Brain
The brain is the most complex organ of the human body. Weighing about 1,400 g (only 2% of body weight), it consumes up to 20% of the body's total energy. It contains 86 billion neurons, each of which forms thousands of synaptic connections.
Shells and protection
The brain is surrounded by three membranes:
- Dura mater (dura mater) - dense, adjacent to the bones of the skull
- Arachnoid membrane (arachnoidea) - thin, forms the subarachnoid space
- Soft shell (pia mater) - directly covers the brain, contains blood vessels
Between the arachnoid and pia mater, cerebrospinal fluid (CSF) circulates - about 150 ml, which is renewed 3-4 times a day. Liquor performs shock-absorbing, nutritional and protective functions.
Large hemispheres
The cerebral cortex is the highest division of the central nervous system. The area of the cortex reaches 2,200 cm² due to numerous convolutions and grooves. Each hemisphere is divided into four lobes:
- Frontal lobe - planning, decision-making, voluntary movements, speech (Broca's center)
- Parietal lobe - tactile sensitivity, spatial orientation
- Temporal lobe - hearing, memory, speech understanding (Wernicke's center)
- Occipital lobe - visual perception
The right and left hemispheres are connected by the corpus callosum - a massive bundle of 200 million nerve fibers.
Subcortical structures
The thalamus is the “gate of consciousness” through which almost all sensory information passes before being sent to the cortex. The hypothalamus is a neuroendocrine center that regulates body temperature, hunger, thirst and circadian rhythms. Basal ganglia (striatum, globus pallidus) - are involved in the regulation of movements; their defeat underlies Parkinson's disease.
Brainstem
The trunk consists of the midbrain, pons and medulla oblongata. Vital centers are located here: respiratory, vasomotor and the nuclei of most cranial nerves. Damage to the brain stem is incompatible with life.
Cerebellum
The cerebellum contains more than half of all neurons in the brain, although its mass is only 10% of the total. It coordinates movements, maintains balance, and is involved in motor learning. Damage to the cerebellum leads to ataxia, a loss of coordination.
Blood supply
The brain receives blood through four arteries: two internal carotid and two vertebral. They form the Circle of Willis - an arterial ring at the base of the brain. Stopping blood flow for at least 5 minutes causes irreversible neuronal death - this is the basis of ischemic stroke.
You can view all parts of the brain in detail in 3D atlas Humio - rotate the model and study each structure layer by layer.