|
Primary Motor Cortex
The primary motor cortex ( Brodmann area 4) is a brain region that in humans is located in the dorsal portion of the frontal lobe. It is the primary region of the motor system and works in association with other motor areas including premotor cortex, the supplementary motor area, posterior parietal cortex, and several subcortical brain regions, to plan and execute voluntary movements. Primary motor cortex is defined anatomically as the region of cortex that contains large neurons known as Betz cells, which, along with other cortical neurons, send long axons down the spinal cord to synapse onto the interneuron circuitry of the spinal cord and also directly onto the alpha motor neurons in the spinal cord which connect to the muscles. At the primary motor cortex, motor representation is orderly arranged (in an inverted fashion) from the toe (at the top of the cerebral hemisphere) to mouth (at the bottom) along a fold in the cortex called the central sulcus. However, some body p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brodmann Area 4
Brodmann area 4 refers to the primary motor cortex of the human brain. It is located in the posterior portion of the frontal lobe. Brodmann area 4 is part of the precentral gyrus. The borders of this area are: the precentral sulcus in front (anteriorly), the medial longitudinal fissure at the top ( medially), the central sulcus in back (posteriorly), and the lateral sulcus along the bottom (laterally). This area of cortex, as shown by Wilder Penfield and others, has the pattern of a homunculus. That is, the legs and trunk fold over the midline; the arms and hands are along the middle of the area shown here; and the face is near the bottom of the figure. Because Brodmann area 4 is in the same general location as primary motor cortex, the homunculus here is called the motor homunculus. The term area 4 of Brodmann-1909 refers to a cytoarchitecturally defined portion of the frontal lobe of the guenon. It is located predominantly in the precentral gyrus. Brodmann-1909 re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Motor Cortex
The motor cortex is the region of the cerebral cortex involved in the planning, motor control, control, and execution of voluntary movements. The motor cortex is an area of the frontal lobe located in the posterior precentral gyrus immediately anterior to the central sulcus. Components The motor cortex can be divided into three areas: 1. The primary motor cortex is the main contributor to generating neural impulses that pass down to the spinal cord and control the execution of movement. However, some of the other motor areas in the brain also play a role in this function. It is located on the anterior paracentral lobule on the medial surface. 2. The premotor cortex is responsible for some aspects of motor control, possibly including the preparation for movement, the sensory guidance of movement, the spatial guidance of reaching, or the direct control of some movements with an emphasis on control of proximal and trunk muscles of the body. Located anterior to the primary mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Medulla Oblongata
The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (involuntary) functions, ranging from vomiting to sneezing. The medulla contains the cardiovascular center, the respiratory center, vomiting and vasomotor centers, responsible for the autonomic functions of breathing, heart rate and blood pressure as well as the sleep–wake cycle. "Medulla" is from Latin, ‘pith or marrow’. And "oblongata" is from Latin, ‘lengthened or longish or elongated'. During embryonic development, the medulla oblongata develops from the myelencephalon. The myelencephalon is a secondary brain vesicle which forms during the maturation of the rhombencephalon, also referred to as the hindbrain. The bulb is an archaic term for the medulla oblongata. In modern clinical usage, the word bulbar (as in bulbar palsy) is r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lower Motor Neuron
Lower motor neurons (LMNs) are motor neurons located in either the anterior grey column, anterior nerve roots (spinal lower motor neurons) or the cranial nerve nuclei of the brainstem and cranial nerves with motor function (cranial nerve lower motor neurons). Many voluntary movements rely on spinal lower motor neurons, which innervate skeletal muscle fibers and act as a link between upper motor neurons and muscles. Cranial nerve lower motor neurons also control some voluntary movements of the eyes, face and tongue, and contribute to chewing, swallowing and vocalization. Damage to lower motor neurons often leads to hypotonia, hyporeflexia, flaccid paralysis as well as muscle atrophy and fasciculations. Classification Lower motor neurons are classified based on the type of muscle fiber they innervate: * Alpha motor neurons (α-MNs) innervate extrafusal muscle fibers, the most numerous type of muscle fiber and the one involved in muscle contraction. * Beta motor neurons (β-M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cranial Nerve
Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and from regions of the head and neck, including the special senses of vision, taste, smell, and hearing. The cranial nerves emerge from the central nervous system above the level of the first vertebra of the vertebral column. Each cranial nerve is paired and is present on both sides. There are conventionally twelve pairs of cranial nerves, which are described with Roman numerals I–XII. Some considered there to be thirteen pairs of cranial nerves, including the non-paired cranial nerve zero. The numbering of the cranial nerves is based on the order in which they emerge from the brain and brainstem, from front to back. The terminal nerves (0), olfactory nerves (I) and optic nerves (II) emerge from the cerebrum, and the remaining ten pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brainstem
The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is continuous with the thalamus of the diencephalon through the tentorial notch, and sometimes the diencephalon is included in the brainstem. The brainstem is very small, making up around only 2.6 percent of the brain's total weight. It has the critical roles of regulating heart and respiratory system, respiratory function, helping to control heart rate and breathing rate. It also provides the main motor and sensory nerve supply to the face and neck via the cranial nerves. Ten pairs of cranial nerves come from the brainstem. Other roles include the regulation of the central nervous system and the body's sleep cycle. It is also of prime importance in the conveyance of motor and sensory pathways from the rest of the brain to the body, and from the b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internal Capsule
The internal capsule is a paired white matter structure, as a two-way nerve tract, tract, carrying afferent nerve fiber, ascending and efferent nerve fiber, descending axon, fibers, to and from the cerebral cortex. The internal capsule is situated in the Anatomical terms of location#Medial and lateral, inferomedial part of each cerebral hemisphere of the brain. It carries information past the subcortical basal ganglia. As it courses it separates the caudate nucleus and the thalamus from the putamen and the globus pallidus. It also separates the caudate nucleus and the putamen in the dorsal striatum, a brain region involved in motor and reward pathways. The internal capsule is V-shaped in transection forming an anterior and posterior limb, with the angle between them called the genu. The corticospinal tract constitutes a large part of the internal capsule, carrying motor information from the primary motor cortex to the lower motor neurons in the spinal cord. Above the basal gangli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White Matter
White matter refers to areas of the central nervous system that are mainly made up of myelinated axons, also called Nerve tract, tracts. Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distribution of action potentials, acting as a relay and coordinating communication between different brain regions. White matter is named for its relatively light appearance resulting from the lipid content of myelin. Its white color in prepared specimens is due to its usual preservation in formaldehyde. It appears pinkish-white to the naked eye otherwise, because myelin is composed largely of lipid tissue veined with capillaries. Structure White matter White matter is composed of bundles, which connect various grey matter areas (the locations of nerve cell bodies) of the brain to each other, and carry nerve impulses between neurons. Myelin acts as an insulator, which allows saltatory conduction, electrical signals to jump, rather than cour ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corticospinal Tract
The corticospinal tract is a white matter motor pathway starting at the cerebral cortex that terminates on lower motor neurons and interneurons in the spinal cord, controlling movements of the limbs and trunk. There are more than one million neurons in the corticospinal tract, and they become myelinated usually in the first two years of life. The corticospinal tract is one of the pyramidal tracts, the other being the corticobulbar tract The corticobulbar (or corticonuclear) tract is a two-neuron white matter motor pathway connecting the motor cortex in the cerebral cortex to the Medullary pyramids (brainstem), medullary pyramids, which are part of the brainstem's medulla oblonga .... Anatomy The corticospinal tract originates in several parts of the brain, including not just the motor areas, but also the primary somatosensory cortex and premotor areas. Most of the neurons originate in either the primary motor cortex (precentral gyrus, Brodmann area 4) or the premotor fron ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lower Motor Neurons
Lower motor neurons (LMNs) are motor neurons located in either the anterior grey column, anterior nerve roots (spinal lower motor neurons) or the cranial nerve nuclei of the brainstem and cranial nerves with motor function (cranial nerve lower motor neurons). Many voluntary movements rely on spinal lower motor neurons, which innervate skeletal muscle fibers and act as a link between upper motor neurons and muscles. Cranial nerve lower motor neurons also control some voluntary movements of the eyes, face and tongue, and contribute to chewing, swallowing and vocalization. Damage to lower motor neurons often leads to hypotonia, hyporeflexia, flaccid paralysis as well as muscle atrophy and fasciculations. Classification Lower motor neurons are classified based on the type of muscle fiber they innervate: * Alpha motor neurons (α-MNs) innervate extrafusal muscle fibers, the most numerous type of muscle fiber and the one involved in muscle contraction. * Beta motor neurons (β-MN ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cranial Nerves
Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and from regions of the head and neck, including the special senses of Visual perception, vision, taste, Olfaction, smell, and hearing. The cranial nerves emerge from the central nervous system above the level of the Atlas (anatomy), first vertebra of the vertebral column. Each cranial nerve is paired and is present on both sides. There are conventionally twelve pairs of cranial nerves, which are described with Roman numerals I–XII. Some considered there to be thirteen pairs of cranial nerves, including the non-paired cranial nerve zero. The numbering of the cranial nerves is based on the order in which they emerge from the brain and brainstem, from front to back. The terminal nerves (0), olfactory nerves (I) and optic nerves (II) emerge f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Axons
An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see spelling differences) is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action potentials away from the nerve cell body. The function of the axon is to transmit information to different neurons, muscles, and glands. In certain sensory neurons ( pseudounipolar neurons), such as those for touch and warmth, the axons are called afferent nerve fibers and the electrical impulse travels along these from the periphery to the cell body and from the cell body to the spinal cord along another branch of the same axon. Axon dysfunction can be the cause of many inherited and acquired neurological disorders that affect both the peripheral and central neurons. Nerve fibers are classed into three types group A nerve fibers, group B nerve fibers, and group C nerve fibers. Groups A and B are myelinated, and group C are unmyelina ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
