Muscle Flashcards
Skeletal muscle
controls voluntary movements innervated by the somatic nervous system connects one bone to another bone stores large amounts of glycogen to use to power muscle contractions and provide heat to the body
tendon
Connective tissue that connects muscle to bone Can store elastic potential energy
Functions of muscle
- body movement 2. stabilization of body position 3. movement of substances through the body 4. generating heat to maintain body temperature
ligament
connective tissue that connects bone to bone
Smooth muscle and cardiac muscle
innervated by the autonomic nervous system control heart rate and blood pressure
sarcomere
the smallest functional unit of the contractile apparatus in skeletal muscle composed of many strands of two kinds of protein filaments: 1. thick filaments - made of myosin; 2. thin filaments - made of actin
thick filaments
One of two types of filaments that makes up a sarcomere Composed of several long myosin molecules wrapped around each other to form one thick filament Have myosin heads protruding along both ends of the thick filament
thin filaments
One of two types of filaments that make up a sarcomere Composed of actin Proteins troponin and tropomyosin are attached to the actin thin filament
troponin
A protein attached to the actin that aids in the mechanism of contraction. Binds calcium, causing a conformational change in troponin, which then pulls tropomyosin back and exposes the active site of the actin thin filament, allowing the myosin head to bind and form a cross bridge.
tropomyosin
A protein attached to the actin that aids in the mechanism of contraction. Covers the active site of the actin thin filament. Moves out of the way when calcium binds to troponin and troponin moves tropomyosin.
Z line
separates one sarcomere from the next and is where actin filaments attach
I band
The part of a sarcomere that contains actin only (includes the Z line)
H zone
The area containing myosin only
A band
The area where myosin is present, including where it overlaps with actin Includes the H zone
M line
The midline of the myosin fibers
myofibril
sarcomeres positioned end to end form a myofibril, each of which is surrounded by the specialized endoplasmic reticulum of the muscle cell, the sarcoplasmic reticulum.
sarcoplasmic reticulum
the endoplasmic reticulum of a muscle cell. The lumen is filled with Ca2+ ions
multinucleate
each muscle cell contains many nuclei
myocite/muscle fiber
several myofibrils wrapped together
fasciculus
Many muscle fibers bound together form a fasciculus
single muscle
Many fasciculi together make up a single muscle
Overall anatomy of muscle
Sarcomeres line up end to end to form myofibrils, which are wrapped together by the sarcolemma to form a muscle cell. Many muscle cells bound together form a fasciculus and many fasciculi form a muscle
Sliding Filament Theory
Actin and Myosin work together by sliding alongside each other to create the contractile force of skeletal muscle. Each myosin head crawls along the actin in a 5-stage cycle.
Important properties of myosin head
- Magnesium - ATP head 2. ATPase activity 3. A site for binding actin
Sliding Filament theory
The idea that myosin and actin work together by sliding alongside each other to create the contractile force of skeletal muscle
Cross Bridge
When the myosin head binds to the actin filament, we call this a cross bridge.
motor unit
consists of a neuron and the fibers in the muscle that it innervates. one neuron can innervate 2-2000 fibers. Small muscles have small motor units and large muscles, requiring more force, have larger motor units. [a small motor unit would be one neuron innervating 2 fibers; a large motor unit would be one neuron innervating 2000 fibers.]
Muscle fiber types
Type 1 and Type 2
Type 1
Type 1 – slow twitch – slow oxidative fibers –Highly aerobic –Contain mitochondria and ample myoglobin, which gives them a red color and makes them slow to fatigue –Have a relatively slow contractile velocity (speed of contraction) and produce a low amount of force
Type 2
Type 2 – fast twitch – fatigue quickly and are heavily glycolytic a. Type 2A – fast oxidative fibers –Also red, but they have a fast contractile velocity More resistant to fatigue than Type2B, but not as resistant as Type 1 b. Type 2B – fast glycolytic fibers –Low myoglobin content and thus appear white –Contract rapidly and can generate a lot of force, but fatigue quickly –Contain large amounts of glycogen
Muscle cell changes
–Muscle cells do not undergo mitosis generally –Muscles grow by increased diameter of the muscle fibers, increased numbers of sarcomeres and mitochondria, and lengthened sarcomeres
T tubules
have their origin on the cell surface and come down to branch into the cell. T-tubules carry the action potential deep inside the cell and interact with the sarcoplasmic reticulum to cause calcium release.
sarcoplasmic reticulum
–the endoplasmic reticulum of the muscle cell –Contains calcium to control contraction
nebulin
a structural protein in the sarcomere that helps align actin
Titan
a structural protein in the sarcomere that provides elasticity and stabilizes myosin
what happens to the bands in a sarcomere as muscle contraction occurs?
During muscle contraction, each sarcomere shortens as the thin filaments slide closer together between the thick filaments so that the Z lines are pulled closer together. The width of the A bands does not change as a muscle fiber shortens, but the I bands and H zones become shorter.
rigor state
When myosin and actin are bound but before ATP comes in to bind myosin and make it release. Rigor mortis results from no more ATP being produced in the body (b/c someone is dead) and therefore myosin does not release actin
