Download Nervous System

The State Medical and Pharmaceutical University “Nicolae Testemitanu”
Department of
Human Anatomy
The functional
Anatomy of the
Nervous System
Lecturer Globa Lilian
Medical ppt
http://hastaneciyiz.blogspot.com
Coordination and Regulation of
Body Systems
– Nervous system.
• Conducts nerve impulses maintaining
homeostasis (electrochemical).
– Endocrine system.
• Serves as messaging system maintaining
homeostasis (chemical).
Nervous & Endocrine Systems
Main Functions of the Nervous
System
• Connect the organism to the
environments
• Coordinate with all processes of the body
• Adapt organism to the environments
• Specific features of the human nervous
system distinguish man from the animals
(social life and speech)
Divisions of the NS
• CNS Central Nervous System
– Brain & spinal cord
• PNS Peripheral Nervous System
– Cranial nerves (12 pairs)
– Spinal nerves (31 pairs)
– Nervous plexus
– Nerves
Divisions of the NS
• Somatic Nervous System
• Visceral (Autonomic) Nervous System
– Sympathetic
– Parasympathetic
Somatic Nervous System
• Somatic Sensitive
– General somatic sense (touch, pain, pressure,
vibration)
– Proprioceptive sense (skin, body wall, limbs-muscles
& joints)
– Special somatic senses (hearing, equilibrium, vision,
smell)
• Somatic Motor
– Skeletal muscle
Visceral (Autonomic)
Nervous System
• Visceral sense
– General visceral: stretch, pain, temperature,
chemical changes, irritation in viscera,
nausea, hunger
– Special visceral: taste
• Visceral motor (ANS)
– Smooth muscle
– Cardiac muscle
– Glands
Nervous tissue
•
Neurons
–
–
–
–
•
unipolar neuron
pseudounipolar neuron
bipolar neuron
multipolar neuron
Supporting cells
(neuroglia)
Neuron
• The functional and structural unit
of the nervous system
• Specialized to conduct information from one part of the
body to another
-
-
Cell body (soma)
One or more
specialized, slender
processes
(axons/dendrites)
An input region
(dendrites/soma)
A conducting
component (axon)
A secretory (output)
region (axon terminal)
Dendrites
• Usually
numerous
• Branched
• Sends signals to
soma
• The ends of the
dendrites form
receptors
Axons
• 1 per soma
• Initial segment from
axon hillock
• Transmits AP away
from soma
• No Nissl bodies (no
protein synthesis)
• Neurofilaments
• Axonal transport
• Axon collaterals
• Terminal branches
• Axon terminals
Neuron
1. unipolar neuron
neuron
3. pseudounipolar neuron
neuron
a. axon
2. bipolar
4. multipolar
d. dendrite
Neuron classification by
shape
CNS Neuroglia
•
Outnumber neurons by about
10 to 1 (the guy on the right had
an inordinate amount of them).
6 types of supporting cells
•
–
1.
4 are found in the CNS:
Astrocytes
•
•
•
•
•
Star-shaped, abundant, and
versatile
Guide the migration of
developing neurons
Act as K+ and NT buffers
Involved in the formation of the
blood brain barrier
Function in nutrient transfer
CNS Neuroglia
2. Microglia
•
Specialized immune cells that act
as the macrophages of the CNS
3. Ependymal Cells
•
•
Low columnar epithelial-esque cells
that line the ventricles of the brain
and the central canal of the spinal
cord
Some are ciliated which facilitates
the movement of cerebrospinal fluid
CNS Neuroglia
4. Oligodendrocytes
• Produce the
myelin sheath
which provides
the electrical
insulation for
certain neurons
in the CNS
PNS Neuroglia
• 2 types of glia in the PNS
1. Satellite cells
•
•
Surround clusters of neuronal
cell bodies in the PNS
Unknown function
2. Schwann cells
•
•
Form myelin sheaths around
the larger nerve fibers in the
PNS.
Vital to neuronal regeneration
Myelin sheaths
• Wrapping of PM around axon
• Phospholipid bilayers form
insulation
• Gaps between Schwann cells are
nodes of Ranvier
• Allow faster propagation of AP
• Saltatory conduction
Nerve
• Bundle of axons in the
PNS
• Endoneurium around
each axon
• Loose CT
• Perineurium – CT
around a bundle of
axons
• Epineurium – CT
around a nerve
Interneurons / association
neurons
•
•
•
•
Located in CNS
>99% of all neurons
~ all multipolar
Integration of information
SYNAPSE
 Presynaptic Portion: Synaptic Button
- synaptic vesicle
- mitochondria
- presynaptic membrane: tubulin
 Synaptic Cleft
- 20-30 nm
 Postsynaptic Portion
- postsynaptic membrane: actin, fodrin, spectrin
- mitochondria
SYNAPSE
SYNAPSE
Synapses
• Presynaptic neuron
• Postsynaptic neuron
Synapses
• Axodendritic synapses
• Axosomatic synapses
• Axoaxonic synapses
Synapse structure
• Presynaptic element
– Axon terminal
– Synaptic vesicles
– Neurotransmitters
– Mitochondria
• Synaptic cleft
• Postsynaptic
elements
– NT receptors
– May generate AP
Reflex arcs
• Reflex = rapid
motor response to
a stimulus
• Unlearned
• Unpremeditated
• Involuntary
• Can involve all
muscle types
and/or glands
Knee-jerk stretch reflex
• Monosynaptic reflex arc
• Tap patellar tendon
• Stretch quadriceps
femoris
• Stimulate stretch
receptor
• AP to motor neuron
• Contract quadriceps
femoris
• Knee extends
12.18a
Withdrawal reflex
• Polysynaptic
(12.18b)
2 Main Paths Convergence and
Divergence
Saltatory Conduction
Appear the
jump from node
to node.
Speed of
impulses is
much faster
on myelinated
nerves then
unmyelinated
ones. Speed
also increases
with increase in
diameter. Ex.)
120m/s skeletal
muscle .5m/s
skin
Neuron
Communicati
on
Developmental Aspects
Development
Structure of the Spinal
Cord
Meninges of the Spinal
Cord
A Reflex Arc
Spinal Cord Reflex
Simple Nerve Path
The Spinal Cord
• The spinal cord
extends from
the foramen
magnum to the
level of the 1st
or 2nd lumbar
vertebrae
• It is enclosed
within the
vertebral
column
The Spinal Cord
• The spinal cord
is a provides a
two way
conduction
pathway to and
from the brain
• It is a major
reflex center
The Spinal Cord
• The spinal cord is protected by bone,
cerebro- spinal fluid, and meninges
– Dura mater, arachnoid, pia mater
The Spinal Cord
• Between the bony vertebrae and the dural sheath
is a large epidural space filled with a soft padding
of fat and a network of veins
• Cerebrospinal fluid fills the subarachnoid space
The Spinal Cord
• Inferiorly, the
dural and
subarachnoid
membranes
extend to the
level of S2
while the spinal
cord ends at L1
• Subarachnoid
space beyond
L1 is an ideal
site for a spinal
tap
The Spinal Cord
• The spinal cord
terminates in a
tapering cone
shaped
structure called
the conus
medullaris
The Spinal Cord
• A fiberous
extension of the
pia mater, the
filum terminale
extends
inferiorly from
the conus
medullaris to
attach to the
posterior
surface of the
coccyx
The Spinal Cord
• There are 31 pairs of spinal nerves that
arise from the cord by paired roots and
exit from the vertebral column via the
intervertebral formina
• Each segment of the spinal cord is defined
by a pair of spinal nerves that lie just
superior to their corresponding vertebra
The Spinal Cord
• The spinal cord
has obvious
enlargements
where the
nerves serving
the upper and
lower limb arise
– Cervical
enlargement
– Lumbar
enlargement
Cross Section of Spinal Cord
• The spinal cord has two grooves that mark its
surface
– Anterior median fissure / Posterior medial sulcus
Gray Matter and Spinal Roots
• These grooves run the length of the cord and
partially divide it into right and left halves
• Gray matter inside, the white matter outside
Gray Matter and Spinal Roots
• The gray matter consists of a mixture of neuron
cell bodies, their unmyelinated processes, and
neuroglia (support cells)
Gray Matter and Spinal Roots
• The white matter is composed of myelinated
and unmyelinated nerve fibers that represent
ascending, descending and transverse
pathways
Gray Matter and Spinal Roots
• The gray matter consists of mirror-image lateral gray
masses connected by a cross-bar of gray matter
called the gray commissure that encloses the central
canal
Gray Matter and Spinal Roots
• The two posterior projections of gray matter are the
posterior (dorsal) horns; the anterior pair are the
anterior (ventral) horns with lateral horns in the lumbar
and thoracic portions of the cord
Gray Matter and Spinal Roots
• The anterior horns house nerve cell bodies of the
somatic motor neurons
• These send their axons out via ventral roots of the
spinal cord to the skeletal muscles
Sectional Anatomy of the
Spinal Cord
Gray Matter and Spinal Roots
• The amount of ventral gray matter present
at a given level of the spinal cord reflects
the amount of skeletal muscle innervated
at that particular level
• Thus, the anterior horns are the largest in
the areas where the innervation for limbs
is present
– Cervical enlargement / arms
– Lumbar enlargement / legs
Figure 10.07 Meninges and Ventricles of the Brain
Nerve Plexuses
– Plexus = “braid”
– Nerves supplying the limbs form plexuses
when they leave the spinal cord
• Cervical
• Brachial
• Lumbosacral
– Lumbar
– Sacral
Nerve Plexuses
Cervical Plexus
– Formed by spinal nerves C1 – C5
• Nerves innervate the neck and shoulder region
• Phrenic nerve to the diaphragm
Cervical Plexus
Brachial Plexus
– Formed by spinal nerves C5 – C8 and T1
• Nerves innervate the arm and shoulder
– Radial nerve
– Ulnar nerve
– Median nerve (between radial & ulnar nerve)
Brachial Plexus
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Brachial Plexus
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Lumbar Plexus
– Formed by spinal nerves T12 and L1 – L4.
• Innervates the medial and anterior portions of the
thigh and lower abdominal regions
• Lateral femoral cutaneous nerve
Lumbar Plexus
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Lumbosacral Plexus
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Sacral Plexus
– Formed by spinal nerves L4 and L5, and S1
and S2
• Innervates the posterior portion of the hip, thigh,
and leg, and the genital region
• Sciatic nerve
Sacral Plexus
Sacral Plexus
Medical ppt
http://hastaneciyiz.blogspot.com