Human Brain – Class 11 | Chapter – 21 | Biology Short Notes Series PDF

Human Brain: The human brain is the root of our intelligence. It is the central unit of the human body, responsible for controlling physical functions, physiological processes, and cognitive skills. It regulates almost every element of the human body. The brain processes information coming from all the body parts. It works by sending and receiving messages to various regions of the body via neurons. The human brain has the same fundamental anatomy as most other mammals, but the human brain is bigger in size and more evolved than other mammalian brains. 

The brain is the source of human intelligence. The human brain is mostly made up of neurons, which are the basic building blocks of the brain and nervous system. According to recent estimates, the brain has anywhere from 86 billion to 100 billion neurons. On average, the brain in adult humans weighs between 1.0 kg and 1.5 kg. 

Our brain has two types of tissues :

  • White Matter- White matter is present in the deeper tissues of the human brain. It is made of axons that are the extensions of neurons. White Matter is covered or protected by myelin, which is also responsible for the color of white matter. White matter connects all the grey matter inside the brain.
  • Grey Matter- Grey matter consists of different types of cells. It is majorly present in the outermost layer of the brain. Grey matter is slightly pinkish-grey in color, it surrounds the cerebrum, also known as the cortex of the brain. Grey matter makes up most of the brain and helps in processing and releasing new information.

Diagram of the Human Brain

Human Brain

The brain is surrounded by a skull, which is made up of 22 bones – 14 are facial bones and 8 are cranial bones. The skull protects the brain from the frontal, lateral, and dorsal directions. The brain is confined within the cranium and covered by cerebrospinal fluid.

The Cerebrospinal Fluid or CSF flows through the skull and spinal cord. It fills the empty areas on the brain’s surface. The Cerebrospinal Fluid protects the brain against immunological attacks. It acts as a buffer and protects the brain by cushioning mechanical shocks and neutralizing small jolts.

On average, 500 ml of Cerebrospinal Fluid is produced in a day by the specialized ependymal cells. Cerebrospinal Fluid keeps the brain buoyant. Specifically, the brain is suspended in a layer of CSF, where its weight is almost nullified. If the brain is not suspended in CSF, its weight will restrict its movement, cutting off blood flow to the bottom part of the brain. It would cause neuron death in the afflicted area. 

Parts of Human Brain

The human brain comprises of three parts:

  • Forebrain
  • Midbrain
  • Hindbrain


The largest part of the human brain is termed the forebrain. The forebrain is responsible for controlling emotions, hunger, sleep, body temperature, reproductive body parts, and functions. The forebrain is mainly made of three parts which are mentioned below:

  • Cerebrum
  • Thalamus
  • Hypothalamus


The cerebrum is the brain’s biggest structure. It is made up of the cerebral cortex and subcortical tissues. The cerebrum controls the intellect, thinking process, reasoning, memory, consciousness, translation of touch, vision, and other senses. It consists of two cerebral hemispheres connected by thick, dense bands of fiber known as the corpus callosum. It’s divided into four lobes which are:

  • Temporal Lobe: Temporal Lobe helps in processing sensory inputs, body orientation, and movements.
  • Frontal Lobe: Frontal Lobe is responsible for speech, reasoning, body movements, planning, and problem-solving. 
  • Occipital Lobe: Occipital Lobe controls visual processing, distance perception, object and face recognition, color determination, and memory formation.
  • Parietal Lobe: Parietal Lobe is responsible for the perception of senses, which include taste, touch, smell, etc.

Cerebrum - Lobes of Brain

The cerebrum has an exterior portion, known as the cortex, or the cerebral mantle. The cortex has a huge surface area because it is very convoluted and consists of three parts:

  • Sensory Area– Sensory area is responsible to receive messages.
  • Motor Area– Motor Area controls the action of voluntary muscles.
  • Association Area– Association Area establishes a connection between the Sensory and the Motor Area.


  • Thalamus is a tiny structure just above the brain stem that is in charge of communicating sensory information from the sense organs and sending motor information for movement and synchronization.
  • Thalamus is located within the cerebrum’s limbic system, which is primarily in charge of forming new memories and preserving old events.


Hypothalamus is a tiny and vital part of the human brain, positioned just underneath the thalamus. Hypothalamus is the main region of the brain, it regulates all the important functions of the human body that are mentioned below:

  • It controls the rate of heartbeat, appetite, blood pressure, and peristalsis.
  • It regulates the temperature of the body.
  • It is responsible for controlling the emotion and mood
  • It helps in synthesizing the essential hormones
  • It controls the sense of smell and taste.
  • It receives impulses from body parts. It also communicates messages from the autonomous nervous system.


Midbrain is the central area of the brainstem between the thalamus and hypothalamus and is comparatively smaller in size. Midbrain is mainly made of two parts which are:

  • Tectum
  • Tegmentum


  • The tectum is a tiny part of the brain and refers specifically to the dorsal area of the midbrain. 
  • It sends and receives the sensory information from the ears to the cerebrum and vice versa.
  • The tectum is responsible for the reflex movements of the head, eye, and neck muscles. It serves as a channel for neurons that go in and out of the cerebrum.


  • Tegmentum is located within the brainstem. It connects the midbrain to the cerebral, thalamus, and spinal cord. 
  • It is complex with various components. It is primarily engaged in sleep, bodily motions, attention, arousal, and various other body reflexes.


The hindbrain is the central part of the brain. It regulates all the body functions required for survival like breathing, sleep, heart beating, motor learning, and consciousness. The hindbrain is made of three parts which are mentioned below:

  • Cerebellum
  • Medulla
  • Pons


  • The cerebellum is present in the posterior area of the pons and medulla. The cerebellar tentorium and transverse fissure divide the cerebellum and cerebrum.
  • It is the second biggest region of the human brain. Cerebellum has the cortex as the outer surface and parallel ridges that are known as the folia. 
  • Cerebellum also has cerebellar nuclei, cerebellar peduncles, posterior lobes, and anterior. It is divided into two halves – the outer grey cortex and the inner white medulla.
  • It is in charge of regulating voluntary motions and maintaining bodily equilibrium during walking, cycling, running, and swimming.

Some of the important functions of the Cerebellum are:

  • It sends and receives information.
  • It controls the voluntary movements of the human body.
  • It maintains bodily equilibrium during walking, cycling, running, and swimming.
  • It balances the body by predicting the future position of the body.
  • It also coordinates the movement of the eyes.

Medulla Oblongata

  • The medulla is the tiny structure in the lowest part of the brain. It connects the cerebral cortex, spinal cord, and pons. 
  • It regulates various body functions like breathing, heartbeat, digestion, etc. It also maintains the body posture and control reflexes.


  • Pons is the main part of the brain stem. It lies between the medulla and the midbrain.
  • It transmits signals to and fro from the spinal cord, midbrain, lower cerebellum, cerebrum, and the higher area of the brain. 

Pons perform various important functions such as:

  • It controls respiration.
  • It regulates the sleep cycle.
  • It transmits the information or signals from the cerebellum to the motor cortex and vice versa.

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By Team Learning Mantras