Unit1Lec1-Introduction to Biology and Histology of Neurons and Gila Flashcards
What are the Anatomical components of the Nervous System?
- Central Nervous Systen (CNS)
- Peripheral Nervous System (PNS)
What is included in the CNS?
- Brain
- Spinal Cord
- Neuronal portions of the eye
What is included in the PNS?
- Peripheral nerves
- Nerve ending
- Peripheral nerve ganglia
What two cells are included in the CNS and PNS?
- Neurons
- Glia/Supporting cells
List the cells in the brain (CNS)
- Neurons
- Glia=Neuroglia (Astrocytes, Oligodendrites, Microglia)
- Endothelial cells (brain capillary)
- Ependymal (Epithelial-like cells)
Structure of neuron
(Several) dendrites, soma (cell body), axon, synapses
What is the function of neurons?
Conduct electrochemical signals after impulses are recieved on the dendrites or the cell body.
Describe the path of signals in a neuron
- Signal is recieved by the dendrites to the cell body
- Continues down the axon (myelinated or unmyelinated)
- Signal then travels to the synapse that makes the connection to other nerves or muscle cells
How many types of neurons are there? List them
3 types of neurons
1. Bipolar
2. Pseudo-unipolar
3. Multipoplar
Describe bipolar neurons and where are they found?
- A Single axon emerges from either side of the cell body
- Found in sensory structures (retina, olfactory, epithelium, vestibular & auditory systems)
Describe the pseudo-unipolar neurons and where are they found?
- A single axon divides a short distance from the cell body
- Two branches: peripheral branch and central branch
- Found in sensory ganglia of cranial and spinal nerves
Describe multipolar neurons and what are some examples?
- Many dendrites and a single long axon emerge from the cell body
- e.g. Pyramidal neuron of the cerebral cortex
- e.g Purkinje cell of the cerebeller cortex
What are the components (5) of the soma (cell body)?
- Nucleus
- Nucleous
- Nissl bodies
- Lipofuscin pigment-“age pigment”
- Intermediate filament
Describe Nissl bodies
Structures that hold ribosomes and rough endoplasmic reticulum (rER)
Describe Lipofuscin pigment (“age pigment”)
- Staining that shows lysosomes with degradation products (residual bodies)
List the characteristics (4) of dendrites
- Ramified, spiny, branches extending off the soma
- Increase surface area of neuron for reception
- Contain all proteins/organelles
- NOT myelinated
True or False: Dendrites are mylienated
False
List the characteristics of axons
- Singular, straight segment, with no spines
- Responsible for conducting action potential
- No Nissl bodies (e.g axon hillock)
- CAN be myelinated
True of False: Axons can be either myelinated or unmyelinated
True
List the filaments that the neuronal cytoskeleton is made up of
- Microtubles
- Intermediate Filaments
- Microfilaments (actin)
True or false: the neuronal cytoskeleton are non-membranous organelles
True
What are microtubules composed of and the relative size?
- Tubulin
- 25 nm in diameter
What are Intermediate Filaments composed of and their relative size?
- Composed of neurofilaments (light, medium, and heavy)
- 10 nm in diameter
What are Microfilaments composed of and their relative size?
- Actin
- 3-5 nm in diameter
Microtubules play a part with which types of proteins in the cytoskeleton?
Motor proteins
What is the function of motor neurons
Bidirectional transport of molecules along the axon
List the 2 motor proteins
- Kinesin (dimer w/ 2 identical motor heads)
- Dyenin
What type of transport does kinesin mediate?
Anterograde
Describe Anterograde transport
Done by Kinesin
- Movement of organelles, vesicles and neurotransmitters from soma (- end) to synapase (+ end)
- Fast, Intermediate and Slow
- “away from cell body”
What type of transport does Dynein mediate?
Retrograde transport
Describe Retrograde transport
Done by Dynein
- Movement of organelles, vesicles and neurotransmitters from synapse (+ end) to soma (- end)
- 1/2 rate of anterograde
- “toward the cell body and termina end of axon”
Where else does Dynein play a role?
In cillary and flagellar movement
What causes potential entry for harmful substances (e.g. virus)?
Retrograde transport (Dynein)
What is need for kinesin and dynein to work?
ATP
What cytoskeleton are intermediate filaments a part of and their composition?
- Are a part of Neuronal and Glial cytoskeleton
- Heterogenous group composed of 6 main classes
What type of proteins are neurofilaments and where are they found?
- Triple proteins (Light ,Middle, Heavy proteins)
- Found in axon & dendrites of nerve cells
List and describe the 3 types of neurofilaments
- Nestin: neuronal stem cells (nerve cells)- Type VI IF
- Glial Acidic Fibrillary Protein (GFAP): astrocytes- Type III IF
- Peripherin: peripherial nerve cells-Type III IF
Why do pathologist primarily look at Intermediate filaments?
To determine what cell/type tissue they’re working
Changes in neurofilaments within the brain are characteristics of what disease?
Alzheimer’s disease, which produces neurofibrillary tangles
What are microfilaments composed of and list the two types?
- Composed of the protein actin
- G-actin (Globular)- free floating actin in cytoplasm
- F-actin (Filamentous)-polymerized actin
Describe the structure of F-actin
- Plus-barbed end=fast growing
- Minus-pointed end=slow growing
Describe the mechanism occuring at the synapse
Action potential causes membrane depolarization—>leads to an Influx of Ca+ ions–>causes release of a neurotransmitter
List and describe the 4 types of synapses
LOW yield
- Axosomatic- An axon terminal ending on the soma of a neuron
- Axoaxonic- Axon terminal contacting another axon terminal
- Axodendritic- An exon ending on a dendrite
- Axospinous-An axon terminal facing a dendritic spine
What are neuroglia
Supporting cells of the nervous system. They are nonconductive but rather offer physical and metabolic support for neurons
List the Peripheral (PNS) Neuroglia
- Schwann cells
- Satellite cells
List the Central (CNS) Neuroglia
- Astrocytes
- Microglia
- Oligodendrocytes
Only half the volume of the brain is occupied by neurons. The other half of the brain volume are…………
Neuroglia/glia
What glia are present during development and what are their function?
- Radial Glia (Bergman glia)
- Serve as “scaffolding” for neurons migrating to their final location in the brain
What are radial glia an example of?
The functional interdependence of neuroglial cells and neurons during development
What are the two types of astrocytes and where are they found
- Protoplasmic (gray mattter)
- Fibrous (white matter)
List the functions of Astrocytes
HIGH yield
- Nourishment, maintenance & protection of neurons
- Contribute to blood-brain barrier
- Glycogen stores
- Index of CNS toxicity
Astrocytes interconnect and outline the CNS at the (4):
- Brain surface (glia limitans)
- Ependymal lining of the ventricles
- Synapses
- Blood vessels
Astrocytes form and permit what?
- Desmosomal (tight) junctions & Gap junctions
- Permitting cell to cell transfer of small molecules/ions
Astrocyte ________ to injury
React
How do astrocytes react to injury?
Increases concentrations of GFAP fibrils at the site of injury forming a glial scar
How do scientist detect CNS toxicity injuries?
Formation of glial scars by astrocytes
What are Microglia?
- Phagocytic cells of the CNS
- The primary responders to injury of the brain
e.g. multiple sclerosis and trauma
Mircoglia initiate the immune response by….
- Releasing chemoattractants which recruit leukocytes across the BBB
- Contains complement receptor 3 and MHC-II
Why do microglial cells and astrocytes interact with each other?
To modulate immune responses
Describe the stages of microglia showed in the photo
A. Quiescent (resting) microglia monitor CNS for injury
B. After damage, microglia progressively activate and thicken
C. Severe activation leads to rounding of cells to form macrophages
Where are Oligodendrocytes found in the CNS?
White matter (fascicular)
List the functions of oligodendrocytes
- Synthesize myelin sheath
- Insulates the axons and enhances speed of conduction of electrochemical impulses
- Wrap around axons of several CNS axons
Where are Schwann Cells found?
PNS
List the functions of Schwann cells
- Synthesize myelin sheaths
- Insulate the axons and enhances speed of conduction of electrochemical impulses
- Wrap around a single axon in the PNS
What do Endothelial cells cover?
Blood vessels
What are Non-Brain Fenestrated endothelial cells?
Non-brain fenestrated capillaries have small gaps in plasma membrane
What are Brain Non-Fenestrated endothelial cells?
Brain Non-fenestrated capillaries have tight juntions between endothelial cells
What forms the Blood Brain barrier
Formed by Endothelial cells with tight junctions+ glial foot processed of astrocytes
What do astrocytes induce capillaries to form?
Zonula Occludens (tight junction) limiting diffusion of small molecules
What do epithelial cells cover?
Outer surface of the internal organs and the body
Functions of epithelial cells of the ependyma
- Movement and absorption of CSF (via cilia and microvilli)
- Bidirectional transport of materials between CSF and neuropil
What do ependymal cells line?
The inner surface of the brain ventricles
How can ependymal cells be modified? and are a part of?
- Modified within the ventricles to produce CSF
- Part of choroid plexus (CP)
- All of the following are true regarding neuronal dendrites EXCEPT:
A. Ramified, spiny branches
B. Increase surface area of neuron
C. Lack nissl bodies
D. Not myelinated
c. lacks nissl bodies
The movement of organelles, vesicles, and neurotransmitters from the synapse of a neuron to the soma (is referred to as ______ transport and is mediated by ______.)
A. retrograde; dynein
B. retrograde; kinesin
C. anterograde; dynein
D. anterograde; kinesin
a. retrograde; dynein
- What is the primary function of epithelial cells in the ependyma?
A. Form the blood brain barrier via tight junctions
B. Synthesize myelin sheath surrounding axons
C. Nourishment and protection of neurons
D. Movement/absorption of CSF
d. movement/absorption of CSF
- An MSP3 student is studying a newfound carcinogen which affects glial cells of the peripheral nervous system. Which of the following glial cells is most likely to be affected by this carcinogen?
A. Astrocytes
B. Schwann cells
C. Microglia
D. Oligodendrocytes
b. Schwann cells
- Which of the following glial cells is the primary responder to injury of the brain?
A. Astrocytes
B. Schwann cells
C. Microglia
D. Oligodendrocytes
c. Microglia
