Exam1Lec1IntrotoBiology&HistologyofNeuronsandGlia Flashcards
What does the CNS consist of?
- Brain
2.Spinal cord
3.Neural portions of the eye
What does the PNS consist of?
- Peripheral nerves
- Nerve endings
- Peripheral nerve ganglia
What does the CNS and PNS both include?
Two basic cell types:
Neurons and glia/supporting cells
supporting cells are impt fore the survival of neurons
Soma can also be called what?
Neuronal cell body
A multipolar neuron has 3 major components. What are they?
Soma/cell body, many dendrites, 1 axon
What are the three regions of the neuron?
- Receptor region (contains soma)
- Conductive region (contains axon)
- Effector region (signal ends up here)
Membrane bound organelles on a cell contribute to what?
slide 9
Production of proteins
What are nissl bodies?
These are located on soma. They are Ribosomes and rough endoplasmic reticulum (rER)
These stain dark with basic dye cresyl violet
What are lipofuscin pigment? “age pigment”
They are located in soma. They are lysosomes with degradation products (residual body)
These accumulate throughout life
Intermediate filaments are important for what?
Recognition of cells and gives specificity
What are dendrites?
Extensions of cell soma. They contain all proteins/organelles found in soma. They are ramified and spiny. They are NOT myelinated and incr surface area of neuron for reception.
What are axons?
Conduct action potential and have NO NISSL bodies (axon hillock). They can be myelinated
Neuron classification is based on what?
Shape
What are the three types of neurons?
Bipolar, pseudounipolar, multipolar
Where can bipolar neurons be found?
Sensory structures such as retina, olfactory epithelium, vestibular and auditory systems
Where can pseudounipolar neurons be found?
Sensory ganglia of the cranial and spinal nerves
Where can multipolar neurons be found?
Pyrmidal neuron in the cerebral cortex
Purkinje cell in the cerebellar cortex
What are two unique properties of neurons?
Conduct electrochemical signals after impulses are received on the dendrites or the cell body
Connection between cells called synapes
What is the direction of information flow?
Dendrites, soma, axon, synapse, another neuron or muscular component
What are the three types protein filamments that make up the neuronal cytoskeleton?
cytoskeleton=non membranous organelles
Microtubules
Intermediate filaments
Microfilaments (actin filaments)
What are microtubules?
Largest cytoskeleton component, 25 nm in diameter. Composed of tubulin. They transport neurotransmitters made by soma
This is like the highway for movement, hollow tube
What are intermediate filaments?
They are used for identification of cells/tissues (specificity). They are 10 nm in diameterand are composed of neurofilaments (light, medium, heavy)
ropelike structure, supporting and structual role
What are microfilaments?
3-5nm in diameter and composed of actin
shortest component
What is G-actin?
Globular actin: free actin in cytoplasm
What is F-actin?
Filamentous actin: polymerized actin of the filament (plus-barbed end= fast growing, minus pointed end=slow growing)
The ____ and the ____ of actin is a dynamic and constant process. So a cell reacts to its environment and goes through these processes on a regular basis. Without this occuring, the cell cannot survive
polymerization, depolymerization
G-actin polymerizes and becomes f-actin
True or False: Intermediate filaments are a component of botn neuronal and glial cytoskeleton?
True
True or false: Intermediate filaments have a heterogenous group composed of 6 main classes and they vary in different cell types
True
What has very specific intermediate filaments?
slide19
Peripherin (peripheral nerve cells)
What are neurofilaments composed of?
neurofilament triplet proteins (L, M, H proteins) in axons & dendrites of nerve cells.
- Nestin – neuronal stem cells (nerve cells)
- Glial Acidic Fibrillary Protein (GFAP) – astrocytes
- Peripherin – peripheral nerve cells
What is effected in neurodegenerative diseases?
Neurofilaments, changes in this is characteristic of Alzheimer’s which produces neurofibrillary tangles
Kinesin mediates ____ transport
motor protein associated with microtubules
anterograde (fast-dominant, intermediate, slow)
soma to synpase
away from cell or centrosome
Dynein mediates ____ transport
motor protein associated with microtubules
retrograde (slow)
synapse to soma
towards the cell or centrosome. Also has a role in ciliary and flagellar movement
Explain how kinesin does fast axonal transport
Organeles and vesicles attach to kinesin. Kinesin is the molecular motor with 2 motor heads and they both contain ADP. When one binds to the microtubules tightly, adp is released and ATP is bound. The second head is then thrown into the next binding site on the microtubule. Phosphate is released from the previous head and the current head releases adp and binds atp. The cycle repeats and the heads move steo by step along the microtubule.
uses atp
https://www.youtube.com/watch?v=YAva4g3Pk6k
Explain how Dynein does retrograde axonal transport
Organelles and vesicles attach to dynein. Dynein is the molecular motor with 2 motor heads and they both contain ADP. When one binds to the microtubules tightly, adp is released and ATP is bound. The second head is then thrown into the next binding site on the microtubule. Phosphate is released from the previous head and the current head releases adp and binds atp. The cycle repeats and the heads move steo by step along the microtubule.
uses atp
https://www.youtube.com/watch?v=YAva4g3Pk6k
What can potentially occur with retrograde transport?
Potential entry of harmful substances (ex viruses) from the periphery to neuronal cell body
Neurons may be classified based on the chemical nature of the transmitter located within their _____ _____.
synaptic vesicles
Where are neurotransmitters stored and released?
Stored in the axon terminals and released at a synapse
The release of a neurotransmitter is the result of a
membrane depolarization
What happens to Ca+ ions when there is membrane depolarization?
Large influx of Ca2+ ions via voltage sensitve channels
What are neuroglia?
supporting cells of the nervous system
What are the peripheral neuroglia in the PNS?
Schwann, satellite, and other cells specific to organs
What are the central neuroglia in the CNS?
Astrocytes
Oligodendrocytes
Microglia
Ependymal Cells
One half of the brain voulme is occupied by ____ and the other half is occupied by ____.
neurons, neuroglia/glia
What are the type of cells that reach from the ependymal zone to the brains surface during development?
specialized astrocytes called radial glia or Bergman glia
What are radial glia?
Embryonic glial cells that extend radially in the neural tube and serve as scaffolding for neurons directing them to their correct position in the brain. Immature neurons move along their processes to their final destination in the brain.
Radial glia also act as scaffolds along which new neurons can travel from their site of origin to their final destination in the brain.
Axonal cytoskeleton and motor proteins: bidirectional transport of molecules along the axon
Kinesin and Dynein
What is the marker of astrocyte activation?
GFAP (glial fibrillary acid protein)
What are the 5 functions of astrocytes?
- Nourishment, maintenance and protection of neurons
- contributes to BBB
- absorb excess neurotransmitters
- the only reservoir of glycogen in the brain
- serve as the index of CNS toxicity
Protoplasmic astrocytes are in ____ matter
gray
Fibrous astrocytes are in ____ matter
white
Astrocytes interconnect and outline CNS, explain this
astrocytes make up the brain surface (glia limitans), ependymal lining of the ventricles , blood vessels, and synapses
What isolate synapses and the nodes of ranvier?
Astrocytes
What surrounds foreign bodies in the CNS?
Astrocytes
What form a “glial scar” composes of high concentrations of GFAP fibrils at sites of injury?
Astrocytes
IMPT for protect
How does Astrocytes react to injury?
By increasing GFAP
Astrocytes have a more bushy structure
What allows astrocytes to do cell to cell transfer of small molecules/ions?
They form desmosomal (tight) junctions and gap junctions
astrocytes form a syncytium; connections b/w cells allow diffusion of ions or other small cytoplasmic molecules b/w adjacent astrocytes.
What is connexin-43?
Gap junction protein
Astrocyte functions summary (6 points)
- Surround the CNS
- Induce BBB
- Buffer potassium (and other substances) and protect neurons
- Storage of glycogen
- Guide neurons during development
- react to injury, provide EC matrix proteins, and form scars GFAP positive
Explain the life cycle of Microglia
- Microglial cells enter the CNS before the closing of the BBB and become ameboud microglia to clear debris during development.
- The BBB closes behind then and they become quiescent microglia
- Injury or infection leads to their activation
True or false Microglia are both phagocytics and immunogenic
True
What are the resident macrophages of the CNS?
Microglia-phagocytic cells
What are the primary responsders to injury of the brain, e.g., multiple sclerosis and trauma?
Microglia
They release
How are microglia immunogenic?
They release chemoattractans that then recruit leucocytes across the BBB and initiates immune response
What is the marker for microglia?
Complement receptor 3 and MHC-II
not just cleaning cells but also antigen responding
____ and ____ interact with each other and modulate immune responses.
Microglial cells and astrocytes
Explain how microglia reacts to CNS injury
- Quiescent or resting microglia monitor CNS for injury
- After damager they become progressively activated with incr soma diameter and thickening and retraction of processes
Severe activation causes rounding of cells to form macrophages
changes in morphology to react to injury
Where are oligodendrocytes located in the CNS?
White matter (fasicular)
What do oligodendrocytes synthesize?
Myelin sheats
high lipid content with cholesterol and cerebroside
Oligodendrocyte wrap around what?
axons of several CNS neurons
Insulate the axon and enhance the speed of conduction of electrochemical impulses
Oligodendrocytes
What produces myelin sheaths in the PNS?
Schwann cells
What do Schwann cells wrap around?
A single axon (the entire cell wraps around one axon)
one schwann cell myelinates one neuron
With multiple sclerosis are nerve fibers myelinated or demyelinated?
Demyelinated
axons cannot fxn properly
Stimuli from multiple synapses sum at the…
axon hillock
When threshold is reached what is triggered?
Action potential (wave of membrane depolarization)
flow of Na+ inside the cell depolarizes, outside the cell is rich in sodium
The speed of action potential depends on what?
Diameter of axon (larger diameter faster)
Explain myelin speed conduction
Nerve impulses “jump” from node to node. This is called saltatory conduction
What are ednothelial cells?
Brain capillaries with tight junctions
What do non-brain fenestrated capillaries have?
Small gaps in plasma membrane of endothelial cells
What do brain fenestrated capillaries have?
Tight junctions between endothelial cells
True or False, Astrocytes participate in formation of BBB
True
How is the BBB formed?
endothelial cells with tight junctions and glial feet procesess of astrocytes
Astrocytes induce capillaries to form ____ ____ limiting diffusion of small molecules
zona occludens (tight junctions)
most susbstances need to be actively transported across endothelias cells into the brain including glucose
What are epithelial-like cells?
ependyma
What are 6 charactersitcs of ependymal cells?
- Line inner surface of brain ventricles
- ciliated
- moves CSF by using cilia
- Bidirectional transport of materials b/w CSF and neuropil
- Can be modified w/in ventricles to make CSF: part of choroid plexus (CP)
- Absoption and production
