the central nervous system is formed by the brain the spinal cord and peripheral nerve the main parts of the brain %uh the brainstem the diencephalon cerebral hemispheres and serve them new runs and glial cells are the basic unit for the nervous system each neuron is composed with Phil body with the nucleus is localized one tax on and several dendrite around 100 billion neurons exist in the brain each one establishing connections with roughly 10,000southern Europe this vast number resemblethe number of stars estimated to be present in the universe electrical
signals are integrated by neurons as if the cell body with the calculator
adding excited to re and inhibitory signals the cell body sends a message through the exxon whenever a positive result
is a cheap this message propagates along the acts on
through the generation of action potential but what is indeed
an action potential let's rewind of story a little
near the cell body to explain deep inside the nature of this Nov
of
the nuron presents a dynamic electrochemical gradient
across the plasma membrane this gradient
is due to the different ion concentration inside and outside the
cell and to the several intracellular proteins
negatively charged particular focus will be given to the role of potassium
and 30 in my hands on action potentials although other irons
are involved in it fine regulation the concentration
potassium ions is higher inside the cell at its resting state
on the other hand sodium concentration
is higher outside this ion concentration gradient
is generated by the passive influx of potassium ions
driven by the excessive intracellular protein
negative charges the present the
open potassium channels during the membrane resting state
makes it more permeable to potassium and 2:30 a.m. I am
this selective membrane permeability
is responsible for the observed -62 -19 millivolt
difference during the resting potential when the new run is stimulated
member in deep polarization to more positive potential values
is observed followed by repolarization the terms the membrane back to its
resting potential and action potential
is generated by this trends membrane potential change
let the this process in close to deter
a significant number voltage sensitive sodium channels
open at the beginning the action potential with
past in with sodium current causes a sudden and localized deep polarization
the plasma membrane which intern make more sodium channels open
during membrane depolarization progressive
opening a voltage sensitive potassium channels the
in a few milliseconds the membrane potential may be reached 30 millivolt
the voltage sensitive sodium channels return to the closed state
at this voltage one more voltage sensitive potassium channels
open the outlook for potassium increases
leading to membrane repolarization this
fast potassium flux courses membrane hyperpolarization
and the resting membrane potential approaches equilibrium potential
of potassium the voltage sensitive sodium channels
close during the 3-pointer isolation the ironic
gradient is reestablish in part due to the action of the 30 in potassium pump
whose activity varied throughout the action potential
this is an important activity
that involves about 25 percent all energy consumption
interesting human being the existence
a mile in insulation coating around summit comes
make the action potential transmission faster the mile in coating surrounding
the exxon
is not continue the existence of several cups exposes the high-density
voltage sensitive sodium channels to the extracellular sign
this allows a quicker conduction up the nerve signal
in a jumping man throughout the non myelinated region
after an action potential
the voltage sensitive sodium channels stay temporarily inactive
in what is called the refractory period
the things you with that action potentials are propagated
uni-directional from the cell body to the tax on term in
in some situations and on balance between inhibitory and excitatory
signals can occur
leading to a hyperexcitability the neuronal network and epileptic crisis
may develop
when this happen several drugs that mimic the mechanism of action
awesome natural neurotoxins have been developed
in order to treat this disorder natural neuro toxins are used by several species
to defend themselves against predators as well as to paralyze the price the
poison
of the the shell species CONUS geographic's is a cocktail made of
peptides and other compounds
some of them blocking the voltage sensitive sodium channels
thus interrupting action potential propagation through the nervous L
this effect causes paralysis and has been adopted by the species
as a strategy to immobilize fast approaching another example
is the puffer fish which uses tetrodotoxin
or TTX for self defense TT
X interacts with the voltage sensitive sodium channel blocking and restraining the influx of sodium ions
through the channel and putting the transmission action potential
this knowledge
allowed the development of some anti uplifting drugs that act on the voltage
sensitive sodium channel
in a way similar to TTX although it can interact
on different channel two main by preventing the influx of 30 on my own
through the channel
it inhibits the transmission of action potential diminishing the activity
the neuronal network