Electro chemical impulses
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How are the electrical chemical impulses (messages) sent and what are the ions
Neurons send messages electrochemically, these ions are Na+ cl- k+ and ca2+
how is a voltage difference produced (easy)
having seperate positive and negative charges
what are voltage differences a result of
the pumping of sodium ions out of the cell and potassium ions into the cell through the Na+ and k+ pump
what is different about the pumping of sodium and potassium in and out
when potassium ions are pumped in they are ready to diffuse back out as the membrane is permeable for them but when sodium is pumped out, they cant come back in as the membrane is not permeable for them.
Nerve impulse 2 points
Nerve membrane contains Na+ and K+ voltage gated channels, they can open or close -opening and closing of gated channels affects the movement of ions which affects the charge and concentration across the membrane
what is the resting potential of a neuron
The resting potential of neurons is about -70 mV. At resting potential concentration of ions is kept constant through Na+/K+ pumps. When the threshold is reached, the Na+ gated channel are opened.
what is another way of saying action potential
nerve impulse
what causes the action potential and what initiates it
positive ions moving in and then out of the neuron at certain spots along the neuron Initiated by a stimulus ex prick
what is the action potential initiated by
a stimulus ex pin, prick, ight, heat or sound above a certain threshold
why are Na+ and K+ channels called voltage gates
because they act only when the surrounding area reaches a certain voltage
what is the threshold
-55mv
what happens when k+ ions pour outside neuron
hyperpolarization -90mv
how long does the refractory period last
1-2 msec
briefly explain the all or none law
it basically states that the axons fire metaphorically like a gun. if they do fire the size, speed etc is always the same and therefore stronger stimulus have a higher intensity by having a higher frequency (firing more frequently) ex # of action potentials per second
channel inactivation
following depolarization the sodium channels begin to close, called channel inactivation