NSC Exam 1

neurons

sense changes in the environment, communicate these sensations

glia

contribute to brain function by insulating, supporting, and nourishing

histology

microscopic study of the structure of tissues

the neuron docterine

cell theory also applies to neurons

Nissl stain

clumps of Nissl bodies, distinguishes between neurons and glia and enables the histologists to study the arrangement

cytoarchitecture

arrangement of neurons in different parts of the brain

golgi stain

soaking brain tissue in a silver chromate solution, makes a small percentage of neurons become darkly colored in their entirety

Cajal

skilled histologist, used golgi stain to work out the circuitry of many regions in the brain

cytosol

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

organelles

membrane enclosed structures inside of the soma

cytoplasm

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

nucleus

spherical, centrally located, double membrane nuclear envelope

chromosomes

contain genetic material DNA, inside nucleus

genes

segments of DNA that are used to assemble the cell

gene expression

reading of the DNA, final product is synthesis of proteins

protein synthesis

assembly of protein molecules, occurs in cytoplasm

mRNA

intermediary that must carry the genetic messages to the sites of protein synthesis

transcription

process of assembling a piece of mRNA that contains the information of a gene, resulting mRNA called transcript

promoter

one end of the gene, region where RNA-synthesizing enzyme, RNA polymerase binds to initiate transcription

transcription factors

binding of the polymerase to the promoter regulated by this protein

RNA splicing

introns are removed and the remaining exons are fused together

amino acids

building blocks of protein, 20 different kinds

translation

assembling of proteins from amino acids under the direction of mRNA

central dogma

dna-(transcription)-mRNA-(translation)-protein

genome

entire length of DNA that comprises the genetic information our genome

genetic engineering

ways to change organisms by design with gene mutations or insertions

knockout mice

one gene has been deleted

transgenic mice

genes have been introduced and overexpressed

knock-in mice

native gene is replaced with a modified transgene

smooth ER

site where proteins that jut out from the membrane are carefully folded giving them their three dimensional structure

golgi apparatus

stack of membrane enclosed disks in the soma that lies farthest from the nucleus , extensive post translational chemical processing of proteins

mitochondrion

very abundant organelle in the soma

adenosine triphosphate

cell’s energy source

neuronal membrane

serves as a barrier to enclose the cytoplasm inside the neuron and exclude certain substances that float in the fluid that bathes the neuron

cytoskeleton

scaffolding that gives the neuron its characteristic shape

microtubules

run longitudinally along neurites, straight thick walled hollow pipe, pipe is composed of smaller strands that are braided like rope, each strand consists of tublin

microfilaments

same thickness as cell membrane, braids of two thin strands that are polymers of actin protein, run longitudinally along membrane, anchored to the membrane by attachments with a meshwork of fibrous proteins that line the inside of the membrane like a spider web

neurofilaments

exist in all cells as intermediate filaments, in neurons they re called…, most closely resemble bones and ligaments of the skeleton, multiple subunits/building blocks would together in a rope like structure

axon hillock

beginning of the axon, tapers away from the soma to form the initial segment of the axon proper

axon collaterals

branches on the axon, can travel long distances to communicate with different parts of the nervous system

axon terminal/terminal bouton

site where the axon comes in contact with other neurons and passes information onto them

synapse

point of contact

terminal arbor

many short branches on an axon end forming a dendrite or cell bodies in the same region

innervation

neuron makes a synaptic contact with another cell, innervates cell

synaptic vesicles

terminal contains numerous small bubbles of membrane

synaptic cleft

space between the presynaptic and postsynaptic membranes

synaptic transmission

transfer of information at the synapse from one neuron to another

neurotransmitter

chemical signal stored and released from the synaptic vesicles within the terminal

axoplasmic transport

movement of material down the axon

anterograde transport

all movement of material in this direction, soma to terminal

retrograde transport

movement from terminal to soma

dendritic tree

dendrites of a single neuron

receptors

specialized protein molecules that detect the neurotransmitters in the synaptic cleft

dendritic spines

dendrites of some neurons covered with specialized structures that receive some types of synaptic input

primary sensory neurons

cells with neurites on the sensory surfaces of the body

motor neurons

neurons with axons that form synapses with the muscles and command movementsi

interneurons

neurons that only form connections with other neurons

green fluorescent protein

encoded by a gene discovered in jellyfish, bright green, allows visualization of neuron

astrocyte

most numerous glia in the brain, fill space between neurons, essential role is regulating the chemical content of this extracellular space

oligodendroglial/schwann cells

provide layers of membrane that insulate axons

myelin

spirals around axons of the brain

node of Ranvier

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

ependymal cells

ine fluidfilled ventricles within the brain and play a role in directing cell migration during brain development

microglia

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

phospholipid bilayer

hydrophilic head face inner, hydrophobic tails face outer

peptide bonds

join amino acids

polypeptides

chain of amino acids

ion channels

made from sorts of membrane spanning protein molecules

ion selectivity

potassium channels are selectively permeable to K+, calcium to Ca2+…

gating

channels can be opened and closed by changes in local microenvironment of the membrane

ion pumps

membrane spanning proteins, enzymes that use the energy released by the breakdown of ATP to transport certain ions across the membrane

diffusion

movement of ions from high concentrations to low concentraions

concentration gradient

movement of ions across a concentration gradient, membrane channels permeable to the ions, there is a concentration gradient across the membrane

electrical current

movement of electrical charge

electrical potential (voltage)

force exerted on a charged particle, reflects difference in charge between anode and cathode

electrical conductance

relative ability of an electrical charge to migrate from one point to another

electrical resistance

relative inability of a chemical charge to migrate

ohm’s law

I=gV, current is the product of conductance and the potential difference

membrane potential

voltage across the neuronal membrane at any moment, Vm

microelectrode

thin glass tube with an extremely fine tip that can penetrate the membrane of a neuron with minimal damage

ionic equilibrium potential

electrical potential difference that exactly balances an ionic concentration gradient

Nernst equation

consideration of charge of ion, temperature, ratio of external and internal ion concentrations

sodium-potassium pump

enzyme that breaks down ATP in the presence of internal Na+, 3Na+ in, 2K+ out

calcium pump

enzyme that actively transports Ca2+ out of the cytosol across the membrane

goldman equation

mathematical formula relative permeability of the membrane to different ions

depolarization

change in membrane potential from the normal resting value to the less negative value

blood-brain barrier

specialization of the walls of brain capillaries that limits the movement of potassium into the extracellular fluid of the brain

rising phase

rapid depolarization of the membrane

overshoot

part of the action potential where the inside of the neuron is positively charged with respect to the outside

falling phase

rapid repolarization until the inside of the membrane is actually more negative than the resting potential

undershoot

last part of falling phase

threshold

critical level of depolarization that must be reached in order to trigger an action potential

optogenetics

introduces neurons foreign genes that express membrane ion channels that open in response to life

channelrhodopsin-2

photopigment, introducing ChR2 gene into mammalian cells, shows that it encodes a light-sensitive cation channel that is permeable to Na+ and Ca2+

voltage clamp

key technical breakthrough, enabled Hodgkin and Huxley to clamp the membrane potential of an axon at any value they chose

voltage-gated sodium channel

protein forms a pore in the membrane that is highly selective to Na+ and the pore is opened and closed by changes in membrane voltage

patch clamp

study ionic currents passing through individual ion channels, entails sealing tip of an electrode to a very small patch of neuronal membranec

channelopathy

generalized febrile seizures, human genetic disease caused by alterations in the structure and function of ion channels

tetrodoxin (TTX)

clogs Na+ permeable pore by binding tightly to a specific site on the outside of the channel

voltage gated potassium channels

most open when the membrane is depolarized and function to diminish any further depolarization by giving K+ a path to leave the cell across the membrane