Energi pada kontraksi jantung

ENERGI PADA
KONTRAKSI JANTUNG
HUSNIL KADRI
Fakultas Kedokteran Unand
Padang
3 JENIS JARINGAN OTOT
2
OTOT JANTUNG
OTOT JANTUNG
CARDIAC MUSCLE
20-5
OTOT JANTUNG
–selnya bercabang dan mengandung 1 – 2
nukleus ditengahnya
 Myofilament actin dan myosin
 Intercalated disks: Specialized cell-cell contacts
 Desmosomes hold cells together and gap junctions
allow action potentials
20-6
 Sel
GAP JUNCTIONS
 small
pores in the center of each gap
junction
 allows ions and small peptides to flow from
one cell to another
 action potential is propagated to adjacent
muscle cells
Heart behaves as a single motor unit
THEORETICALLY,
AN ION INSIDE AN SA NODAL CELL
COULD TRAVEL THROUGHOUT THE HEART
VIA THE GAP JUNCTIONS
Sperelakis N, Kurachi Y, Terzic A, Cohen MV.
Heart Physiology and Pathophysiology
Academic Press, 2001
MITOCHONDRIA
 Membangkitkan
energi dalam bentuk
adenosine triphosphate (ATP)
 Menjaga fungsi kontraksi jantung dan
berhubungan dengan gradien ion
THICK & THIN MYOFILAMENTS
PROTEIN OTOT
 Myofibrils
terdiri dari 3 protein:
1. contractile proteins
- myosin and actin
2. Proteins pengatur kontraksi
- troponin and tropomyosin
3. Protein struktural
- titin, myomesin, nebulin and dystrophin
MYOSIN

Many different types
Myosin V  vesicle transport
 Myosin II  skeletal and cardiac muscle contraction

ACTIN FILAMENTS:
 Polymer
of G-actin (43 kDa globular
protein)
 ‘thin filaments’ in muscle
2 SUMBER CALSIUM PADA OTOT JANTUNG
CARDIAC VS SKELETAL MUSCLE
 More
sarcoplasm and mitochondria
 Larger transverse tubules located at Z discs
 Less well-developed SR
 More Ca+2 enters cell from extracellular fluid
during contraction
 Prolonged delivery of Ca+2 to sarcoplasm, produces
a contraction that last 10 -15 times longer than in
skeletal muscle
PHYSIOLOGY OF CARDIAC MUSCLE
 Contracts
without stimulation
 Contracts 75 times per min & needs lots O2
 Larger mitochondria generate ATP aerobically
 Sustained contraction possible due to slow Ca+2
delivery
 Ca+2 channels to the extracellular fluid stay open
MUSCLE METABOLISM:
ENERGY FOR CONTRACTION
 Muscle
cells need to generate large amounts of
available energy during contractions
 Muscle
cells have three ways to produce ATP:
Aerobic cellular respiration
 Anaerobic cellular respiration
 Creatine phosphate

CARDIAC MUSCLE METABOLISM
CREATINE PHOSPHATE IN MUSCLE CELLS
Resting muscle cells store excess energy in
creatine phosphate
 During exercise cells can quickly replenish
their ATP supply using creatine-phosphate
 This supply of energy is only large enough for
short bursts of activity (about 15 seconds)

ANAEROBIC METABOLISM IN MUSCLE CELLS
 For
short time periods muscle cells can make ATP
by glycolysis alone
 The
pyruvate is converted into lactic acid and enters
the blood if there is no oksigen (anaerobic)
 This
source of ATP can only power muscle cells for
about 30-40 seconds
KEPUSTAKAAN
Akar AR. Cardiac Physiology (IV). Ankara University
School of Medicine. Desember 2003. download 2011
 Jenkins, Kemnitz, Tortora. Chapter 10 Muscle Tissue.
Anatomy and Physiology. John Wiley & Son, inc.
download 2011
 Cardiovascular System: Heart. download 2011
 Chapter 6 Histology. download 2011
 Structure and Function of Skeletal Muscle. download
2011
 Khan R. Year I Tutorial: Musculoskeletal System.
download 2011.
 Murray RK. Muscle & the cytoskeleton. In:Harper’s
Illustrated Biochemistry. 27th ed. pp 565-587
