Human Brain: Origin, Evolution, Function

Brain

The brain is one of the most complex and magnificent organ in the human body. Our brain gives us the awareness of ourselves and our environment, processing a steady stream of sensory data. our muscle movements controlled, secretions from the glands of ours, and even breathing and internal temperature. Every creative thought, feeling, and the plan is developed by our brain. brain neurons recorded memory of every event in our lives.

In fact, the human brain is so complicated that it is still an exciting frontier in the study of the body; doctors, psychologists and scientists continually strive to learn exactly how many brain structures work closely together to create our powerful human mind.

Anatomy of the Brain

There are different ways of dividing the brain anatomically regions. Let's use a common method and divide the brain into three main regions based on embryonic development: the forebrain, midbrain and hindbrain. In these divisions:

• The forebrain (forebrain o) consists of our amazing brain, the thalamus, the hypothalamus and the pineal gland among other characteristics. You neuroanatomists call the brain area of ​​the telencephalon and diencephalon use the term (or interbrain) to refer to the area where our thalamus, hypothalamus and the pineal gland resides.

• The midbrain (or midbrain), located near the center of the brain between the diencephalon and hindbrain, consists of a portion of the brain stem.

• Hindbrain (or hindbrain) consists of the remaining brainstem and cerebellum and pons our. Neuroanatomists have a word to describe the brain stem sub-region of our hindbrain, calling it the myelencephalon, as they use the word in reference to our hindbrain cerebellum and pons collectively.

Before exploring these different brain regions, first let's define the major types of cells and tissues that are the building blocks of all.

Histology

Brain cells can be divided into two groups: neurons and glia.

Neurons, or nerve cells, are the cells that perform all communication and processing in the brain. Sensory neurons that enter the brain from the peripheral nervous system provide information about the condition of the body and its surroundings. Most of the neurons in the gray matter of the brain are interneurons, which are responsible for the integration and processing of information to the brain by sensory neurons. Interneurons send signals to motor neurons, which carry signals to muscles and glands.

Glia or glial cells act as helper cells of the brain; support and protect neurons. In the brain there are four types of glial cells: astrocytes, oligodendrocytes, microglia and ependymal cells.

• Astrocytes protect neurons by filtering nutrients from the blood and preventing chemicals and leaving pathogens brain capillaries.
• Oligodendrocytes surround the axons of the neurons in the brain to produce the insulation called myelin. nerve myelinated axons transmit signals much faster than unmyelinated axons, oligodendrocytes so accelerate the rate of communication of the brain.
• Microglia act as some white blood cells to attack and destroy pathogens that invade the brain.
• Ependymal cells and capillaries of the choroid plexus and blood plasma filter are aligned to produce cerebrospinal fluid.

Brain tissue can be divided into two broad classes: gray matter and white matter.

• Gray matter is made of myelinated neurons especially, most of which are interneurons. Gray matter regions are the areas of nerve connections and processing.
• The white matter is mainly of myelinated neurons connecting gray matter regions of one another and with the rest of the body. myelinated neurons transmit nerve signals much faster than unmyelinated axons do. Acts of white matter as the information highway of the brain to speed up connections between different parts of the brain and body.

HINDBRAIN (RHOMBENCEPHALON)

Brainstem

Connect the brain to the spinal cord, brain stem is the lower part of the brain. Many of the basic survival of brain functions are controlled by the brainstem.

The brain stem consists of three regions: the medulla, pons and midbrain. Similar to a network of gray and white matter mixed structure known as the reticular formation in the three regions of the brainstem. The reticular formation controls muscle tone in the body and acts as a switch between consciousness and sleep in the brain.

The medulla is a roughly cylindrical mass of nervous tissue that connects to the spinal cord at its lower edge and the bulge in its upper edge. Spinal contains mostly white matter nerve signals carrying the ascending and descending brain spinal cord. In several regions of spinal gray matter that process involuntary body functions related to homeostasis. The cardiovascular center of the spinal controls the levels of pressure and oxygen in the blood and regulates heart rate to provide sufficient supply of oxygen to body tissues. Downtown medullary rhythmicity controls the rate of breathing to provide oxygen to the body. Vomiting, sneezing, coughing and swallowing reflexes are coordinated in this region of the brain also.

The bridge is the region of the brainstem found above the medulla, below the midbrain and cerebellum above. With the cerebellum, it forms what is called the hindbrain. About an inch long and big and a little wider than the medulla, pons acts as a bridge for nerve signals traveling to and from the cerebellum and transmits signals between the upper regions of the brain and spinal and spinal spinal.

Cerebellum

The cerebellum is a wrinkled, hemispherical region of the back of the brain located below the brain and brain stem. The outer layer of the cerebellum known as the cerebellar cortex is made of neatly folded gray matter that provides the processing power of the cerebellum. Deep in the cerebellar cortex is a layer in a tree of white matter called Arbor Vitae, meaning "tree of life." The arbor vitae connects the processing regions of the cerebellar cortex to the rest of the brain and body.

The cerebellum helps control motor, such as balance, posture and coordination of the complex muscular activities functions. The cerebellum receives sensory information from the muscles and joints of the body and uses this information to keep the body balanced and maintain posture. The cerebellum also controls the timing and finesse of complex motor actions such as walking, writing and speaking.

MIDBRAIN (MESENCEPHALON)

Midbrain, also known as the midbrain is the uppermost region of the brainstem. Found between the protrusion and diencephalon, midbrain can be subdivided into two main regions: the tectum and brainstem.

• The tectum is the posterior region of the midbrain, which contains relays for reflections that involve auditory and visual information. The pupillary reflex (adjusting light intensity), accommodation reflex (focus on near or far objects), and scare reflexes are some of the many reflections relayed through this region.
• The formation of the anterior midbrain, the brainstem contain many nerve pathways and substantia nigra. nerve tracts passing through connecting regions brainstem and thalamus of the brain to the spinal cord and lower regions of the brainstem. The substantia nigra is one region of the dark melanin-containing neurons is involved in the inhibition of movement. Degeneration of the substantia nigra leads to a loss of Parkinson disease known as motor control.

FOREBRAIN (PROSENCEPHALON)

Diencephalon

Anterior superior midbrain and is the region known as the interbrain or diencephalon. Thalamus, hypothalamus and pineal gland make major regions of the diencephalon.

• The thalamus is a pair of lower oval masses of gray matter to the lateral ventricles and surrounding the third ventricle. Sensory neurons that enter the brain relay format of the peripheral nervous system neurons in the thalamus following the cerebral cortex. Thus the thalamus acts as the switchboard operator brain by routing to the correct sensory regions of the cerebral cortex entries. The thalamus plays an important role in learning by routing sensory information processing centers of the brain and memory.
• The hypothalamus is a region lower than the thalamus and brain pituitary gland located. The hypothalamus acts as the control center of the brain in body temperature, hunger, thirst, blood pressure, heart rate and hormone production. In response to changes in body condition detected by sensory receptors, the hypothalamus sends signals to the glands, smooth muscles, and the heart to counteract these changes. For example, in response to increases in body temperature, the hypothalamus stimulates the secretion of sweat from the sweat glands in the skin. The hypothalamus also sends signals to the cerebral cortex to produce feelings of hunger and thirst when the body lacks food or water. These signals stimulate the conscious mind to get food or water to correct this situation. The hypothalamus also directly controls the pituitary gland by producing hormones. Some of these hormones, such as oxytocin and antidiuretic hormone, is produced in the hypothalamus and stored in the posterior pituitary gland. Other hormones, such as releasing and inhibiting hormones are secreted in the blood to stimulate or inhibit hormone production in the anterior pituitary gland.
• The pineal gland is a small gland located behind the thalamus in a sub-region called the thalamus. The pineal gland produces the hormone melatonin. light striking the retina of the eye sends signals to inhibit the function of the pineal gland. In the darkness, the pineal gland secretes melatonin, which has a sedative effect on the brain and helps induce sleep. This function of the pineal gland helps explain why darkness is sleep induction and light tends to disrupt sleep. Babies produce large amounts of melatonin, allowing them to sleep up to 16 hours per day. The pineal gland produces less melatonin with age, resulting in difficulty sleeping during adulthood.

Cerebrum

The largest region of the human brain, the brain controls higher brain functions such as language, logic, reasoning and creativity. Diencephalon surrounds the brain and is higher than the cerebellum and brainstem. A deep groove called the longitudinal fissure runs sagittal in the center of the brain, dividing the brain into the left and right hemispheres. Each hemisphere can be divided into four lobes: frontal, parietal, temporal and occipital. The lobes are named for the skull bones that cover them.

The surface of the brain is a twisted layer of gray matter known as the cerebral cortex. Most brain processing is carried out within the cortex. The protrusions of the crust are called convolutions (singular: gyrus), while the slits are called grooves (singular: groove).

Deep to the cortex is a layer of the cerebral white matter. The white matter contains the connections between brain regions and between the brain and the body. A band of white matter called the corpus callosum connects the left and right brain hemispheres and allows communicate with each other.

Deep in the cerebral white matter are several regions of gray matter that make up the basal ganglia and limbic system. The nuclei of the base, including the globus pallidus, striatum and the subthalamic nucleus, working together with the substantia nigra of the midbrain to regulate and control muscle movements. Specifically, these regions help control muscle tone, posture and skeletal muscle subconscious. The limbic system is another group of deep gray matter regions, including the hippocampus and amygdala, which are involved in memory, survival, and emotions. The limbic system helps the body to react to emergency situations with highly emotional, almost involuntary rapid action.

With so many vital functions under the control of one amazing body - and so many important functions performed at its outer layers - how our body to protect the brain from damage? Our skull clearly offers some protection, but what protects the brain from skull itself? Keep reading!

Meninges

Three layers of tissue, known collectively as the meninges, surround and protect the brain and spinal cord.

• The dura form leather, outermost layer of the meninges. irregular dense connective tissue made of collagen fibers gives the dura difficult strength. Dural a pocket that surrounds the brain and spinal cord to keep the cerebrospinal fluid and prevent mechanical damage to the soft nerve tissue is formed. The dura mater name comes from the Latin for "tough mother" because of their protective nature.
• Arachnoid found lining the inside of the dura. Much thinner and more delicate than the dura, which contains many fine fibers that connect the dura mater and the pia mater. Arachnoid name comes from the Latin for "Mother Spider" because its fibers resemble a spider web. Below the arachnoid is a region filled with liquid known as the subarachnoid space.
• As the innermost layer of the meninges, the pia mater rests directly on the surface of the brain and spinal cord. The pia many blood vessels provide nutrients and oxygen to the nerve tissue of the brain. The pia mater also helps regulate the flow of cerebrospinal fluid materials from the bloodstream and nervous tissue.

Cerebrospinal Fluid

Cerebrospinal fluid (CSF) - a clear fluid surrounding the brain and spinal cord - offers many important functions in the central nervous system. Instead of being firmly anchored in the bones surrounding the brain, spinal cord and float inside the LCR. CSF filled subarachnoid space and exerts pressure on the outside of the brain and spinal cord. CSF pressure acts as a stabilizer and shock absorber for the brain and spinal cord, and floating within the cavities of the skull and vertebrae. Within the brain, CSF filled small cavities called ventricles expand under pressure to lift CSF and brain tissue inflate soft.

Cerebrospinal fluid is produced in the brain capillaries coated with ependymal cells known as the choroid plexus. Blood plasma passing through the capillaries is filtered by ependymal cells and is released into the subarachnoid space and CSF. The CSF contains glucose, oxygen and ions, which helps distribute throughout the nervous tissue. CSF also carries away waste products of nerve tissue.

After circulating around the brain and spinal cord, CSF enters small structures called arachnoid villi where it is reabsorbed into the bloodstream. arachnoid villi are finger-shaped extensions of the arachnoid passing through the dura and the superior sagittal sinus. The superior sagittal sinus is a vein running through the longitudinal slot in the brain and carries blood and cerebral spinal fluid back to the heart.

Physiology of the Brain

Metabolism

Despite weighing only about 3 pounds, the brain consumes as much as 20% of the oxygen and glucose taken by the body. Nerve tissue in the brain has a very high metabolic rate, due to the large number of decisions and processes that occur in the brain at any given time. The large volumes of blood must be constantly delivered to the brain in order to maintain the proper brain function. Any interruption in the blood supply to the brain very quickly leads to dizziness, disorientation, and finally unconsciousness.

Sensory

The brain receives information about the condition of the body and its environment from all sensory receptors in the body. All this information is entered into the sensory areas of the brain, which collect this information to create a perception of internal and external conditions of the body. Part of this sensory information is the autonomous sensory information, which tells the brain subconsciously about the condition of the body. body temperature, heart rate and blood pressure are all autonomous senses that the body receives. Other information is somatic sensory information that the brain is conscious. Touch, sight, sound and hearing are all examples of somatic senses.

Motor Control

Our brain directly controls almost every movement in the body. A region of the cerebral cortex known as the engine area sends signals to the skeletal muscles to produce all voluntary movements. Basal ganglia of the brain and gray matter in the brain stem helps to control these movements unconsciously avoid extraneous movements are undesirable. The cerebellum helps with timing and coordination of these movements during complex movements. Finally, the smooth muscle tissue, cardiac muscle, and glands are stimulated by motor outputs of the autonomous regions of the brain.

Processing

Once entered sensory information in the brain, the association areas of the brain will work processing and analyzing this information. Sensory information is combined, evaluated and compared to previous experiences, providing the brain with an accurate picture of conditions. Association areas also work to develop action plans that are sent to motor regions of the brain in order to produce a change in the body through the muscles or glands. association areas also work to create our thoughts, plans and personality.

Learning and Memory

The brain needs to store many different types of information received from the senses and develops through thought in the areas of partnership. Information is stored in the brain in a few different ways depending on their source and time it takes. Our brain keeps short-term memory to keep track of the tasks that the brain is currently being undertaken. The short-term memory is believed to consist of a group of neurons that stimulate each other in a loop to keep data in memory of the brain. New information replaces the old information in short-term memory within a few seconds or minutes, unless the information is transferred to the long-term memory.

The long-term memory is stored in the brain from the hippocampus. The hippocampus transfers information from short-term memory to storage memory regions of the brain, especially in the cerebral cortex of the temporal lobes. The related motor skills (known as procedural memory) memory is stored by the basal ganglia and cerebellum.

Homeostasis

The brain acts as the control center of the body by maintaining the homeostasis of many different functions such as breathing, heart rate, body temperature, and hunger. The brainstem and hypothalamus are more concerned with homeostasis brain structures.

In the brainstem, medulla oblongata contains the cardiovascular center that monitors the levels of dissolved carbon dioxide and oxygen in the blood, with the blood pressure. The cardiovascular center adjusts the heart rate and dilating the blood vessels to maintain healthy levels of gases dissolved in the blood and maintain a healthy blood pressure. The center of the spinal cord rhythmicity controls the levels of oxygen and carbon dioxide in the blood and respiration rate adjusted to maintain these levels in balance.

The hypothalamus controls the homeostasis of body temperature, blood pressure, sleep, thirst and hunger. Many autonomic receptors for temperature, pressure, and dosing means in the hypothalamus. The hypothalamus processes sensory information it receives and sends the output to the autonomic effectors in the body, such as sweat glands, heart and kidneys.

Sleep

While sleep may seem to be a time of rest for the brain, this organ is actually very active during sleep. The hypothalamus maintains biological clock 24 hours body, known as the circadian clock. When the circadian clock indicates that it is time to sleep, it signals the reticular activating system of the brain stem to reduce the stimulation of the cerebral cortex. Reduction in the stimulation of the cortex leads to a feeling of drowsiness and eventually leads to sleep.

In a state of sleep, the brain fails to maintain awareness, reduce some of their sensitivity to sensory stimuli, relaxes the skeletal muscles, and complete many administrative functions. These include consolidating administrative functions and storage memory, sleep, and development of nerve tissue.

There are two main stages: the dream of rapid eye movement (REM) and non-rapid eye movement (NREM). During REM sleep the body is paralyzed while the eyes move back and forth quickly. Sleep is common during REM sleep is believed that some memories are stored during this phase. NREM sleep is a period of slow eye movement or no movement of the eyes, culminating in a deep sleep in the lower brain electrical activity. Dreaming during NREM sleep is rare, but the memories are processed and stored during this time.

Reflexes

A reflex is an involuntary to a form of internal or external stimulus rapid reaction. Many reflexes in the body are integrated in the brain, including the pupillary light reflex, coughing and sneezing. Many reflexes protect the body from damage. For example, cough and sneeze to clear the airways of the lungs. Other reflexes help the body respond to stimuli, such as the adjustment of pupils to bright or dim light. All reflections occur quickly without going through the control centers of the cerebral cortex and integration into the nether regions of the brain such as the environment or limbic brain system.