hjernen

hjernen (the brain) is the central organ of the nervous system in vertebrates, including humans. It integrates sensory information, coordinates movement, and enables a wide range of cognitive functions, emotions, and memories. The brain is enclosed within the skull and protected by the meninges and cerebrospinal fluid. In Norwegian and Danish, the definite form for the organ is hjernen.

Anatomically, it comprises three main parts: the cerebrum, the cerebellum, and the brainstem. The cerebrum, with the cerebral cortex, governs higher-order functions such as perception, reasoning, language, and voluntary action, and is organized into lobes with specialized regions. The cerebellum coordinates balance and precise motor control, while the brainstem regulates vital autonomic functions and relays information between the brain and spinal cord. The neural tissue includes gray matter in the cortex and white matter tracts, along with subcortical nuclei and ventricles filled with cerebrospinal fluid.

Development and function: The brain develops from the neural tube during embryogenesis; postnatally, plasticity and synaptic pruning shape neural circuits in response to experience. The brain is a high-energy organ, consuming a substantial portion of resting metabolic energy to support perception, thought, memory, learning, emotion, and coordinated movement.

Protection and circulation: It is safeguarded by the skull, meninges, and cerebrospinal fluid; blood is supplied by carotid and vertebral arteries and drained by cerebral veins. The blood-brain barrier helps regulate the neural environment.

Health and research: Common conditions include stroke, Alzheimer’s disease, Parkinson’s disease, epilepsy, migraine, and traumatic injury. Research employs imaging techniques such as MRI, fMRI, CT, and PET, along with electrophysiology and neuroanatomical mapping to study structure and function.