lesson 4 Flashcards
more positive outside the cell at 1 as stimulus hasnt yet caused channel proteins to open and let potassium and chloirde ions to pass into cell
slightly neg in cell due to negatively charged proteins
at 2 becomes positive depolarisation
3=repolarisation
4=hyperpolarisation-continuation of k+ moving out of axon
hyperpolarisation/refractory period enables unidirectional movement
for an action
add values from graphs
what is a threshold value
enough sodium moving from outside the axon to inside it
where are motor neurons located?
the CNS-carry signals from the CNS to effector glands or muscles
Where are sensory neurones located?
carry impulses from receptors to the brain and spinal chord in the CNS
where are relay neurons located
entirely in the CNS
what factors in the axon affect action potential speed
temp-higher temp=higher speed of ap
diameter of axon-larger diameter, faster the ap
(temp effects rate of diffusion)
(axons with a smaller diameter have a larger SA:V ratio so larger quantity of of ions leak out the axon)
1) Describe resting potential (distribution of ions/charge/which voltage gates are open or closed)
more sodium and potassium ions outside of axon than inside K and NA gates closed
cell membrane more - charged than outside
Na outside and K inside
but to reach resting potential K flows out of cell
2) Describe depolarisation (distribution of ions/charge/which voltage gates are open or closed)
stimulus causes NA channel proteins to open
sodium ions flow into cell membrane and CL flow out
more positive inside membrane than outside
creates action potential?
3) Describe repolarisation (distribution of ions/charge/which voltage gates are open or closed)
NA channels closed and K voltage gated channels open so K ions can flow out of the cell
cell membrane becomes more negatively charged than outside again
4) Describe hyperpolarisation (distribution of ions/charge/which voltage gates are open or closed)
more ions outside of cell than at resting potential
very negative charge inside axon
K voltage gates open
means action potential is unidirectional- can only spread in 1 direction so section of the axon wont react to any further stimulus until resting potential is restored.
continuation of repolarisation
5) Describe saltatory conduction
action potential jumps between nodes of ranvier speeding up transmission of nerve impulse.
6) Describe the all-or-nothing principle/threshold value
either an action potential is or isnt reached
stimulus strong enough that a certain amount of sodium ions move into cell then action potential is reached and signal will be spread, if not it wont be
action potentials either happen or they dont
depolarisation can happen at different levels
difference between an action potential and depolarisation
wave of depolarisation triggers the action potential.
action potential is the electrical impulse that spreads down a neurones axon
wave of depolarisation is the initial change in membranes potential
depolarisation can happen at any level but only if it reaches a certain threshold will it trigger an action potential
(wave of depolarisation to do with heart not this)
What is a membrane potential
membrane potential is the difference in charge inside and outside a CELL NOT MEMBRANE
