Chapter 5 (exam 2) Flashcards
(71 cards)
What is a synapse?
Functional contacts between neurons.
What are the types of synapses?
Electrical synapses and chemical synapses.
What characterizes electrical synapses?
Gap junctions allow cytoplasmic continuity between neurons.
What are connexons?
Hemichannels formed by connexins that allow communication between neurons.
How long do connexons typically remain stable?
Stable for a couple of hours.
What can pass through large pores of connexons?
ATP, nutrients, and second messengers.
What is the speed and directionality of electrical synapses?
Fast and bidirectional flow
What is often the configuration of electrical synapses?
Often dendrodendritic with no set presynaptic and postsynaptic roles.
What is the typical function of electrical synapses?
Typically excitatory, but can also be inhibitory.
Where are electrical synapses commonly found?
In breathing and interneurons, such as in the hippocampus.
What was observed in mice without brain connexons?
Slight delay in temporal motor precision and inability to distinguish novel from previously seen objects.
What characterizes chemical synapses?
Presynaptic neuron releases neurotransmitter into the synaptic cleft.
Where are neurotransmitters typically stored?
In vesicles.
What is the active zone in chemical synapses?
A specialized area where small molecule neurotransmitters are released.
What is the synaptic cleft?
The area of interstitial fluid between presynaptic and postsynaptic neurons
What role do filaments in the synaptic cleft play?
They help maintain alignment of presynaptic and postsynaptic neurons.
What do postsynaptic neurons contain?
Receptors for neurotransmitters.
What is found in excitatory synapses?
Intracellular scaffolding known as postsynaptic density.
What are the typical events in a chemical synapse?
AP → VGCC open → neurotransmitter exocytosed in response to elevated Ca2+ → diffuse across cleft → bind to receptor → changes status of ion channel in postsynaptic cell → current generated → neurotransmitter removed → vesicular membrane recovered.
What did Loewi’s experiment demonstrate?
Chemical signaling by neurons using frog hearts, vagus nerve, and fluid while monitoring heart beat
What were the conclusions from Katz’s experiments?
A specific amount (a quanta) of ACh is spontaneously released, neurotransmitters must be packaged, and calcium plays a role in neurotransmitter release.
depolarization -> End plate potential -> current generated -> action potential (EPP smaller).
What did Boyd and Martin find in their experiments?
Distribution of MEPP amplitudes clustered around a single value, confirming neurotransmitters are released in vesicles.
What is the role of calcium in neurotransmitter release?
Calcium influx is necessary for neurotransmitter release and postsynaptic depolarization.
Katz used TTX, but an action potential in muscle fiber was still produced
What is the conclusion from studies visualizing Ca2+?
Calcium ions are necessary and sufficient for neurotransmitter release.
