Lecture 21 Flashcards
What is electricity?
Electricity is the net flow of charges from one area to another, the movement of these charges allows work to be done.
What are the two main cations used in the generation of electricity in a neuron?
Na+ and K+
How is the movement of the two main cations into or out of the cell able to change the cell’s membrane potential?
taking in Na+ from the region of high concentration (outside the cell in the ECF) will increase the cells potential difference across the membrane (makes it more positive). Releasing K+ from the region of high concentration (inside the cell in the ICF) will decrease the potential difference across the membrane (makes the difference more negative).
What methods are used by the cell to move the two main cations from inside the cell to outside(or vice versa)?
Ion channels act as cellular switches allowing the flow of ions if open, these channels are specific e.g Na+ ion channels for Na+ and K+ ion channels for K+ ions. Ion channels are largely specific due to the different sizes of the K+(bigger) and Na+(smaller) ions.
utilisation of Na+/K+ ATPase, an ion pump allows the cell to push 3 Na+ ions from low concentration to high concentration out of the cell and couples this with the bringing in of 2 K+ ions from low concentration to high concentration in the cell at the cost of ATP.
What is the main difference between ion pumps and ion channels?
Ion pumps transport ions against the concentration gradient, while ion channels transport along concentration gradients.
What is the standard resting membrane potential and what are the ion channel, (and pump) states at this point?
-70mV (e.g more negative in the cell), in this state most Na+ channels are closed and some K+ channels are open. Na+/K+ ATPase is operating.
Are neurons normally at the resting membrane potential?
No, typically the membrane potential will vary in size and time because neurons are excitable cells.
What causes the change in resting membrane potential?
The change in ion concentration of the cell in regard to the external environment, this is caused by ion channels opening and closing.
What are the 3 types of membrane potential changes? What are the primary ion channels which cause this?
Resting: a few K+ channels are open to keep the charge constant. (Occurs at roughly -70mV)
Depolarisation: Caused by opening Na+ channels letting positive charges in, the membrane potential has increased, e.g from -70mV to -60 mV
Hyperpolarisation: Caused by K+ channels opening, allowing the outflow of positive charges, increases the membrane potential e.g from -70mV to -80mV, note that repolarisation brings the membrane potential back to -70mV.
What are local potentials?
Changes in the membrane potential in only part of the cell membrane.
which membrane potential change is excitatory? Which is inhibitory?
Depolarisation is excitatory, hyperpolarisation is inhibitory.
How does electricity store energy?
The separation of opposite charges causes energy to be stored as when those charges are no longer seperated they will move towards each other, allowing work to be done.
