1. The Nervous Tissue - Nervous SystemThe Nervous Tissue - Nervous System
Human nervous system is the most complex
system in the body formed by a network of many
billion of nerve cell called neuron and all assisted
by many more supporting glial cell
Neurons (nerve cell )
long processes respond to environmental change
(stimuli)
Glial cell (Neuroglia ) “glue cell”
short processes and support protect neurons
participate in
neural activity
neural nutrition
defence of cell in Central nervous system
2. Development of nerve tissueDevelopment of nerve tissue
Nerve system develop from the outer embryonic layer
(ectoderm) 3rd
week of human embryonic life
3. 1. Central nervous system (CNS)
Component: Brain (cerebrum and cerebellum) and
Spinal cord
Function : Overall “command center” processing
and integrating information
Location: CNS nerve cell bodies are present only in
the gray matter
1. Peripheral nervous system (PNS)
Component: nerve (Cranial and spinal) and ganglia
Function: receives and projects information to and
from the CNS
Location: found in ganglia and in some sensory
region like olfactory mucosa
Two Anatomical Divisions of the nervous
system
7. 1. Cell body (perikaryon)
Trophic center for the entire
nerve cell and is receptive to
stimuli
2. Dendrites
Many elongated process
specialized to receive stimuli
from the environment
3. Axon
Single process specialized in
generating and conducting
nerve impulse to other
cell(nerve,muscles gland cell)
Synapse:
interact with other neurons or
nonnerve cells
Responsible for the
transmission of nerve
impulse
Contact between neurons and
other effector cell by
releasing neurotransmitters
8. Structural classes of neurons :
• Anaxonic neurons
no anatomical clues to determine
axons from dendrites
functions unknown
• Multipolar neuron
multiple dendrites & single axon
most common type
• Bipolar neuron
two processes coming off cell body
– one dendrite & one axon
only found in eye, ear & nose
• Pseudounipolar (Unipolar) neuron
single process coming off cell body,
giving rise to dendrites (at one end) &
axon (making up rest of process)
9. 3 Main Types of Neuron
1. Sensory (afferent)
involved in the reception of sensory stimuli from the environment
and from within the body through presence of receptors
transmit sensory information from receptors of PNS towards the
CNS
most sensory neurons are unipolar, a few are bipolar
2. Association (interneurons)
interpretation of sensory information (information processing);
complex (higher order) functions
are all multipolar
3.Motor (efferent)
control muscle contraction and glandular secretion
(muscles/glands/adipose tissue)
all are multipolar
10. Neuroglia (glial cells)
CNS neuroglia:
• Astrocytes
create supportive framework for
neurons
create “blood-brain barrier”
monitor & regulate interstitial fluid
surrounding neurons
Metabolic exchanges
Origin : neural tube
•Oligodendrocytes
create myelin sheath around axons of
neurons in the CNS,
Myelinated axons transmit impulses
faster than unmyelinated axons
Origin: neural tube
11. •Microglia
“brain macrophages”
phagocytize cellular wastes &
pathogens
Immune-related activity
Origin: bone marrow
•Ependymal cells
produce, monitor & help
circulate CSF (cerebrospinal
fluid)
Lining of CNS
Origin:Neural tube
12.
13. PNS neuroglia:
•Schwann cells (Neurolemmocytes)
surround all axons of neurons in the PNS creating a
neurilemma around them. Neurilemma allows for potential
regeneration of damaged axons
creates myelin sheath around most axons of PNS
Orgin : neural tube
Satellite cells
support groups of cell bodies of neurons within ganglia
of the PNS
14. Things to know:Things to know:
The axons of neurons are
bundled together to form nerves
in the PNS & tracts/pathways in
the CNS. Most axons are
myelinated so these structures
will be part of “white matter
The cell bodies of neurons are
clustered together into ganglia in
the PNS & nuclei/centers in the
CNS. These are unmyelinated
structures and will be part of
“gray matter”
Ganglia
15. •Most axons of the nervous system are surrounded by a
myelin sheath (myelinated axons)
•The presence of myelin speeds up the transmission of
action potentials along the axon
•Myelin will get laid down in segments (internodes) along
the axon, leaving unmyelinated gaps known as “nodes of
Ranvier”
•Regions of the nervous system containing groupings of
myelinated axons make up the “white matter”
•“gray matter” is mainly comprised of groups of neuron cell
bodies, dendrites & synapses (connections between
neurons)
16. Blood brain barrier
Fuction :
shields the brain from toxic substances in the blood,
supplies brain tissues with nutrients,
filters harmful compounds from the brain back to the
bloodstream.
Compotents :
Capillary endothelium
Meninges
The skull and the vertebral column protect the CNS
Between the bone and nervous tissue are membranes of
connective tissue
Three layer:
1.Dura mater : outer layer lining of skull
2.Arachnoid mater : contain blood vessel
subarachoid space : filled with CSF
3.Pia mater : cover the brain
Choroid plexus
Fuction :
remove water from blood and release it as CSF