neuromuscular junction, which is discussed in Chapter 7, can diminish at least a small amount after intense prolonged muscle activity, thus further diminishing muscle contraction. Interruption of blood flow through a contracting muscle leads to almost complete muscle fatigue within 1 or 2 minutes because of the loss of nutrient supply, especially loss of oxygen. Lever Systems of the Body. Muscles operate by applying
tension to their points of insertion into bones, and the bones in turn form various types of lever systems. Figure 6–14 shows the lever system activated by the biceps muscle to lift the forearm. If we assume that a large
muscles, and it is controlled by the motor control centers of the brain and spinal cord. The position of each separate part of the body, such as an arm or a leg, is determined by the relative degrees of contraction of the agonist and antagonist sets of muscles. For instance, let us assume that an arm or a leg is to be placed in a midrange position. To achieve this, agonist and antagonist muscles are excited about equally. Remember that an elongated muscle contracts with more force than a shortened muscle, which was demonstrated in Figure 6–9, showing maximum strength of contraction at full functional muscle length and almost no strength of contraction at half normal length. Therefore, the elongated muscle on one side of a joint can contract with far greater force than the shorter muscle on the opposite side. As an arm or leg moves toward its midposition, the strength of the longer muscle decreases, whereas the strength of the shorter muscle increases until the two strengths equal each other. At this point, movement of the arm or leg stops. Thus, by varying the ratios of the degree of activation of the agonist and antagonist muscles, the nervous system directs the positioning of the arm or leg. We learn in Chapter 54 that the motor nervous system has additional important mechanisms to compensate for different muscle loads when directing this positioning process.
Sistem Muskuloskeletal Yuliati
Figure 6–14 Lever system activated by the biceps muscle.
Remodeling of Muscle to Match Function
All the muscles of the body are continually being Departemen Biologi Oral remodeled to match the functions that are required of
Sistem Muskuloskeletal Semua fungsi fisik tubuh melibatkan otot, misal: gerak tubuh, denyut jantung, kontraksi pembuluh darah dll Otot rangka menyusun 40% tubuh Komponen Sistem Muskuloskeletal a. bones b. muscles c. ligament d. tendons e. nerves → biological and mechanical system. Bones – internal framework Muscles – generate force and movement Ligaments – connect bones Tendons – connect muscles to bone
Fungsi Sistem muskuloskeletal 1. Memberi bentuk tubuh, 2. Melindungi organ dalam, 3. Menyimpan mineral kalsium dan fosfat, 4. Tempat melekatnya otot, 5. Sebagai pengungkit (tuas) dalam pergerakan sendi, 6. Mengandung sumsum tulang tempat pembentukan sel darah, 7. Menghasilkan panas tubuh
SKELETAL MUSCLE
Struktur Otot Skeletal
Muscle
A
Inervasi pada muscle fiber dilakukan oleh :
Muscle fasciculus
B
C H band
Z disc
A band
Sistem Saraf Motorik Somatik
Muscle fiber
I band
86 Myofibril
Z Sarcomere Z
D
Unit II
Myelin sheath
G-Actin molecules H
J
Membrane Physiology, Nerve, and Muscle
Axon
Terminal nerve branches Teloglial cell
Myofilaments
Muscle nuclei
Myofibrils F-Actin filament
K L
E
A
B
Myosin filament Myosin molecule
Synaptic vesicles
M
Axon terminal in synaptic trough
N F
G
osin filaments. The Z disc, of filamentous proteins difd myosin filaments, passes bril and also crosswise from ching the myofibrils to one the muscle fiber. Therefore,
H
I
Light meromyosin
Heavy meromyosin
beginning to overlap one another. We will see later that, at this length, the muscle is capable of generating its greatest force of contraction. What Keeps the Myosin and Actin Filaments in Place? Titin Filamentous Molecules. The side-by-side rela-
C
Subneural clefts
Neuromuskular Junction Adalah sinap ( hubungan ) antara ujung saraf motorik A dengan sarcolemma muscle fiber
Kerja Otot Kontraksi otot melawan beban Energi dipindah dari otot ke beban eksternal Energi berasal dari reaksi kimia dalam sel otot Unit II
Membrane Physiology, Nerve, and Muscle
Macam kontraksi otot
Kontraksi Otot
a. Isometrik :
Normal range of contraction
panjang tetap, tonus berubah D B C
b. Isotonik :
C A
Phenomena kontraksi ☻Summasi ☻Tetani ☻Treppe
D
1 ( stair 2 case phenomena 3 4 Length of sarcomere (micrometers)
)
Tension during contraction
Tension of muscle
B tonus tetap, panjang berubah A
Increase in tension during contraction
Tension before contraction D 0 1/2 normal
Normal Length
2x normal
Tulang Komponen Pembentuk Tulang Mikroskopis tulang : bahan organik (30%) & mineral (70%)
1. Bahan organik tulang
2. Mineral
a. Matrik tulang : 98% bhn organik tulang
95% terdiri dari hidroksiapatit kristal kalsium fosfat.
kolagen (95%) protein non-kolagen (5%)
b. Sel tulang : sebesar 2% osteoblas, osteosit dan osteoklas
Struktur Histologis Setiap jenis tulang terdiri atas a. Kortikal : 80 - 90 % vol termineralisasi b. Trabekula : hanya 20% vol termineralisasi - sebag besar terdiri atas sumsum - mengandung lemak dan/atau jar hematopoetik
Tulang panjang
Sel-sel Tulang
1. Osteoblas peran : produksi kolagen & mukopolisakarida.
2. Osteosit sel tulang yg tertanam matrik yg termineralisasi peran : sintesa matrik
3. Osteoklas sel yang dapat bergerak ( motil ) → dapat berpindah peran : resorbsi tulang
Hubungan Osteoblas, Osteoklas dan Osteosit Pada Matriks Tulang
Sumber Energi Kontraksi Chapter 84 Sports Physiology I. Phosphocreatine
Creatine + PO3-
II. Glycogen
Lactic acid
III. Glucose Fatty acids Amino acids
+ O2
ms e
become available. Removal erts the ATP into adenosine
CO2 + H2O + Urea
1057
ATP
ADP
Energy for muscle contraction
AMP
glycolysis, occurs without use of oxygen and, therefore, is said to be anaerobic metabolism (see Chapter 67).
Metabolisme Aerob
• Tjd peristiwa oksidasi reaksi dg O • Energi hasil reaksi oksidasi tiap bhn mknan 2
( kh, prot., lemak ) dg 1 liter O2 : a. karbohidrat 5 kkal b. lemak 4,7 kkal c. protein 4,5 kkal
Reaksi : glukosa
O2
CO2 + H2O + 36 ATP
Metabolisme Anaerob
• • •
Metabolisme tanpa O2 Fungsi : penyediaan energi mendesak Hanya berlangsung pd karbohidrat ATP lebih <
Reaksi : glukosa
as.laktat + 2 ATP
Asam Laktat
• M’pengaruhi pH cair tubuh kerja enzim terganggu Diubah as.Piruvat
- dibakar/oksidasi (20%) - diubah jadi glukosa (80%) energi metab.aerob
Kelelahan Otot Muscle Fatique
•
Otot bekerja maksimal : posisi keseimbangan, misalnya : kepala, leher dan tulang belakang berada pd satu garis lurus → pengaruh gaya gravitasi
•
Akibat kontraksi otot terus menerus dalam waktu yang lama.
•
Kontraksi makin lemah akibat kekurangan ATP
Tipe kelelahan fatigue : kegagalan hub saraf-otot dalam • Transmission menghantarkan impuls. Penyebab : turunnya sekresi neurotransmiter atau daya ikat reseptor neurotransmiter
•
Central fatigue : sistem saraf pusat tidak dapat
•
Muscle fatigue : kurangnya energi untuk kontraksi
menyalurkan impuls pada saraf motorik
( ATP, kreatin fosfat ), terjadi akumulasi asam laktat
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