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Synapses.
Exam 5 - Lecture 3
| Question | Answer |
|---|---|
| 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
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