Muscles Flashcards
Motor System
converts chemical
potential energy (ATP) into the kinetic
energy of muscle contractions.
-A muscle is any tissue that is capable of
contraction
-The motor system allows for body movement
Smooth Muscle
• Have one nucleus
• Long and tapered at the
ends
• Arranged in parallel lines
forming sheets
• Involuntary contraction
• Form walls of internal
organs
Cardiac Muscle
- Found only in the
heart
• Striated (Bands of
Light and Dark) and
branched
• One nucleus
• Contract involuntarily
Skeletal Muscles
-Tissue is striated - Looks like it has stripes
• Can be very long
• Many nuclei
• Contract Voluntarily
• Attached to bones
• Referred to as fibers
- can only pull when they contract
Antagonistic Pair
Contracts and relaxes at the same time in order to move joints
Hierarchy of Skeletal Muscles
Breakdown of Skeletal Muscles, from Most Complex to Simplest
___________ Muscles (Organ)______________ Fasicles- Bundles of Muscle Fibres/Muscle Cells (Tissue)
___________MuscleFibre(Cell)___________
Sarcolemma(Cell Membrane of Muscle Cell)
Sarcoplasm(Cytoplasm of Muscle Cell)
Sarcoplasmic Reticulum(Organelle of Muscle Cell)
Transverse Tubules(Contains bundles of Myofibrils)
Myofibrils(Organelle)(Bundles of Myofilaments)
Myofilaments(molecule)
Sarcomere (atom) (basic unit of a striated muscle)
muscle fibre
A single muscle cell
sarcolemma
the cell membrane of a muscle fibre.
sarcoplasm
the cytoplasm of a muscle fibre
Muscle
composed of
many bundles of muscle
fibres(fascicles)and associated
nerves and blood vessels.
Muscle Fibre
composed of myofibrils
Myofibrils
composed
two types of protein
myofilaments, actin and
myosin.
Actin
-thin filament
-Made of 2 actin myofilaments twisted together (2
strands of pearls)
• Has myosin binding-sites
• Has 2 regulatory proteins on it
Myosin
-thick filament
-Two strands of protein molecules wrapped around
each other
– 10 X bigger than actin and have a different shape
– Bundled so that half of the molecules have their
head facing one direction, the other half, the
opposite direction
-Has many myosin heads (which want to bind to actin)
• Powered by ATP
Sliding Filament Model
• In this model, the myosin filaments pull the actin filaments
inward, towards the M line.
• Since the actin molecules are attached to the Z lines, the Z lines
are pulled inward.
• Since the myofibrils are attached to the sarcolemma of the
muscle fibre, these contractions cause the entire muscle cell to
contract
WHICH SOURCE OF ENERGY DO WE USE FIRST?
- Creatine phosphate– Lasts for the first 8 sec,
fastest way to make ATP - Aerobic Respiration – Until Oxygen runs out
- Anaerobic Respiration – Can use this for
about 2-3 min until muscle cramping occurs
The Cross Bridge Cycle
- an action potential(nerve impulse)
triggers the sarcoplasmic reticulum to release calcium ions - Ca2+ is released by the sarcoplasmic reticulum
- Ca2+ binds to troponin
- The binding of Ca2+ causes troponin to change shape and roll tropomyosin off the myosin-binding
sites - The myosin head cocks, forming a cross-bridge between the myosin head and myosin-binding site
- Myosin pulls actin toward the M-line. This is called
the POWER-STROKE. - ATP binds to myosin, allowing it to break the cross-bridge. Steps 4 6 repeat as long as Ca2+ and ATP are present.
7.5. Myosin releases actin so that myosin can grab another binding-site and pull actin closer to the
M-line
Sarcomere
-Together the
myofilaments
make up a
sarcomere.
– Basic unit of
striated or
skeletal muscle
-when a sarcomere is relaxed,
tropomyosin is blocking the myosin-binding sites
on actin.
Cross Bridge
is formed when a
myosin head binds to a myosin-binding site on
actin.
Tropomyosin
Rod-like
• Stiffens and stabilizes actin (actin is like a wet noodle)
• Blocks myosin-binding sites when a muscle is relaxed
Troponin
Made of 3 subunits
• 1 subunit binds it to actin
• 1 subunit binds it to tropomyosin
• 1 subunit binds to calcium ions
