Week 3 - Nervous System (signalling) Flashcards
(46 cards)
What is the typical RMP of a neuron?
-70mV
What is the function of a neuron?
Neuron are specialised cells that receive and transmit electrochemical signals.
What factors cause the resting membrane potential and what two transport mechanisms are invovled?
The resting membrane potential of -70mV is cause by the unequal distribution of Na+ and K+ ions across the plasma membrane. This is caused by:
• Na+ and K+ leak channels
• Na+ and K+ pump (3Na+ our 2 K+ in)
Why is the membrane more permeable to K+ when compared to Na+?
There are more K+ leak channels.
What prevents the Na+ and K+ gradients from dissipating considering the presence of leak channels which are always open?
The sodium potassium pump
What the major intracellular and extracellular ion?
- Intracellular: K+
* Extracellular: Na+
What is an action potential in terms of membrane potential?
Is the change in membrane potential from resting (-70mV) to a peak value of 30mV.
What channels are important for an action potential to initially occur?
Voltage gated Na+ channels
What is the threshold potential in terms of Na+ voltage gated channels?
Is the voltage at which the Na+ voltage gated channels open up to cause an influx of Na+ ions
What are graded membrane potentials?
Are membrane potentials that vary in size and direction
What causes changes in graded membrane potential?
The binding of neurotransmitter opens ligand gated channels.
What kind of ligand gated channels are bound by excitatory and inhibitory neurotransmitters?
- Excitatory - Na+ or Ca2+
* Inhibitory - K+ or Cl-
What is the difference between depolarisation and hyperpolarisation?
Depolarisation makes the membrane potential more positive, whereas hyperpolarisation makes the membrane potential more negative.
What role does calcium play at the pre synaptic axon terminal?
It is necessary for neurotransmitter release.
What is the threshold membrane potential?
-55mV
Where in the neuron is the action potential initiated?
At the axon hillock
Why is the axon potential initiated at the axon hillock?
That is where the density of the Na+ voltage gated channels is at there highest.
How does the action potential move along the axon?
Depolarization causes neighboring Na+ voltage gated channels to open which causes the action potential to travel down the length of the axon
What are the 5 stages of an action potential and what channels are open?
- Resting potential - Na+ and K+ leak channels are open
- Threshold - Some of the Na+ voltage gated channels are open
- Depolarisation - Na+ voltage gated channels open
- Reploarisation - K+ voltage gated channels open
- Hyperpolarisation - K+ voltage remain open which causes the membrane to become more negative that threshold.
What reestablishes the resting membrane potential after hyperpolarisation.
The sodium potassium pump and natural permeability of Na+ and K+ through their respective leak channels.
What is the absolute refractory period?
Is a period of an action potential in which a neuron cannot generate an action potential
What is the relative refractory period?
Is a period of an action potential in which a stronger than normal stimulus is required to generate an action potential.
What causes the absolute refractory period?
The inactivation of Na+ voltage gated channels whilst the K+ voltage gated channels remain open.
What causes the relative refractory period?
Not all Na+ voltage gated channels have recovered from inactivation and some of the K+ voltage gated channels remain open.
