Phase 2 - Week 2 (Tendons, Shoulder), Phase 1 - Week 6 (Muscles, Muscle/Nerve Excitation), Phase 2 - Week 3 (Muscle, Elbow + Forearm, Nervous Control) Flashcards Preview

Medicine YEAR 1 > Phase 2 - Week 2 (Tendons, Shoulder), Phase 1 - Week 6 (Muscles, Muscle/Nerve Excitation), Phase 2 - Week 3 (Muscle, Elbow + Forearm, Nervous Control) > Flashcards

Flashcards in Phase 2 - Week 2 (Tendons, Shoulder), Phase 1 - Week 6 (Muscles, Muscle/Nerve Excitation), Phase 2 - Week 3 (Muscle, Elbow + Forearm, Nervous Control) Deck (291):

List the bones of the shoulder

1. Scapula
2. Clavicle
3. Humerus


Describe the position of the scapula

Lies obliquely on the back/side of the thorax


What type of bone is the scapula



Describe the articulations made by the scapula

1. Acromioclavicular joint - acromial end of of the clavicle and acromion of the scapula
2. Glenohumeral joint - glenoid fossa of the scapula and head of the humerus


List the distinct structural features of the scapula

1. Acromion
2. Coracoid process
3. Glenoid fossa
4. Inferior angle
5. Infraspinous fossa
6. Lateral Border
7. Medial Border
8. Neck of the glenoid
9. Spine
10. Superior border
11. Subscapular fossa
12. Supraspinous fossa
13. Suprascapular notch



Large projection forming point of the shoulder, articulates with the clavicle


Coracoid Process

Large anterior projection, provides insertion point for pectoralis minor and point of origin for short head of the biceps brachii and corcacobrachialis


Glenoid Fossa

Shallow socket that articulates with the head of the humerus to form the shoulder joint


Inferior angle

Junction between the medial and lateral borders, typically overlies 7th rib


Infraspinous fossa

Large depression on the back of the scapula, below the spine, provides point of origin for the infraspinatus


Lateral border

Thick border, runs from infraglenoid tubercle to inferior angle


Medial border

Thin border between superior and inferior angles


Neck of the glenoid

Constriction between glenoid + body of the scapula


Spine of the scapula

Triangular ridge of bone that crosses the back of the scapula , from acromion to medial border


Superior Angle

Junction between lateral + medial borders


Superior Border

Thin, sharp border, separated from coracoid process by supraglenoid notch


Subscapular fossa

Slightly ridged fossa on inner surface of the scapula. Point of origin for subscapularis muscle


Supraspinous fossa

Deep fossa on back of scapula, above spine. Point of origin for supraspinatus muscle


Subscapular notch

Dip in superior border, just medial to coracoid process


Describe the shape and postition of the clavicle

Slightly S-shaped bone, lies at the base of the neck, in front of the first rib


Describe the articulations made by the clavicle

1. Acromioclavicular joint with the acromion of the scapula
2. Sternoclavicular joint with the manubrium of the sternum


Describe the ends of the clavicle

1. Sternal end = medial end of clavicle, articulates with the manubrium of the sternum
2. Acromial end = lateral end of the clavicle, articulates with the acromion of the scapula


Conoid tubercle of the clavicle

Small projection from posterior edge, gives attachment to the conoid part of the coracoclavicular ligament


Describe the articulations made by the humerus

1. Glenohumeral joint - head of the humerus with the glenoid fossa of the scapula
2. Humeroulnar joint - trochlea of the humerus with the trochlear notch of the ulna
3. Humeroradial joint - capitulum of the humerus with the head of the radius


List the distinct structural features of the humerus

1. Head
2. Anatomical neck
3. Greater tubercle
4. Lesser tubercle
5. Surgical neck
6. Intertubercular groove
7. Shaft
8. Deltoid tuberosity
9. Capitulum
10. Trochlea
11. Coronoid fossa
12. Radial fossa
13. Olecranon fossa
14. Medial epicondyle
15. Lateral epicondyle


Head of the humerus

Forms 1/3 of a sphere that articulates with the glenoid fossa of the scapula


Anatomical neck of the humerus

Constricted area that joins head to greater and lesser tubercles


Greater tubercle

Large projection from the lateral side of the proximal humerus


Lesser tubercle

Projection that provides an insertion point for the subscapularis muscle


Surgical neck

Junction between the tubercles and the shaft. Common site for fractures


Intertubercular groove

Located anteriorly between the tubercles, holds the tendon of the biceps brachii muscle. Sometimes called bicipital groove.


Shaft of the humerus

Long + thick shaft that connects the two extremities


Deltoid tuberosity

Roughened area, halfway down shaft. For the insertion of the deltoid muscle



Lateral of the two distal condyles, articulates with the radius



Medial of the two distal condyles, articulates with the ulna


Coronoid fossa

Anterior fossa above the capitulum for the head of the radius


Radial fossa

Anterior fossa above the capitulum for the head of the radius


Olecranon fossa

Large posterior fossa for the olecranon of the ulna


Medial epicondyle

Prominence medial to the trochlea, gives origin to the superficial flexor muscles in the forearm


Lateral epicondyle

Prominence located lateral to the capitulum gives origin to the extensor muscle in the forearm


List the muscles acting on the scapula

1. Pectoralis minor
2. Rhomboid major
3. Rhomboid minor
4. Trapezius
5. Serratus anterior


Give the origin, insertion and action of pectoralis minor

Origin = Ribs 3-5
Insertion = Coracoid process of the scapula
Action = Pulls shoulder girdle forwards + downwards


Give the origin, insertion and action of rhomboid major

Origin = T2-T5 spinous processes
Insertion = Medial border of the scapula
Action = Medially rotates + retracts the scapula


Give the origin, insertion and action of rhomboid minor

Origin = C7-T1 spinous processes
Insertion = Spine of the scapula
Action = Medially rotates the scapula and retracts the scapula


Give the origin, insertion and action of the trapezius

Origin = External protuberance of the occipital bone, nuchal ligament, C7-T2
Insertion = Clavicle, scapula
Action = Elevates + retracts the scapula and depresses its medial aspect, extends and laterally flexes the head and neck


Give the origin, insertion and action of serratus anterior

Origin = Ribs 1-9
Insertion = Costal surface of the medial border of the scapula
Action = Protracts the scapula and pectoral girdle


List the shoulder muscles acting on the humerus

1. Latissimus dorsi
2. Pectoralis major


Give the origin, insertion and action of latissimus dorsi

Origin = T7-T12 spinous processes, iliac crest of hip bone, ribs 9-12
Insertion = Intertubercular groove of the humerus
Action = Extends, adducts and medially rotates the arm at the shoulder joint


Give the origin, insertion and action of pectoralis major

Origin = Medial end of the clavicle, sternum, costal cartilages 1-6
Insertion = Intertubercular groove of the humerus
Action = Adducts and internally rotates the humerus, extends shoulder joint from flexed + flexes it from extended


List the rotator cuff muscles

1. Supraspinatus
2. Infraspinatus
3. Subscapularis
4. Teres minor


Give the origin, insertion and action of the supraspinatus

Origin = Supraspinous fossa of the scapula
Insertion = Greater tubercle of the humerus
Action = Initiates abduction of the arm


Give the origin, insertion and action of the infraspinatus

Origin = Infraspinous fossa of the scapula
Insertion = Greater tubercle of the humerus
Action = Laterally rotates the arm


Give the origin, insertion and action of the subscapularis

Origin = Subscapular fossa of the scapula
Insertion = Lesser tubercle of the humerus
Action = Medially rotates the arm


Give the origin, insertion and action of teres minor

Origin = Lateral border of the scapula
Insertion = Greater tubercle of the humerus
Action = Laterally rotates the arm, contributes to abduction of the arm


Give the origin, insertion and action of the deltoid

Origin = Clavicle, spine of the scapula, acromion of the scapula
Insertion = Deltoid tubersity of the humerus
Action = Adbucts the shoulder


Give the origin, insertion and action of the teres major

Origin = Inferior angle of the scapula
Insertion = Intertrabecular Groove of the humerus
Action = Extends the shoulder, adducts and medially rotates the humerus


Give the origin, insertion and action of the coracobrachialis

Origin = Coracoid process of the scapula
Insertion = Humerus
Action = Flexes the shoulder and adducts the arm


How are the upper limbs innervated

The brachial plexus supplies the entire upper limb with motor and sensory innervation


Describe the structure of the brachial plexus

1. Roots - C5-T1 spinal nerves
2. Trunks - superior, middle and inferior
3. Divisions - anterior and posterior
4. Cord - posterior, lateral and medial
5. Branches


Superior trunk of the brachial plexus

- Formed from roots of C5 + C6
- Splits into anterior and posterior divisons


Middle trunk of the brachial plexus

- Formed from root of C7
- Splits into anterior and posterior divisions


Inferior trunk of the brachial plexus

- Formed from the roots of C8 + T1
- Splits into anterior + posterior divisons


Anterior divisions of the brachial plexus

The upper and middle anterior divisions form the lateral cord and the lower anterior division forms the medial cord


Posterior divisions of the brachial plexus

The posterior divisions of all three trunks combine to form the posterior cord


Posterior cord of the brachial plexus

- Formed by the posterior divisions of all three trunks
- Gives off branches:
1. Subscapular nerves
2. Thoracodorsal Nerve
3. Axillary nerve
4. Continues as radial nerve


Lateral Cord of the brachial plexus

- Formed by the anterior division of the inferior trunk
- Gives of branches:
1. Musculocutaneous nerve
2. Lateral pectoral nerve
3. Joins with the medial cord to form the median nerve


Medial cord of the brachial plexus

- Formed by the anterior divisions of the superior and middle trunks
- Gives off branches:
1. Medial pectoral nerve
2. Medial cutaneous nerve of the forearm
3. Medial cutaneous nerve of the arm
4. Ulnar nerve
5. Joins with the lateral cord to form the median nerve


List the terminal branches of the brachial plexus

1. Axillary nerve
2. Radial nerve
3. Musculocutaneous nerve
4. Ulnar nerve
5. Median nerve


Axillary nerve

Origin = C5/6, posterior cord
Course = descends behind the axillary artery + winds around the surgical neck of the humerus
Innervates = motor = deltoid + teres minor, sensory = shoulder joint, cutaneous = skin over the shoulder + lateral arm


Radial nerve

Origin = C5-T1 posterior cord of the brachial plexus
Course = exits axillae under teres minor, runs around back of humerus in the radial groove with the arteria profunda brachii. Passes down the lateral side of the forearm to the wrist
Innervates = motor = extensors of elbow, wrist + hand, sensory = elbow, wrist + hand joints, cutaneous = skin over the posterior surface of the upper limb


Musculocutaneous nerve

Origin = C5-7, lateral cord
Course = descends between biceps + brachialis to the elbow where it becomes the lateral cutaneous nerve of the forearm
Innervates = motor = flexors of the elbow joint, cutaneous = skin over the lateral border of the forearm


Ulnar nerve

Origin = C7-T1, medial cord
Course = descends the medial side of the arm in front of the medial head of triceps to reach the elbow. Enters the flexor compartment of the forearm + travels to the wrist
Innervates = motor = majority of the muscles of the hand, sensory = hand joints, cutaneous = skin of the medial aspect of the hand


Median nerve

Origin = C5-T1, medial + lateral cords
Course = leaves axillae with brachial artery, travels to the elbow. In the forearm, it travels to the wrist where it enters the carpal tunnel and divides into medial and lateral branches
- Innervates = motor = most of the flexor muscles in the forearm, cutaneous = skin of the elbow, wrist and radial aspect of the palm of the hand


List the 3 major arteries in the posterior scapular region

1. Suprascapular artery
2. Posterior circumflex artery
3. Circumflex scapular artery


Describe the function of tendons

Tough, fibrous structures that provide attachment for muscles to bones. Transmit the muscles' contractile force to bone, producing movement at joints.


Describe the arrangement of fibres in tendons

Collgen fibril --> Collagen fibre --> Primary collagen fibre bundle (sub-fascicle) --> Secondary fibre bundle (fascicle) --> Tertiary fibre bundle --> Tendon


Describe the connective tissue layers that surround tendons

Endotenineum = Surrounds primary, secondary and tertiary bundles to facilitate gliding
Epiteon = fine layer of connective tissue that sheathes tendon
Paratenon = loose elastice connective tissue layer, allows tendon to more against neighbouring tissues


How are tendons attached to bones?

By collagenous fibres (Sharpey fibres) that continue into the matrix of the bone


What type of collagen is found in tendons?

Type 1


List the cell types found in tendons

1. Tenocytes (fibrocytes)
2. Tenoblasts (fibroblasts)


Explain the role of tenocytes in tendons

Mature tendon cells - lay down type 1 collagen fibres.


Explain the role of tenoblasts in tendons

Immature tendon cells, give rise to tendons. Highly proliferative, involved in synthesis of collagen and other components of the ECM.


What aspect of tendon structure gives their tensile strength?

Collagen bundles in parallel arrangements gives tensile strength and elasticity in one direction.


Describe the components of the ECM of tendons

Elastin, proteoglycans, type 1 collagen


List the stages of tendon healing

1. Inflammation
2. Regeneration
3. Remodelling


How long does each stage of tendon healing last?

Inflammation lasts a week, regeneration lasts a month, remodelling lasts a year


Describe the pain felt during each stage of tendon healing

Pain occurs during:
- Inflammation even when at rest
- Regeneration under normal load bearing
- Remodelling with extreme load bearing


Describe the inflammation stage of tendon healing

1. Tendon ruptures/tears
2. BVs are also damaged, platelets in the blood become activated
3. Platelets release growth factors, trigger surrounding inflammatory cells - e.g. macrophages
4. OR - molecules from interior of cells that are ruptured from injury are released and recognised as foreign by the immune system, triggers the inflammatory response
- Inflammation is initially non-specific


Describe the regeneration stage of tendon healing

1. Macrophages stimulate reconstruction - summon endothelial cells that form new BVs + mesenchymal stem cells that start forming new ground substance with collagen
2. At first, type 3 collagen is laid down (rather than type 1) and is haphazardly organised (not in parallel bundles)
- new material looks like watery gel - pink coloured granulation
3. Becomes large nodule (tendon callus) which encloses the old injury site


Compare type 1 and type 3 collagen

Type 3 collagen can be quickly produced but is of a lower quality than type 1 - weaker and less elastic. Type 1 has a more complex structure which takes longer to synthesise but is stronger and more elastic.


Describe the remodelling stage of tendon healing

1. For the new tissue to perform like the old tendon did the collagen needs to be higher quality + be organised in neat parallel bundles aligned in the direction of strain
2. To know which way the direction of force is the cells detect the deformation cycle which occurs when muscles pull the damaged tendon - why load bearing/movement is important during healing
3. Cells break down the callus and replace it with a better, more functionally adapted material - primarily collagen type 1, in parallel arrangement
- Callus decreases in size, tissue left resembles original tendon



Inflammation of the tendon (acute)


Treatment of tenditis

- Rest joint
- Take NSAIDs
- Physiotherapy
- Steroid injections, surgery, shock wave therapy (if more long-term)


Diagnosis of tendinitis

Physical examination


List the symptoms of tendinitis

- Pain - worse with movement
- Difficulty moving joint
- Feeling grating/crackling sensation when moving joint
- Swelling, sometimes w/ heat or redness


Describe methods of prevention of tendinitis

- Warm up before exercising, stretch afterwards
- Wear suitable shoes for exercise
- Take regular breaks from repetitive exercise
- Don't over-exercise tired muscles
- Don't do repetitive exercises



Non-inflammatory degeneration of the tendon caused by micro-tears due to overuse


Complete tendon rupture

Tear of the tendon in which none remains intact


Partial tendon rupture

Tear of the tendon in which some remains intact


List the symptoms of tendon ruptures

- Swelling around joint
- Inability to bear weight
- Bruising
- Sudden, sharp pain at time of injury which develops into a dull ache
- Stiffness
- Snapping/popping sound at time of injury


Diagnosis of tendon ruptures

- Physical examination
- Check for range of movement/weight bearing etc.
- Ultrasound/MRI to show rupture


Describe the treatment of tendon ruptures

- Depends on partial or complete tear, age, health etc.
- All will have physiotherapy
- Non-surgical or surgical treatment options


Describe non-surgical treatment of tendon ruptures

- Plaster cast, brace on injury for 6-8 weeks to keen tendon immobile while it heals
- Crutches to reduce weight bearing
- Pain-relief/anti-inflammatories e.g. NSAIDs


Describe surgical treatment of tendon ruptures

- Often done if active/young/athlete
- Depends on where tendon is ruptured (e.g. if achilles tendon is ruptured at or above the point at which the tendon meets the calf muscle surgery may not be possible)
- Open surgery - one long incision to reach tendon and repair it
- Limited open surgery - make a single incision but it will be shortened
- Percutaneous surgery - number of small incisions to reach tendon and repair it
- Tendon is stitched together to allow more efficient healing
- Chance tendon will rupture again after surgery


How are muscles attached to bones?

Directly via tendons, indirectly via aponeurosis


Describe the macrostructure of a muscle

Origin -> belly -> insertion

(From smallest to largest structure)
1. Myofilaments (proteins responsible for muscle contraction)
2. Myofibrils (tubes of proteins)
3. Muscle fibres (muscle cells)
4. Muscle fascicles
5. Skeletal muscle


Describe the function of muscles

Able to:
- Contract
- Respond to stimulation from nervous system
- Stretch beyond normal resting length
- Revert to normal resting length


List the layers of connective tissue found in muscles

1. Endomysium
2. Perimysium
3. Epimysium



- Thin layer of connective tissue
- Surrounds each muscle fibre (cell)



- Thick connective tissue
- Groups muscle fibres into fascicles
- Protects fascicles from damage, contains capillaries + nerve fibres - allows nutrient transfer



- Thick connective tissue
- Surrounds whole skeletal muscle
- May continue beyond muscle belly as tendon and become continuous with periosteum of bone
- Separates muscle from surrounding tissues and organs


List the components of skeletal muscle fibres (cells)

1. Nuclei
2. Sarcoplasm
3. Myofibrils
4. Terminal cisternae
5. Sarcoplasmic reticulum
6. Transverse tubules
7. Sarcolemma


What is the sarcolemma of a muscle fibre?

- Plasma membrane of a muscle fibre
- Invaginated to from transverse tubules


What are the transverse tubules of a muscle fibre?

- Sarcolemma is invaginated to form transverse tubules (T tubules)
- Penetrate through the fibre, conduct electrical stimuli from sarcolemma


Nuclei of muscle fibres

- Each cell contains multiple flattened nuclei
- Lie beneath sarcolemma


Describe the sarcoplasmic reticulum of a muscle fibre

- Type of smooth endoplasmic reticulum
- Only found in skeletal muscle cells
- Large, concentrated store of calcium


Describe the role of the terminal cisternae of a muscle fibre

- Sarcoplasmic reticulum becomes enlarged, forms bonds, wrap around muscle fibres on either side of T tubules
- Action potential, T tubule stimulates terminal cisternae to release calcium from sarcoplasmic reticulum - triggers contraction of myofibrils


What is the sarcoplasm of a muscle fibre?

- Cytoplasm
- Large amounts of glycogen (provides energy during muscle contraction), and myoglobin (contains stored oxygen)


What are the myofibrils of a muscle fibre?

- Thread-like organelles extend length of muscle fibre
- Each myofibril made of bundles of myofibrils which are arranged into contractile elements of muscle cell i.e. the sarcomere



- Basic functional unit of a myofibril
- Made of contractile proteins
- Supported by structural and elastic proteins
- Have thin and thick actin and myosin filaments, when triggered by release of calcium, actin and myosin filaments slide over each other to shorten sarcomere (contraction)


List the bands/lines/zones of the sarcomere

1. I band
2. Z-line
3. M-line
4. H-zone
5. A-band


I band of the sarcomere

- Isotropic = uniform in each direction
- Lighter band
- Only thin actin filaments
- Bisected by thin, dark Z-line


Z-line of the sarcomere

- Dense protein disc
- Defines end of each sarcomere
- Composed of large elastic protein titin - provides anchorage for thin filaments + coiled elastic titin filaments
- Titin filaments aid elastic recoil of muscle during relaxation


M-line of the sarcomere

- Thin, elastic mesh of interlinking thick fibres
- At centre of sarcomere


H-zone of the sarcomere

- Lighter region of each A band
- Only myosin filaments - deficient in actin filaments


A-band of the sarcomere

- Anisotropic = directionally dependent
- Dark band consisting of parallel, thick filaments with tin filaments partly overlapping them


List the regulatory proteins found in the sarcomere

1. Myosin
2. Actin



- Contractile proteins
- Thick filaments
- Mainly in A-band + H-zone of the sarcomere
- Interacts with actin to create movement
- Made of three domains - head, neck + tail


Describe the function of myosin

- Coupling hydrolysis of ATP to conformational changes in head region of filament
- Enables binding and movement along actin filament



- Contractile protein
- Thin filaments
- Each microfilament is a polymer called F actin, composed of monomeric subunits called G actin
- F actin polymer are made of G actin subunits twisted together
- All actin filaments same length + contain myosin binding sites - myosin heads attach and walk along, causing contraction


Describe the function of actin filaments

To bind to myosin


List the regulatory proteins of the sarcomere

1. Tropomyosin
2. Troponin



- Regulates actin filaments
- Tropomyosin filaments - long molecule made of coil of alpha helices
- Twist around each filament of actin, bind to it in 7 places
- Function - uncovering of myosin head binding sites on actin during excitation (contraction coupling)



- Regulates actin filaments
- Moves tropomyosin away from myosin binding site on actin filaments
- 3 subunits - TnT, TnI + TnC
- Calcium binding to troponin causes conformational shape change that moves troponin away from myosin head binding sites on actin, also moves tropomyosin away from myosin head binding sites, freeing them for cross bridge formation


TnT subunit of Troponin

Binds to tropomyosin near the ends of the tropomyosin sub-units


TnI subunit of Troponin

Binds to actin filaments


TnC subunit of Troponin

Binds to TnI + TnT subunits and calcium ions


What is the role of the structural proteins of the sarcomere?

- Contribute to overall stability and elasticity of myofibrils
- Hold thick + thin filaments in alignment
- Connect sarcolemma to ECM


List the structural proteins of the sarcomere

1. Titin
2. Nebulin
3. Alpha actinin
4. Myomesin
5. Dystrophin



- Regulatory component of sarcomere
- Large singular protein coiled at one end
- Between M-line and Z-line of sarcomere
- Act as spring for actin filaments, attaching them to Z-line



- Structural component of actin
- Sheath-like protein, covers entire actin filament
- Anchors filaments to Z-lines


Alpha actinin

- Makes up Z-lines of sarcomere
- Made of analogous dense bodies in smooth muscle
- Helps anchor actin filaments



- Makes up M-line of sarcomere
- Attaches myosin thick filaments to each other at M-line



- Links actin filaments to sarcolemma
- Transmits tension generated in sarcomere to tendon of muscle
- Reinforces strength of sarcolemma


Explain how the sliding filament mechanism resulting in contraction of the sarcomere

- Allows skeletal muscle to contract and relax
- Movement of thick and thin filaments relative to each other causes shortening of muscle fibre
- Contraction occurs because thick (myosin) filaments bind to thin (actin) filaments by chemical bonds called cross-bridges. Myosin filaments walk along actin filaments, pull them towards centre of sarcomere
- Causes contraction because actin is attached to Z-line + myosin grip along, making H-zone almost non-existent
- Combined shortening of many sarcomeres along number of myofibrils causes whole muscle contraction


Describe the differences in the appearance of sarcomeres in relaxed muscle compared with contracted muscle

Relaxed muscle:
- Sarcomeres have few cross-bridges
- H-zone is large, I band is large
Contracted muscle:
- Sarcomeres have many cross-bridges
- H-zone is small or non-existent
- I-band is smaller
- A-band remains the same


What happens to the length of the A-band when the sarcomere contracts and why?

A-band is constant length contracted or relaxed as length of myofilaments doesn't change during contraction


Which cells stimulate muscle excitation?

Somatic motor neurons/efferent neurons


How is muscle excitation triggered?

Neurones propagate action potentials - series of electrical events involving plasma membrane, altering from resting state


What is required for an action potential to be triggered at the neuromuscular junction?

If the stimulus reaches a threshold value sufficient to open voltage-gated ion channels in cell's plasma membrane - resting membrane potential less negative


What is the effect of stimulation of a muscle at the neuromuscular junction?

Excitation-contraction coupling and muscle fibre contraction


Describe the efferent neurones at the neuromuscular junction

- Terminate on the surface of muscles
- Bulb-like processes
- Relay impulses from CNS -> effector organs, muscles or glands


Where does muscle excitation begin?

Neuromuscular junction = connection between muscle and neurone


Describe the presynaptic membrane at the neuromuscular junction

- Form synaptic end bulbs at end of branches of axon of motor neurone
- At motor end plate of fibre
- Contain synaptic vesicles filled with acetyl choline (neurotransmitter), which is released in response to action potential to stimulate adjoining neuron or motor end end


Synaptic cleft

Small gap between the communicating somatic neurone or motor end plate


Motor end plate

- Part of muscle fibre innervated by somatic motor neurone
- Highly excitable area
- Contains many acetyl choline receptors
- Contains junctional folds for larger surface area for neurotransmitter binding


List the sequence of events which occur at the neuromuscular junction

1. Action potential received
2. Fusion of synaptic vesicles to presynaptic membrane
3. Movement of acetyl choline across synaptic cleft, binding to postsynaptic membrane
4. Sodium influx
5. Depolarisation of postsynaptic membrane
6. Breakdown and removal of acetyl choline from synapse


Describe how the action potential is received at the presynaptic membrane terminal and the effect this has

- AP propagated along presynaptic motor neurone to presynaptic axon terminal
- Causes voltage-gates calcium channels to open, triggering influx of calcium ions from extracellular fluid


Describe fusion of synaptic vesicles to the presynaptic membrane

High calcium concentration causes axon's synaptic vesicles containing acetyl choline to fuse with the presynaptic membrane and release acetyl choline into the synaptic cleft in a process called exocytosis


Describe the effect of acetyl choline binding to the postsynaptic memrbane

- Acetyl choline diffuses across synapse to motor end plate, activating acetyl choline receptors on post-synaptic membrane
- Receptors are ligand-gated channels - undergo conformational change when acetyl choline binds
- Shape change opens channels, allowing influx of cations (mostly sodium ions) down electrochemical gradient, across postsynaptic membrane into muscle cell's sarcoplasm


Describe the effect of the influx of sodium ions on the post-synaptic membrane

- Influx of positively charged sodium ions causes sarcoplasmic side of post-synaptic membrane to become more positive, causing a change in membrane potential
- Change elicits muscle action potential, propagated along sarcolemma and into T tubules
- As action potential is conducted deep into muscle fibre, ryanodine receptors on surface of sarcoplasmic reticulum trigger release of calcium ions - begins process of muscle contraction


Describe the breakdown and removal of acetyl choline from the synapse

- Neurotransmitters left in synapse after synaptic transmission may affect subsequent synaptic events - have to be removed from synaptic cleft
- Broken down by acetylcholinesterase (AChE) a degrading enzyme - breaks down acetyl choline into inactive acetate and choline molecules - transported back through uptake into presynaptic terminals - recycled to synthesis new acetyl choline molecules or removed from cleft by neuroglia


Excitation-contraction coupling

- Somatic motor neurones stimulate contraction - more stimulation = more contraction
- Excitation-contraction coupling = electrical stimulus from nerve fibre ending translates into contraction of muscle
- Takes place within sarcoplasm of muscle fibre, mediated by calcium ions


List the steps in excitation-contraction coupling

1. Stimulus
2. Calcium release
3. Exposure of myosin binding sites
4. Calcium Storage


Describe the initial stimulation and calcium release during excitation-contraction coupling

1. Stimulus
- AP at neuromuscular junction, travels through sarcolemma and the transverse tubules to the terminal cisternae of the sarcoplasmic reticulum which has reservoirs of calcium for muscle contraction
2. Calcium release
- Reception of AP triggers opening of calcium release channels in membrane of sarcoplasmic reticulum - calcium ions flow out into cytosol of muscle fibre


Explain the process of exposure of the myosin binding sites during excitation-contraction coupling

- Calcium travels towards thick + thin filaments, binds to calcium binding sites on TnC subunit of troponin
- Calcium binding causes shape change in troponin
- Troponin is bound to tropomyosin
- Tropomyosin = regulatory protein, covers myosin binding sites on actin filament
- Conformational change in troponin causes conformational change in tropomyosin, uncovering myosin binding sites on actin


Explain the process of calcium storage in excitation-contraction coupling

- No more stimuli received by muscle fibre
- Calcium release channels close
- Intracellular calcium levels return to normal
- Calcium restored to reservoirs in sarcoplasmic reticulum by active transport pumps in its membrane
- Pumps transport calcium, against concentration gradient, into sarcoplasmic reticulum for storage


List the steps of the muscle contraction cycle

1. ATP hydrolysis
2. Cross-bridge formation
3. Power stroke
4. Detachment of myosin from actin


Describe the first step of the muscle contraction cycle

- ATP hydrolysed when it binds to ATP binding site on head of myosin filament
- Hydrolysis of ATP causes conformational change in orientation of myosin head - brings it closer to actin filament
- Phosphate group lost, ADP stays attached to myosin head


Describe cross-bridge formation in the muscle contraction cycle

- Myosin head is free to attach to actin filaments, form cross-bridges
- Myosin head attaches to actin filament, remaining phosphate group released


Describe the power stroke of the muscle contraction cycle

- Myosin head starts to pivot and rotate, releasing ADP
- Generates force, pulls thin filament to centre of sarcomere, prepares myosin head to receive another ATP molecule


Describe the detachment of myosin from actin in the muscle contraction cycle

New ATP binds to ATP binding site on myosin head - detaches from binding site on actin filament, ready for ATP hydrolysis


What is the resting membrane potential?

- The electrical gradient across the cell membrane
- Between -40mV and -90mV in nerve and muscle cells


How is the resting membrane potential maintained in cells

- 3 sodium ions are pumped out and 2 potassium ions are pumped in by the sodium-potassium pump (Na+/K+ ATPase)


What is the actual resting membrane potential of cells and why?

Approx. -70mV as a small amount of sodium ions leak into the cell


Motor unit

All the muscle cells controlled by one nerve cell


Muscle tonus

Tightness of a muscle



Sustained contraction of a muscle, result of a rapid succession of nerve impulses


Refractory peroid

Brief period of time in which muscle cells will not respond to a stimulus


Skeletal muscle

- Long cylindrical cells
- Many nuclei per cell
- Striated
- Voluntary
- Rapid contractions


Cardiac muscle

- Branching cells
- One or two nuclei per cell
- Striated
- Involuntary
- Medium speed contractions


Smooth muscle

- Fusiform cells
- One nucleus per cell
- Nonstriated
- Involuntary
- Slow, wave-like contractions


List the types of muscle

- Smooth
- Cardiac
- Skeletal


Muscle hypertrophy

Increase in total mass of a muscle, results from an increase in size/number of individual muscle fibres


Muscle atrophy

Decrease in total mass of a muscle


What type of movements produce the most muscle hypertrophy

- When muscle is 'loaded' during contractions (e.g. lifting weights)
- Few strong contractions per day = significant hypertrophy of muscle in 6-10weeks


Describe the process of muscle hypertrophy

- Rate of synthesis of muscle contractile proteins greater when hypertrophy is developing, leading to greater number of myosin and actin filaments in the myofibrils
- Some myofibrils split within hypertrophying muscle to form new myofibrils - enlarge then divide longitudinally so fibrils become more numerous
- Enzyme systems providing energy also increase - enzymes of glycolysis, allowing for rapid supply of energy during short-term forceful contractions


List the requirements for muscle hypertrophy

1. Positive energy balance - consuming more calories than burned - needed for anabolism, therefore muscle hypertrophy
2. Increased requirement for protein - esp. branched chained amino acids, required for elevated protein syntesis
3. Training variables (strength training) - frequency, intensity, total volume affect


Define muscle fatigue

Inability to maintain muscle power output - reversible by rest. Has fast onset and fast recovery. There are several types but all reduce muscle force, shortening velocity and relaxation rate. Force loss occurs earliest and is greatest.


How does muscle fatigue differ from injury?

Fatigue is quickly reversible by rest - injury requires much longer recovery


List the types of muscle fatigue

1. Central fatigue (within the CNS)
2. Peripheral fatigue


Describe central fatigue

- Not muscular
- Loss of excitability in the motor cortex
- Upper motor problem - probably affected by sensory inputs from metabo-receptors in muscle
- Can also include failure of transmission in peripheral nerve + NMJ (pathological)
- Common in occupational work/recreational sport
- Sensation = discomfort/lack of motivation
- Probably not a factor in elite sport - athletes have better potassium metabolism


Describe peripheral fatigue

- Failure of excitation-contraction coupling, T tubule action potential, sarcoplasmic reticulum activation, calcium ion release
- Leads to failure of force generation at cross bridges
- Failure of ATP generation by depletion of energy stores


List common misconceptions about the causes of fatigue

- Fatigue is not due to lack of ATP - ATP concentrations increase during exercise
- Lactic acid is not the cause of fatigue


List the causes of fatigue

- ADP, phosphate + hydrogen ion concentration increase as ATP is broken down
- High concentration affects calcium pumping process and ATPase function
- Hydrogen competes with calcium for troponin binding
- Phosphate, ADP and hydrogen inhibit calcium ion release and calcium re-uptake into sarcoplasmic reticulum which affects force and speed of shortening and relaxation


Describe how muscles are supplied with energy in activities lasting a few seconds (short duration/high power)

- ATP is regenerated by breakdown of creatine phosphate
- Creatine phosphate -> creatine by creatine metabolism and ADP -> ATP
- Uses inefficient anaerobic glycolytic metabolism (produces 2 ATP)


Describe how muscles are supplied with energy in activities lasting longer than a few seconds up to 3 hours

- Glycogen metabolism:
- Glycogen -> glucose-1-phosphate -> glucose-6-phosphate (by enzymes glycogen phosphorlyase + phosphoglucomutase)
- Glucose-6-phosphate follows normal glycolysis to produce pyruvate (+ 2 ATP + 2NADH)
- Products of glycolysis go on to Krebs cycle + electron transport chain
- Net product = 36 ATP


Describe how muscles and supplied with energy in activities lasting longer than 3 hours (long duration/low power)

- Lipid metabolism starts after 90% of initial glycogen has been used
- Lipids come from adipocytes and intramuscular stores
- Very long duration activities utilise lipids almost entirely
1. Triglycerols -> fatty acids + glycerol
2. Fatty acids -> acetyl CoA
3. Acetyl CoA follows normal Krebs cycle + ETC


Strength training

- Small numbers of repetitions, high force contractions
- Loads close to max, 10-20 reps. per session
- Increases muscle mass (type 1 fibres)


Endurance training

- Large numbers of repetitions, low force contractions
- Can decrease muscle mass (type 1 unused so will atrophy, type 2 don't increase muscle mass)


List the stages of strength training involved with muscle hypertrophy

1. Neural
2. Hypertrophic


Neural stage of strength training

- First 4-6 weeks
- Activation of motor units
- CNS response - increased recruitment of largest motor units + higher maximal firing rates


Hypertrophic stage of strength training

- Significant hormonal changes - After strenuous training, GH, local GFs (IGFs etc.), insulin and testosterone elevated
- Causes hypertrophy of muscle fibres
- Connective tissues also strengthen to cope w/ increasing forces
- Hypertrophy is slow - starts with development of new contractile filaments added laterally to existing myofibrils
- Later there is fibril splitting. Most enlarged fibrils divide longitudinally, fibrils become more numerous


Describe the effects of endurance training

- Mostly aerobic metabolism
- Improved cardiovascular performance
- Improved metabolic performance
- Selective hypertrophy of type 2A + B fibres


Describe the ways in which cardiovascular performance is improved by endurance training

- Oxygen delivery
- Cardiac output
- Regional flow
- Capillary density
- Blood volume


Describe the ways in which metabolic performance is improved by endurance training

- Enzyme concentrations
- Mitochondria density
- Substrate storage
- Mobilisation


List the types of muscle fibres

Type 1 = slow
Type 2A = fast fatigue resistant
Type 2B = fast fatiguing


Compare the twitch capabilities of:

a) Type 1
b) Type 2A
c) Type 2B

muscle fibres

a) Smaller twitch
b) Larger twitch
c) Largest twitch


Compare the rate of fatigue of:
a) Type 1
b) Type 2A
c) Type 2B

muscle fibres

a) Slower fatigue
b) Moderate fatigue
c) Fast fatigue


What colour are:

a) Type 1
b) Type 2A
c) Type 2B

muscle fibres

a) Red
b) Red
c) White


What type of respiration is used by:

a) Type 1
b) Type 2A
c) Type 2B

muscle fibres

a) Aerobic
b) Anaerobic + aerobic
c) Anaerobic


Compare the number of mitochondria and level of myoglobin found in:

a) Type 1
b) Type 2A
c) Type 2B

muscle fibres

a) Lots of myoglobin (therefore lots of oxygen) and high numbers of mitochondria
b) Moderate number of mitochondria and some myoglobin
c) Low level of myoglobin, few mitochondria


List the regions of the mesoderm

1. Paraxial mesoderm
2. Intermediate mesoderm
3. Lateral plate mesoderm


Paraxial mesoderm

- Forms from cells moving bilaterally and cranially from the primitive streak
- Lies adjacent to notochord and neural tube
- Forms somites


What is formed by the intermediate mesoderm

The genitourinary system


Lateral plate mesoderm

Split by a cavity (intraembryonic coelom) into two layers:
1. Somatic or parietal layer
2. Splanchnic or visceral layer


Which part of the mesoderm do skeletal muscles originate from?

Paraxial mesoderm


Which part of the mesoderm does smooth muscle (gut and derivatives) originate from?

Visceral layer, lateral plate mesoderm around gut tube


Which part of the mesoderm does smooth muscle (pupil, mammary and sweat glands) originate from?



Which part of the mesoderm does cardiac muscle originate from?

Visceral layer, lateral plate mesoderm around heart tube


Which genes control somitogenesis?

- FGF family
- Wnt
- Notch


Which part of the mesoderm forms somites?

Paraxial mesoderm gets organised into segments - somites


How can the number of somites be used to determine the age of an embryo?

- Somites appear at a rate of approximately 3 pairs a day until the end of week 5
- Can accurately determine the age of an embryo by the number of pairs


How many pairs of somites are present by the end of week 5 of development?

42-44 pairs

- 4 occipital
- 8 cervical
- 12 thoracic
- 5 sacral
- 5-7 coccygeal


What is a somite?

A block of paraxial mesoderm which gives rise to skeletal muscles


Describe the process of epithelialisation of somites

- Segmented blocks of paraxial mesoderm are transformed into spheres
- Epithelial cells around a lumen


Describe differentiation of somites

- Cells in the ventral and medial area undergo and epithelial mesenchymal transition - become sclerotome (form vertebrae and ribs)
- Cells in dorsal half form dermomyotome
- Dermomyotome splits again to form dermatome (dermis of back) and myotome (muscles)


What is responsible for regulation of muscle development in embryos?

MYOD and MY45
- Transcription factors
- Activate muscle-specific genes
- Enable the differentiation of myogenic precursor cells in the dermomyotome into myoblasts



- Myotome cells - committed muscle cell precursors
- Undergo cell division under the influence of growth factors


What happens to myoblasts when growth factors are depleted?

- Stop dividing
- Secrete fibronectin onto ECM bind to it via an integrin - crucial step
- Align into chains and fuse, cell membranes disappear - multinucleated myotubes - primary myotubes


How is differentiation of of myoblasts mediated?

Myogenin mediates the differentiation of myoblasts



- Required for myoblast formation
- Inactivates MYF5 in mice results in delayed development in the intercostal and paraspinal regions


What is the effect of mutation in MYF5 and MYOD1

Loss of function mutation results in a complete lack of skeletal muscle formation


Where is smooth muscle found?

- Walls of GI tract
- Walls of arteries and veins
- Around glands


Describe smooth muscle development

- Originates from splanchnic mesoderm (except ciliary musce, sphincter pupilae of eye - ectoderm)
- Serum response factor (SRF) is responsible for smooth muscle cell differentiation
- SRF upregulated by kinase phosphorylation pathways
- Myocardin/myocardin related transcription factors enhance SRF activity


How do myoblasts for skeletal muscle?

- Myoblasts fuse to form long multinucleated fibres - myotubes
- Skeletal muscle = striated, contain many mitochondria


Describe the the development of tendons

Tendons are derived from the sclerotome under the control of the transcription factor scleraxis


Describe the development of cardiac muscles

- Originates from splanchnic mesoderm surrounding the developing heart tube
- Striated - different from skeletal
- Myoblasts adhere to each other via intercalated discs


List the articulations of the elbow joint

1. Humeroulnar -trochlear notch of the ulna and trochlea of the humerus
2. Humeroradial -head of the radius and capitulum of the humerus


List the important bony landmarks of the elbow joint

- Medial epicondyle (medial side of distal humerus)
- Lateral epicondyle (lateral side of distal humerus)
- Olecranon (proximal end of ulnar, point of elbow)


List the ligaments found in the elbow

- Radial collateral ligament (from lateral epicondyle)
- Ulnar collateral ligament (from medial epicondyle)


Describe the blood supply to the elbow joint

Arterial supply = cubital anastamosis (branches of the brachial and deep brachial arteries)


Describe the innervation of the elbow joint

Median, musculocutaneous and radial nerves anteriorly and ulnar nerve posterior;y


List the movements of the elbow joint

Extension = triceps brachii and anconeus
Flexion = Brachialis, biceps brachii, brachioradialis


Which joints are responsible for movements of the forearm?

- Elbow joint (humeroulnar and humeroradial)
- Proximal radioulnar
- Distal radiaoulnar


Describe the position of the proximal radioulnar joint

Located immediately distal to the elbow joint, enclosed within the same articular capsule


Describe the articulation of the proximal radioulnar joint

Articulation between the head of the radius and the radial notch of the ulnar


Which ligament stabilises the proximal radioulnar joint?

The annular radial ligament - forms a collar around the joint


List the types of movement possible at the proximal radioulnar joint

1. Pronation = pronator quadratus and pronator teres
2. Supination = supinator and biceps brachii


Describe the location of the distal radioulnar joint

Located just proximally to the wrist joint


Describe the articulation of the distal radioulnar joint

Articulation is between the ulnar notch of the radius and the ulnar head


Describe the ligament which stabilises the distal radioulnar joint

Articular disk:
- Fibrocartilaginous ligament
- Binds the radius and ulna together, holds them together during movement at the joint
- Separates the distal radioulnar joint from the wrist joint


List the movements possible at the distal radioulnar joint

1. Pronations -pronator quadratus and pronator teres
2. Supination - supinator and biceps brachii


Interosseous membrane

- Sheet of connective tissue that joins the radius and ulna together between the radioulnar joints
- Spans between the medial radial border and the lateral ulnar border


List the functions of the interosseous membrane

1. Holds the radius and ulnar together during pronation and supination, provides stability
2. Acts as a site of attachment for muscles of the forearm
3. Transfers forces from radius to ulna


List the divisions of the muscles in the anterior department of the forearm

1. Superficial
2. Intermediate
3. Deep


In general, what movements are the muscles of the anterior compartment of the forearm responsible for?

Flexion at the wrist and fingers and pronation of the forearm


List the muscles of the superficial compartment of the anterior forearm

1. Flexor carpi ulnaris
2. Palmaris longus
3. Flexor carpi radialis
4. Pronator teres


Where do the superficial muscles of the anterior forearm originate from?

All originate from the medial epicondyle of the humerus


Describe the innervation of the superficial muscles of the anterior forearm

Ulnar nerve = flexor carpi ulnaris

Median nerve = Palmaris longus, flexor carpi radialis, pronator teres


List the movements of the superficial muscles of the anterior forearm

Flexor carpi ulnaris = flexion/adduction at wrist
Palmaris longus = flexion at wrist
Flexor carpi radialis = flexion and abduction at wrist
Pronator teres = pronation of forearm


List the muscles of the intermediate compartment of the anterior forearm

Flexor digitorum superficialis


Why is the flexor digitorum superficialis a good anatomical landmark?

The median nerve and ulnar artery pass between its two heads, then travel posterior


List the attachments of the flexor digitorum superficialis

- 2 heads - one from medial epicondyle of humerus, one from radius
- Splits into 4 tendons in wrist, travel through carpal tunnel, attaches to middle phalanges of fingers


Describe the actions of the flexor digitorum superficialis

Flexion of metacarpophalangeal joints and proximal interphalangeal joints and flexion of the wrist


Describe the innervation of the flexor digitorum superficialis

Median nerve


List the muscles of the deep compartment of the anterior forearm

1. Flexor digitorum profundus
2. Flexor pollicis longus
3. Pronator quadratus


Describe the actions of the muscles of the deep compartment of the anterior forearm

1. Flexor digitorum profundus = flexion of distal interphalangeal joints, metacarpophalageal joints and wrist
2. Flexor pollicis longus = Flexion of interphalangeal joint and metacarpophalangeal joint of the thumb
3. Pronator quadratus = pronation of the forearm


Describe the innervation of the muscles of the deep compartment of the anterior forearm

1. Flexor digitorum profundus = medial half by ulnar nerve, lateral half by median nerve
2. Flexor pollicis longus = median nerve
3. Pronator quadratus = median nerve


What is the general function of the muscles of the posterior forearm?

Produce extension at the wrist and fingers


Describe the innervation of the muscles of the posterior forearm

Radial nerve


How can the muscles of the posterior forearm be divided?

2 layers - deep and superficial, separated by a layer of fascia


List the muscles of the superficial layer of the posterior forearm

1. Extensor carpi radialis brevis
2. Extensor digitorum
3. Extensor carpi ulnaris
4. Extensor digiti minimi
5. Extensor carpi radialis longus
6. Anconeus
7. Brachioradialis


Which of the four muscles of the superficial layer of the posterior forearm attach to the lateral epicondyle?

1. Extensor carpi radialis brevis
2. Extensor digitorum
3. Extensor carpi ulnaris
4. Extensor digiti minimi


Describe the actions of the muscles of the superficial layer of the posterior forearm

Brachioradialus = Flexes elbow
Extensor carpi radialis longus/brevis = extend and abduct the wrist
Extensor digitorum = Extends fingers at MCP and IP joints
Extensor digiti minimi = Extends little finger, contributes to extension of wrist
Extensor carpi ulnaris = extension and adduction of wrist
Anconeus = extends elbow joint, abducts ulna during pronation


List the muscles of the deep layer of the posterior forearm

1. Supinator
2. Abductor pollicis longus
3. Extensor pollicis brevis
4. Extensor pollicis longus
5. Extensor indicis proprius


Describe the actions of the muscles of the deep layer of the posterior forearm

Supinator = supination
Abductor pollicis longus = abducts the thumb
Extensor pollicis brevis = extension at MCP and CM joints of thumb
Extensor pollicis longus = extends all joints of thumb
Extensor indicis proprius = extends index finger


Describe the arterial supply to the forearm and hand

In the distal cubital fossa the brachial artery bifurcates into radial (posterior) and ulnar (anterior) arteries which anastomose in the hand, forming two arches - superficial palmar arch and deep palmar arch


List the types of nerve cells which peripheral nerves contain axons from

1. Sensory neurones (afferents)
2. Motor neurones (efferents)


How many pairs of cranial nerves are there?

12 pairs


How many pairs of spinal nerves are there?

31 pairs


Describe the segmental arrangement of the spinal nerves

Cervical = 8
Thoracic = 12
Lumbar = 5
Sacral = 5
Coccygeal = 1


List the plexuses formed by the spinal nerves

- Cervical plexus (C1-C5)
- Brachial plexus (C5-T1)
- Lumbosacral plexus (T12-S5)


What is innervated by the brachial plexus and which nerves does it form?

Innervation of the upper limb
Nerves =
- Axillary
- Musculocutaneous
- Radial
- Ulnar
- Median


Describe the types of axons in peripheral nerves

Myelinated = large axon diameter, fast conduction velocities, for touch, vibration, motor

Unmyelinated = small axon diameter, slow conduction velocities, for pain, cold, hot


List the types of peripheral receptors and their modalities

- Mechanoreceptors = mechanical deflection, touch
- Thermoreceptors = hot/col
- Nociceptors = noxious (pain)
- Special sensory = vision, taste, olfaction



Each muscle is supplied by a particular level/segment of the spinal cord and by its corresponding spinal nerve



An area of skin innervated by a particular level/segment of the spinal cord and its corresponding spinal nerve


Describe the pathway for voluntary movement

Motor cortex (upper motor neurone) -> brainstem/spinal cord (lower motor neurone) -> muscle -> movement


Describe the reflex pathway

No upper motor neurone component

Brainstem/spinal cord -> muscle



Sensations arising from the deep field (muscles and joints) as a result of the actions of the organism

Movement sense = awareness of joint movement

Position sense = awareness of static joint position