Flashcards in Muscles Deck (32):
What are the three types of muscle in the body?
Smooth muscle (aka involuntary muscle)
Describe the fiber appearance of; 1) skeletal, 2) cardiac, 3) smooth muscle.
2) specialised striated
Is the muscle voluntary/involuntary?
Describe the arrangement of;
1) Regularly arranged so contraction is in one direction
2) cells branch and interconnect resulting in simultaneous contraction
3) no regular arrangement- cells contract in different directions
What is the contraction speed like in;
1) rapid contraction
2) intermediate contraction
3) slow contraction
What is the length of contraction like in;
3) relatively long time
Describe the structure of skeletal muscle.
Fibres are tubular and multinucleated
Describe the structure of cardiac muscle.
Fibres are branched and uninucleated. Fainter striations than in skeletal muscle.
Describe the structure of smooth muscle.
Striped muscle. Fibres are spindle shaped and uninucleated.
What is the plasma membrane called that encloses the skeletal muscle?
What is the sarcoplasm?
The shared cytoplasm within a muscle fibre.
What are T tubules?
Parts of the sarcolemma that are folded inwards to help spread electrical impulses through the sarcoplasm.
Why are T tubules important?
They ensure the whole fibre receives the impulse to contract at the same time.
What organelle is highly abundant in muscle fibres?
What is the modified version of endoplasmic reticulum in the muscle fibres?
What are myofibrils and where are they found?
They are long cylindrical organelles made of protein. Found in the muscle fibres.
What two types of protein filaments that make up myofibrils?
Actin and Myosin
Describe the structure of actin.
Thinner filament. It consists of two strands twisted around each other.
Describe the structure of myosin.
Thicker filament. It consists of long rod-shaped fibres with bulbous heads that project to one side.
What are the light bands of myofibrils?
What are they also known as?
Region where the actin and myosin filaments do not overlap. AKA isotopic bands/I-bands.
What are the dark bands of myofibrils?
What are they also known as?
Region where thick myosin filaments are present.
AKA anisotropic bands/A-bands.
What is the Z-line of myofibrils?
Line found at the centre of each light band.
What is the H-zone?
Lighter coloured region found in the centre of each dark band.
What is a sarcomere?
The distance between adjacent Z-lines.
When a muscle contracts what happens to the sarcomere and the H zone?
Sarcomere shortens and H zone decreases in size.
Where are slow-twitch fibres found in the body?
In the muscles that maintain posture in the body, so those muscles in the back and calves.
Name some properties of slow-twitch fibres.
Less powerful contractions
Used in endurance activities as they don't tire easily
Get energy aerobically
Rich in myoglobin (red coloured muscles)
Rich in mitochondria and blood vessels.
Where are fast-twitch fibres found in the body?
In areas that require short bursts of intense activity like the eyes or biceps.
Name some properties of fast-twitch fibres.
Short bursts of power as they tire easily
Get energy anaerobically
Low levels of myoglobin and blood vessels (pale colour)
Contain thicker myosin
Store creatine phosphate.
Explain step by step the process of muscle contraction, talking about the interaction between actin and myosin, along with where the energy supply comes from.
Start from the impulse in the presynaptic neurone and finish on one contraction of the muscle fibre.
1) Action potential travels down presynaptic neurone
2) Calcium ion channels are triggered to open
3) Calcium ions diffuse into synaptic knob where they trigger vesicles containing acetylcholine to fuse with the presynaptic membrane.
4) Acetylcholine diffuses into synaptic cleft by exocytosis and binds to receptors on the sarcolemma.
5) Sodium ion channels open and membrane is depolarised.
6) Acetylcholine is broken down into by acetylcholinesterase.
7) Depolarisation travels deep into T tubules. Sarcoplasmic reticulum is triggered to open Ca2+ ions.
8) Calcium ions travel down concentration gradient.
9) Ca2+ ions bind to troponin which causes it to change shape. This pulls on tropomyosin which reveals the actin-myosin binding site.
10) Myosin head attaches to binding site
11) Myosin head changes angle, pulling actin filament with it. ADP released.
12) ATP binds to head, causing it to detach frm the actin filament.
13) ATP is hydrolysed to ADP by myosin provides the energy for myosin to resume to its original position.
14) Head of myosin reattaches to a binding site further along the actin filament and the cycle repeats.
How is energy supplied to the muscles in limited oxygen availability and when does this mainly occur?
Energy is supplied anaerobically and ATP is made along with the pyruvate molecule being converted into lactic acid. This occurs usually when sprinting or doing high-intense, short bursts of exercise.