Muscle Unit Flashcards
Types of Muscle Cells
- Skeletal (voluntary)
- Smooth
- Cardiac
Function of Muscles
- Produce movement
- Maintain posture
- Support soft tissues
- Protection
- Maintain body temperature
- Store nutrient reserves
Skeletal
Multinucleated with long large fibers
Cardiac
Branch shaped cells with intercalated disks (doesn’t need a nerve to activate)
What do muscle fascicles make up?
Skeletal Muscle
What do muscle fibers make up?
Muscle fascicle
What do myocytes make up?
muscle fibers
What do myofibrils make up?
myocytes
What makes up the myofibrils?
sacromers
What is the thick filament
Myosin
What holds myosin in place?
Titin
What is the thin filament? What does it do?
Actin ; it pulls myosin together
Tropmyosin
prevent the muscle from contracting at the wrong time
Troponin
promotes muscle contraction
A band
spans length of myosin fiber
I band
contains only actin fibers ; no myosin
H band
contains myosin fibers ; no actin
Z line
acts as anchor for actin fibers
M line
middle line (vertical medial line) to hold myosin in place
How does fiber shortening happen?
As sarcomeres shorten, muscle pulls together, producing tension
Which bands get smaller during muscle contraction?
I band
H band
Which site is not supposed to move?
Origin - attached to bon
Insertions
bone to bone
What is the first step of muscle contraction? Explain it
Signalling or Activation
- The neuromuscular junction activates it using acetylcholine
Neuromuscular junction
synapse gap where nerves talks to muscle (using neurotransmitters)
Neurotransmitter for Muscle
Activated by acetylcholine
Second Step of Muscle Contraction
- release calcium
-Binds to troponin (prevents contraction) to move it so actin is exposed
Where is calcium stored?
Sarcoplasmic reticulum
Third Step in Muscle Contraction
Uses ATP to get shorter
Rigor Mortis
Running completely out of ATP is only at death
Endomysium
connective tissue inside muscles
Perimysium
connective tissue surrounding muscle bundles
Epimysium
envelops entire muscles
What happens when the contraction cycle begins?
Arrival of calcium ions within the zone of overlap.
What happens when the active site is exposed
Calcium ions bind to troponin, blocking the contraction.
The troponin molecule then changes position, rolling the tropomyosin molecule away from the active sites on actin and allowing interaction with the energized myosin heads.
- myosin head attaches to actin
Cross Bridge Formation
Once the active sites are exposed, the energized myosin heads bind to them, pulling it towards the middle, forming cross-bridges.
Myosin Head Pivoting
The energy that was stored in the resting state is released as the myosin head pivots toward the M line
Power Stroke
- energy that was stored in the resting state is released as the myosin head pivots toward the M line
- when it occurs, the bound ADP and phosphate group are released.
What happens at cross bridge detachment
When another ATP binds to the myosin head, the link between the myosin head and the active site on the actin molecule is broken.
- The active site is now exposed and able to form another cross-bridge.
- Myosin head detaches from the actin
Agonist
prime mover
Antagonist
opposes movement of agonist
Synergist
- smaller muscle that assists larger agonist
Motor Units
- That contract at the same time
- can be big and small
Recruitment
multiple motor unit summation
Tetanus
maximum contraction
by all motor units
Isotonic Contraction
occur when the muscle changes length, producing limb motion.
- use same force
Isometric Contraction
- contractions in which there is no change in the length of the muscle
- holds at same place
What are the three major types of skeletal muscle fibers?
Fast fibers
Slow fibers
Intermediate fibers
Fast Fibers
- strong for short period of time
Slow Fibers
- slow for long periods of time
Intermediate Fibers
between slow and fast fibers
