Kuliah4-anatomi2-Nervous sistem

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

  

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

  

Parts of the nervous system

  1. Central Nervous System (CNS):

• – Brain (Encephalon)
• – Spinal cord (Medulla spinalis)

  2. Peripheral Nervous system

• – Cranial and spinal nerves with their ganglia
• – Sympathetic nervous system

The nervous system is divided into the

  

1. peripheral nervous system (PNS)

and the

  2. central nervous system (CNS)

  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 efectors - 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

  The Sensory-Somatic Nervous System

• The sensory-somatic system consists of 12 pairs of cranial nerves and
• 31 pairs of spinal nerves

  The cranial nerves _{Olfactory Nerves Type Function I sensory Oculomotor Optic III II sensory (Contain 38% of all the axons * motor eyelid and eyeball muscles connecting to the brain.) Trigeminal Trochlear}

  IV _{V mixed sensation * motor eyeball muscles Sensory: facial and mouth Abducens VII VI * eyeball movement motor} Motor: chewing _{Sensory: Auditory Facial VIII sensory}

  IX Sensory: taste _{X mixed mixed main nerve of the Accessory and shoulder XII}

_{XI swallowing; moving head}

_{motor (PNS) Hypoglossal} * tongue muscles motor

  

_{A neuron is a cell specialized to conduct electrochemical impulses}

_{called nerve impulses or action potentials.} Structure of Neuron cell

  The Spinal Nerves

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

  

The Autonomic Nervous System

The autonomic nervous system consists of sensory neurons

and motor neurons that run between the central nervous system (especially thend and various internal organs such as the:

• heart
• lungs
• viscera
• glands (both _{environment and bringing about appropriate changes in them. It is responsible for monitoring conditions in the internal}

   The contraction of botis The actions of the autonomic nervous system are largely involuntary (in contrast to those of the sensory-somatic system). It also difers from the sensory-somatic system is using two groups of motor neurons to stimulate the efectors instead of one.

• The frst, the preganglionic neurons, arise in the CNS and r body. Here they

  ith

• • postganglionic neurons, which run to the efector

  organ (cardiac muscle, smooth muscle, or a gland).

  The autonomic nervous system has two subdivisions,

• the sympathetic nervous system and the
• parasympathetic nervous system.

  

The Sympathetic Nervous

System

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

  

_{1. synapse with postganglionic neurons (shown in white) which then}

The preganglionic neuron may do one of three things in the _{sympathetic ganglion: 2. pass up or down the sympathetic chain and fnally synapse with glands and the walls of blood vessels near the surface of the body.} re-enter the spinal nerve and ultimately pass out to the sweat

_{3. 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 neurons in a higher or lower ganglion

_{preganglionic neurons pass right on through this second ganglion}

_{muscular walls of the viscera. However, some of these} postganglionic sympathetic neurons running to the smooth _{the adrenal medulla. modifed postganglionic cells that make up the secretory portion of} and into thHere they synapse with the highly-

Functional work

• Neurons send signals to other cells as electrochemical waves travelling along thin fbres called
• 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

Functional Work (2)

• • Motor neurons, situated either in the central nervous

  system or in peripheral ganglia, connect the nervous system to muscles or other efector 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(or simply glia), which provide structural and metabolic support.

  CNS muscle Efecto r organ

  From Signals  to behavior Neuron axon ^{Signal (electrochemi cal wave neurotra} _nsmitters synapsis

  Perceptio n of work behavio

• Exciting • Inhibiting • modulatin g

Structure of Neuron cell The main structure of a neuron is the cell body, the dendrite (receives

  

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)
Ada dua macam prosessus

• Dendrit:
• – pendek, bentuk dan ukuran berbeda
• – Fungsi: menerima rangsangan (impuls)
• Axon:
• – Panjang, tidak bercabang
• – Tunggal – Cabang: collateral
• – Akhiran: telodendron

  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

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

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

  

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

Peranan sinaps

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

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 

  

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,

  

Refek otonom

• Sistem syaraf otonom mengatur fungsi viceral  dengan memakai refek 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