Anatomy & physiology of BRAIN

1. The Anatomy and Physiology of
Brain Sarita Sharma
Assistant professor
of pharmacology
Mumbai

2. Organs
CNS:
 Brain
 Spinal Cord
PNS:
 Nerves

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

5. Cerebrum
cerebellum

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
hemisph
ere
Left
cerebral
hemisph
ere

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

14. Lobes of Cerebrum

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.

25. Flocculonod
ular lobe
folia

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 exten
ds 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
SUBSTANTI
A NIGRA
CRUS CEREBRI
Body
movement
s
Motor
neurons
relay
inhibitory
signals for
unwanted
body
movement
s
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.

35. (D)Diencephelon

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)

44. Thank you