1. Introduction to the
Nervous System
Prof. Vajira Weerasinghe
Professor in Neurophysiology
Faculty of Medicine
University of Peradeniya
(This lecture is available at www.slideshare.net/vajira54)

3. Why study nervous system?
Neurological diseases are disabling
and debilitating and very little treatment
is available

4. Migraine
(severe headache)
Stroke or paralysis Parkinsonism
Alzheimer’s disease (Memory loss)
Muscle wasting

5. Why study nervous system?
Activities such as walking and running and
various forms of exercise and sports require
proper functioning of the nervous system

7. Controlling system
Nervous system is the main
controlling system of the body
Quick
Electrical
Endocrine system also
controls body functions
Slow
Chemical

8. Nerve impulses
• It controls other organs by sending electrical
messages called nerve impulses
It is also the main communication system (like

9. What does it do ?
Functions of the nervous system
1. Receives sensory messages from the external environment
2. Organizes information and integrates it with already stored
information
3. Uses integrated information to send out messages to muscles
and glands, producing organized movement and secretions
4. Provides the basis for conscious experience

10. Functional Subdivisions
• Sensory functions
 feeling, eg. pain
• Autonomic functions
control of blood pressure
• Integrative functions
eg. reflexes
• Motor functions
movement, eg. walking
• Higher functions
memory, learning

11. Anatomical Subdivisions
• Central Nervous system
Brain and spinal cord
• Peripheral Nervous system
Cranial Nerves & Peripheral Nerves
• Autonomic system
sympathetic & parasympathetic

12. Brain - Lobes
• Brain contains the main controlling
centres
• Frontal lobe
Located in the front
Performs motor functions
• Parietal lobe
Located laterally
Performs main sensory functions

13. Brain - Lobes
• Occipital lobe
Located in the back
Performs visual functions
• Temporal lobe
Located laterally
Performs hearing functions

14. Spinal cord
• Functions
To transmit impulses to and from the
brain to the periphery
To cause reflex action
To process information

15. Peripheral nervous system
• Cranial nerves
There are 12 cranial nerves which
connects brain & brainstem with
different organs of the head and neck
region
• Spinal nerves
There are several pairs connecting
different segments of the spinal cord
with peripheral organs

16. Cranial nerves
I-Olfactory nerve - smell
II-Optic nerve - vision
III-Occulomotor nerve - eye movements
IV-Trochlear nerve - eye movements
V-Trigeminal nerve - mastication
VI-Abducens nerve - eye movements
VII-Facial nerve - facial expressions
VIII-Vestibulocochlear nerve - hearing, balance
IX-Glossopharyngeal nerve - taste
X-Vagus nerve - parasympathetic
XI- Spinal accessory nerve - neck muscles
XII-Hypoglossal nerve - tongue

17. • Spinal nerves
Cervical
Thoracic
Lumbar
Sacral

18. Brain stem
• This is an important part of the
nervous system that connects
brain with the spinal cord
• Many cranial nerves arise from
brain stem
• It also contain vital centres
Cardiac, respiratory functions,
consciousness

19. Brain stem
• It has three areas
Midbrain
Pons
(or pons Varoli)
Medulla
(or medulla oblongata)

20. Cerebellum
• This is hind brain
• This is connected to the
brainstem
• Main function is motor
coordination
• Abnormalities result in difficulty

21. Sensory functions
• Functions that make us feel the
environment
• Nerve signals come from the
sensory organ towards the CNS
Afferent signals
• There are different types of
sensory modalities human nervous
system could feel

22. General and special sensations
• There are two main types of sensations
General sensations
Special sensations

23. General sensations
• Mechanical sensations
Touch
Pressure
Vibrations
Stretch
• Thermal sensations
Hot, cold
• Chemical sensation

24. Somatic and visceral sensations
• Somatic sensations
External stimuli sensed by the skin
eg. Feeling of hot environment
• Visceral sensations
Internal sensations sensed by the
visceral afferent nerves
eg. acidity in stomach

25. Special sensations
These are specialised sensations
Vision
Hearing
Taste
Smell

26. Proprioception
• Joint and position sensation
• Muscles and tendons contain
receptors which could feel
Muscle length
Joint angle
Position of bones and joint
• This is very important feedback
information for movements of
muscles

27. Motor functions
• Movements are of two
types
Voluntary movements
Consciously controlled
movements
Well thought and planned
Involuntary movements
Reflex action
Control of posture
Balance

28. Voluntary movements
• Planning starts from the brain (frontal
lobe)
• Modified by various intermediate
structures
Brainstem
Cerebellum
• Executed by the brainstem and spinal
cord (lower motor neuron)

29. Reflexes
• Response to a stimulus
• This is an involuntary action
eg. Hot object touching the hand
will cause it to withdraw
• This is called withdrawal reflex

30. What is a reflex?
Stimulus
Effector organ
Response
Central
connections
Efferent nerve
Afferent nerveReceptor
Central control

31. Reflexes
• Reflexes involve many systems of the body
• eg.
Withdrawal reflex (pain and motor pathways)
Pupillary reflex (eye)
Salivatory reflex (salivary glands)
Swallowing reflex (GIT)
Micturition reflex (urinary system)
Baroreceptor reflex (blood pressure control)
Stretch reflex (main reflex in the motor system)

32. Autonomic functions
• Controls involuntary functions of
the body
• Two main divisions
Sympathetic
Parasympathetic

33. Sympathetic system
• This is involved in fight or flight
reaction
• What happens when somebody is
excited
Blood pressure increases
Heart rate increases
Respiratory rate increases
Increased sweating
Pupillary dilatation
GIT function suppressed

34. Parasympathetic system
• This is involved when somebody s
resting
• Blood pressure decreases
• Heart rate decreases
• Respiratory rate decreases
• Decreased sweating
• Pupillary constriction
• GIT function increased

35. Higher functions
• Brain is involved in controlling
higher functions
• Learning
• Memory
• Intelligence
• They are called cognitive functions

36. Basic cell in the nervous system is
is a neuron
Nerve signals are electrochemical impulses
called “action potentials”