role of calcium and chloride in neurons

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can someone give me a brief summary of what calcium and chloride does in neurons and their synapses? I understand Na and K stuff, as well as action potentials just fine.

Originally Posted by icecoldstar

can someone give me a brief summary of what calcium and chloride does in neurons and their synapses? I understand Na and K stuff, as well as action potentials just fine.

http://www.wikipremed.com/mcat_cours...07010300000000
http://mcat-review.org/specialized-e...ls-tissues.php

Originally Posted by MedPR

http://www.wikipremed.com/mcat_cours...07010300000000
http://mcat-review.org/specialized-e...ls-tissues.php

those links doesnt say anything about cloride ions though. do i need to know about those for mcat?

and to clarify on the ca+,
1. there is more ca+ outside of the neuron terminus compared to inside?
2. when there is action potential, ca+ goes into the axon terminus and make it release neurotransmitters?
3. how does the cell re-establish concentration gradient after all of those things?

I don't think you need to know chloride for the MCAT - the purpose is a bit more nuanced. It kind of serves as an electrochemical gradient buffer.

1. Yes
2. Yes
3. By the Na/K ATPase and the active transport of calcium out of the cytosol

Ca+ also plays a role in regulating Na+ affinity towards receptors. An overabundance will decrease Na+ affinity and a decrease in Ca2+ will increase Na2+ affinity. This is why Ca2+ regulation is crucial to our body. A lack of will cause overexcitability of cells and can lead to many problems.

Originally Posted by loveoforganic

I don't think you need to know chloride for the MCAT - the purpose is a bit more nuanced. It kind of serves as an electrochemical gradient buffer.

1. Yes
2. Yes
3. By the Na/K ATPase and the active transport of calcium out of the cytosol

Calcium is perhaps arguably one of the most important ions and most tightly regulated ions in the neuron. It only enters in very limited quantities as it is responsible for significant changes in the physiology of the neuron, from short term effects such as LTP to long term effects such as gene up-regulation. It usually enters the cytoplasm in small regions known as microdomains - small volumes of high Ca+ Conc. It comes from the ER and membrane channels. Actually most of the Calcium is usually bound by as soon as it enters by CaBPs - Calcium binding proteins (recall proteins with EF hand region).

Chloride ion is also very important specially for OSNs. In a new neuron there are channels that pump Chloride ions INTO the neuron later on as the neuron matures the activity of these protein transporters is taken over by another pump that pumps Cl out. This is why in a developing brain GABA is an excitatory neurotransmitter but later on it is inhibitory. Read up on physiology of OSN's they are quite strange

and to clarify on the ca+,
1. there is more ca+ outside of the neuron terminus compared to inside?
Yes there is more extracellular Ca than intracellular. This is necessary for the electrochemical gradient to favor the influx of Ca into the cell upon reception of an action potential.
2. when there is action potential, ca+ goes into the axon terminus and make it release neurotransmitters?
Yes, the entry of Ca into the post-synaptic neuron induces exocytosis of neurotransmitter by a mechanism not currently understood.
3. how does the cell re-establish concentration gradient after all of those things?
Since Ca enters the neuron down its concentration gradient, work must be done to reestablish this gradient. The mechanism of this likely involves ion channel pumps that are either directly or indirectly tied to the hydrolysis of high energy molecules like ATP[/QUOTE]