Muscular system Flashcards
Describe skeletal muscle
Striated muscles that move bones around joints
Describe smooth muscle
Non-striated muscles located in the walls of hollow organs, blood vessels + glands
Describe cardiac muscle
Striated muscle cells that make up walls of heart
List the 6 functions of the muscular system
- body movement
- maintenance of posture
- respiration
- production of body heat
- communication
- control of blood flow
Describe the muscle fascicle
Bundle of cells
- contain muscle fibres
- contained in skeletal muscle organ (many)
Describe the muscle fibre (cells)
- contain many mitochondria
- sarcolemma = muscle fibre cell wall
- myofibrils = surrounded by sarcoplasm
List the components of a sarcomere + their functions
Actin = thin filaments
Myosin = thick filaments
Interact to cause muscle shortening -> contraction
What filament includes troponin + tropomyosin + what are their functions
Actin
Cover G-actin molecules (contain active site)
Describe the role of calcium in muscle contraction
Causes exposure of myosin binding sites on actin therefore acting as ‘on switch’ by binding to troponin complex
State the role of ATP in muscle contraction
Provides energy for filaments to slide over each other by causing myosin heads to bind + swivel, dragging filaments along
Describe the 6 steps of the contraction cycle
- contraction cycle begins
Calcium arrives within the zone of overlap in a sarcomere - active site exposure
- calcium binds to troponin, weakening the bond b/t the actin + the troponin-tropomyosin complex
- troponin molecule then changes position, rolling the tropomyosin molecule away from the active sites on actin + allowing interaction w/ energised myosin heads - cross bridge formation
once the active sites are exposed, energised myosin heads bind to them -> form cross bridges - myosin head pivoting
- energy stored in resting state released as myosin heads pivot towards m line
-> power stroke = bound ADP and phosphate group released - cross bridge detachment
- when another ATP binds to the myosin head, the link b/t the myosin head + active site on actin molecule is broken
- a/s now exposed + able to form another cross bridge - myosin reactivation
- occurs when free myosin head splits ATP into ADP and pi
- energy released used to re-cock myosin head
List + describe the 5 steps that end a muscle contraction
- Ach is broken down
- ends action potential generation - sarcoplasmic reticulum reabsorbs ca2+
- conc. in cytosol decreases - A/s covered + cross bridge formation ends
- no ca2+ means tropomyosin returns to normal place - contraction ends
- no cross bridges formed - muscle relaxation occurs
- returns passively to resting length
Distinguish b/t the structure + function of slow + fast twitch muscle fibres
Slow twitch = less power
-> decreased myofibrils, increased mito. + myoglobin
Fast twitch = more power
-> increased myofibrils, decreased mito.
List the components of a motor unit
- somatic motor neuron + muscle fibres that function together
- 1 axon terminal on each fibre
- each motor neuron has terminals on many fibres
What effect does endurance training have on muscle
- increased size + number of mitochondria
- increased number of blood capillaries supplying area
