Neuroscience: Exploring the Brain: 2

Glia/Glial Cells

Contribute to brain function mainly by insulating, supporting, and nourishing neighboring neurons

Dendritic Tree

Dendrites of a single neuron

Anterograde Transport

kinesin moves material only from the soma to the terminal. this is that movement

Pyramidal Cell

looks like an upside down tree.

Smooth Endoplasmic Reticulum

looks like rough ER without the ribosomes, performs with rough ER in some areas, some play no direct role in processing of protein molecules and instead regulate the internal concentrations of substances such as calcium.

mRNA

messenger ribonucleic acid: DNA never leaves nucleus, so something has to carry the material to the sites of protein synthesis in the cytoplasm. consists of 4 different nucleic acids strung together.

Multipolar

most neurons in the brain have many neurites

Astrocytes

most numerous glia in the brain; fill in the spaces between neurons. this space is only about 20 nm wide. probably influence whether a neurite can grow or contract. also have special proteins that can actively remove many neurotransmitters from syn cleft. also tightly control extracellular concentration of several substances having the potentiol to interfere w proper neuronal function.

Axoplasmic Transport

movement of material down the axon.

Node of Ranvier

myelin sheath is interrupted periodically, leaving a short length where the axonal membrane is exposed.

Unipolar

neuron that has a single neurite

Interneurons

neurons that only form connections with other neurons; this is true for most neurons in the body.

RNA Splicing

introns are removed and the remaining axons are fused together

Classify the cortical pyramidal cell based on (1) the number of neurites (2) the presence or absence of dendritic spines, (3) connections and (4) axon length

1) single neurite, two neurites, three neurites=unipolar, bipolar, multipolar 2)If they have dendrites, they are aspinous. If not, spiny 3)Primary sensory neurons: cells with connections to the sensory surfaces of the body Motor Neurons: axons that form synapses with the muscles and command movements Interneurons: neurons that only form connections with other neurons; this is true for most neurons in the body. 4) Golgi type 1/ projection neurons: Neurons that have long axons that extend from one part of the brain to the other Golgi type 2/ local circuit neurons: short axons that do not extend beyond vicinity of cell body

How does the cytoplasm of the axon differ from the axon?

1)microtubules do not extend into the terminal; 2)terminal contains small bubbles of membrane called synaptic vesicles, measuring 50 nm in dia; 3)inside surface of membrane facing sunapse covered in proteins; 4) numerous mitochondria indicating high energy demand.

Microtubules

20 nm in diameter; run longitudinally down neurites. appears as a straight, thick hollow pipe . Strandds braided like rope around hollow core.

Microfilaments

5 nm in diameter; about the same thickness as the cell membrane. Braids of thin strands of the protein actin

Promoter

At one end of the gene, the region where the RNA syntehsizing enzyme, RNA polymerase, binds to initate transcription

Axon Hillock

Begins the axon, and tapers to form the initial segment of the axon proper. 2 features differentiate the axon from the soma: 1)no rough er extends into the axon, and there are few if any ribosomes. 2) the protein composition of the axon membrane is fundamentally different from that of the soma membrane.

Golgi Stain

By soaking tissue in a silver chromate solution, a small percentage of neurons became darkly colored in their entirety. This revealed that the neuronal cell body, the region of the neuron around the nucleus that is shown with the Nissl stain, is actually only a small fraction of the total structure of the neuron.

Innervation

Innervate the cell; when a neuron makes contact with a cell

Retrograde Transport

Movement from terminal to soma. The protein that helps is dynein

What is myelin? What does it do? Which cell provide it in the central nervous system?

Myelin refers to layers of glial membrane that insulate axons. Myelin speeds the propagation of nerve impulses down the axon. The oligodendroglial cells provide myelin in the central nervous system.

Neuron Doctrine

Neurites of different neurons are not continuous with one another and must communicate by contact, not continuity.

State the neuron doctrine in a single sentence. To whom is the insight credited?

Neurites of different neurons are not continuous with one another and must communicate by contact, not continuity. This is credited to Santiago Ramon y Cajul

Rough Endoplasmic Reticulum/Rough ER

Not far from the nucleus, abounds in neurons, for more than in glia or most other non-neuronal cells. aka nissl bodies.

What are the steps by which the information in the DNA of the nucleus directs the synthesis of a membrane-associated protein molecule?

Protein synthesis, the assembly of protein molecules, occurs in the cytoplasm. The DNA never leaves the nucleus. The intermediary that carries the genetic message to the sites of protein synthesis in the cytoplasm is a long molecule called messenger ribonucleic acid, mRNA. The process of assembling a piece of mRNA that contains the information of a gene is called transcription and the resulting mRNA is called the transcript. Messenger RNA transcripts emerge from the nucleus through pores in the nuclear envelope and travel to ribosomes, the sites of protein synthesis in the cytoplasm. At these sites, protein molecules are assembled by linking individual amino acids into a chain. Amino acids of 20 different kinds are the building blocks for protein. Amino acids are brought to the ribosome by transfer RNA (tRNA). The assembling of proteins from amino acids under the direction of the mRNA is called translation.

Golgi Apparatus

Stack of membrane enclosed discs in the soma that lies farthest from the nucleus. Site of extensive post translational chemical processing of proteins. One function is the sorting of certain proteins that are destined for delivery to different parts of the neuron, such as axons and dendrites.

Which parts of a neuron are shown by a Golgi stain that are not shown by a Nissl Stain?

The Golgi stain shows the neuronal cell body with the dendrites and the axon. The Nissl stain shows only the cell body.

What are the three physical characteristics that distinguish axons from dendrites?

The cell body usually gives rise to a single axon while many dendrites extend from the cell body. The axon is of uniform diameter throughout its length while dendrites rarely extend more than 2 mm in length. The branches of an axon generally extend at right angles while dendrites generally taper to a fine point.

Of the following structures, state which ones are unique to neurons and which are not: nucleus, mitochondria, rough ER, synaptic vesicle, Golgi apparatus.

The synaptic vesicle is unique to neurons whereas the nucleus, the mitochondria, the rough ER, and Golgi apparatus are not unique to neurons.

Colchicine is a drug that causes microtubules to break apart or depolymerize. What effect would this drug have on anterograde transport? What would happen in the axon terminal?

Vesicles containing molecules needed at the axon terminal "walk down" the microtubules within the axon on "legs" provided by a protein called kinesin. The process is fueled by ATP. Kinesin moves material only from the soma to the terminal. Movement in this direction is called anterograde transport. The application of colchicines causes microtubules to disintegrate and when applied to the axon disrupts the path for anterograde transport. As a result, all movement of material from the soma to the terminal (anterograde transport) ceases. If the colchicines application does notkill the whole cell, then the material to be transported will accumulate on the side of the axon closest to the soma.

Tubulin

What the strands in microtubules are made of. A protein. Tubulins stuck together like pearls.

Nissl Stain

a class of basic dyes would stain the nuclei of all cells and also stain clumps of material surrounding the nuclei of neurons. These clumps are Nissl Bodies.

Translation

assembling of proteins from amino acids under the direction of the mRNA

Microtubule Associated Proteins (MAPS)

a class of proteins that participate in the regulation of microtubule assembly and function

Organelles

a number of membrane-enclosed structures

Wallerian Degeneration

axons cannot be sustained when separated from their parent cell body.

Motor Neurons

axons that form synapses with the muscles and command movements

Amino acids

building blocks for protein

Primary Sensory Neuron

cells with connections to the sensory surfaces of the body

Ribosomes

dense globular structures; measure about 25 nm in diameter

DNA

deoxyribonucleic acid.

Receptors

detect the neurotransmitters in a synaptic cleft. specialized proteins

Neurotransmitter

electrical impulse carried down the axon is converted into a chemical signal as it crosses the synapse; in the postsynaptic membrane it is again converted to an electrical impulse. neurotransmitters are the chemical part.

Axon Terminal

end of the axon (beginning: hillock; middle: proper); Axon comes into contact wth other cells/neurons here.

Cytoplasm

everything contained inside of the cell membrane, including the organelles but excluding the nucleus

Proteins

final product of gene expression, synthesis of molecules

Bipolar

if there are two neurites

Mitochondrion

important organelle in the soma. sausage shaped structures about 1 um in length. Inside their outer membrane are folds of inner membrane called cristae, and between the cristae is an inner space called matrix. site of cellular respiration. when it inhales, it pulls in pyruvic acid and oxygen amd goes into krebs cycle

Neurofilament

intermediate in size between microtubules and microfilaments. Exist in all parts of the body as intermediate filaments.

Intron

interspersed regions of DNA that cannot be used to code for protein, and the coding sequences are called exons.

Axon

only one in each cell body, uniform diameter, and if it branches, the branches extend at right angles. Axons = wires throughout the body

Microglia

phagocytes to remove debris left by dead or degenerating neurons and glia.

Synapse

point of contact between terminal and other cell; this is where info is passed

Polymerization

process of joining small proteins together

Ependymal Cells

provide the lining of fluid fuilled ventricles within the brain; also play role in directiing cell migration during brain development.

Gene Expression

reading of the DNA

Dendritic Spines

receive some types of synaptic input. Look like little punching bags that hang off the dendrite.

Cytoskeleton

scaffolding that gives the neuron its characteristic shape. the bones of it are the microtubules, microfilaments, and neurofilaments. Very likely moving around.

Genes

segments of DNA

Neurons

sense changes in the environment

Neuronal Membrane

serves as a barrier to enclose the cytoplasm inside the neuron and to exclude certain substances that float in the fluid that bathes the neuron. membrane is about 5 nm thick and studded with proteins.

Recurrent Collaterals

sometimes a branch will return to the same cell or or with the dendrites of neighboring cells

Synaptic cleft

space between presynaptic and postsynaptic membrane

Polyribosomes

sseveral free ribosomes may appear to be attached by a thread of a single strand of mRNA.

Stellate Cells

star shaped

Cytoarchitecture

the arrangement of neurons in different parts of the brain.

ATP (adenine triphosphate)

the cell's energy source. when mitochondrion exhales, 17 atp molecules are released for every molecule of pyruvic acid. atp is used to fuel the biochemical reactions of the neuron.

Myelin Sheath

the insulation from glia (myelin is a kind of membrane)

Histology

the microscopic study of the structure of tissue

Transcription

the process of putting together a piece of mRNA that contains the info

Soma/Cell Body/Perikaryon

the swollen region containing the cell nucleus

Axon collateral

these are the branchs of the axon.

Transcription Factors

these are the proteins that tightly regulate the binding of the polymerase to the promoter

Ogliodendral and Schwann cells

these glia provide layers of membrane that insulate axons.

Neurites

thin tubes that radiate away from the soma, have two types: axons, dendrites

Synaptic Transmission

transfer of info from one neuron to another

Dendrites

usually no more than 2 mm in length. Taper to a fine point. Act as the antennae o the neuron to receive incoming signals.

Cytosol

watery fluid inside the cell. Salty, potassium rich solution that is separated from the outside by the neuronal membrane.

Terminal Arbor

when synapses are in the same region

Chromosomes

within the nucleus, contain the genetic material, DNA