Muscular Systems


Assessment Notes

posted 11 Oct 2010 14:01 by NicolaAvery .

1. List four muscles from the upper limbs, trunk and lower limbs and state the action of each

Upper Limbs:
Deltoid - the fleshy part of the  shoulder, abducts away from the body, flexes and extends the arm, laterally rotating the shoulder joint.
Brachialis - beneath biceps anterior of upper arm, the main flexor of the elbow joint
Flexor Carpi Radialis - anterior forearm, flexes wrist joint, when acting with extensor carpi radialis - abducts the joint.
Extensor Carpi Digitorum - posterior of forearms, spans wrist and elbow joints, extends fingers, elbow or wrist joints.
Trunk:
Trapezius - kite shaped in upper back, adducts inward to the body and rotates inferior angle of scapula laterally, flexes neck and head, raises shoulder, draws scapula backwards as shoulders are in use.
Teres Major - side of scapula to humerus, adducts and medially rotates humerus, extends shoulder joint
Rectus Abdominis - abdominal wall, supports viscera (abdominal internal organs, flexes vertebral column
Internal Oblique - waist - deep to external oblique, produces rotation of the waist when working antagonistically, flexes vertebral column
Lower Limbs:
Quadriceps Femoris - vastus lateralis - extends knee, rectus femoris - extends knee and hip, vastus intermedius - extends knee, vastus medialis - extends knee, together all four act as extensor of knee joint.
Sartorius - crosses over from hip to medial side of knee, flexes and abducts hip and knee, rotates femur laterally
Gastrocnemius - calf muscle - joins with soleus to from tendon of achilles, plantarflexes ankle for pointing / rising on ball of foot)
Soleus - deep to gastrocnemius - plantarflexus ankle walking or rising onto demi-pointe with knees bent)

2. Compare and contrast skeletal and smooth muscles

Smooth muscle - involuntary or non-striated, not under conscious control. cells have one nucleus, spindle shaped. Intrinsic ability to contract & relax also autonomic nerve impulses (but some can initiate contraction independently of nerve impulses), some hormones & local metabolites.  Only completely relaxed for short periods. Contraction slower, more sustained than skeletal - found in walls of hollow organs - regulate diameter of blood vessels, parts of respiratory tract, propel contents of ureters, ducts of glands and alimentary tract, expelling contents of urinary bladder and uterus.

Cardiac are also smooth muscles but in the heart wall only - striated, not under conscious control, each fibre has a nucleus and more than one branch. The ends of cells in close contact with adjacent cells - adjacent 'lines' are intercalated discs - thicker, darker than ordinary stripes so looks more like sheet. So when heart contracts - like wave across cells because adjacent and connected - does not require each individual cell to stimulate. Heart beats without external nerve stimulation but rate is influenced by autonomic nerve impulses, some hormones, local metabolites

Skeletal muscles cover the bones and joints - striated (striped appearance when seen under microscope), voluntary - under conscious control but also subconscious e.g diaphragm movements when sleeping. They are attached to bones via tendons and used to move skeleton. They are cylindrical , contain several nuclei, can be up to 25 cm long.

The muscles are covered in three layers of connective tissue - epimysium, within muscle cells are in bundles of fascicles, each fascicle also covered in connective tissue - perimysium. Inside fascicles - each cell is covered in finer connective tissue - endomysium. Fibres bind and at end of muscle blend to form tendon - is rope-like appearance but sometimes sheet-like known as aponeurosis. Cell membrane is the sarcolemma, cytoplasm of cells - sarcoplasm - has tiny contractile filaments. Also many mitochondria - essential for ATP to power contraction. Myoglobin (oxygen-binding similar to haemoglobin) stores oxygen in muscles. Calcium released into sarcoplasm by nerve stimulation.

3. Write short notes on muscle tone and muscle fatigue

Muscle tone occurs where some fibres are slightly contracting whilst others are relaxing. This constant movement provides firmness to muscles, protecting joints which stabilise the body / skeleton such as keeping your head upright. The combination of some contracting whilst others are relaxing means the effort is distributed so less tiring, stress involved on the overall muscle.

Muscle fatigue occurs when muscles are working too hard that they exceed their supplies of oxygen and fuel in the form of energy which could ultimately result in no movement at all. Muscles require ATP energy (which is usually derived from a breakdown of carbohydrates and fats or proteins), with an adequate oxygen supply releasing the energy stored within the fuel molecules (e.g. glucose). However a lack of oxygen causes a build up in lactic acid from a result of excessive anaerobic exercises (e.g. this happens to me in taekwondo competition fights) and the muscles will stop contracting, becoming increasingly stiff, causing pain.


4. Briefly explain the sliding filament theory of muscle contraction

Muscles generally move in opposing pairs with the agonist contracting whilst the antagonist is relaxed. Contraction of a muscle involves the muscles fibres shortening and becoming thicker. Different forces of contraction depend on the number of fibres involved in the contraction e.g. greater force when more fibres contract.

Isometric contraction is where the length of the muscle stays the same but the tension increases in order to overcome the opposing force such as trying to push a heavy load. Isotonic contraction is when the tension remains the same but the length changes in actions such as lifting and lowering small objects.

The two different myofilaments are involved in the contraction process:
  • Actin - thin contractive myofilaments - arranged in repeating units known as sarcomeres - light bands seen under microscope
  • Myosin- thick contractive myofilaments - dark bands seen under microscope


Each sarcomere bound by dense stripe known as the  Z-line - myosin fibres attached with actin in middle of sarcomere which overlaps myosin. When a muscle contracts, nerves stimulate the muscle cells releasing calcium and myosin cross-bridges become in contact with the binding sites of the actin myofilaments (triggered by calcium). Then APT provides energy for the actin myofilaments and myosin myofilaments to slide safely across each other. The Z-lines move closer through this action which shortens the overall length of each sarcomere.



Courtesy of http://www.flickr.com/photos/antbay/4714665902/#/

When the nerve stimulation stops, the muscles relaxes and calcium is pumped back whick break the cross-bridges, causing the actin and myosin myofilaments to return to their original positions.

Muscle tone and Muscle Fatigue

posted 29 Aug 2010 11:01 by NicolaAvery .

Muscle tone occurs where some fibres are slightly contracting whilst others are relaxing. This constant movement provides firmness to muscles, protecting joints which stabilise the body / skeleton such as keeping your head upright. The combination of some contracting whilst others are relaxing means the effort is distributed so less tiring, stress involved on the overall muscle.

Muscle fatigue occurs when muscles are working too hard that they exceed their supplies of oxygen and fuel in the form of energy which could ultimately result in no movement at all. Muscles require ATP energy (which is usually derived from a breakdown of carbohydrates and fats or proteins), with an adequate oxygen supply releasing the energy stored within the fuel molecules (e.g. glucose). However a lack of oxygen causes a build up in lactic acid from a result of excessive anaerobic exercises (e.g. this happens to me in taekwondo competition fights) and the muscles will stop contracting, becoming increasingly stiff, causing pain.


Example of muscles, positions and actions

posted 29 Aug 2010 10:57 by NicolaAvery .

Muscle origin - the proximal attachment to bones, joints etc - the fixed end of a muscle which barely moves in action i.e. the bone remains still whilst the muscle contracts.
Muscle insertion - the distal attachment to bones, joints, tendons etc - flexible, moving end of a muscle - the point to which the force of the muscle is directed. A muscle always works in the direction from insertion to origin.

Upper Limbs:
Deltoid - the fleshy part of the  shoulder, abducts away from the body, flexes and extends the arm, laterally rotating the shoulder joint.
Brachialis - beneath biceps anterior of upper arm, the main flexor of the elbow joint
Flexor Carpi Radialis - anterior forearm, flexes wrist joint, when acting with extensor carpi radialis - abducts the joint.
Extensor Carpi Digitorum - posterior of forearms, spans wrist and elbow joints, extends fingers, elbow or wrist joints.
Trunk:
Trapezius - kite shaped in upper back, adducts inward to the body and rotates inferior angle of scapula laterally, flexes neck and head, raises shoulder, draws scapula backwards as shoulders are in use.
Teres Major - side of scapula to humerus, adducts and medially rotates humerus, extends shoulder joint
Rectus Abdominis - abdominal wall, supports viscera (abdominal internal organs, flexes vertebral column
Internal Oblique - waist - deep to external oblique, produces rotation of the waist when working antagonistically, flexes vertebral column
Lower Limbs:
Quadriceps Femoris - vastus lateralis - extends knee, rectus femoris - extends knee and hip, vastus intermedius - extends knee, vastus medialis - extends knee, together all four act as extensor of knee joint.
Sartorius - crosses over from hip to medial side of knee, flexes and abducts hip and knee, rotates femur laterally
Gastrocnemius - calf muscle - joins with soleus to from tendon of achilles, plantarflexes ankle for pointing / rising on ball of foot)
Soleus - deep to gastrocnemius - plantarflexus ankle walking or rising onto demi-pointe with knees bent)

temp notes

posted 14 Aug 2010 09:12 by NicolaAvery .   [ updated 14 Aug 2010 11:28 ]

R&W 39,40, 414-30
600 muscles in body - 40-50% of human body weight.Made of cells known as fibres
Muscle tissue:
- smooth - involuntary or non-striated, not under conscious control. cells have one nucleus, spindle shaped. Intrinsic ability to contract & relax also autonomic nerve impulses (but some can initiate contraction independently of nerve impulses), some hormones & local metabolites. 

Only completely relaxed for short periods. Contraction slower, more sustained than skeletal - found in walls of hollow organs - regulate diameter of blood vessels, parts of respiratory tract, propel contents of ureters, ducts of glands and alimentary tract, expelling contents of urinary bladder and uterus.

- cardiac - heart wall only - striated, not under conscious control, each fibre has a nucleus and 1+ branches, ends of cells in close contact with adjacent cells - adjacent 'lines' are intercalated discs - thicker, darker than ordinary stripes so looks more like sheet. So when heart contracts - like wave across cells because adjacent and connected - does not require each individual cell to stimulate. Heart beats without external nerve stimulation but rate is influenced by autonomic nerve impulses, some hormones, local metabolites

- skeletal - striated (stripes seen under microscope), voluntary - under conscious control but also subconscious e.g diaphragm in sleep. Attached to bones via tendons and used to move skeleton. Cylindrical , contain several nuclei, can be up to 25 cm long.



Muscle is covered in connective tissue - epimysium, within muscle cells are in bundles of fascicles, each fascicle also covered in connective tissue - perimysium. Inside fascicles - each cell covered in finer connective tissue - endomysium. Fibres bind & at end of muscle blend to form tendon - is ropelike but sometimes sheet - aponeurosis.

Cell membrane - sarcolemma, cytoplasm of cells - sarcoplasm - has tiny contractile filaments. Also many mitochondria - essential for ATP to power contraction. Myoglobin (oxygen-binding similar to haemoglobin) stores oxygen in muscles. Calcium released into sarcoplasm by nerve stimulation.

Actin - thin contractive myofilaments - arranged in repeating units - sarcomeres - light bands seen under microscope

Myosin- thick contractive myofilaments - dark bands seen under microscope

Each sarcomere bound by dense stripe - Z-line - myosin fibres attached with actin in middle of sarcomere - overlaps myosin.

Contraction - stimulated by motor nerve impulses in spinal cord or brain, ending at neuromuscular junction - axons of motor neurones divide into fine filaments, end in 'motor-end plates', where myelin sheath absent and passes to sensitive fibres on muscle surface (like synapse). A nerve fibre and muscle fibres = motor unit.

Action potential (..electrical charge) spreads along sarcolemma through network of channels through sarcoplasm, releases calcium which triggers myosin binding to actin filament forming 'cross-bridges'. ATP provides energy for two filaments to slide over each other - pulling Z-lines closer and shortening the sarcomere. (Sliding filament theory)

Relaxation - when nerve stimulation stops, calcium pumped back into intracellular storage, breaking cross bridges so that myosin, actin slide back to original positions, sarcomeres are then lengthened etc

Muscle functions:

- tone - fibre contracts either completely or not at all, degree of contraction depends on no of fibres as well as frequency of stimulation. better tone allows better contraction, protection of joints, better firmness and shape.
- fatigue - muscles need adequate supply of oxygen, fuel molecules such as glucose - fatigue occurs when muscle working exceeds supply of these. ATP may be used if supplies of fat & carbohydrate exhausted, but needs adequate oxygen supply. Otherwise less-efficient anaerobic pathways used which lead to excess lactic acid
- recovery - depending on degree of exertion, oxygen debt remains and body converts lactic acid to pyruvic acid, replaces energy stores.

Movement

Antagonistic pairs - most muscles arranged so action of muscles oppose each other e.g. if bending elbow, where main flexors on front of upper arm contract, back muscles of upper arm must relax in order to prevent injury.




Common disorders
(from course notes)
- atony - lack of normal tension or tone in muscle
- atrophy - withering/lack of growth of muscle e.g polio (is opposite to hypertrophy e.g. exercise, stress produces muscle growth)
- dystrophy - progressive destruction of tissue - duchenne, facioscapulohumeral, myotonic (R&W 430)
- crush syndrome - from sustained pressure - ischaemia resulting in massive muscle necrosis, when pressure released - myoglobin, necrotic products enter blood - toxic to kidneys and renal failure may develop. Also possible complication is infection by anaerobic microbes - clostridium perfringens causing gas gangrene (R&W 430)
- cramp - localised involuntary contraction - caused by insufficient circulation & build up of waste products - occurs with extreme exercise, heat, or salt or water depletion
- fibrositis/fibromyalgia - stiffness, pain, inflammation of soft tissues especially fibrous connective tissues of tendons, ligaments. Caused by build up waste - e.g. lactic acid, urea inside muscles. Can be acute, often associated with chronic arthritis, rheumatic conditions - worsened by stress, also lumbago, torticollis, Wry neck
- myositis - inflammation of muscle
- rupture - burst, tear of fascia or sheath - can take longer to heal than a simple fracture
- spascitity - excessive contraction caused by hyperactive spinal reflexes, may be congenital - more often a result of CNS disorder such as MS, stroke, RTA
- sprain - damage to joint with pain,swelling resulting from ligament trauma
- strain - rupture, tearing of muscle tissue from injury
- stress - tension, pain





Muscle structure


  • Face 
    • occipitofrontalis (unpaired)
    • levator palpebrae superioris
    • orbicularis oculi
    • buccinator
    • orbicularis oris (unpaired)
    • masseter
    • temporalis
    • pterygoid
  • Neck
    • sternocleidomastoid
    • trapezius
  • Shoulder, upper limb
    • deltoid
    • pectoralis major
    • coracobrachialis
    • biceps
    • brachialis
    • triceps
    • brachioradialis
    • pronator quadratus
    • pronator teres
    • supinator
    • flexor carpi radialis
    • flexor carpi ulnaris
    • extensor carpi radialis longus and brevis
    • extensor carpi ulnaris
    • palmarus longus
    • extensor digitorum
  • Back
    • rhomboid (todo)
    • latissimus dorsi
    • teres major
    • quadratus lumborum
    • sacrospinalis (erector spinae)
  • Abdominal wall
    • rectus abdominus
    • external oblique (note!!!)
    • internal oblique
    • transversus abdominus
  • Pelvic floor
    • levator ani
    • coccygeus
  • Hip & lower limb
    • psoas
    • iliacus
    • quadriceps femoris
    • obturators
    • gluteals
    • sartorius
    • adductor group
    • hamstrings
    • gastrocnemius
    • anterior tibialis
    • soleus

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