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Conducting pathways of exteroreceptive and proprioreceptive sense. Conducting pathways of pain, temperature sensation. Tactile and pressure.353P2 Muscles and joints sense

Receptors appreciating stimuli outside the body are called exteroreceptors. In the early evolutional stages they were located mainly in the outer body coverings, which was necessary for perception of external stimuli, derived from ectoderm. Then exteroreceptors of vital importance developed and more complexed and acquire structure of special organs which could appreciate stimuli from a source at some distance from the body- they are distance receptors as sound, light, taste, olfaction. The conducting pathways from receptors of internal stimuli divided to motor apparatus, i.e.interoreceptors. Secondary subconscious impulses from the motor apparatus(bones. Joints. Muscles. tendons) reach the cerebellum through spinal, proprioceptive pathways. The most important among which are the anterior and posterior spinocerebellar tracts. The afferent fibers of the skin analyser bring to the cerebral cortx tctile stimuli and the sense of stereognosis, pain and thermal stimulations. Conducting pathways of pain, temperature sensation. The cell body of the first neuron is in the spinal ganglion whose cells are connected by peripheral processes with the skin and by central processes with the posterior horns of the spinal cord(nuclei propria) in which the cell body of the 2-nd neuron (gangl tract) is situated. The axon of the 2-nd neuron passes to the opposite side as a component of the white commissure and ascenders in the lateral spinothalamic tract to the thalamus.It should be pointed out because they are separates into 2: anterior-conducting the sense of pain, post- conveying temperature sense, the thalamus contain the cortical end of the skin analyzer. Pain and temp r impulses from the head are conveyed by the corresponding cranial nerves(5,7,9,10).Fibers of 2-nd neuron of the conducting pathway extend from exterorec. Cross to the other side. The impulses of pain. Temp. partly those of tactile sense are brought to the postcentrl gyrus from the opposite side. Pain and temp sense is disturbed on the contralateral to the affection when damage occurs to the second neuron above the crossing or if 3-rd neuron is damaged. The sense of Touch. The ganglio-pino-thalamo-cortical tract. The receptor is in the skin. The conductor consist of 3 neurons. Cell body of 1^st-in spinal ganglion. It is aggregation of perif.neurons, which concerned with all types of sensitivity. This neuron divides into 2: 1-st peripheral runs in skin nerve to the receptor, 2-central pass to the post.funiculi of spinal cord and separates into ascending and descending parts.The terminal ending part of this fibers in post.horns of s.cord in substantia gelatinosa(tractus gangliospinal tract.) Ascend.fiber pass to the post.funiculi-faciculus gracilis and fac.cutaneus in medulla oblongata(gangliobulbar tr). 2-nd neuron is nuclei of the medulla oblongata and reach the thalamus along the bulbothalamic tract. On the way it establish connection with motor nuclei of the brain stem and cranial nerves along which head refl. Occur in stimulation of skin, skin of hand, movement of eye. 3-rd neuron in thalamus. The axons of this n. extend in thalamocortical tract to the cerebral cortex into the postcentral gyrus and sup.parietal lobe, where cortical end of skin analyses is situated. Muscles and joints sense - Sensory subconscious impulses from the motor apparatus (bones, joints, muscles and tendons) reach the cerebellum through spinal, proprioceptive pathways, the most important are ant.(Fleching’s) and post.(Gowers’) Spinocerebellar tract. In addition nuclei gracilis and cutaneous located in med.oblong. also send proprioceptive imp. To the cerebellum. The processes of cells lodged in these nuclei reach the cerebellum through its inf.peduncules. All pathways conveying deep sense terminate n vermis, old part of cerebellum.

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