MSK S2 Flashcards
What is the function of agonists?
The main muscles responsible for a particular movement
What are the muscle groups?
Agonists
Antagonists
Synergists
Fixators
What is the function of antagonists?
Oppose agonists
What is the function of synergists?
Assist agonists (neutralise extra movement)
What is the function of fixators
Stabilises action of agonist (eg by fixing non moving joint whilst agonist acts over two joints)
What are the types of muscle contraction?
Isotonic contraction
Isometric contraction
What are the types of isotonic contraction?
Concentric
Eccentric
Define isotonic contraction
Constant tension but variable length - the muscle changes length and moves the load
Define isometric contraction and give an example
Constant length but variable tension eg hand grip
Describe concentric contraction and give an example
Muscle shortens eg lifting a load with the arm
Describe eccentric contraction and give an example
The muscle exerts a force whilst being extended eg walking down a hill.
This type of muscle action can cause delayed onset muscle soreness
What are the muscle fibre types?
I Slow twitch
IIa Fast twitch
IIb Fast twitch
What is spatial summation in relation to muscle?
The more neurones which stimulate the muscle, the more fibres will be activated so the greater the overall force of the contraction.
What is temporal summation in relation to muscle?
The more action potentials that arrive at a muscle per second, the greater the force of the contraction.
What is tetanic contraction?
When the muscle is at it’s maximal contraction.
In the disease tetanus, this is caused by the toxin secreted by Clostridium tetani.
What is an EMG?
An electromyography
Electrodes may be placed above or in muscles to measure activity
Can be used to diagnose eg MND (motor neurone disease)
What is a marker for muscle damage?
Serum creatine kinase
Define ‘contracture’
A state of constant contraction caused by ATP depletion
Myosin heads are unable to detach from actin filaments
Seen in rigor mortis
What components make up the axilla?
Axillary artery Axillary vein Lymphatic vessels Axillary lymph nodes Axillary fat Brachial plexus
How are the sections of the Axillary artery and Axillary vein numbered?
In the direction of blood flow, ie in the artery, the 1st part is closest to the heart and the 3rd is furthest.
Describe the first part of the Axillary artery
In the Axillary sheath
Has one branch - the superior thoracic artery
Describe the second part of the Axillary artery
Posterior to pectoralis minor
Two branches: lateral thoracic artery and thoracocromial artery
Describe the third part of the Axillary artery
Runs from pectoralis minor to teres major
Three branches: subscapular artery, and posterior and anterior circumflex humeral arteries
Describe the Axillary vein
On the anteromedial side of the Axillary artery
Formed by the union of the brachial and basilic veins at the inferior border of teres major
Very variable between individuals
Is a collateral route of venous return in case of vena cava obstruction
From which vertebrae do the roots of the brachial plexus originate?
C5, C6, C7, C8, T1
What are the parts of the brachial plexus?
Roots Trunk Divisions Cords Branches
What nerves branch off the roots of the brachial plexus and where do they originate?
The C5, C6 & C7 roots all have a branch which goes on to form the long thoracic nerve
The C5 root also branches to form the dorsal scapular nerve and to contribute to the phrenic nerve
How do the roots of the brachial plexus form trunks?
The C5 and C6 roots merge to form the superior trunk
The C7 root forms the middle trunk
The C8 and T1 roots merge to form the inferior trunk
What nerves branch off the superior trunk of the brachial plexus?
Suprascapular nerve and the nerve to the subclavius
How do the trunks of the brachial plexus divide?
The superior, middle and inferior trunks all branch into posterior and anterior.
The anterior branches of the superior and middle trunks join to form the lateral cord
The posterior branches of the superior, middle and inferior trunks join to form the posterior cord
The anterior branch of the inferior trunk becomes the medial cord
How is the lateral cord formed?
The anterior branches of the superior and middle trunks join to form the lateral cord
What nerve(s) originate(s) from the lateral cord?
The lateral pectoral nerve
How is the posterior cord formed?
The posterior branches of the superior, middle and inferior trunks join to form the posterior cord
What nerve(s) originate(s) from the posterior cord?
AXILLARY NERVE
Thoracodorsal nerve
Inferior subscapular nerve
Superior subscapular nerve
How is the medial cord of the brachial plexus formed?
The anterior branch of the inferior trunk becomes the medial cord
What nerve(s) originate(s) from the medial cord?
Medial pectoral nerve
Medial cutaneous nerve of arm
Medial cutaneous nerve of forearm
How do the cords of the brachial plexus become the terminal nerves?
The lateral and medial cords split.
A branch of each join together to form the median nerve
The other branch of the lateral cord forms the musculocutaneous nerve
The other branch of the medial cord forms the ulnar nerve
The posterior cord becomes the radial nerve
