Lecture 5 - Exercising Muscles 1 Flashcards
three types of muscle tissue
Smooth muscle
- > involuntary, hollow organs
Cardiac muscles
- > involuntary, heart
Skeletal muscle
- > voluntary, skeleton
Parts of skeletal muscle
Entire muscle
- > epimysium
*consists of many bundles (fasciculi)
Fasciculi
- > surrounded by perimysium
*consists of individual muscle cells/fibres
Muscle fibres
- > surrounded by endomysium
*consists of myofibrils divided into sarcomeres
parts of the muscle fibre and what they do
Plasmalemma (cell membrane)
- > fused with tendon
- > conducts AP
- > maintains pH and transports nutrients
Satellite cells
- > muscle growth and development
- > responds to injury, immobilization and training
Sarcoplasm
- > cytoplasm of muscle cell
- > unique features: glycogen storage and myoglobin
Transvers Tubules
- > extensions of plasmalemma
- > carry AP deep into muscle fibre
Sarcoplasmic Reticulum (SA)
- > Ca storage
myofibrils vs sarcomeres
Myofibrils
Muscle - > fasciculi - > muscle fibre - > myofibril
*hundreds of thousands per muscle fibre
Sarcomere
- > basic contractile element of skeletal muscle
- > end to end for full myofibril length
components of a sarcomere
distinctive striped/striated appearance
A-bands
- > dark stripes
I-Bands
- > light stripes
H-Zone
- > middle of A-Band
M-Line
- > middle of H-zone
characteristics of actin and myosin
Actin (thin filament)
- > shows up lighter under microscope
- > I-Band contains only actin filaments
Myosin (thick filaments)
- > shows up darker
- > A-band contains both actin and myosin fil.
- > H-zone contains only myosin fil.
parts of myosin
*two intertwined filaments with globular heads*
Globular heads
- > protrude 360deg from thick filament axis
- > will interact with actin for contraction
Stabilized by tintin
composition of actin/thin filaments
composed of 3 proteins
Actin
- > contains myosin binding site
Tropomyosin
- > covers active site at rest
Troponin
- > anchored to actin, moves tropomyosin
*anchored at Z-disc and equally spaced out my tintin*
alpha motor neuron
innervate muscle fibres
motor unit
comprised of single alpha motor neuron and all fibres it innervates
- > more operating motor units = more contractile force
neuromuscular juntion
site of communication between neuron and muscle
- > consists of synapse between alpha motor neuron and the muscle fibre
explain excitation-contraction coupling (muscle fibre contraction)
- AP stars in brain
- AP arrives at axon termina, releases ACh
- Ach crosses synapse, binds to Ach receptors on plasmalemma
- AP travels down plasmalemma to T-Tubules
- This triggers Ca release from SR
- Ca eneables actin-myosin contraction
role of Ca in muscle fibres
When AP arrives at SR from T-Tubules
- > SR are sensitive to electric charge so this causes mass release of Ca into sarcoplasma
Ca binds to troponin on thin filament
- > tropomyosin-Ca complex moves tropomyosin
- > myosin binds to actin, causing contraction
described the relaxed state of a muscle contraction
- > no actin-myosin interaction at binding site
- > myofilaments overlap a bit
describe the contracted state of a muscle fibre
- > myosin head pulls actin towards sarcomere centre (powerstroke)
- > filament slide past each other
- > sarcomeres, myofibrils, muscle fibres all shorted
