Human Brain Anatomy
The human’s brain weighs approximately 1,400 grams, depending on the person’s body weight and sex. However, there is no connection between the weight of an individual’s brain and his or her intelligence.
The telencephalon accounts for about 80% of the brain mass. The brain is also divided into two halves (hemispheres) connected by the corpus callosum. The brain processes sensory information, coordinates and maintains the functions of the organism.
This requires constant communication between the billions of nerve cells of the brain (neurons) through electrical impulses, which can be measured with the electroencephalogram (EEG).
Certain functions of the brain may be assigned to certain anatomical regions of the brain. According to the person, some faculties of the brain are located on different sides. By observing the metabolism of the brain, for example, the consumption of oxygen or glucose, by deflecting brain waves in the form of EEG, brain activity can be made visible through the metabolic changes that accompany it. Such functional studies of brain metabolism may be performed, for example, with positron emission tomography (PET) or functional magnetic resonance imaging (MRI).
Anatomy of the Brain- Structure of the Brain
The central nervous system (CNS) is composed of two main parts: the spinal cord and the brain, located in the head. The brain is surrounded by the skull and within three membranes which are called meninges. There is also cerebrospinal fluid among these which allows the brain to be floating and well protected from injury or blows.
The mass of the brain, which consists of nerve cells, glial cells and blood vessels has numerous folds or convolutions, so that the brain surface is multiplied many times. Within the brain, there are also cerebrospinal fluid cavities called cerebral ventricles which communicate with external spaces of cerebrospinal fluid.
The spinal cord is also surrounded by cerebrospinal fluid. Since all spaces with cerebrospinal fluid are connected, by puncturing the spinal cord at the lumbar level, cerebrospinal fluid can be obtained from the brain for analysis.
The brain can be divided into the following parts:
- Brain (telencephalon) and cerebral cortex (cortex)
- Cerebellum (midbrain)
- Diencephalon, which includes among other things (the pituitary gland and thalamus)
- Cerebral trunk with midbrain and medulla oblongata (medulla oblonga or myelencephalus)
What is Telencephalon?
The telencephalon is the largest and most developed part of the brain. The bark of a thickness of two to four millimeters (cortex) contains many folds, reason why the surface multiplies many times.
The cerebral cortex consists of cellular bodies with between 19 and 23 billion of nerve cells, also called gray matter because of its gray color.
The cortex can be classified into different cortical areas according to their characteristics:
- The sensory cortex processes the information of the senses
- The motor cortex develops movement
- The cerebellum coordinates the movements to be precise
- The axons are in the inner part of the cerebral cortex. They are surrounded by the so-called myelin
The telencephalon is divided into two largely symmetrical halves (hemispheres), joined together by the so-called corpus callosum. Most function centers are symmetrically in each hemisphere, but some centers are unique, such as the center of language, and are located individually in the right or left hemisphere.
Each hemisphere can be divided into different parts:
- Frontal lobe: in the frontal area of the brain; Movement, behavior
- Parietal lobe: upper back; Sensations
- Temporal lobe: located behind each temple; Recognition of people, hearing
- Occipital lobe: at the back of the head; view
What is Cerebellum?
The cerebellum is a walnut-sized structure, located at the base of the skull, beneath the occipital lobe of the brain. Functions such as balance, movement, coordination and language acquisition are coordinated in here.
The cerebellum distinguishes the movements and stores the processes so that after some practice certain movements can be performed automatically.
What is Diencephalon?
The diencephalon or middle brain consists of the thalamus, hypothalamus, subthalamus, and epithelium. Emotions such as sadness, joy, and others are processed in this region.
In the thalamus, information is received from the body and from the various sensory organs and it is sent to the brain after previously filtering the information.
This way you can avoid an overload of the brain. Other names of the thalamus are “gate of consciousness” or “gate of the cerebral cortex”.
The hypothalamus controls various life processes, such as the sleep-wake cycle, water balance, sweat and sensations of pain and temperature, and is influenced by both nerves and hormones. It is in direct contact with the pituitary gland and is a link between the hormonal and nervous systems.
What is Brainstem?
The brainstem is the oldest part of the brain. It is found under the other sections, near the spinal cord, and is almost completely surrounded by the cerebral hemispheres.
The brainstem can be divided into:
- Middle Brain (midbrain)
- Thoracic bulb (myceliacephalus)
- Fronto cephalic bridge (pons)
- Spinal cord
The mesencephalon sends information from the spinal cord to the brain and from the brain to the motor nerves and coordinates among other things.
At the back of the brain, at the level of the spinal cord, the incoming nerve pathways intersect, so that information from one part of the body is processed in the opposite hemisphere.
Functions such as heart rate, respiration, and metabolism, as well as reflexes such as vomiting and cough are coordinated in the posterior brain.
Anatomy of the Brain-Brain Cells
The brain is composed of a series of cells, which can be classified according to their appearance and functioning. The most important and numerous cells are nerve cells (neurons). There are about 200 billion neurons in the human brain.
A nerve cell consists of a nucleus or cell body (soma), with extensions of nerve cells (dendrites) and axon-cylinders (axons). The nerve cell body has a size of about 5 to 100 microns, while the extensions of the nerve cells narrow to a diameter of about one micron. An extension of a nerve cell can be up to one meter long and a single nerve cell can have up to 10,000 extensions.
At the point of contact with neighboring cells, the synapse is formed. By this synapse, the nerve cells are united not only with each other, but also they are united to muscular endings at different levels.
The exchange of information between cells takes place through the synapse through chemical messengers (neurotransmitters). For the communication of the information, the important thing is to form many synapses, reason why the number of nerve cells plays a minor role.
Because neurons no longer divide after birth, they are rarely the cause of brain tumor diseases.
Neurons are covered by glial cells, which make up about 50% of the total brain volume. Most brain tumors originate in these cells called gliomas. Glial cells can be further subclassified into astrocytes, oligodendrocytes, ependymal cells and microglia or microglial cells.
Astrocytes play an important role in the metabolism and supply of nutrients to the brain of the brain and are part of the blood brain barrier. Oligodendrocytes form myelin to coat extensions of nerve cells along the ventricles of the brain. Microglial cells are derived from the bone marrow and have functions in the immune system of the nervous system.
Anatomy of the Brain-Blood Vessels and Brain Membranes
There are some gaps called foramen in the skull. This is where special blood vessels come in from the neck. In the major opening (foramen magnum) the brainstem is related to the spinal cord.
Inside the skull, there are three cerebral membranes (meninges). The spaces between the meninges are filled with cerebrospinal fluid (CSF).
- Dura mater
- Arachnoids: Here many blood vessels flow and is where the exchange between the cerebrospinal fluid and blood takes place
- Soft Meninges: Supplies the brain with nutrients
- Cerebrospinal fluid forms in the brain’s cavities (ventricles) and protects the brain against impacts and bumps. In addition, it contributes to the elimination of brain waste
The numerous small blood vessels (capillaries) of the brain are important. The cells that line the vessels of the capillaries (endothelial cells) and the glial cells that cover them constitute a functional unit. This functional unit is called the blood-brain barrier.
This barrier only leaves few substances, mostly fatty substances (lipophilic) and regulates, thanks to its selective permeability, the entry and exit of substances into the brain. In this way, many drugs, toxins, viruses and bacteria can not reach the brain.
Anatomy of the brain-Cranial nerves
Twelve pairs of cranial nerves come out of the brainstem which are surrounded by the meninges:
- Olfactory nerve: odor
- Optic nerve: sight
- Oculomotor nerve: eye movements
- Troclear nerve: eye muscles
- Trigeminal nerve: facial nerves
- Abductor nerve: eye muscles
- Facial nerve: facial expression, taste
- Vestibulocochlear nerve: ear, balance
- Glossopharyngeal nerve: taste, swallowing
- Vague nerve: glands and hormones
- Accessory or spinal nerve: head and neck movements
- Hypoglossal nerve: tongue
- The cranial nerves have motor (movement), sensory (sensations) and vegetative functions (somatosensory sensations, ie, sensations of internal organs)
All other nerves that supply information to the brain and carry information from the brain to the different parts of the body originate in the spinal cord.
Anatomy of the Brain-Functional Map
Today a functional map of the brain can be created. It is already known that the functions of the frontal lobe are intelligence, language (motor speech center), personality characteristics and movement control.
In the back of the brain, the occipital lobe is the visual cortex. That is the place where visual stimuli are perceived, stored and classified. Hormonal secretions are controlled by the diencephalon.
The temporal lobe is important for memory, feelings and emotions. It houses the auditory cortex and the understanding of the language.
Abstract mathematical problems and music are perceived in the parietal lobe.
In the brain stem, nerves connect the brain with the spinal cord. Also, here is the center of the breath. It governs breathing, cardiovascular system and blood pressure. In the pituitary gland (pituitary) hormones or hormone precursors are released.
The cerebellum maintains the programs of the movement and regulates the coordination of movements. Since most brain functions can be assigned to a specific anatomical brain region, a brain tumor can be localized because of its loss or failure.