Ch. 2 Cells of the Nervous System (based from review guide)

2 major nerve cell types

neurons and glia

neuron function

transmit information (electrical/chemical) over long distances

glia function

provide physical support to neurons, maintain CNS, environment, transmit information, and provide immune function

Nissil stain

stains Nissil bodies; general look of neuron; less detailed; tells if cell is alive or dead

Golgi stain

more detailed; stains entire neuron but not all neurons

T or F: you can study an unstained brain

false

T or F: Both Nissil and golgi stains are used for visualizing neuronal structures

true

Neuron doctrine

concept that the nervous system is made up of discrete individual cells

who coined the term neuron and came up with neuron doctrine?

Waldeyer-Hartz

was the neuron doctrine fully validated after being named by Waldeyer-Hartz in 1891?

no the neuron doctrine wasn’t fully validated until 1955 when the synapse was captured on electron microscope

cell body

most prominent part of the neuron

what does the cell body of a neuron contain?

1. nucleus (surrounded by nuclear membrane

2. Specialized structures called organelles

Other names for the cell body

soma, perikaryon

organelles to know

1. cell membrane

2. cytoplasm

3. mitochondrion

4. nucleus

5. ribosome

6. endoplasmic reticulum

7. golgi apparatus

cell membrane function

protects the cell

cytoplasm function

cell buffer

mitochondrion function

generates energy (ATP), involved in signaling, cellular differntiation, cell death, maintain control of cell cycle/cellular growth

nucleus function

contains genetic material

rough endoplasmic reticulum function

makes proteins

smooth endoplasmic reticulum function

makes lipids, folds proteins, regulates calcium

golgi apparatus function

modifies, packages, and transports lipids and proteins

which organelles are not present throughout the entire neuron?

nucleus and rough endoplasmic reticulum

T or F: mitochondria are found throughout the entire neuron

true

where are mitochondria concentrated?

in pre and post synaptic neuron

T or F: each neuron contains the same genetic code, but uses the genetic code differently to make different proteins

true

nucleotide

molecule consisting of a nitrogen-containing base, a phosphate group, and a sugar that forms the basic structural unit of a nucleic acid

genes

segment of DNA that codes for the manufacture of a specific protein

DNA

molecule that carries genetic instructions for the development and functioning of all organisms and some viruses

chromosomes

long strands of DNA

transcription steps

1. RNA polymerase, with the help of transcription factors, binds to a specific sequence within a gene (the promoter) and splits the two strands of DNA apart

2. One strand is the template strand that RNA polymerase moves down to synthesize mRNA

3. Once RNA polymerase reaches the end of the gene termination occurs. This is when the enzyme detaches from the gene and the DNA is returned to its original state.

4. mRNA leaves the nucleus of the cell and moves into the cytoplasm where it will find a free ribosome.

exons

coding regions on pre-mRNA

introns

noncoding regions on pre-mRNA; cut out of the RNA strand during splicing after transcription has occurred

T or F: introns are included in mRNA

false

T or F: 1 section of a gene can make a variety of different proteins by splicing exons together differently

true

different types of ribosomes

1. attached

2. detached

3. poly

steps of translation

1. mRNA codon (3 nucleotides) will pair with a specific transfer RNA (tRNA) anticodon

2. Each tRNA anticodon is linked to an amino acid

3. As the process continues down the mRNA, ribosomes link the amino acids together forming a polypeptide chain

4. Once completed the polypeptide chain folds into a protein and exits the ribosome (or the polypeptide chain can exit the ribosome and then fold into a protein)

T or F: Proteins can be made of one or more polypeptides

true

protein folding after translation

1. this process involves four stages (primary, secondary, tertiary and quaternary structure) that gives rise to various 3D protein structures

2. amino acid sequence accounts for diff conformations

T or F: Some neurological impairments arise as a result of protein production problems or protein misfolding

true

T or F: smooth ER is not found throughout all parts of the neuron

false

neurons contain _____ amounts of endoplasmic reticulum

large

where is rough ER found in neurons?

mostly cell body and dendrites (little to no amount in axons)

cytoskeleton function

gives a neuron its characteristic shape

what 3 structures make up the cytoskeleton (in order of size largest to smallest)

1. microtubules

2. neurofilaments

3. microfilaments

protein that makes up microtubules

tubulin

microtubule associated proteins (MAPs)

proteins that interact with tubulin and microtubules to regulate their function and transport cargo; anchor neurons to one another and other parts of the neuron

microtubules are involved in ______-range axoplasmic transport

long

T or F: microtubules are not static and can change (lengthen/shorten) as the neuron changes

true

MAP protein Tau

when Tau becomes misfolded this leads to Alzheimers disease. Misfolded Tau causes breakdown of microtubules and eventually axon/neuron death

neurofilament protein

intermediate filament

neurofilament function

important for structure, shape, space filling (fill axons which increases connections/communication between neurons. increased filling also increases axon diameter and this leads to faster signaling)

neurofilaments move _________ along microtubules

bidirectionally

another name for neurofilaments

intermediate filaments

T or F: neurotubules have tracks for transport

false

another name for microfilaments

actin filaments

microfilament protein

actin

T or F: microfilaments are not static and can change (lengthen/shorten) as the neuron changes

true

microfilaments are involved in ______-range axoplasmic transport

short

____ is one of the most abundant proteins in cells of all types and plays a role in changing ____ shape (usually muscle contraction)

Actin; cell

T or F: microtubules extend all the way to the axon terminal

false

dendrites

projections that receive chemical signals (neurotransmitters) from other nerve cells

axon

slender projection that conducts the action potential

how many axons are there per neuron? how long is an axon?

1; long

how many dendrites are there per neuron? how long is a dendrite?

many; short

2 types of neurites

1. dendrites

2. axons

axon hillock

portion of the axon adjacent to the cell body that generates the action potential

axon collaterals

axons that split into numerous branches (how signal travels to other neurons)

axon varicosities

swellings that release NT along length of an axon

axon terminal

small enlargement at the end of an axon that stores and releases neurotransmitter

T or F: axons and dendrites are continuous (connected)

false

Wallerian degeneration

an active process of degeneration that results when a nerve fiber is cut which causes death to an axon distal to the injury

what kind of axons did Wallerian damage

frog axons

retrograde degeneration

injury occurs close to the cell body; neuron dies because damage moves backwards from site on injury to the soma

anterograde regeneration

injury occurs close to the axon terminal; neuron can regenerate because damage moves forwards from site of injury away from the soma

which MAP is responsible for anterograde transport?

MAP Kinesin

which MAP is responsible for retrograde transport?

MAP Dynein

anterograde transport

newly synthesized proteins are packaged in the soma and transported toward the axon terminal

retrograde transport

vesicles, organelles, and signaling molecules are carried from the axon terminal to the cell body for recycling

what uses slow axoplasmic transport?

cytosolic and cytoskeletal proteins

T or F: slow axoplasmic transport gets its name because the speed/rate of transport is slower than fast axoplasmic transport

F: slow axoplasmic transport runs at the same speed/rate as fast axonal transport but it makes more stops

what uses fast axoplasmic transport?

synaptic vesicles, membranous organelles, and proteins

synapse (synaptic cleft)?

the space between two signaling cells (presynaptic and postsynaptic)

synaptic transmission is mediated _______

chemically

where do many drugs act?

at the synapse

malfunctions at the ________ are responsible for many mental disorders

synapse

unipolar

one nerve process that extends from the cell body (axon that extends into dendrites, sensory ganglia, and dorsal root ganglia)

bipolar

two structures extending from the cell body (ex: retina, olfactory bulb)

multipolar

many dendrites; single axon (most neurons are this type)

how can neurons be classified?

1. number of neurites (unipolar, bipolar, multipolar)

2. shape of dendritic tree

3. connectivity (sensory, motor, interneurons)

4. axon length (golgi type I and II)

5. neurotransmitters released

6. gene expression

shape of dendritic tree

1. pyramidal cells (all spiny); most cells are this

2. stellate cells (some spiny, some aspinous)

sensory neurons

gather information from the sensory receptors and carry that information to the brain

interneurons

small neurons that connect other neurons to each other CNS

motor neurons

receive information from the brain and carries signals to muscles

golgi type 1 (projection neurons)

long axons; extend between brain regions, mostly pyramidal cells

golgi type 2 (local circuit neurons)

short axons; connect to neurons in vicinity; mostly stellate cells

neurotransmitter types

1. acetylcholine

2. glutamate

3. GABA

4. serotonin

5. dopamine

6. opioids

7. peptides

gene expression to classify neurons

can use RNA sequencing to identify genes expressed in certain neuron populations; neurons have their own specific combo of genes

neuroglia function

support neuron functioning, have signaling capabilities, supports synapse formation, and some can function as stem cells

neuroglia types

1. astrocytes

2. oligodendrocytes

3. schwann cells

4. microglia

5. radial glia & ependymal cells

2 most abundant neuroglia

astrocytes and oligodendrocytes