nerves 2 Flashcards
what is the major ion that contributes to the RMP/resting membrane potential?
K / potassium( as there are more open K channels
According to Nernst’s equation of K+, the RMP for neurons should be approx -90mV, but that isn’t the case in reality.
Why is that?
it is -70mv due to the different membrane permeability to the ions
what happens when a action potential reaches it thresehold?
- causes opening on Na+ voltage gated channels
- Na+ goes in , causes depolarisation
-then Na+ channels close
what is the mv for when the threshold is reached ?
-55mV
describe the process of repolarization
-K+ voltage gated channels open
-K+ moves OUT
-causes repolarisation
how does hyperpolarization occur ?
due to K+ voltage gated channels being open longer than needed to
which potentials have a threshold , is it action potential or graded potential?
action potential , graded potential has no threshold- it tries to reach a thresold with EPSPs
what does the Nernest equation describe?
if the membrane was permeable to only one ion
what happens as graded potentials increase in their strength/ amplitude?
trigger more action potentials and therefore releasing more neurotransmitters
At the start of an action potential propagation the excitability of the cell is high, but once the action potential fires it drops to zero, and no action potential can be generated this is called the what?
absolute refactory period
Once the action potential passes through a location, it goes through a phase where the excitability of the cell slowly rises and the Na+ gated channels slowly recover and open, this is called the
relative refactory period
why are IPSPs and EPSPs fast?
as they use ion channels
what receptors do fast IPSPs and EPSPs use ?
ionotropic receptor
why are IPSPs and EPSPs slow ?
use G-protein-coupled receptors
what receptors do slow IPSPs and EPSPs use ?
metabotropic receptors
In the neuromuscular junction (NMJ) what does the presynaptic terminal contain within it?
contains aceytlcholine
where are the pacemaker potentials located?
in the heart
in the brain and spinal cord where is the grey and white matter located ?
brain-white matter on the inside and grey matter on the outside
spinal cord - white matter on the outside and grey matter on the inside
what distance do graded and action potentials travel?
graded potentials - short distance
action potential - long distance
How does the Na+ / K+ pump contribute to the resting membrane potential?
5mV contribution
makes inside more negative (2k+ pumped inside )
how is a compound action potential generated ?
axons based on their conduction velocity & degree of myelination
give 2 examples of demyelinating diseases and where they occur in the nervous system
multiple sclerosis in the CNS & gullian syndrome in the PNS
action potential encode stimulus intensity in their amplitude or frequency?
in their frequency
they encode a stronger stimulus by firing more action potentials
do action potential travel slowly on their own?
yes 1 m/s
