Chapter 10- The neuron at rest Flashcards
What is potential energy measured in?
Volts (V)
Local ionic differences are maintained by what?
The cell’s plasma membrane
Explain the ionic composition of a resting neuron?
The neuron at rest tries to get positive ions outside the cell membrane and negative ions inside the cell membrane.
When at rest, there is a high concentration of sodium ions and chlorine ions outside the cell, plus a little bit of potassium ions
When at rest, there is a high concentration of potassium ions and negatively charged protein molecules inside the cell, plus a little bit of sodium and chlorine ions.
The net result is that the inside of the neuron is more negative than the outside.
How is the resting potential created? What are the four key mechanisms?
1- Chemical force (physical concentration gradient)
2- Electrostatic force (electrical concentration gradient)
3- Selective permeability
4- Active transport (the sodium potassium pump)
Describe the chemical force (physical concentration) part?
An ion will move from an area of high concentration to an area of lower concentration.
Describe the electrostatic force (electrical concentration) part?
An ion will be attracted to the opposite polarity.
Describe the selective permeability part?
The plasma membrane’s phospholipid bilayer has proteins that act as channels that selectively allow certain elements to pass.
They also have leakage channels which are permanently open and represent a form of passive transport.
Describe the active transport (sodium potassium pump) part?
Some proteins form channels that actively pump out sodium and pump in potassium.
This is a form of active transport, so uses energy
This energy is provided by ATP made by the cell’s mitochondria during respiration.
What is the whole process of what occurs when a neuron is at rest?
1- The sodium potassium pump sets up a chemical concentration gradient. At this point, there is lots of potassium inside and lots of sodium outside.
2- The plasma membrane is more permeable to potassium than it is to sodium.
3- The resultant leakage leads to an electrical gradient. Potassium leaves the cell, making the outside more positive. Sodium attempts to travel back into the cell to balance but is held in check by the membrane.
When the neuron is at rest, why is there still more potassium inside than out?
The movement of potassium is dictated by opposing forces.
The chemical force forces ions out, creating an electrical gradient.
At some point the electrostatic force becomes so great that any further K+ ions are held back inside the cell.
That balance point happens at around -70mV
When the neuron is at rest, why doesn’t the sodium levels eventually equalise?
Both electrochemical forces are trying to push sodium in. This is resisted by the plasma membrane but only partially.
The resting membrane potential can only be maintained by constant “bailing” by the sodium potassium pump.
Why do we have a resting membrane potential?
1- Allows a cell to function as a battery, providing a store of power to operate a variety of molecular devices embedded in the membrane.
2- Allows signals to be rapidly transmitted between different parts of a cell.
Neurons maintain a negative resting membrane potential of…
-70mV
What are nervous signals?
Are changes in the resting potential
The resting potential is determined largely by what?
The potassium ion concentration
