PSY 352 Lecture Notes - Lecture 6: Threshold Voltage, Tetrodotoxin, Resting Potential
Document Summary
Positively charged ions: examples: sodium (na+), potassium (k+) Negatively charged ions: examples chloride (cl-), protein molecules (a-) Movement of ions from area of higher concentration to an area of lower concentration through random motion. Differences in concentration of a substance among regions allows for diffusion. Occurs when a large concentration of first na+ ions, then k+ ions crosses the membrane rapidly. With tetrodotoxin (to block sodium channels), a slightly different action potential due entirely to the efflux of potassium is recorded. With tea surrounding the axon and blocking potassium channels, a smaller-than-normal action potential due entirely to a na+ influx is recorded. Both sodium and potassium voltage-sensitive channels are attuned to the threshold voltage of about -50mv. If the cell membrane changes to reach this voltage, both types of channels open to allow ion flow across the membrane. The voltage-sensitive sodium channels are more sensitive than the potassium channels and so open first.
