Synapses and Synaptic Transmission Flashcards
What does an action potential trigger, as it reaches the presynaptic terminal?
Voltage-gated calcium channels open, allowing influx of this ion. This triggers release of neurotransmitter into the synaptic cleft.
What sort of action at the postsynaptic terminal might produce an EPSP?
Influx of sodium or calcium.
What sort of action at the postsynaptic terminal might produce an IPSP?
Influx of chlorine or efflux of potassium.
What is the difference between a neurotransmitter and a neuromodulator?
A neurotransmitter acts directly on the postsynaptic membrane; a neuromodulator is released into the extracellular fluid and can adjust the activity of many neurons.
True or false: A substance can be either a neurotransmitter or a neuromodulator, but it cannot be both.
False. A substance may act as a neurotransmitter in one location and as a neuromodulator in another. (Substance P is one example.)
What does ACh have to do with myasthenia gravis?
Myasthenia gravis is an autoimmune disease that destroys ACh receptors on skeletal muscle.
Which amino acid neurotransmitters are excitatory?
Glutamate and aspartate.
Which amino acid neurotransmitters are inhibitory?
GABA and glycine.
True or false: Amino acid neurotransmitters are typically fast-acting.
True.
How might low levels of GABA and/or glycine affect a person?
This can cause neural overactivity, which can lead to seizures, muscle spasms, and anxiety.
Name a few of the common amine neurotransmitters.
Dopamine, norepinephrine, serotonin, histamine.
True or false: Amine neurotransmitters are typically fast-acting.
False. Amine neurotransmitters are typically slow-acting.
Dopamine affects ____________.
motor activity, cognition, and behavior.
Where is dopamine produced?
In the substantia nigra and in the ventral tegmental area.
What role does NE play?
It helps maintain active surveillance by increasing attention to sensory information. (be aware of any (NE) one.)
In the CNS, where is NE produced?
Brainstem nuclei, hypothalamus, and thalamus. (Almost any (NE) thalamus.)
What can overactive NE systems do?
They produce fear and panic, even in response to things that are normal.
What role does serotonin play?
It affects mood and perception of pain, adjusts general arousal level, and can suppress sensory information.
What is the role of histamine, and where is it concentrated?
It increases arousal and is concentrated in the hypothalamus.
Name a few peptide neurotransmitters.
Substance P, calcitonin gene-related peptide, galanin, and opioid peptides.
What is the role of substance P?
It is thought to be involved in the pathology of pain syndromes where innocuous stimuli are perceived as painful. (substance P = Pathology of Pain, stimuli Perceived as Painful)
What is the role of calcitonin gene-related peptide?
It phosphorylates the ACh receptor, decreasing the likelihood that ACh will activate said receptor. (the Peptide Phosphorylates the receptor.)
What is the role of galanin?
It helps regulate food intake, cognition and moods, alertness, seizures, and pain perception. It also helps inhibit insulin release. (food=Glut, coGnition, ALertness, seizures, and pAiN perceptIoN.)
What is the role of opioid peptides?
They help decrease the perception of pain.
What important functions does NO have?
It is involved in LTP and excitotoxicity.
True or false: All of the amines and substance P bind to and activate G-protein receptors.
True.
What are receptor tyrosine kinase most commonly involved in?
Cell growth, cellular movement, and cell death.
What type of receptor do peptides and hormones typically activate?
Receptor tyrosine kinase.
Loss of nicotinic receptor-expressing neurons in the brain have been associated with what disease?
Alzheimer’s disease.
What type of receptors are nicotinic receptors?
They are ligand-gated ion channels, for sodium and calcium.
What type of receptors are muscarinic receptors?
G protein receptors.
True or false: All glutamate receptors are ionotropic.
False. Glutamate receptors may be ionotropic or metabotropic.
What are some ionotropic receptors that bind glutamate?
AMPA, kainate, NMDA.
What are the two types of receptors for GABA?
GABA-A, which is an ionotropic chlorine channel, and GABA-B, which is a metabotropic receptor.
True or false: Dopamine receptors all use second messenger systems.
True. They are used to suppress the activity of calcium channels.
What are the two types of NE receptors?
Alpha and Beta. Beta receptors in the heart increase the force and rate of heart contraction. Activation of Alpha receptors in the gut relaxes intestinal smooth muscle.
After ACh is degraded by AChE, what happens to the resulting molecules?
Choline is reuptaken through active transport, acetic acid diffuses.
Where are neuromodulators released?
At axoaxonic synapses in order to either facilitate or inhibit the release of neurotransmitter.
True or false: Nicotonic receptors are always excitatory.
True.
True or false: Muscarinic receptors are always excitatory.
False. They can be excitatory or inhibitory.
How does botulinum toxin exert its effect?
It blocks release of ACh into the synaptic cleft.
What types of receptors does NE activate?
Alpha1, alpha2, beta1, and beta2.
How do MAO inhibitors help treat depression?
They stop the reuptake of NE by MAO, allowing NE to remain in the synapse longer, exerting its effect. (Cocaine also blocks NE reuptake.)
True or false: Amphetamines block NE reuptake.
False, they stimulate additional NE release.
Which neurotransmitters do optometrists have to deal with most?
ACh, NE, glutamate, aspartate, glycine, GABA, serotonin, and dopamine.
Why is myasthenia gravis an important disease for optometrists to be familiar with?
Ptosis is the presenting symptom in many patients.
What is the difference between symptoms and signs?
Symptoms are what the patient tells us; signs are what we see.
True or false: In MG, manual elevation of one eyelid causes increased contralateral ptosis.
True.
What is Cogan’s sign?
Occuring in MG, it is when, after looking in downgaze, a patient is instructed to look foward. The eyelid will elevate and then drop slightly.
How would saccades be affected in MG?
They would slow with fatigue.
How would the orbicularis be affected in MG?
Orbicularis be weakened. Have patient try to keep their eyes shut, then try to manually open their eyelids. They will open relatively easily.
How can you test in-office for MG?
Two-minute upgaze test.
Ice test: 2 minutes improves ptosis, EOMs approve after 5 minutes.
Rest test: Ptosis improves after 20 minutes with eyes closed.
How can you treat MG?
Anticholinesterase medications, removal of thymus gland, plasmapheresis.
