Nervous System Flashcards
The nervous system is made of the ____ and ____.
CNS and PNS
The CNS consists of the ____ and ____. It has _______ that conduct signals ____ the CNS to _______.
Spinal Cord and Brain
Motor Elements, from effectors cells in muscles, glands, viscera etc.
The PNS consists of ______ and has _____ that conduct information _____.
all other nerves
sensory elements, to the CNS
Motor output can be through the ___ or _____.
Somatic or Autonomic
The autonomic nervous system can be split into _______ and ________.
Parasympathetic (Rest and digest)
Sympathetic (Fight or Flight)
Neurons are polarized. True or False?
True
Neurons are stained with the _________.
Golgi method
Dendrites may have ________ shaped like ____. Axons do not have this structure.
Dendritic Spines, Mushroom
Flow of signals through a neuron.
Signal is received by dendrites, process through the cell body and passed down through the axon to release NT.
There are three different neuron morphologies. Describe them.
Multipolar: Classic neuron shape. One axon with short fat dendrites.
Bipolar: Cell body in center with one dendrite and one axon protruding from opposite ends
Pseudounipolar: No true dendrites but rather one large axon. Peripheral projection may extend into skin while central projection will extend into CNS to TRANSMIT information
The most common neuron shape is _______.
Multipolar
Bipolar neurons are found in ________.
Visual and olfactory organs
Pseudounipolar cells are found in ______.
Sensory ganglia of cranial and spinal nerves
Communication between neurons occurs at the _____ where the ________ of the ______ sends neurotransmitters to the ________ of the _____.
synaptic cleft
pre-synaptic terminal of the axon
post-synaptic terminal of the dendritic spines.
Axons contain several _______ containing _______ that will show up on an EM. They also contain lots of _____ needed to ________.
vesicles containing neurotransmitters
mitochondria needed to make ATP to facilitate release of neurotransmitters
The postsynaptic contacts of ________ on an EM will appear as a ______ due to _______.
dendritic spines, an electron-dense line, clustered NT receptors and their associated proteins
What is the major excitatory NT in the CNS?
This causes _________.
Glutamate
Depolarization (more positive)
What is the major inhibitory NT in the CNS?
This causes________.
GABA
Repolarization (More negative)
What allows for loading of a neurotransmitter into the vesicle of the pre-synaptic vesicle in the axon?
What is it activated by?
Proton gradient activated by glutamate.
There are 4 steps of vesicle transport. What are they?
1.Budding
2.Movement (diffusion or motor driven)
3.Tethering to cytoskeleton
4.Fusion where a pore is created to allow transmission of NT from axon through synaptic cleft into the dendrite.
What are key steps involved with tethering and fusion?
Fusion involves the recognition of V-SNARE and T-Snare which interlock and force the donor and acceptor membranes together allowing for NT to be released into the synaptic cleft.
What signals the fusion of synaptic vesicles?
Ca2+!
In the pre-synaptic cell there are Ca2+ channels. When the cell receives a signal via its dendrites, there is an influx of calcium into the cell which urges the fusion of the membranes and the release of NT.
_________ from ____ and _______ bacteria can ____________.
Neurotoxins from Clostridium botulinum and Clostridium tetani can cleave Synaptic Vesicle SNAREs
BOTOX
A voltage potential exists across the membrane. The inside is _______ than the outside. The voltage change is _____ meaning that it________ with distance from the sight of input. _______ inputs are needed.
more negative
graded, decreases, multiple.
When depolarization occurs above a certain threshold value due to ________, _______ open. This conveys a need for ________.
What happens after?
influx of a excitatory NT like Glutamate, Na+ , Action Potential.
Na+ rushes into the cell creating an electrical signal. K+ channels are then opened to allow ions to flow out to repolarize the membrane.
What is the first step of the action potential?
Influx fo Na+ ions into cell due to depolarization by excitatory NT.
Ca2+ is only for the release of the NT into the cleft and into the dendrite!
Neurons have a very prominent _______ especially in the ______. _________ and ______ are the most prominent elements.
Cytoskeleton, axon and dendrites
Microtubules and Neurofilaments (Neuronal IF)
Microtubules and neurofilaments are non-myelinated. True or false?
True
What is Nissl material?
What can they highlight?
Nissl material is acidic components that show up blue because they can be bound by basic dyes.
Nucleolus, Ribosomes/Polysomes
mRNA,tRNA and rRNA
Do neurons have a large amount of Nissl material?
Yes
The neuronal cell body contains lots of _________ but the ________ and __________ do not.
RER
Dendrite and Axon
An ___ is a morphological feature that _____ Nissal stain. Another name for it is _______.
It contains high levels of __ and ______ and is more likely where _____ but varies from ___ to _____.
Axon hillcock, does not
Axon initial segment
Na+ and K+ channels, action potential occurs , neuron to neuron
Axonal proteins are synthesized in the _______.
Cell body
Anterograde transport occurs from _______ to ______ and is controlled by ______.
Retrograde transport occurs from _______ to ______ and is controlled by ______.
Both ______ and ____carry _____________
Cell body to axon tip, Kinesin
Axon tip to cell body, dyenin
Both dyenin and kinesin carry cargoes along microtubules
Mutations in _____,____,_____ can cause ___ and _________ such as :
tubulins, dyenin, kinesis and cargo proteins can cause motor and sensory neuropathies including
Diabetes
Chemotherapy-induced Neuropathy
Huntingtons Disease
Alzheimers Disease
Describe Rabies Virus infection
- Rabies Virus is carried saliva of infected animal enters tissue after bite
- Virus travels via retrograde axonal transport and enters spinal cord and brain.
- Virus disperses to extra-CNA sites such as salivary glands via anterograde transport.
What are the PNS Cells?
Satellite Cells and Schwann Cells
What are the CNS Cells?
Oligodendrocytes
Astrocytes
Microglia
Ependymal Cells
Compacted myeline appears as a _______ and the axon appears as a _________ on EM.
Compacted myeline appears as a _______ and the axon appears as a _________ on H&E
Dark ring , white center
Stained darker pink, stained as a distinct light pink ring with a border
The __________ conducts myelination of a peripheral ____.
Schwann Cell, Myelination, Peripheral Axon
Myelination of PNS
A growing Schwann cell spirals inwards around the axon and wraps into layers of myelin.
The myelin is a single wrap which means layers are very close together in apposition of the membrane lamella. Additional adhesive contacts between adjacent membrane layers also allow for compaction
Very little cytoplasm!
What is the ratio of Schwann cells to ______ axon myelination?
1 Schwann Cell :1 PNS Axon
Myelination makes __________. It increases ______ so that _____ can ______ along the _______ without __________.
action potential faster
membrane resistance, membrane depolarization, propagate further without the need for action potential generation
Why are there breaks in the myelin sheath? What are they called?
Membrane potential will decay over distance within the axon so sodium channels clustered at gaps in the myelin re-boost action potential.
Nodes of Ranvier
CNS axons are myelinated by _______ . What is the ratio of axon myelination to these cells?
Oligodendrocytes
One oligodendrocyte can myelinate multiple axon segments on multiple separate axons.
Oligodendrocytes look like a ________ while Schwann cells look like a _____.
Octopus; the cell branches out to touch multiple axon regions
Swiss Roll: The cell is wrapped around the axon
MS
Patients have an increase in antibodies in CSPF and abnormal T-cell function.
Caused by CNS demyelination
Guillain-Barre
PNS demyelination
Autoimmue
Adrenoleukodystrophy
Failure to generate plasmalogens which is one of the key lipids that makes up myelin sheath.
Delayed myelination, desmyelination , demyelination or combo.
Inherited
Central Pontine Myelinolysis
Demyelination in the central pons, occurs after rapid correction of hypoatremia caused my alcoholism or malnutrition.
Progressive Multifocal Encephalopathy
Viral infection of oligodendrocytes in patients with immunodeficiency
Virus born
Astrocytes form the ________ and secrete __________.
blood-brain barrier, neurotrophic factors
What are the functions of astrocytes?
Form Blood-Brain Barrier
Metabolic cooperation with neurons
Regulation of cerebral blood flow
Regulation of intercellular fluid composition in brain
Mobilize glycogen for lactate conversion which neurons will use to make pyruvate for TCA
Clean up excess glutamate
Why is the blood-brain barrier important?
It helps determine composition of interstitial fluid by restricting ionic and fluid movements between blood and brain.
Ex. Na+ and K+ channels
What makes up the blood brain barrier?
Basal lamina covering to which astrocyte feet hold on
Capillary Endothelial Cells and tight junctions
What are the two passive transports of the BBB?
What are the three active transports of the BBB?
Paracellular Aqueous
Transcellular Lipophilic
Transport Proteins
Receptor Mediated Transcytosis
Adsorptive Transcytosis
What is the synaptic cleft into the astrocyte?
Cerebrospinal fluid
Astrocytes can _______ to produce ____. Neurons take up _____ and convert it to _______ via the _____. This allows for it to be used for other metabolic pathways and protect other neurons from ________.
Astrocytes express _____ which take up _____ from the _______and recycle it by ______
mobilize glycogen, lactate
lactate, pyruvate and later glucose via TCA
low glucose
Glutamate Receptors
Excess Glutamate
Synaptic Cleft
converting it into glutamine
Microglia are a _______ in the ______and are _______ than other _____ cells.
immune cells in the CNS
Smaller, glial
Microglia are created during _______ and replicate via _________. They are NOT in _______. Their function is to ________.
Embryogenesis, self-propogation
blood circulation, clean up damaged tissue
How are microglia activated?
Physical injury, local inflammation/infection changes microglial morphology from RAMIFIED to AMOEBOID.
Can microglia be harmful?
yes, they can secrete cytokines that exacerbate inflammation
Ependymal Cells _________ and ______. They are involved in the _________ and ________ which ________.
line the ventricles of the brain and central canal of spinal cord
production and circulation of CSF which acts as a buffer and cushion for brain and spinal cord
What is the shape of Ependymal Cells?
Cuboidal to columnar epithelium is formed between CSF and ISF of CNS.
Ependymal cells have microvilli and cilia true or false?
True
The ISF-CSF barrier is much ____ than the BBB.
looser
The spinal cord is made of ______, ____ , ___ and ______.
White matter, gray matter, spinal ganglion, ventral root
White matter is made of ______ and _______. It is ______ positive.
myelinated axons and oligodendrocytes
NOT Nissle Positive
Gray matter is made of _______ plus ____________. It is _____ positive.
neuronal cell bodies plus astrocytes and motor axon
Nissle Positive
Spinal Ganglion also known as _______ or ____contains the ____ of _____ whose axons project into the ________ via the _______. It is ______ positive.
Dorsal Root Ganglion or Central Ganglia
cell bodies of sensory neurons whose axons project into the spinal cord via the dorsal root.
It is Nissle Positive.
The ventral root is the _______ of _____ from the ____ to ________. ________ are in the _________ of _________.
projection of motor axons from spinal cord to innervate muscle
Motor neuronal cell bodies are in ventral part of spinal cord gray matter.
In the PNS, neuronal cell bodies are clustered together in _____. Axons bundles together are called ______.
Ganglia, nerves
Satellite Cells are a _____ cell that _______.
PNS, surround nerve cell bodies, provide trophic support to neurons
Structure of PNS Nerves
(internal to external)
1.Axon
2. Myelin bound axon
3. Endoneurium surrounding single myelin-bound axon
4. Fascicle forms with multiple nerve fibers
5. Fascicle is covered by perineurium.
6. Multiple fascicles bind together to form the nerve which is surrounded by the epineurium.
The epineurium is made of _____________ containing ____ that surrounds ______ and fills ________.
DIRCT , adipose tissue
surrounds the nerve and fills space between nerve fasicles
Schwann cells can sheath ________ PNS axons. Transfer of information is ______.
Nonmyelinated. The transfer of info is much slower.
Dull toothache!
Can the PNS nerves regenerate after injury?
Yes!
How does the PNS nerve regenerate after injury?
- Injury occurs piercing nerve
- Wallerian degeneration of distal axon triggered by impaired transport of axon survival factors past injury site occurs 2-3 days after.
Blood-nerve barrier breaks down to allow influx of macrophages which cooperate with Schwann cells to digest myelin.
- Schwann cells DEdifferentiate,proliferate and line up to coordinate with the basement mebrane to form Bands of Bunger that guide regenerating toxins.
They also shed and degrade myelin debris.
- Innervation occurs once axon reaches target such as muscle fiber.
What is Wallerian Degeneration?
Wallerian degeneration is a process that occurs when a nerve fiber is cut or crushed, causing the axon distal to the injury to break down along with its myelin sheath. It is part of the PNS nerve regeneration process.
Injured axons appear __________ while uninjured axons appear _____ in EM and toluline blue.
irregular shapes, varying level of myelination
much more regular
What is a key feature of injured axons in EM?
Along with irregular shape and varying myelination, injured axon organelles may not be visible or may be clustered in one region of the axon. There will also be myelin decompaction.
Is the CNS nerve system good at regenerating?
No!
Why is the CNS nerve system not good at regenerating?
Oligodendrocytes can clean up myelin debris but there is limited macrophage infiltration and myelin breakdown.
The _________ is critical for learning and memory. It is _______ positive.
It has a distinct _____ shape.
Hippocampus, Nissl
C-shape kinda stretched out. Looks like two bunny ears
