Section 3 Muscles

Muscles

Muscles are an important part of the complex system that allows to to move and function. We will consider individual muscles in depth as we go through the module. The video is an excellent crash course in the underlying mechanisms and ways muscles work. Have a watch of it with a nice cup of tea and make some notes regarding the keys themes below:

What do muscles do when they contract?

What do the muscles do on the opposite the prime movers?

What is a motor unit?

What are the names of the attachments of muscles to bone called?

What happens when a muscle is damaged?

The different types of skeletal muscle are as follows:

Fusiform
Parallel
Convergent
Unipennate
Bipennate
Multipennate
Circular

Can you think of any specific muscles which fit the above?

Muscles, level 4 example.

Myology

In MSK we expected you to know individual muscles and the groups of muscles they belong to. For each muscle at level 4, we would want the following in priority order (remember however you don't routinely stretch all muscles!) Here is an example:

Biceps Femoris

Crosses and acts over the hip joint (posteriorly) and knee joint (posteriorly)
Extends the hip and flexes the knee (position and palpate the muscle belly)
Is stretched by flexing the hip and extending the knee
An example of when it is used functionally e.g. eccentrically to decelerate the leg in the terminal swing phase of running.
Finally and ONLY if you know the above, do origins and insertions. 1-4 is needed to pass.
1. Origin = Ischial tuberosity and Gluteal tuberosity
2. Insertion = Head of fibula

Key Muscles

The shoulder muscles

Trapezius (Upper, Middle, Lower)

Rhomboids (Major and Minor)

Serratus anterior

Levator scapulae

Sternocleidomastoid

Latissimus dorsi

Pectoralis major / minor

Deltoid

Supraspinatus

Infraspinatus

Teres minor

Subscapularis

The Hip muscles

Iliopsoas (anterior)

Rectus Femoris (anterior)

Adductor longus

Adductor magnus

Gluteus maximus (posterior)

Gluteus medius (lateral)

Gluteus minimus (lateral)

Tensor fascia lata and iliotibial tract (lateral)

The elbow muscles

Triceps (posterior)

Biceps brachii (anterior)

Extensor carpi radialis Brevis / Longus (anterio-lateral)

Extensor digitorum (anterio-lateral)

Extensor carpi ulnaris (anterio-lateral)

Supinator (anterio-lateral)

Pronator teres (anterio-medial)

Flexor carpi radialis (anterio-medial)

Flexor digitorum profundus / superficialis (anterio-medial)

Flexor carpi ulnaris (anterio-medial)

The knee muscles

Hamstrings

Biceps femoris
Semitendinosus
Semimembranosus

Quadriceps

Rectus femoris
Vastus lateralis
Vastus medialis
Vastus Intermedialis

Popliteus

The wrist & hand muscles

Extensor carpi radialis Brevis / Longus

Extensor digitorum

Extensor carpi ulnaris

Flexor carpi radialis

Flexor digitorum profundus / superficialis

Flexor carpi ulnaris

The foot & ankle muscles

Tibialis anterior

Extensor digitorum longus

Extensor hallucis longus

Peroneus longus

Peroneus brevis (Lat)

Gastrocnemius (post

Soleus (post)

Tibialis posterior (Med)

Flexor digitorum longus (Med)

Flexor hallucis longus (Med)

Extensor digitorum brevis

Extensor hallucis longus

learn to stretch the following muscles

Iliopsoas (eg. flexes the hip, so in order to lengthen the muscle we must do the opposite)

Hamstrings

Rectus Femoris

Pectoralis major / minor

Supraspinatus

Infraspinatus

Subscapularis

Triceps

Biceps brachii

Wrist Extensors

Wrist Flexors

Gastrocnemius

Soleus

Origins & Insertions

Muscles have an origin and an insertion attachment site.

Muscles will pull towards the origin

Origin = less mobile

Insertion = more mobile

Agonist & Antagonist

In an antagonistic muscle pair as one muscle contracts the other muscle relaxes or lengthens.

The muscle that is contracting is called the agonist and the muscle that is relaxing or lengthening is called the antagonist

SYNERGISTS – work with an agonist to provide a suitable base for movement, or to facilitate the movement, without directly producing the movement. They may modify the angle of pull of an agonist.

FIXATORS – fix bones of origins in order to make the pull more efficient.

Muscle Range

INNER – The part at which the muscle is near its shortest position

MIDDLE – The part that the muscle is in between fully lengthened and fully shortened

OUTER –The part where the muscle is almost fully lengthened.

Muscle contractions

Isotonic contraction

Occur when a muscle contracts and changes length. There are two types of Isotonic contractions:

- Concentric – Involves the muscle shortening. The origin and insertion of the muscle move closer together and the muscle becomes bigger.

- Eccentric – = Involves the muscle lengthening whilst it is under tension. The origin and the insertion move further away from each other. An eccentric contraction provides the control of a movement on the downward phase and it works to resist the force of gravity.

Isometric Contraction

Occur when a muscle is placed under tension requiring contraction, but the length remains the same. The origin and insertion stay the same distance apart.

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