Physiology Exam I Flashcards.txt

• 1) Resting State
• 2) Depolarization
• 3) Repolarization
• 4) Repolarization continues

Voltage gated Na+ channels are at rest while voltage gated K+ channels are closed. Ready to accept information.

-70 mV to -50 mV (threshold) opens Na+ channel activation gates. The influx of Na+ further depolarizes the membrane until the membrane polarity is reversed (absolute refractory period)

Depolarization also opens the K+ voltage gated channels. As K+ rushes out of cell it closes the voltage gated Na+ channels. The outflow of K+ restores membrane potential.

As AP's move down (forward only) the axon they leave behind a depolarized area to resting membrane potential while being attracted to the next negative charge to reach threshold and therefore depolarizing the axon down the vessel.

Because of the refractory period the membrane behind the AP is not ready to receive a threshold.

Ap jumping over areas covered by myelin sheath in which ions can not cross the membrane and spark and action potential, thus the "skip".

No, saltatory is faster.

• 1) presence or absence of myelin sheath
• 2) the size (diameter) of the axon

• Largest axons (4-20 um) in diameter
• Myelinated
• Speed (up to 300 mph)
• Carry info. to the CNS concerning position, balance skin sensations
• Ex: Motors neurons sending info. to skeletal muscles use type A

• smaller (2-4 um) in diameter
• myelinated
• 40 MPH
• messages from organs (less important info. than A fibers)

• Unmyelinated and under 2um in diameter, tiny
• moves at speed of 2 mph (less important than A fibers)

The site where information is transferred from one cell to another. (The neurotransmitter is released at the synapse following an AP)

• Axondendritic Synapse (why?)
• Axosomatic Synapse
• Axoaxonic synapse (Always on exam and final) Inhibiting the flow of Ca2+. It does not immediately effect a Neuron of interest, it modifies the neurotransmitter released by another neuron to the Neuron of interest.

A synapse at which neurotransmitters are released.