[Biology Class Notes] on Human Brain Pdf for EXAM

The human brain is the command centre for the entire nervous system. It works like a computer to process various information that it receives as signals from the other sensory organs in the body and sends messages back to the body.  While the human brain is the same in terms of structure as compared to other mammals, it is larger in terms of body size and better developed.

Weighing between 1-1.5 kg, the human brain is mostly made of neurons. There are anywhere between 86 billion-100 billion neurons in the human brain. The central nervous system is made up of the brain and the spinal cord. Basic functions like body movements, thoughts, emotions and more are controlled by the brain. 

 

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The human brain consists of two types of tissues, gray and white matter. While gray matter makes up the bulk of the brain with various types of cells, white matter is made of axons that are responsible for connecting the various gray matter areas of the brain with each other.

 

Location of the Brain

The human brain is contained inside the skull. The skull comprises 22 bones, of which 8 are cranial bones and the remaining 14 are facial bones. The skull is also responsible for providing frontal, dorsal and lateral protection to the brain. 

The brain is located inside the cranium and surrounded by cerebrospinal fluid, which fills up any hollow space on the brain surface and also circulates within the skull and the spinal cord. Specialized ependymal cells are responsible for producing about 500ml of cerebrospinal fluid every day.

The other functions that the cerebrospinal performs are:

• The CSF (cerebrospinal fluid) acts as a cushion for the brain, lessening the impact of mechanical shocks and other jolts in the process. 

• It is responsible for providing immunological protection to the brain. 

• It provides buoyancy to the brain, almost negating the weight of the brain in its cushion of fluid.

 

Parts of the Human Brain

The human brain consists of various parts that include:

1. The Forebrain

2. The Midbrain

3. The Hindbrain

Each of these parts can be subdivided into various other parts as described below.

1. Forebrain– This refers to a human brain’s anterior part and controls various functions of the human body like temperature, reproduction, hunger, sleep, and emotions. The forebrain includes other parts like:

This is the largest part of the brain which consists of the cerebral cortex of the brain and other subcortical structures. The cerebrum has two cerebral hemispheres. Dense, heavy bands of fiber, commonly known as the corpus callosum join the two cerebral hemispheres together. 

Functions of the cerebrum include memory retention, consciousness, intelligence, thinking, hearing, vision and interpreting touch. 

The cerebrum can be further subdivided into four sections, which are:

• Frontal Lobe- This section is associated with movements, problem-solving abilities, reasoning, planning and various parts of speech.

• Parietal Lobe- This section helps in perceiving stimuli, orientation, and movements. 

• Occipital Lobe- This is involved in visual processing.

• Temporal Lobe- Relates to the recognition of memory, perception of auditory stimuli and speech. 

The cerebrum also possesses an exterior part called the cerebral mantle, commonly known as the cortex. The cerebrum possesses an exterior part called the cerebral mantle, known as the cortex. The cortex has a large surface area since it is convoluted. 

Other areas that are a part of the cerebrum:

• Sensory areas- Help in receiving messages

• Motor areas- Help the voluntary muscles act

• Association areas- Help in connecting the sensory areas with the motor areas. 

This is a part of the forebrain that is located above the brainstem. It is a small structure responsible for conveying sensory information from the various sense organs. It also helps in overall coordination and movement by transmitting motor information. The thalamus is contained within the cerebrum, in the limbic system, which helps in memory retention. 

The hypothalamus is located below the thalamus and is a small yet essential part of the human brain. It is considered as the primary area of the brain performing the following functions:

• The body temperature is regulated by the hypothalamus.

• It receives impulses from various parts of the body.

• Controls the emotional quotient and mood.

• Controls the sense of smell and taste.

• Controls blood pressure, appetite, heart rate, and peristalsis.

2. Midbrain– The midbrain is the central part of the brainstem. It is a fairly small area that consists of the:

The tectum is the dorsal area of the midbrain and makes up for a small portion of the brain. It controls the reflex movements of the neck muscles, eye, and head. All sensory information from the ears to the cerebrum is relayed here. The tectum also acts as a passage for various neurons that move in and out of the cerebrum.

The tegmentum is an area within the brainstem and forms the platform for the midbrain. It connects with the spinal cord, thalamus, and cerebral cortex. It has a complex structure that controls various reflex actions, body movements, sleep, attention and more. 

3. Hindbrain– This is the central area of the human brain. It is composed of three regions that coordinate any process that is essential for survival, which includes motor learning and breathing. The hindbrain is made up of the following:

It is the second-largest part of the brain located in the posterior area of the pons and the medulla. The transverse fissure and the tentorium cerebelli separate the cerebrum and the cerebellum. The outer surface of the cerebellum is the cortex; two hemispheres- the gray cortex on the outer portion and the white medulla inside make up the cerebellum.

The cerebellum also consists of cerebellar nuclei, cerebellar peduncles, and the anterior and posterior lobes. The cerebellum performs important functions like:

•  Transfer of information

• Coordination of eye movement

• Sense of equilibrium

• Controlling the voluntary movements of the body

• Coordination of skeletal movements that are directly related to the anterior and posterior lobes

 

Medulla

The medulla oblongata is in the lowest area of the brain. It is a small structure that controls the body’s autonomic functions like digestion, heartbeat. It also connects the cerebral cortex and the spinal cord and helps control the human body reflexes.

 

Pons

Present between the medulla oblongata and the midbrain, the pons is the most important structure of the brain stem. It relays signals between various parts of the brain including the spinal cord, lower cerebellum, midbrain, and cerebrum.

Some other functions of the pons include:

• Regulating respiration frequency and magnitude

• Controlling the sleep cycle

• Transferring information between the motor cortex and the cerebellum

• Helps in regulating sensations like taste and hearing

 

Conclusion

The human brain is the root of human intelligence. It controls the cognitive abilities of humans, their physiological and psychological functions, and communicates with the various other parts of the human body by sending signals via neurons. Details study materials, worksheets on this topic are available on the Website.