The document provides an overview of the nervous system including: - The central nervous system (CNS) which includes the brain and spinal cord. - The peripheral nervous system (PNS) which connects the CNS to other parts of the body and includes nerves and ganglia. - The autonomic nervous system which regulates involuntary body functions and has sympathetic and parasympathetic divisions. - Neurons, the basic cellular units of the nervous system, and neuroglia which support neuronal functions. Key parts of neurons and different neuron types are described.

1. MNR MEDICAL COLLEGE
Department- Anatomy
Topic – Introduction to the nervous system-AN7
Associate Professor: Dr Prasad Mergu

2. NERVOUS SYSTEM

5. AN7.1-DESCRIBE GENERAL PLAN OF NERVOUS SYSTEM WITH
COMPONENTS OF CENTRAL,PERIPHERAL & AUTONOMIC NERVOUS
SYSTEMS

6. INTRODUCTION
• Neuroanatomy is the study of the nervous system.
• The human nervous system is the most complex product of biological evolution
• The nervous system is widely investigated and least understood system in the body.
• It along with endocrine system regulates the functions of all other systems of the body.
• Hence nervous system is also called master system of the body.

7. THE FUNCTIONS
• The functions of the nervous system include:
Reception of sensory stimuli from internal and external environments.
 Integration of sensory information.
 Coordination and control of voluntary and involuntary activities of the body.
 Assimilation of experiences, a requisite to memory, learning and intelligence.
 Storage of experiences to establish pattern of responses in future, based on prior
experience.
 Programming of basic instincts.
The basic instincts in humans are survival, eating, drinking, voiding, and sex
(following puberty).

8. DIVISIONS OF NERVOUS SYSTEM
• Anatomically the nervous system is divided into two parts, the central nervous
system and the peripheral nervous system.
• The central nervous system (CNS) consists of brain and spinal cord.
• The brain is located within the cranial cavity and
• The spinal cord within the vertebral canal.
• The CNS is responsible for integrating, processing, and coordinating sensory data,
and giving appropriate motor commands.
• It is also the seat of higher functions such as intelligence, memory, learning, and
emotions.

9. The peripheral nervous system (PNS) includes all the neural tissues
outside the CNS such as;
12 pairs of cranial nerves,
31 pairs of spinal nerves, and
Ganglia associated with cranial and spinal nerves.
The PNS provides sensory information to the CNS and carries its
motor commands to the peripheral tissues and systems.
Unlike the CNS, the PNS is not protected by bone, leaving it exposed
to toxins & mechanical injuries.

10. NERVOUS SYSTEM
CENTRAL NERVOUS SYSTEM (CNS) PERIPERAL NERVOUS SYSTEM (PNS)
BRAIN SPINAL CORD
FORE BRAIN
(Prosencephalon)
MIDBRAIN
(Mesencephalon)
HIND BRAIN
(Rhombencephalon)
Diencephalon Telencephalon
i. Thalamus
ii. Metathalamus
iii. Subthalamus
iv. Epithalamus
v. Caudal part of the
hypothalamus
1) Cerebral hemispheres
2) Basal ganglia/nuclei
3) Limbic system
Metencephalon
1) Pons
2) Cerebellum
Myelencephalon
1) Medulla oblongata
12 Pairs -CRANIAL
NERVES
31 Pairs -
SPINAL
NERVES
Ganglion

13. SENSORY GANGLION AUTONAMIC/MOTOR
GANGLI ON
SYMPATHETIC PARA-SYMPATHETIC
EX: Dorsal root of each spinal nerve
Trunks of V, VII, VIII, IX, X
EX: Sympathetic trunk
Coeliac plexus
Mesentric plexus
EX: CILIARY
OTIC
SUBMANDIBULAR
PTERYGOPALATINE

14. CRANIAL NERVES
Marieb 13.5a

17. SPINAL NERVES
Marieb 13.6

18. • The afferent division brings sensory information to the CNS.
• The efferent division carries motor commands to the muscles and glands.
• The efferent division has somatic and visceral components constituting somatic and
autonomic nervous systems, respectively.
• – The somatic nervous system (SNS) provides the voluntary control over the skeletal
muscle contraction.
• – The autonomic nervous system (ANS) innervates involuntary structures, such as
heart, smooth muscle and glands and thus provides an involuntary regulation of
smooth muscle, cardiac muscle, and glandular activity.
• N.B. The afferent division brings sensory information to the CNS.
• The CNS interprets the sensory information and sends commands through the
efferent division to produce a response.
Functional

19. AUTONAMIC
SOMATIC ENTERIC
NERVOUS SYSTEM (FUNCTIONAL)
MOTOR
SENSORY
PARA SYMPATHETIC
(Cranio-Sacral Outflow)
(III, VII, IX,X & S2,3,4)
SYMPATHETIC (T1- L2/3)
(Thoraco-lumbar outflow)

20. SOMATIC
MOTOR
SENSORY
General Exteroceptive- Pain, Temperature, Touch
Special Exteroceptive- Vison , Hearing
General Proprioceptive- Muscle and Bone, Joints of
head & Neck, body wall ,
Extremities
Special Proprioceptive - Vestibular receptors for
Balancing
General Somatic Efferent-
Muscles developed from somite's
Special Somatic Efferent- Muscles
of Head & Neck developed from
Branchial arches
Somatic- Motor
(Efferent)
Somatic- sensory
(Afferents)

21. Autonomic
MOTOR
SENSORY
 General visceral afferents- (Hunger, Thirst,
Nausea)
 Special visceral afferents- Smell, Taste
 Sensations for normal visceral reflexes- Carotid
sinus, Hering-breuer reflex)
 Visceral pain sensation-
Pre-ganglionic
Post-ganglionic- Smooth
muscle, Cardiac Muscle,
Glands
Motor
(Efferent)
Visceral- sensory
(Afferents)

23. Freeman 45-20

24. Martini 16-10

25. AN7.2- LIST COMPONENTS OF NERVOUS TISSUE AND THEIR
FUNCTIONS

26. CELLULAR ORGANIZATION OF THE NERVOUS
SYSTEM
• The highly specialized and complex nervous system consists of only two principal
categories of cells, (a) neurons, and (b) neuroglia.
• • Neurons form the basic structural and functional units of the nervous system.
• They are excitable cells which are specialized for reception of stimuli and the
conduction of nerve impulses.
• • Neuroglia or glial cells are supportive cells that support the neurons both structurally
and functionally.
• The neu-roglia are five times more abundant than the neurons and account for more
than half of the weight of the brain.

27. AN7.3- DESCRIBE PARTS OF A NEURON AND CLASSIFY THEM
BASED ON NUMBER OF NEURITES, SIZE & FUNCTION

28. NEURON
STRUCTURE SIZE / LENGTH FUNCTIONAL
UNIPOLAR BIPOLAR MULTIPOLAR
GOLGI TYPE-I GOLGI TYPE-II
PRIMARY SECONDARY TERTIARY
SENSORY INTERNEURON MOTOR
UPPER MOTOR LOWER MOTOR
PRE GNAGLIANIC POST GNAGLIANIC

29. Types of Neurons

33. NEURONS (NEURO, NERVE)
The neurons are the structural and functional units of the nervous system.
They are specialized for reception, integration, interpretation and onward
transmission of information.
They conduct nerve impulses over long distances at great speeds.
The nervous system consists of vast number (about 1012) of neurons.
Each neuron consists of a cell body (also called soma or perikaryon or nerve cell body)
and its processes called neurites.
The typical neuron has a single long process called axon and many short processes
called dendrites

35. Structure of a typical neuron

38. CNS PNS
NEUROGLIA
OLIGODE
NDROCYTE
ASTROCYTS
SATELLITE
CELLS
SCHWANN-CELLS
EPENDYMAL
CELLS
MICROGLIAL
CELLS
PROTO-
PLASMIC
FIBROUS

39. Marieb 11.3

50. STRUCTURE OF A NERVE
Marieb 13.3b

51. AN7.4 -DESCRIBE STRUCTURE OF A TYPICAL SPINAL NERVE

52. SPINAL NERVE
Marieb 13.7a

55. ORGANIZATION OF THE
CNS
Gray Matter: Contains neuron cell bodies
W
White Matter: Contains cell extensions organized into tracts

56. GRAY MATTER: ORGANIZATION

57. ORGANIZATION OF THE NERVOUS
SYSTEM TO SUPPLY THE THREE
BASIC FUNCTIONS

58. sensory receptor
sensory input
integration
motor input
effector

59. AN7.6 -DESCRIBE CONCEPT OF LOSS OF INNERVATION OF A
MUSCLE WITH ITS APPLIED ANATOMY

61. AN7.7 DESCRIBE VARIOUS TYPE OF SYNAPSE
The point at which the nerve impulse passes from one neuron to another
is called synapse.
It is important to know that at synapse, the contact between the neurons
is by contiguity and not by continuity (neuron theory of Waldeyer, 1891),
and the impulse is transmitted across a synapse by a specific
neurotransmitter.
The synaptic communication is the process by which neurons
communicate among themselves and with the muscles and glands.
Synapse

62. FIG. (A) The structure of a typical synapse as seen under electron microscope.
(B) The synaptic transmission.
The neurotransmitter diffuses from the presynaptic terminal across the synaptic cleft to the receptors
on the

63. CLASSIFICATION OF SYNAPSES
• Depending upon the parts of two neurons forming a synapse, the synapses are
of the following types:
• 1. Axodendritic: synapse between an axon and a dendrite.
• 2. Axosomatic: synapse between an axon and a soma.
• 3. Axoaxonal: synapse between two axons.
• 4. Somatodendritic: synapse between a soma and a dendrite.
• 5. Somatosomatic: synapse between two somas and soma.
• 6. Dendrodendritic: synapse between two dendrites.
• N.B. The most common synapse is between an axon of one neuron and the
soma or dendrite of another neuron (i.e. axosomatic or axodendritic).
• The axodendritic synapse is generally termed typical synapse.

66. AN7.8: DESCRIBE DIFFERENCES BETWEEN SYMPATHETIC AND SPINAL GANGLIA

68. Cells and unipolar neurons of a dorsal root ganglion.

69. Multipolar neurons, surrounding cells, and nerve fibers of a sympathetic ganglion