For a better understanding of the nervous system diagram , we divide it into two parts:
- Central Nervous System
- Peripheral Nervous System
CENTRAL NERVOUS SYSTEM
Location: Are those structures that are housed in the skull and spine, which act as protection.
- Brain (housed in the skull)
- Spinal cord (housed in the spine)
It is subdivided into:
I) Brain externally can describe as follows:
Great nervous mass
2. Protected by a membrane called meninges (dura, arachnoid and pia mater (among the latter runs the cerebrospinal fluid)
3. It has a large central sulcus, which divides the brain into two Right Hemisphere and Left Hemisphere, these two hemispheres are joined by transverse fibers (corpus callosum)
4. Also seen on its surface folds or sulci, two fairly notorious
5. The latter fissures and other divide the brain into lobes: frontal, parietal, temporal and occipital lobes, associated with movement, sensation, hearing and vision respectively.
It presents internally brain cell nuclei (cell bodies of neurons):
a.- basal ganglia, related to the movement
b.- thalamus, which acts of way station for feelings
c.- Hypothalamus and Pituitary related to the autonomic system (sympathetic and parasympathetic) and the Endocrine System
II) Cerebellum, having the form as butterfly fissures that divide it into a series of lobes are also observed.
The cerebellum it is divided into three parts: Arquicerebelo (related to equilibrium), Palliocerebelo (related to muscle tone) and neocerebellum (related to the coordinated movement).
III) Brainstem, is presented as a spinal cord widened then it are the ascending, descending nerve bundles and a number of cell nuclei. Are also a number of nuclei called reticular formation, related to states of excitation and inhibition of movement and control of sleep and wakefulness.
The brain stem is divided into three parts:
1. midbrain, is the most anterior part of the trunk. In it we find relay nuclei of auditory and visual pathways (colliculi), just as nuclei for eye movements; and nuclei associated with movement (red nucleus and substantia nigra).
2. Pons, it found cranial nerve nuclei related to facial expression, chewing, relay nuclei for hearing and nuclei involved in breathing.
3. The medulla, many cranial nerves have their entry and exit in the bulb also has several autonomous functions related to core (breathing, heart rate and movements associated with coughing, vomiting, sneezing).
By their appearance we can say that the spinal cord is an elongated cylindrical mass, also covered by a protective membranes (meninges), in the lower part observed a nerve fiber series, which together form the “ponytail”.
It is noteworthy that the bone is not full extension of the spine, up to the level of the lumbar vertebra 2 and is fixed to the coccyx through meningeal extension called “filum terminale”.
As to its internal structure, the cell bodies forming cores are located in the central part (gray matter) and are surrounded by ascending and descending nerve fibers (white matter).
Its role focuses on driving nerve impulses to the brain and it responses to the muscles (striated / smooth) and glands; and is also the center of reflex actions.
PERIPHERAL NERVOUS SYSTEM
Comprised of nerve fibers found outside the spinal cord, thus we find afferents (Estrada) and efferent fibers (outgoing). The afferent pathway enters the cord by the postero-lateral part and efferent pathway emerges from the anterolateral part.
Afferents are related to somato-sensory and viscero-sensory inputs (Autonomous System).
Efferent pathways are related to somatosensory and motor responses viscero-motor (Autonomous System).
Autonomic Nervous System, is involved in structures such as smooth muscle, cardiac muscle and glands, controlling and regulating the activity of these.
The autonomic system has two parts: the sympathetic system and the parasympathetic system, the activity of these systems contrasts, such as the sympathetic increases heart rate, dilates the pupil and inhibits stomach activity; the parasympathetic slows the heart rate, constricts the pupil, stimulates stomach activity.
Otherwise; in the body in states of rest, parasympathetic activity predominates, unlike in the states of alert predominant sympathetic activity.