LG 1.10 Synaptic Transmission Flashcards
What must the membrane potential rise to to cause another action potential?
-50 mVs
What is EPSP?
Change in membrane potential towards an action potential (-50 mV) [Na+ moving in or K+ moving out]
What is IPSP?
change in membrane potential away from an action potential. Usually this is from Cl- moving in the cell.
What is summation?
Multiple EPSPs combine to raise the membrane potential to threshold (-50mV)
What are the two types of summation?
Temporal and spatial
What is a temporal summation?
One neuron causing multiple EPSPs within a short time frame.
What is a spatial summation?
At least two neurons causing an EPSP around the same time
What is Lambert Eaton Syndrome?
Autoantibodies to the voltage gated Ca+2 channels on the presynaptic terminal
What is the effect of Botulism Toxin?
Destroys SnRPs, which prevents synaptic vesicle from releasing neurotransmitters
What is the effects of Myasthenia Gravis?
Autoantibodies to the postsynaptic acetylcholine receptors.
Define a non-gated ion channel
- “Open” all the time
- Also known as leak channels
- Used to help control the resting membrane potential.
- Think of the potassium leak channels with regular action potentials.
Define Voltage Gated channels
1) Respond to changes in membrane potential.
2) Found on
a) Axons of nerve cells (Na+ gated)
b) Presynaptic nerve endings (VG-Ca+2 channels releases NTs)
What is a mechanically gated channel?
- These channels respond to environmental stimuli
- Ex: Pressure receptors found in the skin such as pacinian corpuscles, merkel discs, meissner’s corpuscles, and ruff ini endings. Hair cell transductive mechanochannels responding to sound.
What are Ligand channels?
- Ion or molecule that forms a complex
- Neurotransmitters or ligands.
- Divided into metabotropic and ionotropic
What are the general characteristics of Metabotropic?
- G-protein coupled
- Made up of seven transmembrane proteins
- Wide array of effects [illustrated on the next slide]
- Activates secondary (G-proteins) proteins that will open an ion channel, enhance transcription, or cause the release of other enzymes.
- Slower response
- One unit as a seven transmembrane (requires only one gene)
What are the general characteristics of ionotropic receptors
- Fast Excitatory or Inhibitory
- Local effects (once the ligand binds the channel opens)
- Fast response
- Multiple protein subunits (influenced by multiple genes)
What are the general characteristics of Nicotinic Acetylcholine Receptors?
- Ionotropic
- Peripherally on postganglionic neurons
- Located on skeletal muscle end plates
- Adrenal Gland
What are the general characteristics of muscarinic acetylcholine receptors?
- Metabotropic
- Located on target organs for postsynaptic neurons of parasympathetic nervous system and sweat glands
Which receptor do most anti-cholinergic drugs target?
Most anti-cholinergic drugs used are muscarinic and not nicotinic
Which receptor do most anesthetic drugs target?
Nicotinic
What is the only type of postsynaptic receptors found at the ganglionic synaptic clefts?
Nicotinic
What would happen if you game a anti-nicotinic drug?
Both the sympathetic and parasympathetic nervous systems would be depressed.
What happens if you destroy or inhibit acetylcholinesterase or something that acts as a nicotinic agonist?
- Prevents the muscles from relaxing (unregulated high Ach levels)
- Ex: Organophosphates (insecticides – think of farmers), Nerve gas, nicotine
What are examples of anti-cholinergic drugs?
- Low potency typical antipsychotics
- Atypical antipsychotics
- Tricyclic antidepressants (TCA’s)
- Anti-histamines 1st generation
- Anti-muscarinic drugs for asthma
- Scopolamine – used for motion sickness
What do triptans work against?
Are 5-HT1B & D agonists
What do Ondansetron (anti-emetics) do?
5-HT3 blockers
What body activities is serotonin involved with?
-Emesis, GI motility, Anxiety, GI smooth muscle contraction, sleep, feeding, thermoregulation, hallucinations
What are the types of Serotonin receptors?
- 7 families of receptors (numbered 1 – 7)
* All are G protein receptors (metabotropic) except 5-HT3, which is ionotropic
What is Tyrosine Kinases?
Tyrosine kinases becomes activated when a growth factor, cytokine, or insulin binds to the receptors. Growth in general is a multicellular activity that needs to be coordinate so it makes sense that growth factors activates a pathway with a lot of components. Insulin also uses RTK and if your body has decreased amounts or becomes desensitized to insulin as with diabetes you will have a decrease in signaling from receptor tyrosine kinase. If you decreased signaling from receptor tyrosine kinase it will affect a lot of different pathways, which helps to explain why complications from diabetes are with multiple organs.
What are the main factors of Receptor Tyrosine Kinase?
- Ligands associated with RTKs include: growth factors, cytokines, and pancreatic beta cells for insulin.
- There can be up to 10 different responses after these ligands bind to RTKs. This indicates that there are multiple ways to regulate growth.
- RTK mutations are associated with cancers if a mutation causes the RTK to become constantly activated.
What is the end activity of activation of Receptor tyrosine kinase?
Will lead to the activation of a protein that binds to a promoter region of DNA to upregulate transcription.
