The Extraordinary Fu Organs (Qi Heng Zhe Fu)
The Marrow (Sui), Brain (Danao) , Bones (Gu), Blood Vessels (Mai), Uterus (Zigong) and Gallbladder (Dan) all store Yin Essences but have the shape (hollow) of a Yang Organ. They store the Essence but do not excrete. Therefore, they are called Extraordinary Yang Organs (1, 2, 3).
The common characteristics of these organs are that they store some form of yin essence (Kidney Essence, Marrow or Blood) and they are all functionally, directly or indirectly, related to the Kidneys.
The Chinese medical concepts of the Extraordinary Organs will be discussed as well as their Western medical counterparts. Western organs are described by their pure morphological or substantial structure. Their function is obtained through the anatomic analysis of the organs. On the other hand, the Chinese Organs are described by concepts formed by centuries of observation of various functions of the body, external manifestations, the interrelation between the organs, connection with environment and vital substances. Each Chinese organ is defined by a non-overlapping set of physiological, mental and spiritual functions. For example, the Blood Vessels contain Blood; the Heart controls Blood and Houses the Mind.
The interested reader could do further research to relate exactly which parts of western organs correspond to the Chinese Organ function (4). For example, parts of the cerebral cortex function like the Heart (Mind). The free, smooth flow of Qi, controlled by the Liver, is required for smooth movements, which is a function of the cerebellum, discussed below.
1. Marrow (Sui)
Kidney Essence produces Marrow which fills and nourishes the Brain and spinal cord and forms the Bone Marrow. Simple Questions states that the Bones are the residence of Marrow and Chapter 34 says that if the Kidneys are deficient, Marrow cannot be abundant.
Western Concepts of Marrow
In western medicine the term marrow refers to soft, gelatinous tissues that fill the cavities of bones. There are two types of bone marrow: red marrow (medulla ossium rubra), consisting mainly of hematopoietic tissue, and yellow marrow (medulla ossium flava), comprised mainly of fat cells. Both types of bone marrow contain numerous blood vessels and capillaries.
Red blood cells, platelets, stem cells and most white blood cells originate in red marrow. At birth, all bone marrow is red. With age, more and more marrow is converted to the yellow type; only about half of adult bone marrow is red. Red marrow is found mainly in the flat bones, such as the pelvis, sternum, cranium, ribs, vertebrae and scapulae, and in the cancellous (“spongy”) material at the epiphyseal ends of long bones such as the femur and humerus.
The red bone marrow is a key element of the lymphatic system. Hematopoietic precursors from the bone-marrow, called thymocytes, mature into T-cells in the thymus gland. Once mature, T-cells emigrate from the thymus and constitute the peripheral T-cells of the adaptive immune system.
Yellow marrow is found in the medullary cavity, the hollow interior of the middle portion of long bones. In cases of severe blood loss, the body can convert yellow marrow back to red marrow to increase blood cell production.
Various diseases and drugs can affect the bone marrow. Malignancies, aplastic anemia, or infections such as tuberculosis can lead to a decreased production of blood cells and blood platelets. There are types of leukemia that are cancers of the hematologic progenitor cells in the bone marrow. Exposure to radiation or chemotherapy can kill many of the rapidly dividing cells of the bone marrow and so result in a depressed immune system. Many of the symptoms of radiation sickness are due to damage to the bone marrow cells.
A bone marrow aspiration is sometimes performed to diagnose diseases of the bone marrow. This typically involves using a hollow needle to acquire a sample of red bone marrow from the crest of the ilium under general or local anesthesia.
2. Brain (Danao)
Chapter 33 in the Miraculous Pivot states that the Brain is a Sea of Marrow. Its upper part lies beneath the scalp with vertex at Bahui (Du 20) and its lowest part at Fengfu (Du 16). Chapter 10 in Simple Questions says that the Marrow pertains to the Brain. The Du (Govening) Meridian ascends the spinal column and enters the Brain at Fengfu. Many acupoints of the Du Meridian are used for pathological conditions of the Brain.
In Simple Questions, says that the head is the residence of intelligence. This can be interpreted as stating that the Brain is related to thinking. the Miraculous Pivot states that deficiency of the Brain leads to vertigo and dizziness.
The Brain is functionally related to the Kidneys, since Marrow originates from the Kidneys. The Brain is nourished by the Heart, particularly Heart Blood. The Kidneys store Essence and the Heart governs Blood. If Essence and Blood are abundant, the Brain will be healthy, vision and hearing will be clear. Deficiency of Heart Blood and Kidney Essence can result in slow thinking, poor memory, low vitality and impaired sight and hearing. The interrelation of the Brain with the Kidney and Heart explains why in clinical practice symptoms such as poor memory and concentration, blurred vision and dizziness can result from a deficiency of the Kidney essence or Heart Blood.
The ancient Chinese doctors ascribed the functions of the Brain to various Organs, particularly, the Kidneys, Heart and Liver. Therefore, many syndromes and treatments of brain disorders are included in syndromes of the Organs.
Later, some of these functions of the Brain were ascribed to the brain itself. In the Ming Dynasty (1368-1644), Li Shizhen clearly indicated that the Brain is the palace of the Mind. During the Qing Dynasty (1644-1911), Wang Qingren’s book, “Revision of the Medical Classics” postulated that intelligence and memory rely on the brain. He stated that thinking, memory, smelling, vision, hearing and speaking are all functions of the brain.
Western Concepts of the Brain
The nervous system is composed of two parts. The central nervous system (CNS) consists of the brain and spinal cord. The peripheral nervous system is composed of cranial and spinal nerves, which carry impulses to and from the central nervous system. The cranial nerves handle head and neck sensory and motor activities, except the vagus nerve, which conducts signals to visceral organs. Each spinal nerve is attached to the spinal cord by a sensory and a motor root. These exit between the vertebrae and merge to form a large mixed nerve, whose branches supply a defined area of the body. The autonomic nervous system, sometimes considered as another division, is part central and part peripheral.
The brain is a complex organ which receives information from other parts of the body via the spinal cord and the peripheral nervous system. It uses this information to control basic life processes, like breathing, body temperature and blood pressure, as well as higher functions like creative thought and emotions.
The brain is comprised of two types of cells: nerve cells (neurons) and glial cells. Glial cells have multiple functions, which include structurally supporting neurons, repairing the CNS, and regulating the biochemical balance of the brain. The blood-brain-barrier is composed of astrocytes, a special type of glial cell. This barrier prevents many substances in the blood from entering the brain.
The brain is surrounded and protected by the rigid, bony skull and three membranes, called meninges. The tough, fibrous outer membrane is the dura mater. The archanoid, the intermediate membrane, is web-like. The pia mater is the innermost covering and is the most delicate. It is molded to the shape of the brain. The cerebrospinal fluid (CSF) surrounds the brain and spinal cord. It flows through open chambers in the brain, called ventricles, and out an opening to the spinal cord. The brain actually floats in the shock-absorbing CSF, and is thus protected from trauma. The CSF also brings nutrients to the brain and removes wastes.
The brain has 3 main parts: forebrain, midbrain and hindbrain, as shown in Fig. 1.
Forebrain (Prosencephalon)
The forebrain is the largest part of the brain, most of which is the cerebrum, consisting of the cerebral cortex, corpus striatum and olfactory bulb. The other major division of the forebrain is the diencephalon, which includes the hypothalamus, thalamus, epithalamus (including the pineal gland), and subthalamus.
Cerebrum
Cerebral Cortex
The outermost and top layer of the brain is the cerebral cortex. The cerebral cortex is composed of two similar halves called hemispheres, having different functions. The left side of the cerebral cortex controls the right side of the body and speech. The right side controls the left side of the body and the perception of spatial relationships, such as where one’s hand might be located in relation to the ground, without looking. There are individual variations, for example, the language center is on the right in 2 percent of right-handed people and also in about 50% of left-handed people
The hemispheres are separated by a deep groove, but are linked by the corpus callosum, anterior commissure, posterior commissure, and hippocampal commissure. All of these transfer the information between two hemispheres to coordinate functions.
The outer layer of the hemispheres is composed of gray matter, consisting of neuronal cell bodies. The inner core of the hemispheres is composed of white matter, consisting of axons of neurons. The cortex contains ridges (gyri) and valleys (sulci).
Figure 3
Lobes of the Hemispheres of the Brain
The cerebral cortex has association and motor areas. Association areas include the parietal, temporal, and occipital lobes, which are involved in producing perceptions, resulting from sensory organs and the frontal lobe (or prefrontal association complex); involved in movement and planning, as well as abstract thought. Motor areas are related to controlling voluntary movements. They are located in the frontal lobes. The primary motor cortex executes voluntary movements, while the premotor cortex selects the movement (with the aid of supplementary motor areas).
Some functions of the lobes appear in Table 1. All of the lobes also contain areas for which specialized functions have not yet been identified. These areas are known as the association cortex and are thought to be involved in complex, higher-level mental activity.
Functions of Lobes of the Brain
Corpus Striatum
The corpus striatum, or “striped body” consists of the basal ganglia (basal nucleus) and the internal capsule. The basal ganglia are composed of neurons and so are gray matter. The internal capsule is a group of tracts surrounded by myelinated axons and so appears white. The internal capsule runs between the caudate and lenticular nucleus of the basal ganglia and so the group of structures looks striped.
Figure 4
The Basal Ganglia
The basal ganglia consist of the caudate nucleus and the lenticular nucleus, which is divided into the putamen and the globus pallidus.
The components of the basal ganglia that control the motor functions are sometimes called the “extrapyramidal motor system.” Though the basal ganglia are important in motor and learning functions, it also plays a part in addictions and emotions.
The caudate nucleus is partitioned into a head, body and tail. It contains endorphins, which produce a positive emotional state.
The lenticular nucleus is also called the lentiform nucleus (lentiform means lens-shaped in Latin). The putamen is the most lateral part of the structure. Its main function of the putamen is to regulate movements and influence various types of learning and uses the neurotransmitter dopamine to perform its functions.
The globus pallidus, the more medial part of the lenticular nucleus, regulates movements which occur on the subconscious level. It has a primarily inhibitory action to balance the excitatory action of the cerebellum. These two systems are designed to work in harmony with each other to allow people to move smoothly. Imbalances can result in tremors, jerks, and other movement problems, as seen in patients with progressive neurological disorders with symptoms like tremors.
The amygdala, attached to the tail of the caudate nucleus, involved in emotions. It was once classified as part of the basal ganglia, but is now part of the limbic system.
The subthalamic nuclei and the substantia nigra are both functionally related to the basal ganglia.
Olfactory Bulb
The olfactory bulb is on the inferior (bottom) side of the brain as shown in Fig. 4.
It receives neural input about odors detected by cells in the nasal cavity. The axons of olfactory receptor (smell receptor) cells extend directly into the highly organized olfactory bulb, where information about odors is processed.
figure 5
Diencephalon
(a) Hypothalamus
This part of the brain regulates hunger, thirst, pain, pleasure, sexual satisfaction, anger, etc. It also regulates the parasympathetic and sympathetic, thus controlling blood pressure, heart rate, breathing, digestion, etc. It also stimulates the pituitary gland, is responsible for hormone levels, and so is important in regulating growth and metabolism.
(b) Thalamus
The thalamus translates signals from “pre-thalamic” inputs to cortex-readable signals. It also plays an important role in regulating states of sleep and wakefulness. Thalamic nuclei have strong reciprocal connections with the cerebral cortex, forming thalamo-cortico-thalamic circuits that are involved with consciousness. The thalamus plays a major role in regulating arousal, levels of awareness, and activity. Severe damage to this area causes permanent coma.
(c) Epithalamus
The epithalamus is a dorsal posterior segment of the diencephalon. It regulates the motor pathways and emotions. It is connected with the limbic system and basal ganglia.
The pineal gland is a small endocrine gland that is part of the epithalamus. Its shape resembles a tiny pine cone, hence its name. It produces melatonin, which affects the modulation of wake/sleep patterns and seasonal functions.
(d) Subthalamus
The major part of the subthalamus is the subthalamic nucleus (SNT). Functionally, it also encompasses the globus pallidus, which is part of the telencephalon. The function of the STN is unknown, but current theories place it as a component of the basal ganglia control system that may perform action selection. STN dysfunction has also been shown to increase impulsivity in individuals presented with two equally rewarding stimuli.
Midbrain (Mesencephalon)
The midbrain or mesencephalon is composed of the tectum, tegmentum, the ventricular mesocoelia and the cerebral peduncles, as well as several nuclei and fasciculi. Caudally the mesencephalon adjoins the pons (metencephalon) and rostrally it adjoins the diencephalon (thalamus, hypothalamus, etc.). The midbrain is located below the cerebral cortex, and above the hindbrain placing it near the center of the brain.
(a) Tectum
The tectum is located in the dorsal region of the mesencephalon. It consists of the superior colliculi (visual receptors) and inferior colliculi (auditory receptors) and is involved in controlling auditory and visual responses.
(b) Tegmentum
Tegmentum helps control motor functions, regulates awareness and attention. It also regulates some autonomic functions.
(c) Ventricular Mesocoelia
The ventricular mesocoelia, also known as the cerebral aqueduct, the iter or the aqueduct of Sylvius, connects the third and fourth ventricles of the brain.
(d) Cerebral Penduncles
The cerebral peduncles are two tracts underneath the tegmentum that are often considered part of the mesencephalon. These tracts are bundles of nerve fibers passing over the bottom of the brain that connect the cerebral hemispheres to the spinal cord.
Hindbrain (Rhombencephalon)
The hindbrain includes the cerebellum, the pons and the medulla oblongata, which function collectively to support vital bodily processes (Fig. 5). Often the midbrain, pons, and medulla are referred together as the brainstem.
(a) Cerebellum
The cerebellum (small brain in Latin) is the part of the brain that functions in movement, co-ordination, motor control and sensory perception. It is responsible for relaying messages about posture, equilibrium, movement and fine motor skills such as writing or catching a ball.
One of the main manifestations of cerebellar dysfunction is problems with motor control. The ability for motor activity remains, but it loses precision, producing erratic, uncoordinated, or incorrectly timed movements. One such common problem is loss the of fine motor coordination called spasticity, a distinctive way of walking in which first one foot then the other is laboriously set forward. A standard test of cerebellar function is to reach with the tip of the finger for a target at arm’s length: A healthy person will move the fingertip in a rapid straight trajectory, whereas a person with cerebellar damage will reach slowly and erratically, with many mid-course corrections. Hence, scientists concluded that the basic function of the cerebellum is not to initiate movements, or to decide which movements to execute, but rather to control the detailed form of a movement.
The brain is composed of billions of neurons, but the cerebellum has the most neurons compared to any other part of the brain. Hence, when excessive alcohol abuse affects the brain, it is usually the cerebellum that is most affected. This is why alcohol related brain damage can cause permanent slurred speech, loss of balance or co-ordination.
Functional imaging studies have shown cerebellar activation in language, attention, and mental imagery activities. Other correlation studies have shown interactions between the cerebellum and non-motor areas of the cerebral cortex. The cerebellum also participates in error-correction and problem solving of many different types, including screening out incorrect responses by other brain systems. Various non-motor symptoms have been recognized in people with damage that appears to be confined to the cerebellum.
Dr. K. Doya (5) proposed that the cerebellum is involved in supervised learning, in contrast to the basal ganglia, which perform reinforcement learning, and the cerebral cortex, which performs unsupervised learning.
(b) Pons
In Latin, the word pons means bridge. It connects the cerebral cortex with the medulla and also serves as a communications and coordination center between the two hemispheres of the brain. The pons is an important sensory relay system that provides information to the cerebellum, cerebrum, and spinal cord. It provides input to the cerebellar cortex through the pontine nuclei, allowing the cerebellum to coordinate much of its control.
The pons also functions as a motor relay center, since many of the descending nerve fibers synapse in the pons. Hence, any injury to the pons may result in motor deficits.
The pons is also an important control center for respiration. The apneustic center, located in the lower pons, stimulates inspiration, while the pneumotaxic center, located in the upper pons, inhibits inspiration. Damage to the pneumotaxic center can result in prolonged and so a decrease in the respiratory rate.
The pons plays a role in Rapid Eye Movement (REM) sleep, arousal and sleep paralysis.
The pons contains several cranial nuclei: the trigeminal nerve sensory and motor nucleus (V), the motor nucleus for the trigeminal nerve (V), abducens nucleus (VI), the facial nerve nucleus (VII) and : vestibulocochlear nuclei (VIII). The functions of these nerves include sensory roles in hearing, equilibrium, taste, facial sensations; as well as motor roles in eye movement, facial expressions, chewing, swallowing, urination, and the secretion of saliva and tears. Thus, the pons also functions to relay information from the face, teeth, ear, and eyes and their subsequent adjustment.
(c) Medulla Oblongata (Medulla)
The medulla oblongata or simply the medulla controls autonomic functions such as breathing, digestion, heart and blood vessel function, vomiting, swallowing, coughing and sneezing. Motor and sensory neurons from the midbrain and forebrain travel through the medulla. It helps relay messages between various parts of the brain and the spinal cord and the coordination of body movements.
An important function of the medulla is to help control the heart rate. Two centers in the medulla help control the heart rate. The cardio-inhibitory center via the vagus nerve, causes the release of acetylcholine, which decreases the heart rate. The cardio-acceleratory center, via the accelerator nerve, causes the release of nor-epinephrine.
The Marrow (Sui), Brain (Danao) , Bones (Gu), Blood Vessels (Mai), Uterus (Zigong) and Gallbladder (Dan) all store Yin Essences but have the shape (hollow) of a Yang Organ. They store the Essence but do not excrete. Therefore, they are called Extraordinary Yang Organs (1, 2, 3).
The common characteristics of these organs are that they store some form of yin essence (Kidney Essence, Marrow or Blood) and they are all functionally, directly or indirectly, related to the Kidneys.
The Chinese medical concepts of the Extraordinary Organs will be discussed as well as their Western medical counterparts. Western organs are described by their pure morphological or substantial structure. Their function is obtained through the anatomic analysis of the organs. On the other hand, the Chinese Organs are described by concepts formed by centuries of observation of various functions of the body, external manifestations, the interrelation between the organs, connection with environment and vital substances. Each Chinese organ is defined by a non-overlapping set of physiological, mental and spiritual functions. For example, the Blood Vessels contain Blood; the Heart controls Blood and Houses the Mind.
The interested reader could do further research to relate exactly which parts of western organs correspond to the Chinese Organ function (4). For example, parts of the cerebral cortex function like the Heart (Mind). The free, smooth flow of Qi, controlled by the Liver, is required for smooth movements, which is a function of the cerebellum, discussed below.
1. Marrow (Sui)
Kidney Essence produces Marrow which fills and nourishes the Brain and spinal cord and forms the Bone Marrow. Simple Questions states that the Bones are the residence of Marrow and Chapter 34 says that if the Kidneys are deficient, Marrow cannot be abundant.
Western Concepts of Marrow
In western medicine the term marrow refers to soft, gelatinous tissues that fill the cavities of bones. There are two types of bone marrow: red marrow (medulla ossium rubra), consisting mainly of hematopoietic tissue, and yellow marrow (medulla ossium flava), comprised mainly of fat cells. Both types of bone marrow contain numerous blood vessels and capillaries.
Red blood cells, platelets, stem cells and most white blood cells originate in red marrow. At birth, all bone marrow is red. With age, more and more marrow is converted to the yellow type; only about half of adult bone marrow is red. Red marrow is found mainly in the flat bones, such as the pelvis, sternum, cranium, ribs, vertebrae and scapulae, and in the cancellous (“spongy”) material at the epiphyseal ends of long bones such as the femur and humerus.
The red bone marrow is a key element of the lymphatic system. Hematopoietic precursors from the bone-marrow, called thymocytes, mature into T-cells in the thymus gland. Once mature, T-cells emigrate from the thymus and constitute the peripheral T-cells of the adaptive immune system.
Yellow marrow is found in the medullary cavity, the hollow interior of the middle portion of long bones. In cases of severe blood loss, the body can convert yellow marrow back to red marrow to increase blood cell production.
Various diseases and drugs can affect the bone marrow. Malignancies, aplastic anemia, or infections such as tuberculosis can lead to a decreased production of blood cells and blood platelets. There are types of leukemia that are cancers of the hematologic progenitor cells in the bone marrow. Exposure to radiation or chemotherapy can kill many of the rapidly dividing cells of the bone marrow and so result in a depressed immune system. Many of the symptoms of radiation sickness are due to damage to the bone marrow cells.
A bone marrow aspiration is sometimes performed to diagnose diseases of the bone marrow. This typically involves using a hollow needle to acquire a sample of red bone marrow from the crest of the ilium under general or local anesthesia.
2. Brain (Danao)
Chapter 33 in the Miraculous Pivot states that the Brain is a Sea of Marrow. Its upper part lies beneath the scalp with vertex at Bahui (Du 20) and its lowest part at Fengfu (Du 16). Chapter 10 in Simple Questions says that the Marrow pertains to the Brain. The Du (Govening) Meridian ascends the spinal column and enters the Brain at Fengfu. Many acupoints of the Du Meridian are used for pathological conditions of the Brain.
In Simple Questions, says that the head is the residence of intelligence. This can be interpreted as stating that the Brain is related to thinking. the Miraculous Pivot states that deficiency of the Brain leads to vertigo and dizziness.
The Brain is functionally related to the Kidneys, since Marrow originates from the Kidneys. The Brain is nourished by the Heart, particularly Heart Blood. The Kidneys store Essence and the Heart governs Blood. If Essence and Blood are abundant, the Brain will be healthy, vision and hearing will be clear. Deficiency of Heart Blood and Kidney Essence can result in slow thinking, poor memory, low vitality and impaired sight and hearing. The interrelation of the Brain with the Kidney and Heart explains why in clinical practice symptoms such as poor memory and concentration, blurred vision and dizziness can result from a deficiency of the Kidney essence or Heart Blood.
The ancient Chinese doctors ascribed the functions of the Brain to various Organs, particularly, the Kidneys, Heart and Liver. Therefore, many syndromes and treatments of brain disorders are included in syndromes of the Organs.
Later, some of these functions of the Brain were ascribed to the brain itself. In the Ming Dynasty (1368-1644), Li Shizhen clearly indicated that the Brain is the palace of the Mind. During the Qing Dynasty (1644-1911), Wang Qingren’s book, “Revision of the Medical Classics” postulated that intelligence and memory rely on the brain. He stated that thinking, memory, smelling, vision, hearing and speaking are all functions of the brain.
Western Concepts of the Brain
The nervous system is composed of two parts. The central nervous system (CNS) consists of the brain and spinal cord. The peripheral nervous system is composed of cranial and spinal nerves, which carry impulses to and from the central nervous system. The cranial nerves handle head and neck sensory and motor activities, except the vagus nerve, which conducts signals to visceral organs. Each spinal nerve is attached to the spinal cord by a sensory and a motor root. These exit between the vertebrae and merge to form a large mixed nerve, whose branches supply a defined area of the body. The autonomic nervous system, sometimes considered as another division, is part central and part peripheral.
The brain is a complex organ which receives information from other parts of the body via the spinal cord and the peripheral nervous system. It uses this information to control basic life processes, like breathing, body temperature and blood pressure, as well as higher functions like creative thought and emotions.
The brain is comprised of two types of cells: nerve cells (neurons) and glial cells. Glial cells have multiple functions, which include structurally supporting neurons, repairing the CNS, and regulating the biochemical balance of the brain. The blood-brain-barrier is composed of astrocytes, a special type of glial cell. This barrier prevents many substances in the blood from entering the brain.
The brain is surrounded and protected by the rigid, bony skull and three membranes, called meninges. The tough, fibrous outer membrane is the dura mater. The archanoid, the intermediate membrane, is web-like. The pia mater is the innermost covering and is the most delicate. It is molded to the shape of the brain. The cerebrospinal fluid (CSF) surrounds the brain and spinal cord. It flows through open chambers in the brain, called ventricles, and out an opening to the spinal cord. The brain actually floats in the shock-absorbing CSF, and is thus protected from trauma. The CSF also brings nutrients to the brain and removes wastes.
The brain has 3 main parts: forebrain, midbrain and hindbrain, as shown in Fig. 1.
Forebrain (Prosencephalon)
The forebrain is the largest part of the brain, most of which is the cerebrum, consisting of the cerebral cortex, corpus striatum and olfactory bulb. The other major division of the forebrain is the diencephalon, which includes the hypothalamus, thalamus, epithalamus (including the pineal gland), and subthalamus.
Cerebrum
Cerebral Cortex
The outermost and top layer of the brain is the cerebral cortex. The cerebral cortex is composed of two similar halves called hemispheres, having different functions. The left side of the cerebral cortex controls the right side of the body and speech. The right side controls the left side of the body and the perception of spatial relationships, such as where one’s hand might be located in relation to the ground, without looking. There are individual variations, for example, the language center is on the right in 2 percent of right-handed people and also in about 50% of left-handed people
The hemispheres are separated by a deep groove, but are linked by the corpus callosum, anterior commissure, posterior commissure, and hippocampal commissure. All of these transfer the information between two hemispheres to coordinate functions.
The outer layer of the hemispheres is composed of gray matter, consisting of neuronal cell bodies. The inner core of the hemispheres is composed of white matter, consisting of axons of neurons. The cortex contains ridges (gyri) and valleys (sulci).
Figure 3
Lobes of the Hemispheres of the Brain
The cerebral cortex has association and motor areas. Association areas include the parietal, temporal, and occipital lobes, which are involved in producing perceptions, resulting from sensory organs and the frontal lobe (or prefrontal association complex); involved in movement and planning, as well as abstract thought. Motor areas are related to controlling voluntary movements. They are located in the frontal lobes. The primary motor cortex executes voluntary movements, while the premotor cortex selects the movement (with the aid of supplementary motor areas).
Some functions of the lobes appear in Table 1. All of the lobes also contain areas for which specialized functions have not yet been identified. These areas are known as the association cortex and are thought to be involved in complex, higher-level mental activity.
Functions of Lobes of the Brain
Corpus Striatum
The corpus striatum, or “striped body” consists of the basal ganglia (basal nucleus) and the internal capsule. The basal ganglia are composed of neurons and so are gray matter. The internal capsule is a group of tracts surrounded by myelinated axons and so appears white. The internal capsule runs between the caudate and lenticular nucleus of the basal ganglia and so the group of structures looks striped.
Figure 4
The Basal Ganglia
The basal ganglia consist of the caudate nucleus and the lenticular nucleus, which is divided into the putamen and the globus pallidus.
The components of the basal ganglia that control the motor functions are sometimes called the “extrapyramidal motor system.” Though the basal ganglia are important in motor and learning functions, it also plays a part in addictions and emotions.
The caudate nucleus is partitioned into a head, body and tail. It contains endorphins, which produce a positive emotional state.
The lenticular nucleus is also called the lentiform nucleus (lentiform means lens-shaped in Latin). The putamen is the most lateral part of the structure. Its main function of the putamen is to regulate movements and influence various types of learning and uses the neurotransmitter dopamine to perform its functions.
The globus pallidus, the more medial part of the lenticular nucleus, regulates movements which occur on the subconscious level. It has a primarily inhibitory action to balance the excitatory action of the cerebellum. These two systems are designed to work in harmony with each other to allow people to move smoothly. Imbalances can result in tremors, jerks, and other movement problems, as seen in patients with progressive neurological disorders with symptoms like tremors.
The amygdala, attached to the tail of the caudate nucleus, involved in emotions. It was once classified as part of the basal ganglia, but is now part of the limbic system.
The subthalamic nuclei and the substantia nigra are both functionally related to the basal ganglia.
Olfactory Bulb
The olfactory bulb is on the inferior (bottom) side of the brain as shown in Fig. 4.
It receives neural input about odors detected by cells in the nasal cavity. The axons of olfactory receptor (smell receptor) cells extend directly into the highly organized olfactory bulb, where information about odors is processed.
figure 5
Diencephalon
(a) Hypothalamus
This part of the brain regulates hunger, thirst, pain, pleasure, sexual satisfaction, anger, etc. It also regulates the parasympathetic and sympathetic, thus controlling blood pressure, heart rate, breathing, digestion, etc. It also stimulates the pituitary gland, is responsible for hormone levels, and so is important in regulating growth and metabolism.
(b) Thalamus
The thalamus translates signals from “pre-thalamic” inputs to cortex-readable signals. It also plays an important role in regulating states of sleep and wakefulness. Thalamic nuclei have strong reciprocal connections with the cerebral cortex, forming thalamo-cortico-thalamic circuits that are involved with consciousness. The thalamus plays a major role in regulating arousal, levels of awareness, and activity. Severe damage to this area causes permanent coma.
(c) Epithalamus
The epithalamus is a dorsal posterior segment of the diencephalon. It regulates the motor pathways and emotions. It is connected with the limbic system and basal ganglia.
The pineal gland is a small endocrine gland that is part of the epithalamus. Its shape resembles a tiny pine cone, hence its name. It produces melatonin, which affects the modulation of wake/sleep patterns and seasonal functions.
(d) Subthalamus
The major part of the subthalamus is the subthalamic nucleus (SNT). Functionally, it also encompasses the globus pallidus, which is part of the telencephalon. The function of the STN is unknown, but current theories place it as a component of the basal ganglia control system that may perform action selection. STN dysfunction has also been shown to increase impulsivity in individuals presented with two equally rewarding stimuli.
Midbrain (Mesencephalon)
The midbrain or mesencephalon is composed of the tectum, tegmentum, the ventricular mesocoelia and the cerebral peduncles, as well as several nuclei and fasciculi. Caudally the mesencephalon adjoins the pons (metencephalon) and rostrally it adjoins the diencephalon (thalamus, hypothalamus, etc.). The midbrain is located below the cerebral cortex, and above the hindbrain placing it near the center of the brain.
(a) Tectum
The tectum is located in the dorsal region of the mesencephalon. It consists of the superior colliculi (visual receptors) and inferior colliculi (auditory receptors) and is involved in controlling auditory and visual responses.
(b) Tegmentum
Tegmentum helps control motor functions, regulates awareness and attention. It also regulates some autonomic functions.
(c) Ventricular Mesocoelia
The ventricular mesocoelia, also known as the cerebral aqueduct, the iter or the aqueduct of Sylvius, connects the third and fourth ventricles of the brain.
(d) Cerebral Penduncles
The cerebral peduncles are two tracts underneath the tegmentum that are often considered part of the mesencephalon. These tracts are bundles of nerve fibers passing over the bottom of the brain that connect the cerebral hemispheres to the spinal cord.
Hindbrain (Rhombencephalon)
The hindbrain includes the cerebellum, the pons and the medulla oblongata, which function collectively to support vital bodily processes (Fig. 5). Often the midbrain, pons, and medulla are referred together as the brainstem.
(a) Cerebellum
The cerebellum (small brain in Latin) is the part of the brain that functions in movement, co-ordination, motor control and sensory perception. It is responsible for relaying messages about posture, equilibrium, movement and fine motor skills such as writing or catching a ball.
One of the main manifestations of cerebellar dysfunction is problems with motor control. The ability for motor activity remains, but it loses precision, producing erratic, uncoordinated, or incorrectly timed movements. One such common problem is loss the of fine motor coordination called spasticity, a distinctive way of walking in which first one foot then the other is laboriously set forward. A standard test of cerebellar function is to reach with the tip of the finger for a target at arm’s length: A healthy person will move the fingertip in a rapid straight trajectory, whereas a person with cerebellar damage will reach slowly and erratically, with many mid-course corrections. Hence, scientists concluded that the basic function of the cerebellum is not to initiate movements, or to decide which movements to execute, but rather to control the detailed form of a movement.
The brain is composed of billions of neurons, but the cerebellum has the most neurons compared to any other part of the brain. Hence, when excessive alcohol abuse affects the brain, it is usually the cerebellum that is most affected. This is why alcohol related brain damage can cause permanent slurred speech, loss of balance or co-ordination.
Functional imaging studies have shown cerebellar activation in language, attention, and mental imagery activities. Other correlation studies have shown interactions between the cerebellum and non-motor areas of the cerebral cortex. The cerebellum also participates in error-correction and problem solving of many different types, including screening out incorrect responses by other brain systems. Various non-motor symptoms have been recognized in people with damage that appears to be confined to the cerebellum.
Dr. K. Doya (5) proposed that the cerebellum is involved in supervised learning, in contrast to the basal ganglia, which perform reinforcement learning, and the cerebral cortex, which performs unsupervised learning.
(b) Pons
In Latin, the word pons means bridge. It connects the cerebral cortex with the medulla and also serves as a communications and coordination center between the two hemispheres of the brain. The pons is an important sensory relay system that provides information to the cerebellum, cerebrum, and spinal cord. It provides input to the cerebellar cortex through the pontine nuclei, allowing the cerebellum to coordinate much of its control.
The pons also functions as a motor relay center, since many of the descending nerve fibers synapse in the pons. Hence, any injury to the pons may result in motor deficits.
The pons is also an important control center for respiration. The apneustic center, located in the lower pons, stimulates inspiration, while the pneumotaxic center, located in the upper pons, inhibits inspiration. Damage to the pneumotaxic center can result in prolonged and so a decrease in the respiratory rate.
The pons plays a role in Rapid Eye Movement (REM) sleep, arousal and sleep paralysis.
The pons contains several cranial nuclei: the trigeminal nerve sensory and motor nucleus (V), the motor nucleus for the trigeminal nerve (V), abducens nucleus (VI), the facial nerve nucleus (VII) and : vestibulocochlear nuclei (VIII). The functions of these nerves include sensory roles in hearing, equilibrium, taste, facial sensations; as well as motor roles in eye movement, facial expressions, chewing, swallowing, urination, and the secretion of saliva and tears. Thus, the pons also functions to relay information from the face, teeth, ear, and eyes and their subsequent adjustment.
(c) Medulla Oblongata (Medulla)
The medulla oblongata or simply the medulla controls autonomic functions such as breathing, digestion, heart and blood vessel function, vomiting, swallowing, coughing and sneezing. Motor and sensory neurons from the midbrain and forebrain travel through the medulla. It helps relay messages between various parts of the brain and the spinal cord and the coordination of body movements.
An important function of the medulla is to help control the heart rate. Two centers in the medulla help control the heart rate. The cardio-inhibitory center via the vagus nerve, causes the release of acetylcholine, which decreases the heart rate. The cardio-acceleratory center, via the accelerator nerve, causes the release of nor-epinephrine.
Bud
very nice information. Thank you for increasing my knowledge about brain activities ..
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Andy
NitroTek
You are welcome
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