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
