The document summarizes the structure and function of the nervous system. It describes the central nervous system including the brain and spinal cord. It discusses the divisions of the brain and spinal cord. It also describes neurons, synapses, tracts in the spinal cord including ascending sensory and descending motor tracts. The functions of various parts of the brain like hypothalamus, basal ganglia, and cerebellum are summarized. Various neurological disorders are also briefly discussed.

1. NERVOUS SYSTEM
Dr. A. R. Joshi
PROFESSOR OF
PHYSIOLOGY

2. Nervous System
Central Nervous
System
• To control
voluntary and
conscious
functions e.g.
voluntary
movements,
appreciation of
sensations etc.
Autonomic Nervous
System
• To control in-
voluntory functions
e.g. beating of heart,
movements of
intestine etc.

3. Central Nervous System
• Anatomical Division :
Brain & twelve pairs of cranial nerves
Spinal Cord & thirty one pairs of
spinal nerves

4. Brain
• Forebrain - Cerebrum
- Thalamus
- Hypothalamus
• Midbrain
• Hindbrain - Pons
- Medulla
- Cerebellum
(Grey matter outside & white matter
inside)

5. Brain…
• Blood Supply : 700-800
ml/minute by
Circle of Willis.
● Brain is covered by three
meninges.
● Lymph is replaced by CSF, present
in
ventricles of brain &
subarachnoid

6. Spinal Cord
• Parts : - Cervical
- Thoracic
- Lumbar
- Sacral
Gray matter inside with anterior and
posterior roots.
White matter outside with anterior,
lateral and posterior columns.

7. Physiological Division
• Sensory
component
Receptor
Sensory nerve
Ascending tract
Thalamus
Parietal lobe
• Motor Component
Frontal lobe
Descending tract
Anterior horn cell
Motor nerve
Muscle

8. Neuron
• A functional unit of nervous system
• One way conduction in neuron
• Cell body is sensory
• Axon is motor
• Velocity of impulse depends upon
- Myelination
- Diameter

9. Synapse
• Functional junction between two
neurons
•Transmission is via
Neurotransmitter
•Excitatory NTs are Ach, Adr, NA
•Inhibitory NTs are Serotonin,
GABA,
Dopamine, Glycine
•(Inhibition can be presynaptic or

10. Properties of Synapse
1. One way conduction
2. Fatigue
3. Delay
4. Excitation or Inhibition
5. Reciprocal inhibition or cross
extensor reflex
6. Reverberation
7. Irradiation

11. Functions of Spinal cord
1. Reflex action
2. Ascending tracts (Sensory)
3. Descending tracts (Motor)
4. Origin to ANS
5. Inhibitory neurons with different
functions

12. Tracts in Spinal Cord

13. Tracts in Spinal cord

14. Dorsal Column Pathways
• Tract of Gall (Fasciculus Gracilis)
(Carrying fine sensations from lower
extremities & trunk)
• Tract of Burdach (FasciculusCuneatus)
(Carrying fine sensations from upper
extremities & chest)

15. Dorsal Column
Pathways…
Dorsal root ganglion (1st
ordered neuron)
↓
Dorsal column tract in spinal cord on the same
side
↓
Nucleus Gracilis & Cuneatus (2nd
ordered neuron)
(Crossing to opposite side)
↓
Medial lemniscus (Brain Stem)
↓
Thalamus (3rd
ordered neuron)
↓
Parietal lobe (Sensory Cortex)

17. Ascending Tracts (Sensory)
1.Dorsal column tracts (Fine
sensations)
• Fine touch,
• Tactile localization,
• Tactile discrimination
• Vibration sense,
• Sense of stereognosis,
• Joint position, Muscle movement

18. Spinothalamic Pathways
1. Lateral Spinothalamic Tract
(Carrying pain & temp. sensation)
2. Ventral Spinothalamic Tract
(Carrying crude touch & pressure
sensation)

19. Spinothalamic pathways…
Dorsal root ganglion (1st
ordered neuron)
↓
SG cells (2nd
ordered neuron) in spinal cord
↓
(Crossing to opposite side)
↓
Lateral & Ventral Spinothalamic tract
↓
Thalamus (3rd
ordered neuron)
↓
Parietal lobe (Sensory Cortex)

21. 2. Spinothalamic tracts (Crude sensations)
• Crude touch,
• Pressure,
• Temperature,
• Pain
• Itch
• Sexual sensations

22. Damage to Sensory Tracts
1. Damage to Dorsal column tract
Sensory ataxia
Loss of fine sensations
Loss of vibration sense
Astereognosis on
the same side below the level of
lesion
2. Damage to Spinothalamic tract
Crude sensations lost on
opposite side
below the level of lesion

23. Descending Tracts (Motor)
1. Pyramidal tracts:
Cortico-spinal fibers: Control of
voluntary movements especially skilled
movements of distal joints (e.g. writing,
painting) and voluntary control of bladder
and bowel
Corticonuclear fibres: Control of
facial
movements, eye-ball movements,
mastication and speech.

24. Pyramidal tracts (Cortico-
spinal)
Motor cortex (Broadman's area 4,6 and
8)
↓
Corona radiata
↓
Internal capsule (Common site of
damage)
↓
Crus of Mid brain
↓
Pyramids of Medulla - Crossing on opposite

26. Hemiplegia
•Common site of damage- Internal
capsule (damage to Charcot’s artery)
•Paralysis on opposite side
•Three stages seen
•Second stage-typical UMN type of
paralysis
•Aphasia may be associated
•Supra-nuclear facial nerve palsy

27. Extra-pyramidal Tracts
1. Reticulo-spinal tracts
2. Vestibulo-spinal tracts
3. Rubro-spinal tract
4. Tecto-spinal tract
5. Olivo-spinal tract

28. Descending Tracts
(Motor…)
Extra-pyramidal tracts:
(Sub cortical origin )
● Control of gross postural
movements
of proximal joints like pelvic
girdle &
shoulder girdle movements
● Control of anti-gravity muscles of
lower extremities
● Regulation of muscle tone.

29. Paraplegia
• Paralysis of both lower
extremities
• Most of the cases are spastic
• Three stages are seen
• It is UMN type of lesion
• Features of complete &
incomplete
transection may differ.

30. UMN & LMN concept
• UMN : 1st
Neuron in motor pathway
terminating on LMN
e.g.: Pyramidal & extrapyramidal tract
neurons
• LMN : Last neuron in motor pathway
directly supplying muscle
e.g. Anterior horn cells & cranial nerve
nuclei

31. UMN Lesion (features)
1. Rigidity or spasticity
2. Hypertonia
3. Deep reflexes are exaggerated
4. No atrophy
5. Positive Babinski’s sign
e.g. Hemiplegia or Paraplegia

32. LMN Lesion (features)
1. Flaccidity
2. Hypotonia
3. All reflexes lost
4. Atrophy seen
5. No Babinski’s sign
eg.Poliomyelitis

33. Spinal cord lesions
Causes:
• Traumatic e.g. fracture of vertebrae
• Infective e.g. tuberculosis
• Degenerative e.g. motor neuron
disease
• Vascular e.g. atherosclerosis
• Neoplastic e.g. meningioma

34. Spinal cord lesions
(classification)
1.Lesions of roots:
Anterior or posterior root lesions
2.Lesions of cord proper:
(a) Complete trans-section
(b) Incomplete trans-section including
Hemi-section
(Brown Sequard syndrome)

35. Spinal cord Lesions (Stages)
1. Stage of Spinal Shock
For 2-3 wks. Picture like LMN lesion
2. Stage of Reflex Activity
Can remain life long Picture like UMN
lesion
3. Stage of Reflex Failure
Complications causing irreversible
damage Picture like LMN lesion

36. Complete transection
1. Paraplegia in Flexion
2. Flexor reflexes return first
3. Mass reflex present
Incomplete transection
1. Paraplegia in Extension
2. Extensor reflexes return first
3. Mass reflex absent

37. Principles of Treatment
1. Treat the basic Cause
2. Maintain the Vital functions
3. Take care of
• Nutrition
• Bladder
• Bowel
• Bed sores
4. Start Physiotherapy as early as possible

40. Functions of Cerebral
Cortex
Frontal lobe( Motor Functions)
1. Control of Voluntary movements
2. Control of Speech and writing
Prefrontal lobe ( Intellectual Functions)
1. Memory and intelligence
2. Thinking and solving of problems
3. Prediction and future planning

41. Parietal lobe ( Sensory functions)
1. Appreciation of fine sensations
2. Stereognosis, barognosis
3. Appreciation of taste sensation
Temporal lobe ( Auditory functions)
1. Appreciation of hearing
2. Behavioral functions like fear and
rage
Occipital lobe (Visual functions)
Appreciation of vision including colors

42. Functions of Hypothalamus
1. Endocrine control on Pituitary gland
2. Regulation of
•Food intake
•Thirst
•Body temperature
•Sex behavior
•Circadian rhythms
•ANS

43. Sleep & wakefulness
• Temporary state of unconciousness
• Neuronal fatigue of ARAS
• REM & NREM patterns
• Essential for life
• Drugs can modify

44. REM Sleep NREM
Sleep
1. Person wakes up in 1. Person goes
to sleep this pattern in this pattern
2. Duration less 2. Duration more
3. Eyeballs move 3. No movement
4. Dreams occur 4. Do not occur
5. Difficult to arouse 5. Easy to arouse
6. EEG –Beta pattern 6. EEG –Delta

45. Functions of Basal Ganglia
1. Regulation of muscle tone
2. Inhibition of motor cortex
3. Timing and scaling of movements
4. Involuntary associative
movements
5. Regulation of gross intentional acts

46. Parkinsonism
Deficiency of Dopamine at Corpus
Striatum due to damage to Nigro-strial
tract
Features: 1.Akinesia
2. Rigidity
3. Pill rolling tremors
4.Jerky gait
5. Mask face

47. Treatment of Parkinsonism
1. Treat the basic cause
2. L-dopa and carbi-dopa group of drugs
3. Anticholinergic drugs
4. Stop Phenothiasines
5. Other drugs like Amantadin,
Bromocriptin
6. Transplantation of Adrenal medulla

48. Functions of Cerebellum
1. Co-ordination of Voluntary movements
2. Timing, planning and scaling of
movements
3. Regulation of Muscle tone
4. Regulation of Posture and Equilibrium
5. Regulation of Conjugate eyeball
movements
6. Inhibition of Motor cortex

49. Cerebellar Signs
1. Nystagmus
2. Dysmetria
3. Dysdiadochokinesis
4. Motor ataxia
5. Drunken-man’s gait
6. Pendular knee jerk

50. Abnormal Gaits
1. Circumduction gait in Hemiplegia
2. Spastic gait in Paraplegia
3. Flaccid gait in Poliomyelitis
4. Drunken-man’s gait in Cerebellar
syndrome
5. Jerky gait in Parkinsonism
6. High steppage gait in Dorsal column
damage