NERVOUS SYSTEM

1. NERVOUS SYSTEM Prof. Dr. Sc.agr. Ir. Suyadi, MS.

2. Nervous System =Systema Nervorum • A complex mechanism by which the organism is brought into functional relation with its environment, and its various parts are coordinated

3. Parts of the nervous system • Central Nervous System (CNS): • Brain (Encephalon) • Spinal cord (Medulla spinalis) • Peripheral Nervous system • Cranial and spinal nerves with their ganglia • Sympathetic nervous system

4. The nervous system is divided into the • peripheral nervous system (PNS) and the • central nervous system (CNS)

5. The PNS consists of: • sensory neurons running from stimulus receptors that inform the CNS of the stimuli • motor neurons running from the CNS to the muscles and glands - called effectors - that take action. The CNS consists of: • the spinal cord and the • brain The peripheral nervous system is subdivided into : • the sensory-somatic nervous system and the • autonomic nervous system

6. The Sensory-Somatic Nervous System • The sensory-somatic system consists of 12 pairs of cranial nerves and • 31 pairs of spinal nerves

7. The cranial nerves *Note: These do contain a few sensory neurons that bring back signals from the muscle spindles in the muscles they control.

10. Structure of Neuron cell A neuron is a cell specialized to conduct electrochemical impulses called nerve impulses or action potentials.

11. The Spinal Nerves • All of the spinal nerves are "mixed"; that is, they contain both sensory and motor neurons

12. The Autonomic Nervous System The autonomic nervous system consists of sensory neurons and motor neurons that run between the central nervous system (especially the hypothalamus and medulla oblongata) and various internal organs such as the: • heart • lungs • viscera • glands (both exocrine and endocrine) It is responsible for monitoring conditions in the internal environment and bringing about appropriate changes in them. The contraction of both smooth muscle and cardiac muscle is controlled by motor neurons of the autonomic system.

13. The actions of the autonomic nervous system are largely involuntary (in contrast to those of the sensory-somatic system). It also differs from the sensory-somatic system is using two groups of motor neurons to stimulate the effectors instead of one. • The first, the preganglionic neurons, arise in the CNS and run to a ganglion in the body. Here they synapse with • postganglionic neurons, which run to the effector organ (cardiac muscle, smooth muscle, or a gland).

14. The autonomic nervous system has two subdivisions, • the sympathetic nervous system and the • parasympathetic nervous system.

15. The Sympathetic Nervous System • The preganglionic motor neurons of the sympathetic system (shown in black) arise in the spinal cord. They pass into sympathetic ganglia which are organized into two chains that run parallel to and on either side of the spinal cord.

16. The preganglionic neuron may do one of three things in the sympathetic ganglion: • synapse with postganglionic neurons (shown in white) which then re-enter the spinal nerve and ultimately pass out to the sweat glands and the walls of blood vessels near the surface of the body. • pass up or down the sympathetic chain and finally synapse with postganglionic neurons in a higher or lower ganglion • leave the ganglion by way of a cord leading to special ganglia (e.g. the solar plexus) in the viscera. Here it may synapse with postganglionic sympathetic neurons running to the smooth muscular walls of the viscera. However, some of these preganglionic neurons pass right on through this second ganglion and into the adrenal medulla. Here they synapse with the highly-modified postganglionic cells that make up the secretory portion of the adrenal medulla.

17. Functional work • Neurons send signals to other cells as electrochemical waves travelling along thin fibres called axons, which cause chemicals called neurotransmitters to be released at junctions called synapses • A cell that receives a synaptic signal may be excited, inhibited, or otherwise modulated. • Sensory neurons are activated by physical stimuli impinging on them, and send signals that inform the central nervous system of the state of the body and the external environment.

18. Functional Work (2) • Motor neurons, situated either in the central nervous system or in peripheral ganglia, connect the nervous system to muscles or other effector organs. • Central neurons, which in vertebrates greatly outnumber the other types, make all of their input and output connections with other neurons. • The interactions of all these types of neurons form neural circuits that generate an organism's perception of the world and determine its behavior. • Along with neurons, the nervous system contains other specialized cells called glial cells (or simply glia), which provide structural and metabolic support.

19. From Signals  to behavior Signal (electrochemical wave neurotransmitters axon Neuron synapsis muscle CNS Perception of work • Exciting • Inhibiting • modulating Effector organ behavior

20. Structure of Neuron cell The main structure of a neuron is the cell body, the dendrite (receives signals) and the axon (sends signals). Signals are sent to and from the central nervous system via action potentials (ion channels) which allow signals to travel by changing the concentration of ions (sodium outside, and potassium inside) within the axons and dendrites.

23. Cell structure • Neuron: • Unit utama dari sistem syaraf • Sel besar, inti dan bagian-bagian • Sering ada penjuluran (prosesus)  axon • Fungsi bagian-bagian sel : seperti sel lain (kromosom: pembawa sifat keturunan; mitokondria: mengatur aliran energi; dst)

24. Ada dua macam prosessus • Dendrit: • pendek, bentuk dan ukuran berbeda • Fungsi: menerima rangsangan (impuls) • Axon: • Panjang, tidak bercabang • Tunggal • Cabang: collateral • Akhiran: telodendron • Fungsi: meneruskan rangsangan

25. Selubung syaraf • Myelin • Mengelilingi axon, • Lipoid • Dikelilingi oleh selubung brkt  Schwann cell (neurolemma) • Sering selubung myelin mengalami pelekukan  nodus Ranvier • Fungsi Schwann cell: • Regenerasi axon • Sumber nutrisi • Membentuk bungkus myelin

26. Secara struktural neuron dibagi: • Unipolar: mempunyai satu prosesus • Bipolar: dua prosesus dengan dua arah yang berlawanan • Pseudo unipolar: pada awalnya bipolar, multipolar dengan arah berbeda-2

27. Divisi sensoris – reseptor sensoris • Rangsangan (impuls)  sensoris  reaksi segera • Atau dapat disimpan dalam otak  reaksi kemudian • Informasi  sistem syaraf (nervus spinalis)  ke medula spinalis  medula oblongata  pons  cerebrum  thalamus  daerah somatik korteks serebri

28. Divisi motorik - efektor • Tugas pokok sistem syaraf adalah mengatur kegiatan tubuh, dicapai dengan mengatur: • Kontraksi otot rangka; • Kontraksi otot polos dalam organ internal; • Sekresi kelenjar eksokrin dan endokrin • Ini disebut fungsi motorik dari sistem syaraf • Syaraf, otot dan endokrin disebut • Bagoam sistem syaraf yang langsung berhubungan dengan penghantaran sinyal ke otot  divisi motorik

29. Peranan sinaps • Sinaps: tempat hubungan satu neuron dengan neuron berikutnyua • Suatu tempat menguntungkan untuk mengatur penghantaran sinyal • Menentukan arah penyebaran sinyal • Melakukan tindakan selektif

30. Peranan muscle spindle (otot dan tendo) • Muscle spindle  mendeteksi perubahan panjang serabut otot dan perubahan kecepatan panjang • Tendo golgi  mendeteksi ketegangan yang bekerja pada tendo otot selama kontraksi otot atau pereganan otot. • Bekerja pada tingkat bawah sadar  tidak menyebabkan persepsi sensoris

31. Sistem syaraf otonom • Mengatur fungsi viseral tubuh • Membantu mengatur tekanan arteri, motilitas dan sekresi gastrointestinal, output urin, berkeringat, suhu tubuh, dll. • Impuls dikirim dengan sistem • Simpatis (epineprin dan norepineprin) • Parasimpatis (jantung, paru, esophagus, kandung empedu, pankreas, baigan atas uretra, dll)

32. Reflek otonom • Sistem syaraf otonom mengatur fungsi viceral  dengan memakai reflek otonom – gastrointestinal • Bagian atas: • Bau makan  selera makanan melalui syaraf dalam hidung  nukleus vagus  glosofaringeus  salivarius batang otak. • Ke syaraf parasimpatis ke kelj sekretor mulut dan lambung  sekresi getang pencernaan.