Lecture 3
What are the Glia cells we need to know for this class (there are 6)? What nervous system are each glia cells a part of ?
(Embryonic development) Radial glia --> are known to be multi-potent stem cells that give rise to neurons and glia during development (during embryonic development they give rise to all the neurons of the cerebral cortex and astrocytes and oligodendrocytes) Slide 31 (CNS) Oligodendrocytes --> Myelinate axons in the central nervous system and can mylenate multiple axons. They form myelin sheaths Slide 34 (CNS) Microglia --> Main immune cell in the CNS and are the most abundant cell in the brain (along with astrocytes) (CNS) Astrocytes --> most abundant cell (along with Microglia) and they help form the physical structure of the brain (CNS) Ependymal cells --> Form the epithelial lining of the ventricles and produces the CSF (PNS)Schwann cells --> mylenates 1 axon in the PNS (not multi with one like oligodendrocytes)
Microglia have pattern recognition receptors on their surface. True or false
True Microglia are equipped with a group of surface receptors which triggers signals and regulates specific microglia functions.
What is the basic Structure of a neuron? What does each part do?
cell body (also called soma and perikaryon), dendrites, axon AXONS AND DENDRITES ARE TWO TYPES OF NEURITES (THIN PROCESSES THAT RADIATE OUT FROM THE SOMA) Soma is where the nucleus is located Dendrites receive incoming signals from other neurons Axons carry output signals to other neurons (there are exceptions to these rules for both axons and dendrites) slide 7
What is the neuron doctrine?
concept that the nervous system is made up of discrete individual cells Slide 3
what is the difference between a neuron and glia cell?
-Neurons carry out most of the information processing in the nervous system. -Glia cells traditionally are 'supporting cells' that carry out roles such as maintaining homeostasis of extracellular space in the brain, insulating neurons, and providing both structural and nutrient support to neurons. Slide 6
What percent of body mass is approximately the brain and it consumes roughly what percent of energy? What do neurons use to make ATP? During starvation what would the neuron use?
2% and 20% almost exclusively glucose They will use keytone bodies Slide 10
Key idea: There is a lot going on at the nerve terminal, _____(a lot/ a little) amount of energy is needed so we can ______(a lot/a little) amount of mitochondria. All signals have to be transported down the axon because __________. There are _________(none, a lot, some) translation at the nerve terminal.
A lot of energy is needed A lot of mitochondria is needed There are no free ribosomes or ER in the axon No translation happens at the nerve terminal Slide 17
Translation of information from the nucleic acid proteins: what are the two type of messenger RNA (different places they encode, what do they do)?
A) Messenger RNA that encode soluble cytoplasmic proteins are translated on free ribosomes that are not associated with the ER (free flowing in the neurolemma) B)Messenger RNA that encode membrane bound proteins are translated on ribosomes bound to the rough ER ( abundant amount of these because a lot of genes are expressed) Slide 12
Who is Santiago Ramon y Cajal and what is his relation to Camillo Golgi? When was the neuron doctrine was not confirmed (what was created)?
Cajal began using Golgi stain and developed a new interpretation of the images seen through the light microscope ---> the idea that neurons are separate cells that must communicate some way at contact points AT THIS TIME WE STILL DID NOT KNOW THAT SYNAPSES EXIST The electron microscopy slide 5
Regeneration can happen in both the PNS and the CNS True or false
False Can only happen in the PNS
Membrane bound vesicles derived from the ER contain newly synthesized proteins fused with the membrane of the ribosomes True or false
False Fused with the Golgi apparatus membrane Slide 14
Neurons in the mammalian brain communicate via gap junctions, which could functionally could be considered a disconnected reticulum. True or False
False It can be considered an interconnected reticulum.
A single oligodendrocyte can myelinated the axons of multiple neurons in the PNS True or false
False It can do this but only to neurons in the CNS
The nodes of Ranvier is about 2 mm apart true or false
False It is roughly 1mm apart anymore would make the AP weaker which we are not trying to do
Since Neurons are terminally differentiated cells, they have little need for new protein and synthesis and have relatively small amounts of rough ER. true or false
False They do not divide their cells but they do a lot of protein synthesis---> we have a lot of ER to the point where we have Nissl stain!!!
Gene expression in neurons: mature neurons can differentiate true or false? Do chromosomes replicate in mature neurons, if not what do they do then? What is different when it comes to neural protein translation?
False they are terminally differentiated They do not replicate and they function ONLY for gene transcription ---> synthesis of RNA from the DNA template THE MESSENGER RNA THEN EXPORTS FROM THE NUCLEUS TO DIRECT PROTEIN TRANSLATION BY THE ER Neurons transcribe a special set of genes to yield unique sets of neural proteins Slide 11
State the difference between action potential and graded potential.
Graded Potentials • Variable strength • Used for short distance communication • Can be hyperpolarizing or depolarizing Action Potentials • Very brief (duration is milliseconds), large depolarizations • Rapid signaling over long distances • Always depolarizing • Have a threshold (about -55 mV) Slide 22
Integration of excitatory Postsynaptic Potentials (EPSPs): What happens to the EPSP amplitude as they propagate towards the soma? What EPSP is more activating (distal or proximal)? What is spatial summation?
It decreases because a neuron is not every conductive Proximal because it is closer to the soma as appose to distal --> graded potentials are done to cause the action potential Summation are spatially distinct and two inputs are placed separately then come together for a larger response to trigger an action potential Temporal summation is one input done multiple times within a short time to achieve an action potential. Slide 27
What is the role of the microtubules? What is the role of the Actin filament? What is the role of the neurofilaments?
Microtubules are responsible for projecting(elongating) of the axons Actin filaments form short polymers that make up the leading edge of the axon that is growing (growth cone) on the microtubule THE MICROFILAMENTS ARE VERY LABILE B/C ENABLES NEURONS TO SEND OUT FILOPODIA (POLYMERIZATION) TO 'INVESTIGATE' THE ENVIRONEMENT AND TO WITHDRAW THE FILOPODIA (DEPOLYMERIZATION) BEFORE THE MICROTUBULES SOLIDIFY THE FILAMENTS neurofilaments are important for the neuron but not our focus in this course ---> abundant in axons and responsible for the maintenance of axon diameter Slide 16
Is white matter more myelinated axons or somas? What is multiple Sclerosis (MS)? What are the symptoms and What causes it? What test are done and is there a cure?
More myelinated axons (dark matter are the somas) Slide 38 A disease in the CNS where there is an extreme amount of demyelination of axons The symptoms depend on where the demyelination occurs so it could be blindness in one eye, paralysis, etc. --> it is an autoimmune disease, but it is still unknown what the immune system does to cause this disease. Blood test, spinal tap (lumbar puncture around L3-L4, MRI--> there is no cure Slide 40
what is the name of the plasma membrane of a neuron? What is so special about this plasma membrane (what is the importance)? What are the things found in the soma we need to know for this course (5 organelles we must know)?
Neurolemma Unlike most other cells, the neurolemma are crucial for the generation and transmission of electrical signals Aqueous cytosol (potassium rich salt solution), and membrane bound organelles --> mitochondria, nucleus, rough endoplasmic reticulum, smooth endoplasmic reticulum, and Golgi apparatus Slide 9
Why does Nissl stain work? What is Nissl staining?
Nissl staining is stomata staining with cresyl violet and it binds to the ribosomal RNA Can be used to mark neurons in the brain because there are so many rough ER in the soma. Slide 13
What is one hallmark of the PNS we discuss in this class? What is Wallerian degeneration? what is Bands of Bunger? Does the regeneration of the myelin sheaths look the same?
One of the hallmarks of the PNS is the regenerative process that occurs after injury to peripheral nerves. PNS nerve injury induces a complex series of cellular events that take place as the axons distal to the injury site degenerate Schwanns cells forming a unique columnar structure along the regenerating axon that is regrowing No, Axon regeneration and re- innervation is not synonymous with full physiological or functional recovery. Slide 55
What are spines (of a neuron) and where can we find them? What do they involve (language, motor)? Can protein translation happen on dendrites if they can why?
Spines are small protrusions that receive synaptic input from a single axon terminal, They are found on some dendrites They are involved with learning and memory They can because of polyribosomes associated with the spines, synaptic input can use this for protein translation Slide 19
What triggers Schwann cells to myelinate? What is the average thickness of the PNS axons?
The axon not only trigger Schwann cells to myelinate, but also determine the thickness of the myelin sheath. 0.67 (g ratio) Slide 53
What combination does dendrites use to localize polyribosomes? Spines can evolve over time (true or false)? What is the spine specialized ER and what does it store/release?
They use microtubules (for transport from soma to spine) and Actin (for transport into the spine) Spines change over time, corresponding to new synapses and lost of existing ones ---> involved with learning and memory Spinal apparatus (SA) and it stores/releases Ca2+ ---> important for synaptic plasticity Slide 19
Cytoskeleton of Neurons: What is a scaffolding structure and what is the purpose? What are the 3 scaffolding structures in neurons?What are intermediate filament?
To maintain the complex shape of the cell, an internal scaffold is necessary to provide stiffness and to serve as a 'railway' to transport vesicles Microtubules --> polymers of the tubulin protein, together with microtubule-associated proteins (MAPs) Microfilaments --> two intertwined polymer strands of the actin protein Neurofilaments --> consist primarily of proteins from the cytokeratin family (intermediate filament family) intermediate filament are basically neuron specific skeletal proteins Slide 15
What are the roles of Microglia cells? What are the roles of Astrocytes?
Use pattern Recognition receptors to identify and engulf foreign microbes, presents antigens to helper T cells via MHC Class II molecules --> in adults it maintain homeostasis Slide 44 Helps form the physical structure of the brain, cell surface transporter proteins for several neurotransmitters, helps clear released neurotransmitters, provides nutrients that helps support the BBB, stores glucose as glycogen , and they are antigen presenting cells Slide 45
What did Camillo Golgi develop? How did he interpret his experimental results? What is the Golgi method? What did he call his stain at first?
a stain for neural tissues (Golgi stain) that reveals individual neurons or groups of neurons He thought the Golgi stain was showing a continuous interconnected reticulum of neurons, rather than individual cells Is a silver staining technique that allows nervous tissue to be visible under a light microscope (in this time this was a mirror and sunlight) He called it the black reaction, but it was later called the Golgi method Slide 4
What is g ratio? Myelin are found in all vertebrates except...? What are saltatory conduction? What is innate myelination and what is adaptive myelination? What causes the shift between innate and adaptive?
axon diameter which is related to myelin sheath thickness hagfish and lampreys Slide 33 No voltage gated Na+ channels under the myelin, this is why AP jumps Slide34 Innate myelination occurs during development and it is the first set of myelinated neurons we have Adaptive myelination happens in the CNS after development and is the change in myelination of neurons (we reducing the myelination or making a neuron have thinker sheaths) --> neurons that fire together wire together (slide 39) Neuregulin 1 (involved with both the oligodendrocytes and Schwann cells.) Slide 36
What is peripheral neuropathy?
occurs in 50% of diabetics and is characterized as damage blood vessels, Schwann cells, and neurons --> very complicated and not completely understood Slide 56