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Sistem muskuloskeletal
Pendahuluan
• Sistem muskuloskeletal diperankan oleh
– Organ otot
– Organ rangka/ tulang
– Sistem sendi : cairan sendi, ligament, meniskus, diskus, dll
• Sistem muskuloskeletal = lokomotoris, berarti otot menarik rangka untuk bergerak
• Fungsi muskuloskeletal gerakan
Otot : 40 – 50% total BB
Produksi Pergerakan Pergerakan bagian tubuh
Pergerakan darah dari jantung ke sistem sirkulasi
Pergerakan limfe
Pergerakan makanan di GIT
Pergerakan empedu
Pergerakan urine
Pergerakan semen di tr. Genital pria dan wanita
Pergerakan bayi partus
FUNGSI OTOT :
Sifat Otot :
• Kontraktilitas : kemampuan otot untuk memendek / berkontraksi (contract = counter to act) karena adanya filamen actin dan myosin
• Eksitabilitas : kemampuan otot untuk dirangsang (memberikan respond thd stimulus)
• Ekstensibilitas : kemampuan otot untuk diregang
• Elastisitas : kemampuan otot untuk kembali ke panjang awalnya sebelum diregang
Klasifikasi otot
Muscle Tissue Types
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Inc., publishing as Benjamin Cummings.
Skeletal Muscle
• Long cylindrical cells
• Many nuclei per cell
• Striated
• Voluntary
• Rapid contractions
Smooth Muscle
• Fusiform cells
• One nucleus
per cell
• Nonstriated
• Involuntary
• Slow, wave-like
contractions
Cardiac Muscle
• Branching cells
• One or two nuclei
per cell
• Striated
• Involuntary
• Medium speed
contractions
Otot
• Otot memiliki 2 karakter dasar, yaitu
– Jaringan kontraktil karena memiliki protein kontraktil, actin dan myosin
– Jaringan eksitabel karena memiliki sifat
• Bereaksi kalau dirangsang
• Menghantarkan rangsangan
Otot : jaringan kontraktil
• Contraction, to contract (counter to act)
• Otot seperti pegas gaya recoil
– Cenderung memendek
– Makin diregang, makin besar reaksinya (hukum Frank Starling)
Recoil force
F = k ∆x
Otot : jaringan kontraktil
• Otot memiliki filamen kontraktil – Tipis : actin, troponin &
tropomyosin
– Tebal : myosin
• Relaksasi, active site actin tertutup tropomyosin & troponin
• Kontraksi, active site actin terbuka & myosin menempel
Myofilament
• Filamen tipis : actin @ actin
@ troponin T,I,C
@ tropomyosin
• Filamen tebal : myosin
@ head/ kepala
@ hinge/ leher (engsel)
@ rod/ tubuh (batang)
Membentuk double helix dengan
active site tersembunyi
Z line Z line
H Band
Sarcomere Relaxed
Sarcomere Partially Contracted
Sarcomere Completely Contracted
Binding Site Tropomyosin
Troponin
Myosin
Neuromuscular Junction
Acetylcholine Opens Na+ Channel
troponin Tropomyosin
Relaksasi
Active site actin
tersembunyi
Kontraksi
Active site actin
tersekpose
MYOSIN
Relaksasi
Kontraksi (sliding)
Otot : jar eksitabel
• Kontraksi otot terjadi bila ada rangsangan dari akson saraf
• Hubungan akson saraf dengan otot disebut neuromuscular junction (NMJ)
• Tiap NMJ punya kepekaan yang berbeda
• Makin banyak NMJ yang aktif makin besar kontraksi otot yang dihasilkan
• Akson saraf melepaskan asetilkolin yang ditangkap reseptor di membran otot
Otot : jar eksitabel
• Asetilkolin yang tertagkap reseptor memicu potensial aksi pada membran otot
• Potensial aksi merambat hingga ke sisten TRIAD
– 1 t tubule, mrp invaginasi membran otot
– 2 sarcoplasmic reticulum (SR), gudang penyimpanan Ca2+
• Potensial aksi Ca2+ terlepas mengikat troponin C actin terbuka myosin nempel kontraksi
Hubungan otot & rangka
• Otot selalu melekat pada 2 bagian rangka
– Tulang yang relatif pasif dalam suatu gerakan disebut origo
– Tulang yang reralif aktif dalam suatu gerakan disebut insersio
• Origo & insersio berfungsi,
– Saat relaksasi, diam tak ada gerakan membentuk tonus & membentuk range of movement (ROM)
– Saat kontraksi menarik rangka & membentuk gerakan sesuai dengan tipe sendinya
Muscle Attachments
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Antagonistic Muscles
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Muscle Spindle
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Muscle Spindle Responses
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Alpha / Gamma Coactiviation
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Golgi Tendon Organs
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OTOT POLOS (SMOOTH MUSCLE)
Histologi :
• Berbentuk sekoci
• Berinti tunggal terletak di tengah
• Tidak berlurik (garis2 melintang)
Persarafan :
OTONOMIK : SIMPATIS, PARASIMPATIS
Pergerakan :
INVOLUNTER
KLASIFIKASI OTOT POLOS
Secara umum, otot polos terdiri dari 2 tipe :
Single – unit smooth muscle
(seringkali disebut visceral smooth
muscle).
Multi – unit smooth muscle (discrete
smooth muscle)
•Terdapat pada dinding
organ berongga: GIT
•Hub. Antar sel : gap
junction, sehingga
inervasinya tidak perlu
pada tiap sel
•Terdapat pd m.siliaris mata,
m.erector pilli, dsb
•Masing2 sel berdiri sendiri, inervasi
pada setiap sel
KONTRAKSI OTOT POLOS Perbedaan aktin dan myosin pada otot
polos dan otot rangka
Perbedaan Otot Rangka Otot Polos
Susunan Tidak teratur Teratur
Troponin Ada Tidak ada,
kalmodulin
Sumber
Ca2+ Cisternae
SR Interstitial/ekstra
seluler dan SR
Cisternae
SR Ada Tidak ada
KONTRAKSI OTOT POLOS
FUNGSI OTOT POLOS Sistem kardiovaskular :
Dinding pembuluh darah
regulasi aliran darah organ vital
Regulasi tekanan darah
Sistem digestive :
Sphincter : regulasi gerakan internal
Ubah kontraksi dan relaksasi gerakan makan oral ke anal
System Reproduktif
Males
Gerakan sperma sepanjang traktus reproduksi.
Sekresi komponen nonseluler semen
Ereksi dan ejakulasi
Females
Membantu gerakan ovum dan sperma sepanjang tract. reproduksi
Kelahiran
Properties of Smooth Muscle
– One nucleus
– Tropomyosin
– No troponin
– Dense bodies analogous to Z line
– Slow myosin ATPase
– Myosin has light chains
– Little sarcoplasmic reticulum
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Inc., publishing as Benjamin Cummings.
Smooth Muscle Cell
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Inc., publishing as Benjamin Cummings.
Excitation-Contraction Coupling
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Ca2+
Ca2+ Ca2+ Calmodulin
Phosphorylated
myosin light
chain
Unphosphorylated
myosin light
chain
Endoplasmic
reticulum
No myosin
ATPase activity
No crossbridge
activity
Myosin ATPase
active
Crossbridge
cycling
Contraction Smooth muscle cell
MLCK
Ca-calmodulin
Single-Unit Muscle
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Properties of Single-Unit Smooth Muscle
– Gap junctions
– Pacemaker cells with spontaneous depolarizations
– Innervation to few cells
– Tone = level of contraction without stimulation
– Increases/decreases in tension
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Inc., publishing as Benjamin Cummings.
– Graded Contractions
• No recruitment
• Vary intracellular calcium
– Stretch Reflex
• Relaxation in response to sudden or prolonged stretch
Multi-Unit Muscle
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Multi vs. Single-Unit Muscle
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Spontaneous Depolarizations
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Inc., publishing as Benjamin Cummings.
Figure 12.36
Rhythmic contraction
Tonic contraction
Smooth Muscle Regulation
• Innervated by autonomic nervous system
• Neurotransmitter are acetylcholine and norepinephrine
• Hormones important as epinephrine and oxytocin
• Receptors present on plasma membrane which neurotransmitters or hormones bind determines response
OTOT JANTUNG
• Functional Synctitium
O.k : antar sel dihubungkan oleh Desmosomes dan Gab junction
Cardiac Muscle
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Inc., publishing as Benjamin Cummings.
Muscle Comparisons
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Inc., publishing as Benjamin Cummings.
JENIS OTOT OTOT RANGKA
OTOT POLOS OTOT JANTUNG
BENTUK lurik polos lurik
SERABUT OTOT Sangat panjang, silindris
Spindel, serabut kecil
Terelongasi
NUKLEUS Banyak, di perifer Nukleus sentral terelongasi
Satu, central
KONTRAKSI Cepat, kuat Lamban, kuat Kuat dan berirama
KERJA volunter involunter involunter
Fenomena kelainan otot
• Tetani • Spasme • Muscle cramp • Kaku mayat • Myasthenia gravis • Paralisis • Parhese • Atrofi • Distrofi • Hipertrophy