Cerebrum and Cerebellum, Practice Problems and FAQs

We are the most intelligent animal in the whole world. Do you know what makes us more intelligent? The ability for reasoning, communication, and environment manipulation is making us different from other animals. So which part of our body is helping us to do all these things? Obviously the brain!!

Human brain

Human brains are well advanced and it is efficient enough to generate ideas which can change the colour of the world. All the great inventions like the internet, the electrical gadgets and even a technique of lock and key came from some great human brains. Human brains are the part of the central nervous system which is the processing centre of the body.

Fig: Central nervous system

All the functions of our body such as movement, senses etc., are controlled by the brain. But some of our actions are voluntary and some are not. Both the voluntary and involuntary actions are controlled by the different parts of the brain. The part of the brain which controls the voluntary actions include cerebrum and cerebellum. The part which controls the involuntary actions includes the brain stem. Cerebrum and cerebellum have different structure and function. So in this article we are going to discuss more about cerebrum and cerebellum.

Table of contents

• Human brain
• Cerebrum
• Cerebellum
• Differences between cerebrum and cerebellum
• Practice Problems
• FAQs

Human brain

Brain is an important organ in the human body which is a part of the central nervous system (CNS). It is made up of 100 billion neurons. The brain acts as the centre for command and control in the human body and it is also called an encephalon. It is the major information processing unit and is situated in the cranial cavity of the skull which gives the protection.

Fig: Brain within the skull

Protective covering of the brain

The human brain is covered by three protective coverings called meninges. It includes dura mater, arachnoid membrane and pia mater.

Fig: Cranial meninges

Parts of the brain

The brain can be divided into three parts as follows:

• Forebrain (Prosencephalon)
• Midbrain (Mesencephalon)
• Hindbrain (Rhombencephalon)

Fig: Parts of the brain

Cerebrum

The largest and most prominent part of the human brain is called cerebrum. It is a part of the forebrain and constitutes about 4/5^th of the total weight of the brain.

Fig: Cerebrum

Cerebral hemispheres

A deep median longitudinal cerebral fissure divides the cerebrum into two as follows:

• Right cerebral hemisphere
• Left cerebral hemisphere

Fig: Right and left hemispheres of cerebrum

Corpus callosum

The right and left cerebral hemispheres are connected through a tract of nerve fibres called corpus callosum. It is a large, C-shaped nerve fibre bundle and it stretches across the midline of the brain. Corpus callosum is present only in mammals. It is absent in Prototherians and poorly developed in Marsupials.

Fig: Corpus callosum

Folds of cerebrum

Surface of the cerebrum is highly convoluted and thrown into folds which increases surface area for accommodating more neurons. These folds are of two types and they are as follows:

• Gyri - These are the ridges found between the convolutions.
• Sulci - These are the depressions between the gyri.

Fig: Folds of cerebrum

Fissures of cerebrum

Right and left cerebral hemispheres are further divided into four lobes by three deep fissures. The fissures are as follows:

• Central fissure - It demarcates the frontal lobe from the parietal lobe.
• Parieto-occipital fissure - It demarcates the parietal lobe from the occipital lobe.
• Sylvian fissure - It demarcates the frontal and the parietal lobes from the temporal lobe.

Lobes of cerebrum

The four lobes of the cerebrum are as follows:

• Frontal lobe
• Parietal lobe
• Temporal lobe
• Occipital lobe

Frontal lobe

The largest lobe of cerebrum which is located at the front of each cerebral hemisphere is called the frontal lobes. The major sensory areas in the frontal lobe are premotor area (involuntary movements), motor area, Broca’s area (speech), and association area. The major functions of frontal lobe are as follows:

• Inner monitoring of complex thoughts and action.
• Translation of perceptions and memories into plans of muscle movement.
• Reasoning and decision making.
• Creative ideas.
• Expression of emotions.
• Will power and personality.
• Reality testing by judgement.
• Ability to abstract.

Fig: Frontal lobe

Parietal lobe

The lobe of the cerebrum which is positioned above the temporal lobe and behind the frontal lobe and central sulcus are called parietal lobe. The major sensory areas in the parietal lobe are gustatory area (taste) and somaesthetic area (for pain, touch, temperature etc). The major functions of the parietal lobe are as follows:

• Awareness about the position in space.
• Perceiving information from the environment, then organising and communicating to the rest of the brain.
• Receiving sensory perceptions of touch, heat, pain and cold.

Fig: Parietal lobe

Temporal lobe

The cerebral lobe which is located beneath the lateral fissure is called temporal lobe. The major sensory areas in the temporal lobe are Wernicke’s area (Understanding speech), olfactory area (smell) and auditory area (hearing). The major functions of temporal lobe are as follows:

• Decoding and interpretation of sound, smell, emotion and memory.
• Language comprehension.

Fig: Temporal lobe

Occipital lobe

The lobe of cerebrum which is located at the back of the head is called occipital lobe. The latin word ‘ob’ means behind and ‘caput’ means the head. The major sensory area in the occipital lobe is the visual area. The major functions of the occipital lobe is the decoding and interpretation of visual information of objects such as shape and colour.

Fig: Occipital lobe

Parts of cerebrum

Cerebrum can be divided into two parts as follows:

• Cerebral cortex - It is the outer layer
• Cerebral medulla - It is the inner layer

Fig: Parts of cerebrum

Cerebral cortex

The outer portion of the cerebrum is called the cerebral cortex. It is extensively folded. Outer layer of the cortex is also referred to as grey matter, because it is composed of the neuronal cell bodies and dendrites, as well as unmyelinated nerve fibres. The neurons give them a greyish appearance.

Cerebral medulla

The inner portion of the cerebrum is called the cerebral medulla. This inner part contains the myelinated axon fibres of the neurons which give it an opaque white appearance. So this part is called white matter.

Fig: Cross section of brain

Sensory areas of cerebrum

Cerebral cortex is considered as the highest centre for many activities and sensations. It had a number of sensory areas and they are as follows:

• Motor area

• Premotor area
• Association area
• Somaesthetic area
• Visual area
• Auditory area
• Motor speech area
• Sensory speech area
• Olfactory area
• Taste area

Motor area

The area which controls the voluntary movement of the muscles is called the motor area and it is present in the frontal lobe.

Premotor area

The centre which can control the involuntary movement of muscles is called the premotor area. It is also in the frontal lobe.

Association area

The centre which controls the association between the various sensations and movements is called association area. It is in the frontal lobe and is also the seat of learning.

Somaesthetic area

The area which controls the general sensations like pain, touch and temperature is called somaesthetic area and it is in the parietal lobes.

Visual area

The area in the occipital lobe which controls the visual sensation is called visual area.

Auditory area

The area in the temporal lobe that controls the hearing is called the auditory area.

Motor speech area

The area in the frontal lobe where the motor speech is controlled is called the motor speech area. It is also called Broca's area.

Sensory speech area

The area in the lower part of the parietal lobe where the sensory speech is controlled is called the sensory speech area. It is also called the Wernicke’s area.

Olfactory area

The area which controls the smell is called the olfactory area and it is located in the cerebral cortex of the temporal lobe.

Taste area

The area which controls the gustation is called the taste area and it is located in the parietal lobe.

Fig: Sensory areas of cerebrum

Limbic system

The inner parts of cerebral hemispheres and a group of associated structures like amygdala, hippocampus form the limbic system.

Fig: Limbic system

The location of the limbic system is just under the cerebrum, lying on both sides of thalamus. Along with the hypothalamus, it is involved in the regulation of sexual behaviour, expression of emotional reactions like excitement, pleasure, rage and fear, and motivation.

Fig: Thalamus and hypothalamus

Functions of cerebrum

The major functions of the cerebrum are as follows:

• Mental abilities like thinking, reasoning, learning, intelligence, and memory are governed.
• It controls will, speech and emotions.
• It is the seat of consciousness.
• It exerts strong control over reflexes such as laughing and weeping.
• It interprets various sensations or stimuli.

Cerebellum

The second largest part of the brain is called cerebellum and is a part of the hindbrain. It is also called little brain. For maintaining equilibrium and erect posture it is important.

Fig: Cerebellum

Location of cerebellum

The location of cerebellum is posterior to the medulla and pons. It is located inferior to the posterior portion of the cerebrum. In order to provide the additional space for many more neurons, cerebellum possesses a very convoluted surface.

Fig: Location of cerebellum

Parts of cerebellum

Just like in the cerebrum, there are two parts in the cerebellum as follows:

• Cerebellar cortex - It possesses the upper grey matter.
• Arbour vitae -It possesses the deep central white matter.

White matter is arranged in the form of patches giving the appearance of a tree-like structure called arbour vitae or tree of life. The cerebellar nuclei of the cerebellar cortex are scattered in the white matter. Fibre tracts are present in the white matter and it connects the cerebellum with medulla oblongata and thalamus or cerebrum. Neuroglial cells are also present in the cerebellum. Gyri and sulci of cerebellum are more symmetrical and it has Purkinje cells (most complex neurons of the brain).

Fig: Arbour vitae

Lobes of cerebellum

There are three lobes in the cerebellum and they are as follows:

• Vermis - It is the central part
• Two lateral or cerebellar hemispheres

Fig: Lobes of cerebellum

Functions of cerebellum

• It constantly receives information or input signals from proprioceptors in muscles, tendons, joints
• It constantly receives information or input signals from the receptors for equilibrium and visual receptors of eyes.
• It regulates rapid movements like running, typing, etc.
• It maintains balance and equilibrium.
• It maintains muscle tone.
• It regulates and coordinates the skeletal muscle contraction.
• Voluntary movements initiated in the cerebrum are modulated.

Differences between cerebrum and cerebellum

The major differences between cerebrum and cerebellum are as follows:

Practice Problems

Q1. Which of the following is the C-shaped nerve fibre bundle in the cerebrum?

A. Corpus callosum
B. Gyri
C. Sulci
D. Sylvian fissure

Solution: The right and left cerebral hemispheres are connected through a tract of nerve fibres called corpus callosum. It is a large, C-shaped nerve fibre bundle and it stretches across the midline of the brain. Corpus callosum is present only in mammals. Surface of the cerebrum is highly convoluted and thrown into folds which increases surface area for accommodating more neurons. These folds are of two types and they are gyri and sulci. The function of sylvian fissure is to demarcate frontal and parietal lobes from the temporal lobe. Hence the correct option is a.

Fig: Corpus callosum

Q2. Which lobe of the cerebrum has the following functions:

i) Decoding and interpretation of sound, smell, emotion and memory.

ii) Language comprehension.

A. Frontal lobe
B. Parietal lobe
C. Temporal lobe
D. Occipital lobe

Solution: The cerebral lobe which is located beneath the lateral fissure is called temporal lobe. The major sensory areas in the temporal lobe are Wernicke’s area (Understanding speech), olfactory area (smell) and auditory area (hearing). The major functions of temporal lobe are decoding and interpretation of sound, smell, emotion and memory and the language comprehension. Hence the correct option is c.

Fig: Temporal lobe

Q3. Match the sensory areas of the cerebrum in column I with their functions in column II:

a. i - A, ii - B, iii - C, iv - D
b. i - A, ii - B, iii - D, iv - C
c. i - B, ii - A, iii - C, iv - D
d. i - B, ii - A, iii - D, iv - C

Solution: Cerebral cortex is the highest centre for many sensations and activities. It had a number of sensory areas and they are motor area, premotor area, association area, somaesthetic area, visual area, auditory area, motor speech area, sensory speech area, olfactory area and taste area. The area which controls the voluntary movement of the muscles is called the motor area. The centre which controls the association between the various sensations and movements is called association area. The area in the frontal lobe where the motor speech is controlled is called the motor speech area. It is also called Broca's area. The area in the lower part of the parietal lobe where the sensory speech is controlled is called the sensory speech area. It is also called the Wernicke’s area. Hence the correct option is d.

Fig: Sensory areas of cerebrum

Q4. Which of the following statements about the cerebellum is incorrect?

A. It is a part of the hindbrain
B. Consists of two cerebral hemispheres and a median vermis
C. Controls voluntary actions, memory and intelligence
D. Gyri and sulci of the cerebellum are more symmetrical

Solution: The second largest part of the brain is called cerebellum and it is a part of the hindbrain. It is also called little brain. It is highly developed in humans for maintaining equilibrium and erect posture. Gyri and sulci of cerebellum are more symmetrical and it has Purkinje cells (most complex neurons of the brain). There are three lobes for the cerebellum and they are vermis (central part) and two lateral or cerebellar hemispheres. Cerebrum controls voluntary actions, memory and intelligence and cerebellum maintains equilibrium and control posture. Hence the correct option is c.

FAQs

Q1. What is the dominant hemisphere?
Answer: The centres for speech, intelligence and motor control areas are commonly more highly developed in one cerebral hemisphere than the other. It is called the dominant hemisphere. Left hemisphere is more dominant than the right hemisphere in 95 percent of the individuals.

Fig: Right and left hemispheres of cerebrum

Q2. Is it possible to live without cerebellum?
Answer: Yes, it is possible to live without cerebellum, even though many neurons are present in it. A few people have cerebellar agenesis (absence of the cerebellum) and they still live. In this condition the cerebrum never develops.

Q3. What is ataxia?
Answer: Damage to the cerebellum causes ataxia. It can also be caused due to any damage to the spinal cord or other nerves. Alcohol misuse, stroke, brain degeneration etc., can cause ataxia. This condition affects coordination, balance and speech.

Q4. What is a foramen of Monro?
Answer: Lateral ventricle is the cavity enclosed by each cerebral hemisphere. It is also called the second ventricle. The two lateral ventricles open behind into the third ventricle in diencephalon by a common aperture called foramen of Monro.