MUSCLES

3 Types

• Skeletal-striated/voluntary• Smooth- involuntary• Cardiac-heart, involuntary

Skeletal

Smooth

Cardiac

Skeletal Muscle Components

Skeletal muscle - numerous nuclei and mitochondria

Fascia- dense CT, surrounds each muscle/separates- Tendon- cordlike, connects to bone- Aponeuroses- CT that connects bone

- broad, fibrous sheets

CT

• Epimysium – outermost layer, surrounds entire muscle

• Perimysium – separated and surrounds the FASCICLES -(bundles) of muscle fibers

• Endomysium – surrounds each individual muscle fiber

• Many layers= ability to move independently, allows blood vessels and nerves to pass through

Draw

• Sarcolemma- muscle fiber membrane• Sarcoplasm- inner fluid, cytoplasm• Myofibrils- indiv muscle fibers made of

myofilaments within the sarcoplasm

Draw

• MYOFILAMENTS.two types:

MYOSIN – thick filaments, two twisted proteins strands, globular parts (cross bridges)ACTIN – thin filaments, double strands in helix

• These filaments overlap to form dark and light bands on the muscle fiber

– A band = dArk • thick (myosin)– I band = lIght • thIn (actin)

• In the middle of each I band are Z lines. A sarcomere is one Z line to the other

• arrangement of sarcomeres next to each other produces the STRIATIONS

• Sarcoplasmic Reticulum–network of membranous channels surrounding myofibril

• Transverse tubules (T tubules) – extend from sacroplasmic reticulum into sacrolemma.

• Cristernae- 2 tubes surrounding T tubes

Hierarchy of muscle parts

Muscles and Nervous System

• Muscle contraction- movement of myofibrils: actin & myosin slide past one another, shortening sacromeres

• Muscle fibers shortens - pulls attachments

• Neuron- • Axon- extends / capable of conducting nerve impulse

• Motor Neuron- control skeletal muscles

Synapse

• Synapse- Space which info passes• Neurotransmitters- chemicals released into

synapse• Neuromuscular junction- site where axon and

muscle fiber meet- forms motor end plate– Nuceli/mitochondria abundant & sarcolemma is

folded

• Synaptic cleft- separates neuron membrane and membrane of muscle fiber

Steps for Contraction

1. Acetylcholine (Ach) –(neurotransmitter) released from end neuron

2. It diffuses across the gap to the muscle fiber3. Muscle fiber is stimulated-impulse travels

across fiber & into T tubules

4. Impulse reaches sarcoplasmic reticulum5. Calcium ions are released6. Cause linkages between actin and myosin7. Actin filaments slide across the myosin8. Muscle fiber shortenshttp://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter42/animations.html#

Sliding filament Theory

The movement of the actin filaments over the myosin causes shortening of fiber

• http://entochem.tamu.edu/MuscleStrucContractswf/index.html

Fiber Relaxation

1. Cholinesterase is released2. Inhibits acetylcholine3. No muscle stimulation4. Calcium ions reabsorbed into S.R5. Actin returns to normal position6. Muscle fiber relaxes

http://www.blackwellpublishing.com/matthews/myosin.html