Topic 6B: Muscles Flashcards
Other names for Skeletal Muscles
- Striated muscle
- Striped muscle
- Voluntary muscle
What are tendons?
Skeletal Muscles that are attached to bones
What are Ligaments?
- They attach bones to other bones
- hold them together
Skeletal Muscles are made up of…
Long Muscle Fibres
What are muscle fibres?
large bundles of long cells.
The cell membrane of the muscle fibre is called….
sacrolemma
When sacrolemma fold inwards and stick the sacroplasm, we call it….
Transverse (T) Tubules
What is the purpose of T Tubules?
Help into spread electrical impulses throughout the sacroplasm so they reach all parts of the muscle fibres
A network of internal membranes is called
sacroplasmic reticulum
What is the function of the sacroplasmic reticulum?
Stores and releases calcium ions that are need for contraction
What organelle is in muscle fibres?
lots of mitrochondria that release ATP for muscle contraction
Muscles are multinucleate. What does this mean?
Contain many nucleis
What are myofibrils?
- long cylindrical organelles
- they are made up of proteins and are highly specialised
Myofibrils contain….
- Thick myofilaments
- Thin myofilaments
- These move past each other to contract
If you put a myofibrils under a electron microscope what do you see?
- Dark bands
- Light bands
What do dark bands contain?
-Thick myofilaments
What do light bands contain?
-Thin myofilaments
What are A bands?
Thick myofilaments overlapped with thin myofilaments
What I bands?
Thin myofilaments only
A myofibrils are made up of short unit called?
sacromeres
The end of sacromeres are called?
Z-line
What is the middle of the sacromere called?
M-line
What is the H-zone?
Contains only myosin filaments
Do myofilaments contract?
No they slide over each other
Do sacromeres contract?
yes
What get shorter when the sarcomere contracts?
- I Bands
- H-Zone
What do myosin filaments have structurally?
- Globular heads that are hinged
- binding site for actin
- binding site for ATP
What do actin filaments have structurally?
- binding site for myosin heads
- actin-myosin binding sites
How are resting muscles maintained?
- actin-myosin binding site blocked by tropomyosin
- can’t slide past each other because of myosin heads cant bind on actin filaments
What are muscle contraction triggered by?
An influx of calcium ions
What happens when action potential reaches the muscle cells?
- depolarises sacrolemma
- depolarisation spreads down t-tubles to the sarcoplasmic reticulum
- sacroplasmic reticulum releases stores ca2+ into sacroplasm
Outline the process of muslce contraction
- ca2 binds to protein on tropomyosin
- changes shape and moves away exposing the actin myosin binding site
- allows myosin head to bend
- forms an actin myosin cross bridge
- enerygy released from ATP causes myosin heads to bind and pull actin filament along in a rowing motion
- Another ATP provides energy for myosin heads to dettach from the actin-myosin cross bridge
- reattaches to a new actin myosin binding site
- cycle repeats as long as calcium ions present
What is the role of Ca2+ in muscle contraction?
-Ca2+ binds to protein associated with tropomyosin which makes tropomyosin move away and expose the actin myosin binding site.
-Ca2+ activates the enzyme ATP hydrolase which hydrolyses ATP to provide the energy needed for muscle contraction
-
What is the role of ATP in muscle contraction?
- ATP releases energy which makes myosin bend which also pulls actin filaments along in a rowing motion
- Another ATP breaks the actin myosin cross bridge
How does muscle contractions stop?
- muscles stop being stimulated
- calcium ions leave the binding site
- by active transport
- back to sacroplasmic reticulum
- causes tropomyosin to move back and block the actin myosin binding site
- sacromeres lengthens again
Muscles will only contract if…
Myosin heads are attached to actin filaments
What provides the energy for muscle contraction?
ATP and Phosphocreatine (PCr)
How is ATP generated in aerobic respiration?
-via oxidative phosphorylation in cells mitrochondria
-
How is ATP generated in anaerobic respiration?
-rapidly by glycolysis
How is ATP generated in PCr?
- atp made by phosphorylating ADP
- which adds a phosphate group taken from PCr
- only used for short vigorous exercise
- anaerobic processes(no oxygen needed)
- its alactic (doesnt produce lactate)
Name the two types of muslce fibres?
slow twitch
fast twitch
What are the properties of slow twitch?
- contract slowly
- used for posture
- good for endurance activities eg long distance training
- can work for a long time without being tired
- energy released through aerobic respiration-use of o2
- lots of mitrochondria and blood vessels
- reddich colour-alot of myoglobin
What are the properties of fast twitch?
- contract very quickly
- used for fast movements
- good for short bursts of speed and power
- get tired very quickly
- energy released through anaerobic respiration use of glycogen
- Whitish colour because not much myoglobin
