This document summarizes the structure and components of neurons and nerve cells. It discusses that neurons and glia cells are the two main types of cells in the nervous system. Neurons receive and transmit information, while glia cells provide support functions. The key components of a neuron are dendrites, the cell body, the axon, and presynaptic terminals. Information flows from dendrites to the cell body and down the axon. Neurons communicate via neurotransmitters released at presynaptic terminals. The document also outlines the roles of glia cells like oligodendrocytes and astrocytes in myelination and support of neurons.
2. CONTENTS IN THIS
PRESENSATION
NEURON
STRUCTURE OF NEURON
COMPONENTS OF NEURON.
CELL
CELL ORGANELLS
DNA STRUCTURE
PROTEIN SYTHESIS-ROLE OF ER AND
GOLGI.
NERVE CELLS-GLIA AND NON GLIA .
3. Nerve cells
Two Types of Cells in the Nervous System.
1.Neurons
Receive & transmit information to other cells.
Around 100 billion to 1 trillion.
2.Glia cells
Different functions but don’t transmit information
like neurons.
Around 9x more than neurons
4. Neuron
It is the basic cell unit of the nervous system.
Cells that act as the information conducting
units of the nervous system.
7. Neuron components..
Dendrites are branching fibers with a surface lined
with synaptic receptors responsible for bringing
information into the neuron .
Some dendrites also contain dendritic spines that
further branch out and increase the surface area of
the dendrite.
Dendritic spines are the point of communication
between two neurons.
8. Neuron components..
Cell body/ Soma - contains the nucleus,
mitochondria, ribosomes, and other structures
found in other cells.
Also responsible for the metabolic work of the neuron.
9. Axon - thin fiber of a neuron responsible for
transmitting nerve impulses toward other
neurons, organs, or muscles.
Single axon, extends out of an expansion of the
cell body known as axon hillock.
Axon may have branches called axon collaterals.
Axons are covered with an insulating material
called the myelin sheath with interruptions in the
sheath known as nodes of Ranvier.
10.
11. Axon collateral divides into small branches called
teleodendria.
Knob called End foot or terminal button at
teleodendrion.
Presynaptic terminals refer to the end points of an
axon where the release of chemicals to
communicate with other neurons occurs.
13. Dendrites and axon are simply fluid filled
extensions of the cell body.
Information flows from the dendrites to the cell
body and axon .
Dendrites receives thousands of data.
But at single axon , data passes will be an average
level and summarized version. And it is regulated
by axon hillock.
14. Neuron consists of a flow of electrical current that
begins on the dendrites and then travels along the
axon to the terminals.
Each impulses reaches an end foot, the end foot
releases a chemical into its synapse, and the
chemical influences the electrical activity of the
receiving cell. Thus passes the information.
The chemical is known as Neurotransmitter.
15. Like other cells , Neuron cell contain the
following structures:
Membrane
Nucleus
Golgi body
Mitochondria
Ribosomes
Endoplasmic reticulum
a. Smooth ER.
b. Rough ER.
18. Cell has an outer cell membrane that separates it
from its surroundings and allows it to regulate the
materials that enter and leaves its domain.
The cell membrane envelops the cell body.
Its an impenetrable barrier.
Proteins embedded in the cell membrane serve as
the factory’s gate, allowing some substances to leave
or enter and denying the rest.
19. The nucleus – executive office, and a structure that
contains the genes chromosomes .
Endoplasmic Reticulum
Thin tubes that transport newly synthesized
proteins to locations around the cell.
Proteins may have ribosomes attached
20.
21. The mitochondrion - structure that performs
metabolic activities and provides energy that
the cells requires.
22. Ribosomes - sites at which the cell synthesizes
new protein molecules.
24. DNA Structure
The structure, type and functions of a cell are all
determined by chromosomes that are found in
the nucleus of a cell.
Chromosomes are composed of DNA,
(deoxyribonucleic acid).
DNA is arranged into a double helix structure.
26. There are four different types of nucleotide
possible in a DNA sequence, adenine, cytosine,
guanine and thymine (can be replaced with A, C, G
and T).
Thymine and adenine can only make up a base
pair
Guanine and cytosine can only make up a base
pair
Therefore, thymine and cytosine would NOT make
up a base pair, as is the case with adenine and
guanine.
27.
28.
29. Transcription is the first step of gene expression,
in which a particular segment of DNA is copied into
RNA (especially mRNA) by the enzyme RNA
polymerase.
30. Protein synthesis
The X marked nucleotides are an example of a DNA
sequence that would be used to code for a particular
protein, with the sequence of these nucleotides
determining which protein it is.
The sequence of these nucleotides are used to create
amino acids, where chains of amino acids form to make
a protein.
31.
32. SUPPORT CELLS
Glia are the other major components of the nervous
system that exchange chemicals with adjacent
neurons.
The general term for support cells in the CNS is glia
or neuroglia (glial cells, neuroglial cells). There are
three types of neuroglial cells.
(1) Oligodendrocytes,
(2) Astrocytes and ,
(3) Microglia.
33. Neuroglial cells
(1) Oligodendrocytes, the myelin-secreting
cells of the CNS.
(2) Astrocytes, which provide physical and
metabolic support for nerve cells.
(3) Microglia, or microglial cells (mesoglia),
which are the phagocytes of the CNS.
34. Oligodendrocytes build the myelin sheath that surrounds
the axon of some neurons.
Radial glia- guide the migration of neurons and the growth
of their axons and dendrites during embryonic
development.
Astrocytes helps synchronize the activity of the axon by
wrapping around the presynaptic terminal and taking up
chemicals released by the axon.
35. Microglia.
These are the smallest of the glial cells, with short
twisted processes. They are the phagocytes of the CNS,
considered part of the mononuclear phagocytic system.
They are believed to originate in bone marrow and enter
the CNS from the blood.
In the adult CNS, they are present only in small
numbers, but proliferate and become actively phagocytic
in disease and injury.
Their alternate name, mesoglia, reflects their embryonic
origin from mesoderm (the rest of the nervous system,
including the other glial cells, is of neuroectodermal or
neural crest origin).
36. Support cells in the PNS
The support cells of the PNS are called satellite
cells and Schwann cells.
Satellite cells surround the cell bodies of the
neurons in ganglia (ganglion cells).
These small cuboidal cells form a complete layer
around the nerve cell body, but only their nuclei
are visible in routine preparations. They help to
maintain a controlled microenvironment around the
nerve cell body, providing electrical insulation and
a pathway for metabolic exchange.
37. Schwann cells:
Schwann cells are responsible for the myelination of
axons in the PNS. A Schwann cell wraps itself, jelly
roll-fashion, in a spiral around a short segment of an
axon.
During the wrapping, cytoplasm is squeezed out of
the Schwann cell and the leaflets of plasma
membrane of the concentric layers of the Schwann
cell fuse, forming the layers of the myelin sheath.
38. The blood-brain barrier is a mechanism that
surrounds the brain and blocks most chemicals
from entering.
The immune system destroys damaged or
infected cells throughout the body.
Because neurons in the brain generally do not
regenerate, it is vitally important for the blood
brain barrier to block incoming viruses, bacteria or
other harmful material from entering.