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MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

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MUSCLE TISSUE
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Page 1: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

MUSCLE TISSUE

Page 2: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

MUSCLE TISSUEA primary tissue type, divided into:

skeletal musclecardiac musclesmooth muscle

Page 3: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

Connective Tissue Organization

1. Epimysium• Exterior collagen layer• Surrounds entire muscle• Separates muscle from surrounding tissues2. PerimysiumSurrounds muscle fiber bundles (fascicles)Contains blood vessel and nerve supply to fascicles

Page 4: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

3. EndomysiumSurrounds individual muscle cells (muscle fibers)Contains capillaries and nerve fibers contacting

muscle cellsContains satellite cells (stem cells) that repair

damageEndomysium, perimysium, and epimysium come together

at ends of muscles to form connective tissue attachment to bone matrix i.e., tendon.

Page 5: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

Structure of Skeletal Muscle

Page 6: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

Structure of Skeletal Muscle

Page 7: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

SKELETAL MUSCLE CELL- Striated/striped appearance of skeletal muscle cell is due

to the orderly arrangement of the thin and thick filaments .

that makeup the majority of the contractile proteins.- The contractile proteins are made of 3 types of

filaments;1. THIN FILAMENT2. THICK FILAMENT3. ELASTIC FILAMENT

Page 8: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

CONTRACTILE PROTEINS1. THIN FILAMENTThin filament is placed hexagonally around myosinMake and break contacts with myosin during

contractionHas 3 parts;

i) ACTIN PROTEIN (i.e. the main molecule of this filament). FUNCTION: Binds to myosin head.

Page 9: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

CONTRACTILE PROTEINSii) TROPONIN

FUNCTION: Regulatory function by binding to Ca 2+

iii) TROPOMYOSIN FUNCTION: Has a regulatory function by blocking/unblockingthe binding site of actin to the myosin head

Page 10: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

CONTRACTILE PROTEINS

2. THICK FILAMENT

Thick filament: composed of structural protein, myosin.

- has 2 main parts i) Myosin head - possesses actin binding site and ATPase activity.

ii) Myosin tail– forms the shaft of thick bands.

Page 11: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

CONTRACTILE PROTEINS3. ELASTIC FILAMENT

– made of titin molecule FUNCTION: – Fixes the thick filament to a z disc.

Page 12: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

Muscle SarcomereSarcomere - functional unit of muscle cellConsist of thick and thin filaments –

myofilaments/ myofibrilMyofilaments that lies between two ‘z’ lines-

sarcomere- Dark & light bands alternate- Light I band is Isotropic- Dark A band is anisotropic- Z line bisects I band- H zone: No overlap of actin

Page 13: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

MyofibrilsEach myofibril consists of two types of protein

filaments -"thick filaments", and "thin filaments". Thick filaments and the thin filaments within

myofibrils overlap in a structured way, forming units called sarcomeres.

Sarcomeres are sections of myofibril that are separated from each other by areas of dense material called "Z discs".The sarcomeres are also described in terms of the bands/zones within which one or both of the two filaments occur.

Page 14: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

• The "A band" is a relatively darker area within the

sarcomere that extends along the total length of the thick

filaments.• The "H zone" is at the centre of the A band of

each sarcomere. As shown below, this is the region in which there are only thick filaments, and no thin filaments.The "I band" is the region between adjacent A bands, in which there are only thin filaments, and no thick filaments. ( Each I band extends across two adjacent sarcomeres.)

Page 15: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.
Page 16: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

Arrangement of Filaments

Page 17: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

Cross Bridge

Page 18: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

Muscle contraction [SLIDING FILAMENT THEORY]

Involves the sliding of the actin over the myosin which causes the muscle to shorten and therefore develop tension

The process of muscular contraction can be explained by the sliding filament theory

Page 19: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

Muscle contraction [SLIDING FILAMENT THEORY]

Excitation: Step 1Action potential (AP) travels to nerve endingACh release at the neuromuscular junctionActivation of receptors by AChVoltage gated Na channels openAP is generated in the muscle fiber

Page 20: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

Muscle contractionDepolarization of sarcolemmaAction potential transmitted down T-tubuleSarcoplasmic reticulum releases Ca++ Ca++ binds to troponin CActive actin site is exposed

Page 21: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

Muscle contractionContraction: Step 2

1. Myosin heads are activated Myosin head hydrolyses (breakdown) ATP to release energy

Myosin head gains energy so it becomes activated. Activated myosin head is ready to bind with actin filament (cross bridge)

Page 22: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

Muscle contraction2. Activated myosin head binds rapidly to myosin-

binding sites on actin3. Myosin head still bonded to actin;

i) Changes its shapeii) Moves towards the center of sarcomere

Above steps, i) and ii) called power stroke4. Myosin head is still bonded to actin

Page 23: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

Muscle contraction5. ATP binds to the myosin in the myosin-actin complex6. Myosin head detaches from actin7. Myosin head hydrolyses ATP to release energy.8. Steps 2 – steps 8 is repeated• During muscle contraction the thin actin filaments

slide over the thick myosin filament.• This results in a reduction in the distance from Z line

to Z line• H zone increases while while I band decreases.

Page 24: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.
Page 25: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

The Sliding Filament Model of Muscle Contraction

Page 26: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

Muscle contractionRelaxation: Step III• Ca++ is pumped back to sarcoplasmic

reticulum• Active pump utilizing ATP• Actin sites are covered by troponin• Ca++ remains stored in the reticulum

Page 27: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

NEUROMUSCULAR JUNCTION Each muscle fibre is connected to a nerve fibre

branch coming from a nerve cell.These nerve cells are called motor neurons, and

extend outward from the spinal cordThe motor neuron and all the muscle fibres it

innervates are called a motor unit.Stimulation from motor neurons initiates the

contraction process.The site at which motor neuron attaches on the

muscle cell is known as the neuromuscular junction

Page 28: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.
Page 29: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

NEUROMUSCULAR JUNCTIONAt this junction, the sarcolemma forms a pocket

known as the motor end plateThe end of the motor neuron is not in direct

contact with the muscle fibre but is separated by a short gap known as the neuromuscular cleft

A nerve impulse reaching the end of the motor nerve stimulates the release of the neurotransmitter acetylcholine which diffuses across the synaptic cleft and binds to the receptor sites on the motor end plate

Page 30: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.
Page 31: MUSCLE TISSUE. A primary tissue type, divided into: skeletal muscle cardiac muscle smooth muscle.

NEUROMUSCULAR JUNCTIONThis causes an increase in permeability of

sarcolemma to sodium and sodium diffuses into muscle fibre resulting in a depolarisation called the end-plate potential (EPP)

This EPP is usually large enough to exceed the threshold that is the signal to start the contractile process.


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