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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 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
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
Nerves
I
Olfactory
Type
Function
sensory
olfaction (smell)
sensory
(Contain 38% of all the axons
connecting to the brain.)
motor*
eyelid and eyeball muscles
motor*
eyeball muscles
V
Trigeminal
mixed
Sensory: facial and mouth
sensation
Motor: chewing
VI
Abducens
motor*
eyeball movement
VII
Facial
mixed
Sensory: taste
Motor: facial muscles and
salivary glands
sensory
hearing and balance
II
Optic
III
Oculomotor
IV
Trochlear
VIII
Auditory
IX
Glossopharyngeal
X
Vagus
XI
Accessory
XII
Hypoglossal
vision
mixed
mixed
motor
motor*
Sensory: taste
Motor: swallowing
main nerve of the
parasympathetic nervous
system (PNS)
swallowing; moving head
and shoulder
tongue muscles
*Note: These do contain a few sensory neurons that bring back signals from the muscle spindles in the muscles they control.
Structure of Neuron cell
A neuron is a cell specialized to conduct electrochemical impulses called nerve
impulses or action potentials.
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 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.
The actions of the autonomic nervous system are largely
involuntary (in contrast to those of the sensorysomatic system). It also differs from the sensorysomatic 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).
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 sympathetic
ganglia which are organized into two chains
that run parallel to and on either side of the
spinal cord.
The preganglionic neuron may do one of three things in the
sympathetic ganglion:
1. 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.
2. pass up or down the sympathetic chain and finally synapse with
postganglionic neurons in a higher or lower ganglion
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 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 highlymodified postganglionic cells that make up the secretory portion
of the adrenal medulla.
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.
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.
From Signals  to behavior
Signal
(electrochemical
wave
Neuron
axon
synapsis
muscle
Perception
of work
neurotrans
mitters
CNS
Effector
organ
behavior
•Exciting
•Inhibiting
•modulating
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.
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
– Fungsi: meneruskan rangsangan
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
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
somatik korteks serebri
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
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  tidak
menyebabkan persepsi sensoris
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)
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.