Membranes And Ions Flashcards
Are there more potassium or sodium channels in the membrane and what does this result in?
There are more K+ channels than Na+ channels. Therefore the membrane is more permeable to K+ than to Na+.
How do potassium ions leave the cell?
K+ ions leak OUT of the cell down the concentration gradient
The inside of the Na/K pump cell is positive and the outside is negative. Why is this?
K+ leaks out of the cell leaving behind negative particles.
What is the resting membrane voltage?
-70mV
What are excitable cells?
Nerve and muscle cells that have the ability to alter their membrane potential.
What type of ion channels do excitable cells have?
Gated ion channels
What happens when gated ion channels are open?
Ions can move through
What happens when gated ion channels are closed?
Ions cannot move through
What happens when the gated ion is at rest?
Gates are closed
Inside cell is negative
Outside cell is positive
Membrane is polarised
What initially happens when an Na+ excitable cell is activated?
- Na+ gates open
- Na+ ions rush into cell - down the concentration gradient
- Inside the cell is positive/Outside is negative (Membrane is depolarised)
- Na+ gates begin to close and K+ gates begin to open
What happens after an Na+ excitable cells is activated and the K+ gates open?
- K+ ions rush out of the cell
- Inside the cell is negative and outside the cell is positive (repolarised)
- Gates are now closed
What are the sequence of events for an excitable cell (include inside charge only)
- Polarised - Inside cell negative
- Depolarised - inside cell positive
- Repolarised - inside cell negative
What is the change in membrane voltage in excitable cells known as?
The action potential
Why is the membrane more negative in hyper-polarisation?
K+ gates are slow to close. Therefore excess K+ leaks out of the cell causing the membrane potential to become more negative.
