What is the sarcolemma?

The sarcolemma is the cell surface membrane of a muscle fibre.

What is the sarcoplasm, and which organelle is unusually abundant within it?

The sarcoplasm is the cytoplasm of a muscle fibre, and it contains an unusually large number of mitochondria.

What is the sarcoplasmic reticulum, and what does it store?

The sarcoplasmic reticulum is a specialised endoplasmic reticulum forming a network of tubules around every myofibril, and it stores calcium ions.

What are transverse tubules, and what do they do?

Transverse tubules are inward folds of the sarcolemma that run deep into the fibre, and they carry the action potential to every myofibril so that the whole fibre is stimulated at the same instant.

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Human Musculoskeletal Anatomy: Skeletal Tissues

The structure of skeletal muscle

3 things to know
Component 3

Overview

Sarcoplasmic reticulum, transverse tubules and H zone of a sarcomere.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Why does a muscle fibre need so many mitochondria and such a dense capillary network?

Key term

How is a whole skeletal muscle organised down to the level of a single fibre?

Key term

Why is a skeletal muscle fibre described as multinucleate?

Questions from this subtopic

Each one with the model answer underneath.

1
How is a whole skeletal muscle organised down to the level of a single fibre?
Model answer
A muscle is made of bundles of muscle fibres wrapped in connective tissue, and each fibre is one very long cylindrical cell running the length of the bundle.
2
Why is a skeletal muscle fibre described as multinucleate?
Model answer
Each fibre is formed by the fusion of many separate cells during development, so the single fibre contains many nuclei, pushed to lie just beneath its surface membrane.
3
What is the sarcolemma?
Model answer
The sarcolemma is the cell surface membrane of a muscle fibre.
4
What is the sarcoplasm, and which organelle is unusually abundant within it?
Model answer
The sarcoplasm is the cytoplasm of a muscle fibre, and it contains an unusually large number of mitochondria.
5
What is the sarcoplasmic reticulum, and what does it store?
Model answer
The sarcoplasmic reticulum is a specialised endoplasmic reticulum forming a network of tubules around every myofibril, and it stores calcium ions.
6
What are transverse tubules, and what do they do?
Model answer
Transverse tubules are inward folds of the sarcolemma that run deep into the fibre, and they carry the action potential to every myofibril so that the whole fibre is stimulated at the same instant.

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