Session 4 Flashcards
What are parallel muscles and what are the three different types?
Fibres run parallel to force generating axis.
Strap - eg sartorius
Fusiform - wider and cylindrical shaped in the centre, taper off at ends. Eg biceps brachii.
Fan shaped - fibres converge at one end, eg pectoralis major
What are circular muscles?
Where fibres form a concentric ring around a sphincter. Tend not to attach to bones. Eg orbicularis oculi around the eye
Define: agonist, antagonist, synergist, neutraliser and fixator.
Agonist - the prime muscle(s) responsible for a particular movement.
Antagonist - oppose prime movers. Important for the fine control of the movement.
Synergist - assist prime movers. Acting alone they cannot perform the movement of the agonist.
Neutralisers - prevent unwanted actions that the agonist can perform. Eg the rotator cuff muscles prevent flexion of the elbow whilst the bicep flexes the elbow.
Fixators - hold a joint stable whilst another one is moving
What is isotonic contraction and what are the two different types?
Where the tension within the muscle remains constant and the length changes.
Concentric contraction - where the muscle shortens
Eccentric contraction - where the muscle lengthens. Can result in delayed onset muscle pain.
What is the contraction called when the muscle is generating tension but not shortening?
Isometric contraction
What is a motor unit?
An Alpha-motor neurone and the group of individual muscle fibres it innervates
What is the advantage of big or small motor units?
Muscles that perform precise fine movements have a low number of muscle fibres per motor unit. Powerful muscles have a high number.
What form of myosin heavy chain do the different types of muscle fibres possess?
Slow/type I muscle fibres - type I myosin heavy chain (slow oxidative)
Fast/type II muscle fibres - type IIA (fast oxidative). Type IIX (fast glycolytic).
What factors does the contractile force produced by a muscle depend on?
The size principle - small motor neurones are recruited before large ones, generally meaning that slow fibres are recruited first.
The rate code - the frequency that the muscle fibres are stimulated by their motor neurone. Consecutive APs in a repetitive train result in summation, giving a slightly larger force with each contraction. Eventually a limit, called tetany, is reached.
What causes baseline muscle tone?
Motor neurone activity
Muscle elasticity
What is hypotonia and what can cause it?
A lack of skeletal muscle tone. Caused by damage to the motor cortex/cerebellum/spinal cord or myopathy.
What are pennate muscles and what are the three different types?
They have one or more aponeurosis running through the muscle body. The fascicles attach to the aponeurosis at an angle (pennation angle).
Unipennate - all fascicles on the same side of the tendon eg extensor digitorum longus of foot
Bipennate - fascicles on both sides of central tendon eg rectus femoris
Multipennate - central tendon branches eg deltoid
What are the articulating surfaces of the elbow joint?
Trochlear notch of the ulna with the trochlea of the humerus.
Head of the radius with the capitulum of the humerus.
Outline the stability of the elbow joint
Weak anteriorly and Posteriorly. Joint capsule strengthened medially and laterally by collateral ligaments.
What is malignant hypothermia and how is it treated?
A rare life-threatening condition triggered by some volatile anaesthetic agents and succinylcholine, a neuromuscular blocking agent. Leads to uncontrolled increase in oxidative metabolism, hence body temperature.
Polymorphism in the ryanodine receptor is the most common cause. The receptor become activated and leads to a massive increase in intercellular Ca2+ from stores. The SERCA pump works at an increased rate, consuming ATP.
Dantrolene is administered which antagonised the ryanodine receptors.
Outline the ligaments of the elbow joint
Radial collateral ligament - fan like, joins lateral epicondyle to annular ligament.
Ulnar collateral ligament - joins medial epicondyle to coronoid process and olecranon of ulna. Three bands - anterior (strongest), posterior and oblique (depends the socket for trochlea).
Annular ligament - encircles and holds the radial head in the radial notch, permitting pronation and supination.
What are the bursae in the elbow prone to bursitis?
Subtendinous olecranon bursa
Subcutaneous olecranon bursa (more common) - can also become infected from a wound to the elbow
What is the neurovascular supply to the elbow joint?
Arterial anastomoses around the elbow joint.
Musculocutaneous, ulnar and radial nerves.
How does an elbow dislocation most commonly occur and present?
Posterior dislocation (radius and ulna posterior) usually occurs when a child falls on their hands with their elbow flexed. The distal end of the humerus is driven through the weak anterior part of the joint capsule. The ulnar collateral ligament is often torn. Injury to the ulnar nerve, median nerve and brachial artery may result.
What are the two types of epicondylitis and how do they occur?
Lateral epicondylitis (tennis elbow) - repetitive use of extensor muscles Medial epicondylitis(golfers elbow) - repetitive use of flexor muscles
How can a medial epicondyle Avulsion occur?
A fall that causes severe abduction of the extended elbow.
What are the articulations of the proximal and distal radioulnar joints?
Proximal - radial head and radial notch of ulna
Distal - ulnar notch of the radius and head of the ulna
What ligaments are present in the distal radioulnar joint?
Anterior and posterior radioulnar ligaments.
A fibrocartilage articular disc that binds the two bones together during movement and separates the joint from the wrist joint.
What is the neurovascular supply of the distal radioulnar joint?
Posterior and anterior interosseous artery and nerve.
What are the functions of the interosseous membrane?
Holds the radius and ulna together during pronation and supination. Acts as a site of attachment for muscles in the forearm. Transfers forces from the radius to the ulna.
Define dislocation and subluxation
Dislocation is the complete loss of contact of joint surfaces
Subluxation is the partial dislocation of a joint so the bones are misaligned, but still in contact.
How can subluxation of the head of the radius occur?
When a child is lifted by the upper limb when the forearm is pronated.
What is the name given to the extensions of the synovial membranes that cover the proximal and distal radioulnar joints?
Sacciform recess
What are the articular surfaces of the wrist joint?
Proximally - the distal end of the radius and the articular disc
Distally - the scaphoid, lunate and triquetrium
Describe the neurovascular supply to the wrist joint.
The dorsal and palmar carpal arches derived from the ulnar and radial arteries.
Anterior interosseous branch of the median nerve, posterior interosseous branch of the radial nerve and deep and dorsal branches of the ulnar nerve.
Outline the ligaments of the wrist joint.
Palmar radiocarpal ligaments - joins radius to both rows of carpals. Ensures hand follows forearm during supination.
Dorsal radiocarpal ligaments - joins radius to both rows of carpals. Ensures hand follows forearm during pronation.
Ulnar collateral ligament - joins ulnar styloid process to triquetrum and pisiform. Strengthens the joint capsule medially.
Radial collateral ligament - joins radial styloid process to scaphoid. Strengthens the joint capsule laterally.
What happens to the brachial artery as it exits the cubital fossa?
It divides into the radial and ulnar artery. The ulnar artery travels deep to the flexor digitorum superficialis and passes superficially to flexor retinaculum to enter hand. The radial artery travels deep to the brachioradialis and crosses the floor of the anatomical snuffbox.
What happens to the brachial artery as it exits the cubital fossa?
It divides into the radial and ulnar artery. The ulnar artery travels deep to the flexor digitorum superficialis and passes superficially to flexor retinaculum to enter hand. The radial artery travels deep to the brachioradialis and crosses the floor of the anatomical snuffbox.
Outline the borders of the anatomical snuffbox
Medial - tendon of the extensor pollicis longus
Lateral - tendons of the extensor pollicis brevis and abductor pollicis longus
Proximal - styloid process of the radius
Floor - scaphoid and trapezium
Roof - skin
Outline the contents of the anatomical snuffbox
Radial artery, cephalic vein and the superficial branch of the radial nerve
