Voluntary And Involuntary Muscles Flashcards
what are the three types of muscle?
- smooth
- skeletal
- cardiac.
how is cardiac muscle myogenic?
it contracts without the need for a nervous stimulus, causing the ehart to beat in a regular rhythm.
what are some features of skeletal muscle?
- fibre appears striated.
- regularly arranged so muscle contracts in one direction.
- the contraction speed is rapid.
- short length of contraction.
what is the structure of skeletal muscle?
muscles showin cross striations are known as striated muscles.
fibres are tubular and multinucleated.
what are some features of cardiac muscle?
- appear to be specialised striated.
- involuntary muscle
- arranged wherby cells branch and interconnect resulting in simultaneous contraction.
- intermediate contraction speed.
- intermediate length of contraction.
what is the structure of cardiac muscle?
cardiac muscle shows striations but they are fainter than skeletal muscle.
fibres are branched and uninucleated.
what are some features of smooth muscle?
- non-striated
- involuntary
- they have no regular arrangement so different cells can contract in different directions.
-slow contraction speed.
- they can remain contracted for a relatively long time.
what is the structure of smooth muscle?
muscles show no cross striations
fibres are spindle shaped and uninucleated.
what are skeletal muscles made up of?
bundles of muscle fibres.
what is the name of the plasma membrane that encloses the bundles of muscle fibres called?
sarcolemma.
what makes skeletal muscle strong?
muscle fibres contain a number of nuclei and are much longer than normal cells. the junction between adjacent cells would have acted as a point of weakness but it isnt present so it’s strong.
what is the sarcoplasm?
the shared cytoplasm witin a muscle fibre.
why does the whole fibre recieve the impulse to contract at the same time?
parts of the sarcolemma (plasma membrane) fold inwards to help spread electrical impulses throughout the sarcoplasm (cytoplasm)
what is the name of the folds on the sarcolemma?
transverse tubules (T tubules.)
what are some adaptations of muscle fibres?
- lots of mitochondria to provide ATP needed for muscle contraction.
- modified version of endoplasmic reticulum containing calcium ions required for muscle contraction.
what is the name of the modified version of endoplasmic reticulum?
sarcoplasmic reticulum.
what are myofibrils?
long cylindrical organelles made of protein.
what makes myofibrils so powerful?
they are lined up in parallel to provide maximum force when they contract together.
what are the two types of protein filament that myofibrils are made up of?
- actin
- myosin
what is actin?
the thinner protein filament that makes up myofibrils. it consists of two strands twisted around each other.
what is myosin?
the thicker protein filament. It consists of long rod shaped fibres with bulbous heads that project to one side.
what causes the striped look in myofibrils?
myofibrils have alternating light (I bands) and dark bands (A bands)
what are light bands (I bands) ?
they appear light as they are the region wher actin and myosin filaments do not overlap.
what are dark bands (A bands) ?
these appear dark because of the presence of thick myosin filaments. edges particularly dark as myosin is overlapped with actin.
what is the Z-line?
the line found at the centre of each light band. sacromere between them.
what is a sacromere?
the distance between adjacent Z-lines. it is the functional unit of the myofibril. when a muscle contracts, the sacromere shortens.
what is the H zone?
the lighter region found in the centre of each A band. only myosin filaments are present here. when the muscle contracts, the H zone decreases.
