Human Physiology: Physiology of Excitable Cells

Flashcards covering key concepts of human physiology related to excitable cells, including membrane potentials, action potentials, and their mechanisms.

What are the three types of physiologic electrotonic potentials?

Graded potentials, excitatory postsynaptic potentials (EPSPs), and inhibitory postsynaptic potentials (IPSPs).

What is the typical resting membrane potential for neurons?

Approximately -70 mV.

How does a membrane potential relate to cell signaling?

Changing membrane potential can act as a signal for communication between cells.

What is the impact of myelin on action potential conduction velocity?

Myelin increases membrane resistance, allowing for faster conduction through saltatory conduction.

What does the Nernst Equation calculate?

The equilibrium potential for ions based on their concentrations inside and outside the cell.

What is the function of the sodium-potassium pump?

To maintain the concentration gradient of sodium and potassium across the cell membrane.

What is the significance of the absolute refractory period?

It is the time during which a second action potential cannot be triggered, regardless of stimulus strength.

What occurs during the depolarization phase of an action potential?

Sodium channels open, allowing Na+ ions to flow into the neuron, making the membrane potential more positive.

What role do chloride ions (Cl-) play in neuronal function?

When Cl- channels open, they cause hyperpolarization of the membrane, which can inhibit action potentials.

What is a graded potential?

A passive, sub-threshold change in membrane potential that can summate but does not initiate an action potential.

How does potassium permeability affect the resting membrane potential?

Since the membrane is more permeable to potassium, the resting membrane potential is close to the potassium equilibrium potential (EK).

What causes a rapid overshoot during an action potential?

The rapid influx of Na+ when voltage-gated sodium channels open.

Explain the concept of 'saltatory conduction'.

The jumping of action potentials between nodes of Ranvier on myelinated axons, allowing faster transmission.

What is the length constant (λ) in electrotonic potentials?

It describes how far an electrotonic potential spreads along a membrane before it diminishes.

What initiates an action potential at the axon hillock?

If the summation of excitatory postsynaptic potentials reaches the threshold of approximately -55 mV.

How does the Goldman equation help in understanding membrane potentials?

It calculates the steady-state membrane potential considering the permeability of various ions.