a brief presentation on neurons and transmission of nerve impulses

1. NEURON AND TRANSMISSION
OF NERVE IMPULSES

2. THE NEURON
A neuron also known as a neurone
or nerve cell is a cell that carries
electrical impulses. They are the
basic units of nervous system.
Every neuron is made up of
a cell body, dendrites and an axon.

3. DETAILED STRUCTURE OF NEURON

4. SOME IMPORTANT TERMS
• SYNAPSE: the junction between the axon of
one neuron and dendrite, cell body or axon of
another neuron is know as synapse.
• SYNAPTIC KNOB: the swelling terminal of
axon or dendrites is known as synaptic knob.
• PRE SYNAPTIC NEURON: the neuron
carrying impulse towards synapse.
• POST SYNAPTIC NEURON: the neuron
carrying impulse away from the synapse.

5. TRANSMISSION OF NERVER IMPULSES
Nerve impulses have a domino effect.
Each neuron receives an impulse
and must pass it on to the next
neuron. To make sure that the
correct impulse continues on the
path, a series of chemical and
electrical events are carried out by
the neurons.

6. TWO THEORIES HAVE BEEN PUT
FORWARD TO EXPLAIN THE
TRANSMISSION OF NERVE IMPULSES
ACROSS THE SYNAPSE. THEY ARE;
1. ELECTRICAL TRANSMISSION THEORY
2. CHEMICAL TRANSMISSION THEORY

7. ELECTRICAL TRANSMISSION THEORY
Impulse transmission
through synapse is
accomplished by
electric current. When
the impulse reach the
pre synaptic knob, the
impulse itself act as
stimulus for the post
synaptic neuron
causing
depolarization. Now

8. POLARIZATION OF NEURON’S MEMBRANE
1. When the neuron is not
stimulated, its
membrane is said to be
polarized.
2. It means electric charge
on the outside of the
membrane is positive
while on the inside is
negative.
3. The outside of the cell
contains excess sodium
ions while the inside of

9. RESTING POTENITAL
When the neuron is
inactive and polarized,
it is said to be at its
resting potential. It
remains this way until a
stimulus comes along.

10. ACTION POTENTIAL
1. A stimulus from a
sensory cell or
another neuron
causes the target to
depolarize toward the
threshold potential.
2. If the threshold of
excitation is reached,
all Na channels open
and the membrane
depolarizes.
3. At the peak action

11. REPOLARIZATION
1. With potassium ions moving to the
outside, the membrane’s
repolarization restores electrical
balance.
2. Potassium ions move outside and
the sodium ions stay inside the
membrane.

12. HYPER POLARIZATION
1. More potassium ions are on the
outside than there are on the inside.
2. This cause membrane potential to
drop slightly lower than the resting
potential
3. The membrane have greater potential
is thus said to be hyper polarized.

13. REFRACTORY PERIOD
1. Refractory period puts everything back
to normal
2. Potassium returns inside while sodium
returns outside.
3. After the na/k pump return the ions to
the rightful sides, the neuron is back to
its normal polarized state until another
impulse comes along.

14. DIAGRAMMATIC REPRESENTATION

15. CHEMICAL TRANSMISSION THEORY
Nerve impulses are
conducted across the
synapse with the help of
chemical substances
called neurotransmitter.
The process of chemical
transmission was
discovered by Henry
(1936).

16. MECHANISM
1. Calcium gate opens.
2. Releasing a neurotransmitter.
3. The neurotransmitter binds with
receptors on the neuron.
4. Excitation or inhibition of the
membrane occurs.

17. DIAGRAMMATIC REPRESENTATION

18. Thank you