Action Potential Flashcards
What forms nerves
Bundles of axons
What are the longest nerve axons in the human body
Sciatic nerve axons
Which type of nerve axons are in the peripheral nervous system
Schwann cells
Which type of nerve axons are in the central nervous system
Oligodendrocytes
What does the resting membrane potential rely on
The concentration gradient of potassium ions as the membrane is most permeable to these ions
In neurons what is the resting potential value
Around - 70 mV
What do all cells have in relation to potentials
They all have a resting membrane potential
What generates a negative charge in the cell membrane when potassium moves down the concentration gradient and out
Anions are left behind to create this negative charge
When does potassium stop moving out of the cell membrane during resting potential
Until the electrical attraction is as strong as the concentration gradient
What maintains the gradient of the ions within the resting potential
The sodium potassium pump which uses ATP
When is the action potential started
When the axon hillock is depolarised
What is depolarised in action potential
Is the increase in the voltage
Why does depolarisation in action potential normally happen
Due to an influx of sodium from synapse or receptor binding
What must happen to produce and action potential
The voltage must exceed threshold voltage (-55)
What is moving into the cell during action potential
Sodium which is positive therefore increase on the graph during depolarisation
How does depolarisation increase
Through the opening of more and more voltage sensitive sodium channels
What is the maximum peak voltage of an action potential
+40 mV
What does the high voltage of action potential lead to
Closing of the sodium channels and opening of the potassium channels
What happens during repolarisation
Sodium is stop at coming into the cell and potassium starts moving out reducing the positive charge within the cell as there is more potassium in the cell
What is the refractory period
After the action potential there is too little potassium within the cells therefore an even lower voltage then resting rate occurs then potassium rate gradually returns to resting state
At what state can the action potential not occur to the axon
During the refractory period
What does depolarisation of the axon membrane lead to
Depolarisation of adjacent sections of the membrane if the threshold voltage is reached - the signal is propagated and moves along the neuron
What does myelination increase
Speed and efficiency of action potentials
What is myelin made of
Lipid rich substance not permeable to ions like an insulation wire
What are the nodes of ravier
The gaps between myelin on the axon and the only areas of membrane which can be depolarised
What is saltatory conduction
It allows action potentials to appear to hop along from gap to gap in the myelination
What does myelination reduce
The degradation of the action potential over the length of the axon
What happens during multiple sclerosis
Myelin is damaged and destroyed over time
