Q.Cerebral hemispheres are connected by a tract of nerve fibres called ______ .

The Cerebrum: The Brain's Command Centre

Think of the cerebrum as the CEO of your brain. It's the largest, most visible part — that wrinkled, walnut-shaped mass that fills most of your skull. While the brainstem handles automatic tasks like breathing and the cerebellum coordinates balance, the cerebrum is where the "you" lives: your thoughts, decisions, memories, and conscious experiences.

When you decide to pick up a pen, feel the texture of paper, remember a friend's face, or solve a math problem — that's the cerebrum at work. It's the seat of voluntary action, sensory perception, memory, and intelligence.

Structure: The Wrinkled Map

The cerebrum is divided into two halves called cerebral hemispheres — left and right. They're connected by a thick bridge of nerve fibres called the corpus callosum, which lets them talk to each other.

The surface is folded into ridges (gyri, singular: gyrus) and grooves (sulci, singular: sulcus). These folds dramatically increase the surface area, packing more neurons into a limited space. Deep fissures divide each hemisphere into four lobes, each with specialised jobs:

The outer layer, about 2–4 mm thick, is the cerebral cortex — grey matter made of neuron cell bodies. Beneath it lies white matter, composed of myelinated axons that connect different brain regions.

Function: What Each Part Does

Motor Control — The Frontal Lobe Takes Charge

The primary motor cortex, a strip at the back of the frontal lobe, sends commands to muscles. Different body parts are mapped onto this strip — hands and face take up the most space because they require fine control. This is called the motor homunculus (a distorted "little man" representation).

When you decide to raise your arm, the frontal lobe fires signals down through the brainstem and spinal cord to the muscles. Damage here causes paralysis on the opposite side of the body (because each hemisphere controls the contralateral side).

Sensory Perception — The Parietal and Occipital Lobes

The primary somatosensory cortex in the parietal lobe receives touch, pressure, pain, and temperature signals from the body. Again, there's a sensory homunculus — lips and fingertips are hugely overrepresented because they're so sensitive.

The occipital lobe processes everything you see. Light hits your retina, signals travel to the thalamus, then to the primary visual cortex. From there, specialised areas interpret colour, motion, and shape.

The temporal lobe handles hearing (auditory cortex) and helps you understand spoken language (Wernicke's area, usually on the left side).

Memory and Intelligence — A Distributed Network …