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Biology IB HL - 11.2 Movement Part 3

Biology20 CardsCreated about 1 month ago

This deck covers key concepts related to muscle structure and function, focusing on the organization and contraction of skeletal muscles.

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What can myofibrils be divided into?

The myofibrils can be divided into repeating sections called sarcomeres, each of which represent a single contractile unit
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Key Terms

Term
Definition
What can myofibrils be divided into?
The myofibrils can be divided into repeating sections called sarcomeres, each of which represent a single contractile unit
List the organisation of skeletal muscles?
skeletal muscle muscular bundle (fascicles) muscle fibres myofibrils sacromeres
What 5 specialised features does each individual muscle fibre have to facilitate muscle contraction?
They are Multinucleate They have a large number of Mitochondria They have a specialised Endoplasmic reticulum They contain tubular Myofibrils Sarcolem...
How are muscle cells multinucleate?
fibres form from the fusion of individual muscle cells and hence have many nuclei
How does having a large number of mitochondria aid in muscle contraction?
They have a large number of mitochondria (muscle contraction requires ATP hydrolysis)q
What is the specialised ER of muscles called and what is its role?
They have a specialised endoplasmic reticulum (it is called the sarcoplasmic reticulum and stores calcium ions)
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Biology IB HL - 11.2 Movement Part 3
TermDefinition
What can myofibrils be divided into?
The myofibrils can be divided into repeating sections called sarcomeres, each of which represent a single contractile unit
List the organisation of skeletal muscles?
skeletal muscle muscular bundle (fascicles) muscle fibres myofibrils sacromeres
What 5 specialised features does each individual muscle fibre have to facilitate muscle contraction?
They are Multinucleate They have a large number of Mitochondria They have a specialised Endoplasmic reticulum They contain tubular Myofibrils Sarcolemma MMEMS
How are muscle cells multinucleate?
fibres form from the fusion of individual muscle cells and hence have many nuclei
How does having a large number of mitochondria aid in muscle contraction?
They have a large number of mitochondria (muscle contraction requires ATP hydrolysis)q
What is the specialised ER of muscles called and what is its role?
They have a specialised endoplasmic reticulum (it is called the sarcoplasmic reticulum and stores calcium ions)
What are tubular myofibrils composed of?
They contain tubular myofibrils made up of two different myofilaments – thin filament (actin) and thick filament (myosin)
What is the sarcolemma? (structure)
The continuous membrane surrounding the muscle fibre is called the sarcolemma and contains invaginations called T tubules
What do myofibrils consist of?
Myofibrils consist of repeating contractile units called sarcomeres, which are made of two protein myofilaments
What is the "thick" filament and its structure?
The thick filament (myosin) contains small protruding heads which bind to regions of the thin filament (actin)
What causes the lengthening and shortening of the sarcomere?
Movement of these two filaments relative to one another causes the lengthening and shortening of the sarcomere
What is each individual sarcomere flanked by?
Each individual sarcomere is flanked by dense protein discs called Z lines, which hold the myofilaments in place
What is the role of the z discs?
The actin filaments radiate out from the Z discs and help to anchor the central myosin filaments in place
What causes skeletal muscle fibres to look striated?
The recurring sarcomeres produce a striated (striped) pattern along the length of the skeletal muscle fibres
What does the A band look like?
The centre of the sarcomere appears darker due to the overlap of both actin and myosin filaments (A band)
What does the I band look like?
The peripheries of the sarcomere appear lighter as only actin is present in this region (I band)
What does the H zone look like?
The dark A band may also contain a slightly lighter central region where only the myosin is present (H zone)
What 3 things are key to remember when drawing a diagram of the sarcomere?
The myosin filaments are the thick filaments and should be represented as being thicker than the actin filaments The myosin filaments should include protruding heads (myosin heads form cross-bridge attachments with actin) The striated banding pattern should be identified (A band = dark region ; I band = light region)
What are the 4 main steps of muscle contraction?
Depolarisation and calcium ion release Actin and myosin cross-bridge formation Sliding mechanism of actin and myosin filaments Sarcomere shortening (muscle contraction)
What is the first step of depolarization and calcium ion release?
An action potential from a motor neuron triggers the release of acetylcholine into the motor end plate