Neuro Anatomy Introduction, Nervous System, Classification of Nervous System, Cellular Architecture, Neuron Structure, Classification of Neuron, Skull: Osteology, Bones of skull, Skull Joints, Anatomical Position of Skull, Methods of Study of skull.

1. Neuro Anatomy
Dr. Priyanka(PT)
BPT,MPT(Neurological Disorders)
Assistant Professor(SIMS College,
Dehradun)

2. What is Neuroanatomy?
Study of structure and organization of Nervous
system.

3. Nervous System
It is the most complex system of the body.
Chief controlling and coordinating system of the body.
It is responsible for judgment, intelligence, and memory.
It regulates both voluntary and involuntary activities.
The average weight of the adult brain in the air is 1500 grams.
The brain weighs 50 grams as it floats in cerebrospinal fluid.
180-200 billion neurons are present in an adult.

4. Divisions of the Nervous System
Anatomical
1. Central Nervous System(CNS)
It comprises of brain and spinal cord.
It is responsible for integrating, coordinating the sensory information
and ordering appropriate motor actions.
It is the seat of learning, memory, intelligence and emotions.
2. Peripheral Nervous System(PNS)
It includes 12 pairs of cranial nerves and 31 pairs of spinal nerves.
Afferent impulses:- PNS provide afferent impulses to CNS.
Efferent impulses:- PNS carries efferent impulses to muscles, glands and
blood vessels.

5. Functional
Peripheral nervous system functionally has two components.
1. Afferent
Provides sensory information to CNS.
2. Efferent
 Carries motor information to muscles, glands, blood vessels
and heart via:
a. Somatic Nervous System:- Control of skeletal muscles.
b. Autonomic Nervous System:- Control of heart, smooth muscle
of the organs, glands and blood vessels.
It is subdivided into Sympathetic and Parasympathetic parts.

6. Cellular Architecture
Two types of cells are present in the nervous tissue of the Nervous system.
1. Neurons
Known as the nerve cells of the brain.
It is the nerve cells that send and receive signals from the brain.
Each neuron is specialized for sensitivity and conductivity.
Impulses flow from these neurons with great rapidity.
2. Neuroglia
Also known as the neuroglial cells.
It forms the supporting(connective)tissue of the CNS. Thus known as
supporting cells of the brain.
Neuroglial cells are replaced by Schwann’s cells in the PNS.

7. Neuron Structure
The neuron is made up of the following components.
1. Cell body
The cell body is the central region which is the most important part of the
neuron containing the nucleus of the cell.
They form grey matter and the nuclei in the CNS.
They form ganglia in the PNS.
2. Cell Processes of two varieties.
a. Dendrites ( Branch of tree)
Dendrites are the extensions that carry impulses toward the cell body and
are referred to as being afferent fibers.
They effectively increase the surface area of a neuron to increase its ability
to communicate with other neurons.

8. b. Axons
Single elongated process.
Collectively axons form
tracts(white matter) in the
CNS and nerves in the PNS.

10. Classification of Neuron
I. Based on number of poles

11. Anaxonic or Non-polar neurons
 No anatomical clues to determine axons from
dendrites
 Functions unknown.
 These type of neuron bears several branched
processes. There are no functional differences
between the axon and dendrite.
 Each processes can bring impulse to the cyton or
can take away from the cyton.
 These neurons are rare in vertebrates but common
in cnidarians such as Hydra.

12. Unipolar neuron:
 Single process coming off cell body, giving rise to
dendrites (at one end) & axon (making up rest of process)
 Present only in embryonic life.
 A unipolar neuron only has one nerve process extending
from the cell body: an axon that extends into dendrites.
 Unipolar neurons only occur in invertebrates, such as
flies, and are not present in humans.
 In invertebrates, unipolar neurons play a role in the glands
and muscles.
 Present in the mesencephalic nucleus of the trigeminal
nerve .

14. Pseudounipolar Neuron
Single short process that branch like a T
to form a pair of longer processes.
It is actually unipolar, to begin with, but
becomes bipolar functionally.
It is found in the dorsal nerve root
ganglia and sensory ganglia of the
cranial nerves.
 Ex: Sensory neurons

15. Bipolar Neurons
 Two processes coming off cell
body – one dendrite and one axon.
Dendrite is specialized to receive
specific stimulus
Axon conduct action potential to
CNS
Ex: Retina of eye, Nasal cavity

16. Multipolar Neuron
• Multiple dendrites and single axon.
• Most common type of neuron within
CNS.
• Most of the neurons in man are
multipolar, e.g all motor and
internuncial neurons

18. II. Based on Length of Axon.
1) Golgi Type- I Neuron
• Long axons and numerous short dendrites.
• Cell bodies are located in different parts of the CNS and their axons
reach the peripheral organs.
• Present in Pyramidal cells of the cerebral cortex, Purkinje cells of the
cerebellum, and anterior horn cells of the spinal cord.
2) Golgi Type-II Neuron:
• Short axons.
• Establish synapses with neighboring neurons.
• Present in the cerebral cortex and spinal cord.

19. III. Based on the Function
1. Sensory neurons
Transmit sensory information from receptors of PNS towards the CNS.
Most sensory neurons are unipolar, and a few are bipolar.
Sensory neurons are of three types.
1. Primary or 1st order sensory neurons.
Present as spinal or sensory neurons in the dorsal root ganglion of spinal
nerves.
2. Secondary or 2nd order sensory neurons.
Present in the grey matter of spinal cord and in brainstem.
3. Tertiary or 3rd order sensory neurons.
Present in the thalamus.

21. 2. Motor Neurons
Motor neurons carry impulses from the CNS to the distal part of the body.
Motor neurons are of two types.
1. Upper motor neurons.
Situated in the motor area of the brain.
These synapse with cranial nerve nuclei and the anterior horn of the
spinal cord.
2. Lower motor neurons.
Located in cranial nerve nuclei and the anterior horn of the spinal cord.
Nerves emerging from these nuclei supply the skeletal muscles.

22. IV. According to Shape
Stellate.
Basket.
Fusiform.
Pyramidal.
V. According to size.
Macroneuron
Microneuron.

23. Osteology: Skull
The skeleton of the head is called the skull.
Several bones of the head join together to form the cranium.
The two terms skull and cranium, are used synonymously.
The skull can be divided into two main parts:
(a)The calvaria or brain box is the upper part of the cranium which encloses the brain,
(b) the facial skeleton constitutes the rest of the skull and includes the mandible.

24. Bones of the Skull
1. Consists of 22 bones.
2. Calvaria or brain box:- Comprised of 8 bones.
Paired:- Parietal, Temporal.
Unpaired:- Frontal, Occipital, Sphenoid, Ethmoid.
3. Facial Skeleton:- Comprises of 14 bones.
Paired:- Unpaired
a. Maxilla a. Mandible
b. Zygomatic b. Vomer
c. Nasal
d. Lacrimal
e. Palatine
f. Inferior nasal concha.

29. Skull Joints
Sutures
The sutures of the skull, also referred to as the cranial sutures, are fibrous
joints that connect the bones of the skull.
Skull joints are immovable fibrous joints.
Only a few are cartilaginous joints.
During infancy, slight movement is available in the sutures.
As one age, these sutures become immovable.

31. Anatomical Position of the Skull
Frankfurt Plane
The anatomical position of the skull is the Frankfurt plane.
 In this position, the lower margins of the orbitals (eye sockets), the
lower margin of the orbits, and the upper margins of the ear canals
(poria) lie in the same horizontal plane.
This orientation represents the position of the skull if the subject were
standing upright and looking straight ahead.

32. Reid’s baseline
 The horizontal line is obtained by joining the infraorbital margin to the center of the external
acoustic meatus, i.e. auricular point.
 It is used by the radiologist.
Frankfurt Plane
 The horizontal line is obtained by joining the infraorbital margin to the upper margin of the
external acoustic meatus.

35. Methods of Study of the Skull
1. External study.
1. Superior view or norma verticalis.
2. Posterior view or norma occipitalis.
3. Anterior view or norma frontalis.
4. Lateral view or norma lateralis.
5. Inferior view or norma basalis.
2. Internal Study:- studied from the inside or internally after removing the roof of the calvaria or
skull cap.
1. Internal surface of the cranial vault.
2. Internal surface of the cranial base which shows a natural subdivision into anterior, middle, and posterior
cranial fossae.
3. The skull can also be studied as an individual bones.

36. Thank You