What are the three units of subcellular organization?
Conduction of electrical signals (sarcolemma), control of muscle contraction (sarcoplasmic reticulum), and contraction (myofibrils)
What is the fascia?
A web/network of connective tissue made of collagen and elastin
Describe “control”
Sarcoplasmic reticulum stores calcium, not much leaks out but over time it will need to be replenished
Describe a triad
T-tubules, terminal cisternae, and sarcoplasmic reticulum, all work together to release calcium
Describe “contraction”
Myofibrils (longitudinal bundles of protein filaments) use actin and myosin to become sarcomeres
What is the functional unit of muscle?
Sarcomere
What happens when a muscle fully contracts?
The h zone and I band decreases, the a band stays the same
The protein that makes the z line is
Alpha-actinin
What does titin do
Allows muscle to go back to its original state
Describe conduction
Sarcolemma has a phospholipid bilayer, t-tubules run transverse to sarcolemma, allows electrical conduction to get around every myofibril
How does troponin unbind from tropomyosin?
Calcium binding
Describe myosin
Has a head and tail, actin-binding site, and myosin ATPase site
Describe actin
Forms a helix called fillamentis actin, has a binding site for attachment with myosin crossbridge, attached to z line and troponin/tropomysosin associated with thin filament
What is the basic function of muscle?
Generate tension between different points
List some functions of skeletal muscle
Locomotion, facial expression, posture, control of body openings/passages, regulation of body temperature, and metabolism and endocrine functions
What is dystrophin?
Prevents injury to muscle during contraction, translates force from sarcomere to the bone
How does the muscular system and the endodcrine system work together?
Muscle contraction releases hormones
Why is skeletal muscle contraction voluntary?
It requires nervous system input
Do muscles pull or push on bones?
Always pull on bones
What is a muscle origin? Insertion?
Origin: place where muscle starts on a bone
Insertion: place where muscle ends on a bone
When is crossbridge formation possible?
When thick filaments overlap with thin filaments
Describe flexion of a muscle
Flexing the muscle, reduced angle between the joint
Describe extension of a muscle
Extending a muscle, increases the angle of a joint
What is reverse muscle action?
The insertion is fixed and the origin moves towards it (pull ups)
