NRSC 1110- Chapter 2- Neurons and Glia

Neurons

Neurons

sense changes in the environment, communicate these changes to other neurons, and command responses to these sensations

Glia

help brain functions by insulating, supporting and nourishing neurons.

development of neuroscience pre modern science

could not develop due to small size of neurons

why are stains important

stains help distinctively depict structures.

Nissil stain

shows the nucleus and soma of a neuron. Showed the arrangement of neurons in different parts of the brain (cytoarchitecture). Stains all neurons in sample

Golgi stain

silver chromate solution. Only makes a small part of neurons stained and depicted, increasing detail and labels neurons in its entirety (cell body and neurites)

Neurites

axon and dendrites

axon

uniform; carry output information (can extend long distances)

dendrites

receive sensory information

Cajal

Used the Golgi stain to explain the circuity in neuroscience.

Golgi’s belief

believed neurites formed a continuous reticulum like that of the circulatory system

Golgi’s belief and cell theory

does not align with cell theory

Cajal’s belief

argued in non-continuity of neurons and communicate by contact. Electron microscope proved him right (1950s)

Cajal’s belief and cell theory

applies the cell theory, which is now known as the neuron doctrine.

cell theory

cells are the elementary unit of tissues

neuron doctrine

the fundamental structural and function unit of the CNS is the neuron

neurons are discrete cells connected but not continuous with other cells

neurons are composed of three parts: dendrite, axon, cell body

information flows along the neuron in one direction (dendrite—> soma—> axon)

Soma

also known as ell body; contains cytosol and organelles, surrounded by the neuronal membrane

nucleus

contains chromosomes which hold genetic material

genetic material

DNA and RNA

is DNA the same everywhere

yes

Why are different cells different?

cells have the same DNA but different parts are turned on or turned off

gene expression

reading of DNA to make proteins

Transcription

making of mRNA from DNA which serves as an intermediate step for protein synthesis

When does transcription start

promoter

enhancers

distal regulatory sequences that help with transcription

transcription factors

help regulate transcription. Bind to enhancers

RNA splicing

when introns are cut out of exons

alternative splicing

when exons are also cut out which lead to different expression

Translation

using mRNA to create amino acids

Central dogma of molecular biology

DNA—> mRNA—> protein

Disease formation

errors in genes; either due to mutations, or overexpression of genes or underexpression of genes

Knockout mice

gene has been deleted. Used to study disease progression

transgenic mice

mice that have transgenes or genes that have been introduced or over expressed

knock in mice

replacement of a genetic material using a transgene.

Rough er

has ribosomes attached which allows for protein synthesis to happen.

Nissil bodies

Ribosomes that are attached to the ER.

polyribosomes

ribosomes that are not attached to the ER aka free ribosomes

free ribosome protein destination

the protein is released within the cytosol

attached ribosome protein destination

membrane of cell or to an organelle

smooth er

function depends on place but the two functions include: folding proteins, regulate concentrations of substances.

Golgi apparatus

sorts delivery of proteins to different parts of the neuron. Post translational chemical processing

Mitochondria

foldings within it are called cristae and it has an inner space called the matrix. Site of cellular respiration which makes ATP

Neuronal membrane

composition differs depending on what part of the neuron is present

cytoskeleton

gives architectural support/structure of the neuron

microtubules

20 nm, consists of tubulin. Depolymerization and polymerization of neurons determine shape. (biggest in size)

MAP proteins

microtubule associated proteins that anchor microtubules to one another in various parts of the neuron

Microfilaments

made from actin and are important in changing the shape of neuron (smallest in size)

Neuronal filaments

intermediate filaments (intermediate in size) structural role.

Axon

has no rough ER. few or no free ribosomes

axon vs soma

the protein content is different

axon hillock

beginning of the axon

axon collateral

branching of axons that communicate with other parts of the nervous system

recurrent collateral

axon collateral returns to communicate with the same cell that gave rise to the axon or with dendrites of neighboring cells

thickness of axon

faster nerve impulse

axon terminal

end of axon; site where axon comes into contact with other neurons

difference between axon terminal and axon

microtubules don’t extend there, has synaptic vesicles, dense with proteins, a lot of mitochondria

synapse

where the axon of one neuron meets the dendrite of another. There is a presynaptic side and a post synaptic side. The post synaptic side has vessicles filled with neurotransmitters, chemicals that relay information

Wallerian degeneration

when axon are removed from the body; occurs when flow of materials to the soma are cut off

axoplasmic transport

material down the axon via the soma; divided into slow and fast

anterograde transport

kinesin “walks” along microtubules to bring materials from the soma to the axon.

retrograde transport

dynenin “walks” along microtubules to bring materials from the axon to the soma

Classification of neurons: neurite number

unipolar, bipolar, multipolar

unipolar

one neurite

bipolar

two neurites

multipolar

more than two neurites

Classification of neurons: shape of dendrites

stellate and pyramidal

stellate cells

star shaped, can be aspinous or spiny

pyramidal cells

pyramid shaped, always spiny

Classification of neurons: connections

sensory neurons, motor neurons, interneurons

Sensory neurons

sensory input to neurons

motor neurons

handle movement

interneurons

make connections with other neurons

Classification of neurons: axon length

golgi type 1, golgi type 2

Golgi type 1

projection neurons, have long axons

Golgi type 2

local circuit neurons, have short neurons

Classification of neurons: neurotransmitter

cholinergic, glutameric, dopaminergic

cholinergic

releases AcH into sacroplasmic reticulum

glumateric

releases glutamine

dopaminergic

releases dopamine

astrocytes

numerous glia in the brain, envelop synapses, responsible for neurotransmitter reuptake, K+ spatial buffering, influence neurite growth (have scaffolds for growing axons), blood brain barrier

myelinating glia

myelin sheath for insulating axons, Schwann cells and oligodendrocytes

Schwann cells

in PNS, single axon myelinated

Oligodendrocytes

in CNS, myelinate several axons

Microglia

respond to insult or injury in the CNS. “Immune system of the brain”, act as phagocytes for the brain

Ependymal cells

ventricular system of the CNS, produce CSF

Gray matter

neurons and glia

white matter

myelinated axons of neurons (also neurons and glia)

cns

a central division consisting of the brain and the spinal cord

pns

a peripheral division consisting of the network of nerves that course through the body

periphernal nerves contain sensory and motor function. what are they?

efferent, motor and afferent, sensory

afferent

typically information going from the peripheral nerves to the CNS usually sensory

efferent

information going out of the spinal cord or CNS to peripheral nerves, usually motor

how many lobes does the brain have?

4

lobes of the brain

frontal lobe, parietal lobe, temporal lobe, occipital lobe

gryi

bumps in brain

sulci

grooves

cerebral localization

different functions for different lobes and gyri

Primary cortical areas

1 degree cortical area that receives data, receives inputs that are relayed to cortex throught he thalamus

differences between dendrites and axons (dendrites)

short, stubby, often spiny

highly branched tree

very tapered as it goes further from soma

differences between dendrites and axons (axons)

long, thinner, smooth

fewer branches,

diameter is more uniform