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Topic- EPSP and IPSP
Online Classes
Course
Biomedical Instrumentation
Presented by
Mr. Gaurav Pandey
Two Neurons
Polaried State Depolarization Repolarization Hyperpolarization
Cell membrane in
polarised state
which means the
inside of the cell is
negatively charged
due to high
concentration of
proteins and
inorganic anions
(phosphate,
sulphates), and the
outside is positively
charged due to high
concentration of
sodium ions.
When a cell is
stimulated the
permeability of its
membrane increases
so sodium ions will
get inside and inside
becomes positive
the amplitude will
slowly increases
until it reaches a
threshold point. The
voltage gated
sodium channels will
open and the
sodium inside will
increase rapidly this
will lead to reversal
polarity.
When the cell is no
longer stimulated
and the amplitude
reaches a certain
point the voltage
gated sodium
channels will close
and the membrane
will be permeable to
potassium ions to
get outside the cell
(potassium efflux)
which will lead to
more positive ions
outside again and
more negative ions
inside. This
ia repolarization.
Hyperpolarization is
a change in a cell's
membrane potential
that makes it more
negative. It is the
opposite of a
depolarization. It
inhibits action
potentials by
increasing the
stimulus required to
move the membrane
potential to the
action potential
threshold.
1. Neurons communicate with each
other by their dendrites and Axon
terminal.
2. Incoming signals are received at
dendrites terminals.
3. Outgoing Signals travels along
axon to the axon nerve terminal.
4. To achieve fast communication
over its long axon, the neuron
sends Electrical Signals from the
cell body to the nerve terminal,
along the axon, known as nerve
impulses or action potentials.
Nerve Impulses
5. Action potential is brief reversal of electrical polarity across
the cell membrane .
6. Cells are polarized, meaning there is no electrical voltage
across the cell membrane.
7. In resting phase of neuron, the typical voltage known as the
resting membrane potential is about -70 mV, the negative
value means cell is more negative on the inside.
8. At this resting state, there are concentration gradients of
sodium and potassium across the cell membrane.
9. More sodium outside the cell and the more potassium inside
the cell and maintained by sodium potassium pump.
1. Action Potential reaches the nerve terminal and depoalrizes it.
2. The Depolarization open the Ca2+ channels, enabling the Ca2+ to
enter the nerve terminal.
3. Increase in intracellular Ca2+ concentration is signal whereby
release of neurotransmitter by vesicles by exocytosis.
4. This produces high concentration of neuro transmitter in synaptic
cleft.
5. The released neurotransmitter briefly binds the the receptors of
the postsynaptic neuron.
Important Steps – Neuronal Communication
6. After the activation of receptors, transmitter must be
inactivated quickly.
7. Inactivation occurs partly by diffusion of the transmitter partly
by enzymatic degradation and partly by transporter protein.
8. There are two types of Receptors
a) Ionotropic- Fast and Precise.
b) Metabotropic- Slow and long lasting.
9. The change in membrane potential arises as a change in
synaptic influence is called as synaptic potential.
Synaptic potential and the type of Synapses: EPSP & IPSP
1. An excitatory postsynaptic potentials (EPSP) is a temporary
depolarization of postsynaptic membrane caused by the flow of
positively charged ions into the postsynaptic cell as a result of opening
of ligand-sensitive channels.
2. An EPSP is received when an excitatory presynaptic cell, connected to
the dendrite, fires an action potential.
3. The EPSP increases the neurons membrane potential. When the
membrane potential reaches threshold the cell will produce an action
potential and send the information down the axon to communicate
with postsynaptic cells.
EPSP
1. An inhibitory postsynaptic potentials (IPSP) is a
temporary hyperpolarization of postsynaptic membrane
caused by the flow of negatively charged ions into the
postsynaptic cell.
2. An IPSP is received when an inhibitory presynaptic cell,
connected to the dendrite, fires an action potential. The
IPSP signal is propagated down the dendrite and is
summed with other inputs at the axon hilllock.
3. The IPSP decreases the neurons membrane potential and
makes more unlikely for an action potential to occur. A
postsynaptic cell typically has less inhibitory connections
but the connections are closer to the soma.
IPSP