Human respiratory system is the system breathe oxygen from the air and remove carbon dioxide and water vapor. In the process of respiration, oxygen is a major requirement substance. Oxygen for breathing obtained from the air in the surrounding environment. Respiratory function tools incorporate air containing oxygen and remove the air containing carbon dioxide and water vapor. The purpose of breathing process is to obtain energy. In the event the release of energy breathing. Human respiratory system includes two things, namely respiratory tract and respiratory mechanisms.
Respiratory tract or respiratory tract (respiratory tract) is part of
the human body that serves as a track and Gated gas exchange necessary
for the breathing process. This channel from either the nose or mouth and ended up in the lungs. 1. Human Respiratory Organs Here are the parts of the respiratory organs in humans. a.Nose (cavum Nasalis) Aside from being one of the human respiratory organs, nose also serves as one of the five senses. The nose serves as a tool to breathe the air, the air filter will go into the lungs, and as the sense of smell. b.Throat (pharynx)
The pharynx is the junction between the nasal cavity to the throat
(respiratory) and oral cavity to the esophagus (digestive tract). On the back of the pharynx are larynx. The larynx is also called the base of the throat. In the larynx are the vocal cords or epiglottis and larynx valve. At the time swallowing the epiglottis covers the larynx so that the food does not go into the throat. In contrast to the breathing time epiglottis will open so that air into the larynx and then to the throat. c.Throat (trachea) d.Branch Throat (bronchi) The trachea bronchial branches. The amount pair, the one to the right lung and one to the left lung. Bronchus to the left is longer, narrower, and the horizontal than to the right. This has resulted in the right lung more susceptible to disease. Bronchial wall structure similar to the trachea. The difference tracheal wall thicker than the walls of the bronchi. Will bronchial branches into bronchioles. Right bronchus branches into three bronchioles whereas the left bronchus branches into two bronchioles. e.Bronchioles Bronchioles is a branch of the bronchus. Bronchial branches into increasingly fine line, small, and the walls are thinner. Bronchial cartilage but does not have a ciliated sockets. Each bronchial empties into the alveoli. f.Alveolus g.Lungs The lungs are located in the chest cavity. Chest and abdominal cavity bounded by siuatu bulkhead called the diaphragm. Lungs were two, namely the right lung and the left lung. Right lung has three wattle (lobes) that wattle upper, middle and wattle wattle below. While the left lung is composed of two wattle wattle top and bottom wattle. The lungs are enveloped by the lining of the lungs (pleura). The maximum capacity of the lungs hover around 3.5 liters. The air in and out of the lungs during normal breathing is called air breathing (tidal air). The volume of air breathing in adults approximately 500 nl. After we did the usual inspiration, we can still draw breath deeply. Air that can enter after holding inspiration so-called complementary air, the volume of approximately 1500 ml. After we did the usual expiration, we still can exhale with a vengeance. The air can be removed after the expiration commonly called supplementary air volume is approximately 1500 ml. Although we exhale from the lungs with a vengeance turns the lungs still air is called air residue. Residual air volume of approximately 1500 ml. Total volume of breathing air, air complementary and supplementary air called the vital capacity of the lungs. 2. Human Respiratory Process
The order of the respiratory tract are as follows: nasal cavity>
pharyngeal> trachea> bronchus> lungs (bronchioles and alveoli). Human respiratory process starts from the nose.
The air is sucked in a breath (inspiration) usually come in through the
nostrils (nares) left and right other than through the mouth. At the time of entry, the air is filtered by the nose hairs on the inside of the nostrils. At the time you inhale, the diaphragm muscle to contract. Originally diaphragm position curved upwards now be straight so that the chest cavity expands. This is called abdominal breathing. Along with the contraction of the diaphragm muscle, rib muscles also contract, and thus expands the chest cavity. This is called respiratory chest.
Due to the expansion of the chest cavity, the pressure in the chest
cavity is reduced, so that the outside air in through the nose the next
through the respiratory tract finally air into the lungs, so the lungs
inflate.
After passing through the nasal cavity, air enters into the upper
esophagus (Naro-pharinx) and then down to the next entry throat
(larynx).
After going through the throat, the air into the windpipe or trachea,
from there forwarded to the channel named bronchus or bronchi. Bronchial tract consists of several levels of branching and finally touch in the alveoli in the lungs.
The air is absorbed through the alveoli into the capillaries will
hereinafter be streamed into the pulmonary vein, or pulmonary veins. Oxygen gas is taken up by the blood. From there, the blood will flow into the left atrium of the heart and so on. Furthermore air containing carbon dioxide gas will be released through the nose back.
Exhalation due melemasnya diaphragm muscles and the muscles of the ribs
and also assisted with berkontraksinya abdominal muscles.
Diaphragm be curved upward, ribs down to the bottom and move inward,
resulting in smaller chest cavity so that the pressure in the chest
cavity rises. With the rising pressure in the chest cavity, the air from the lungs out past the respiratory tract. Summary of Air Breathing way: 1. Air enters through the nostrils 2. pass the nasopharynx 3. passes oral farink 4. past the glottis 5. The entrance to the trachea 6. The entry into the trachea branches called bronchi 7. entry into branching bronchi called bronchioles 8. Air expire at the end of the bronchus in the form of bubbles, called alveoli (plural: alveoli 3. Types of Breathing In Humans Types of breathing in humans is divided into two types. Namely respiratory chest and abdominal breathing. a.Breathing Chest Chest breathing is breathing that involves muscle antartulang ribs. Mechanisms can be distinguished as follows. 1. Phase inspiration.
This phase in the form of muscle berkontraksinya antartulang ribs so
that the chest cavity enlarges, resulting in pressure in the chest
cavity becomes smaller than the pressure outside so that the oxygen-rich
air outside the entrance.
Breathing chest 2. expiratory phase.
This phase is the phase of relaxation or muscle between the ribs return
to its original position which was followed by a decline in the ribs so
that the chest cavity becomes smaller.
As a result, the pressure in the chest cavity becomes greater than the
pressure outside, so that the air in the chest cavity that is rich in
carbon dioxide out.
Breathing chestb.Abdominal Breathing Abdominal breathing is breathing involving the diaphragm muscle. Mechanisms can be distinguished as follows. 1. Phase inspiration.
This phase of the diaphragm muscle that form berkontraksinya chest
cavity enlarges, resulting in pressure in the chest cavity becomes
smaller than the pressure outside so that outside air is rich in oxygen
from entering.
Abdominal Breathing 2. expiratory phase.
This phase is the phase diaframa muscle relaxation or return to the
original position which was followed by a decline in the ribs so that
the chest cavity becomes smaller.
As a result, the pressure in the chest cavity becomes greater than the
pressure outside, so that the air in the chest cavity that is rich in
carbon dioxide out. 4. Respiratory System Diseases in Humans Human respiratory system consists of several organs can be impaired. This disorder biasanyaberupa disorder, disease, or because of human activity itself (such as smoking). Disease or disorder that attacks the respiratory system may cause disturbance in the breathing process. a.Asthma Asthma is a disorder of the respiratory organs such as narrowing of the airways due to a reaction to certain stimuli. Things that can trigger asthma attacks such as pollen, dust, animal dander, smoke, cold air and exercise. Proper and regular treatment can help patients. Asthma attacks can be prevented if the trigger factor is known and can be avoided. The attacks triggered by exercise can be avoided by taking medicine before exercise. b.Bronchitis Bronchitis is an inflammation of the bronchi (air passages to the lungs).
The disease is usually mild and will eventually recover completely, but
in patients who have chronic diseases (such as heart or lung disease)
and in the elderly, bronchitis can be serious. Recurrent bronchitis attacks can occur in smokers and patients with lung disease and chronic respiratory tract. Recurrent infections can also be the result of: c.Influenza Influenza or flu is an infectious disease caused by influenza virus. The disease is transmitted through the air by sneezing from the patient. This disease not only affects humans, birds, and mammals such as pigs and orang-utan can also have a cold. In humans, a common symptom is fever, sore throat, headache, nasal congestion and discharge, coughing, lethargy and malaise. In worse cases, influenza can also cause pneumonia, which can result in death, especially in children and the elderly. Transmission period until the disease usually is 1 to 3 days after contact with animals or people who influenza. Patients are encouraged to isolate themselves or quarantined so as not to transmit the disease until they feel better. d.Bird flu Bird flu or avian influenza is an infectious disease caused by a virus that usually infects birds and mammals. The cause of bird flu is a type A influenza virus that spreads among birds. The virus is then found to be able to also spread to other species such as pigs, cats, dogs, tigers, and humans. The virus can be transmitted through the air or contact through food, beverages, and touch. However, this virus will die in high temperatures. Therefore, meat, eggs, and animals should be thoroughly cooked to avoid infection. Personal hygiene should be maintained also by washing hands with antiseptic. Cleanliness of body and clothing also needs to be maintained. The virus can survive in cold temperatures. Raw foods refrigerated or frozen can save virus. Hands should be washed before and after cooking or touching raw food materials. Poultry should not be kept in the house or room dwelling. Livestock must be kept out of the housing to reduce the risk of transmission. Common symptoms that can occur are high fever, respiratory symptoms, and (possibly) the abdomen. The development of the virus in the body can run fast so that the patient requires immediate treatment. e.Swine flu (swine influenza) Swine flu cases are caused by the influenza virus that usually affects pigs Orthomyxoviridae.
Swine flu infect humans each year and is usually found in people who
come into contact with pigs, though found also cases of human-to-human
transmission.
Symptoms of the virus include fever, disorientation, stiffness in the
joints, vomiting, and loss of consciousness that ended in death According to the Centers for Disease Control and Prevention in the United States, influenza symptoms similar to influenza. Symptoms such as fever, cough, pain in throat, body aches, head, chills, and limp. Some patients also reported defecating and vomiting. f.Asbestosis Asbestosis is a respiratory disease caused by inhaling asbestos fibers, in which the lungs are formed extensive scarring. Asbestos is a mineral composed of silicate fibers with different chemical composition. If inhaled, asbestos fibers settle in the lungs, causing scarring. Inhaling asbestos can also cause thickening of the pleura (the membrane that lines the lungs). Inhaling asbestos fibers can cause scarring (fibrosis) in the lungs. Lung tissue that forms fibrosis can not expand and contract as it should. Severity of the disease depends on the duration of exposure and the number of fibers inhaled.
Symptoms of asbestosis appear gradually and emerging only after the
formation of scar tissue in large quantities and the lungs lose their
elasticity. g.Pharyngitis Pharyngitis is an inflammatory disease that attacks the throat or pharynx. Sometimes also referred to as strep throat. This inflammation can be caused by viruses or bacteria, when the immune system is weak. Treatment with antibiotics is effective only if for germs. Sometimes eating a healthy diet with lots of fruits, along with vitamins can help. h.TBC TB disease can affect anyone (old, young, male, female, poor, or rich) and anywhere.
Each year, Indonesia increased by a quarter of a million new TB cases
and approximately 140,000 deaths occur each year are caused by
tuberculosis. In fact, Indonesia is the third largest country with the problem of tuberculosis in the world. TB disease is an infectious disease caused by bacteria Mikobakterium tuberculosis. These bacteria are rod-shaped and are resistant to acid, also known as Trunk Hold acid (BTA).
This bacterium was first discovered by Robert Koch on March 24, 1882,
so as to commemorate his services bacteria named Koch bacillus. In fact, TB disease of the lungs, sometimes referred to as Koch Pulmonum (KP).
TB disease is usually transmitted through contaminated air with
Mikobakterium tuberculosis bacteria that are released during coughing TB
patients, and in children the source of infection is generally derived
from adult TB patients.
These bacteria when frequently enter and accumulate in the lungs will
breed a lot (especially in people with a low immune system), and can be
spread through the blood vessels or lymph nodes.
That is why TB infection can infect virtually all body organs such as
the lungs, brain, kidneys, gastrointestinal tract, bone, lymph nodes,
and others, although the organs most commonly affected are the lungs. i.Emphysema Emphysema is caused due to loss of elasticity in the alveoli. Alveoli are bubbles contained in the lungs.
In people with emphysema, lung volume greater than a healthy person
because the carbon dioxide should be issued from the lungs trapped
therein. Cigarette smoke and the enzyme deficiency of alpha-1-antitrypsin is the cause of loss of elasticity in the lungs. Symptoms of emphysema: • Shortness of breath for a long time and can not be cured with medication reliever commonly used shortness of breath. • decreased appetite and weight loss are also common in patients with decreased emphysema. Prevention and solutions: Avoiding cigarette smoke is the best way to prevent this disease. Quitting smoking is also very important. j.Lung Cancer Parumerupakan killer lung cancer compared to other cancers first. Cancer can grow in these tissues and can spread to other parts.
The main cause is cigarette smoke contains many toxic substances and
inhaled into the lungs and have been accumulating for decades causing
mutations in airway cells and cause cancer cells. Another cause is the active radio radiation, toxic chemicals, stress or heredity. Symptoms: Cough, chest pain, shortness of breath, coughing up blood, fatigue and weight loss. But as in other types of cancer, symptoms generally only visible when this cancer has grown large or spread.
Prevention and solutions: Avoiding smoking and cigarette smoke are also
many nutritious foods that contain lots of antioxidants to prevent
cancer cells. k.Pneumonia Cause: Pneumonia is an infection that occurs in the lung tissue (parenchyma) caused by bacteria, viruses or fungi. Generally caused by streptococcus bacteria (Streptococcus) and the bacterium Mycoplasma pneumoniae. Symptoms: Cough and phlegm with thick yellow sputum, chest pain, and shortness of breath are also accompanied by high fever.
Prevention and solutions: Always maintain cleanliness and keep the
immune system stay strong can prevent bacteria are not able to penetrate
the defenses of the body's health. Make it a habit to wash hands, eat a nutritious diet or exercise regularly.
Sistem saraf merupakan salah satu sistem koordinasi yang bertugas menyampaikan rangsangan dari reseptor untuk dideteksi dan direspon oleh tubuh. Sistem saraf memungkinkan makhluk hidup tanggap dengan cepat terhadap perubahan-perubahan yang terjadi di lingkungan luar maupun dalam.
Untuk menanggapi rangsangan, ada tiga komponen yang harus dimiliki oleh sistem saraf, yaitu:
Reseptor, adalah alat penerima rangsangan atau impuls. Pada tubuh kita yang bertindak sebagai reseptor adalah organ indera.
Penghantar impuls, dilakukan oleh saraf itu sendiri. Saraf tersusun dari berkas serabut penghubung (akson). Pada serabut penghubung terdapat sel-sel khusus yang memanjang dan meluas. Sel saraf disebut neuron.
Efektor, adalah bagian yang menanggapi rangsangan yang telah diantarkan oleh penghantar impuls. Efektor yang paling penting pada manusia adalah otot dan kelenjar
1. Sel Saraf (Neuron)
Sistem saraf terdiri atas sel-sel saraf yang disebut neuron. Neuron bergabung membentuk suatu jaringan untuk mengantarkan impuls (rangsangan). Satu sel saraf tersusun dari badan sel, dendrit, dan akson.
a. Badan sel
Badan sel saraf merupakan bagian yang paling besar dari sel saraf. Badan sel berfungsi untuk menerima rangsangan dari dendrit dan meneruskannya ke akson. Pada badan sel saraf terdapat inti sel, sitoplasma, mitokondria, sentrosom, badan golgi, lisosom, dan badan nisel. Badan nisel merupakan kumpulan retikulum endoplasma tempat transportasi sintesis protein.
b. Dendrit
Dendrit adalah serabut sel saraf pendek dan bercabang-cabang. Dendrit merupakan perluasan dari badan sel. Dendrit berfungsi untuk menerima dan mengantarkan rangsangan ke badan sel.
c. Akson
Akson disebut neurit. Neurit adalah serabut sel saraf panjang yang merupakan perjuluran sitoplasma badan sel. Di dalam neurit terdapat benang-benang halus yang disebut neurofibril. Neurofibril dibungkus oleh beberapa lapis selaput mielin yang banyak mengandung zat lemak dan berfungsi untuk mempercepat jalannya rangsangan. Selaput mielin tersebut dibungkus oleh sel-sel sachwann yang akan membentuk suatu jaringan yang dapat menyediakan makanan untuk neurit dan membantu pembentukan neurit. Lapisan mielin sebelah luar disebut neurilemma yang melindungi akson dari kerusakan. Bagian neurit ada yang tidak dibungkus oleh lapisan mielin. Bagian ini disebut dengan nodus ranvier dan berfungsi mempercepat jalannya rangsangan.
Ada tiga macam sel saraf yang dikelompokkan berdasarkan struktur dan fungsinya, yaitu:
1) Sel saraf sensorik, adalah sel saraf yang berfungsi menerima rangsangan dari reseptor yaitu alat indera.
2) Sel saraf motorik, adalah sel saraf yang berfungsi mengantarkan rangsangan ke efektor yaitu otot dan kelenjar. Rangsangan yang diantarkan berasal atau diterima dari otak dan sumsum tulang belakang.
Perbedaan struktur dan fungsi dari ketiga jenis sel saraf tersebut lebih jelasnya bisa dilihat pada tabel di bawah ini.
Tabel Perbedaan sel saraf sensorik, penghubung, dan motorik
No
Pembeda
Sensorik
Penghubung
Motorik
1
Ukuran Dendrit
Panjang
Pendek
Pendek
2
Ukuran Neurit
Panjang
Pendek
Panjang
3
Fungsi Dendrit
Menerima rangsangan dari reseptor
Menerima dan merusak rangsangan
Menerima rangsangan dari sel saraf lain
5
Fungsi Neurit
Meneruskan rangsangan ke sel saraf lain
Menerima dan meneruskan rangsangan
Meneruskan rangsangan ke efektor
3) Sel saraf penghubung Sel saraf penghubung adalah sel saraf yang berfungsi menghubungkan sel saraf satu dengan sel saraf lainnya. Sel saraf ini banyak ditemukan di otak dan sumsum tulang belakang. Sel saraf yang dihubungkan adalah sel saraf sensorik dan sel saraf motorik.
Saraf yang satu dengan saraf lainnya saling berhubungan. Hubungan antara saraf tersebut disebut sinapsis. Sinapsis ini terletak antara dendrit dan neurit. Bentuk sinapsis seperti benjolan dengan kantung-kantung yang berisi zat kimia seperti asetilkolin (Ach) dan enzim kolinesterase. Zat-zat tersebut berperan dalam mentransfer impuls pada sinapsis.
2. Impuls
Impuls adalah rangsangan atau pesan yang diterima oleh reseptor dari lingkungan luar, kemudian dibawa oleh neuron. Impuls dapat juga dikatakan sebagai serangkaian pulsa elektrik yang menjalari serabut saraf. Contoh rangsangan adalah sebagai berikut.
a. Perubahan dari dingin menjadi panas.
b. Perubahan dari tidak ada tekanan pada kulit menjadi ada tekanan.
c. Berbagai macam aroma yang tercium oleh hidung.
d. Suatu benda yang menarik perhatian.
e. Suara bising.
f. Rasa asam, manis, asin dan pahit pada makanan.
Impuls yang diterima oleh reseptor dan disampaikan ke efektor akan menyebabkan terjadinya gerakan atau perubahan pada efektor. Gerakan tersebut adalah sebagai berikut. a. Gerak sadar
Gerak sadar atau gerak biasa adalah gerak yang terjadi karena disengaja atau disadari. Impuls yang menyebabkan gerakan ini disampaikan melalui jalan yang panjang. Bagannya adalah sebagai berikut.
b. Gerak refleks
Gerak refleks adalah gerak yang tidak disengaja atau tidak disadari. Impuls yang menyebabkan gerakan ini disampaikan melalui jalan yang sangat singkat dan tidak melewati otak. Bagannya sebagai berikut.
Contoh gerak refleks
adalah sebagai berikut.
☯ Terangkatnya kaki jika terinjak sesuatu.
☯ Gerakan menutup kelopak mata dengan cepat jika ada benda asing yang masuk ke mata.
☯ Menutup hidung pada waktu mencium bau yang sangat busuk.
☯ Gerakan tangan menangkap benda yang tiba-tiba terjatuh.
☯ Gerakan tangan melepaskan benda yang bersuhu tinggi.
3. Susunan Sistem Saraf
Di dalam tubuh kita terdapat miliaran sel saraf yang membentuk sistem saraf. Sistem saraf manusia tersusun dari sistem saraf pusat dan sistem saraf tepi. Sistem saraf pusat terdiri atas otak dan sumsum tulang belakang. Sedangkan sistem saraf tepi terdiri atas sistem saraf somatis dan sistem saraf otonom.
a. Sistem saraf pusat
1) Otak
Otak merupakan alat tubuh yang sangat penting dan sebagai pusat pengatur dari segala kegiatan manusia. Otak terletak di dalam rongga tengkorak, beratnya lebih kurang 1/50 dari berat badan. Bagian utama otak adalah otak besar (Cerebrum), otak kecil (Cerebellum), dan batang otak.
Otak besar merupakan pusat pengendali kegiatan tubuh yang disadari. Berpikir, berbicara, melihat, bergerak, mengingat, dan mendengar termasuk kegitan tubuh yang disadari. Otak besar dibagi menjadi dua belahan, yaitu belahan kanan dan belahan kiri.
Masing-masing belahan pada otak tersebut disebut hemister. Otak besar belahan kanan mengatur dan mengendalikan kegiatan tubuh sebelah kiri, sedangkan otak belahan kiri mengatur dan mengendalikan bagian
tubuh sebelah kanan.
Otak kecil terletak di bagian belakang otak besar, tepatnya di bawah otak besar. Otak kecil terdiri atas dua lapisan, yaitu lapisan luar berwarna kelabu dan lapisan dalam berwarna putih. Otak kecil dibagi menjadi dua bagian, yaitu belahan kiri dan belahan kanan yang dihubungkan oleh jembatan varol. Otak kecil berfungsi sebagai pengatur keseimbangan tubuh dan mengkoordinasikan kerja otot ketika seseorang akan melakukan kegiatan.
Batang otak tersusun dari medula oblangata, pons, dan otak tengah. Batang otak terletak di depan otak kecil, di bawah otak besar, dan menjadi penghubung antara otak besar dan otak kecil. Batang otak disebut dengan sumsum lanjutan atau sumsum penghubung. Batang otak terbagi menjadi dua lapis, yaitu lapisan dalam dan luar berwarna kelabu karena banyak mengandung neuron. Lapisan luar berwarna putih, berisi neurit dan dendrit. Fungsi dari batang otak adalah mengatur refleks fisiologis, seperti kecepatan napas, denyut jantung, suhu tubuh, tekanan, darah, dan kegiatan lain yang tidak disadari.
Fungsi Otak kiri dan otak kanan berbeda, dapat dilihat pada gambar berikut ini
2) Sumsum tulang belakang
Sumsum tulang belakang terletak memanjang di dalam rongga tulang belakang, mulai dari ruas-ruas tulang leher sampai ruas-ruas tulang pinggang yang kedua. Sumsum tulang belakang terbagi menjadi dua lapis, yaitu lapisan luar berwana putih dan lapisan dalam berwarna kelabu. Lapisan luar mengandung serabut saraf dan lapisan dalam mengandung badan saraf.
Di dalam sumsum tulang belakang terdapat saraf sensorik, saraf motorik, dan saraf penghubung. Fungsinya adalah sebagai penghantar impuls dari otak dan ke otak serta sebagai pusat pengatur gerak refleks.
b. Sistem Saraf Tepi
Sistem saraf tepi tersusun dari semua saraf yang membawa pesan dari dan ke sistem saraf pusat. Kerjasama antara sistem pusat dan sistem saraf tepi membentuk perubahan cepat dalam tubuh untuk merespon rangsangan dari lingkunganmu. Sistem saraf ini dibedakan menjadi sistem saraf somatis dan sistem saraf otonom.
1) Sistem saraf somatis
Sistem saraf somatis terdiri dari 12 pasang saraf kranial dan 31 pasang saraf sumsum tulang belakang. Kedua belas pasang saraf otak akan menuju ke organ tertentu, misalnya mata, hidung, telinga, dan kulit. Saraf sumsum tulang belakang keluar melalui sela-sela ruas tulang belakang dan berhubungan dengan bagian-bagian tubuh, antara lain
kaki, tangan, dan otot lurik. Saraf-saraf dari sistem somatis menghantarkan informasi antara kulit, sistem saraf pusat, dan otot-otot
rangka. Proses ini dipengaruhi saraf sadar, berarti kamu dapat memutuskan untuk menggerakkan atau tidak menggerakkan bagian-bagian tubuh di bawah pengaruh sistem ini.
Contoh dari sistem saraf somatis adalah sebagai berikut.
Ketika kita mendengar bel rumah berbunyi, isyarat dari telinga akan sampai ke otak. Otak menterjemahkan pesan tersebut dan mengirimkan isyarat ke kaki untuk berjalan mendekati pintu dan mengisyaratkan ke tangan untuk membukakan pintu.
Ketika kita merasakan udara di sekitar kita panas, kulit akan menyampaikan informasi tersebut ke otak. Kemudian otak mengisyaratkan pada tangan untuk menghidupkan kipas angin.
Ketika kita melihat kamar berantakan, mata akan menyampaikan informasi tersebut ke otak, otak akan menterjemahkan informasi tersebut dan mengisyaratkan tangan dan kaki untuk bergerak membersihkan kamar.
2) Sistem saraf otonom
Contohnya apabila kita kejatuhan cicak, kita merasa kaget ketakutan, dan menjerit keras. Jantung berdetak dengan cepat. Pikiran kacau. Reaksi yang membuat respon dalam situasi ketakutan ini dikontro oleh sistem saraf otonom. Sistem saraf otonom mengatur kerja jaringan dan organ tubuh yang tidak disadari atau yang tidak dipengaruhi oleh kehendak kita. Jaringan dan organ tubuh diatur oleh sistem saraf otonom adalah pembuluh darah dan jantung. Sistem saraf otonom terdiri atas sistem saraf simpatik dan sistem saraf parasimpatik. Sistem saraf simpati disebut juga sistem saraf torakolumbar, karena saraf preganglion keluar dari tulang belakang toraks ke-1 sampai dengan ke-12. Sistem saraf ini berupa 25 pasang ganglion atau simpul saraf yang terdapat di sumsum tulang belakang yang terletak di sepanjang tulang belakang sebelah depan, dimulai dari ruas tulang leher sampai tulang ekor. Masing-masing simpul saraf dihubungkan dengan sistem saraf spinal yang keluar menuju organ-organ tubuh seperti jantung, paru-paru, ginjal, pembuluh darah, dan pencernaan. Fungsi dari sistem saraf simpatik adalah sebagai berikut.
Mempercepat denyut jantung.
Memperlebar pembuluh darah.
Memperlebar bronkus.
Mempertinggi tekanan darah
Memperlambat gerak peristaltis.
Memperlebar pupil.
Menghambat sekresi empedu.
Menurunkan sekresi ludah.
Meningkatkan sekresi adrenalin
Sistem saraf parasimpatik disebut juga dengan sistem saraf kraniosakral, karena saraf preganglion keluar dari daerah otak dan daerah sakral. Susunan saraf parasimpatik berupa jaring-jaring yang berhubung-hubungan dengan ganglion yang tersebar di seluruh tubuh. Saraf parasimpatetik menuju organ yang dikendalikan oleh saraf simpatetik, sehingga bekerja pada efektor yang sama. Urat sarafnya menuju ke organ tubuh yang dikuasai oleh susunan saraf simpatik. Sistem saraf parasimpatik memiliki fungsi yang berkebalikan dengan fungsi sistem saraf simpatik. Misalnya pada sistem saraf simpatik berfungsi mempercepat denyut jantung, sedangkan pada sistem saraf parasimpatik akan memperlambat denyut jantung.
Tabel Perbedaan Fungsi sistem saraf simpatetik dan parasimpatetik.
Saraf Simpatik
Saraf Parasimpatik
Memperlebar pembuluh darah.
Memperkecil pembuluh darah.
Mempercepat denyut jantung.
Memperlambat denyut jantung.
Memperlebar pupil mata.
Memperkecil pupil mata.
Mempertinggi tekanan darah.
Memperendah tekanan darah.
Meningkatkan pernapasan.
Mengurangi pernapasan.
Meningkatkan kadar gula dalam darah.
Mengurangi kadar gula dalam darah.
Mengerutkan limpa.
Mengembangkan limpa.
4. Kelainan pada Sistem Saraf
Sistem saraf dapat mengalami gangguan atau kelainan. Beberapa contoh gangguan pada sistembuh) saraf manusia adalah sebagai berikut. a. Epilepsi, merupakan kelainan pada sel-sel saraf di otak sehingga penderita tidak dapat merespon berbagai rangsangan. Otot-otot rangka penderita sering berkontraksi secara tidak terkontrol. Epilepsi dapat disebabkan karena cacat sejak kelahiran, kelainan metabolisme, infeksi, adanya racun yang merusak sel-sel saraf, kecelakaan pada kepala, dan tumor. b. Neuritis, adalah luka pada neuron atau sel-sel saraf. Disebabkan oleh infeksi, kekurangan vitamin, karena pengaruh obat-obatan dan racun. c. Amnesia, atau penyakit lupa, yaitu sulit mengingat kejadian-kejadian yang telah berlalu. Amnesia dapat disebabkan karena goncangan batin atau cidera pada otak. d. Strok, adalah kerusakan otak akibat pecah, penyempitan, atau tersumbatnya pembuluh darah di otak. Strok sering terjadi pada orang yang menderita tekanan darah tinggi
