6: Nervous coordination Flashcards
(22 cards)
What value is the resting potential?
-70mV
What do sodium-potassium pumps do?
Actively transport 3 sodium ions out and 2 potassium pumps in
What maintains the resting potential of a neurone?
Sodium-potassium pump, potassium ion channels (membrane not permeable to sodium ions)
What do potassium ion channels do?
Allow facilitated diffusion of potassium ions out of the neurone
Action potential sequence of events?
Stimulus, depolarisation, repolarisation, hyperpolarisation, resting potential
What does a stimulus do?
Excites the neurones cell membrane, causing voltage-gated sodium ion channels to open, sodium ions diffuse into the neurone, inside less negative
What value is the threshold level?
-55mV
What happens to the membrane if the threshold is reached?
More sodium ion channels open
What potential difference to the sodium ion channels close and the potassium ion channels open at?
+30mV
Why does hyperpolarisation occur?
Potassium ion channels are slow to close
What potential difference is hyperpolarisation?
less than -70mV
What is the refractory period?
After an action potential, the ion channels are recovering so can’t be made to open so the neurone cell membrane can’t be excited
What does the refractory period lead to?
Discrete, unidirectional impulses
What is a wave of depolarisation?
Some of the sodium ions that enter the neurone diffuse sideways, causing sodium ion channels in the next region to open
What is the all-or-nothing principle?
Once a threshold is reached, an action potential will always fire with the same change in voltage, no matter how big the stimulus is
A bigger stimulus will cause more frequent action potentials
What factors increase the speed of conduction?
Myelination, larger axon diameter, increased temperature (up to around 40)
What cell makes up a myelin sheath?
Schwann cell
What are concentrated at the nodes of Ranvier?
Sodium ion channels
What part of a neurone connects to the effector?
Axon terminal
What part of a neurone connects to other neurones?
Dendrites
What type of conduction occurs along a myelinated neurone?
Saltatory conduction
