Hormones

Touch receptors called Meissner’s corpuscles are found in the papillary region of the dermis of the skin. When nothing is touching the skin, a voltage difference known as the (1) ___________ _____________ _____________ exists across the plasma membrane. Leakage channels, also called passive channels, allow the movement of potassium (and sodium) across the membrane. Due to the electrochemical gradient, (2) ___________________ (ion) diffuses out of the cell. Because of this and because proteins that are large, non-diffusible anions are more abundant in the cell than outside it, the fluid on the inside adjacent to the plasma membrane is – (3) negatively / positively (circle or highlight one) – charged compared to the fluid on the outside immediately adjacent to the plasma membrane. The (4) _______________________ actively moves sodium and potassium ions against their electrochemical gradients using (5)______ (energy source), thus it moves (6) __________________ (ion) out of the cell and (7)_________________ into the cell to maintain the ions’ electrochemical gradients.

When the skin is touched, the membrane is deformed and (8) ___________________-gated channels open thus allowing the – (9) efflux / influx (circle or highlight one) – of (10) _______________________ ions. This causes a membrane potential change known as (11) ___________________________, which brings the membrane potential closer to the point at which the action potential will occur. If (12) ___________________ (the voltage at which an action potential is generated) is reached at the (13) ______________ ________ (area) of the neuron, then an action potential will be generated because (14) ________________________-gated (15) ________________ (ion) channels will open. The – (16) efflux / influx (circle or highlight one) – of these ions will cause more channels to open, moving the membrane potential further from its resting condition. This is an example of – (17) negative / positive (circle or highlight