Human Brain

 

The Brain

The brain is one of the larger organs in the human body, with the average adult brain weighing around 1.5 kg.  It is composed of basic, functional units called neurons and the adult human brain contains roughly contains 86 billion.

Human Brain

Parts of the Nervous System

  1. Central Nervous System (CNS): The brain, along with the spinal cord, constitutes the Central Nervous System. It is responsible for thoughts, interpretation and origin of control of body movements.

  2. Peripheral Nervous System (PNS): It includes the nerves and ganglia that are present outside the brain and spinal cord. These radiate through the entire body, from tip to toe. The primary function of the PNS is to connect the CNS with the other parts of the body such as organs, organ systems, limbs and skin.

Where is the Brain located?

The brain is enclosed within the skull, which provides frontal, lateral and dorsal protection. The skull consists of 22 bones, 14 of which forms the facial bones and the remaining 8 forms the cranial bones. Anatomically, the brain is contained within the cranium and is surrounded by the cerebrospinal fluid.

The Cerebrospinal Fluid (CSF) is a fluid that circulates within the skull and spinal cord, filling up hollow spaces on the surface of the brain. Every day, around 500mL of cerebrospinal fluid is produced and about 125 mL is present at any one time.

The primary function of the CSF is to act as a buffer for the brain, cushioning mechanical shocks and dampening minor jolts. The CSF also provides basic immunological protection to the brain.

Furthermore, CSF provides buoyancy for the brain. I.e., the brain is suspended in a layer of CSF, wherein, the weight of the brain is nearly negated. If the brain wasn’t suspended in CSF, it would be impeded by its own weight, consequently cutting off the blood supply in the lower half of the brain. This would lead to the death of neurons in the affected area.

Parts of the Brain

The human brain is composed of three major parts, namely:

  1. Forebrain: It consists –

    • Cerebrum,
    • Hypothalamus
    • Thalamus
  2. Midbrain: Consists of-

    • Tectum
    • Tegmentum
  3. Hindbrain: Is made of-

    • Cerebellum
    • Medulla
    • Pons

Parts of Brain

Cerebrum

The cerebrum is the largest part of the brain which consists of the cerebral cortex and other subcortical structures. It is composed of two cerebral hemispheres that are joined together by heavy dense bands of fibre called the corpus callosum. It is further divided into four sections or lobes:

  1. Frontal lobe: It is associated with parts of speech, planning, reasoning, problem-solving and movement.

  2. Parietal lobe: Helps in movement, the perception of stimuli and orientation.

  3. Occipital lobe: Related to visual processing.

  4. Temporal lobe: Related to perception and recognition of memory, auditory stimuli, and speech.

Generally, the brain consists of two types of tissue named Grey matter and White matter because of their appearance to the naked eye. Grey matter mainly consists of various types of cells, which make up the bulk of the brain. White matter is primarily composed of axons which connect various grey matter areas of the brain with each other.

The exterior portion of the cerebrum is called the cortex or the cerebral mantle. The cortex is extremely convoluted, and as a result, has a large surface area.  The cerebrum also includes:

  1. Sensory areas: To receive the messages.

  2. Association areas: To associate the information with the previous and other sensory information.

  3. Motor areas: Responsible for the action of the voluntary muscles.

The cerebrum is also responsible for thinking, intelligence,  consciousness and memory.

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 relaying 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.

Hypothalamus

The hypothalamus is a small and important part of the brain, located exactly below the thalamus. It is considered the most important region of the brain as it is involved in :

  1. Controlling the mood and emotions.
  2. Receiving the impulses, sense of taste and smell.
  3. Coordinating the messages from the autonomous nervous system.
  4. Synthesizing of body’s essential hormones.
  5. Controlling body temperature, peristalsis, the rate of heartbeat, and blood pressure.
  6. Forming an axis with the pituitary which is the main link between the nervous and the endocrine systems.

Tectum

The tectum is a small portion of the brain, specifically the dorsal part of the midbrain. It serves as a relay centre for the sensory information from the ears to the cerebrum. It also controls the reflex movements of the head, eye and neck muscles. It provides a passage for the different neurons moving in and out of the cerebrum.

Tegmentum

Tegmentum is a region within the brainstem. It is a complex structure with various components. It forms the platform for the midbrain and connects with the thalamus, cerebral cortex, and the spinal cord. It is mainly involved in the movements,  sleep, arousal, attention,  and various basic reflexes.

Cerebellum

The cerebellum is the second largest part of the brain which is located in the posterior portion of the medulla and pons. The cerebellum and cerebrum are separated by tentorium cerebelli and transverse fissure. Cortex is the outer surface of the cerebellum and its parallel ridges are called as the foila. Apart from this, the cerebellum has the cerebellar peduncles, cerebellar nuclei, anterior and posterior lobes, etc. The cerebellum consists of two hemispheres the outer grey cortex and the inner white medulla.  It is mainly responsible for coordinating and maintaining the body balance during walking, running, riding, swimming, and fine control of the voluntary movements. The main functions of the cerebellum include:

  1. It senses equilibrium.
  2. Transfer of information.
  3. Fine control of the voluntary body movements.
  4. The cerebellum is responsible for coordinating eye movements.
  5. It predicts the future position of the body during a particular movement.
  6. The cerebellum is also essential for making fine adjustments to motor actions.
  7. Both anterior and posterior lobes are concerned with skeletal movements.
  8. Coordinating and maintaining body balance and posture during walking, running, riding, swimming, etc.

Medulla Oblongata

The medulla oblongata is a small structure present in the lowest region of the brain.  It essentially controls the body’s autonomic functions such as heartbeat, breathing, digestion, etc. It plays a primary role in connecting the spinal cord, pons and the cerebral cortex. Also, it helps us in maintaining our posture and controlling our reflexes.

More to Read: Difference between heart rate and pulse rate

Pons

The pons is the major structure of the brain stem present between the midbrain and medulla oblongata. It serves as a relay signals between the lower cerebellum, spinal cord, the midbrain, cerebrum and other higher parts of the brain. The main functions of the pons include:

  1. Transferring information between the cerebellum and motor cortex.
  2. Controlling the magnitude and frequency of the respiration.
  3. It is also involved in controlling sleep cycles.
  4. In addition, the pons is involved in sensations such as the sense of taste, hearing, and balance.

Important Questions about the Brain

1. Explain how the nervous system is classified.

The nervous system in humans can be broadly classified into two types, namely:

  • Peripheral Nervous System
  • Central Nervous System

2. Describe the Central Nervous System

The central nervous system essentially consists of the brain and the spinal cord. The system coordinates and controls various aspects of life ranging from physical attributes (heartbeat, breathing) to mental capabilities (memory, intelligence etc).

3. Explain the Peripheral Nervous System

The nerves and ganglia that are present outside the brain and spinal cord contribute to the peripheral nervous system. The primary role of the PNS is to connect the central nervous system to the rest of the body such as the limbs, skin etc.

4. How is the brain protected in the body?

The brain is enclosed within the skull, where it is suspended in a layer of fluid called the cerebrospinal fluid. It protects the brain from minor mechanical shocks and jolts. Furthermore, it also serves minor immunological roles and provides the necessary nutrients required by the brain.

5. Briefly explain the parts of the brain.

Anatomically, the brain consists of the following parts.

  1. Forebrain

    • Cerebrum,
    • Hypothalamus
    • Thalamus
  2. Midbrain

    • Tectum
    • Tegmentum
  3. Hindbrain

    • Cerebellum
    • Medulla
    • Pons

To explore more about the human brain and nervous system, or any other topic, please visit BYJU’S Biology

Further Reading: Spinal Cord

 

 

 

 


Practise This Question

When your finger gets accidentally caught at the door, the pain message is sent to your brain through: