Muscular System Post Lab

8/4/2019 Muscular System Post Lab

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Exercise 10

Muscular System



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



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



• Striated and multinucleated

• Attached to skeleton

• Voluntary

• Contracts powerfully and

quickly but fatigues morerapidly than smooth andcardiac muscles

Skeletal Muscle



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.



• 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



Ultrastructure

of a SkeletalMuscle



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.



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



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



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



• 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





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)



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



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



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



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



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



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



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



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


Transversusabdominis

Dorsal fascia, ilium andtransverse processesof the vertebral column

Aponeuroses on thelinea alba




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



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



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



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



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



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




• 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)




• 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



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.

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Muscular System Post Lab

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