1 | Nerve cells and nerve impulses Flashcards
(18 cards)
What are the widely branching structures of a neuron called? And what is the long, thin structure that carries information to another cell called?
The widely branching structure of neuron is called dendrites, and the long thin structure that carries information to another cell is called an axon
Which animal species would have the longest axon?
The longest axons occur in the largest animals. For example, giraffes and elephants have axons that extend from the spinal cord to the feet, nearly 2 meters away
Compared to other neurons, would an interneuron’s axon be relatively long, short, or about the same?
Because an interneuron is contained entriely within one part of the brain, its axon is short.
What are the 4 major structures that compose a neuron?
Dendrites, soma (cell body), axon, and presynaptic terminal
Which kind of glia cell wraps around the synaptic terminals of axons?
Astrocytes
Identify one major advantage and one disadvantage of having a blood-brain barrier?
The blood-brain barrier keeps out viruses (an advantage) and also keeps out most nutrients (a disadvantage)
Which chemicals cross the blood-brain barrier passively?
Small, uncharged molecules like oxygen, carbon dioxide, and water cross the blood-brain barrier passively. So do chemicals that dissolve in the fats of the membrane
Which chemicals cross the blood-brain barrier by active transport?
Glucose, amino acids, purines, choline, certain vitamins, and iron
When the membrane is at rest, are the sodium ions more concentrated inside the cell or outside? Where are the potassium ions more concentrated?
Sodium ions are more concentrated outside the cell, and potassium is more concentrated inside.
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, and the electrical gradient draws them into the cell. The sodium-potassium pump also draw them into the cell
What is the difference between a hyperpolization and a depolarization?
A hyperpolization is an exaggeration of the usual negative charge within a cell, to a more negative level than usual. A depolarization is a decrease in the amount of negative charge within the cell.
What happens if the depolarization does or does not reach the threshold?
If the depolarization reaches or passes the threshold, the cell produces action potential. If it is less tha threshold, no action potential arises
State the all-or-none law.
According to the all-or-none law, the size and the 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? Why or why not?
The all-or-none law does not apply to dendrites, because they do not have action potentials
During the rise of the action potential, do sodium ions move into the cell or out of it? Why?
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 cell by both an electrical and a concentration gradient
As the membrane reaches the peak of the action potential, what brings the membrane 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. Important note: The sodium-potassium pump is NOT responsible for returning the membrane to its resting potential. The sodium-potassium pump is too slow for this purpose.
In 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 further apart?
If the nodes were closer, the action potential would travel more slowly. If they were much farther apart, the action potential would travel faster if it could successfully jump from one node to the next. When the distance becomes too great, the current cannot diffuse from one node to the next and still remain above threshold, so the action potential would stop.
Suppose researchers find that axon A can produce up to 1000 action potentials per second, but axon B can never produce more than 100 per second. What could we conclude about the refractory periods 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 10 ms.
