lecture 9- neurophysiology III Flashcards
a synapse=
and 2 types?
=the region where the neuron meets its target cell (neuron-neuron, neuron-muscle cell)
electrical synapse and chemical synapse
electrical synapse
a gap junction where current flows directly from one cell to another
what are gap junctions made of and what do they do?
gap junctions are made of connexin proteins
they allow for very rapid communication and synchronization of activity in a network of cells
chemical synapse
electrical signals in the presynaptic cell are converted to a chemical signal for transmission to the postsynaptic cell
explain how neurotransmitter is released at a synapse
an action potential depolarizes the axon terminal
the depolarization opens voltage gated Ca2+ channels and Ca2+ enters the cell
Ca2+ entry triggers exocytosis of synaptic vesicle contents
neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell
neurotransmitter binding initiates a response in the postsynaptic cell
How is the stimulus (neurotransmitter) terminated?
when the chemicals are broken down, taken up into cells or diffuse away from the synapse
Acetylcholinesterase (ACh)= enzymatic breakdown of acetylcholine
examples of neurotransmitters
Acetylcholine
Amines:
- norepinephrine, epinephrine
Amino acids:
-glutamate, aspartate, GABA, glycine
what two things are stimulus intensity coded by?
frequency of AP firing and amount of NT released
what is the action of excitation or inhibition dependent on?
depends on the transmitter molecule and the type of post synaptic receptor
an excitatory post-synaptic potential (EPSP) is…
a depolarization
an inhibitory post-synaptic potential (IPSP) is a
hyperpolarization
two types of post-synaptic responses
Ionotropic
Metabotropic
Ionotropic response=
fast, mediated by receptor channels
metabotropic response=
slow, mediated by GPCRs
two types of pathways
divergent pathway
convergent pathway
divergent pathway
one presynaptic neuron branches to pass info to many downstream neurons
convergent pathway
many presynaptic neurons send input to a smaller number of postsynaptic neurons
presynaptic inhibition: 2 types
global presynaptic inhibition
= all targets of the postsynaptic neuron are inhibited equally
selective presynaptic inhibition
= an inhibitory neuron synapses on one presynaptic neuron and selectively inhibits one target
synaptic diseases: one example
myasthenia gravis
= attacks neuromuscular junction between somatic motors and skeletal muscles
symptoms of myasthenia gravis
muscle weakness, fatigue
caused by autoimmune-mediated decrease in acetylcholine receptors
