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Functions
- Movement of the body (skeletal muscles).
- Maintenance of posture (erector spinae).
- Respiration (diaphragm & accessory muscles).
- Production of body heat (shivering).
- Communication (gap junctions in cardiac muscles).
- Constriction of organs and vessels (smooth muscles).
- Contraction of the heart (cardiac muscle).
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Contractility
shorten with force
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Skeletal Muscle
- Yes-Striations.
- Cylindrical and very long.
- Single: centrally located.
- Involuntary and Voluntary.
- Infraspinatus
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Cardiac Muscle
- Yes-Striations.
- Cylindrical and branched.
- Single; centrally located.
- Involuntary.
- Heart.
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Smooth Muscle
- No Striations.
- Spindle-shaped.
- Single; centrally located.
- Involuntary.
- Walls of hollow organs, blood vessels, eyes, glands, and skin.
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Endomysium
Surrounds muscle single fibers.
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Perimysium
Surrounds fasciculi or fascicle.
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Epimysium
Surrounds whole muscles (many fascicles).
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Fascia
Surrounds individual muscles and groups of muscles.
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Neuromuscular Junction (NMJ)
- Junction (synapse) between nerve and muscle.
- 1. Synapse: Muscle, organ, and gland create a synapse.
- 2. Presynaptic membrane: belongs to neuron.
- 3. Postypnaptic membrane: belongs to muscle cell.
- 4. Synaptic cleft: space or gap.
- 5. Neurotransmitter (Acetylcholine - ACh) - Ligand chemical.
- 6. Acetylcholinesterase (AChE): breaks ACh to not allow receptors to bind anymore:
- Acetic Acid
- Choline
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Thick myofilament
Made up of one protein: Myosin (head).
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Thin myofilament (3 proteins)
- Made up of three proteins:
- 1. Actin: G-actin - monomer; contains binding site for myosin head.
- 2. Tropomyosin
- 3. Troponin
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Tropomyosin
Block myosin binding site on G-actin.
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Troponin
- Binds tropomyosin
- Binds Calcium
- Binds G-actin
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Sarcomere
- Most basic functional unit. Z disk to Z disk. dArk and lIght bands of a skeletal muscle cell. A-band: M-line and H-zone.
- I-band: Z-disk and thin filaments.
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How many forms of actin do you have?
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Which actin is going to bind site for myosin head to form "cross-bridge"?
G-actine
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Cardiac & skeletal muscles cells; calcium is going to bind to which protein?
Troponin
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Smooth muscle cells; calcium is going to bind to a protein known as?
Coagulate.
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Z-Disk
- Allow attachment of thin (actin) myofilament.
- Allow attachment of thick (myosin) myofilament via thin filament.
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M-line
Holds the thick (myosin) myofilament in place at the center.
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Alternating A band and I band are?
Muscle Striations
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H zone
A region where only thick (myosin rods) myofilaments are found.
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A band
- Contain M line and H Zone.
- Span the entire length of the thick (myosin) myofilament.
- Certain regions contain both thick and thin myofilaments.
- Consists of the dar band of alternating dark and light striation of striated muscles.
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I band
- Contain Z-disk and thin (actin) myofilaments only.
- Consist of the light band of alternating dark and light. Striation of striated muscles.
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Sliding Filament Model
- 1. An action potential travels down motor neuron to presynaptic terminal causing Ca2+ channels to open. These Ca2+
- channels are voltage-gated channels.
- 2. Ca2+ causes synaptic vesicles to release acetylcholine (Ach) into synaptic cleft. Acetylcholinesterase (ACh-E) resign in
- the synaptic cleft and can degrade ACh before it reaches the postsynapatic membrane.
- 3. Acetylcholine binds to receptor sites on Na+ channels (ligand-gated) on the postsynaptic membrane (sarcolemma).
- 4. Na+ channels open, and Na+ rushes into postsynaptic terminal (depolarization). This cause an action potential in the
- postsynaptic membrane (muscle). Action potential travels to T-tubules (contains voltage-gated Ca2+ channels).
- 5. This causes the release of stored Ca2+ from the sarcoplasmic reticulum and terminal cisterna of the muscle cell.
- 6. This Ca2+ binds to troponin (skeletal & cardiac), calmodulin (smooth)
- 7. Ca2+ binding to troponin causes tropomyosin to move exposing G-actin (contains myosin binding site).
- 8. Myosin heads bind to G-actin (formation of cross-bridge).
- 9. Myosin heads bend toward center of sarcomere (power-stroke).
- 10. ATP is used to release the myosin head from the G-actin.
- 11. This pattern cycle to form a muscle contraction.
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Ligand-gated channel (ACh)
A channel that responds to ligand chemical.
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Voltage-gated channel
- Action potential.
- Open and close in response to a small voltage change across the plasma membrane (brought on by an action potential that recahed it).
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Resting membrane potential
Cell at rest (no stimuli).
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Threshold
Minimum amount of energy.
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Depolarization
Up stroke of action potential. Intake of Sodium (Na+).
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Repolarization
Down stroke of action potential. Release of Potasium (K+ ions).
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Hyperpolarization
- Below minimum value. Overshoot of the re-polarization phase.
- Returning to Resting Membrane potential; Na+/K+ pump (3Na+ back out and 2K+ in).
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Sarcolemma
Cell membrane of a muscle cell.
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Sarcoplasmic reticulum
Store and release calcium.
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Sarcoplasm
Cytoplasm of a muscle cell.
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Muscle Twitch or Contraction
- Muscle contraction in response to a stimulus that causes action potential in one or more muscle fibers.
- Lag or latent
- Contraction
- Relaxation
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Lag or latent
- Begins with stimulation of a muscle that last about 2 milliseconds
- – Action potential sweeps across the sarcolemma and sarcoplasmic reticulum to release stored Ca2+.
- – No tension is produced at this time.
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Contraction
- This phase last about 15 milliseconds.
- – Ca2+ binds to troponin exposing myosin-binding site on
- G-actin and cross-bridge interactions are occurring.
- – Power-stroke.
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Relaxation
- – This phase last about 25 milliseconds.
- – Ca2+ level is falling
- – Myosin-binding sites on Actin are cover by Tropomyosin
- – Decrease number of cross-bridge (presence of ATP)
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Muscle contraction
- 1. Isometric: no change in length.
- 2. Isotonic Contraction:
- Concentric: Muscle shortens (flexibility)
- Eccentric: Muscle lengthens (control release of dumbbells).
- 3. Muscle tone: constant tension by muscles for long periods of time.
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Energy Sources
- Creatine phosphate (CP): 10 seconds
- Anaerobic respiration: Up to 3 minutes.
- Aerobic respiration: Hours.
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Nomenclature
- 1. Location: pectoralis, gluteus, brachial, femoral
- 2. Size: maximus, minimus, longus, brevis
- 3. Shape: deltoid, quadratus, teres, trapezius
- 4. Orientation: rectus, oblique
- 5. Origin and insertion: sternocleidomastoid,
- brachioradialis
- 6. Number of heads: biceps, triceps, quadriceps
- 7. Function: abductor, adductor, masseter
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Classes of Levers
- Class I
- Fulcrum (point of pivot) between
- force (P) and weight (W)
- – Seesaw
- – Head movement at the atlantooccipital
- joint
- Class II
- Weight is between fulcrum and pull
- – Wheelbarrow
- – Standing on toes;
- metatarsophalangeal joint
- Class III
- Pull located between fulcrum and
- weight
- – Person using a shovel
- – Most common: biceps brachii with
- elbow as fulcrum
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Muscles of facial expression
- Frontalis: Raises eyebrow and wrinkles forehead. Facial n.
- Occipitalis: Tenses and retracts scalp. Facial n.
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Orbital Region
Orbicularis oculi: Closes eye. Facial n.
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Oral Region
- Orbicularis oris: Closes lip. Facial n.
- Levator labii superioris alaeque nasi: Elevates ala of nose and upper lip. Facial n.
- Levator labii superioris: Elevates upper lip. Facial n.
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Muscles of mastication
- Masseter: Elevates mandible. Trigenimal n. (V3).
- Temporalis: Elevates and retracts mandible. Trigenimal n. (V3).
- Medial pterygoid: Elevates mandible and side-to-side action with lat. pterygoid. Trigenimal n. (V3).
- Lateral pterygoid: Depresses and protracts mandible. Trigenimal n. (V3).
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Muscles that move the eyeball (extraocular muscles)
- Superior rectus: Elevates eyeball. Oculomotor n. (AL3).
- Inferior rectus: Dpresses eyeball. Oculomotor n. (AL3).
- Lateral rectus: Laterally rotates eyeball. Abducens n. (LR6).
- Medial rectus: Medially rotates eyeball. Oculomotor (AL3).
- Inferior oblique: Elevates eye in adduction. Laterally rotates eye in abduction. Occulomotor n. (AL3).
- Superior oblique: Depresses eye in adduction. Medially rotates eye in abduction. Trochlear n. (SO4).
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Anterior muscles of the neck (suprahyoid)
- Digastric (anterior belly): Depresses mandible and elevates hyoid bone.
- Digastric (posterior belly): Depresses mandible and elevates hyoid bone.
- Stylohyoid: Elevates hyoid bone. Origin; sytloid process. Insertion; hyoid bone (greater cornu).
- Mylohyoid: Elevates floor of mouth and tongue; depresses mandible.
- Geniohyoid: Protracts hyoid bone, depresses mandible.
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Anterior muscles of the neck (infrahyoid)
- Omohyoid (superior belly and inferior belly): Origin, superior border of scapula. Insertion; hyoid bone. Ansa cervicalis n.
- Sternohyoid: Origin; manubrium and clavicle (medial end). Insertion; hyoid bone. Ansa cervicalis n.
- Sternothyroid: Origin; Manubrium and 1st coastal catrilage. Insertion; thryoid cartilage. Ansa cervicalis n.
- Thryrohyoid: Origin; thryroid cartilage. Insertion; hyoid bone. Hypoglossal n.
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Anterolateral muscles of the neck
- Sternocleidomastoid: Origin; manubrium and clavicle (medial). Insertion; mastoid process.
- Together they flex head.
- Alone turns head to the contralateral aspect.
- Accessory n.
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Muscles of the abdomen
- Medial:
- Rectus abdominis
- Lateral:
- External abdominal oblique
- Internal abdominal oblique
- Transversus abdominis
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Erector Spinae - Spinalis Group
- Spinanlis cervicis (not shown)
- Spinalis thoracis
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Erector Spinae - Longissimus Group
- Longissimus capitis
- Longissimus cervicis
- Longissimus thoracis
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Erector Spinae - Iliocostalis Group
- Iliocostalis cervicis
- Iliocostalis thoracis
- Iliocostalis lumborum
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Semispinalis Group
- Semispinalis capitis
- Semispinalis cervicis
- Semispinalis thoracis
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Muscles of the perineum
- Ischiocavernosus
- Bulbospongiosus
- Superficial transverse perineal
- Deep Transverse perineal
- Levator ani
- External anal sphincter
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Muscles of the thenar (thumb) eminence
- Opponens pollicis
- Abductor pollicis brevis
- Flexor pollicis brevis
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Adductor of the thumb
Adductor pollicis
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Muscles of the hypothenar (pinky) eminence
- Abductor digiti minimi
- Flexor digiti minimi brevis
- Opponens digiti minimi
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Posterior muscles that move the arm
Teres major
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Muscles of the rotator cuff
- Subscapularis
- Infraspinatus
- Supraspinatus
- Teres minor
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Which group is not part of the errector spinalis?
Semispinalis
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