Lecture 1 Flashcards
Central Nervous System (CNS) includes?
Brain, Spinal Cord and neural portions of the eye
Peripheral Nervous System (PNS) consists of?
Peripheral Nerves, nerve endings and peripheral nerve ganglia
CNS and PNS both include the same 2 basic cell types?
Neurons and Glia/supporting cells
Cells in the Brain (CNS)?
Neurons
Glia
Endothelial Cells (brain capillary)
Ependymal (Epithelial-like cells)
1) Nissl bodies?
Ribosomes and rough endoplasmic reticulum (rER)
2) Lipofuscin pigment?
“Age Pigament” lysosomes with degradation products (residual body)
Dendrites?
-Extensions of cell soma (contain all proteins/organelles found in soma)
-Many, ramified, spiny, taper as branch
-Increase surface area of neuron for reception
-Not myelinated
Axons?
-One, straight, no spines, no taper
-Conduct action potential
-No Nissl bodies (ex. Axon Hillock)
-Can be myelinated
3 Types of Neurons?
1) Bipolar Neuron
2) Pseudo-unipolar Neuron
3) Multipolar Neuron
Bipolar Neuron?
-Single axon emerges from either side of body
-Found in sensory structures such as the retina, olfactory epithelium, and the vestibular and auditory systems
Pseudounipolar Neuron?
-Single axon divides a short distance from body
-Divides into 2 branches: Peripheral Branch (carries information from periphery) and Central Branch (ends in spinal cord or brainstem)
-These cells found in sensory ganglia of cranial and spinal nerves
Multipolar Neuron?
-Many dendrites and a single long axon emerge from cell body
-Ex: pyramidal cell of cerebral cortex and Purkinje cell of cerebellar cortex
Neuronal Function (Unique Properties of Neurons)?
1) Conduct electrochemical signals after impulses are received on dendrites or cell body
2) Neurons possess unique connections between cells: which are synapses
Direction of Information Flow?
Dendrites —> Soma —> Axon —> Synapse
Neuronal Cytoskeleton?
(Neuronal Cytoskeleton is a non-membranous organelle made up of 3 types of protein filaments:)
1) Microtubules
2) Intermediate Filaments
3) Microfilaments
3 Types of Protein Filaments?
1) Microtubules (25 nm in diameter and composed of tubulin)
2) Intermediate Filaments (10 nm in diameter and composed of neuro filament (light,medium and heavy))
3) Microfilaments (3-5 nm in diameter and composed of actin)
1) Microtubules and Motor Proteins?
-Kinesin
-Dynein
Kinesin?
Mediates anterograde (away from cell or centrosome) transport
Dynein?
Mediates retrograde transport (towards the cell or centrosome) also role in ciliary and flagellar movement
Axonal Transport?
Neurons synthesize and transport neurotransmitters and related precursor substances
Kinesin and Dynein?
Axonal Cytoskeleton and Motor Proteins (bidirectional transport of molecules along axon) (Both use ATP to move along microtubule)
Kinesin mediates anterograde transport?
Movement of organelles, vesicles, and neurotransmitters from soma (minus end) to synapse (plus end)
Dynein mediates retrograde transport?
-Movement of organelles, vesicles, and neurotransmitters from synapse (plus end) to soma (minus end)
-Also plays a role in ciliary and flagellar movement
-Potential entry of harmful substances
Retrograde Transport?
Potential entry of harmful substances (ex. viruses) from periphery to neuronal cell body
Neurons may be classified based on?
Chemical nature of transmitter located within their synaptic vesicles
Neurotransmitters are stored in the?
Axon Terminal and released at a synapse
Release of a neurotransmitter is result of?
Membrane Depolarization
Axosomatic Synapse?
An axon terminal ending on soma of a neuron
Axoaxonic Synapse?
An axon terminal contacting another axon terminal
Axodendritic Synapse?
An axon ending on a dendrite
Axospinous Synapse?
An axon terminal facing a dendritic spine
Peripheral Neuroglia in PNS?
Schwann
Satellite
Other cells associated with specific organs
Central Neuroglia in CNS?
Astrocytes
Oligodendrocytes
Microglia
Ependymal cells
Only half the volume of brain is occupied by?
Neurons
Other half of brain volume is occupied by?
Neuroglia/Glia
Radial Glia/Bergman Glia?
Reach from ependymal zone to brain’s surface
Radial Glia?
Embryonic glial cells that extend radially in neural tube and serve as scaffolding for neurons directing them to their appropriate position in brain
Glia (Neuroglia)?
Supporting cells of CNS (astrocytes, oligodendrocytes and microglia)
Schwann cells and Satellite cells?
Supporting cells in PNS
Function of Astrocytes?
-Nourishment, maintenance and protection of neurons
-Contribution to barrier that protect neurons: blood-brain barrier
-Turnover/metabolism of neurotransmitters
-Only reservoir of glycogen in brewing
-Serve as index of CNS toxicity
Astrocytes interconnect and outline CNS?
-Brain surface (glia limitans) ependymal lining of ventricles synapses and blood vessels
-Isolate synapses and nodes of Ranvier
-Surround foreign bodies in CNS
-Form a “glial scar” composed of high concentrations of GFAP fibrils at sites of injury
Astrocytes react to injury by?
Increasing GFAP
Astrocytes form?
Junctions (form desmosomal (tight) junctions and gap junctions, permitting cell to cell transfer of small molecules/ions
Microglial cells enter CNS before?
-Closing of blood-brain barrier and become ameboid microglia to clear debris during development
-BBB closes behind then and they become quiescent microglia
-Injury or infection leads to activaton
Microglia?
-Phagocytic cells, resident macrophages of CNS
-Primary responders to injury of brain, multiple sclerosis and trauma
-Microglial cells and astrocytes interact with each other and modulate immune responses
When threshold is reached?
An action potential- a wave of membrane depolarization is triggered
Flow of Na+ inside cell?
Depolarizes cell (outside of cell is rich in sodium)
Speed of action potential depends on?
Diameter of axon (larger diameter faster)
Oligodendroglia and Schwann cells produce?
Myelin (contain myelin basic protein MBP)
Astrocytes?
GFAP intermediate filaments; induction of blood-brain barrier, support and protection of neurons
Microglia?
Phagocytosis, immune response, inflammation may lead to damage of neurons
Non-Brain fenestrated?
Capillaries have small gaps in plasma membrane of endothelial cells
Brain non-fenestrated?
Capillaries have tight junctions between endothelial cells
Astrocytes induce capillaries to form?
Zonula occludens (tight junctions) limiting diffusion of small molecules
Ependymal Cells?
-Line inner surface of brain ventricles
-Ciliated
-Functions: movement of CSF and Bidirectional transport of materials between CSF and neuropil
-May be modified within ventricles to produce CSF (part of choroid plexus (CP))
Which cells are known as supportive cells in the PNS?
Satellite and Schwann cells
Indications of cell’s age?
-Lipofuscin pigment
-Metabolic lysosomal product
Smallest cytoskeletal cellular component present in all cells including neuronal cells?
Actin microfilaments
Motor protein that mediates anterograde (away from cell body) transport of products made by neuronal cell body?
Kinesin
General Organization of Nervous System?
1) Neurons
2) Neuroglia
3) Endothelial and Epithelial Cells
General Organization of Nervous System?
1) Neurons
2) Neuroglia
3) Endothelial and Epithelial Cells
Neuronal Cell Body (Soma)?
1) Nissl bodies
2) Lipofuscin pigment- “age pigment”
