The document provides information about the nervous system, including its main divisions and components. It discusses the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which connects the CNS to muscles, glands, and sensory receptors. It describes the development of the brain from early embryonic stages. It also summarizes the anatomy and histology of the spinal cord, including its gray and white matter, dorsal and ventral horns, tracts, and central canal. Additionally, it discusses the meninges, spinal nerves and ganglia, and reflex arcs in the somatic and autonomic nervous systems.

1. Nervous system
Spinal cord
Spinal ganglion
Somatic reflex arc
Autonomic reflex arc

2. Nervous system
 To detect, analyze, utilize & transmit all
information generated by the sensory stimuli
(such as heat & light) & by the mechanical
& chemical changes that take place in the
internal & external environment.
 Controls and integrates all body activities
within limits that maintain life.
 To organize & coordinate most functions of
the body, especially the motor, visceral,
endocrine & mental activities.

3. Development of the NS
 Stage of 3 brain “bubbles” (at the end of the 4-th
week of embryonic development)
 Prosencephalon
 Mesencephalon
 Rhombencephalon
 Stage of 5 brain “bubbles” (6-th week)
 Prosencephalon
 Telencephalon --- cerebral hemispheres
 Diencephalon & nervous components of the eye
 Mesencephalon --- arise reflex centers of the
vision, hearing & tactile sensitivity
 Rhombencephalon
 Metencephalon --- cerebellum, brain stem
 Myelencephalon --- medulla oblongata

5. Anatomical Nervous System Divisions
 Central nervous system (CNS)
– consists of the brain and spinal cord
 Peripheral nervous system (PNS)
– consists of cranial and spinal nerves that
contain both sensory and motor fibers
– ganglia (collections of neurons outside the
CNS)
– motor & sensory nerve endings
– connects CNS to muscles, glands & all sensory
receptors

6. Functional Subdivisions of the PNS
 Somatic (voluntary) nervous system (SNS)
– neurons from cutaneous and special sensory receptors
to the CNS
– motor neurons to skeletal muscle tissue
 Autonomic (involuntary) nervous systems
– sensory neurons from visceral organs to CNS
– motor neurons to smooth & cardiac muscle, glands &
blood vessels
 sympathetic division (speeds up heart rate)
 parasympathetic division (slow down heart rate)
 Enteric nervous system (ENS)
– involuntary sensory & motor neurons control GI tract
– neurons function independently of ANS & CNS

8. HISTOLOGY OF NERVOUS SYSTEM
 White matter consists of:
• aggregations of myelinated nerve
fibers,
• few unmyelinated nerve fibers,
• neuroglia,
• blood vessels.
Gray matter contains:
• neuron cell bodies,
• mostly unmyelinated nerve fibers,
• few myelinated nerve fibers,
• neuroglia,
• blood vessels.

9. In the spinal cord, gray matter forms an H-shaped
inner core that is surrounded by white matter.
In the brain, a thin superficial shell of gray matter
covers the cerebrum.

10.  In the CNS
 Groups of nerve cell bodies are called
nuclei.
 Bundles of nerve fibers are called tracts.
 In the PNS
 Groups of nerve cell bodies are called
ganglia.
 Bundles of nerve fibers form nerves.

11. Spinal Cord
 Is a cylindrical structure that is directly continuous
with the brain & it is situated in the vertebral canal
but not reaching up to its end.
 In cross section it exhibits a butterfly-shaped
grayish inner substance, the gray matter & a
whitish peripheral substance, the white matter.
 Gray matter is divided into the:
 Dorsal (posterior) horns – are fine-bored & long,
 Ventral (anterior) horns – are wide & short,
 Lateral horns.
They are joined to the contralateral gray matter by
the central gray commissure with a central canal that
contains CSF.

12. Dorsal horn
Ventral horn
Anterior median fissure
Posterior median sulcus
Lateral horn
Central
canal

13. Lateral white
column
Anterior
white column
Posterior
white column
White matter
Two groups of tracts:
 propriospinal
 supraspinal:
• accending cerebro-spinal
• descending cerebro-spinal
Propriospinal tracts perform a connection between different parts of the
spinal cord.
Supraspinal tracts perform a connection with a brain.

14. Central canal of spinal cord
Central canal of the spinal cord is lined
with ependymal cells. The cells are often
ciliated and form a simple cuboidal or low
columnar epithelium. The lack of tight junctions
between ependymal cells allows a free exchange
between cerebrospinal fluid and nervous tissue.

15. According to the topography of
neurons’ axons all neurons of spinal
cord are divided into:
 Radicular – axons of neurons form the
anterior roots.
 Inner – axons of neurons are located
inside of the gray matter.
 Fascicular – axons of neurons form
bundles of nerve fibers inside of the white
matter – tracts.

16. Spinal Cord
posterior
funiculus
gray matter
dorsal horn
lateral
funiculus

17. Dorsal horns
 Spongy layer (marginal
zone) – contains many
interneurons
 Gelatinous substance –
mostly is formed by neuroglia
 Nucleus proprius –
interneurons that axons go to
the opposite part of spinal
cord & inside of tracts go to
the cerebellum & thalamus
 Thoracic nucleus (Clark’s
nucleus) - is formed by
interneurons that axons go to
the cerebellum.
Thoracic nucleus

18. Spinal Cord
anterior
funiculus
ventral horn
lateral
funiculus

19. Ventral horns Contain multipolar
motor neurons
 Most evident are:
 Medial group of
motor neurons that
innervate muscles of
the trunk (body)
 Lateral group of
motor neurons that
innervate muscles of
upper & lower
extremities

20. Lateral horns
 Are well developed
in thoracic & sacral
regions
 Contain nuclei that
are formed by
interneurons of
autonomic nervous
system (visceral
organs)

21. Meninges
The meninges cover the spinal cord and
include 3 layers of connective tissue
– dura mater - outer most of the membranes
– arachnoid - middle layer, provides space for
the movement of CSF
– pia mater - inner most layer, includes blood
supply for the spinal cord

22. The Dorsal Root of the spinal nerve contains incoming or afferent fibers carrying
sensory information from the periphery (these are axons of sensitive pseudounipolar
neurons of dorsal root ganglion).
The Ventral Root of the spinal nerve contains outgoing, efferent fibers that carry
information destined to control motor or glandular function. The cell bodies of these
motor neurons are located in the ventral horns of the spinal cord's central grey region
(these are axons of motor multipolar neurons of ventral horns).

23. The ventral root joins with the dorsal root outside the
vertebral column to form a spinal nerve.

24. Ganglia
 Sensory ganglia – contain pseudounipolar
or bipolar afferent neurons. They are
located by course of posterior roots of the
spinal cord (spinal ganglia) & cranial
nerves (V, VII, VIII, IX, X)

25. Within the peripheral nervous system, there are special nerve cell clusters
called dorsal root ganglia that help transmit the sensory messages of pain and
touch. Dorsal root ganglia are also known as spinal ganglia, or posterior root
ganglia.

26. Capsule - dense irregular connective tissue that is continuous with the epineurium of
the nerve.
Ganglion Cells - large, nerve cell bodies with large nuclei and prominent nucleoli.
Satellite Cells - glial cells at the periphery of nerve cell bodies.
Nerve Fibers - unmyelinated and myelinated axons of different diameters.

27. Nerve
 Bundle of axons in the PNS.
 Consists of sensory & motor
nerve processes – it is
called mixed.
 Endoneurium around each
axon - Loose CT.
 Perineurium – CT around a
bundle of axons.
 Epineurium – CT around a
nerve.

28.  A bundle of processes in the PNS is a nerve.
 Within a nerve, each axon is surrounded by an
endoneurium (too small to see on the photomicrograph) –
a layer of loose CT.
• Groups of fibers are
bound together into
bundles (fascicles)
by a perineurium
(red arrow).
• All the fascicles of a
nerve are enclosed
by a epineurium
(black arrow).

30. The path followed by a nerve impulse to produce a reflex action. The
impulse originates in a receptor at the point of stimulation, passes
through an afferent neuron or neurons to a reflex center in the brain or
spinal cord, and from the center out through efferent neurons to the
effector organ, where the response occurs.
The basic conduction pathway through the nervous system, consisting of
a sensory neuron, an association neuron, and a motor neuron.
Reflex arc
A reflex is a rapid,
predictable motor
response to a
stimulus.

31. When a physician strikes your
patellar tendon, the tendon
fibers are stretched and activate
the Golgi tendon organ
(receptor). An action potential
results, and is carried toward
the spinal cord. Within the gray
matter the sensory
neuron synapses with
an interneuron. The interneuron
in turn synapses with motor
neuron, and an action potential
is in turn initiated in the motor
neuron. The motor neuron
carries an action potential to
leg muscles, which contract
and cause your leg to extend.

32. An interneuron may connect two neurons on the
same side of the spinal cord or on opposite side.

33. The conduction pathway through the nervous system may consists
only of a sensory neuron and a motor neuron.

34. The conduction pathway through the nervous system
may consists a sensory neuron, a chain of interneurons
and a motor neuron.

35. Autonomic ganglia
 Paravertebral – along the vertebral column
 Prevertebral – in front of the vertebral
column
 Іntramural – within organs - heart,
bronchi, GIT, urinary bladder.

36. Cells of intramural ganglia
 Efferent neuron with a long axon (Dogel cell type I)
- large in size, contain short dendrites, its long axon is
directed to the organs where it forms motor or
secretory endings.
 Afferent neuron with equal in length cell processes
(Dogel cell type II). Long dendrites and axon form
synapses with the I and III types of cells in the
adjacent ganglia.
 Interneuron (Dogel cell type III) – it is a local
interneuron that connects several cells of I and II
types.

37. Autonomic reflex arc
I type
1-st neuron – afferent pseudounipolar neuron. A
cell body is in the spinal ganglion; dendrite
within spinal nerve goes to the periphery where it
forms a receptor nerve ending; axon goes to the
grey matter of spinal cord within dorsal root.
There it forms a synapse with second neuron.
2-d neuron– interneuron multipolar neuron of the
lateral nucleus of the lateral horn of the grey
mater of the spinal cord. Short dendrites make
branches within the grey matter; axon leaves the
spinal cord and within a preganglionic nerve fiber
goes to an autonomic ganglion. There it forms
synapses with third neuron.
3-d neuron – Dogel cell type I – motor multipolar
neuron. Its short dendrites make synapses within
autonomic ganglion; axon within postganglionic
nerve fiber goes to the internal organs where it
forms an effector nerve ending.

38. Autonomic reflex arc
II type
1-st neuron – afferent pseudounipolar
neuron. A cell body is in the spinal
ganglion; dendrite within a
preganglionic nerve fiber crosses an
autonomic nerve ganglion and within a
postganglionic nerve fiber goes to an
internal organ where it forms a receptor
nerve ending; axon within dorsal root
exits into the grey matter of a spinal cord
where it forms a synapse with a second
neuron.
2-d and 3-d neurons are similar to the
neurons the autonomic reflex arc I type.

39. Autonomic reflex arc
III type
1-st neuron – Dogel cell type II– afferent
multipolar neuron. Cell body is in the
autonomic ganglion, long dendrites
within a postganglionic nerve fiber go out
from the ganglion and form receptor
nerve endings within an internal organs;
long axon within the postganglionic
nerve fiber go to the spinal ganglion and
transiting it goes to the grey matter of the
spinal cord where it form a synapse with
a second neuron.
Efferent part of the arc is identical to
previous types.

40. Beginning of exams…
…At the end of exams