THE NERVOUS SYSTEM (SYSTEMA NERVOSUM) THE FUNCTIONS OF THE NERVOUS SYSTEM •control function •The neural control of the activity of the organs •The basical property is the excitability and the generating of electric nerve impulses The nerve cell (neuron) • the basic component of the nervous system • highly specialized (excitability, conductivity) Glial cell (neuroglia) • support, nutritive, defensive and other functions Neuron 1. the body (perikaryon) 2. the projections •dendrites: receiving of complaints •Axon (nerve fibre): conducts electrical impulses away from the neuron's cell body The types of the neurons •Multipolar: the largest ones, several dendrites and one axon, star-shaped, 80% •Pseudounipolar dendrite + axon - dendraxon, T-shaped, central and peripheral branch (spinal ganglions and ganglions of cranial nerves) • •Unipolar only one projection - axon (primary sensory cells, olfactory cells, rods and cones of the retina) • • • • • • • •Bipolar one axon and one dendrite, (the second neuron of the optic tract) • The synapse (a part of axon) •Ended by enlargement– terminal button – is in contact with other neuron – the connection synapse (muscle – neuromuscular junction) •presynaptic membrane, postsynaptic membrane •Transfer of impulse– spread through axon centrifugally as electric signal – action potential •terminal button – vesicles with neurotransmitters The neuromuscular junction Neuroglia •Astrocytes: the largest ones • long unbranched cellular processes (with vascular feet), which cover all vessels of CNS – blood-brain barrier •Oligodendrocytes: within the grey and white matter, they myelinate nerve fibres of CNS (nutrition, homeostasis) •Microglia: the smallest ones (primarilly within the bone marrow) • defense function – ability of phagocytosis) •Ependymal cells: they cover the central canal of spinal cord and the brain ventricles –they are bathed by the cerebrospinal fluid and they help its flow Neuroglia Function: they accelerate the conduction of the excitement, nutrition, homeostasis, defence function The myelin sheath CNS: oligodendroglia PNS: Schwann cells •insulator, it is interrupted by the nodes of Ranvier, the neural impulses ,,jump´´ •Myelinized nerve fibres - quicker transmission of the impulse The bodies of the neurons: ganglions, grey matter of CNS The projections of the neurons: white matter of CNS, nerves of PNS THE DIVISION OF THE NERVOUS SYSTEM •1. central nervous system (systema nervosum centrale) •Spinal cord (medulla spinalis) •brain (encephalon, cerebrum) •The hind-brain (rhombencephalon) •The Medulla oblongata(medulla oblongata) •The pons (pons Varoli) •The cerebellum (cerebellum) •The midbrain (mesencephalon) •The fore-brain (prosencephalon) •The diencephalon (diencephalon) •The cerebrum (telencephalon) •2. peripheral nervous system (systema nervosum periphericum) •It connects CNS with the periphery of organism (centripetally, centrifugally) •Spinal nerves (nervi spinales) •Cranial nerves (nervi craniales) • •sympathicus (pars sympathica) •parasymphaticus (pars parasympathica) Cerebrospinal nerves Autonomic nerves The terms: •funiculus = cord – x •fasciculus = bundle of axons -HETEROGENEOUS structure, it originates within the different nuclei of the grey matter and creates synapses also within the different structures x •tractus = tract – bundle of axons - HOMOGENOUS structure, the fibres have a common origin and end •rostral The nervous system 1) It mediates relations between external environment and organism 2) It provides body´s response to stimuli from outside 3) It mediates relations between all parts of organism 4) It provides integrality of all actions within organism FUNCTIONAL TYPES OF AXONS WITHIN PNS somatomotor striated muscle branchiomotor striated muscle visceromotor Smooth muscle myocardium glands parasympathetic sympathetic somatosensory Skin perception, proprioception, pain viscerosensory mechanoception, pain senzory taste, hearing and vestibular informations, THE REFLEX ARC •The reflex is a fyziologic action, whose essence is the response of the organism to the change of the external or the internal environment- this is a response of the organism to the irritation. • The nervous system constantly monitors the conditions of the external and internal environment of the organism using the receptors, it processes these informations within CNS and gives off the instructions for the executive organs – effectors = REFLEX •The anatomical underlay of the reflex is the reflex arc – a system of the neural tracts, on which is the reflex carried out. • •1. Receptors •2. Afferent neural tracts •3. CNS •4. Efferrent neural tracts •5. Effectors RECEPTORS •Receptor (sensor): responds to the changes of the internal or external environment of the organism and it converts them into action potential of the neural impulses, these impulses are emited into directing centre within CNS • •The division according to the location: •exteroreceptors – receptors, which respond to the stimuli (changes) from the external environment of the organism •interoreceptors – receptors, which respond to the stimuli (changes) from the internal environment of the organism •According to the specific location: •proprioreceptors – receptors which are located within the locomotor system (within the muscles, tendons and articular capsules) •visceroreceptors – receptors which are located within the visceral organs and the walls of the vessels •The division according to the physical character of the acting stimulus •mechanoreceptors – receptors reponding to mechanical stimuli •chemoreceptors – receptors reponding to chemical stimuli •thermoreceptors – receptors reponding to thermal stimuli •photoreceptors – receptors reponding to light stimuli • •The special case present so called algoreceptors – receptors which respond to pain. The muscles •Muscle and tendon spindles (intrafusal fibres) – degree of contraction and tension of the muscle fibers •Free nerve ending around the muscle fibers - pain The afferent nerve pathways •The afferent (centripetal, sensory) pathways conduct the neural impulses from the receptors into CNS. • They are formed by the projections of sensory neurons, whose bodies are located out of CNS within sensory ganglions. The afferent pathways are divided into: Somatosensory pathways – bring information from receptors within skin and locomotor system Viscerosensory pathways – bring informations from visceroreceptors (from visceral organs) Sensory pathways – bring informations from sensors – specialized sensory organs (visual, auditory, vestibular, olfactory and gustatory sytems) THE CENTRAL NERVOUS SYSTEM •The central nervous system (CNS) is the directing centre of the nervous system. It takes the informations from the receptors using the afferent nerve pathways. It processes and evaluates these informations and provides the responses of the organism using the efferent nerve pathways and effectors. • •The nervous tissue of CNS is formed by two types of the matter: •The grey matter (substantia grisea) •The white matter(substantia alba) The grey matter (substantia grisea): •is formed by the bodies and dendrites of the neurons + glial cells •The bodies of the neurons take the informations from axons of sensory neurons of the sensory ganglions and give off the new informations for motor neurons within CNS •On the connection between sensory and motor neurons may not be any other switching neuron (by the simpliest reflexes), but usually there are one ore more switching neurons, so called interneurons, inserted The white matter (substantia alba): •Is formed by the bundles of myelinized axons of neurons, which are located within the grey matter and provide the communication between the neurons of the grey matter •Association pathways •Commissural pathways •Projection pathways – according to the direction, we divide them into two groups: •Ascending tracts – tracts passing from the lower centre toward the higher one. They are the continuation of the afferent peripheral tracts. •Descending tracts – tracts passing from the higher centre toward the lower one. They are the continuation of the efferent peripheral tracts • The efferent nerve pathways •The efferent, centrifugal, motor) nerve pathways: •They lead the nervous impulses from CNS into effectors (executive organs) •They begin with the motor neuron within CNS, axon of this neuron leaves CNS and presents the proper efferent (motor) pathway •Somatomotor pathways •Visceromotor pathways Effectors are the executive organs or tissues, which provide the proper response of the organism to the irritation. They can be: Muscle cells– the result of the reflexu is the motion Glandular cells– the result of the reflexu is the secretion EFFECTORS THE PERIPHERAL NERVOUS SYSTEM (systema nervosum periphericum) •The periphery nervous system is formed by a system of nerves and ganglions, which convey reversible transfer of the informations between CNS and the periphery (skin, locomotor system and visceral organs) •Nerve is consist of nerve fibres and fibrous connective tissue •Nerve fibres are myelinated (white) or unmyelinated (grey) projections of the neurons •Nerve fibres create fascicles, a few fascicle create nerve, •Particular nerve fibres are interconnected using the fibrous connective tissue – endoneurium, within the nerve • the fascicles of the fibres are interconnecte using perineurium •Teh surface of the nerve is covered by fibrous layer– epineurium Sensory nerves •They consist the afferent fibres, which lead the information from the receptors toward CNS •Within theirs course, there are sensory ganglions inserted with the bodies of pseudounipolar neurons •Peripheral branch leads the impulses from receptors within the periphery into the ganglion, the bundles of these peripheral branches form the nerve •Central branch leads the impulses from the ganglion toward the grey matter of CNS somatosensory – lead the informations from the receptors within the skin and the locomotor system (muscles, tendons, periosteum, articular capsules) viscerosensory –lead the information from receptors within the organs sensory – lead the informations from sensors motor nerves •They consist the efferent fibres, which lead from CNS into effectors (muscles or glands) and provide their activity •They originate within the nuclei of the grey matter of the spial cord or the brainstem (body of the neuron) •somatomotor nerves – innervate striated muscle, the nerve fibers (axons) enter the muscles directly without switch-over •visceromotor nerves – innervate smooth muscle and glandular cells, into which the nerve fibers enter after at least one switch-over within autonomic ganglion Mixed nerves •They consist both motor and sensory fibers. The most of the nerves are mixed, only some are either clearly motor or clearly sensory The peripheral system 1. According to from which part of CNS the nerves arise, we can divide them into: The cranial nerves (pass through the base skull) The spinal nerves (rise through foramina intervertebralia) 2. According to the innervated parts of the body: somatic nervous system autonomic nervous system •It is controlled by our consciousness •It is consist of somatosensory (or sensory) and somatomotor nerve fibers (tracts) •It does the sensory innervation of the skin and the locomotor system (muscles, tendons, bones, articular capsules) and the motor innervation of the striated muscle •It works independently on our consciousness •sympathicus, parasympathicus THE SPINAL NERVES (nervi spinales) •The spinal nerves rise from the spinal cord in the number of 31 pairs •The cervical nerves (nervi cervicales) – 8 pairs •The thoracic nerves (nervi thoracici) – 12 pairs •The lumbar nerves (nervi lumbales) – 5 pairs •The sacral nerves (nervi sacrales) – 5 pairs •The coccygeal nerve (nervus coccygeus) – 1 pair • •Each spinal nerve rises from the spinal cord through two roots, the anterior one (radix ventralis) and the posterior one (radix dorsalis) •The anterior roots consist only efferent fibres (motor), the posterior roots only afferent fibres (sensory) •Within the course of the posterior root, there is the spinal ganglion (ganglion spinale) inserted The posterior root (radix dorsalis) consists afferent fibres, which serve to superficial and deep perception, leading of pain, warmth and cold. On each posterior root, there is ganglion spinale located, which consists neurons of the afferent fibers. The anterior root (radix ventralis) consists efferent somatomotor fibres (for striated muscle) and visceromotor fibres (for smooth muscle cells within the walls of organs and vessels, the skin etc.). •The proper spinal nerv is formed by connection of the anterior and posterior root and it rises from the spinal canal through foramen intervertebrale •After the leaving of the spinal canal, the spinal nerve divides into 2 branches – the posterior branch (ramus dorsalis) and the anterior branch (ramus ventralis), both branches consist the afferent and efferent tracts. • The nerve plexuses are allways formed only by the anterior branches of the appropriate spinal nerves! Ramus dorsalis: doesn´t form plexuses Ramus ventralis: forms plexuses The posterior branches (rami dorsales) – don´t form the plexuses •They are short and thin branches of the spinal nerve •function: motor and sensory innervation of the back part of the trunk (mixed nerves) •They do the motor innervation of autochtoneí (deep) back muscles and sensory innervation of the skin in adjacent area •During their course, they keep simple segmental arrangement •Only the posterior branches of C1 – C3, L1 – L3 a S1 – S3 have more complicated arrangement C1 – C3 n. suboccipitalis n. occipitalis major n. occipitalis tertius • suboccipital muscles + skin L1 – L3 a S1 – S3 nn. clunium superiores nn. clunium medii • skin of the gluteal region n.Suboccipitalis n.Occipitalis major n.Occipitalis tertius nn.Clunium superiores nn.Clunium medii Ramus dorsalis: • ramus medialis (deep back muscles and the skin of medial part of the back) • ramus lateralis (deep back muscles in the lateral part of the back) Ramus dorsalis- ramus medialis - ramus lateralis The anterior branches (rami ventrales) •They are longer and thicker branches of the spinal nerve •Function: motor and sensory innervation of the anterior part of the trunk •They do the motor innervation of the muscles of the anterior part of the trunk (neck except infrahyoid muscles, thorax, abdomen and palevis) and the muscles of the limbs and the sensory innervation of the skin of the anterior part of the trunk and the limbs •They have more complicated arrangement than the posterior branches of the spinal nerves, they lost the segmentation and created nerve plexuses): •Plexus cervicalis C1-C4 •Plexus brachialis C4-Th1 •Nervi thoracici Th1-Th12 (they keep segmental arrangement) •Plexus lumbalis Th12-L4 •Plexus sacralis L4-5,S1-5,Co THE CERVICAL PLEXUS (plexus cervicalis) •It is created by the anterior branches of first four cervical nerves (C1 – C4) •It is located sides the cervical vertabral column and several sensory, motor and mixed nerve rise from it. The particular nerves of the cervical plexus innervate: •Sensory innervation: the skin in the neck area, a part of the head and a part of upper extremity girdle •Motor innervation: neck muscles (infrahyoid muscles, musculi scaleni and deep neck muscles and diaphragm, which originates in the neck area during embryonic development) • •suprahyoid muscles + m. sternocleidomastoideus + m. platysma are of gill origin an they are innervated by some cranial nerves, not cervical nerves •The cervical plexus •The sensory branches – they rise together by the posterior margin of m. sternocleidomastoideus – punctum nervosum sensitivum: •n. occipitalis minor (C2–3) •n. auricularis magnus (C2-C3) ramus anterior et posterior •n. transversus colli (C3)- rr. superiores et inferiores- ansa cervicalis superficialis •nn. supraclaviculares (C3-4) • mediales • intermedii • laterales •The motor branches – for pre- and intervertebral muscles, m. scalenus medius, m. sternocleidomastoideus, m. trapezius a m. levator scapulae – Ansa cervicalis (profunda) (C1–3) – (ansa n. hypoglossi) motor fibres for infrahyoid muscles, except m. thyrohyoideus (separate branch of n. thyrohyoideus) •radix sup. (C1) – joins n. hypoglossus and passes between a. carotis comm. and v. jugularis int. •radix inf. (C2–3) - along v. jugularis int., above tendon of m. omohyoideus both roots connect and ansa (loop) is created •The mixed branches •n. phrenicus (C3–5) •It divides on the inferior surface of the diaphragm – rr. phrenicoabdominales – motor innervation of the diaphragm, sensory innervation of the peritoneum, gall bladder, pancreas; r. pericardiacus – sensory innervation of the pericardium and adjacent part of pleura •nn. phrenici acc. – accessory fibres – a) directly from plx. brachialis (C5–6), – b) through n. subclavius – c) friom radix inf. ansae cervicalis •They can substitute typical n. phrenicus •Irritation of the nerve – singultus – (hiccup) • THE THORACIC NERVES (nervi intercostales) •They keep segmental arrangement, don´t form plexuses, pass within intercostal spaces from behinf forward together with the intercostal vessels (within sulcus costae on the inferior margin of the rib) •1. – 6. toward the sternum, 7. – 12. toward the anterior abdominal wall • they innervates: •Sensory i.: skin of thorax and abdomen and parietal sheet of pleura and peritoneum •Motor i.: proper thoracic (intercostal) muscles and anteriro and lateral group of abdominal muscles Nn. thoracici Th1-12 •Don´t form plexuses nn. intercostales n. subcostalis •rr. musculares (autochtone muscles of thorax) •rr. cutanei- laterales- nn. intercostobrachiales - anteriores (by the sternal margin) Skin of thorax and abdomen •rr. pleurales from Th1- strong connection into plexus brachialis (nervus intercostobrachialis) nn.Thoracici Th1-12 Netvoří pletenš nn.Intercostales n.Subcostalis - rr.musculars - rr.cutanie - rr.pleurales Z Th1- silná spojka do pl.brachialis Nn. intercostobrachiales (n. cutaneus brachii medialis) •Obrázky: •Atlas der Anatomie des Menschen/Sobotta. Putz,R., und Pabst,R. 20. Auflage. München:Urban & Schwarzenberg, 1993 •Netter: Interactive Atlas of Human Anatomy. •Naňka, Elišková: Přehled anatomie. Galén, Praha 2009. •Čihák: Anatomie I, II, III. •Drake et al: Gray´s Anatomy for Students. 2010