It explains anatomy and physiology of brain. It includes all the characteristic features of brain from learner point of view.

1. CENTRAL NERVOUS SYSTEM:
BRAIN
Mrs. Mayuri Padhye, Assistant professor,
Department of Pharmacology,
Saraswathi Vidya Bhavan’s College of Pharmacy

2. BRAIN
• There are 4 parts of brain
1.Brain stem
2.Cerebellum
3.Diencephalon
4.Cerebrum

3. BRAIN
• The brain stem is continuous with the
spinal cord & consists of Medulla
Oblongata, Pons & Midbrain
• Posterior to brain stem is the cerebellum

4. BRAIN
• Superior to brain stem is the diencephalon
1.Thalamus
2.Hypothalamus
3.Epithalamus
• Supported on the diencephalon & brain
stem is Cerebrum [largest part]

6. MENINGES
• The brain & SC are completely surrounded
by three layers of tissue, Meninges
• They lie between skull & brain
• Outer : Dura mater
Subdural
space
• Middle: Arachnoid mater
Subarachnoid
space

8. MENINGES
• Dura & Arachnoid mater are separated by
subdural space
• Arachnoid & Pia mater are separated by
subarachnoid space containing
Cerebrospinal fluid [CSF]

9. VENTRICLES OF BRAIN
• 4 irregular shaped cavities or ventricles
containing CSF
1.Right & Left ventricles
2.Third ventricle
3.Fourth ventricle

10. VENTRICLES OF BRAIN
1. Right & Left ventricles
• Lie within cerebral hemispheres
• Separated by thin membrane septum
lucidum

11. VENTRICLES OF BRAIN
2. Third ventricle
• Situated below lateral ventricles between
two parts of the thalamus

12. VENTRICLES OF BRAIN
3. Fourth ventricle
• Diamond-shaped situated below &
behind the third ventricle
• Continuous with the central canal of the
SC

13. CEREBROSPINAL FLUID
• It is clear, colourless liquid
• Continuously circulates through cavities
in the brain & SC
• Ventricles are filled with CSF

14. FORMATION: CEREBROSPINAL
FLUID
• SITE: Choroid plexuses i.e. network of
blood capillaries in the walls of the
ventricles
• Capillaries are covered by ependymal
cells that form CSF from blood plasma by
filtration

15. FORMATION: CEREBROSPINAL
FLUID
• Because the ependymal cells are joined
by tight junctions, materials entering CSF
from choroid capillaries cannot leak
between the cells instead they must pass
through the ependymal cells

16. FORMATION: CEREBROSPINAL
FLUID
• This blood-cerebrospinal fluid barrier
permits certain substances to enter the
CSF but excludes others, protecting the
brain & SC from potentially harmful
blood-borne substances

19. PROPERTIES:CEREBROSPINAL
FLUID
• It is a clear liquid
• Slightly alkaline fluid
• Specific gravity : 1.005
• Consists of H2O, mineral salts, glucose,
small amounts of plasma albumin &
globulin, small amounts of creatinine &
urea

20. FUNCTIONS :CEREBROSPINAL
FLUID
• It supports & protects the brain & SC
• It maintains a uniform pressure around
these delicate structures
• It acts as a cushion & shock absorber
between the brain & the cranial bones
• It keeps the brain & spinal cord moist &
there may be interchange of substances
between CSF & nerve cells, such as
nutrients & waste products

21. CEREBRUM
• Largest part of the brain
• It is divided by a cleft, the longitudinal
cerebral fissure, into right & left cerebral
hemispheres, each containing lateral
ventricles
• Deep within the hemispheres they are
connected by a mass of white matter
[nerve fibres] called the corpus callosum

22. CEREBRUM
• The superficial part of the cerebrum is
composed of nerve cell bodies or gray
matter forming cerebral cortex
• The deeper layer consists of nerve fibres
or white matter
• The cerebral cortex shows many
infoldings or furrows which interacts with
the surface area of brain

23. CEREBRUM
• The exposed areas of the folds are the
Gyri or Convolutions & these are
separated by Sulci [fissures]
• It is divided into 4 lobes for descriptive
purpose
1. Frontal
2. Parietal
3. Temporal
4. Occipital

24. CEREBRUM
• The boundaries of the lobes are marked
by deep sulci
Gyri

25. Central sulcus
Lateral sulcus
Parieto-occipital
sulcus

26. INTERIOR OF CEREBRUM
• The surface of the cerebral cortex is
composed of grey matter [nerve cell
bodies]
• Within the cerebrum the lobes are
connected by masses of nerve fibres, or
tracts, which make up the white matter
of the brain

27. INTERIOR OF CEREBRUM
• The afferent & efferent fibres linking the
different parts of the brain & SC are as
follows
1. Association tracts connects different
parts of the cerebral hemispheres by
extending from one Gyrus to another

28. FUCTIONAL AREAS OF
CEREBRUM
2. Commisural tracts connect
corresponding areas of the two cerebral
hemispheres
e.g. Corpus Callosum
3. Projection tracts connect the cerebral
cortex with grey matter of lower parts of
the brain & with the SC
e.g. Internal Capsule

31. FUCTIONAL AREAS OF
CEREBRUM
• In general, motor impulses leave from
the anterior part of each cerebral
hemispheres while sensory impulses
arrive at the posterior part i.e. behind the
central sulcus
1. Motor areas
2. Sensory areas
3. Association areas

32. MOTOR AREAS
1. Primary Motor Area (4)
2. Broca’s [Motor Speech] area (44, 45)

33. MOTOR AREAS
1. Primary Motor Area
• Lies in the frontal lobe immediately
anterior to the central sulcus
• The cell bodies are pyramid shaped c/a
Bet’z cells
• They initiate the contraction of skeletal
muscles

36. MOTOR AREAS
1. Primary Motor Area
• The left hemisphere of cerebrum controls
voluntary muscle movements on the
right side of the body & vice versa
• The uppermost cells control the feet &
those in the lowest part control the head,
neck, face & fingers

37. MOTOR AREAS
2. Broca’s [Motor speech] area
• Situated in the frontal lobe just above
the lateral sulcus
• Controls muscle movements necessary
for speech
• It is dominant in left hemisphere in right
handed people & vice versa

39. SENSORY AREAS
1. Primary Somatosensory Area
2. Primary Auditory area
3. Primary Olfactory area
4. Primary Gustatory area
5. Primary Visual area

40. SENSORY AREAS
1. Primary Somatosensory Area
• Located behind the central sulcus
• Sensations of pain, temperature,
pressure, touch, awareness of muscular
movements & the position of the joints
• This area of right handed people receives
impulse from the left side of the body &
vice versa

41. Somatosensory Area

42. SENSORY AREAS
2. Primary Auditory Area
• Lies below the lateral sulcus within
temporal lobe
• The nerve cells receives & interpret
impulses transmitted from the inner ear
by the cochlear [auditory] part of the
vestibulocochlear nerves [8th
cranial
nerve]

44. SENSORY AREAS
3. Primary Olfactory Area
• Lies deep within temporal lobe
• Impulses from the nose, transmitted via
the olfactory nerves [1st
cranial nerve] are
received & interpret

46. SENSORY AREAS
4. Primary Gustatory Area
• Lies above the lateral layers in the deep
layers of the somatosensory area
• Impulses from sensory receptors in taste
buds are received & perceived as taste

48. SENSORY AREAS
5. Primary Visual Area
• Lies behind parieto-occipital sulcus &
includes the greater part of the occipital
lobe
• The optic nerve [2nd
cranial nerve] passes
from the eye to this area which receives
& interprets the impulse as visual
impression

50. ASSOCIATION AREAS
1. Somatosensory Association area
2. Visual Association area
3. Facial recognition area
4. Auditory association area
5. Orbitoforntal Area
6. Wernicke’s area
7. Common integrative area

51. ASSOCIATION AREAS
8. Prefrontal cortex
9. Premotor Area
10. Frontal Eye Field Area

52. ASSOCIATION AREAS
1. Somatosensory Association area:
• Posterior to primary somatosensory area
• Receives input from primary
somatosensory area, thalamus & other
parts of the brain
• Functions:
• To determine the exact shape and
texture of an object by feeling it

53. ASSOCIATION AREAS
1. Somatosensory Association area:
• To sense the relationship of one body
part to another
• Storage of memories of past somatic
sensory experiences, enabling you to
compare current sensations with
previous experiences
• E.g recognition of pencil

54. ASSOCIATION AREAS
2. Visual Association area:
• Located in occipital lobe
• Receives sensory impulses from primary
visual area and thalamus
• Function: Relates present & past visual
experiences and is essential for
recognizing and evaluating what is seen
• E.g. spoon simply by looking at it

55. ASSOCIATION AREAS
3. Facial recognition area
• Present in inferior temporal lobe
• Receives impulses from visual association
area
• Function: Stores and allows to recognize
people by their faces
• It is dominant in right hemesphere

56. ASSOCIATION AREAS
4. Auditory association area
• Inferior & posterior to the primary
auditory area in the temporal cortex
• Function: To recognize particular sound
as speech, music or noise

57. ASSOCIATION AREAS
5. Orbitoforntal Area
• Along the lateral part of the frontal lobe
• Receives sensory impulses from the
primary olfactory area
• Functions: To identify odors
• To discriminate among different odors
• It is dominant in right hemisphere

58. ASSOCIATION AREAS
6. Wernicke’s area
• A broad region in the left temporal &
parietal lobes
• Functions: Interprets the meaning of
speech by recognizing spoken words
• It is active as you translate words into
thoughts
• Also contribute to verbal communication
by adding emotional content like joy

59. ASSOCIATION AREAS
7. Common integrative area
• Bordered by somatosensory, visual and
auditory association area
• Receives impulses from these areas &
primary gustatory area, thalamus, parts
of the brain stem

60. ASSOCIATION AREAS
7. Common integrative area
• Integrates sensory interpretations from
the association area & impulses from
other areas
• Function: Allows the formation of
thoughts based on a variety of sensory
inputs

61. ASSOCIATION AREAS
7. Common integrative area
• Transmits signals to other parts of the
brain for the appropriate response to the
sensory signals it has interpreted

62. ASSOCIATION AREAS
8. Prefrontal cortex:
• Anterior portion of frontal lobe
• Nemerous connections with other areas
of cerebral cortex, thalamus,
hypothalamus, limbic system and
cerebellum

63. ASSOCIATION AREAS
8. Prefrontal cortex: is concerned with
• Makeup of a person’s personality,
intellectual ability, complex learning
abilities
• Recall of information, initiative,
judgment, foresight, reasoning
• Conscience, intuition, mood, planning for
the future, development of abstract ideas

64. ASSOCIATION AREAS
9. Premotor Area:
• Anterior to primary motor area
• Communicate with primary motor cortex,
the sensory association area in the
parietal lobe, basal ganglia and the
thalamus

65. ASSOCIATION AREAS
9. Premotor Area:
• Function:
• Deals with learned motor activities of a
complex and sequential nature(writing)
• Memory bank for such movements

66. ASSOCIATION AREAS
10. Frontal Eye Field Area:
• In frontal cortex
• Said to be the part of premotor area
• Controls voluntary scanning movements
of the eyes (reading)

67. FUNCTIONS: CEREBRAL CORTEX

68. THE DIENCEPHALON [Thalamus]
• Consists of paired oval masses of gray
matter organized into nuclei with
interspersed tracts of white matter
• Intermediate mass [Interthalamic
adhesion]: Bridge of gray matter joins
right & left halves of the thalamus

70. THE DIENCEPHALON [Thalamus]

71. THE DIENCEPHALON [Thalamus]
• Internal capsule: Thick band of white
matter lateral to thalamus

72. THE DIENCEPHALON [Thalamus]
• Internal Medullary Lamina: Y-shaped
sheet of white matter which divides gray
matter of thalamus into right & left sides
of the thalamus

73. THE DIENCEPHALON [Thalamus]
• Seven major groups of nuclei on each side
of the thalamus
I. Anterior nucleus
II. The Medial Nuclei
III. Lateral Group Nuclei
IV. Ventral Group Nuclei
V. Intralaminar Nuclei
VI. Midline Nucleus
VII. Reticular Nucleus

74. THE DIENCEPHALON [Thalamus]
I. Anterior nucleus
• Connects thalamus to hypothalamus &
limbic system
• Function: Emotions, Regulation of
alertness, memory

76. THE DIENCEPHALON [Thalamus]
II. The Medial Nuclei
• Connects to the cerebral cortex, limbic
system, basal ganglia
• Function: Emotions, Learning, Memory,
awareness, Cognition

78. THE DIENCEPHALON [Thalamus]
III. Lateral Group Nuclei
• Connects to superior colliculi, limbic
system & cortex in all lobes of cerebrum
• Function:
a. Lateral Dorsal nucleus: Expression of
emotions
b. Lateral Posterior & Pulvinar Nucleus:
Integrate sensory information

80. THE DIENCEPHALON [Thalamus]
IV. Ventral Group Nuclei
a. Ventral Anterior Nucleus
• Motor functions e.g. Movement
planning
b. Ventral Lateral Nucleus
• Connects to the cerebellum & motor
parts of the cerebral cortex
• Neurons are active during movements
on the opposite side of the body

81. THE DIENCEPHALON [Thalamus]
IV. Ventral Group Nuclei
c. Ventral Posterior Nucleus
• Relay impulses for somatic sensations
e.g. Touch, pressure, proprioception,
vibration, heat, cold, pain from the face
& body to cerebral cortex

83. THE DIENCEPHALON [Thalamus]
IV. Ventral Group Nuclei
a. Lateral Geniculate Nucleus
• Relays visual impulses for sight from the
retina to the visual area of cerebral
cortex

84. THE DIENCEPHALON [Thalamus]
IV. Ventral Group Nuclei
e. Medial Geniculate Nucleus
• Relays auditory impulses for hearing
from ear to 10 visual area [cerebral
cortex]

86. THE DIENCEPHALON [Thalamus]
V. Intralaminar Nuclei
• Lie within he internal medullary lamina
• Connects to reticular formation,
cerebellum, basal ganglia & wide areas
of cerebral cortex
• Function: Pain perception, integration of
sensory & motor information & arousal

88. THE DIENCEPHALON [Thalamus]
VI. Midline Nucleus
• Forms a thin band adjacent to the 3rd
ventricle
• Function: Memory & Olfaction

89. Midline Nucleus

90. THE DIENCEPHALON [Thalamus]
VII. Reticular Nucleus
• Surrounds lateral aspect of thalamus,
next to the internal capsule
• Function: Monitors, filters, integrates
activities of other thalamic nuclei

91. Reticular nucleus

92. THE DIENCEPHALON
[Hypothalamus]
• Small part of diencephalon located
inferior to the thalamus
• Consists of 4 regions
1. Mamillary region
2. Tuberal region
3. Supraoptic region
4. Preoptic region

94. THE DIENCEPHALON
[Hypohalamus]
1. Mamillary region
• Adjacent to midbrain, posterior part of
hypothalamus
• Includes
a. Mamillary bodies: Two, small rounded
projections
• Function: Relay stations reflexes related
to smell

95. THE DIENCEPHALON
[Hypohalamus]
1. Mamillary region
b. Hypothalamic nuclei:
• Thermoregulation
• Panting
• Sweating
• Thyrotropin inhibition

96. 2. Tuberal Region

98. THE DIENCEPHALON
[Hypohalamus]
3. Supraoptic region
• lies superior to the optic chism
• Axons of paraventricular & supraoptic
nuclei from hypothalamohypophyseal
tract, extends through the infundibulum
i.e. posterior lobe of pituitary gland

99. Supraoptic region consists of

101. THE DIENCEPHALON
[Hypohalamus]
4. Preoptic region
• Anterior to supraoptic region [2 nuclei]
• Function: Regulation of autonomic
activities, release of gonadotropin
releasing hormone
• Medial preoptic nuclei: Temperature
regulation of blood composition
• Lateral preoptic nuclei: Non-REM sleep

103. THE DIENCEPHALON
[Hypothalamus : Functions]
1. Control of the ANS:
• Controls & integrates activities of the
ANS which regulates contraction of
smooth & cardiac muscle & the
secretions of many glands
• Through the ANS ; it regulates
i. Heart rate
ii. Movement of food through G.I.T.
iii. Contraction of urinary bladder

104. THE DIENCEPHALON
[Hypothalamus : Functions]
2. Production of hormones: releasing or
inhibitory hormones

105. THE DIENCEPHALON
[Hypothalamus : Functions]
2. Production of hormones:

106. THE DIENCEPHALON
[Hypothalamus : Functions]
3. Regulation of emotional & behavioral
patterns:
• Together with the limbic system
participates in expressions of rage,
aggression, pain, pleasure & behavioral
patterns related to sexual arousal

107. THE DIENCEPHALON
[Hypothalamus : Functions]
4. Regulation of eating & drinking
Feeding
center
Promotes eating
Satiety center Sensation of fullness and cessation of
eating
Thirst center Increases of osmotic pressure of ECF
and cause sensation of thirst. Intake
of water restores osmotic pressure
and removing stimulation, relieves
thirst

108. THE DIENCEPHALON
[Hypothalamus : Functions]
5. Control of body temperature:
• If temperature of blood flowing through
hypothalamus is above normal , it
directs ANS
• This will stimulate activities that
promote heat loss & vice versa

109. THE DIENCEPHALON
[Hypothalamus : Functions]
6. Regulation of circadian rhythm & state
of consciousness:
• Suprachiasmatic nucleus : patterns of
awakening & sleep that occur on a
circadian schedule (body’s internal clock)
• Receives input from eyes --- output to
other hypothalamic nuclei, reticular
formation, pineal gland

110. THE DIENCEPHALON
[Epithalamus]
Small region superior & posterior thalamus.
Consists of :
1. Pineal gland
• Size of a small pea, protrudes from the
posterior midline of the 3rd
ventricle
• Part of endocrine system: secrets
melatonin during the night time,
promotes sleepiness

111. THE DIENCEPHALON
[Epithalamus]
Small region superior & posterior thalamus.
Consists of :
1. Pineal gland
• Sets body’s biological clock if taken
orally
• Helps to relieve jet lag

112. THE DIENCEPHALON
[Epithalamus]
2. Habenular nuclei:
• Olfaction especially with respect to
emotional response
• E.g Mom’s chocolate chip cookies baking
in the oven

113. CIRCUMVENTRICULAR ORGANS
• Lie in the wall of 3rd
ventricle
• Can monitor the chemical changes in the
blood because they lack a blood-brain
barrier
• Include part of the hypothalamus, the
pineal gland, the pituitary gland and few
nearby structures

114. CIRCUMVENTRICULAR ORGANS
• Functions: coordinate the homeostatic
activities of the endocrine and nervous
systems such as
1. Regulation of blood pressure
2. Fluid balance
3. Hunger
4. Thirst

116. THE BRAIN STEM
1. MEDULLA OBLONGATA
2. PONS
3. MIDBRAIN

117. THE BRAIN STEM
MEDULLA OBLONGATA
• Continuous with the superior part of the
brain stem & forms inferior part of the
brain stem
• Begins at foramen magnum & extends to
the inferior border of pons

118. THE BRAIN STEM
MEDULLA OBLONGATA
• White matter contains all sensory
[ascending, input] & motor[descending,
output] tracts that extend between the
spinal cord & brain
• Some of the white matter forms bulges
on the anterior aspect of the medulla,
these protrusions are called pyramids
formed by large corticospinal tracts [SC
& brain]

119. THE BRAIN STEM
MEDULLA OBLONGATA
• Just superior to the junction of the
medulla with the SC: Decussation of
pyramids
• 90% axons in the left pyramid cross to
the right side and 90% axons in the right
pyramid cross to the left side

120. THE BRAIN STEM
MEDULLA OBLONGATA
• Also contains several nuclei, masses of
gray matter where neuron synapses with
one another

121. THE BRAIN STEM
MEDULLA OBLONGATA
• Olive: Just lateral to each pyramid is an
oval shaped swelling called an Olive
• Inside Olive is Inferior Olivery nucleus:
Receives input from cerebral cortex, red
nucleus of midbrain and spinal cord

122. THE BRAIN STEM
MEDULLA OBLONGATA
• Axons from Inferior olivary nucleus
extends into the cerebellum and
controls the cerebellar neuronal activity
with respect to muscle activities as we
learn new motor skills

123. THE BRAIN STEM
MEDULLA OBLONGATA
• Right & left Gracile nucleus & Cuneate
nucleus:
 Located in the posterior part
 Ascending sensory axons of the gracile
fasciculus & the cuneate fasciculus
which are the two tracts in the posterior
columns of the spinal cord, form
synapses with these nuclei

124. THE BRAIN STEM
MEDULLA OBLONGATA
• Axons extends to the thalamus as a band
of white matter i.e. Medial lemniscus
extends through medulla, pons &
midbrain
• The tracts of the posterior columns and
the axons of the medial lemniscus are
collectively called as posterior column-
medial lemniscus pathway

125. Nerve Input Output Function
Vestibulocochle
ar nerves [VIII]
Cochlea of the internal ear Impulses related
to hearing
Glossopharynge
al nerves [IX]
Nuclei in the medulla relay sensory
& motor impulses
Taste,
swallowing &
salivation
Vagus nerve [X] Nuclei in the medulla relay sensory
& motor impulses to pharynx,
larynx, abdominal & thoracic
viscera
Parasympthetic
innervation
Accessory nerve
[XI]
Nuclei in the
medulla
Vagus nerve Fibers are part
of vagus nerve
Swallowing
Hypoglossal [XII] Tongue Nuclei in the
medulla
Tongue
movements
during speech &

126. THE BRAIN STEM
MEDULLA OBLONGATA
Nucleus Input Sensations Pathway
Gustatory Taste buds Taste Gustatory
Cochlear Cochlea of the
Inner ear
Hearing Auditory
Vestibular Proprioceptor
s in the
vestibular
apparatus of
the inner ear
Equilibrium Equilibrium

127. MEDULLA OBLONGATA:
FUNCTIONS
1. Decussation of Pyramids:
• Motor nerves descending from the
motor area in the cerebrum to the spinal
cord in the pyramidal tracts cross from
one side to the other
• i.e. left hemisphere of the cerebrum
controls the right half of the body & vice
versa [skeletal muscles are involved]

128. MEDULLA OBLONGATA:
FUNCTIONS
2. Sensory Decussation:
• Some of sensory nerves ascending to the
cerebrum from the spinal cord cross one
side to the other in the medulla

129. 3. Cardiovascular centre
• Controls the rate &
force of cardiac
contraction
• Controls BP
• Within CVC, there
is vasomotor
centre
• Vasomotor centre:
• Controls the diameter
of blood vessels :
arterioles & arteries
• Stimulated by atrial
baroreceptors, body
temerature &
emotions like anger,
pain

130. MEDULLA OBLONGATA:
FUNCTIONS
4. Respiratory centre:
• Medullary rhythmicity area: Controls
the rate & depth of respiration
• Nerve impulses will pass to the phrenic
& intercostal nerves which stimulate the
contraction of diaphragm & intercostal
muscles initiating inpiration

131. MEDULLA OBLONGATA:
FUNCTIONS
5. Reflex centre:
• Irritants present in the stomach or
respiratory tract stimulate the medulla
oblongata, activating the reflex centre

132. MEDULLA OBLONGATA:
FUNCTIONS
Vomiting
canter
Forcible expulsion of the contents of
the upper G.I. tract through mouth
Deglutition
center
Promotes swallowing of a mass of food
that has moved from the oral cavity of
the mouth into the pharynx
Sneezing Spasmodic contractions of breathing
muscles that forcefully expel air through
the nose & mouth

133. MEDULLA OBLONGATA:
FUNCTIONS
Coughing Long drawn, deep inhalation & strong
exhalation through the upper
respiratory tract
Hiccupping Spasmodic contractions of diaphragm
producing a sharp sound after
inhalation

134. PONS
• Superior to medulla, anterior to the
cerebellum, 2.5cm long
• Has both nuclei & tracts
• It connects various parts of the brain,
connections provided by bundles of
axons

135. PONS
• Connects right & left sides of the cerebellum
• Pontine nuclei:
1. Ventral region of pons made up of scattered
gray matter i.e. a relay station
2. Signals for the voluntary movements originate
in the cerebral cortex & relayed to the
cerebellum

136. PONS
• Connects right & left sides of the cerebellum
• Pneumotoxic area & the Apneustic area:
1. Nuclei located in the above areas together
with medullary rhythmicity area controls
breathing

137. Nerve Input Output Function
Trigeminal
nerve [V]
Somatic
sensations
from head
& face
Governs Chewing
Abducens nerve
[VI]
Motor impulses controls
eyeball movement
Facial nerve [VII] Taste Regulate secretion of saliva, &
tears and contraction of
muscles of facial expressions
Vestibulocochle
ar nerve [VIII]
Receive sensory impulses &
provide motor impulses to
vestibular apparatus
Balance &
Equilibrium

138. MIDBRAIN
• Extends from the pons to diencephalon
• 2.5 cm long
• Cerebral aqueduct passes through the
midbrain, connecting 3rd
& 4th
ventricle
• Has tracts & nuclei

139. MIDBRAIN
• Anterior part contains a pair of tracts c/a
Cerebral penducle
• Contains:
1. Corticospinal: Cerebrum to SC
2. Corticopontine : Cerebrum to Pons
3. Corticobulbar: Cerebrum to Medulla

140. MIDBRAIN
• The posterior part i.e. tectum contains 4
rounded elevations
A. Superior colliculi
B. Inferior colliculi
C. Substantia nigra
D. Red nuclei

141. MIDBRAIN: A] Superior colliculi
• 2 superior elevations ie. nuclei: through
neural circuits from superior colliculi controls
i. Visual reflex [extrinsic]
e.g. Tracking moving images, Scanning stationary
images
ii. Reflexes that govern movements of the eyes,
head & neck in response to visual stimuli

142. MIDBRAIN: B] Inferior colliculi
• 2 inferior elevations
i. Part of auditory pathway:
• hearing sensations received from the inner
ear to the brain
ii. Startle Reflex:
• Sudden movements of head, body & trunk in
response to a loud noise like gunshot

143. MIDBRAIN: C] Substantia Nigra
• Two nuclei: Right & Left
• Large & darkly pigmented
• Neurons that release dopamine, extending
from the substantia nigra to basal ganglia
• Helps control subconscious muscle activities
[Loss of these neurons : Parkinsonism]

144. MIDBRAIN: D] Red Nuclei
• Two nuclei: Right & Left
• Reddish due to rich blood supply, Fe
containing pigment in their neuronal cell
bodies
• Axons from cerebellum & cerebral cortex
synapses with Red nuclei controlling muscular
movements

145. MIDBRAIN: D] Red Nuclei
• Coordinate with cerebellum for muscle
movements
Nerve Function
Occulomotor
nerve [III]
Motor impulses to controls
movement of eye balls &
smooth muscles in the eyeball
to regulate constriction of the
pupil & changes in the shape
Trachlear nerve
[IV]`
Controls movement of eye balls

146. MIDBRAIN: FUNCTIONS
• Nuclei & nerve fibres [tracts] connect the
cerebrum with lower parts of the brain & SC
• The nuclei acts as relay stations for the
ascending & descending nerve fibres.

147. THE CEREBELLUM
• 2nd
only to cerebrum size; 1/10th
of the brain
mass
• Posterior to medulla & pons, inferior to
posterior portion of cerebrum
• A deep groove known as transverse fissure,
along with the tentorium cerebelli [supports
posterior part of the cerebrum] separates
cerebellum from cerebrum

148. THE CEREBELLUM
• Central constricted area: Vermis, lateral lobes
are cerebellar hemisphere
• Each hemisphere consists of lobes separated
by deep & distinct fissures

149. THE CEREBELLUM
i. Anterior & posterior lobe govern
subconscious aspect of skeletal muscle
movements
ii. Flocculonodular lobe: +nt on the inferior
surface & is responsible for equilibrium &
balance

150. THE CEREBELLUM
• Superficial layer is c/a cerebellar cortex
• In cortex gray matter in a series of slender,
parallel ridges called folia
• Deep to gray matter are the tracts of white
matter c/a Arbor vitae

151. THE CEREBELLUM
• Deep within are the cerebellar nuclei
• They are the regions of gray matter
• Receives impulses from other brain centers &
SC

152. THE CEREBELLUM
• Bundles of white matter are c/a cerebellar
peduncle
i. Inferior cerebellar penducles
• Sensory Impulses from Vestibular apparatus
of the inner ear & proprioceptors through the
body is received by cerebellum
• Axons extends from Inferior Olivery nucleus
[Medulla] & Spinocerebellar penducles to
cerebellum

153. THE CEREBELLUM
ii. Middle cerebellar penducles
• Largest penduncle
• Pontine nuclei:
1. Commands for voluntary movements
2. Impulses from cerebral cortex to cerebellum

154. THE CEREBELLUM
iii. Superior cerebellar penducles
• Axons extend from the cerebellum to Red
nuclei [Midbrain]
• Axons extend from the cerebellum to Nuclei
[Thalamus]

155. THE CEREBELLUM
• When movements initiated by the cerebral
motor areas of the cerebral cortex are not
being carried out correctly, cerebellum
detects discrepancies
• The feedback signals help to correct the
errors, smooth the movements & coordinate
complex sequences of skeletal muscle
contractions

156. THE CEREBELLUM: FUNCTIONS
• Cerebellar activity not under voluntary
control
• It controls & coordinates the movements of
various groups of muscles ensuring smooth,
even precise movements
• It coordinates activities associated with the
maintenance of posture, balance &
equilibrium

157. THE CEREBELLUM: FUNCTIONS
• The sensory inputs for these functions are
derived from the muscles & joints, the eyes &
the ears
• Impulses from the cerebellum influence the
contraction of skeletal muscles so that
balance & posture are maintained
• It also plays a role in learning & language
processing

158. THE CEREBELLUM: FUNCTIONS
• Damage to the cerebellum results in clumsy
uncoordinated muscular movement, inability
to carry out smooth, steady, precise
movements

159. RETICULAR FORMATION
• It is a collection of neurons in the core of the
brain stem surrounded by neural pathways
• These neural pathways conduct ascending &
descending nerve impulses between the brain
& SC
• This part is receiving information from the
various parts of the brain & is transmitting in
ascending

160. RETICULAR FORMATION
• The ascending portion of the reticular
formation is called as Reticular Activation
System
• Consists of sensory axons that project to the
cerebral cortex , both directly & through the
thalamus

162. RETICULAR FORMATION [FNn
]
1. Consciousness:
• A state of wakefulness when an individual is
fully alert, aware & oriented
• Visual & auditory stimuli and mental activities
can stimulate the RAS to maintain
consciousness

163. RETICULAR FORMATION [FNn
]
2. Arousal:
• Awakening from sleep
3. To maintain attention or alertness
4. Prevents sensory overload by filtering
insignificant information so that it does not
reach consciousness

164. RETICULAR FORMATION [FNn
]
5. Inactivation produces sleep, a state of partial
consciousness from which a person can be
aroused
6. Damage to RAS can lead to coma, a state of
partial consciousness from which a person
cannot be aroused

165. RETICULAR FORMATION [FNn
]
• The descending portion of RAS has
connections to cerebellum & SC
• Functions:
1. Regulates muscle tone [involuntary
contractions]
2. Regulates heart rate, blood pressure &
respiratory rate

166. BASAL NUCLEI
• Deep within each cerebral hemisphere are
three nuclei that are collectively termed as
Basal nuclei/ganglia
• Globus Pallidus & Putamen:
• The two basal nuclei lies side-by-side
• Globus pallidus closer to the thalamus &
Putamen closer to the cerebral cortex
• Both are called as Lentiform nucleus

167. BASAL NUCLEI
• Caudate nucleus: large ‘head’ connected to a
smaller ‘tail’ by a long comma-shaped ‘body’
• Corpus striatum:
1. Lentiform & Caudate nuclei together are c/a
Corpus striatum
2. Striated appearance of internal capsule as it
passes among the basal nuclei

168. BASAL NUCLEI
• Axons from the substantia nigra terminate in
the caudate nucleus & putamen
• The subthalamic nuclei interconnect with the
globus pallidus
• Clastrum: A thin sheet of gray matter situated
lateral to the putamen; function is unclear

170. BASAL NUCLEI [FNn
]
1. Receives input from the cerebral cortex &
provide output to the motor parts of the
cortex via medial & ventral group nuclei of
thalamus
2. Activity of neurons in the putamen precedes
or anticipates body movements
3. Activity of neurons in the caudate nucleus
occurs prior to eye movements

171. BASAL NUCLEI [FNn
]
4. The globus pallidus helps to regulate the
muscle tone required for specific body
movements
5. Controls subconscious contractions of skeletal
muscles
6. Involved in attention, memory & planning ;
with limbic system to regulate emotional
behaviour

172. BASAL NUCLEI [FNn
]
• Related disorders: Parkinsonism, Obsessive-
compulsive disorder, schizophrenia % Chronic
anxiety

173. THE LIMBIC SYSTEM
• Location:
 Encircling the upper part of the brain stem &
the corpus callosum is a ring of structures on
the inner border of the cerebrum & the floor
of the diencephalon that constitute Limbic
system

174. THE LIMBIC SYSTEM
• Structure:
• Limbic lobe is a rim of the cerebral cortex on
the medial surface of each hemisphere.
• It includes the cingulate gyrus which lies
above the corpus callosum
• Parahippocampus gyrus: Temporal lobe
below
• Hippocampus: Part of parahippocampal gyrus

176. THE LIMBIC SYSTEM: STRUCTURE
• Dentate gyrus: Between hippocampus &
parahippocampus gyrus
• Amygdala: Group of neurons close to the tail
of caudate nucleus
• Septal nuclei: In the septal area formed by the
regions under corpus callosum

178. THE LIMBIC SYSTEM: STRUCTURE
• Mamillary bodies: Two rounded masses
• Two nuclei of thalamus: Anterior & Medial
nucleus
• Olfactory bulbs: Flattened bodies of the
olfactory pathway

180. THE LIMBIC SYSTEM: STRUCTURE
• Fornix, stria terminalis, medial forebrain
bundle & mammilothalamic tract are linked
by bundles of interconnecting myelinated
axons

182. THE LIMBIC SYSTEM: FUNCTIONS
• It is c/a ‘emotional brain’ because it plays a
primary role in a range of emotions, including
pain, pleasure, affection & anger
• Also involved in olfaction [smell] & memory
• A person whose amygdala is damaged fails to
recognize fearful expressions in others or to
express fear in appropriate situations

183. THE LIMBIC SYSTEM: FUNCTIONS
• Hippocampus together with other parts of the
cerebrum, functions in memory
• People with damage to certain limbic system
structures forget recent events