Week 9 - Cellular Activity Flashcards
(24 cards)
What are the 6 kinds of transmembrane proteins?
Carrier Proteins, Channel Proteins, Enzymes, Anchoring Proteins, Recognition Proteins and Receptor Proteins
What is a leak channel?
Gated channel that randomly opens and closes.
What is a ligand-gated channel?
Open in response to binding of (ligand) chemical stimulus.
What is a mechanically gated channel?
Gated channel which opens in response to mechanical stimulus eg/ touch, pressure, vibration or tissue stretching.
What is a voltage gated channel?
Gated channels that opens in response to voltage stimulus (change in membrane potential )
What is resting membrane potential?
The charge of the cell membrane when the cell is resting (unstimulated), created by the difference between charge across the membrane.
What are three factors that contribute to RMP in neurons?
- Na+/K+ pumps
- Most anions cannot leave cell
- Unequal distribution of ions across the plasma membrane and selective permeability to Na+ & K+
When a cell is at rest how does the net movement of sodium ions occur?
3 Na+ from cytosol bind to inside surface of Na/K pump, which makes ATP to bind to the pump (splits into ADP and P), energy from ATP splitting causes protein to change shape moving Na+ out of cell.
When the cell is at rest how does the net movement of potassium ions occur?
2 potassium ions land to outside surface of pump and cause P to be released, release of P causes pump to return to its original shape moving K+ into cell
When the cell is at rest how do potassium ions move into the cell?
2 potassium ions land to outside surface of pump and cause P to be released, release of P causes pump to return to its original shape moving K+ into cell
What is the term to describe an increase in RMP?
Depolarisation
What is the term used to describe a decrease in RMP?
Hyperpolarisation
What does an increase in permeability to potassium ions cause?
Hyperpolarisation
What does an increase in permeability to sodium cause?
Depolarisation
What is a local potential?
Small deviations in RMP that occur in response to the opening or closing of mechanically gated or ligand gated ion channels
What corresponds to the deviation of a local potential?
Strength of stimulus
What is an action potential?
Sequence of depolarisation and depolarisation along axon to send signal to axon terminal.
What can trigger an action potential?
By depolarising a local potential reaching the initial segment of the neuron if it is large enough.
What causes the rising phase of an action potential?
Caused by Na+ influx
What causes the falling phase of an action potential?
Efflux of K+ ions
How does the action potential spread down an unmylinated axon?
The active area at peak of action potential, spreads to adjacent area causing depolarisation moving toward synapse.
What is the function of refractory zones?
Potassium moves out of axon causing a zone which stops action potential from changing directions.
How is the propagation in myelinated neurons different than unmylinated neurons?
In mylnated neurons AP only occur at nodes of ranvier (gaps where axon is not insulated), known as saltatory conduction.
What is the difference between continuous and saltatory conduction?
Continuous conduction occurs in unmylinated neurons and is therefore slower than saltatory conduction which occurs in mylinated neurons.
