Muscular system continued Flashcards
What are fascicles?
Bundles of muscle fibers (cells) wrapped with connective tissue
What is the sarcomere?
The muscle contractile unit
Myosin
Forms thick filaments
Actin
Forms thin filaments
Z lines
Attachments points for sarcomeres
What happens to the sarcomeres when muscle contraction happens?
They shorten a little
Process of contraction
- Skeletal muscle must be activated by a nerve
- Nerve activation increases the concentration of calcium ions in the vicinity of the contractile proteins
- Presence of calcium permits contractions
- When nerve stimulation stops, contraction stops
Nerves activate skeletal muscles
true or false
True
What is contraction?
formation of cross-bridges between thin and thick filaments
Ca++ does not need to be present for cross-bridges to form
True or false
False
Calcium must be present for cross-bridges to form
Muscles require energy to contract and relax
true or false
True
What is the principle source of energy?
ATP
ATP is not required for contraction
True or false
False, it is required
ATP is required for relaxation
True Or false
True
How is ATP replenished?
- Creatine phosphate
- Stored glycogen
- Aerobic metabolism of glucose, fatty acid, and other high-energy molecules
What is muscle tension?
Mechanical force that muscles generate when they contract
What is muscle tension determined by?
- Number of active motor units
- Motor unit size
- Frequency of stimulation of motor units
All -or-none principle
Individual muscle cells are completely contracting or are relaxed
Muscle tone
Whole muscles maintain intermediate level of force known as muscle tone
Recruitment
Activation of ADDITIONAL motor units increases muscle tone
Slow twitch
- Contract slowly
- Many mitochondria
- Well-supplied with blood vessels
- Used for endurance activities
-Make ATP as needed by aerobic metabolism
Fast twitch
- Contract quickly
- Fewer mitochondria
- Little to no blood vessels
- Used for brief high-intensity activities
