Contraction of skeletal muscle Flashcards
How do skeletal muscles bring about movement?
By pulling on bones via tendons, since bones are incompressible
What are joints, and what is their role in movement?
Joints are points where different parts of the skeleton move relative to each other, allowing controlled movement
Why can a muscle only move a bone in one direction?
Muscles can only move bones in one direction because they can only pull, they cannot push
How is a movement in the opposite direction achieved?
A second muscle is required, working antagonistically to the first muscle
What is meant by antagonistic muscle pairs?
A pair of muscles that work oppositely, where one contracts while the other relaxes
What happens to the relaxed muscle in an antagonistic pair?
It is stretched by the contracting muscle, returning it to its original state and preparing it for the next contraction
What happens to the I-band when a muscle contracts?
It becomes narrower due to the increased overlap of actin and myosin
What happens to the Z-lines during muscle contraction?
They move closer together, causing the sarcomere to shorten
What happens to the H-zone during contraction?
It becomes narrower as actin filaments slide over myosin filaments
What happens to the A-band during contraction, and why is this significant?
It remains the same width, proving that myosin filaments do not shorten, supporting the sliding filament theory
What are the two components of myosin?
- A fibrous protein tail made up of multiple molecules
- A globular protein head with two bulbous structures
What is actin, and how is it structured?
A globular protein arranged into long twisted chains forming a helical strand
What is the role of tropomyosin?
It frms long thin threads wound around actin filaments, regulating binding sites for myosin
What happens after myosin heads attach to actin?
They flex in unison, pulling the actin filaments along the myosin filaments
How do myosin filaments interact with actin filaments during muscle contraction?
The bulbous myosin heads form cross - bridges by attaching to binding stirs on actin filaments
How do myosin heads detach from actin?
They use ATP to detach and return to their original position
What happens after myosin heads to return to their original position?
They reattach further along the actin filament and repeat the process
