Nerves 3 Flashcards
How much does the resting membrane potential have to be depolarised to to fire an action potential?
about -55mV
What is a generator potential?
a graded potential occurring at sensory nerves e.g pressure on skin
What is an excitatory postsynaptic potential?
a potential that will cause the cell to fire
What is an inhibitory postsynaptic potential?
a potential that will inhibit the cell from firing
What is the graded potential that occurs in the muscle after stimulation by a motor neurone called?
endplate potential
What is the function of graded potentials?
to determine when an action potential is fired
What are 4 examples of graded potentials?
generator potentials - at sensory receptors
postsynaptic potentials- at synapses
endplate potentials - at neuromuscular junction
pacemaker potentials - in pacemaker tissues
What are 4 key properties of graded potentials?
- decremental
- are graded
- can be depolarising or hyper polarising
- can summate
Why are graded potentials decremental?
current leaks out
What is meant by the fact that graded potentials are ‘graded’?
signal stimulus intensity in their amplitude
How can a graded potential cause an inhibitory postsynaptic potential?
by opening Cl- channels (this makes the cell more negative, preventing an AP from being generated)
How are fast IPSPs generated?
by opening chlorine channels
How are slow IPSPs generated?
by opening potassium channels to allow the potassium to leave
What are the names of two neurotransmitters that will cause an IPSP?
GABA and Glycine
How do transmitters depolarise cells?
open type of channels permeable to potassium and sodium - more sodium gets in than potassium gets out therefore causing the cell to depolarise
How are fast EPSPs generated?
by opening sodium/ potassium channels
How are slow EPSPs generated?
blocking leaky potassium channels
What are postsynaptic potentials produced by?
a neurotransmitter opening or closing ion channels - ligand gated ion channels
What is meant by the fact that graded potentials can summate?
they can add to each other
What is temporal summation?
when input from the same stimulus adds to each other
What is spatial summation?
when two different stimuli generate EPSPs and they add to each other
What is synaptic integration?
taking all the inputs and deciding whether to fire an action potential
Why would EPSPs received nearer the axon hillock have greater influence on whether an action potential is fired?
graded potentials are decremental and so the nearer the graded potential is to the axon hillock where the AP is going to be generated then the more graded potential that is going to reach the axon hillock and therefore the larger the response than if it were further apart
