HNS PART IV - PARTS OF BRAIN

Human Nervous System
Dr. Aniket A. Shilwant
Assistant Professor
Dept. of Kriya Sharir
GJP-IASR

Table of Contents
 Brain – Classification, Introduction, Meninges, Ventricles
 Medulla Oblongata
 Pons Varolli
 Midbrain
 Thalamus
 Hypothalamus
 Cerebrum
 Cerebellum
DR. ANIKET A. SHILWANT, GJPIASR 2

CLASSIFICATION OF BRAIN BRAIN
Pros-encephalon
(Fore brain)
Tel-encephalon
Cerebrum
Lateral ventricles
Di-encephalon
Thalamus
Hypothalamus
Mes-encephalon
(Mid brain)
Rhomb-encephalon
(Hind brain)
Met - encephalon
Pons V
Cerebellum
IV Ventricles
Myel - encephalon
Medulla O
IV Ventricles

Introduction to Brain
 Embryological development – 4th Week of IUL
 Ectodermal in origin from Neural tube.
 One of the largest organs of human body
 Weight – 1300 – 1350gms
 Shape – Walnut or Mushroom shaped
 Main divisions – 4parts
• Cerebrum
• Di-encephalon
• Brain stem
• Cerebellum

Brain Coverings & Spaces
 Meninges
 Duramater -2layers.
 Outermost Periosteal layer.
 Inner Meningeal layer.
 Arachnoid mater
 Piamater

SUBDURAL SPACE
 BONE LAYER OF SKULL
 DURA MATER
 DURA MATER
 ARACHNOID MATER
 ARACHNOID MATER
 PIA MATER
SUBARACHNOID SPACE
EPIDURAL SPACE
Brain Coverings & Spaces

Ventricles in Brain
 Hollow spaces or cavities in brain connecting each other
 Continuation with central canal along the Spinal cord
 2 Lateral ventricles – Below Corpus Callosum within Cerebral
Hemispheres
 IIIrd Ventricles – Between Lateral V, inferior to right & left half of
Thalamus
 IVth Ventricles – Between Cerebellum & Inferior part of Brain
 Lateral V & IIIrd V – Connected by an Oval opening – Foramen
of Monro (Inter Ventricular Foramen)
 IIIrd V & IVth V – Cerebral Aqueduct or Aqueduct of Slyveius

 Upper portion of spinal cord & Inferior part of brain stem.
 Location:- Just superior to the level of Foramen Magnum.
 It contains all ascending and descending tracts that cross each other
which communicates the spinal cord and various parts of brain.
 Ventrally there are two rough triangular structures c/a- Pyramids.
 Pyramids are composed of largest motor tracts from cerebral cortex -
spinal cord.
 Crossing of fibres in pyramids - Decussation of Pyramids.
 Dorsal side of medulla 2pairs of nuclei - Nucleus Gracilis and Nucleus
Cuneatus. These receives information from opposite side and conveys to
Thalamus.
Medulla Oblongata

Medulla Oblongata

Vital centre –
i. Cardiac centre-Regulates cardiac beat and force of contraction.
ii. Medullary rhythmicity area-Maintains basic rhythm of breathing.
iii. Vasomotor area-Regulates dimension of blood vessels.
Cranial nerve centre (VIII-XII) –
i. Vestibulo-cochlear nerve(VIII)- Hearing, Equilibrium & posture balance.
ii. Glossopharyngeal nerve(IX)-Swallowing, Salivation, Taste perception.
iii. Vagus nerve(X)- Maintains activity of Thoracic & Abdominal viscera.
iv. Spinal accessory nerve (XI)-Head & Shoulder movements.
v. Hypoglossal nerve(XII)- Swallowing, Tongue movements, Articulation of
speech.
Functions of Medulla Oblongata

Vital reflex actions –
• Coughing reflex
• Sucking reflex
• Sneezing
• Vomiting reflex
• Salivation
• Swallowing reflex
• Hiccupping
Functions of Medulla Oblongata

Location:- Anterior to cerebellum and above medulla.
 It consists of white fibres scattered throughout along with
nuclei.
 Fibres go along two principal directions –
i. Transverse-connect with cerebellum.
ii. Longitudinal-connect spinal cord/medulla with upper
parts of brain.
Pons Varolii

Vital centres –
a) Pneumotaxic area
b) Apneustic area – Both controls, initiates respiratory
cycle.
Cranial nerve centres- (V-VIII) –
a)Trigeminal nerve(V)-Head, Face, Eyes and Jaws
movement
b)Abducens nerve(VI)- Lateral eyeball movements
c)Facial nerve(VII)-Taste perceptions, Salivation, Facial
expressions.
d)Vestibulocochlear nerve(VIII)-Equilibrium & posture
balance, hearing.
Functions of Pons Varolii

 Location:- It extends from lower portion of diencephalon to pons
 Cerebral aqueduct passes through midbrain connecting third and fourth
ventricles.
 Ventrally - pair of fibre bundles c/a- Cerebral peduncles.
 Peduncles contain-
 Motor fibres (cerebral cortex to pons and spinal cord)
 Sensory fibres (pass from spinal cord to thalamus)
 Dorsally - c/a- Tectum.
 It contains 4round prominences c/a- Corpora Quadrigemina.
 2 Superior colliculi-Reflex centres for eyeball movements(optic)
 2 Inferior colliculi- Reflex centres for movements of head and
trunk in response to auditory stimuli.(Auditory)
Mid Brain

 Substantia Nigra- A large pigmented nucleus. Largest nucleus in
Midbrain.
 Red nucleus -Termination of fibres from cerebral cortex and
cerebellum.
 The neurons of Substantia Nigra and Red nucleus secretes a
neurotransmitter-Dopamine. (Parkinsons Disease, Schizophrenia)
 Dopamine plays an important role in motor as well as cognition
functions of body.
 Medial Leminiscus - Band of white fibres i.e. axons conveying
impulses for touch and vibration.
Mid Brain

 Regulates the movements of eyeballs and head in response to visual
stimuli.
 It has also the reflex centres regulating the movements of head and
trunk in response to auditory stimuli.
 The medial leminiscus within midbrain conveys impulses about fine
touch, vibrations from medulla to the thalamus.
 Substania Nigra – Reward seeking center, Production of NT
 Red Nucleus – Hb & Ferritin form, Descending tracts (Rubrospinal
tracts), Righting reflex, Muscle tone
 Cranial nerve centres-
• Occulomotor nerve (III) - Eyeballs & Pupils size.
• Trochlear nerve (IV) - Eyeball movements.
Functions of Mid Brain

 Bilateral oval structures shares majority of Di-encephalon
 Nearly 3cm in length.
 Location:- Just above the brain stem.
 Classification of Nuclear centres –
 Anatomical
 Physiological
Thalamus

Classification of Nuclear centres –
Anatomical
 Midline nuclei
 Intra-laminar nuclei
 Medial mass of nuclei
 Lateral mass of nuclei
 Posterior group of nuclei.
Thalamic Reticular Nucleus
Thalamus

Thalamus

Thalamus
Sr. No Group of Nuclei Nuclei Functions
1 Specific sensory
relay nuclei
Ventral posterior nucleus
Medical geniculate body
Lateral geniculate body
Sends Sensory signals to Cerebral Sensory
cortex
2 Specific motor
nuclei
Ventral anterior nucleus
Ventral lateral nucleus
Receives from Cerebellum & sends Sensory
signals to Cerebral Motor cortex
3 Association or less
specific nuclei
Dorsolateral nucleus
Posterolateral nucleus
Pulvinar Nucleus
To Association Areas
4 Non-specific nuclei Midline nuclei
Intralaminar nuclei
Reticular nucleus
Connects Reticular formation,
Hypothalamus, Cerebral cortex to Cerebral
Cortex
5 Limbic system
nuclei.
Anterior nucleus
Dorsolateral nucleus
Limbic cortex – Hypothalamus, Mamillary
bodies, Cingulate gyrus
Physiological

Physiological
Thalamus

Thalamic Radiations

 Collection of nerve fibers connecting thalamus and cerebral cortex
 Contains - Thalamocortical and Corticothalamic fibers
 All fibers pass through internal capsule.
 Divided into four groups, called as thalamic peduncles or thalamic stalks.
 Anterior (frontal) thalamic peduncle or radiation
 Superior (centroparietal) thalamic peduncle or radiation
 Posterior (occipital) thalamic peduncle or radiation
 Inferior (temporal) thalamic peduncle or radiation
Thalamic Radiations

Functions of Thalamus
 RELAY CENTER
 CENTER FOR PROCESSING OF SENSORY INFORMATION - Functional Gateway for Cerebral
Cortex
 CENTER FOR DETERMINING QUALITY OF SENSATIONS
i. Discriminative Nature ii. Affective Nature
 CENTER FOR SEXUAL SENSATIONS
 ROLE IN AROUSAL AND ALERTNESS REACTIONS
 CENTER FOR REFLEX ACTIVITY
 CENTER FOR INTEGRATION OF MOTOR ACTIVITY
 MEDIAL GENICULATE NUCLEI (HEARING)
 LATERAL GENICULATE NUCLEI (VISION)
 VENTRAL POSTERIOR NUCLEI (GENERAL SENSATIONS & TASTE)
 VENTRAL ANTERIOR AND LATERAL NUCLEI (VOLUNTARY MOTOR ACTIONS)

Thalamic Syndrome:- Blockage – Ischemia – Infarction
1) Anaesthesia
2) Astereognosis
3) Ataxia
4) Anosognosia
5) Hyperalgesia – Medial Mass Nuclei (Limbic cortex)
6) Thalamic phantom limb – Feeling of limb missing (Gender
transform surgery, Amputation of limbs)
7) Chorea – Quick, Jerky movements
8) Athetosis – Involuntary muscle twitching, twisting, folding
Applied Physiology of Thalamus

Hypothalamus
 Just near base of IIIrd ventricles
 Extends from Optic chiasma to Mamillary body
 Groups of Nuclei
 Anterior / Preoptic Group
 Middle / Tuberal Group
 Posterior / Mamillary group

Hypothalamus

 It controls and regulates the Autonomic Nervous System
 It is mediator between Nervous and Endocrine system.
 Regulates Posterior Pituitary by Secretion of –
 Oxytocin
 Anti diuretic Hormone (ADH)
 It regulates Anterior Pituitary –
 Growth hormone releasing hormone (GHRH)
 Growth hormone releasing polypeptide (GHRP)
 Growth hormone inhibiting hormone (GHIH)
 Corticotropin releasing hormone (CRH)
 Prolactin inhibiting hormone (PIH)
 Gonadotropin releasing hormone (GnRH)
Functions of Hypothalamus

 REGULATION OF HEART RATE – Vasomotor Center
 REGULATION OF BLOOD PRESSURE – Vasomotor Center
 REGULATION OF BODY TEMPERATURE
 Sets normal physiological thermostat conditions (37°C)
 Heat loss center
 Heat gain center
 REGULATION OF HUNGER AND FOOD INTAKE
 Feeding center
 Satiety center
Applied – Hyperphagia, Anorexia, Hypothalamic Obesity

 REGULATION OF HUNGER AND FOOD INTAKE MECHANISM
 Glucostatic – Glucostats
In Hyperglycemia, failure in stimulation of Satiety center.
 Lipostatic – Leptin (Adipocytes) – Crossing BBB – Inhibits Feeding center
 Peptide – Stimulates & or Inhibits feeding center
Stimulation – Ghrelin, Neuropeptide Y
Inhibition – Leptin, Peptide YY
 Thermostatic
 Hormonal
Stimulation – Insulin
Inhibition – Glucagon, Somatostatin, Pancreatic Polypetide

 WATER BALANCE
 Thirst mechanism- Activation of Osmoreceptors in Hypothalamus
 ADH mechanism- Facultative reabsorption of water
 REGULATION OF SLEEP AND WAKEFULNESS
 REGULATION OF CIRCADIAN RHYTHMS
 ROLE IN BEHAVIOR AND EMOTIONAL CHANGES
 Reward & Punishment Center
 Rage
 REGULATION OF SEXUAL BEHAVIOUR
 ROLE IN OLFACTION

Hypothalamus

 Maximum part of brain and is supported on the brain
stem.
 During embryonic development there is rapid increase
in brain size.
 Nerve cell bodies inside cortex enlarges out of
proportion then the cortical region rolls and folds upon
itself.
 Folds - GYRI or CONVOLUTIONS .
 Deep grooves between folds - FISSURES.
 Shallow grooves between folds - SULCI.
 Both hemispheres are connected to each other by a
large bundle of transverse fibres of white matter called
as - CORPUS CALLOSUM.
Introduction to Cerebrum
DR. ANIKET A. SHILWANT, GJPIASR
34

Longitudinal fissure
Lateral or
Sylvian
fissure
Gyri
&
sulci
Cerebrum
Longitudinal Fissures -
Left and Right Cerebral
Hemispheres.
Transverse Fissures -
Cerebrum and Cerebellum.
Falx Cerebri
Tentorium Cerebri

 Cerebral cortex arranged in 6layers of cells
which gets rolled on each other as it develops.
 Six layers from outer to inner side -
1) Molecular or Plexiform layer
2) External granular layer
3) External pyramidal layer
4) Internal granular layer
5) Internal pyramidal layer or Ganglionic layer
6) Fusiform layer
 Cerebrum classification –
1) Neocortex / Neopallium
2) Allocortex - Archicortex & Paleocortex
Cerebrum

1. Frontal lobe
2. Parietal lobe
3. Temporal lobe
4. Occipital lobe
5. Insula
Lobes of Cerebrum
Central Sulcus
Lateral Cerebral Sulcus
Parieto-Occipital Sulcus

1) Association Fibers.
2) Commisural Fibers.
3) Projection Fibers.
intracortical
intercortical
projection fibers
White Mater of Cerebrum

Projection Fibers

 Anterior Commissure
 Posterior Commissure
 Habenular Commissure
 Corpus Callosum
Commissural Fibers

 Short fibers – connect adjacent gyri
 Long fibers
 Superior longitudinal fasciculus
 Arcuate fasciculus
 Inferior longitudinal fasciculus
 Cingulum – septal area, cingulate and
para-hippocampal gyri
 Uncinate fasciculus – orbital frontal gyri
to temporal pole
Association Fibers

 Cerebral dominance is defined as the dominance of one cerebral hemisphere
over the other in the control of cerebral functions.
 Both the cerebral hemispheres are not functionally equivalent.
 Some functional asymmetries are well known.
CEREBRAL DOMINANCE AND HANDEDNESS
 Cerebral dominance is related to handedness.
 Dominant Cerebral Hemisphere – Analytical, critical thinking, cognitive,
linguistic functions
 Speech, reading, writing, response, expression, intellect, etc.
 More than 90% of people are right handed.
Cerebral dominance

 Dominant Hemipshere – Categorical Hemisphere
 Non-Dominant Hemisphere – Representational Hemishphere
Lesion in –
 Dominant hemisphere – Linguistic, cognitive disorders
 Representational hemisphere – Astereognosis, technical specifications –
visuospatial, direction defining, recognition of tones, artistic defects, etc.
Cerebral dominance

1
2
3 5
7
4
4s
6a
6b
44 45
8
41 42
22
17
18
18
19
19
9
10
11 39
w
43

Functions of Cerebrum

1) General sensory area / Somesthetic Area
a) Area No.:- 1,2,3
b) Location:- Just posterior to central sulcus or in post central gyrus
c) Function / Importance :-
a) Receives sensations from cutaneous and visceral receptors throughout body.
b) Cutaneous – Touch, Pain, Pressure, Temperature
c) Activates lower motor neurons of spinal cord
d) Proprioceptors
e) Discriminative sensations – Spatial recognition, Intensity of stimulus, similarities &
differences between stimulus.
Effect of Lesion –
a) When damaged with Thalamus – complete Anaesthesia
b) Lesion only in Somesthetic Area – perception of sensation is present but there is loss of
discriminative functions
Sensory Areas

2) Somesthetic Association Area
a)Area No.:- 5, 7
b)Location:- Posterior to Somesthetic Area
Integrates and interprets sensations.
Helps to store memories of past sensory experiences.
Plays role in Stereognosis
3) Primary Visual Area
a) Area No.:- 17
b) Location:- Occipital Lobe
c) Function / Importance:-
 It receives sensory visual impulses from eyes & interprets shape, size
&colour
Effect of lesion – Blindness
Sensory Areas

4) Visual Association Area
a)Area No.:- 18, 19 (Occipital Eyefield Area)
b)Location:- Occipital Lobe
Receives sensation from Primary visual area, Thalamus, Midbrain and interprets
visual impulses.
It helps to recall past visual experiences and recognises what is seen.
5) Primary Auditory Area
a) Area No.:- 41, 42
b) Location:- Superior Temporal lobe near lateral cerebral sulcus.
 It interprets characteristics of sound - pitch, rhythm, intensity & source of sound
 Receives auditory sensation
Effect of lesion - Deafness
Sensory Areas

6) Auditory Association Area
a)Area No.:- 22
b)Location:- Inferior to primary auditory area in temporal cortex
Determines whether sound is speech, noise or music.
It also interprets meaning of speech by translation of words into thoughts.
It works along with Primary Auditory Area & Wernicke’s Area
7) Primary Gustatory Area
a) Area No.:- 43
b) Location:- Above lateral cerebral sulcus in Parietal Cortex
 It perceives sense of taste sensation.
Effect of lesion – Ageusia
Sensory Areas

8) Primary Olfactory Area
a)Area No.:- 28
b)Location:- Temporal lobe
It interprets sense of smell sensation.
Effect of lesion – Anosmia
9) Gnostic Area
a) Area No.:- 5, 7 (Somesthetic Asso. Area) 39, 40 (Area of Understanding)
b) Location:- In between visual-auditory association and somesthetic areas
 It is a common integrative area
 It receives and collects sensory impulses from various areas and a common thought is
formed.
Sensory Areas

10) Wernicke Area
a) Area No.:- 22 (Auditory Asso. Area); 39, 40 (Area of Understanding)
b) Location:- Left temporal & parietal lobe
 It is a posterior language understanding area
 Translates words into thoughts
 Interprets & analyses the character of sound.
Sensory Areas

1) Primary Motor Area
a)Area No.:- 4, 4s
b)Location:- In precentral gyrus of frontal lobe
It controls group of specific muscles
It forms pyramidal tracts
Initiates voluntary movements and speech
Activates lower motor neurons of spinal cord
4s – Suppressor area. Supresses or prevents exaggerated motor
movements
Effect of lesion – Hemiplegia & Spastic paralysis
Motor Areas
Motor Areas

2) Premotor Area
a) Area No.:- 6 (6a & 6b)
b) Location:- Anterior to primary motor area
 It controls learned motor activities
 It controls group of specific muscles to perform a activity in a sequence
pattern
E.g.. Rotation of eyes, head, trunk
 It also regulates skilled movements. E.g.. Writing, holding a pen
 It also controls the grasping reflexes
 6a – Generalised pattern of movements (rotation of eyes, head, trunk)
 6b – Complex coordinated movements (face, buccal cavity, larynx and
pharyngeal movements)
Motor Areas

3) Frontal Eyefield Area
a) Area No.:- 8
b) Location:- Frontal cortex
 It plays a role in conjugate movements of eyes
 Controls the voluntary scanning movements. E.g.. Searching a word in dictionary
Effect of lesion – Squint, Astigmatism
4) Broca’s Area
a) Area No.:- 44, 45
b) Location:- Superior to lateral cerebral sulcus in frontal lobe
 It is active in left cerebral hemisphere of right handed persons & vice versa
 It translates thought into speech
 Dominant Hemisphere*
Effect of lesion – Aphasia
Motor Areas

Association Area / Silent Area
a) Area No.:- 9, 10, 11 12, 13, 14, 23, 24, 29, 32
b) Location:- Prefrontal area
 Connects sensory & motor areas
 Concerned with-
i. Memory
ii. Emotions
iii. Reasoning, Aptitude
iv. Intelligence
v. Judgement
vi. Personality traits
vii. Will Power, Decision Power & Planned actions
Association Areas

Morphological distribution of Cerebral Areas
Frontal Lobe – Precentral & Prefrontal lobe
Precentral – Primary motor (4), Pre motor areas (6,8,44,45)
Prefrontal lobe –
9, 10, 11 – Laterally
12, 13, 14, 23, 24, 29 and 32 – Medially
Parietal Lobe – Post central gyrus (1,2,3 & 5,7)
Temporal Lobe – Auditory (41,42 & 22)
Occipital Lobe – Visual (17,18,19)

Sensory and Motor Areas of the Cerebral Cortex

•Areas 3, 1 & 2 – Primary Somatosensory Cortex (frequently referred
to as Areas 3, 1, 2 by convention)
•Area 4 – Primary Motor Cortex
•Area 5 – Somatosensory Association Cortex
•Area 6 – Premotor cortex and Supplementary Motor Cortex
(Secondary Motor Cortex) (Supplementary motor area)
•Area 7 – Somatosensory Association Cortex
•Area 8 – Includes Frontal eye fields
•Area 9 – Dorsolateral prefrontal cortex
•Area 10 – Anterior prefrontal cortex (most rostral part of superior
and middle frontal gyri)
Broadman’s Classification of Cerebrum

•Area 11 – Orbitofrontal area (orbital and rectus gyri, plus part of the
rostral part of the superior frontal gyrus)
•Area 12 – Orbitofrontal area (used to be part of BA11, refers to the
area between the superior frontal gyrus and the inferior rostral
sulcus)
•Area 13 and Area 14* – Insular cortex
•Area 15* – Anterior Temporal Lobe
•Area 16 – Insular cortex
•Area 17 – Primary visual cortex (V1)
•Area 18 – Secondary visual cortex (V2)
•Area 19 – Associative visual cortex (V3,V4,V5)
•Area 20 – Inferior temporal gyrus

•Area 21 – Middle temporal gyrus
•Area 22 – Superior temporal gyrus, of which the caudal part is
usually considered to contain the Wernicke's area
•Area 23 – Ventral posterior cingulate cortex
•Area 24 – Ventral anterior cingulate cortex.
•Area 25 – Subgenual area (part of Ventromedial prefrontal cortex)
•Area 26 – Ectosplenial portion of the retrosplenial region of the
cerebral cortex
•Area 27 – Piriform cortex
•Area 28 – Ventral entorhinal cortex
•Area 29 – Retrosplenial cingulate cortex
•Area 30 – Part of cingulate cortex

•Area 31 – Dorsal Posterior cingulate cortex
•Area 32 – Dorsal anterior cingulate cortex
•Area 33 – Part of anterior cingulate cortex
•Area 34 – Dorsal entorhinal cortex (on the Parahippocampal gyrus)
•Area 35 – Perirhinal cortex (in the rhinal sulcus)
•Area 36 – Ectorhinal area, now part of the perirhinal cortex (in the
rhinal sulcus)
•Area 37 – Fusiform gyrus
•Area 38 – Temporopolar area (most rostral part of the superior and
middle temporal gyri)
•Area 39 – Angular gyrus, considered by some to be part of Wernicke's
area
•Area 40 – Supramarginal gyrus considered by some to be part of
Wernicke's area

•Area 40 – Supramarginal gyrus considered by some to be part of Wernicke's area
•Areas 41, 42 – Auditory cortex
•Area 43 – Primary gustatory cortex
•Area 44 – Pars opercularis, part of the inferior frontal gyrus and part of Broca's
area
•Area 45 – Pars triangularis, part of the inferior frontal gyrus and part of Broca's
area
•Area 46 – Dorsolateral prefrontal cortex
•Area 47 – Pars orbitalis, part of the inferior frontal gyrus
•Area 48 – Retrosubicular area (small part of medial surface of the temporal lobe)
•Area 49 – Parasubicular area in a rodent
•Area 52 – Parainsular area (at the junction of the temporal lobe and the insula)

Thank You All !!!
Dr. Aniket A. Shilwant
Assistant Professor
Department of Kriya Sharir
GJP-IASR
Email –
ayuraniket18@gmail.com
http://ayugjac.edu.in/Staff_CV.aspx?dl=dn3Mja19480dn3Mja19
http://scholar.google.co.in/citations?user=636K2sMAAAAJ&hl=en
https://www.researchgate.net/profile/Aniket_Shilwant
64

HNS PART IV - PARTS OF BRAIN

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