13.9 Voluntary and involuntary muscles Flashcards
(21 cards)
What are the 3 types of muscle
Skeletal
Cardiac
Involuntary (smooth muscle)
What are skeletal muscles like
Fibre appearance striated, tubular and multinucleated
They are under conscious control
They are regularly arranged so muscle contracts in one direction
They are rapid and short contractions
What are cardiac muscles like
Fibre = specialised striated, branched and uninucleated
Under involuntary control myogenic
Cells branch and interconnect resulting in simultaneous contraction
The contractions are intermediate speed and length
What are involuntary muscles like
Fibres = non striated, spindle shaped and uninucleated
Under involuntary control
They have no regular arrangement and different cells can contract in different directions
Slow contractions and can stay contracted for a long time
Structure of skeletal muscles
Made up of many muscle fibres
These bundles of fibres are enclosed by a plasma membrane called sarcolemma
Parts of the sarcolemma are folded into transverse/ T tubules
How are skeletal muscles formed
The fusion of many individual embryonic cells, because of this there are many nuclei and a shared cytoplasm called the sarcoplasm this makes the so strong
Why do muscle fibres have lots of mitochondria
to provide the ATP that is needed for muscle contraction
What is the sarcoplasmic reticulum
the endoplasmic reticulum in muscle fibres, it contains calcium ions for muscle contraction
What gives the striated appearance
The alternating light and dark bands
What are the light bands
- I bands
- areas with only actin
What’s the sacromere
The distance between two adjacent z lines
What’s the z line
The centre of each light band
What’s the M line
The middle of the sacromere
What’s the H zone
- the centre of each dark band
- myosin only
- when muscles contract the H band decreases
What’s the dark band
The A band
Myosin overlapped with actin
What two types of protein filaments make up myofibrils
Myosin and actin
How are myofibrils arranged
parallel to provide maximum force when they all contract together
What’s actin like
The thinner filament it consists of two strands wrapped around each other
What’s myosin like
The thicker filament it consists of long rod shaped filaments with globular heads that project to one side
What else can be seen in microscope images of muscle
Streaks of connective tissues
Capillaries running in between fibres
What happens to lines and zones when muscles contract
Z lines get closer so sacromere shortens
H zone decreases
Light band becomes narrower
Dark band remains the same as myosin doesn’t shorten just that actin overlaps more
