Skeletal Muscles Flashcards
What are skeletal muscles?
Muscles that are attached to the skeleton
What do skeletal muscles do?
Bring about movement of parts of the body
How do skeletal muscles perform their function?
Through contraction and relaxation
What are the characteristics of skeletal muscles?
Attached to the skeleton by inelastic tendons
They are striated
They are under voluntary control
What is the structure of a skeletal muscle?
Made up of bundles of muscle fibres
They are bound together by connective tissue known as the perimysium
These bundles are enclosed by the epimysium
What is a muscle fibre like?
A single elongated, cylindrical cell
Consists of thousands of myofibrils
What are myofibrils like?
They contain two types of protein filaments
What protein filaments do myofibrils contain?
Myosin
Actin
What are myosin filaments like?
Thicker and darker
What are actin filaments like?
They are thinner and lighter
How are actin and myosin positioned in a myofibril?
They overlap in certain areas
Which filaments form the dark bands in myofibrils?
They regions where active and myosin overlap
Which filaments form light bands in myofibrils?
The sections with only actin
What is the Z-line?
A line which bisects the dark bands on a myofibril
What is a sarcomere?
The region between two Z-lines
It is the functional unit of a muscle
What causes the contraction and relaxation of muscles?
Nerve impulses
What happens during contraction of muscles?
The thin actin filaments slide past the thicker myosin filaments
The Z-lines then move closer together
The sacromere is shortened, which shortens the myofibrils, which shortens the muscle fibre, which shortens the whole muscle
How are skeletal muscles often arranged?
In pairs
Why are skeletal muscles arranged in pairs?
So that the one contracts as the other relaxes
What are antagonistic muscles?
Muscles which work in opposite directions, pulling on the same bone
Why are antagonistic muscles important?
They make coordinated movements possible
Give an example of antagonistic muscles
Biceps and triceps
Where are the biceps situated?
To the front of the upper arm
Why are the biceps called biceps?
The muscle is attached to the pectoral girdle with two tendons
What other bone is the bicep attached to?
Radius
Where do the triceps occur?
At the back of the upper arm
Why are the triceps called the triceps?
They are attached to the pectoral girdle with three tendons
What other bone is the tricep attached to?
The ulna
What happens when the biceps contract and the triceps relax?
The elbow joint bends and the forearm is raised
What happens when the triceps contract and the biceps relax?
The elbow joint extends and the forearm is lowered
What is an agonist?
The muscle which contracts
What is an antagonist?
The muscle which relaxes
What is a flexor?
A muscle which serves to bend a part of the body
What is an extensor?
A muscle which serves to extend or straighten a part of the body
