Mod 4 Musculoskeletal system Anatomy of the head, neck and trunk Flashcards
What is myosin?
Myosin (thick) close to the M line
What is actin?
actin (thin) close to the Z line
How does the muscle contract with actin and myosin?
1) the myosin pulls the actin along the cross-bridges of the myosin filaments
2) the myosin filaments attach to the actin filaments and exert force for them to move (a sliding mechanism)
Muscle contraction with actin and myosin ext.
- The myosin head extends and attaches to the binding site on actin (forming the cross-bridge) also where ATP binds and converts it to ADP.
- the Powerstroke is triggered when the myosin pulls the actin towards the M line (shortening the muscle)
Ca+2 and muscle contractions?
- muscles contractions are associated with the Ca2+ levels
- tropomyosin: relaxes the muscle as it blocks the cross-bridge on actin
- Ca+ binds to troponin –> it allows the binding site
- Ca+ ions are stored in the SR and are released from the NS
- neurotrans. are released and bind to receptors depolarises the membrane of the muscle fiber.
- the impulse travels down the T-tubules and opens the Ca+ stores, calcium ions flow to the myofibrils where a muscle contraction is triggered
Actin and myosin summary?
The actin and myosin slide along with each other, the sarcomere shortens as the Z lin draws closer to the M line (shortening and then contracting the muscle).
What is the sarcoplasmic reticulum?
It is smooth endoplasmic reticulum in muscle fibres
What are myofibrils surrounded by?
Myofibrils are surrounded by sarcoplasmic reticulum and T-tubules
What does the sarcoplasmic reticulum store?
The sarcoplasmic reticulum store Ca 2+ released during a muscle contraction
What are T-tubules?
T-tubules are a part of a sarcolemma that runs between the SR –> and AP propagating down T-Tubules cause the release of Ca+ from the SR: which allows the actin and myosin to bind
What are thin filaments made of?
Thin filaments are made of actin, tropomyosin, troponin
What is tropomyosin?
Tropomyosin blocks myosin binding site in the relaxed muscle (with a protein blocking the binding site on myosin-binding sites on actin)
Troponin?
Has the binding site for Ca+, the Ca+ binds to the troponin, making the tropomyosin move away from the active sites on actin, the actin then binds to myosin to form cross-bridges (ATP)
What are thick filaments?
Thick filaments are myosin which has binding sites for ATP
Muscle contraction summary
1) AP travels down a motor neuron
2) Acetylcholine is released at the neuromuscular junction (synapse between neuron and muscle)
3) AP runs down the sarcolemma of the muscle
4) AP travels down the T-tubules
5) Ca 2+ is released from the Sarcoplasmic reticulum
6) Ca+ causes actin and myosin to bind
7) sarcomeres shorten
8) muscle contracts
What are axial muscles?
Muscles of the head and neck are in includes in the axial muscles. The muscles of facial expression, mastication, pharynx, and larynx. Muscles of the vertebral column and the thorax, abdomen and pelvis
What are muscles of facial expression?
mostly originate on the skull and attach to the fascia and the skin, the contractions move the skin and controls the orifices (openings like eyes and mouth), and basis for facial expression.
LABEL the parts of facial expression!
Occipitofrontalis (forehead), orbiclaris oculi (eyes), orbicularis oris (Oral) and buccinator (mouth)
What are facial expressions innervated by?
Facial expressions are innervated by the facial nerve - damage like lesions cause drooping like Bell’s palsy
LABEL the muscles of mastication
1) temporalis, masseter, medial pterygoid, and lateral pterygoid.
What is the temporomandibular joint? (TMJ)
Both TMJs form a single bilateral articulation
What is the classification of the temporomandibular?
Synovial, modified (gliding and hinge)- functional: uniaxial diarthrosis
Why is the temporomandibular modified?
Modified because the fibrocartilaginous articular disc separates the mandibular fossa and the condyle of the mandible
LABEL the extrinsic muscles of the eye
- superior rectus, lateral rectus, inferior oblique, superior oblique, medial rectus and inferior rectus
What do the extrinsic muscles of the eye do?
they control the position of the eye
What do muscles of the tongue do?
it positions and shapes the tongue for speech, mastication and swallowing.
What do the pharynx and larynx do?
Swallowing, speech (voice box)
LABEL the muscles of the anterior neck?
pp
What do the muscles of the anterior neck do?
move the head and neck (the sternocleidomastoid) (SCM), support the floor of the mouth and are the extrinsic muscles of the larynx 1) Elevators (suprahyoid) and 2) depressors (infrahyoid)
What actions do the sternocleidomastoid do?
unilateral action, lateral flexion and contralateral rotation
- bilateral action (upper cervical extent) and lower cervical flexion (waking up and lifting your head off the pillow)
What actions do the suboccipital muscles do?
Bilaterally: head extension
Unilaterally: ipsilateral rotation and lateral flexion
LABEL the muscles of the vert. column (erector spinae)
1) Illocostalis
2) Longissimus
3) Spinalis
What action do the bilateral and unilateral muscles of the vert. column?
Bilateral action: extension
unilateral action: lateral flexion
What are the transversospinales group and what do they do?
Rotatores, multifidus, and semispinalis - they attach to the transverse and spinous processes BILATERAL ACTION: extension
what are the segmental muscles?
interspinales and intertransversales (proprioceptive)- position in space
Label the muscles of the vertebral column
pp
Label the muscles in the thorax?
To complete the thoracic wall 3 layers of intercostals (between ribs) 1. External intercostals inspiration 2. Internal intercostals expiration 3. Innermost intercostals
Label the muscles in the abdominal wall and their actions
pp - posterior, lateral and anterior
Label the muscles in the pelvic wall and their actions
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What are tropomyosin and troponin?
Tropomyosin blocks myosin binding sites on actin molecules, preventing cross-bridge formation, which prevents contraction in a muscle without nervous input. The protein complex troponin binds to tropomyosin, helping to position it on the actin molecule.
