Final Exam Essays - 1) Calcium plays essential roles in...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
1) Calcium plays essential roles in many aspects of neuronal function. Describe two different roles of calcium in neurons with one focusing on transmitter release and the other on synaptic plasticity. Role in transmitter release (from lecture 10) - At the pre-synaptic terminal, the release of neurotransmitter is ultimately triggered by the increase in intracellular calcium, usually via the opening of voltage dependent calcium channels - Release involves a number of calcium-dependent events—like vesicle transport and docking at the membrane, priming and formation of the SNARE complex, and final fusion step that is probably mediated by calcium binding to synaptogmin. - When the AP propagates to the nerve terminal, the NA rushing in depolarizes the cell and the K rushing out to terminate the spike (but neither is directly related to release). - Instead, this opens voltage sensitive Ca channels and Ca flows down a very steep electrochemical gradient (increasing the intracellular Ca by up to 100 fold). - The increase in intracellular Ca triggers release, if the AP arrives but the Ca channels are blocked, release will not occur. Role in synaptic plasticity (also from lecture 10): - An example of synaptic plasticity is synaptic facilitation, which is intrinsic to the terminal (it does not require any other synaptic inputs). - Facilitation is common at many nerve terminals, if the AP arrives at the terminal twice in close succession; the second spike evokes more transmitter release than the first spike. - This happens, as a result of the accumulation of free intracellular Ca in the nerve terminal. - Because each spike cause the depolarization of the cell, and the influx of Ca from the opening of Ca dependent voltage channels—and because it takes time for the terminal to clear away excess Ca (due to the action of Ca buffering proteins pumping Ca into intracellular organelles)—if another spike arrives before intracellular Ca is cleared, more Ca is released on top of the remaining Ca. - Release increases with increased intracellular Ca, typically release is proportional to the 4 th power of intracellular Ca: Release= k x [Ca 2+ ] 4 3) Signal transduction mediated by G-protein-coupled receptors plays critical roles in detection of both peripheral sensory signals and central neuromodulator actions. This system is optimally designed to allow flexibility in the signals that are received and the responses that are generated in the neuron. In the space below, describe how this system works with regard to: The detection and differential responses to the major taste signals (from lecture 21) - The sweet, bitter, and umami taste sense receptors are all 7-trans-membrane G-protein coupled receptors. -
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/25/2009 for the course BIO 2220 taught by Professor Hopkins,c.d. during the Spring '08 term at Cornell University (Engineering School).

Page1 / 4

Final Exam Essays - 1) Calcium plays essential roles in...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online