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Synapses.

Exam 5 - Lecture 3

QuestionAnswer
There are ______ neurons in the brain 100 billion
There are ______ synapses per neuron in the brain 100-10000
Synapse A junction between tow cells that propagates an electrical impulse
How do neurons propagate electrical impulses? By having a bunch of neurons in a row
Faster type of synapse? (Electrical or Chemical) Electrical Synapse; very rare in the human body
More common type of synapse? (Electrical or Chmical) Chemical Synapse
Common Gas Neurotransmitters Nitric Oxide
Common Amino Acid Neurotransmitters Glutamate, Aspartate, Glycine
Common Amino Acid Derivative Neurotransmitters GABA, Serotonin, Histamine, Epinephrine, Norepinephrine, Dopamine
Common Acetylcholine Peptides Substance P, Opioids, Neuropeptide Y
Neurotransmitter Released from the terminal ends of neurons and has an effect by itself
Neuromodulator Released from the terminal ends of neurons and modulates the effects of neurotransmitters; more commonly peptide and gas molecules
Monoamines Serotonin, Histamine, Epinephrine, Norepinephrine, Dopamine
Chatecholamine (Derivatives of Tyrosine) Monoamines Epinephrine, Norepinephrine, Dopamine
Cholinergic Neurons Release Acetylcholine
Dopaminergic Neurons Release Dopamine
Serotonergic Neurons Release Serotonin
Noradrenergic Neurons Release Noradrenaline/Norepinephrine
Adrenergic Neurons Release Adrenaline/Epinephrine
GABAnergic Neurons Release GABA
Glutamanergic Neurons Release Glutamate
Steps of Basic Neurotransmitter Release 1. Action potential activates voltage gated Ca++ channels 2. Influx of calcium via channels stimulates vesicles with stored neurotransmitters to dock and release neurotransmitters 3. Neurotransmitters drift to receptors
What is the slowest part of neuronal signaling? The time needed for Ca++ influx and vesicle docking
More synapses = _____ signal slower
Fastest reflexes have ____ synapse(s) One; sensory neuron → motor neuron
Overstimulation is which toxin? Black widow spider toxin (latrotoxin)
Understimulation is which toxin? Clostridium Botulinum bacteria toxin (botulinus toxin)
Black Widow Spider Toxin (Latrotoxin) works by: Directly STIMULATING massive vesicle docking and NT release in PNS; motor neurons to release massive amounts of ACh which leads to muscle rigidity (diaphragm contracts and gets stuck) and you die of asphyxiation
Clostridium Botulinum Bacteria Toxin (Botulinus Toxin) works by: Directly INHIBITING vesicle docking and NT release in PNS; motor neurons cannot release ACh which causes muscle paralysis (diaphragm can’t contract) and you die of asphyxiation
Negative Regulation of Neurotransmitters at the Synapse 1. Enzymes that break down NTs (inside synaptic space and inside neurons & glial cells) 2. Reuptake transporters (into neurons and glial cells) 3. Autoreceptors (negative feedback)
Where do enzymes break down neurotransmitters? Inside the synaptic area and inside neurons & glial cells
Autoreceptors Negative feedback of a neurotransmitter by that same neurotransmitter (auto = same)
Example of Glutamate Autoreceptor NMDA Receptor
Example of Norepinephrine Autoreceptor Alpha-2A or Alpha-2C
Example Acetylcholine Autoreceptor Muscarinic-2 or Muscarinic-4
Heterororeceptors Either negative or positive feedback of a neurotransmitter by a different neurotransmitter (hetero = other)
Acetylcholinesterase Inactivates ACh by hydrolysis to actetate and choline; located on postsynaptic membranes
Where is Acetylcholinesterase located? On the postsynaptic membrane
How much ACh is degraded by AChE before reaching the receptors? 50%
Each molecule of AChE degrades about ______ molecules of ACh per second 5000
How much ACh is degraded by AChE 20 mSec after receptor binding? the other 50%
Acetylcholine is degraded by AChE to: Acetate + Choline
Irreversible Acetylcholinesterase Inhibitors Toxins: Insecticides, Sarin nerve gas
Reversible Acetylcholinesterase Inhibitors Medications: Aricept (donepezil) for Alzheimers
Transporters Located on Presynaptic Neuron 1. Choline Transporter (CHT) 2. Dopamine Transporter (DAT) 3. Norepinephrine Transporter (NET) 4. Serotonin Transporter (SERT)
Dopamine Transporter (DAT) is Blocked By: Cocaine, Wellbutrin (Buproprion)
Dopamine Transporter (DAT) is Reversed By: Amphetamines
Norepinephrine Transporter (NET) is Blocked By: Cocaine, Wellbutrin (Buproprion), Straterra (Atomoxetine)
Norepinephrine Transporter (NET) is Inhibited By: Amphetamines
Serotonin Transporter (SERT) is Blocked By: Paxil (Paroxetine) [SSRI]
Transporters Located on Glial Cells Excitatory Amino Acid Transporters (Glutamate and Aspartate)
Monoamine Oxidase (MAO) Inactivates monoamine NTs by oxidation (all except histamine)
Which Monoamine doesn’t MAO inactivate? Histamine
Which Monoamines do MAO inactivate? Serotonin, Epinephrine, Norepinephrine, Dopamine
Where are MAOs located? Mostly inside presynaptic neurons
Increased MAO activity causes: Less neurotransmitters which is associated with depression
Decreased MAO activity causes: More neurotransmitters which is associated with antisocial rage behavior (Maori population has high prevalence)
Catechyl-O-Methyl Transferase (COMT) Inactivates neurotransmitters by methylation
Methylation Addition of a methyl group to a neurotransmitter so it doesn’t fir the receptor anymore (gum on pen) These molecules then cannot get out through the blood-brain barrier
Where are Catechyl-O-Methyl Transferases located? Inside postsynaptic neurons and astrocytes which clean up “escaped” NTs
Which Monoamines do COMT degrade? Catecholamines (Epinephrine, Norepinephrine, Dopamine)
Increased COMT activity causes: Less neurotransmitters which is associated with schizophrenic behavior
Decreased COMT activity causes: More neurotransmitters which are associated with aggressive behavior
Some drugs that directly inhibit COMT are used to treat what disease? Parkinson’s Disease
Where are autoreceptors located? On the presynaptic membrane
Examples of Autoreceptors Glutamate: NMDA receptors; NE: alpha-2A or 2C; ACh: muscarinic-2 or 4
Where are heteroreceptors located? On the presynaptic membrane
Heteroreceptors work on what? Calcium (which is what releases vesicles containing the other neurotransmitter)
Increase in intracellular calcium leads to __________ in release of neurotransmitters an increase
Decrease in intracellular calcium leads to __________ in release of neurotransmitters a decrease
Presynaptic Inhibition When one neurotransmitter binds to a heteroreceptor and causes a decrease in the release of a different neurotransmitter
Examples of Presynaptic Inhibition GABA can decrease release of NTs; NE can decrease release of ACh; ACh can decrease release of NE
Presynaptic Facilitation When one neurotransmitter binds to a heteroreceptor and causes an increase in the release of a different neurotransmitter
Examples of Presynaptic Facilitation Serotonin can increase the release of some NTs
Which ions can be regulates to create excitatory or inhibitory postsynaptic cells? Na+, K+, Ca++, Cl-
Two Major Receptor Types that Control Ion Channels Ionotropic Receptors and Metabotropic Receptors
Ionotropic Receptor Neurotransmitter binds and controls ion channel directly
Metabotropic Receptor Neurotransmitter controls ion channel indirectly
Four ways to make a cell more excitable (ions) 1. Open a channel to allow positively charged ions in 2. Open a channel to draw negatively charged ions out 3. Close a channel to prevent positively charged ions from moving out of cell 4. Close a channel to keep negatively charged ions inside cell
EPSP Excitatory Post Synaptic Potential (Depolarization) [inside of the cell becomes more positive]
IPSP Inhibitory Post Synaptic Potential (Hyperpolarization) [cell becomes more negative]
Which is easier to do: Hyperpolarization or Depolarization? Hyperpolarization
Excitatory Neurotransmitters Glutamate and Aspartate
Inhibitory Neurotransmitters GABA and Glycine
How many receptors does ACh have? 7
How many receptors does GABA have? 2
How many receptors does Glycine have? 1
How many receptors does Glutamate have? 4
How many receptors does Aspartate have? 1
How many receptors does Dopamine have? 5
How many receptors does Norepinephrine have? 5
How many receptors does Serotonin have? 7
How many receptors does Histamine have? 3
How many receptors does Opiods have? 4
Created by: Cyndi1087