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Blood brain barrier and the sodium potassium pump

The blood-brain barrier keeps out must viruses, bacteria, and other harmful substances What is a disadvantage of a blood-brain barrier?

  • The effects were most clearly seen in the large columnar cells of the salivary gland in which the septate junction occupies only a small region of the lateral surface of the cell;
  • One possible explanation for the apparent specific morphogenic requirement of nrv2 in tracheal tube expansion is that there is a maternal contribution of nrv2 that provides enough activity to support early morphogenic processes, but not enough to support tracheal tube expansion, which occurs late in embryonic development.

The blood-brain barrier also keeps out most nutrients Which chemicals cross the blood-brain barrier on their own? When the membrane is at rest, are the sodium ions more concentrated inside the cell or outside?

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Where are the potassium ions more concentrated? Sodium ions are more concentrated outside of the cell; potassium is more concentrated inside.

  • This is of obvious importance for neurons that are involved in memory processes, but it is also true for many other types of neurons that need to operate within a particular activity or input-output range;
  • In weakly electric fish, a long-lasting shift in intrinsic excitability is responsible for a pulse integrating mechanism that is immune to frequency-dependent fluctuations;
  • In the first epithelial cells, the asymmetric localization of the Na,K-ATPase may have been achieved by anchoring the pump to asymmetrically localized adhesion proteins;
  • The voltage dependent sodium gates have opened, so sodium can move freely;
  • When the membrane is at rest, the concentration gradient tends to drive potassium ions out of the cell; the electrical gradient draws them into the cell.

When the membrane is at rest, what tends to drive the potassium ions out of the cell? What tends to draw them into the cell? When the membrane is at rest, the concentration gradient tends to drive potassium ions out of the cell; the electrical gradient draws them into the cell.

The sodium-potassium pump also draws them into the cell. What is the difference between a hyperpolarization and a depolarization?

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A hyperpolarization is an exaggeration of the usual negative charge within a cell to a more negative level than usual. What is the relationship between the threshold and an action potential? A depolarization that passes the threshold produces an action potential.

One that falls short of the threshold does not produce an action potential. During the rise of the action potential, do sodium ions move into the cell or out of it?

During the action potential, sodium ions move into the cell. The voltage dependent sodium gates have opened, so sodium can move freely. Sodium is attracted to the inside of the ell by both an electrical and a concentration gradient.

Biological Psychology Chapter 2

As the membrane reaches the peak of the action potential, what ionic movement brings the potential down to the original resting potential? After the peak of the action potential, potassium ions exit the cell, driving the membrane back to the resting potential. The sodium-potassium pump is not the answer here; it is too slow.

State the all-or-none law. According to the all-or-none law, the size and shape of the action potential are independent of the intensity of the stimulus that initiated it. That is every depolarization beyond the threshold of excitation produces an action potential of about the same amplitude and velocity for a given axon. Does the all-or -none law apply to dendrites, somata, axons, or all three? What could we conclude about the refractory period of the two axons? Axon A must have a shorter absolute refractory period, about 1 ms, whereas B has a longer absolute refractory period, about 5 ms.

During the absolute refractory period, the sodium gates are locked and no amount of stimulation can produce another action potential. During the relative refractory period, a stronger than usual amount of stimulation is needed to produce an action potential.

In a myelinated axon, how would the action potential be affected if the nodes were much closer together? How might it be affected if the nodes were much farther apart?

If the nodes were closer, the action potential would travel more slowly. If they were much farther apart, the current might not be able to diffuse from one node to the next and still remain above the threshold, so the action potentials might stop.

What evidence led Sherrington to conclude that transmission at a synapse is different from transmission along an axon? Sherrington found that the velocity of conduction through a reflex arc was significantly slower than the velocity of an action potential along an axon. Therefore, some delay must occur at the junction between one neuron and the next. What is the difference between temporal summation and spatial summation? Temporal summation is the combined effect of quickly repeated stimulation at a single synapse.

Spatial summation is the combined effect of several nearly simultaneous stimulations at several synapses onto one neuron.

Blood brain barrier and the sodium potassium pump

What was Sherrington's evidence for inhibition in the nervous system? Sherrington found that a reflex that stimulates a flexor muscles sends a simultaneous message that inhibits nerves tot he extensor muscles of the same limb.

What ion gates in the membrane open during an EPSP? What gates open during an IPSP? During an EPSP, sodium gates open. During IPSP, potassium or chloride gates open. The membrane of a cell consists primarily ofa.

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Which of the following is true of the blood-brain barrier? Which of the following is true? What is the function of radial glia? What related function do Schwann cells perform?

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What four types of chemicals are transported in this way? Why is a shortage of glucose usually not a problem?

  • Although the process of tracheal tube expansion is drastically disrupted in nrv2-null mutants, the earlier of phases of tracheal tube morphogenesis, including early tube-size regulation, are normal;
  • In Drosophila embryos, cells undergoing such a cell membrane tear form a membrane plug to reseal the gap in the lipid bilayer through a coordinated activity of the cell membrane and the cytoskeleton;
  • Among its other functions, the Na pump helps maintain the resting potential of cells, regulates cellular volume, and facilitates transport of solutes in and out of cells;
  • The many functions of vertebrate tight junctions provide possible examples of non-barrier mechanisms by which septate junctions could control tube size;
  • Tight control of activity bursts has been shown to be an important factor in regulating cycle period in other segmentally coupled oscillating networks.

What is Korsakoff's syndrome? Which chemicals can cross the membrane and which ones can't? How do a few biologically important ions cross? What is this change called? How may a neuron signal "greater than" amplitude and velocity of an action potential are independent of the intensity of the stimulus that initiated it.