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17 Cards in this Set
- Front
- Back
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How are the intracellular and extracellular fluid different in terms of ionic composition?
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The intracellular fluid contains more K+ ions and negative protein ions, while the extracellular fluid contains Na+ and Cl-
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Why are there still some K+ ions in the extracellular fluid but no Na+ in the cytosol?
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The cell membrane contains leaky channels which K+ flows out of, but there is no easy way for the Na+ to get in
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Is the ICF or the ECF more positive?
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The ECF is more positive and the ICF is more negative, due to the proteins inside the cell and the K+ leaky channels.
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Describe the resting membrane potential (polarised state)
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There is more K+ on the inside, more Na+ on the outside. The outside is more positive, the inside more negative. The difference in charge between the two is -70mV. The cell is ready to leap into action.
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What is the action potential?
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The signal that changes the charge of the cytosol, causing depolarisation
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What is propagation?
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The action potential jumping between the nerve cells
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What transmits the action potential (AP)? What begins the AP?
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Dendrites transmit the AP but only the axon can start it
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Describe depolarisation
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When the difference in charge reaches -60mV, the sodium channels open, causing Na+ to rush inside the cell. This causes the charge to rise until it reaches 30mV, when the sodium gate closes and the potassium gate opens, causing K+ to leave the cell.
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What is repolarisation?
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When Na+ has stopped entering the cell, and K+ is leaving.
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Describe hyperpolarisation
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Too much potassium has left the cell! Membrane potential is now -90mV
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How is hyperpolarisation solved?
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The sodium-potassium pump activates, pushing out Na+ and bringing in K+. For every 3 Na+ ions pushed out, 2 K+ ions are pulled in, mimicking the passive diffusion process, and returning the RMP to -70mV
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What is the absolute refractory period? What is the relative refractory period?
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The absolute refractory period is when the sodium gates are open, and it is impossible for another impulse to start. The relative refractive period is during repolarisation. Another impulse can only begin with a very strong stimulus.
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What is a synapse?
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The gap between the presynaptic and postsynaptic cell.
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What happens when the action potential reaches the end of an axon?
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The AP will depolarise the synaptic terminal, causing the voltage-gated calcium channel to open and Ca2+ to enter the pre-synaptic cell.
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What is the role of ACh?
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ACh is the neurotransmitter that is activated by Ca2+ and leaves the synaptic vesicles to cross the synaptic cleft and fuse post-synaptic membrane, in a process called exocytosis.
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How is the post-synaptic membrane depolarised?
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Along the PSM are chemical-gated channels, which are activated when ACh binds with them and open, causing Na+ to enter the post-synaptic cell.
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What happens next?
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The ACh is removed by the enzyme AChE, and the action potential is propagated along the rest on the PSC (now the pre-synaptic cell!!)
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