File - Mr. Jacobson`s Site

Muscular System Chapter 8

Introduction • All movements require muscles • They are specialized cells that use chemical energy to contract • They provide muscle tone, propel body fluids and food, generate the heartbeat and distribute heat • Three types: skeletal, smooth and cardiac • We will just talk about skeletal this chapter

http://t1.gstatic.com/images?q=tbn:ANd9GcRBgTwo0pCWijCpU1047_hoBesy-Wf8REPi0R4jROH1aRnGTyu4

Structure of a Skeletal Muscle • It is composed of skeletal muscle tissue, nervous tissue, blood, and connective tissue •

Muscles > Fascicles > Muscle fiber (cells) > Myofibrils > Thick and thin filaments

Structure of Skeletal muscle: Connective tissue coverings • A muscle is covered by layers of fibrous connective tissue called a fascia • It may project longer than the muscle and form a tendon by connecting to the bone • Sometimes they form aponeuroses which are sheets that connect to adjacent muscles

http://www.guwsmedical.info/blood-vessels/images/4518_264_558-aponeuroses.jpg

• All parts of a skeletal muscle are enclosed in layers of connective tissue which form a network • Epimyseum > perimyseum > fasicles > endomyseum • All of those are connective tissues

Structure of Skeletal Muscle: Skeletal Muscle Fibers • SMF is a single cell that contracts in response to stimulation and then relaxes when stimulation ends (may extend full length of muscle) • The sacroplasm (cytoplasm) contains many threadlike myofibrils that lie parallel to one another

SMF & Myofibril

http://211.174.114.20/catalog/2011%5C2011_08/actinx2.jpg

• Myofibrils aid in muscle contraction and contain 2 types of protein filaments: – Myosin- thick muscle filaments – Actin- thin muscle filaments

• These alternating bands cause the striations

http://www.sport-fitness-advisor.com/images/actin_myosin.jpg

• 2 main parts to striations: – I bands are composed of actin (thin/light) directly attached to z lines – A bands are composed of myosin (thick/dark) that overlap the thin filaments • In the center of the A band is the H zone which is a central region that has the M line inside • The segment of a myofibril that extends from one z line to the next is called a sacromere

http://site.motifolio.com/images/Arrangement-of-myofilaments-in-the-sarcomere-relaxed-state-9111135.png

http://apbrwww5.apsu.edu/thompsonj/Anatomy%20&%20Physiology/2010/2010%20Exam%20Reviews/Exam%203%20Review/09-03bc_skelemusfi_1.jpg

• Sacroplasmic reticulum – Membranous network of channels and tubules (similar to ER) • Transverse tubules – Membranous channel that extends inward from a muscle fiber membrane and passes through the fiber

• These two structures activate muscle contraction when fiber is stimulated

Neuromuscular Junction • Each SMF connects to an axon from a nerve cell, called a motor neuron • Muscle fiber contracts only when stimulated by neuron • Neuromuscular junction – connection between the motor neuron and muscle fiber

http://www.biologycorner.com/anatomy/muscles/muscle_images/neuromuscular_junction.jpg

• The muscle fiber forms a motor end plate • The end of the motor neuron has many vesicles that contain chemicals called neurotransmitter (acetocholine) • A nerve impulse travels to the neuron which releases some of the neurotransmitters into the gap which stimulates the muscle fiber to contract

http://4.bp.blogspot.com/-gmzOZ8xvH1w/UF7d_9n7P8I/AAAAAAAAACE/FDmkFYMAEnY/s1600/neuromuscular-junction.jpg

Motor Units • One motor neuron may connect to many muscle fibers because they are branched • When one impulse is sent it stimulates all of the muscle fibers that the motor neuron is connected to • A motor neuron and the muscle fibers that is controls make up a motor unit

Motor Unit

http://staff.fcps.net/cverdecc/adv%20a&p/notes/muscle%20unit/contration%20of%20motor/contra36.jpg

Muscle contraction animation

http://classconnection.s3.amazonaws.com/1517/flashcards/715536/jpg/picture1.jpg

Contraction video

http://blazerstrength.com/wp-content/uploads/2012/07/atpadpcp.jpg

http://jeb.biologists.org/content/207/20/3441/F2.large.jpg

http://click4biology.info/c4b/3/images/3.7/summary.gif

http://legacy.owensboro.kctcs.edu/gcaplan/anat/images/Image370.gif

http://www.pef.uni-lj.si/eprolab/comlab/sttop/sttop-bm/figures/Myogram%20-%20contractions%2001.gif

http://classes.midlandstech.edu/carterp/Courses/bio210/chap09/Slide29.JPG