Muscular System Post Lab
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Transcript of Muscular System Post Lab
8/4/2019 Muscular System Post Lab
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Exercise 10
Muscular System
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Functions of the Muscular System
• Produce movement
– Muscle pulls tendons to move the skeleton
• Maintain posture and body position
– Continuous muscle contraction
• Support soft tissue
– Support weight of visceral organs
• Maintain body temperature
– Energy from contraction is converted to heat
• Involuntary contraction of blood vessels
– Produce blood pressure and pump blood
• Involuntary contraction of the walls of visceral organs and theirpassages
– Peristalsis moves the food from the mouth down to the rest of thedigestive tract
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Properties of muscle tissues1. Contractility – shorten
2. Excitability – respond to stimuli
3. Extensibility – stretch
4. Elasticity –
return to original state
Three types of muscle tissues
1. Skeletal – striated; voluntary
2. Cardiac – striated; involuntary
3. Smooth – unstriated; involuntary
Muscular Movement
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• Striated and multinucleated
• Attached to skeleton
• Voluntary
• Contracts powerfully and
quickly but fatigues morerapidly than smooth andcardiac muscles
Skeletal Muscle
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Cardiac Muscle
• Muscle fibers in the walls of the
heart
• Striated, branching cells withsingle nucleus; connected byintercalated discs
• The contraction of the whole heartis caused by the action potentialgenerated in one part of the heartthen spread to all the cardiacmuscle cells.
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• Non-striated
• actin & myosin filaments are notregularly arranged
• Each fiber has single nucleus
•Responsible for the involuntaryperistalsis of the vessels and walls ofvisceral organs
• Contracts slowly but can sustain
prolonged contractions and does notfatigue easily
Smooth Muscle
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Ultrastructure
of a SkeletalMuscle
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Myofibrils
• Each muscle fiber contains100 to 1000 or moremyofibrils.
• Consist of thick (myosin) andthin filaments (actin) aligned
in contractile units calledsarcomeres.
• The arrangement of thick andthin filaments appears as
alternating light and darkbands, thus the striation ofthe whole muscle fibers.
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Sarcomere
•
Each myofibril contains10,000 sarcomeres end toend.
• Interaction between thick andthin filaments cause
contraction
• M line – connection between thethick myosin filaments
• H zone – the central zone in the
relaxed sarcomere containing onlymyosin filaments
• Z line – the dark stripe in thecenter of the I band (bulkhead)
• Isotropic (I) band – zone around
the Z line that contains only actinfilaments
• Anisotropic (A) band – marks theextent of the myosin filaments inthe sarcomere
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Actin and Myosin
• Actin
–
Twisted actin molecules – Has resting site - covered by
tropomyosin which is held inplace by troponin
– Has active site – exposed site
where myosin interacts withactin
• Myosin
– Head attaches to the active siteof actin during contraction
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Sliding-Filament Model of MuscleContraction
• Myosin head attaches to active site on actin (cross bridge), pulls actin towards center, thendetaches
• Actin filaments slide toward the center of sarcomere while the myosin filaments remainstationary
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• Muscle contractions require energy• Blood vessels deliver oxygen and nutrients to
produce ATP
• Muscle contractions are under stimulation from the centralnervous system (CNS)
• Voluntary control
• Axons connect to individual muscle fibers
Control of Skeletal Muscle Contraction
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Control of Skeletal Muscle Contraction at theNeuromuscular Junction
1. Action potential travels to axon of motor neuron2. Neurotransmitter acetylcholine (Ach) is released into
synaptic cleft
3. Ach diffuses across synaptic cleft & binds to Ach
receptors on sarcolemma1. This changes permeability to sodium
2. Sudden rush of sodium into sarcolemma
3. Causes action potential in sarcolemma
4. Action potential spreads over entire sarcolemma, downt-tubules to cisternae
5. Cisternae release massive amounts of calcium
6. Increase in calcium – sarcomeres contract
7. Ach broken down by acetylcholinesterase (AchE)
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Calcium-Induced Formation of Cross-bridgesbetween Actin and Myosin
•
Step 3 – Pulling of cross-bridge
towards center ofsarcomere
– ADP + P released
(energy used)• Step 4
– Myosin head bindsanother ATP
– Detachment of cross
bridge• Step 5
– ATP ADP + P,reactivation of myosinhead
• Resting sarcomere
– ATP (stored energy) attaches
to myosin head• Step 1
– Ca+ binds to troponin exposingactive site on actin
• Step 2
– Myosin head attaches to actin
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Antagonistic Muscles
Antagonistic muscles contract
opposite to each other.
Examples in frogs
1. Temporalis: levator of the mandible
Depressor mandibulae: depressorof the mandible
2. Sternoradialis: flexor of the forearm
Triceps brachii: extensor of theforearm
3. Biceps femoris: flexor of the leg
Triceps femoris: extensor of the leg
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Synergistic Muscles
•
Synergistic muscles contract together to produce the samemovement.
• Examples in frogs:
1. Anterior pectoralis
Middle pectoralis adductor and rotator of the armPosterior pectoralis
2. Rectus abdominis
External oblique constrictor of the abdomen
Transversus abdominis
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Parts of a Muscle
• Origin – proximal point ofattachment; does not move when the
muscle contracts
• Insertion – distal point of attachment;moves when the muscle contracts
• Belly – muscle mass between theorigin and insertion
• Heads – for muscles with more than1 point of origin
• Biceps – muscles with twoheads
•
Triceps –
muscles with threeheads
• Slips – for muscles with more than 1point of insertion
OB
I
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Dorsal muscles of the head and trunk
Muscle Origin Insertion Function
Temporalis Median dorsal line of theskull
Posterior portion of thelower jaw
Levator of themandible; constrictor of
the mouth
Depressormandibulae
Tough fascia in themiddorsal line
Lower jaw Depressor of the jaw
Dorsalis scapulae Dorsal surface of thesuprascapula andscapula
Side of the humerus Abductor of the arm
Latissimus dorsi Lumbodorsal fascia Side of the proximal end ofthe humerus
Draw limbs upward andbackward
Longissimus dorsi Anterior third of theurostyle and skull
Along the vertebral column Extensor of the back;levator of the head
Iliolumbaris Anterior portion of theilium
Transverse processes ofthe vertebral column
Flexor of the back
Coccygeo-sacralis Lateral anterior half ofthe urostyle
Transverse processes ofthe sacral vertebrae
Draws the back andurostyle closer to eachother
Coccygeo-iliacus Side of the posterior halfof the urostyle
Ilium
Extensor of the back;fixes the urostyle withrespect to the pelvic
girdle
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Ventral muscles of the head Muscle Origin Insertion Function
Mylohyoid Central surface of themandible
Median raphe
Levator of the floor ofthe mouth duringbreathing andswallowing
Submentalis Anterior edge of thelower jaw
Anterior angle of themandible
Levator of the tip of themandible; constrictorof the external nares
Geniohyoid Anterior angle of themandible
Posterior horn and thyroidprocesses of the hyoidapparatus
Draws the hyoidforward and upward
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Pectoral and chest muscles Muscle Origin Insertion Function
Cutaneouspectoralis
Posterior pectoralis andanterior third of therectus abdominis
Skin at the pectoral region Draws the skin caudad
Anterior pectoralis(Pectoralis
epicoracoidea)
Epicoracoid Deltoid ridge Adductor and rotator of
the arm
Middle pectoralis(Pectoralis sternalis)
Mesosternum andxiphisternum
Ventral portion of theproximal end of thehumerus
Adductor and rotator ofthe arm
Posterior pectoralis(Pectoralisabdominis)
Median surface of thetrunk
Deltoid ridge Adductor and rotator ofthe arm
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Abdominal muscles Muscle Origin Insertion Function
Rectus abdominis Antero-ventral surfaceof the pelvic girdle
Posterior half of thesternum
Constrictor of theabdomen
External oblique Dorsal fascia and ilium Aponeuroses on thelinea alba
Constrictor of theabdomen
Transversusabdominis
Dorsal fascia, ilium andtransverse processesof the vertebral column
Aponeuroses on thelinea alba
Constrictor of theabdomen
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Muscles of the forearmMuscle Origin Insertion Function
Sternoradialis Episternum andomosternum
Proximal end of the radius Flexor of the forearm
Scapulohumeralis(deltoid)
Scapula Deltoid ridge Adductor andprotractor of the
forearm
Triceps brachii Base of the scapula andshaft of the humerus
Proximal end of the radio-ulna
Extensor of theforearm
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Dorsal muscles of the thigh Muscle Origin Insertion Function
Triceps femoris Ilium and acetabulum Proximal end of the tibio-fibula
Abductor of the thigh;extensor of the leg
Gluteus Crest of the ilium Proximal end of the femur Rotator of the femur
Biceps femoris(iliofibularis)
Dorsal side of the ilium Proximal end of the tibio-fibula
Flexor of the leg;extensor of the thigh
Semimembranosus Dorsal part of theischium
Back of the head of thetibio-fibula
Flexor or extensor ofthe leg or adductor ofthe thigh
Pyriformis Posterior edge of theurostyle
Proximal end of the femurPulls the urostyle;draws the femurdorsally
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Ventral muscles of the thigh Muscle Origin Insertion Function
Adductor longus Ventral part of the ilium (Fused with adductormagnus)
Pulls the thighventrally and forward
Adductor magnus Pubis, ischium Distal end of the femur Adductor of the thighand leg; draws thethigh ventrally
Gracilis major(Rectus internusmajor)
Posterior edge of theischium
Proximal end of the tibio-fibula
Adductor or extensorof the thigh; flexor orextensor of the shank
Gracilis minor(Rectus internusminor)
Posterior part of theischiac symphysis
Proximal end of the tibio-fibula
Adductor and extensorof the shank
Semitendinosus Ischium Proximal end of the tibio-
fibula
Adductor of the thigh;
flexor of the leg
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Dorsal muscles of the shank
Muscle Origin Insertion Function
Gastrocnemius Distal end of the femur Tendon of Achilles Flexor of the shank;extensor of the foot
Peroneus Distal end of the femur Lower end of the tibio-fibula and proximal end ofthe tarsals
Flexor and extensor ofthe foot; extensor ofthe leg
Tibialis anticus Distal end of the femur Proximal ends of thetarsals
Flexor of the foot;extensor of the leg
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Ventral muscles of the shank Muscle Origin Insertion Function
Tibialis posticus Proximal end of thetibio-fibula
Proximal end of theastragalus
Flexor or extensor ofthe foot
Extensor cruris Distal end of the femur Anterior surface of theproximal half of the tibio-fibula
Extensor of the shank
Flexor tarsi anterior Anterior surface of thecenter; distal half of thetibio-fibula
Proximal end of th tibialeand foot fascia
Flexor of the foot
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Tendon
–
fibrous connective tissue (cord) that attaches musclesto bones
Ligament
– also a fibrous connective tissue (cord) that attachesbones to bones
Connective Tissues Associated with Muscles
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Connective Tissues Associated with Muscles
• Fascia
• Soft connective tissue that covers and protects exposedsurfaces of muscles, organs and other structures
• Acts as shock absorber of the underlying muscles andstructures; helps facilitate tissue repair during an injury
• Three types:
» Superficial fascia – subcutaneous; blending withthe dermis
» Deep fascia - surrounds the muscles
» Visceral fascia – surrounds the internal organs
(pericardium covers the heart; peritoneum coversmost of the internal organs)
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Connective Tissues Associated with Muscles
• Aponeuroses
• flattened or ribbon-shaped tendons whichare very sparinglysupplied with blood
vessels and nerves• function as the insertion
sites of muscle fibers andtherefore cover asubstantial portion of the
muscle belly
• Inscriptions
• segments that interrupt the longitudinal muscle fibers ofrectus abdominis
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Epaxial and Hypaxial Muscles• Epaxial muscles
• Mass of trunk muscles dorsal to the horizontal myoseptum
• Include muscles associated with the vertebrae, ribs, andbase of the skull
• Hypaxial muscles
• Mass of trunk muscles ventral to the horizontal myoseptum
• Include the diaphragm, the abdominal muscles, and all limbmuscles
• Horizontal myoseptum separates epaxial and hypaxial muscles.