ENERGI PADA KONTRAKSI JANTUNG

HUSNIL KADRI Fakultas Kedokteran Unand

Padang

2

3 JENIS JARINGAN OTOT

OTOT JANTUNG

OTOT JANTUNG

20

-5CARDIAC MUSCLE

20

-6

OTOT JANTUNG

Sel –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

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 PathophysiologyAcademic 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 actin2. Proteins pengatur kontraksi

- troponin and tropomyosin3. 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 deliveryCa+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 respirationAnaerobic cellular respirationCreatine 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