Following an Action Potential, Potassium Channels open up driving membrane potential toward equilibrium. These voltage-gated Potassium channels differ from leak-potassium channels in that they are normally __________ during resting potential, but __________ in response to depolarization. (Thus the term "voltage-gated").
The "Undershoot" Phase following an Action Potential is caused by _____________.
The tree-like branches of a neuron are called ______________
The long thin structure of a neuron that carries information TO another cell is called the __________
Which animal species have the longest axons?
Longest axons occur in the largest animals.
ex giraffes & elephants from spinal cord to feet, ~2 meters
What is one major advantage of the blood brain barrier & one major disadvantage
Advantage: Toxins and viruses don't go to the brain
Disadvantage: Needed medications or nutrients don't get to brain
Which chemicals cross the blood-brain barrier PASSIVELY?
Small, un-charged molecules:
water, oxygen, carbon dioxide, chemicals that dissolve in fats of membrane
Which chemicals cross the blood-brain barrier via ACTIVE transport?
Glucose, amino acids, purines, choline, some vitamins, (A & D), iron, some hormones
Heroin exerts faster effects on the brain than morphine. What can we infer about those drugs?
Heroin crosses the blood-brain barrier.
When a neuron membrane is at rest, the sodium ions more concentrated __________ of the cell. The Potassium ions more concentrated __________ of the cell
When the neuron membrane is at rest, what tends to drive the potassium ions OUT of the cell? What tends to draw them INTO the cell?
OUT: Concentration gradient (higher concentration inside, driving them out)
INTO: Electrical gradient (post-AP after cell is depolarized, opens K+ voltage-gate channels to send cell back to neutral)
Also, the sodium-potassium pump.
What is the difference between HYPERPOLARIZATION and DEPOLARIZATION?
Hyperpolarization: Makes cell more NEGATIVE
Depolarization: Makes cell more POSITIVE (by decreasing amount of negative charge) (-/-) = (+)
During the rise of the action potential, do sodium ions move INTO the cell or OUT of it? Why?
Move INTO it.
The voltage-dependent sodium gates open, 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 it down to the original resting potential?
Sodium Channels CLOSE- causing sodium levels to drop. Voltage-gated Potassium Channels OPEN - Potassium ions EXIT the cell, carrying a POSITIVE charge. Enough potassium ions leave to drive membrane BEYOND usual resting level to short hyperpolarization. Eventually, the sodium-potassium pump removes the higher amount of sodium and adds more potassium to bring back to normal resting level.
What are the "3 Mantras"?
1. Biology is NOT determinism
2. Brains produce behavior AND behavior changes brains.
3. Multiple approaches COMPLETE, not COMPETE
In most cases, neuron cluster OUTSIDE the CNS is called a ganglion, & cluster INSIDE is called a nucleus. The exception to this is the __________ _____________, which is located IN the CNS.