This document discusses the anatomy and physiology of the nervous system. It covers several topics: 1) The nervous system requires adequate space around neural tissue and attachments to surrounding structures. The space is less in males than females and developmental stenosis is more common in males. 2) The dura mater has various attachments inside and outside the cranium and spinal canal. Dural ligaments attach the dura to surrounding structures like bones. 3) The blood supply to the nervous system is critical. The spinal cord receives blood from various arteries but is most vulnerable between T4-T9 where the supply is least rich. Peripheral nerves also have extensive intrinsic blood flow. 4) Axonal transport systems move materials and

1. FUNCTIONAL ANATOMY AND
PHYSIOLOGY OF THE
NERVOUS SYSTEM
BY
AHMED SHAWKY ALI
UNDERSUPERVISIONOF
PROF. DR. HUSSEIN SHAKER

2. NERVOUS SYSTEM RELATIONS SPACES AND
ATTACHMENTS
Adequate space is needed around the neural and
connective tissue and there must be enough space
at rest and during physiological movements of the
spine. The nervous system is attached to
surrounding tissues and structures.
Attachments need consideration in terms of those
attaching neural tissue into connective tissue, such
as the denticulate ligaments, and those attaching
connective tissue (and thus the neural tissue) onto
other structures, such as the dural ligaments.

3. NERVOUS SYSTEM RELATIONS SPACES AND
ATTACHMENTS
 N.B Haset al (1983) have shown that the space
around neural tissue, both in the spinal canal and
the intervertebral foramen, is less in males than in
females.
 These authors also point out that developmental
and degenerative stenosis is more common in the
male.

4. The external connections of the dura
Inside the cranium, the dura mater is loosely adhered
to the central portions of the cranial bones and tightly
adhered at the suture levels (Murzin & Gonunov 1979).
 There is a firm attachment at the foramen magnum
and, at the caudal end, to the coccyx by the external
filum terminale. A network of dural ligaments
(Hoffman ligaments) attaches the anterior theca to the
anterior and and anterolateral aspect of the spinal canal
.
 (Blikiia ,1969) noted that the dural ligaments around
L4 were stronger and more numerous than elsewhere
— so strong that they could not be displaced with a
probe.

5. The external connections of the dura
 Thoracic dural ligaments tend to be filmier and
longer, In the cervical spine, they are shorter and
thicker (Romanes 1981).
 The studies of Tencer et al (1985) have revealed
that, in the lumbar spine, dural ligaments, nerve
roots and trunks are of equal importance in the
distribution of forces.

6. Internal dural attachments
 Inside the dural sac there are 21 pairs of denticulate
ligaments .These run from the pia mater to the dura
and are orientated to keep the cord central in the
dural theca. N.B Tani et al (1987) have shown that
the denticulate ligaments, as well as the filum
terminale, prevent excessive elongation of the cord
during flexion. Thickened denticulate ligaments
associated with cervical spondylosis have been
implicated in cord degeneration (Bedf ord et al
1952).

7. Denticulate
ligaments

8. Attachments of the peripheral nervous system
 The peripheral nerves are also attached to
surrounding tissue. However, they are allowed
movement in their nerve beds, less in some areas
than in others, such as where blood vessels enter or
where nerves branch.

9. Attachments of the peripheral nervous system
 What is unmistakable is that, along the course of a
peripheral nerve, there are some areas where the
nerve is more attached than others, for example, the
common peroneal nerve at the head of the fibula,
and the radial nerve to the head of the radius.
 Yet in other areas, a remarkble amount of
movement of over 1.5 cm occurs (McLelJan &
Swash 1976)

10. THE BASIS OF SYMPTOMS
Knowledge of three processes important to
understanding of symptom reproduction related to
the nervous System:
• The supply of blood to the nervous system .
• The axonal transport systems .
• The Innervation of the Connective tissues of the
nervous system .
All of these processes will be influenced by
mechanical deformation .

11. CIRCULATION
 The nervous system consumes 20% of the available
oxygen in the circulating blood yet consists of 2% of
body mass (Dommjsse 1986). Among cells, neurones
are especially sensitive to alterations in blood flow.
 Importance of blood supply :
An uninterrupted vascular supply is imperative for the
metabolic demands of normal neural function. Blood
supplies the necessary energy for impulse conduction
and also for the intracellular movement of the
Cytoplasm of the neurone.

12. CIRCULATION
 There are extrinsic vessels supplying feeder arteries
to the nerve. Once inside the nervous system , there
is a ‘well dcveloped intrinsic system.
 In many parts of the body, blood supply is so
assured that if some feeder vessels are
compromised the intrinsic system can provide
enough blood for normal neural function. With
such an assured supply, it may seem that the
nervous system Can be relatively independent of its
blood supply.

13. Vasculature of the spinal canal and neuraxis
 These structures have a multiple supply :
1-The vertbral artery,
2- The deep cervical,
3- The posterior intercostal and the lumbar arteries supply
the vertbral column.
They also supply, via segmental subdivisions, the spinal
canal and contents.
At certain vertebral levels, medullary feeder branches
arise and join the longitudinally running anterior and
two small posterior spinal arteries.

14. Vasculature of the spinal canal and neuraxis
 The anterior spinal artery supplies about 75% of the
cord. There are usually around eight medullary feeder
arteries (a branch of the cervical part of the vertebral
artry).
 These arteries are more common in the lumbar and
cervical spines.
 Most of the arteries enter the cord in the low cervical
spine and the lumbar spine.
 During spinal movements these plexus areas have
limited movement in relation to the spinal canal (Louis
1981)

15. Vasculature of the spinal canal and neuraxis
 When the cord is elongated the vessels running
longitudinally are stretched while those running
transversely are folded. The opposite effect occurs
on shortening of the cord (Fig. 1.)

17. Vasculature of the spinal canal and neuraxis
 The veins in the spinal canal are valveless and
under little pressure (Penn ing & Wilrnink 1981).
 This allows flow reversibility and an
accommodating mechanism to sudden in-rushes of
blood, as may occur from coughing and straining.

18. Vasculature of the spinal canal
and neuraxis
 Together with the CSF pressure, via the alterations
in the venous system, a balance of intraspinal canal
pressure is maintained.
 N.B A critical vascular zone exists from the T4 to
T9 vertebral levels. The spinal canal is at its
narrowest and the blood supply is less rich in this
area (Dommisse 1974). This may be relevant in
syndromes such as the ‘T4 syndrome’ .

19. Vasculature of the peripheral nervous system
 The extrinsic supply of the peripheral nerves is
such that it allows leeway for movement; that is,
there is slack in the feeder vessels so that a nerve
can glide without alteration in the blood supply.
 In general, major feeder vessels enter nerves at
areas where there is minimal or no nerve movement
in relation to surrounding tissue.

20. Vasculature of the peripheral nervous system
 Examples of this are at the elbow for the median
and radial nerves. However, if part of the extrinsic
supply is occluded, the intrinsic supply is also
sufficient for the needs of the nerve fibres
(Lundborg 1970, 1975).

21. Vasculature of the peripheral nervous system
 The intrinsic vascular system is extensive, linking
endoneuriurn, perineurium and epineurium.
 Under normal conditions, only part of the intranural
vascular system is used.
 However, if traumatised, many more vessels come
into use (Lundborg 1970). Intraneural blood flow is
reversible and collateral systems exist.

22. Vasculature of the peripheral nervous system
 Intranural blood vessels are sympathetically
innervated (Hromada 1963, Lundborg 1970,
Appenzeller ci al 1984).
 According to Appenzejler et al (1984), the nerve
supply to particular blood vessel arises from the
nerve trunk that: the blood vessel supplies. This
probably allows an adjustable blood supply for
functional demands on the nerve.

23. Vasculature of the peripheral nervous system
 N.B Stretch and compression will surely affect the
circulation, although, the mechanisms are not fully
understood.
 Strech will lessen the diameter of the longitudinally
running vessels, plus raise intrafascicular pressure
and perhaps result in squeezing closed the vessels
crossing the perineurium.

24. Vasculature of the peripheral nervous system
 N.B Arrest of blood flow will begin at
approximately 8% elongation (rabbit sciatic tract)
and complete arrest will occur at approximately
15% elongation (Lundborg & Rydevik 1973, Ogata
& Naito 1986).

25. The blood nerve-barriers
 A slightly positive pressure exists in the
intrafascicular environment. This tissue pressure is
referred to as the endoneurial fluid pressure (EFP)
and is probably maintained by the elasticity of the
perineurium.
 The barrier function is bi-directional. As well as
protection from the exterior, this mechanism means
that if the intrafascicular pressure increases, such as
from an oedematous reaction (Lundborg & Rydcvik
1973), the barrier may close.

26. The blood nerve-barriers
 A good example of the protective function of the
diffusion barrier is where peripheral nerves travel
through infected areas without nerve conduction
being altered .The perineurial barrier is also
resistant to trauma.

27. AXONAL TRANSPORT SYSTEMS
 Within the cytoplasm of all Cells there is
movcment of materials and substances.
 The cytoplasm of the neurone (axoplasm) is no
different.
 However , due to the length of the axon and its
function, speciaized intracellular movement
mechanisms occur.

28. AXONAL TRANSPORT SYSTEMS
 The volume of material in an axon and teminals
may be thousands of times as great as in the cell
body (Lundborg 1988).
 Mammalian axoplasm is quite viscous, about five
times that of water (Haak er al 1976).
 Of necessity, the intracellular transport
mechanisms arc complex. These mechanisms are
referred to as axonal transport systems and are a
major direction for research in present day
neurological science.

29. AXONAL TRANSPORT SYSTEMS
 The axon contains smooth endoplasimic reticulum,
ribosomes, microtubules and neurofilaments
comprised of actin like material — all structures
likely to be part of the axoplasmic transport
mechanisms.
 N.B Human movement plays a role in this
intracellular motility.

30. AXONAL TRANSPORT SYSTEMS
 Within the axon, the flow of substances is constant
and controlled.
 From the cell body to the target tissues (antegrade
flow) there is a fast and a slow transport system.
 From the target tissues to the cell body there is a
(retrograde flow) of axoplasm (Fig. 1.28).
 This bi-directional flow is evident because a nerve
will swell both distally and proximally from
circumferential pressure (Mackinnon & Dellon
1988).

31. D deridrite, N nucleus, M mitochondria, SC synaptic cleft, TT targcc
tissue
Axoplasmic transport

32. AXONAL TRANSPORT SYSTEMS
 Antegrade transport
Materials produced in the cell body are transported
along the axon at various velocities.
Two groups based on the speed of transport, can be
identified.
(A) The fast transport moves at approximately 400
mm per day and the substances carried such as
neurotransmitters and transmitter vesicles, are for
use in transmission of impulses at the synapse
(Droz et al 1975).

33. AXONAL TRANSPORT SYSTEMS
 This transport depends on an uninterrupted supply
of energy from the blood. Various toxic substances
and deprivation of blood will slow or block the
transport (Ochs 1974).

34. AXONAL TRANSPORT SYSTEMS
 (B) In the slow antegrade transport (1—6 mm per
day), cytoskeletal material such as microtubules
and neurofilaments are carried (Levine & Willard
1980 McL.ean et al 1983)
 Essentially, the slow transport exists for
maintenance of the structure of the axon.
 The exact mechanisms of transport are unknown.

35. AXONAL TRANSPORT SYSTEMS
 Retrograde transport
Retrograde transport from target tissues to the cell
body moves rapidly (approx 200 mm per day).
The system carries recycled transmitter vesicles and
extracellular materials such as neurite growth
promoting factors from the nerve terminal or from
damaged segments of nerve.

36. AXONAL TRANSPORT SYSTEMS
 N.B It also seems very likely that the retrograde
flow carries "trophic messages" about the status of
the axon, the synapse and the general environment
around the synapse, including the target tissues
(Kristensson & Olsson 1977, Varon & Adler 1980,
Bisby 1982).

37. AXONAL TRANSPORT SYSTEMS
 If the retrograde flow is altered by physical
constriction or from loss of blood flow, nerve cell
body reactions are induced (Ochs 1984, Dahlin &
McLean 1986, Dahlin et al 1987).
 Viruses, such as herpes simplex, can be transported
via the retrograde transport to the cell body
(Kristensson 1982).

38. AXONAL TRANSPORT SYSTEMS
 An understanding of the concepts of axonal
transport is important for physiotherapists
employing mobilisation of the nervous system as a
treatment.
 As Korr has suggested for some years (1978, 1985)
many of the disorders we treat and the responses
from treatment may be related to the axonal
transport systems.

39. AXONAL TRANSPORT SYSTEMS
 Knowledge of these systems is also important in
order to understand the development of symptoms
along the nervous system (ie, double crush,
multiple crush synd romes) and the need to treat
often more than the local area for optimum results.

40. INNERVATION OF THE NERVOUS SYSTEM
 The connective tissues of the nervous system are
innervated.
 They are, thus, able to be a source of symptoms.
 This innervation also means that the Connective
tissues of the nervous system can contribute o
altered sensory input in the same way that muscle,
joint and other tissue can.

41. The meninges
 Dura mater is innervated by segmental, bilateral,
sinuvertebral nerves, first described by Luschka
(1850). (Meningeal Branch Of Spinal Nerves)
 Each sinuvertebral nerve emerges distal to the
dorsal root ganglion, from the union of a somatic
root arising from the ventral rami and an autonomic
root from the grey rami communicate or a
sympathetic ganglion .

43. The meninges
 As well as supply to the dura, branches of the
Sinuvertebral nerve innervate
- The posterior longitudinal ligament,
-Periosteum,
-Blood vessels
And the annulus fibrosis (Edgar & Ghadially 1975,
Bogduk 1983).

45. The meninges
 N.B The innervation density varies depending on
the spinal segment.
 It is richer in the superficial dural layers than in
those deeper.
 Root sleeves at cervical and lumbar levels have a
richer nerve supply than the thoracic root sleeves
(Cuauco et al 1988).

46. The meninges
 N.B All recent authors on the subject agree that the
ventral aspect of the dura mater has a far denser
innervation than the dorsal aspect .
 Towards the midline, the dorsal dura may be
completely insensitive (Groen ct al 1988).

47. The connective tissues of nerve roots
 The ventral nerve root connective tissues receive
their innervation from fibres Originating in the
dorsal root ganglion.
 Connective tissues of the anterior nerve roots are
innervated by fine branches from the sinuvertebral
nerve (Hromada 1963).

48. The peripheral nervous system
 The connective tissues of peripheral nerves, nerve
roots and the autonomic nervous system have an
intrinsic innervation: the ‘nervi nervorum’ from
local axonal branching.
 Free nerve endings have been observed in the
perineurium, epineurium and endoneurium .
 Thomas (1982) believes that the nervi nervorum
must be Considered a source of symptoms in
diabetic neuropathy and in inflammatory
polyneuropathics.

49. The innervation of the connective tissues of peripheral
nerve
The nervi
nervorurm
E epineurium,
BV blood
vessel,
NN nervi
nervorum,
NF nerve fiber
P perineurium,
PVP
perivascular
plexus

50. The peripheral nervous system
 Sunderlarid (1978) considers the pain from local
pressure on a nerve to be due to the nervi
nervorum.
 The innervation of the nervous system cannot be
neglected — it seems very likely that it plays a part
in adverse tension syndromes.


51. The peripheral nervous system
 Perhaps innervation could be regarded as a
protective mechanism for the nervous system,
symptom production being a warning that the
impulse conducting mechanisms may be in danger
from mechanical or chemical compromise.