Problem 23 - Objective Biology for NEET

Question

Select the incorrect statement: (a) Cerebral cortex, greyish in appearance thrown into prominent folds known as sulci and gyri. (b) Concentrated neuron cell body gives grey color to the cerebral cortex. (c) Fibres of the tract, covered with myelin sheath, constitute inner part of cerebral hemisphere. (d) Cerebrum is wrapped around the structure called medulla.

Step-by-Step Solution

Answer

The incorrect statement is (d): 'Cerebrum is wrapped around the structure called medulla.'

Step 1: Analyse Statement (a)

Statement (a) 'Cerebral cortex, greyish in appearance thrown into prominent folds known as sulci and gyri.' is a correct statement. The cerebral cortex is indeed greyish in color and is characterized by folds and grooves known as sulci and gyri respectively.

Step 2: Analyse Statement (b)

Statement (b) 'Concentrated neuron cell body gives grey color to the cerebral cortex.' is also correct. The cell bodies of neurons, also known as grey matter, are present in the cerebral cortex gives it its greyish hue.

Step 3: Analyse Statement (c)

Statement (c) 'Fibres of the tract, covered with myelin sheath, constitute inner part of cerebral hemisphere.' is correct. These tracts of fibres, also known as white matter due to their appearance from the myelin sheath, indeed form the inner part of the cerebral hemisphere.

Step 4: Analyse Statement (d)

Statement (d) 'Cerebrum is wrapped around the structure called medulla.' is incorrect. The medulla is actually a part of the brainstem, which is located below the cerebrum and isn't 'wrapped' by it.

Key Concepts

Cerebral Cortex

The cerebral cortex is a fascinating and integral part of the human brain. It is the outermost layer of the cerebrum and is commonly referred to as the "grey matter" of the brain. This is because it appears greyish in color, a trait resulting from the concentration of neuron cell bodies. The cerebral cortex is characterized by its intricate folds and grooves, known as sulci and gyri, respectively. These structures increase the surface area of the cortex, allowing for a greater number of neurons to be packed into the brain, supporting complex processing abilities. The cerebral cortex is essential for many cognitive functions including thought, perception, memory, and decision-making. Moreover, it's divided into lobes, each responsible for different functions:

• Frontal lobe: Involved in reasoning, planning, and speech.
• Parietal lobe: Manages sensory information like touch and temperature.
• Occipital lobe: Processes visual information.
• Temporal lobe: Important for processing auditory information and memory.

The unique structure and function of the cerebral cortex make it a critical area for higher human cognition.

Neuron Cell Bodies

Neuron cell bodies, often referred to as grey matter, are crucial components of the nervous system. In the cerebral cortex, these neuron cell bodies form a dense layer that contributes to the cortex's distinctive grey color. Each neuron in the brain typically consists of a cell body, dendrites, and an axon. The cell body contains the nucleus, which is the control center of the neuron. It processes incoming information and is vital for the neuron's overall functioning. The neuron cell bodies in the cerebral cortex play a significant role in processing sensory input and executing motor output. They work together to support complex brain functions, such as:

• Decision making
• Problem-solving
• Emotion regulation

Their arrangement in the brain allows for efficient communication and coordination essential for various cognitive tasks.

Myelin Sheath

The myelin sheath is a protective covering that surrounds the axons of many neurons. This fatty layer is vital for the proper functioning of the nervous system. The primary role of the myelin sheath is to insulate axons, which are the long thread-like extensions of neurons that carry electrical impulses. Myelin increases the speed at which electrical signals travel along the axon, enhancing the efficiency of neural communication. In the brain, myelinated fibers constitute the white matter, located under the grey matter of the cerebral cortex. These fibers are crucial in facilitating rapid signal transmission between different parts of the brain. Without myelin,

• Signal transmission would slow down significantly.
• Coordination between different brain regions would be impaired.
• Cognitive and physical functions could be affected.

Therefore, the myelin sheath is essential for maintaining the fast communication pathways necessary for efficient brain and body interaction.

Cerebrum and Medulla Relationship

Understanding the relationship between the cerebrum and the medulla is essential to grasp the brain's structural and functional organization. The cerebrum is the largest part of the brain and is involved in nearly all major brain functions ranging from conscious thought to voluntary movement coordination. Contrary to the incorrect interpretation in the analysis, the cerebrum does not "wrap around" the medulla. Instead, the medulla is part of the brainstem, located beneath the cerebrum. The brainstem, including the medulla, plays a critical role in regulating autonomic functions such as breathing, heart rate, and blood pressure. The relationship between the cerebrum and the medulla involves:

• Pathways: Neural pathways connect the two, allowing the cerebrum to send commands to the medulla for vital functions.
• Coordination: Communication is essential for ensuring that involuntary functions support higher activities managed by the cerebrum.
• Integration: The medulla integrates sensorimotor information from the cerebrum required for maintaining body homeostasis.

This close relationship ensures that basic life-sustaining functions are tightly integrated with advanced cognitive processes.