6. Nerve impulses Flashcards
what attract each other?
positive and negative nerve impulses
what happens when positive and negative come together
energy is released.
this potential can be measured in volts and milivolts.
how do ions play a role play a role in a nerve impulse?
there is a difference in ion between the inside and the outside of a neuron. this creates a potential difference across the membrane called the membrane potential.
what is the resting membrane potential?
-70mV
the inside is 70mV less than the out`side
what does it mean that a neuron is polarised?
7 points needed
- the concentration of Na is 10 times higher on the outside than inside the neuron
- K is 30 times greater inside the neuron than outside
- Membrane is highly permeable to K and only slightly to NA
- K diffuse out of the neuron, leaving the inside of the neuron with a negative charge
- there is not enough K inside to counteract the Na outside the neuron
- the membrane is not equally permeable to all ions and a large number of other negative ions are trapped inside the neuron e.g Cl and proteins.
- this is when the neuron is at rest
what does a sodium- potassium pump do?
maintains the resting potential difference by pumping some Na ions out of the neuron and K ions into the neuron
what is depolarisation?
when a neuron is not at rest
- it’s an all or nothing response
what occurs at a neuron when a strong stimulus is applied?
- the neuron membrane becomes more permeable to Na – sodium gates are open
- this movement is too great to be balanced by an outward movement of K
- charges become reversed
how large does the stimulus need to be?
needs to cause a change of about 15mV
how does the neuron become re-polarised?
the closure of the Na gates and the action of the sodium pump
what is action potential? what is the action called along a neuron?
depolarisation followed by re-polarisation
a nerve impulse
what is the refractory period
time during and just after an action potential in which a neuron cannot respond to another stimulus
how does the action potential move along an unmyelinated neuron?
it moves along the length of the neuron – Mexican wave motion slow movement
how does an impulse move along a myelinated neuron
impulse moves from node of Ranvier to node of Ranvier
fast movement
how do you tell the difference from a small and large stimuli?
large stimuli cause more neurons to be depolarised and cause them to depolarise more often
