Unit 1. Lec 3- Skeletal and Smooth Muscle Physiology Flashcards
What are the 3 types of muscles
- Skeletal
- Smooth
- Cardiac
Which muscle makes up most of the muscles in the body?
Skeletal muscle
Describe the physical apperance of skeletal muscle
- Is straited, appears to have stripes
- NOT uniform
Large muscle bundles are composed of what?
Myocytes or fibers (individual muscle cells)
What does each myocyte contain?
Many myofibrils
What does each myofibrils contain?
Many sacromeres (smallest functioning unit of muscle)
How are sacromes arranged?
end-to-end in series
What is each sacromere composed of?
- Actin
- Myosin
- Other moleculary machinery
List the cellular units of skeletal muscle from largest to smallest
Myocyte–>Myofibrils–>sacromeres (actin/myosin)
What is the function of individual sacromeres?
To generate contractile forces
What is one sacromere bounded by?
2 Z-lines
What are the two types of filaments in skeletal muscle?
- Thin Filaments (Actin)
- Thick Filaments (Myosin)
What are the thin filaments of Skeletal Muscle?
Actin helix w/ tropomyosin & troponin complex attached
What are thick filaments of Skeletal Muscle?
- Myosin II (ATPase b/c breakdown ATP for energy)
- Head and tail and it’s a alpha helix except the head
Thin and thick filaments interact to produce _________.
force
What is the organization of a sarcomere?
- I band: thin filaments only (actin only)
- H band: thick filaments only (myosin only)
Explain the M line and A band of the sarcomere
- M line: thick filaments linked w/ accessory proteins
- A band: thick and thin filaments overlap
A>H zone
What increases the overlap btw myosin and actin?
Decreasing I band & H zone
Explain the neural control of skeletal muscle cells
Neuromuscular Junction:
1. Nerve axon innervating each muscle fiber
2. Release Acetylcholine (ACh) from vesicles
3. ACh binds to AChR (receptor) which is permeable to Na+, K+, and Ca2+
What is the role of Acetylcholinesterase?
Breaks down ACh to decrease ACh in synpases to stop contraction
How are muscle cells innervated?
Each muscle is innervated by one nerve
What causes depolarization in skeletal muscle cells?
ACh receptors
Explain the Initation of Skeletal Muscle Contraction
- Ca2+ release from the Sacroplasmic reticulum
- Ca2+ binds to Troponin complex and initiates a conformational change
- Tropomyosin (which initially was blocking the binding site) slides into the groove btw the actin strands
- Myosin can now bind actin
Troponin complex (accesory proteins bound too tropomyosin & actin)
