NP1B Flashcards
When a wave of ________________ reaches the end of an axon, it stimulates the release of neurotransmitters that are stored in in vesicles
depolarization
synapses often form on __________, and the multiple branches of _________ allow for input from many different axons
dendrites
Neurotransmitter release:
Neurotransmitters are synthesized in the ___________ or the ____________ and packaged in membrane-bound secretory vesicles
axon terminus, neuron cell body
Neurotransmitter release:
Depolarization activates ______________ that mediate the influx of both Ca++ and Na+, and the rise in intracellular Ca++ causes the fusion of a small number of vesicles containing neurotransmitters to fuse with the plasma membrane of the axon terminus, releasing neurotransmitters into the synaptic cleft
voltage-gated Ca++ channels
the space between the axon terminus and the postsynaptic neuron
synaptic cleft
neurotransmitter receptor binding:
released neurotransmitters bind receptors on the _____________ neurons
postsynaptic
____________ results in either excitation or inhibition of depolarization in the post synaptic neuron
receptor binding
opening of sodium channels, increased synthesis of excitatory receptors or decreased synthesis of inhibitory membrane receptors - _______________
excitation
opening of potassium channels, increased synthesis of inhibitory receptors or suppression of cellular metabolic function - ___________
inhibition
__________ is the junction between an axon and muscle fiber
motor end plates
motor end plates are a type of synapse that uses (big/small) ____________ molecular rapidly acting neurotransmitters
small
small molecules are ——->
rapidly acting neurotransmitters
neuropeptide are ——->
slowly acting neurotransmitters
- mediate long-term effects through enzyme receptors
- synthesized in the cell body; a neuron may produce more than one type of neuropeptide
- slow removal from the synaptic cleft
Neuropeptide
complex networks for signal transduction are created through a combination of extensive dendritis branching, release of simulatory versus inhibitory neurotransmitters, and stimulation of postsynaptic inhibitory versus stimulatory receptors. thus, input from numerous presynaptic neurons may influence the activity of a single postsynaptic neuron.
synaptic complexity
(true/false) Excessive activation of excitory ion channel receptors can contributr to disease and death.
true
________ occurs when there is excessive release of an excitory neurotransmitter from an injured or degenerating neuron
Excitotoxity
During excitotoxity the neurons release excessive amounts of __________
glutamate
Glutamate binds _____________ ion channel receptor, resulting in an influx of both Na+ and Ca++
NMDA -> N-methyl-d-aspartate
What leads to excessive Ca++ entry into the post synaptic neuron, activating enzyme systems that can kill the cell?
Excessive glutamate-NMDA receptor interaction
Which are the enzyme systems that can kill the cell?
proteases
nitric oxide synthetases
phospholipases
endonucleases
Excitotoxicity has been implicated in:
stroke
hypoglycemia
viral infections
neurogenerative disorders (e.g. Alzheimer’s and Parkinson’s disease)
What inhibits normal removal of acetylcholine from the synaptic cleft?
Organophosphate
Carbamate toxicity (insecticides)
Small molecule rapidly acting excitatory neurotransmitter, and the signal is terminated through the activity of the catalytic enzyme acetylcholinesterase - ____________
acetylcholine
What inhibits acetylcholinesterase, resulting in no way to terminate the stimulatory signal?
Organophosphates
carbamate
What does neurotoxic mushrooms (Inocybe and Clitocybe species) contain that can activate a type of acetylcholine receptor in the peripheral autonomic nervous system?
muscarine
Symptoms include constricted pupils, hypersalivation, vomiting, diarrhea, bradycardia, hypotension, labored breathing and sometimes death. Effects can be reversed with atropine, which blocks the interaction between muscarine and its receptor
Neurotoxic mushrooms - contains muscarine that can activate a type of acetylcholine receptor
(true/false) Insecticide and mushroom toxicities can cause death, causing structural changes that can be detected on post mortem examination
false - can cause death WITHOUT causing structural changes that can be detected
Axon is maintained primarily by the neuron ____________.
cell body
____________ are easily recognized microscopically by extensive profiles of rough endoplasmic reticulum that stain blue with hematoxylin and eosin. (known as Nissl substance)
Cell bodies
The larger the axon, the (smaller/larger) ______________ the cell body
larger
The axon volume in _____________ times that of the cell body
1000
Which cells are needed to contribute metabolic support along the axon’s length?
Glial Cells
Neuraxonal dystrophies can have a genetic basis compounded by lower _____________ levels in blood.
antioxidant
Examples of Neuraxonal Dystrophies:
degenerative myelopathy in dogs
equine degenerative myeloencephalopathy
The dilated segments of axon are known as:
spheroids
Wallerian degeneration: Thus us the equivalent of amputating the axon, where the segment distal to the amputation _______, and the proximal section _______
dies, survives
Why can axons in the periphery regenerate?
Axons in the periphery can regenerate because nerve sheaths provides a guide for the axon to find its original destination
If the the nerve sheath is displace, them axon sprouting can go in multiple directions, creating a mass of highly sensitive nerve endings known as a _____________
neuroma
Where in the nervous system do axons lack guides and regeneratuion does not occur?
central nervous system
What has high metabolic rate and specialization, and are also susceptible to selective injuries?
Neurons
When can selective neuronal degeneration and necrosis occur?
With extreme forms of hypoxemia and hypoglycemia
degenerate cells will first lose their:
Nissl substance and this is reffered to as central chromatolysis
What is often required to establish the cause of neuronal degeneration and/or necrosis?
Clinical Data
Clumps of material in the neuron (inclusions) may reflect:
degenerative disorders
viral infection
Vacuoles (bubbles) suggest a:
metabolic disorder known as lysosomal storage disease or (depending upon distribution) prion disease
(true/false) Neurons can be replaced
False
Organophosphate toxicity and neurotoxic mushrooms share what in common?
excessive stimulation of excitatory ion channel receptors on the post synaptic neuron
Which of the following represents a defect in transport mechanisms that allows the neuron cell body to support the axon?
Neuraxonal dystrophy
