Nerve impulses originating in the receptors for touch, pressure, heat and cold travel to the sensory cortex, where it triggers feelings itself.
The areas of the body are more sensitive, have a wider region of cortex mapped. Biologists have shown, schematically, each region of the body in relation to the amount of cerebral cortex allocated. The drawing is obtained, called the sensory homunculus. Those areas that are seen larger, as the face and extremities are the most sensitive areas.
Nerve impulses generated in the receptors travel in nerve bundles located in different areas of the spinal cord, forming the spinothalamic pathway and route of Goll and Burdach.
a. Via spinothalamic: it leads to pain and temperature information from cutaneous receptors.
It consists of 3 neurons, the first synapses in the spinal ganglion and synapses with the second neuron. Neuron fibers cross to the opposite side of the cord and ascends in the spinothalamic to the thalamus, where it synapses with the third neuron that reaches the sensory cortex.
b. Route of Goll and Burdach. This pathway transmits the impulses related to the perception of light touch and pressure. It comprises three neurons. The first enters the spinal cord and its axon ascends through the posterior columns of the same side of the body formed by the beam or gracilis Goll and Burdach beam or cuneatus. Synapses in the bulb with the second neuron, whose axon crosses to the opposite side and reaches the thalamus, where it synapses with the third neuron, which carries the information to the sensory cortex.
The motor homunculus is proportional representation of each region of the body depending on the amount of assigned motor cortex. The areas that have greater cortical representation are those that require a more precise engine control, such as: hands, fingers and tongue.
Once generated motor responses, nerve impulses travel from the motor cortex to the spinal cord, through which descending through the pyramidal and extrapyramidal pathways.
a) Ways pyramid: the fibers which constitute these pathways arise from the frontal lobe and descend to the cranial nerve nuclei or anterior horn of the spinal cord. The fiber for which impulses travel can be crossed to the opposite side, forming the decussation at the pyramids, other neurons synapse with association and cross to the opposite side of the cord. 3 beams are distinguished mainly: crossed pyramidal tract, direct pyramidal tract and corticobulbar beam.
b) Inland Extrapyramidal Its fibers are initiated in the motor cortex and then continue to the basal ganglia. There are three bundles Extrapyramidal the rubrospinal, and vestibulospinal tectospinal. The first cone l transmits impulses related muscle tone and posture of the skeletal muscles, the latter conducts impulses that control a series of head movements that respond to visual stimuli and the third is involved in balance control, since it regulates muscle tone in response to head movements.
The simple task of taking an object requires the integration of information coming from these receptors d, development of a motor response and the contraction and relaxation of specific muscles. This underlines the great functional integration between the different structures of the nervous system.
Spinal nerves (leave the spinal cord) There are 31 pairs of spinal nerves:
8 pairs of spinal nerves ciliary (C1-C8) .12 pairs of thoracic spinal nerves (T1-T12), 5 pairs of lumbar spinal nerves (L1-L5)
5 pairs of sacral spinal nerves (S1-S5), 1 pair of coccygeal spinal nerves (Co)
Cornea, pupil, aqueous humor, vitreous (hyaloid canal), retina, optic nerve, visual cortex (occipital lobe)