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3. Brain
• It is one of the largest organs in the body, and coordinates most body
activities.
• It is the center for all thought, memory, judgment, and emotion.
• Each part of the brain is responsible for controlling different body functions,
such as temperature regulation and breathing.
4. • The brain is contained in skull & weighs 1300 - 1400 g
• made up of about 1000 billion neurons 7 each neuron is surrounded
by about 10 glial cells (neuroglia ).
• Neurons cannot multiply & many neurons are lost everyday in life but
glial cells can multiply throughout the life.
• Brain is also covered by “Meninges” like spinal cord---outer
duramater, middle arachnoidmater & inner piamater
6. Ventricles of the brain
• There are certain cavities in the brain called as “ventricles”.
• These ventricles are filled with CSF.
• There are 4 ventricles of brain
2 lateral ventricles in two
hemisphere of the brain
3rd lies between
hypothalamus &
thalamus
4th between brain stem
& cerebellum
& is continuous with the
central cavity of spinal
cord
8. Parts of brain:
Cerebrum Cerebellum
Brain
stem
Diencephelon
(1)Medulla
(2)Pons
(3)Mid brain
(1) Thalamus
(2) Hypothalamus
(3) Epithalamus &
Pineal gland
Right
cerebral
hemisphe
re
Left
cerebral
hemisphe
re
10. (A) Cerebrum
• It is the largest section of the brain
• It is located in the upper portion of the brain and is the area that processes
thoughts, judgment, memory, problem solving, and language, imaginations.
• Cerebral cortex – the superficial layer of the cerebrum is “gray mater” & this is
2-4 mm thick called “Cerebral cortex ” contains billions neurons.
• During embryonic development when the brain size increases rapidly, the gray
mater of the cortex enlarges much faster than deeper white mater so as result
cortical region roles & fold upon itself.
11. • The folds are called “gyri” or “convolutions”
• The deepest grooves between the folds are called “fissures”
• The shallower grooves between folds are called “sulci”
• The most prominent fissure, the longitudinal fissure, separates the cerebrum
into right & left halves called “cerebral hemispheres”. Each hemisphere has 4
lobes.
• The cerebrum is subdivided into the left and right Both hemisphere are
connected by a bridge of nerve fibers that relay information between 2
hemisphere called “corpus callosum”
13. • Left hemisphere controls right side of the body
• Right hemisphere controls left side of the body
15. Lobes of Cerebrum
1. Frontal lobe: Most anterior portion of the cerebrum (under forehead)
“central sulcus” separate frontal & perital lobe.
• controls motor function, personality, and speech
• Like Center of reasoning, Planning, some parts of speech, movement, Emotions,
problem solving.
Also called as “motor cortex”
16. •2. Parietal lobe: The most superior portion of the cerebrum(top of head),
• receives and interprets nerve impulses from sensory receptors and interprets
language.
• Receives sensory input from the skin. (touch, pressure, temperature, &
pain)
• Also called as “sensory cortex”
17. •(3) Occipital lobe: The most posterior portion of the cerebrum (back of the
head),
• Receives input from the eyes & controls vision.
• Also called as “visual cortex”.
18. •4. Temporal lobe: The left and right lateral portion of the
cerebrum(on the sides of your head above your ears),
• controls hearing and smell
• Also called “Auditory cortex”
20. Functions of cerebrum:
• (1) Motor functions like control of voluntary movements.
• (2) sensory functions like perception of pain, temparature, touch, hearing, taste,
& smell.
• (3) control of intelligence, speech, memory & learning etc.
21. (B)Cerebellum
• Second largest portion of the brain
• Located beneath the posterior part of the cerebrum
• A deep groove known as “transverse fissure” separates cerebrum to cerebellum.
• Aids in coordinating voluntary body movements and maintaining balance and
equilibrium
22. External Structure
• The external surface , called cerebellar cortex, look like butterfly,
constricted area called “vermis”
• The lateral wings or lobes called cerebellar hemisphere that is
interconnected by a narrow portion called vermis.
Each hemisphere
consists of lobes
separated by deep
fissures.
23. A part of the human brain
that lies in the posterior
cranial fossa , inferior to
occipital lobes.
10% weight of entire brain.
50% of neurons.
24. Divisions & layers of cerebellum
(1) Anterior lobe both regulate subconscious aspects
of skeletal muscle movements
(2) Posterior lobe
(3) Flocculonodular lobe – on the inferior surface maintain equilibrium and
balance
Superficial layer of cerebellum called ”cerebellar cortex” consist of gray mater,
series of slender & parallel folds called “folia”.
Deep to gray mater white mater called “arbor vitae” resemble to branch of
tree.
Even deeper white mater are”cerebellar nuclei”, region of the gray mater
having axons carrying impulses from cerebellum to other parts of brain.
26. Cerebellar peduncles:
Inferior cerebellar
peduncle is a thick rope-like
strand that occupies the upper
part of the posterior district of
the medulla oblongata
Middle cerebellar
peduncles connect the
cerebellum to the pons.
Superior cerebellar
peduncle is a paired
structure that connects the
cerebellum to the midbrain.3 paired Attach the cerebellum to brain
stem
These bundles of white mater consist of
axons that conduct impulses between
the cerebellum & other parts of the
brain
27. Functions of cerebellum:
(1) Coordinate contractions of skeletal muscles
(2) Regulate posture & balance
(3) May play a role in cognition/learning from experieces & language processing
28. (C) Brain Stem
Consists of:
(1) Midbrain
(2) Pons
(3) Medulla oblongata
Superiorly continuous with
Diencephalon
Inferiorly continuous with spinal cord.
Posteriorly pons and medulla is separated by fourth
ventricle.
Midbrain, pons and medulla connected to cerebellum
by superior, middle and inferior cerebellar peduncle
resp.
29. (1)Mid brain
• The midbrain or mesencephalon extends from the
pons to the diencephalon & about 2.5 cm long.
• It acts as a pathway for impulses to be conducted
between the brain and the spinal cord.
• associated with vision, hearing, motor control,
sleep/wake, arousal (alertness), and temperature
regulation.
• Screening of information before it reach high brain
structure
30. Parts of mid brain:
Anterior part called
“cerebral peduncles”
Posterior part called
“Tectum”
Contain 4 rounded
elevations/swellings
2 superior
elevations
Superior
colliculi
2 inferior
elevations
inferior
colliculi
receives input from
the retina and
the visual cortex and
participates in a
variety of visual
reflexes, particularly
the tracking of
objects in the visual
field.
receives auditory
fibres and relay
nucleus of
the thalamus.
TEGMENTUM
SUBSTANTIA
NIGRA
CRUS CEREBRI
Body
movements
Motor
neurons
relay
inhibitory
signals for
unwanted
body
movements
White mater
Function not clear
31. Functions of mid brain:
• The midbrain serves important functions in motor movement, particularly
movements of the eye, and in auditory and visual processing.
• Dopamine produced in the substantia nigra and ventral tegmental area plays a
role in excitation, motivation.
• The midbrain helps to relay information for vision and hearing.
32. (2) Pons:
• means bridge—connects the cerebellum to the rest
of the brain.
• lies between midbrain above and
medulla below in front of cerebellum.
• Like medulla it also sensory tract and motor tract.
• Contains nuclei that deals with
respiration, swallowing, bladder
control, hearing, equilibrium, eye ball
movements, facial expressions etc.
33. (3) Medulla oblongata
• Lowermost part of the brain stem & continuation of the
superior portion of spinal cord.
• Situated at the base of the skull/ starts from foramen
magnum & extends to the inferior border of the pons, a
distance of about 3 cm.
• The ascending & descending sensory & motor white
mater tracts (nerves) connecting brain to spinal cord
pass through medulla oblongata.
34. • Its very important because many “regulatory centers ” are located here
• (1) The cardiovascular center: regulate the heart rate, force of heartbeat &
diameter of blood vessels.
• (2) The medullary rhythmicity center: responsible for maintaining basic rhythm
of breathing.
• (3) The vasomotor center: regulate blood pressure.
• (4) others: vomiting, swallowing, cough, hiccupping & sneezing etc.
• 5 pairs of cranial nerves originates from the nuclei located in medulla oblongata.
37. (1) Thalamus
• Contain mass of nerve cells.
• 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.
• It makes up 80% of diencephalon.
• Important relay station for all Incoming
sensory nerves from periphery/ spinal
Cord with different impulses of pain,
temperature, Touch, pressure are conveyed to thalamus
first than Go to cerebrum.
38. • This information is relayed from thalamus to cerebrum through thalamic nuclei:
(1) Median geniculate nucleus—related to hearing
(2) lateral geniculate nucleus—related to vision
(3) Ventral posterior nucleus—related to taste & somatic sensations like touch,
pain, pressure, cold, heat, vibrations etc.
39. (2) Hypothalamus:
• The hypothalamus sits under the thalamus at the top of the brainstem.
Although the hypothalamus is small, it controls many critical bodily
functions:
• Controls autonomic nervous system
• Center for emotional response and behavior
• Regulates body temperature
• Regulates food intake(appetite)
• Regulates water balance and thirst
• Controls sleep-wake cycles
• Controls endocrine system
• Controls CVS regulation- Heart rate & BP
The hypothalamus is
shaded blue. The pituitary
gland extends from the
hypothalamus.
40. (3) Epithalamus & Pineal gland:
• Epithalamus is a small region superior & posterior to the thalamus.
• It consist of pineal gland
• Pineal gland is about the size of the pea & protrudes from posterior midline of
the 3rd ventricle
• It’s a endocrine gland secrets hormone “Melatonin”.
• Darkness stimulates the pineal gland to secrets melatonin—it promotes
sleepiness.
41. The cranial nerves:
• The 12 pairs of cranial nerves named because they pass through bones of
cranium & arise from the brain inside the cranial cavity.
• These nerves may be sensory(carrying impulse to the brain), motor (carrying
impulse from the brain to periphery) or mixed (containing both sensory & motor
fibers)