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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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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Smooth Muscle Cell

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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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– 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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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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Muscle Comparisons

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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