Structure of neuron and propagation mechanism of nerve impulse

STRUCTURE OF NEURON AND
PROPAGATION MECHANISM OF
NERVE IMPULSE.
PRESENTED BY:
K.Kavya Priya
Reg. No: 121822201003
M.Sc. Biochemistry
Semester II
Dept. Of Biochemistry and
Bioinformatics.
GITAM Institute of Science
GITAM University.

Let’s start with the Nervous system....
NERVOUS SYSTEM:
The nervous system is a complex network of nerves
and cells that carry messages to and from the brain
and spinal cord to various parts of the body.
It consists of two main parts:
The central nervous system (CNS)
The peripheral nervous system(PNS).
The CNS consists of the brain and spinal cord.
The PNS consists mainly of nerves, which are
enclosed bundles of the long fibers or axons, that
connect the CNS to every other part of the body.
Nerves that transmit signals from the brain are
called motor or efferent nerves, while those nerves
that transmit information from the body to the CNS
are called sensory or afferent.

CELLS OF NERVOUS SYSTEM:
The nervous system contains two main categories of
cells:
Neurons:
Functional unit of Nervous system.
Communicate with other cells via synapses, that
allows rapid transmission of signals, either electrical or
chemical.
Glial cells:
The most important functions of glial cells are:
To support neurons and hold them in place.
To supply nutrients to neurons.
To insulate neurons electrically
To destroy pathogens and remove dead neurons.
To direct the axons of neurons to their targets.
GLIAL CELL
NEURON

NEURON:
There are about 86 billion neurons in the human brain, which
comprises roughly 10% of all brain cells.
The neurons are supported by glial cells and astrocytes.
Neurons are connected to one another and to other tissues
through tiny gaps called synapses. These gaps can be chemical
synapses or electrical synapses and pass the signal from one
neuron to the next.
SYNAPSE

STRUCTURE OF NEURON:
Every neuron is made of :
Cell body.
Dendrites.
Axon.
Myelin sheath.
Nodes of Ranvier.
Axon terminal.
Basic structure of
neuron.

Cell body:
The cell body, also called the soma, is the part of
the neuron that contains the nucleus and various cell
organelles.
It usually lies between axon and dendrites.
The axon hillock is a specialized part of the cell
body (or soma) that connects to the axon.
Dendrite:
Dendrite is a highly branched, generally tapering
extension of a neuron (nerve cell) that usually
receives signals from other neurons.
Axon:
Axon is the extension of cell body.
It is also called as the nerve fiber that transmit
nerve impulses away from cell body towards the
axon terminal.
Axons are usually long.
Microscopic
image of a neuron.

Myelin sheath:
The Myelin Sheath of a neuron consists
of fat-containing cells that insulate the
axon for electrical activity, it increase the
speed at which information travels from
one nerve cell body to another.
Myelin sheath consists of 80% lipid and
20% protein.
The myelin is produced by
Oligodendrocytes in CNS and by
Schwann cells in PNS.
The process of generating myelin is
called myelination or myelinogenesis.
Myelin sheath.

Nodes of Ranvier:
They are first discovered in 1878 by French
histologist and pathologist Louis-Antoine
Ranvier.
They are uninsulated and highly enriched
in ion channels, allowing them to participate
in the exchange of ions required to regenerate
the action potential.
Axon terminal:
An Axon Terminal is the very end of a
branch of a nerve's axon,conducts electrical
signals to a nerve synapse.
Node of Ranvier.
Axon Terminal.

TYPES OF NEURONS:
Structural classification:

Functional classification:
1.Sensory neurons.
2.Interneurons.
3.Motor neurons.

MECHANISM OF NERVE IMPULSE
PROPAGATION:

The major events that occur during nerve impulse propagation are:
1.Initiation of action potential.
2.Depolarization.
3.Repolarization.
Initiation of action potential.

Depolarization and repolarization.

Action potential movement through the
axon:

PLOT SHOWING DIFFERENT PHASES
OF ACTION POTENTIAL
TRANSMISSION.

SYNAPSE:
Synapse is a structure that permits a neuron (or nerve
cell) to pass an electrical or chemical signal to another
neuron or to the target effector cell.
It consist of :
Pre-synaptic neuron(which transmits the nerve
impulse)
Post synaptic neuron(which receives the transmitted
nerve impulse).
Structure of a
synapse

TYPES OF SYNAPSE:
1.Based on function:
Electrical synapse.
Chemical synapse.

Anatomical types of synapse:
Axodendritic.
Axosomatic.
Axoaxonic.
Dendrodendritic.
Dendrosomatic.

CHEMICAL SYNAPSE:
Mediated by NEUROTRANSMITTERS.

Acetylcholine mediated chemical synapse:

Structure of neuron and propagation mechanism of nerve impulse

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