The document presents information on the transmission of nerve impulses through neurons and synapses. It discusses how the nervous system is divided into the central and peripheral nervous systems. It describes how neurons transmit electrical signals called nerve impulses through changes in their membrane potentials. When a neuron is stimulated, sodium ions enter the neuron during depolarization, reversing the potential and triggering further sodium and potassium ion exchanges that allow the impulse to travel down the neuron. At synapses, neurotransmitters released by the presynaptic neuron can trigger signals in the postsynaptic neuron across the narrow synaptic cleft.

1. PRESENTATION ON TRANSMISSION OF
IMPULSE
THROUGH
NERVES AND SYNAPSE
Submitted to: Presented by:
Dr.D.K Sharma Bivek Rai
Dept. of Zoology M.Sc II SEM

2. Nervous system
 It is a complex collection of nerves and specialized
cells known as neurons that transmit signals between
different parts of the body.
 It is a system that coordinates and controls the
activities of the animals.
 The nervous system can be broadly divided into two
sections:
i.Central nervous system (CNS):
It consists of the brain and the spinal cord. It is in the
CNS that all of the analysis of information takes place.
ii.Peripheral nervous system (PNS):
It consists of the neurons and parts of neurons found
outside of the CNS, includes sensory neurons and motor
neurons

3. BRAIN
SPINAL
CORD
SENSE
ORGAN:
EYES
EAR etc
NERVES

4. Neuron
 Neuron is an electrically excitable cell that receives,
processes, and transmits information through electrical
and chemical signals

5. Impulse Transmission Through
Nerves
 Nerve impulse is the electrical signal which is
transmitted by neuron around the nervous system
The nerve impulse travel quickly because they are electrical
impulse and ranges from approximately 1m/s to 100m/s
The inside of a neuron’s cell membrane is negatively-
charged while the outside is positively charged
When sodium and potassium ions change places, this
reverses the inner and outer charges causing the nerve
impulse to travel down the membrane

6. Resting potential
 The state of the neuron when no nerve impulse is being conducted
 During resting potential there is an ion displacement between the
inside and the outside of the neuron (i.e. on either side of the neuron
cell membrane) as follows:
 There are more Na+ ions on the outside than on the inside
 There are more K+ ions on the inside than on the outside

7. Action Potential
 An action potential occurs when a neuron is conducting a nerve impulse
 In order for an action potential to occur, the neuron must receive sufficient
stimulation to open enough Na gates to reach the threshold level
 If sufficient Na gates are opened to reach the threshold level, other Na and K
gates will be stimulated to open
Action potential can be divided into 2 phases:
I. Depolarization
II. Repolarization

8. Depolarization
 If a neuron received sufficient stimulation to reach the membrane threshold,
successive Na gates along the entire neuron membrane will open
 The opening of the Na gates allows Na ions to move into the neuron
 The movement of Na ions into the neuron causes the membrane potential to
change from -70mV to +40mV
 As the membrane potential becomes more positive, Na gates begin to close.
At the end of depolarization, the Na gates are all closed

9. Repolarization
 At the end of the depolarization phase, K gates begin to open,
allowing K to leave the neuron
These K gates are activated at the +ve membrane potential value of
about +40mV
The movement of K ions out of the neuron produces a change in
membrane potential such that the potential becomes more –ve

10. Graphical Representation of Impulse
Transmission

11.  The junction between two communicating neurons is called a synapse;
there exists a synaptic cleft between them across which the impulse must
be conveyed.
Synapse

12. Synaptic Transmission
The process by which the impulse in the presynaptic neuron is
transmitted across the synaptic cleft to the postsynaptic neuron
is called synaptic transmission.
Synaptic cleft: The space between two neuron is called synaptic
cleft. It is approx. 20-55nm.

13.  Action potential reaches axon terminal
 Calcium channel open
 Ca2+ causes vesicles to release neurotransmitter
 Neurotransmitter crosses synapse cleft
 Neurotransmitter bind to neuroreceptors
 Triggers signals in post-synaptic neuron
Steps of Synaptic Transmission

14. Overview of the process