NB505 - Focus Areas Exam One
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- What drug can be used to turn off voltage gated Na+ channels?
- ttx (tetrodotoxin)
- What durg can be purfused into a neuron to turn off voltage-gated Na+ channels?
- QX-314
- What drug can be used to block electrical junctions?
- Octanol (alcohol)
- What drug shuts off NMDA channels?
- AP-5
- What drug shuts off GABA channels?
- bicuculline
- What are the fundamental points of the Stuart and Sakmann paper?
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1) APs backpropagate
2) The backpropagated wave uses active propagation as Na+ channels in the dendrites help to sustain the wave.
3) The "APs" in the dendrites caused by the backpropagating AP are not all-or-nothing. - What are the fundamental points in the Galarreta and Hestrin paper?
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1) Inhibitory henrons are critical in the coordination of cortical activity.
2) Electrical synapses between inhibitory cells => synch of firing - Give three characteristics of electrically coupled cells regarding firing, frequency/coupling and coupling ratios.
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1) Electrically coupled cells tend to fire all-or-none.
2) Low-freq signals => higher coupling ratios.
3) Coupling ratios are usually small, e.g. in the 1 to 10% range. - Within the hippocampus, what type of cells will be heavily connected via electrical junctions and which will not?
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1) Interneurons will be heavily electrically connected.
2) Pyramidal electrical coupling is sparse. - What are the fundamental points of the Gibson et al. paper?
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1) In the neocortex there is an inhibitory network of Fast Spiking (FS) neurons which are electrically coupled.
2) In the neurocortex there is an inhibitory network of Low-Threshold (LTS) neurons that are electrically coupled.
3) There is no electrical coupling between FS-LTS. - What are the distinctions between sodium generated APs and calcium generated APs?
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Sodium
1) All-or-none
2) Distinct threshold for AP
3) Short duration - ~ 1 ms
Calcium
1) Longer duration - 10s of ms
2) Not all-or-none
3) No distinct threshold - What would be seen in intra-dendritic recordings during APs in cerebellar Purkinje cells and hippocampal pyramidal cells?
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Purkinje cells have a low number of Na+ voltage-activated channels in the dendrites so backpropagated APs will only see passive propagation.
Hippocampal pyramidal cells have Na+ voltage-activated channels in the dendrites so there will be active backpropagation of APs. - What are the three different tests to tell if two neurons are electrically connected?
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1) Direct (probe in each cell)
2) Indirect (send signals back along axons and see what is coupled to what)
3) Tracer coupling (inject a dye and see if it goes from one cell to another) - Contrast electrical vs. chemical synapses.
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distance between cells: 3.5 nm (elec) vs. 20-40 nm (chem)
Cytoplasmic continuity (elec) vs. none.
Gap-junction channels (connexons) vs. pre-synaptic vesicles, active region, post-synatpic receptors.
Ion current (elec) vs chemical transmitter
Usually bi-directional (elec) vs. unidirectional. - Trace the electrical pathway within the hippocampus.
- Performant pathway => granule cells => CA3 pyramidal cells via mossy fibers => CA1 pyramidal cells via Shaffer collaterals.
- What are the two things needed to get LTP in the hippocampus?
- Synaptic stimulus coincides with strong depolarization.
- State how to form a LTP in the hippocampus and the details of what happens.
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1) Apply low freq stimulus => high freq stimulus (50-100 stimulii at a rate of 100/sec) => how freq stim.
2) Apply stimulus to multiple inputs in the dendritic tree. AMPA channels form EPSPs.
3) Get temporal and spacial summation => AP.
4) AP backpropagates => strong depolarization => NMDA channels turn on => Ca++ entry => LTP. - What are the four basic firing patterns?
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Slow regular
Fast regular
fast irregular
burst - What two nucleii make up the magnocellular cells?
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supraoptic nucleii
paraventricular nucleii - Where are magnocellular cells located - soma and terminals? Where are the hormones dumped?
- They are located in the hypothalimus and there terminals are in the posterior pituitary. The hormones are dumped directly into the bloodstream.
- What hormones are released by the magnocellular cells?
- Oxytocin and vassopressin.
- Contrast the release of oxytocin to vassopressin
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Oxytocin: released in pulses. The magnocellular cells burst in sync to produce a pulse of oxytocin.
Vassopressin: Release is graded and async. - Given the timeline/signals for release of oxytocin during nursing of rat pubs.
- Signal from suckling => sync bursting in magnocellular cells => release of pulse of oxytocin into the blood stream => release of milk (about 10 seconds later).
- Give the timeline/signals for the release of oxytocin during uterus contractions.
- Contraction signal from uterus => sync bursting in magnocellular cells => release of oxytocin into blood stream => stimulation of contractions.
- Give the drivers and targets for release of vasopressin.
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Decrease osmolarity => async stim. magnocellular cells => releases vasopressin.
Decrease blood volume or BP => async stim. Magno. cells => release of vasopressin.
Target: constriction of arterial smooth muscle; reabsorption of water by kidneys. -
What is one major hormone released by the parocellular cells? G___
What is one of the hormones that this causes to be released? L___
What is a characteristic of firing of the parocellular cells? -
GnRH (gonotrophic releasing hormone).
Leuteinizing hormone (LH).
They fire in sync (neuron to neuron) bursts. - What is the anatomy of the parvocellular cells?
- PV cells are located in the hypothalamus and send a process into the median eminence where hormone is released into the portal vascular system and subsequently affects the anterior pituitary.
- Looking intracellularly, what will be seen in a parvocellular cell when GnRH is about to be released?
- The frequency of APs associated with a burst increase.
- What is a DAP and what is its significance?
- DAP - depolarizing after potential. If an AP occurs their will be a sharp depolarization followe by a fast repolarization with a slower repolarization tail. During this tail, the membrane is still depolarized and this is a DAP. If multi APs occur together and temporally sum, then the DAP will show a rising membrane potential which can lead to a plateau. During this time period, the membrane is closer to threshold and it is possible for a burst of APs to occur.
- What is an example of the use recurrent inhibitory feedback circuits?
- Allow pyramidal cells to be extensively interconnected w/o leading to positive feedback that could result in a seizure if unchecked.
- What drug blocks AMPA channels?
- CNQX
- What are modern approaches to studying the electrophysiological mechanisms of mammalian hypothalamic neuroendocrin cells.
- There are various transgenic mice breed to express a given protein for a hypothalmic cell. For instance, eGTP breed into transgenic mice to be able to distinguish GnRH cells. Use fluorescene to see these. Use biocytin to see cell being probed.
- What neurotransmitters are normally associated with neuroendocrine cells?
- glutamate and GABA-A
- What are two of the key parameters measured in EEGs?
- Amplitude and frequency.
- What can induce paroxysmal depolarization?
- Block inhibition
- What is observed during a myoclonic seizure?
- Rapid contraction of muscles (rapid and short)