Anatomy of Human Brain Presented by Dr Arman MD (Resident) Physical Medicine & Rehabilitation, Dhaka Medical College, Dhaka, Bangladesh. reference taken from latest book & journal.
1. Anatomy of Brain
Dr SM Arman Hossain
MD Resident (Phase-A)
Department of Physical Medicine
And Rehabilitation
Dhaka Medical College
2. The Brain
The human brain is by far the most complex & highly organized
structure of the body. This organ allows us to think, move, feel,
see, hear, taste, and smell. It controls our body, receives,
analyzes, and stores information. produces electrical signals,
which, together with chemical reactions, let the parts of the body
communicate.
3. The Brain
The adult human brain weighs on average about 1.2–1.4 kg (2.6–
3.1 lb), or about 2% of total body weight with a volume of
around 1260 cm3 in men and 1130 cm3 in women. Despite this
relatively small mass, the brain contains approximately 100
billion neurons. Functioning as a unit, these neurons make up the
most complex and highly organized structure on earth.
4. Neuron
Neurons (also known as nerve cell) are the basic units
of the nervous system. Neurons are excitable cells that
are specialized for the reception of stimuli and the
conduction of the nerve impulse.
5. Types of the neurons (Snell NeuroAnatomy, Table 2-1)
Types Site
According to the number of processes
1. Unipolar • Dorsal root ganglion.
2. Bipolar • Retinal bipolar cells.
• Cells of the sensory cochlear &
vestibular ganglia
3. Multipolar • Fiber tracts of the brain and spinal
cord.
• peripheral nerves & motor cells of
spinal cord
According to the size of the neuron
1. Golgi Type 1(Long axon) • Purkinje cells of the cerebellar cortex
• Motor cells of the spinal cord
2. Golgi Type 2 (Short axon) • Cerebral and cerebellar cortex
8. Functional Parts of brain
There are mainly 3 functional region of brain:
• Motor areas
• Sensory areas
• Association areas
9. Structures of the cerebrum
External Structure
Internal Structure
Longitudinal fissure
Tentorium cerebelli
Sulci/Sulcus
Gyri/Gyrus
Corpus callosum
Grey matter
White matter
10. Longitudinal fissure & Tentorium cerebelli.
• It consists of two cerebral hemispheres (left and right)
• cerebral hemispheres are separated by a longitudinal fissure
containing sickle-shaped fold of dura mater called falx
cerebri.
• A second fold of dura mater seperates the cerebral
hemispheres from the cerebellum & is called Tentorium
cerebelli
12. Gyrus and Sulcus
The superficial region of the brain is called the cortex.The surface
is not smooth, it’s convoluted. Each bump on the surface of the
cerebrum is called a Gyrus (ridges or elevations), and each
shallow groove on the surface of the cerebrum is called a Sulcus
(grooves or depressions)
14. Medial View of brain (Atlas of Human Aanatomy, f.h.Netter)
15. The main sulci are:
Central sulcus – groove separating the frontal and parietal lobes.
Lateral sulcus – groove separating the frontal and parietal lobes
from the temporal lobe.
The main gyri are:
Precentral gyrus – ridge directly anterior to central sulcus,
location of primary motor cortex.
Postcentral gyrus – ridge directly posterior to central sulcus,
location of primary somatosensory cortex.
Superior temporal gyrus – ridge located inferior to lateral
sulcus, responsible for the reception and processing of sound.
16. Corpus Callosum
This is the area that is responsible for the right half of
the brain communicating with the left half of the brain.
If the corpus callosum was cut, there would be no
communication between the right and left halves of the
brain.
• This is the area that
is responsible for the
right half of the brain
communicating with
the left half of the
brain.
• If the corpus
callosum was cut,
there would be no
communication
between the right and
left halves of the
brain.
17. Lobes of the Cerebrum
The cerebral cortex is classified into four lobes,
according to the name of the corresponding cranial bone
that approximately overlies each part.
22. Frontal Lobe
The frontal lobe is the area of
the brain responsible for
higher cognitive functions.
These include:-
• Personality
• Emotional Control
• Social behaviour
• Contralateral motor control
• Language
• Micturation
23. Parietal Lobe
The parietal lobe plays a
role in-
• Language
• Calculation
• Spatial orientation
• Constructional skill
Parietal lobe also contains a
specialized area called Wernicke’s
area that is responsible for
matching written words with the
sound of spoken speech.
24. Temporal Lobe
The temporal lobe plays a
role in:
• Auditory perception
• Verbal & non verbal memory
• Smell
• Balance
• Language
• Melody & pitch perception
27. Depiction of the homunculus
A cortical homunculus is a distorted representation of the human
body, based on a neurological "map" of the areas and proportions
of the human brain dedicated to processing motor functions, or
sensory functions, for different parts of the body.
28. Vasculature
The blood supply to the
cerebrum can be simply
classified into 3 distinct
paired arterial branches:
Anterior Cerebral
Arteries – branches of
internal carotid arteries,
supplying the
anteromedial aspect of
the cerebrum.
Anterior cerebral Artery
Middle cerebral Artery
Posterior cerebral artery
Lateral Brain
29. Vasculature
Middle Cerebral
Arteries – continuation of
internal carotid arteries,
supplying most of the
lateral portions of the
cerebrum.
Posterior Cerebral
Arteries – branches of the
basilar arteries, supplying
both the medial and lateral
sides of the cerebrum
posteriorly.
Anterior cerebral Artery
Middle cerebral Artery
Posterior cerebral artery
Medial Brain
30. Artery Supply of the cerebrum (Atlas of Human Anatomy, f.h.Netter)
31. Circle of Willis
The circle of Willis lies in the interpeduncular fossa at
the base of the brain. It is formed by the anastomosis
between the two internal carotid arteries and the two
vertebral arteries.
The anterior communicating, anterior cerebral,
internal carotid, posterior communicating, posterior
cerebral, and basilar arteries all contribute to the
circle
35. Clinical Relevance (Stroke)
Stroke: Acute, focal brain dysfunction due to vascular
disease is called stroke.
Davidson 23rd, fig:26.1 A classification of stroke disease.
38. Thalamus
Thalamus means “inner
room” in Greek, as it sits
deep in the brain at the top
of the brainstem. The
thalamus is called the
gateway to the cerebral
cortex, as nearly all sensory
inputs pass through it to the
higher levels of the
brain(cerebral cortex)
Location- On each side of
third ventricle
41. Functions of Thalamus
• Sensory relay centre.
• Crude centre for perception of sensation.
• Arousal & alertness reaction.
• Language.
• Emotional aspect of behaviour.
• Sexual sensation.
• Reflex activity centre
• Integration of
Sensory impulses & Motor functions.
Visceral & somatic function.
42. Clinical relevance
Thalamic Hand
The contralateral hand is held in an abnormal posture in some
patients with thalamic lesions. The wrist is pronated and flexed,
the metacarpophalangeal joints are flexed, and the
interphalangeal joints are extended. The fingers can be moved
actively, but the movements are slow. The condition is due to
altered muscle tone in the different muscle groups.
43. Hypothalamus
The hypothalamus is situated under
the thalamus at the top of the
brainstem. Although the
hypothalamus is small, it controls
many critical bodily functions:
• Controls autonomic nervous system
• Regulates body temperature
• Regulates food intake
Hypothalamus
44. Hypothalamus
• Regulates water balance and thirst
• Controls sleep-wake cycles
• Functionally, the hypothalamus is part of the limbic system
(which is involved in memories and emotions), so that’s why a
painful memory can increase blood pressure, and a good
memory can lower blood pressure. It is the Center for
emotional response and behavior
• The hypothalamus synthesizes and secretes hormones, and
these in turn stimulate or inhibit the secretion of pituitary
hormones & thus Controls endocrine system.
45. Basal ganglia
Subcortical mass of grey matter strongly interconnected with
cerebral cortex, thalamus & brainstem. forming important parts
of extrapyramidal system
Parts-
1. Corpus Striatum
a. Caudate Nucleus
b. Lentiform Nucleus
2. Amygdaloid Body
3. Claustrum
Globus pallidus
Putamen
48. Main functional components of basal ganglia
1. Corpus Striatum
a. Caudate Nucleus
b. Lentiform Nucleus
Corpus striatum receives information from :- Cerebral cortex,
Thalamus, Subthalamus, brainstem, Substantia nigra
2. Subthalamic nucleus: receives information from brain areas
3. Substantia nigra :receives from globus pallidus &
subthalamic nucleus.
49. Functions of basal ganglia
1. Basal nuclei control muscular movement by influencing the
cerebral cortex & have no direct control of descending
pathways.Thus influencing skill cortical motor activities like :-
- Routine behavioure or habit
- Cognition
- Passing football
- Drawing a diagram
- Writing letters of the alphabet
2. Exerts inhibitory influence on a number of motor system.
3. Help prepare for the movement.
55. Parkinson’s disease
Parkinsonism is a clinical syndrome characterised primarily by
bradykinesia , with associated increased tone (rigidity), tremor
and loss of postural reflexes.
Degenerative changes in globus pallidus & substansia nigra with
marked reduction of dopamin.
Classical Triad:
1. Tremor (Resting tremor)
2. Rigidity (increased muscle tone)
3. Bradykinesia (Slowness of movement)
56. Clinical features of Parkinson’s disease
• The motor symptoms are
almost always initially
asymmetrical.
• features are initially unilateral,
gradual bilateral involvement
evolves with time
• Unilateral rest tremor
affecting limbs, jaw and chin.
• Difficulties with rapid fine
movement such as difficulties
with fastening buttons, shaving
or writing
57. Clinical features of Parkinson’s disease
• Tiredness, mental slowness,
increasingly small
handwriting.
• Slowness of gait
• As the disease advances,
speech becomes softer and
indistinct
• Other neuropsychiatric
features (anxiety,
depression, apathy,
hallucinosis/psychosis).
58. Internal Capsule
Afferent and efferent nerve fibers passing to and from the
brainstem to the entire cerebral cortex must travel between large
nuclear masses of gray matter within the cerebral hemisphere. At
the upper part of the brainstem, these fibers form a compact band
known as the internal capsule.
59. Boundary of Internal Capsule
It is flanked medially by -
• Caudate nucleus & Thalamus
laterally by-
• Lentiform nucleus
Because of the wedge shape of the lentiform nucleus, as seen on
horizontal section, the internal capsule is bent to form an
anterior limb and a posterior limb, which are continuous with
each other at the genu
62. The Brainstem
The brainstem is the most primitive part of the brain and controls
the basic functions of life: breathing, heart rate, swallowing,
reflexes to sight or sound, sweating, blood pressure, sleep, and
balance.
The brainstem can be divided into three major sections:
1. Midbrain
2. Pons
3. Medulla oblongata
64. Blood supply of the brainstem
A. Midbrain-
Posterior Cerebral artery.
Superior Cerebellar artery.
Basilar artery.
B. Pons-
Superior Cerebellar artery.
Anterior Inferior Cerebellar artery.
Basilar artery.
C. Medulla Oblongata-
Posterior inferior cerebellar artery.
Basilar, Vertebral, Anterior and Posterior Spinal arteries
65. Blood supply of the brainstem
(Atlas of human anatomy, fh.netter)
67. Midbrain at the level of Superior Colliculus
(Snell Neuroanatomy, Figure 5-25)
68. Midbrain at the level of inferior Colliculus
(Snell Neuroanatomy, Figure 5-25)
69. Transverse section of midbrain
1. Cranial nerve – 3, 4
2. Temporopontine & fronto pontine fibres
3. Corticospinal & corticonuclear fibres
4. Red nucleus
5. Medial & trigeminal lemniscus
6. Medical longitudinal fasiculus (MLF)
7. Substantia nigra
70. Pons
Further down the
brainstem is the pons,
which relays sensory
information between
the cerebellum (for
balance) and
cerebrum (conscious
awareness).
71. Transverse section of pons
1. Cranial nerve:- 5,6,7,8
2. MTSL
M- Medial lemniscus (contains fibres from N. gracilis & N. cuneatus)
T - Trigeminal lemniscus (contains fibres from N. of trigeminal nerve)
S - Spinal lemniscus (contains fibres from lateral spinothalamic tract)
L - Lateral lemniscus (part of auditory pathway fibes arise from cochlear n.)
3. Medical longitudinal fasiculus (MLF)
4. Reticular formation
5. Corticospinal & corticonuclear tract etc.
72. Medulla Oblongata
At the base of the brainstem is the Medulla Oblongata,
which contains the cardiac, respiratory, vomiting and
vasomotor (blood vessel constriction) centers.
It controls the nerves that effect the heart rate, blood
pressure, and breathing.
Damage here causes coma. Swelling from an injury
causes pressure, which can damage this area, which can
cause a coma.
75. Limbic system
The limbic system is the area
of the brain that regulates
emotion and memory. It
directly connects the lower and
higher brain functions.
Components:
A. Cingulate gyrus
B. Fornix
C. Anterior thalamic nuclei
D. Hypothalamus
E. Amygdaloid nucleus
F. Hippocampus & para hippocampus
76. Functions of the limbic system
FEARS (mnemonic)
Fear, Food habit
Emotion & Endocrine
Anger
Recent memory
Sexual behaviour, Smell( Olfaction)
77. Reticular Formation
The brainstem contains extensive
fields of intermingled neuronal
cell bodies and nerve fibres,
which are collectively termed the
reticular formation.
Functions:
• Arousal
• Tonal Modulation
• Pain Processing
• Regulation of
– Vomiting & Coughing
– Respiration
– Speech Functions
79. Medial Medullary Syndrome (Davidsons 23rd )
Occulsion or thrombus of the medullary branch of vertebral
artery causes medial medullary syndrome. Features are:
Ipsilateral Contralateral
Paresis of the tongue which deviates
toward the lesion (damage to cranial
nerve XII)
Hemiplegia (damage to corticospinal tract)
with sparing of the face
Loss of position and vibratory
sensation (damage to medial lemniscus)
80. Lateral Medullary Syndrome (Wallenberg syndrome)
Occlusion in the Posterior inferior cerebellar artery. Features:
Ipsilateral Contralateral
Limb ataxia (damage to inferior cerebellar
peduncle and cerebellum)
loss of pain and temperature on
the body (damage to spinothalamic tract)
Analgesia & thermoanesthesia of the
face (damage to descending spinal tract and
nucleus of cranial nerve V)
Paralysis of palate, pharynx, and
vocal cord (damage to nuclei or fibers of IX
and X) with dysphagia and dysarthria
Horner's syndrome (damage to descending
sympathetic fibers)
Vertigo, nausea, vomiting, and nystagmus (damage to vestibular nuclei)
81. Clinical relevance ( Bulbar & Pseudobulbar palsy)
Bulbar palsy: Lower motor neuron lesion either at nuclear or
fascicular level within the medulla or from bilateral lesions of the
lower cranial nerves (9,10,11,12) outsie the brainstem is called
bulbar palsy.
Pseudobulbar palsy: Upper motor neuron lesions of the bulbar
muscles from lesions of the corticobulbar pathways in the
pyramidal tract is called pseudobulbar palsy
82. Cause of bulbar & Pseudobulber palsy
(Davisons, 22nd, Table:26.30)
83. C/F of bulbar & pseudobulbar palsy
Trait Bulbar palsy Pseudobulbar palsy
Lesion LMNL of CN:
9,10,11,12
UMNL of CN: 9,10,11,12
C/F:
Bulbar symptoms Dysarthria Dysphagia
Tongue Wasted & fibrilating Spastic, small & stiff
Speech Nasal Slow, slurred, indistinct
Nasal Regurgitation Present Absent
Jaw jerk Brisk Exaggerated (if the lesion
is above pons)
Palate Palatal paralysis Palatal & pharyngeal
reflexes are exaggerated.
84. Horner’s syndrome
Honrer’s syndrome occurs due to interruption of sympathetic
pathway to the head & neck.
Cause of Horner’s syndrome:
• Paralysis of cervical sympathetic fibre
• Bronchial carcinoma
• Syringobulba ( Lesion in the brainstem)
Features of Horner’s syndrome:
• Miosis
• Ptosis (partial)
• Enopthalmus ( Shunken of the eyeball)
• Squint ( Convergence)
• Anhydrosis
85. Cerebellum
• The cerebellum is situated in the posterior cranial fossa and is
covered superiorly by the tentorium cerebelli.
• It is the largest part of the hindbrain and lies posterior to the
fourth ventricle, the pons, and the medulla oblongata
• The cerebellum has two Hemispheres. They are connected by
Vermis
• Each hemisphere is divided into three main lobes: the anterior
lobe, the Posterior lobe and the flocculonodular lobe
• Cerebellum is functionally divided into 3 lobes:
Paleocerebellum, neocerebellum, Archicerebellum.
88. Funtions of the cerebellum
• Paleocerebellum (Spinal crebellum):Anterior lobe, uvula &
pyramid of the vermis
Function: Facilitate muscle tone & posture of the limb
• Neocerebellum (Cerebro-ponto cerebellum): Middle lobe
except uvula & pyramid.
Function: Concerning with smooth performance of skilled
act by co-ordinations of movement.
• Archicerebellum (vestibular cerebellum): Flocculonodular
lobe & lingula
Functions: Maintaining equilibrium, tone & posture of
trunk muscle
89. Blood Supply of cerebellum
Blood Supply
1. Superior surface- Superior Cerebellar Artery
2. Inferior Surface- Anterior Inferior Cerebellar Artery &
Posterior Inferior Cerebellar Artery
The veins drain into neighboring venous sinuses.
90. Signs of Cerebellar Lesion
Defect in posture
Hypotonia Decrease muscle tone
Defective attitude Turning of the face to the opposite side
Vertigo Sensation like the surround environment
is rotating
Nystagmus Tremor of eyeball when viewing towards
the same place
Deep reflexes Pendular jerks
91. Signs of Cerebellar Lesion
Defect in voluntarty movement
Asthenia Weakness of the movement
Ataxia Incoordinated movement
Asynergia Incocodination between protogonist
& antagonists
Decomposition of movement
Dysmetria Inability to arrest movement at
desired point.
Gait Reeling, legs wide apart deviated to
the same side
Disadidokinesia Cannot execute rapid & repeated
movement.
Intension tremor Tremor during movement
92. Venous drainage of the brain
All veins drain
into various
cranial
venous
sinuses which
in turn drain
into internal
jugular vein
93. Meninges of the brain
Brain is very important but delicate organ. It is protected by
following coverings:
1. Bony coverings of the cranium
2. Meninges
3. Cerebrospinal fluid (CSF)
94. Meninges of the brain
Meninges are the membranes covering of brain & spinal cord.
Composed of 3 layers:
1. Outer Dura mater (thickest)
2. Middle arachnoid mater
3. Inner pia mater
95. Cranial Meningeal Spaces
• Epidural space: Potential space superior to dura.
• Subdural space: Potential space between dura and arachnoid
mater.
• Subarachnoid space: Filled with CSF.Contains the blood
vessels supplying brain
96. Ventricles of Brain
The brain contains hollow spaces called ventricles, which are
filled with CSF. They are extensive.
Lateral ventricle is the largest, extends throughout the cerebrum.
It is between the corpus callosum and the fornix.
Third ventricle Lies medial to the thalamus.
Fourth ventricle is at the base of the cerebellum; it is continuous
with the central canal of the spinal cord, and also with the
subarachnoid space.
Cerebral aqueduct: connects the 3rd and 4th ventricles.
98. CerebroSpinal Fluid (CSF)
CSF is a clear colorless fluid & is actively secreted ( major) ,
ultrafiltration (minor). CSF is formed by
1. Choroid plexus within the ventricles (50-70%)
2. Ependymal cells lining the ventricles
3. Perivascular space in the brain
4. Some of the fluid may originate from the brain substance
Features:
1. Color: Crystal clear
2. Daily secretion: 550ml (0.3ml/min)
3. Volume: 150 ml
4. Specific gravity: 1.003-1.008
5. pH: 7.33
6. Osmolarity: 289 msom/kg H2O
7. Pressure: 50-180 mm of H2O
101. Function of CSF
1. Protective function: In air brain weight =1400 g,
but in its water bath of CSF , brain weight = 50 g, making
it suspended effectively & protects from the shock.
2. Distribution of peptides, hormones, neuroendocrine factors
and other nutrients and essential substances to cells of the
body.
3. Wash away waste products
4. Regulates the volume of the cranial content.
102. Functional part of the brain
Functions of the brain:
• Vision
• Taste
• Cognition
• Emotion
• Speech
• Language
• Hearing
• Motor Cortex
• Sensory Cortex
• Autonomic Functions
105. Frontal Lobe
Name of the area Number of the area Effect of lesion
Primary motor area 4 Contra lateral paralysis
& jacksonian fits
Premotor area 6 Extrapyramidal effect
Motor eye field area 6, 8, 9 Loss of horizontal
conjugate movement of
the eyeball
Pre frontal Cortex 9, 10, 11, 12 Loss of orientation
Brocha’s area 44, 45 Motor aphasia
107. Parietal Lobe
Name of the area Number of the
area
Effect of Lesion
Primary somesthetic
(sensory) area
3, 1, 2 Contralateral sensory
disturbances
Somesthetic Association
Area
5, 7 Contralateral Astereognosis
and sensory neglect
Sensory speech area 40, 39
Taste area 43
109. Temporal lobe
The sensory speech area of Wernicke is localized in the superior
temporal gyrus, with extensions around the posterior end of the
lateral sulcus into the parietal region. The Wernicke area permits
the understanding of the written and spoken language and enables
a person to read a sentence, understand it, and say it out loud.
Name of the area Number of the
area
Effect of Lesion
Primary auditory area 42, 41 bilateral loss of hearing, but
the loss will be greater in the
opposite ear. loss of ability to
locate the source of the sound
Auditory Association Area 22 word deafness (acoustic verbal
agnosia).
111. Occipital lobe
Name of the area Number of the area Lesion
Primary visual area 17 Contralateral Homonymous
hemianopia
Secondary visual area
(Visual association area)
18, 19 loss of ability to
recognize objects seen in the
opposite field of vision
113. Vision
The visual cortex resides in the
occipital lobe of the brain.
Sensory impulses travel from
the eyes via the optic nerve to
the visual cortex. Damage to the
visual cortex can result in
blindness.
116. Hearing
There are two auditory areas of the
brain:
• The primary auditory area
(brown circle) is what detects
sounds that are transmitted from
the ear. It is located in the sensory
cortex.
• The auditory association area
(purple circle) is the part of the
brain that is used to recognize the
sounds as speech, music, or noise.
118. Taste
The gustatory complex (green
circle) is the part of the sensory
cortex (purple area) that is
responsible for taste.
119. Language
Wernicke’s area is a
specialized portion of the
parietal lobe that recognizes
and understands written and
spoken language. Wernicke’s
area surrounds the auditory
association area.
Damage to this part of the
brain can result in someone
hearing speech, but not
understanding it.
120. Emotion
Emotions are an extremely
complex brain function. The
emotional core of the brain is
the limbic system. This is
where senses and awareness
are first processed in the brain.
Mood and personality are
mediated through the
prefrontal cortex. This part of
the brain is the center of
higher cognitive and
emotional functions.
Limbic System
Prefrontal cortex
121. Alzheimer’s disease
Alzheimer’s disease is the most common cause of dementia, but
is rare under the age of 45 years. about 15% of cases are familial.
Pathology:
• macroscopically ,The brain in Alzheimer’s diseas is atrophic.
particularly the cerebral cortex and hippocampus.
• Histologically, presence of senile plaques and neurofibrillary
tangles in the cerebral cortex.
• Histochemical staining demonstrates significant quantities of
amyloid in the plaques.
122. C/F of Alzheimer’s disease
1. The key clinical feature is impairment of the ability to
remember information acquired from the past.
2. Association with disorders of other cortical functions.
3. Short-term and long-term memory are both affected, but
defects in the former are usually more obvious.
4. Later in the course of the disease, typical features are-
- Apraxia
- Visuo spatial impairment
- Aphasia
5. As the disease progresses it is common for patients to deny
that there is anything wrong (anosognosia)
6. Depression is common.
123. References
1. BD Chaurasia's Human
Anatomy. 6th edition.
2. Snell Clinical
Neuroanatomy, 7th
edition
3. Davidson's Principles
and Practice of
Medicine, 23rd edition.
4. Atlas of Human
Anatomy, FH Netter.