The motor system is the set of central and peripheral structures in the nervous system that support motor functions, i.e. movement. Peripheral structures may include skeletal muscles and neural connections with muscle tissues. Central structures include cerebral cortex, brainstem, spinal cord, pyramidal system including the upper motor neurons, extrapyramidal system, cerebellum, and the lower motor neurons in the brainstem and the spinal cord.
The brainstem 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.
In neuroanatomy, the lateral geniculate nucleus is a structure in the thalamus and a key component of the mammalian visual pathway. It is a small, ovoid, ventral projection of the thalamus where the thalamus connects with the optic nerve. There are two LGNs, one on the left and another on the right side of the thalamus. In humans, both LGNs have six layers of neurons alternating with optic fibers.
In anatomy, the extrapyramidal system is a part of the motor system network causing involuntary actions. The system is called extrapyramidal to distinguish it from the tracts of the motor cortex that reach their targets by traveling through the pyramids of the medulla. The pyramidal tracts may directly innervate motor neurons of the spinal cord or brainstem, whereas the extrapyramidal system centers on the modulation and regulation of anterior (ventral) horn cells.
In neuroanatomy, a neural pathway is the connection formed by axons that project from neurons to make synapses onto neurons in another location, to enable neurotransmission. Neurons are connected by a single axon, or by a bundle of axons known as a nerve tract, or fasciculus. Shorter neural pathways are found within grey matter in the brain, whereas longer projections, made up of myelinated axons, constitute white matter.
The pyramidal tracts include both the corticobulbar tract and the corticospinal tract. These are aggregations of efferent nerve fibers from the upper motor neurons that travel from the cerebral cortex and terminate either in the brainstem (corticobulbar) or spinal cord (corticospinal) and are involved in the control of motor functions of the body.
The paraventricular nucleus of hypothalamus is a nucleus in the hypothalamus, that lies next to the third ventricle. Many of its neurons project to the posterior pituitary where they secrete oxytocin, and a smaller amount of vasopressin. Other secretions are corticotropin-releasing hormone (CRH) and thyrotropin-releasing hormone (TRH). CRH and TRH are secreted into the hypophyseal portal system, and target different neurons in the anterior pituitary. Dysfunctions of the PVN can cause hypersomnia in mice. In humans, the dysfunction of the PVN and the other nuclei around it can lead to drowsiness for up to 20 hours per day. The PVN is thought to mediate many diverse functions through different hormones, including osmoregulation, appetite, wakefulness, and the response of the body to stress.
The reticular formation is a set of interconnected nuclei in the brainstem that spans from the lower end of the medulla oblongata to the upper end of the midbrain. The neurons of the reticular formation make up a complex set of neural networks in the core of the brainstem. The reticular formation is made up of a diffuse net-like formation of reticular nuclei which is not well-defined. It may be seen as being made up of all the interspersed cells in the brainstem between the more compact and named structures.
The rubrospinal tract is one of the descending tracts of the spinal cord. It is a motor control pathway that originates in the red nucleus. It is a part of the lateral indirect extrapyramidal tract.
The globose nucleus is one of the deep cerebellar nuclei. It is located medial to the emboliform nucleus, and lateral to the fastigial nucleus. The globose nucleus and emboliform nucleus are known collectively as the interposed nuclei.
Decerebration is the elimination of cerebral brain function in an animal by removing the cerebrum, cutting across the brain stem, or severing certain arteries in the brain stem.
The zona incerta (ZI) is a horizontally elongated small nucleus that separates the larger subthalamic nucleus from the thalamus. Its connections project extensively over the brain from the cerebral cortex down into the spinal cord.
The lateral reticular nucleus, of the lateral funiculus, can be divided into three subnuclei, the parvocellular, magnocellular and the subtrigeminal. As is typical of the reticular formation, none of these are very distinct subnuclei, but rather blurred distinctions between cell types and location. The lateral reticular nucleus sends all of its projections to the cerebellum.
The rubro-olivary tract is a tract which connects the inferior olivary nucleus, and the parvocellular red nucleus.
The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal cord is hollow and contains a structure called the central canal, which contains cerebrospinal fluid. The spinal cord is also covered by meninges and enclosed by the neural arches. Together, the brain and spinal cord make up the central nervous system.
The primary motor cortex 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.
The magnocellular red nucleus is located in the rostral midbrain and is involved in motor coordination. Together with the parvocellular red nucleus, the mRN makes up the red nucleus. Due to the role it plays in motor coordination, the magnocellular red nucleus may be implicated in the characteristic symptom of restless legs syndrome (RLS). The mRN receives most of its signals from the motor cortex and the cerebellum.
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 mesencephalic locomotor region (MLR) is a functionally defined area of the midbrain that is associated with the initiation and control of locomotor movements in vertebrate species.
