The central nervous system (CNS) consists of the brain and spinal cord. The brain is protected by membranes, bones, and cerebrospinal fluid. It contains neurons and is divided into the forebrain, midbrain, and hindbrain. The forebrain controls functions like emotions and memory. The spinal cord extends from the brain down the back and connects to all parts of the body, controlling movement and carrying sensory information. It is divided into cervical, thoracic, and lumbar regions.

1. Central nervous system
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2. Central Nervous System
Our bodies couldn’t operate without the nervous system - the
complex network that coordinates our actions, reflexes, and
sensations. Broadly speaking, the nervous system is organised into
two main parts,
 The central nervous system (CNS)
 The peripheral nervous system (PNS)
The CNS is the processing centre of the body and consists of the
brain and the spinal cord. Both of these are protected by three layers
of membranes known as meninges. For further protection, the brain
is encased within the hard bones of the skull, while the spinal cord is
protected with the bony vertebrae of our backbones. A third form of
protection is cerebrospinal fluid, which provides a buffer that limits
impact between the brain and skull or between spinal cord and
vertebrae.

3. The Human Brain
On average, an adult brain weighs between 1.0 kg – 1.5
kg. It is mainly composed of neurons – the fundamental
unit of the brain and nervous system. Recent estimates have
suggested that the brain contains anywhere between 86
billion to 100 billion neurons.
The brain, along with the spinal cord, constitutes the
central nervous system. It is responsible for thoughts,
interpretation and origin of control for body movements.
Fact: The average brain weight of the adult male was 1336 gr; for
the adult female 1198 gr. With increasing age, brain weight
decreases by 2.7 gr in males, and by 2.2 gr in females per year

4. Brain Diagram
The brain diagram given below highlights the
different lobes of the human brain.

5. Parts of Brain
Following are the major parts of the human brain:
Forebrain – Largest part of the brain
It is the anterior part of the brain. The forebrain parts include:
• Cerebrum
• Hypothalamus
• Thalamus
Forebrain Function:
Controls the reproductive functions, body temperature, emotions, hunger
and sleep.
Fact:
The largest among the forebrain parts is the cerebrum. It is also the largest
part of all vertebrate brains.

6.  Cerebrum
I. Topmost and largest part.
II. Right cerebrum hemisphere,Left cerebrum hemisphere
III. Controls action like thinking, feelings, emotions, seeing, hearing,
perceptions, memory, speech, decision making, etc.
 The cerebrum is further divided into four sections or lobes:
1. Frontal lobe: It is associated with parts of speech, planning,
reasoning, problem-solving and movements.
2. Parietal lobe: Help in movements, the perception of stimuli and
orientation.
3. Occipital lobe: It is related to visual processing.
4. Temporal lobe: This region is related to perception and
recognition of memory, auditory stimuli and speech.

7.  Thalamus
The thalamus is a small structure, located right above the brain stem
responsible for relaying sensory information from the sense organs.
It is also responsible for transmitting motor information for
movement and coordination. Thalamus is found in the limbic
system within the cerebrum. This limbic system is
mainly responsible for the formation of new memories and storing
past experiences
I. Inside cerebrum small structure called thalamus.
II. It controls many sensory functions.

8.  Hypothalamus
I. Hypothalamus lies at the base of thalamus.
II. It controls body temperature, hunger and thirst.
III. The hypothalamus is a small and essential part of the brain
IV. It is considered the primary region of the brain
V. Receives impulses
VI. Regulates body temperature
VII. Controls the mood and emotions
VIII. Controls the sense of taste and smell
IX. Synthesises the body’s essential hormones
Coordinates the messages from the autonomous nervous system.Controls appetite,
peristalsis, the rate of heartbeat, and blood pressure.Forms an axis with the pituitary gland
which is the main link between the nervous and the endocrine systems

9. Midbrain: Smallest and central part of the brain
Midbrain is a smaller part of brain which is present below the cerebrum.
It receives information from sense organs which is then passed on
appropriate part of brain.
The midbrain consists of:
• Tectum
• Tegmentum

10.  Tectum
The tectum (Latin for roof) is the dorsal sideof the midbrain. The
position of the tectum is contrasted with the tegmentum, which
refers to the region in front of the ventricular system, or floor of the
midbrain. It is involved in certain reflexes in response to visual or
auditory stimuli.
 Tegmentum
The tegmentum is the ventral part of the midbrain and the tectum
is the dorsal part of the midbrain. It is located between the
ventricular system and distinctive basal or ventral structures at each
level. It forms the floor of the midbrain (mesencephalon) whereas
the tectum forms the ceiling.

11. Hindbrain: The lower part of the brain
 The hindbrain is composed of:
• Cerebellum
• Medulla oblongata
• Pons
 Hindbrain functions: The three regions of the hindbrain
coordinates all processes necessary for survival. These induce
breathing, heartbeat, sleep, wakefulness and motor learning.

12.  Cerebullum
1. Lies under the back part of cerebrum.
2. It controls the bodybalance and movements.
 Pons
1. It is an oval structure present beneath the midbrain.
2. It controls sleep, swallowing, equilibrium and taste
 Medulla oblongata
1. It forms the posterior part of brain where it is connected with the
spinal cord.
2. It controls heartbeat,breathing and digestion etc.
3. It keeps on working when rest of the brain goes to sleep.

13. Spinal cord
 Spinal cord is an extension of medulla oblongata. It runs
backwards in side the backbone up to its lower end. It is also
made up of inter-neurons.Spinal cord create a link between brain
and different body parts. It also controls some reflex actions and
some other involuntary actions.

14. Purpose of the spinal cord
 Control body movements and functions. Signals from your
brain to other body parts control your movements. They also
direct autonomic (involuntary) functions like your breathing rate
and heartbeat, as well as bowel and bladder function.
 Report senses to your brain. Signals from other parts of your
body help your brain record and process sensations like pressure
or pain.
 Manage your reflexes. Your spinal cord controls some reflexes
(involuntary movements) without involving your brain. For
example, your spinal cord manages your patellar reflex
(involuntarily moving your leg when someone taps your shin in a
certain spot)

15. The main parts of the spinal cord
 Your spinal cord has three main parts:
 Cervical (neck).
 Thoracic (chest).
 Lumbar (lower back).

16. Cervical
 Our cervical spine — the neck area of our spine — consists of seven
stacked bones called vertebrae. The first two vertebrae of our cervical
spine are unique in shape and function. Our first vertebra (C1), also
called the atlas, is a ring-shaped bone that begins at the base of your
skull. It’s named after Atlas, of Greek mythology, who held the world
on his shoulders. The atlas holds our head upright. Our second vertebra
(C2), also called the axis, allows the atlas to pivot against it for the side-
to-side “no” rotation of your head.
 Protecting your spinal cord.
 Supporting your head and allowing movement.
 Providing a safe passageway for vertebral arteries.

17. Thoracic
 The thoracic spine is located in the upper and middle part of the
back. Twelve vertebrae are located in the thoracic spine and are
numbered T-1 to T-12. Each number corresponds with the nerves
in that section of the spinal cord:
 T-1 through T-5 nerves affect muscles, upper chest, mid-back
and abdominal muscles. These nerves and muscles help control
the rib cage, lungs, diaphragm and muscles that help us breathe.
 T-6 through T-12 nerves affect abdominal and back muscles.
These nerves and muscles are important for balance and posture,
and they help you cough or expel foreign matter from your
airway.

18. Lumbar
 Compared with other spine vertebrae, your lumbar vertebrae are
larger, thicker and more block-like bones. Your lumbar vertebrae
provide stability for your back and spinal column and allow for a
point of attachment for many muscles and ligaments. Your lumbar
vertebrae support most of your body’s weight. It’s also the center
of your body’s balance. Your lumbar spine and the muscle and
ligaments that attach to them allow you to walk, run, sit, lift and
move your body in all directions.
 Supports your upper body, distributes body weight.
 Moves your body.
 Protects your spinal cord and cauda equina.
 Controls leg movement.