Specialised effectors that bring about movement through contraction
1 of 30
Skeletal(voluntary)muscle is attached via... to the skeleton?
Attached via the tendons
2 of 30
What is the structure of skeletal muscle?
-Many muscle fibres bunched together
-Surrounded by sarcolemma
-Multinucleate
-Rich in mitochondria
-Sacrolemma folds deeply inwards to from T-tubules
3 of 30
What is the bulk of the muscle fibre filled with?
Highly specialised contractile units called MYOFIBRILS
4 of 30
What is the ultrastructure of myofibrils?
-Two types of protein(myosin&actin)
-Myosin forms thick filaments
-Actin forms thin filaments
5 of 30
Where do myosin filaments lie ?
Within the central region of each contractile unit and are linked together by a thin disc(M-LINE)
6 of 30
Where do the actin filaments lie and held together by?
Between the outer edges of the myosin filaments and held together by a thin disc(Z-LINE)
7 of 30
What is a section of myofibril between 2 Z-lines called?
Sacromere
8 of 30
What type of striations do myosin filaments form?
Denser&darker striations
9 of 30
What type of striations do actin filaments form?
Less dense/lighter regions
10 of 30
What does the anisotropic band(A-band) contain?
Contains myosin&areas in which thinner actin filaments penetrates between the myosin filaments
11 of 30
What band contains the actin?
The isotropic band(I-band)
12 of 30
What is the H-zone?
Zone in the centre of the A-band where there's myosin only
13 of 30
What is the sliding filament theory?
The myosin and actin filaments slide past each other so reducing the overall length of the sarcomere.
14 of 30
What happens when the muscle is not contracting?
The actin binding sites are blocked by another ancillary protein(tropomyosin)to prevent binding
15 of 30
Where doe the action potential come from before stimulating the muscle fibre?
The motor neurone
16 of 30
What does the action potential cause the calcium ions to do?
The calcium ion channels in the sarcoplasmic reticulum open
17 of 30
What does the opening of the calcium ion channels cause?
The calcium ions to diffuse into the sarcoplasm down a concentration gradient
18 of 30
What does the release of the calcium ions cause?
The ancillary proteins to be moved which allows the myosin bulbous heads to link with the actin binding sites
(actomyosin bridges)
19 of 30
Once the heads attach what happens?
They change their angle/rotate
20 of 30
What does the rotation of the myosin heads cause?
The pulling on the actin filaments over the adjacent myosin filaments
21 of 30
An ATP molecules attaches to each myosin head causing...?
Energy to be released from its hydrolysis enables the myosin head to detach from the stationary actin binding site and return to original position
22 of 30
Why would this cycle stop?
If the muscle fibre receives no nervous stimulation/if no calcium ions are present
23 of 30
What is the purpose of the calcium ions?
Enables the myosin heads to bind to binding sites on the actin
24 of 30
What happens to the sarcomere, H-zone,I-band and A-band during muscle contraction?
-Sarcomere shortens
- H-zone becomes shorter
- I-band becomes shorter
- A-band remains the same length
25 of 30
What is the power of muscle contraction due to?
Many parallel myofibrils lined side-by-side in a muscle fibre all contracting at the same time
26 of 30
What 2 things does the strength of muscle contraction depend on?
-How long the muscle is stimulated for
-How many muscle fibres are actually stimulated/contracting
27 of 30
What is the appearance/distribution/nervous control of skeleton muscle?
Appearance : Striated&multi-nucleated
Distribution:Attached to bone throughout body
Nervous control:Voluntary control
28 of 30
What is the appearance/distribution/nervous control of smooth muscle?
Appearance : Uninucleated cells&spindle shaped&Non-striated
Distribution:Lining the gut/blood vessels/Iris and ciliary body in eye
Nervous control:Involuntary/automatic control
29 of 30
What is the appearance/distribution/nervous control of cardiac muscle?
Appearance : Striated but branched with intercalated discs between cells
Distribution:Wall of heart
Nervous control:Myogenic&Involuntary control
30 of 30
Other cards in this set
Card 2
Front
Skeletal(voluntary)muscle is attached via... to the skeleton?
Comments
No comments have yet been made