Neuronal Membrane?
The Neuronal Membrane serves as a barrier that encloses the cytoplasm and excludes other substances that float in the fluid that bathes the neuron.
What are Axons? How is it different from the Soma?
Axon Terminal? What is a Synapse? What is Innervation?
How is the Axon Proper different from the Axon Terminal?
Axons are a type of neurites or a tube shaped structures that extends from the Soma. Axons do not contain any Rough ER and have few Free Ribosomes, which means the protein composition of the Axon is different from the Soma.
Axon Hillock refers to the initial segment of the axon proper; the segment that is immediately attached to the Soma.
The Axon proper is the middle of the axon.
Axon Terminal or the terminal bouton is the end of the axon and is the site that comes in contact with other neurons and passes information. The Synapse is the point of contact between an axon terminal and receptors. When a neuron makes synaptic contacts with another neuron, it is called innervation. The cell that receives the information is said to be innervated.
The Microtubules do not extend in the Axon Terminal; the Terminal contains Synaptic Vessicles; the Terminal has a dense covering of proteins; the Terminal also contains many mithochondria which indicates a high energy demand.