Neuronal Synap-c Transmission Flashcards
What is a Synapse?
Site of intercellular communica-on between 2 neurons or between a neuron and an effector.
How is information passed in neurons?
through synapse.
What is presynaptic?
Toward synapse
What is postsynaptic?
Away from the synapse.
What do most neurons function as?
Presynaptic and postsynaptic.
What is a synaptic cleft?
Tiny Gap
What can be blocked in its transmission?
Synapse
Synapse may be changed from a single impulse into what?
Repetitive impulse.
What is the basis of learning and memory?
Experience changes strength of synaptic connections.
What does Botulism toxin do?
Inhibits muscle contraction and blocks fusion of synaptic vesicles at the neuromuscular junction in motor neuron.
What is NMJ?
Neuromuscular junction
What are classic symptoms of botulism in adults?
double vision, blurred vision, drooping eyelids, slurred speech, difficulty swallowing, dry mouth, and muscle weakness.
How do infants with botulism look?
lethargic, feed poorly, are cons-pated, and have a weak cry and poor muscle tone.
What are therapeutic uses of botox?
Severe underarm swea-ng Cervical dystonia - a neurological disorder that causes severe neck and shoulder muscle contrac-ons Blepharospasm - uncontrollable blinking Strabismus - misaligned eyes Chronic migraine Overac-ve bladder
What are cosmetic uses of botox?
Temporary smoothing of facial wrinkles and improving your appearance.
Initiating neuron =
presynaptic neuron
Synapse has two internal structures important to the excitatory or inhibitory and they are?
Transmitter vesicles and mitochondria.
What are the transmitter vesicles?
Contain transmitter substance excitatory or inhibitory.
Mitochondria is used how?
Supplies ATP to synthesize neurotransmitter substance.
10,000 to 20,000 per minute synaptic knobs
presynaptic terminals
What percentage of presynaptic terminals lie on dendrites?
80-95%
2-20% lie on what?
presynaptic terminals on soma
What are the function of neurons based on?
• Size of cell body • The length, size , and number of dendrites • The length and size of the axon • The number of presynap-c terminals
Receiving neuron =
postsynaptic neuron
Where are Receptor proteins found?
at the membrane in
two important components.
What are the two important components receptor proteins are found?
Binding component and Ionophore component.
What is the binding component?
- protrudes outward from the membrane into the synap-c clee
- binds with the NT from the pre-synap-c terminal
What is the ionophore component?
Passes all the way through the membrane to the interior of the post-synap-c neuron
What are the two types of channels in the ionophore component?
Cation channels and Anion channels
What does the cation channel handle?
most often allow Na+ to pass, sometimes K+ or Ca++ (excitatory transmitter)
What does the anion channel handle?
allow mainly Chloride ions to pass, minute quantities of other anions (inhibitory transmigger)
What does the process requires prolonged changes in neurons?
The process of memory
How do you classify a synapse?
The action they produce on the post synaptic neuron- excitatory or inhibitory.
What is an excitatory synapse?
They secrete a substance that excites the post synaptic neuron
Excitatory synapse is in charge of what?
opening of Na+ channels, depressed conduction of chloride channels, and internal metabolism.
Opening Na+ channels allow what?
Large numbers of positive electrical charges to flow to the interior of the post synaptic cell.
What do chloride channels experience when it is in excitatory synapse?
Depressed conduction.
Inhibitory Synapse does what?
They secrete a substance that inhibit the post synaptic neuron.
What is responsible for opening chloride ion channels?
inhibitory synapse through the receptor molecule.
Inhibitory synapse activates what?
receptor enzymes that inhibit cellular metabolic functions
How many neurotransmitters have been identified?
more than 100
How do neurotransmitters make channels open?
binding on to receptors.
A second messenger system results in what?
Results in either excitation or inhibition of the target.
Where are neurotransmitter synthesized?
in the cytosol of the pre-synaptic terminal, absorbed by active transport into the vesicles.
How many classes of small molecule, rapidly acting transmitters?
4
What does class 1 consist of?
Acetylcholine
What does class 2 consist of?
Amines: norepinepherine, epinephrine, dopamine, serotonin, and histamine.
What does class 3 consist of?
Amino Acids: Gamma- aminobutyric acid (GABA), Glycine, glutamate, aspartate
What does class 4 consist of?
Nitric oxide
ACh is short for?
Acetylcholine
All neuromuscular junctions use what?
ACh
Where is ACh released at?
Chemical synapses.
ACh is released in chemical synapses where?
In the PNS and by some CNS neurons.
ACh can be _______ at some synapses and _______ at others.
Excitatory and inhibitory
What synthesizes ACh?
choline acetyltransferase
What inactivates ACh?
enzyme acetylcholinesterase
What exhibits powerful excitatory effects?
Amino acids: glutamate, aspartate & GABA
Glutamate is the main what?
excitatory neurotransmitter in the CNS
Amino acids stimulate what?
most excitatory neurons in the CNS about 1/2 neurons in brain
What opens calcium channels?
binding of glutamate to receptors.
What is EPSP?
Binding of glutamate to receptors opens calcium channels.
What is GABA?
(gamma amino-butyric acid) is an inhibitory neurotransmi4er for 1/3 of all brain synapses
What are catecholamines?
norepinephrine (NE), epinephrine, dopamine (tyrosine)
What is serotonin?
concentrated in neurons found in the brain region = raphe nucleus
What is found in the raphe nucleus?
Serotonin
What is derived from tryptophan?
Serotonin
Serotonin is derived from what?
Tryptophan
What is serotonin’s role?
sensory perception, temperature regulation, mood control, appetite, sleep
induction
What gives you a feeling of well being?
Serotonin
What is Norepinephrines role?
role in arousal, awakening, deep sleep, regulating mood.
What is epinephrine?
adrenaline - fight or flight response
What is responsible for flight or fight response?
epinephrine.
What is dopamine?
emotional responses and pleasure, decreases skeletal muscle tone
______ is widespread in both CNS and PNS
Neuropeptides
Neuropeptides are excitatory as well as ?
inhibitory
Neuropeptides act as what?
hormones elsewhere in the body.
What are examples of neuropeptides?
Substance P, Endorphins, Enjephalins, dynorphins.
When are endorphins released?
During stress, exercise
what breaks down bradykinin?
endorphins
What are bradykinin?
pain chemicals
what do endorphins boost?
the immune system and slows the growth of cancer cells.
What binds on to mu-opiod receptors?
endorphins
Where are endorphins released?
By the neurons of the hypothalamus and by the cells of the pituitary.
What are enkephalins?
analgesics
What are analgesics?
enkephalins
What does enkephalins break down?
bradykinins
What is 200x strong than morphine?
enkephalins
What type of effect does enkephalins have?
pain-relieving effect by blocking the release of substance P
What are dynophins?
Regulates pain and emotions.
What is important to know about acupuncture?
may produce loss of pain sensation.
Why does acupuncture produce loss of pain sensation?
release of opioid like substances such as endorphins or dynorphins.
What are hypothalamic releasing hormones that neuropeptides?
Thyrotropin, LHRH, and Somatostatin
What are pituitary peptides?
- ACTH
- Β-endorphin
- MSH
- Prolactin
- Thyrotropin
- GH
- ADH
- oxytocin
What are gut and brain neuropeptides?
- Leucine enkephalin
- Methionine enkephalin
- Substance P
- Gastrin
- Cholecystokini
- VIP
- NGF
- BDNF
- Neurotensin
- Insulin
- Glucagon
What are neuropeptides from other tissues?
- Angiotensin II, Bradykinin,
* Carnosine, Sleep peptides, Calcitonin
Neuropeptides cause more prolonged actions such as?
small quanties are released but are more potent
Neuropeptides are synthesized as what?
Integral parts of large- proteins molecules by the ribosomes in the neuronal cell body
what happens to the vesicles of neuropeptides?
they are autolyzed
How are neuropeptides removed?
By diffusion into the surrounding tissue, followed by enzymatic destruction.
What does cytoplasmic fusion do?
Allow action potential to spread without impediment
What is quick and easy?
Cytoplasmic fusion
What does a chemical synapse produce?
Chemical intermediate neurotransmitter.
Syncytial synapse?
Cells fuse- cytoplasmic continuity
Electrical synapse?
Pre- and postsynaptic membranes in direct contact.
In the chemical synapse the first neuron does what?
Secretes a chemical substance (neurotransmitter) as the synapse.
In a chemical synapse the neurotransmitter acts on what?
Receptor proteins in the membrane of the next neuron.
What is required in electrical synapse?
Direct physical contact between cells
What are two advantages of electrical synapse over chemical?
Faster communication - instantaneous and synchronization between neurons or muscle fibers.
What is an example of electrical synapse?
heart beat
What does electrical synapses consist of?
small protein tubular structure (gap junctions) that allow free movements of ions from the interior of one cell to the next
What are three things neurons can synapse with?
Neurons, Muscle, Glands
What is the first step in an action potential?
Action potential reaches presynaptic terminal
What is the second step in action potential?
Depolarization of presynaptic terminal opens ion channels allowing calcium into cell.
What is the third step in action potential?
Ca 2+ triggers release of neurotransmitter from vesicles
What is the 4th step in action potential?
Neurotransmitter binds to receptor sites on post synpatic membrane.
What is the 5th step in action potential?
Opening and closing of ion channels cause change in postsynaptic membrane potential.
What occurs after the 5th step in action potential?
Action potential propagates through next cell.
What is the last step in action potential?
Neurotransmitter in inactivated or transported back into presynaptic terminal.
