Muscles Flashcards
What is the cytoplasm called in muscle fibres?
Sarcoplasm
What is it called that muscle fibres have many nuclei?
Multinucleated
What is the cell membrane called in muscle fibres?
Sarcolemma
What surrounds myofibrils?
Sarcoplasm
Why do you nuclei need to be dotted all over sarcoplasm?
Transcription
All muscle cells controlled
What organelle will be in large number in sarcoplasm?
Mitochondria
RER
SER
Why is there lots of mitochondria in sarcoplasm?
ATP for contraction + protein synthesis
Why is there lots of RER in the sarcoplasm?
Protein synthesis
Why is there lots of SER in the sarcoplasm?
Storage of Ca2+ for contraction
Describe the structure of striated muscles
Individual filaments called myofibrils
Fuse together to form muscle fibres
When individual cells fuse together + microfibrils lay parallel
Each fibre shares sarcoplasm surrounding myofibrils
And sarcolemma
A single muscle cell = multinucleated
What do myofibrils consist of?
Actin
Myosin
Describe actin
Thinner
Made up of 2 strands coiled around each other
Describe myosin
Thicker
Consists of rod-shaped fibres with “bulbed heads”
Bulbed heads project outwards
What do myofibrils also contain?
Multiple sarcomeres
Banding pattern
What does the banding pattern of myofibrils cause?
Them to appear striped
What are the two main components of the sarcomere?
Dark bands
Light bands
What type of bands are dark bands?
Anisotropic bands
A - bands
What are the dark bands?
Actin + myosin overlap
What do the dark bands depend on?
Myosin length
What are the light bands?
No overlap
What type of bands are the light bands?
Isotropic bands
I - bands
What is the area called where there is only myosin filaments?
H - zone
What is the structure of an I - band?
Thin actin filaments only
What is the structure of the H - zone?
Thick myosin filaments only
What is the structure of an A - band?
Thick + thin filaments
How would you calculate the mean length of one sarcomere?
Measure the length from one z - line to another
Repeat + calculate
When a muscle contract what happens to the sarcomere?
It shortens
Patterns of light + dark bands change
Why do the patterns of the bands change when a muscle contracts?
Actin + myosin slide over each other
Why do the sarcomere shorten when the muscle contracts?
Sarcomere slides inwards = shortens
What are the 3 connective tissues?
Tendon
Ligament
Cartilage
What does the tendon connect?
Bone to muscle
What does the ligament connect?
Bone to bone
What does the cartilage connect?
Found between bones - “shock absorber”
What are muscles?
Bundle of fibres
Different structures
Different jobs
What are the three types of muscle?
Cardiac
Skeletal
Smooth
What is a cardiac muscle?
Present in the heart + acts involuntary (myogenic)
What is a skeletal muscle?
Attached to bones, vast majority of muscle, discontinuous contraction + controlled voluntarily
What is a smooth muscle?
Involuntary muscle, found in the gut, blood vessel walls + iris
Slow weak contraction
How do muscles act by?
Receiving nerve impulse
Work antagonistic pairs (do opposite jobs)
Pulling bones