The Muscular System Biol 105 Lecture Packet 11 Chapter 6

Copyright © 2009 Pearson Education, Inc. Outline I.Characteristics of muscles II.Three types of muscle III.Functions of muscles IV.Structure of skeletal muscles V.Mechanics of muscle contraction VI.Energy sources for muscle contraction

Copyright © 2009 Pearson Education, Inc. Muscular System  Remember there were different types of muscle: cardiac, smooth and skeletal.  All muscle cells are elongated and therefore are called muscle fibers.  All muscle tissues contract.  Muscles contain muscle cells (called muscle fibers), connective tissue, blood vessels, and nerves

Copyright © 2009 Pearson Education, Inc. 1.Smooth muscle 2.Cardiac muscle 3.Skeletal muscle 11-2 Types of Muscles

Copyright © 2009 Pearson Education, Inc.  Smooth muscles are involuntary muscles found in the walls of many internal organs (digestive tract, respiratory system, blood vessels).  Function to aid in the function of other organs 11-2 Smooth muscle

Copyright © 2009 Pearson Education, Inc.  Cardiac muscles are involuntary muscles found only in the heart wall.  Functions by contracting to force blood from the heart into the arteries 11-2 Cardiac muscle

Copyright © 2009 Pearson Education, Inc.  Skeletal muscle are voluntary muscles attached to the skeleton.  Usually work in pairs 11-2 Skeletal muscle

11-2

Copyright © 2009 Pearson Education, Inc. Skeletal Muscles Work in Pairs  Most skeletal muscles are antagonistic pairs.  One muscle contracts, the other relaxes  Muscles are attached to the bone by tendons  Skeletal muscles are usually attached to two bones on opposite sides of a joint

Copyright © 2009 Pearson Education, Inc. Skeletal Muscles Work in Pairs  The origin of the muscle is attached to the bone that remains stationary during movement  The insertion is attached to the bone that moves  Bones act as levers in working with skeletal muscles to produce movement

Copyright © 2009 Pearson Education, Inc. Skeletal Muscles Work in Pairs Figure 6.1a (a) Flexion The relaxed triceps is stretched. The biceps contracts and pulls the forearm up, flexing the arm. Origin of muscle: attachment of muscle to less moveable bone Insertion of muscle: attachment of muscle to more moveable bone

Copyright © 2009 Pearson Education, Inc. Functions of Skeletal Muscles 1.Support the body – maintain our posture 2.Movement of bones, and other tissues 3.Help maintain a constant body temperature – generates heat 4.Helps move blood through the veins and lymphatic fluid through the lymphatic vessels 5.Help to protect vital organs and stabilize joints

Copyright © 2009 Pearson Education, Inc. Smooth muscles are under this kind of control 1.Voluntary 2.Involuntary

Copyright © 2009 Pearson Education, Inc. Smooth muscles are found in 1.The heart 2.Digestive tract 3.Attached to bones

Copyright © 2009 Pearson Education, Inc. Structure of Skeletal Muscles  Muscles are covered by connective tissue called fascia.  A muscle contains bundles of skeletal muscle fibers (muscle cells), the bundles are called fascicles. These bundles are covered by connective tissue.  Blood vessels and nerves are between the fascicles.

Copyright © 2009 Pearson Education, Inc. Structure of Skeletal Muscles Figure 6.3a–b (b) A light micrograph of a longitudinal view of skeletal muscle cells Skeletal muscle consists of many bundles of muscle cells. A muscle cell consists of many myofibrils. A bundle of muscle cells is called a fascicle. (a) A section of a skeletal muscle The striped (striated) appearance of a skeletal muscle cell is due to the regular arrangement of myofilaments.

Copyright © 2009 Pearson Education, Inc. Sarcomeres Figure 6.3b–c (b) A light micrograph of a longitudinal view of skeletal muscle cells (c) A diagram and electron micrograph of a myofibril Z line One sarcomere The striped (striated) appearance of a skeletal muscle cell is due to the regular arrangement of myofilaments.

Copyright © 2009 Pearson Education, Inc. A bundle of muscle cells is called: 1.Fascicles 2.Fascia 3.Muscle Fibers

Copyright © 2009 Pearson Education, Inc. Muscle Cells  Muscle cells are long cells called muscle fibers.  The muscle fiber is composed of long thin myofibrils

Copyright © 2009 Pearson Education, Inc. a. T tubuleb. Sarcoplasmic reticulum c. myofibril d. Z line e. sarcomere f. sarcolemma

Copyright © 2009 Pearson Education, Inc. Muscle Cells cont  Myofibrils are bundles of myofilaments that contracts.  Myofilaments are made of actin and myosin filaments.  When muscle fibers are stimulated to contract, myofilaments slide past one another, causing sarcomeres to shorten.

Copyright © 2009 Pearson Education, Inc. Muscle Cell Components  Muscle cells (muscle fibers) have many of the same components as typical cells have but some of their components have different names

Copyright © 2009 Pearson Education, Inc. Muscle Cell Components  Sarcolemma – plasma membrane (cell membrane)  Sarcoplasm – similar to cytoplasm, contains large amount of stored glycogen and myoglobin.  Myoglobin is an oxygen binding protein similar to hemoglobin, but found only in muscles  Sarcoplasmic reticulum – similar to endoplasmic reticulum, one of its functions is to store Ca 2+

Copyright © 2009 Pearson Education, Inc. Muscle Cell Components  Muscle cells (muscle fibers) also have unique features:  Multiple nuclei  Transverse tubules (T tubules) – extensions of the sarcolemma that come into contact with the sarcoplasmic reticulum.

Copyright © 2009 Pearson Education, Inc. Muscle Contraction  The small myofibrils that make up the muscle fiber (muscle cell) contain two types of myofilaments: actin and myosin filaments  Sarcomere is the name for the structural unit of these myofilaments  The sarcomere goes between two dark lines = Z lines. The Z lines are protein sheets where the actin filaments attach

Copyright © 2009 Pearson Education, Inc. Sarcomeres Figure 6.3c–d (c) A diagram and electron micrograph of a myofibril (d) A sarcomere, the contractile unit of a skeletal muscle, contains actin and myosin myofilaments. Z line Actin Myosin One sarcomere

Copyright © 2009 Pearson Education, Inc.  The two myofilaments are:  Actin filaments: Thin filaments that formed by two intertwining strands of the protein actin.  Myosin filaments: Thick filaments of the protein myosin shaped like a golf club, with a round “head”. Myofilaments – actin and myosin

Copyright © 2009 Pearson Education, Inc.  The myosin heads can bind and detach from the thin actin filament. When bound it creates cross-bridges.  When the muscle is stimulated, these filaments slide past each other, making the sarcomere to shorten Myofilaments – actin and myosin

Copyright © 2009 Pearson Education, Inc. Muscle Contraction cont  A neuron signals the muscle to contract  The myosin heads attach to the actin then pull the actin toward the center of the sarcomere  Then the myosin heads detach

Copyright © 2009 Pearson Education, Inc. Sarcomeres Figure 6.4

Copyright © 2009 Pearson Education, Inc. Neuromuscular Junction Figure 6.7 (1 of 2)

Copyright © 2009 Pearson Education, Inc. Steps of Muscle Contraction 1.Action potentials are transmitted through the neurons. 2.At the end of the neurons neurotransmitters are released 3.Neurotransmitters bind to receptor on the sarcolemma

Copyright © 2009 Pearson Education, Inc. Steps of Muscle Contraction 4.The receptors are ion channels that open 5.An action potential travels through the T tubules 6.The action potential goes to the sarcoplasmic reticulum 7.The sarcoplasmic reticulum releases Ca 2+.

Copyright © 2009 Pearson Education, Inc. Steps of Muscle Contraction 8.The calcium binds to the troponin on the actin filament 9.This opens up binding site for the myosin to attach 10.Now the myosin binds to the actin 11.ATP is needed for the myosin to slide past the actin

Copyright © 2009 Pearson Education, Inc. Sarcomeres Figure 6.6 (1 of 2)

Copyright © 2009 Pearson Education, Inc. Sarcomeres Figure 6.6 (2 of 2)

Copyright © 2009 Pearson Education, Inc. Tropomyosin-troponin complex  The tropomyosin-troponin complex is attached to the actin filament.  Calcium binds to the troponin, causing a shift in the complex, opening the sites for myosin to attach. Muscle Contraction Video

Copyright © 2009 Pearson Education, Inc. ATP is needed for the myofilaments to slide past each other

Copyright © 2009 Pearson Education, Inc. What is the an oxygen binding protein found only in muscles? 1.Myosin 2.Actin 3.Hemoglobin 4.Myoglobin

Copyright © 2009 Pearson Education, Inc. What ion is required for the myofilaments to bind to each other? 1.Potassium 2.Calcium 3.Chloride 4.Sodium

Copyright © 2009 Pearson Education, Inc. Where is the calcium stored? 1.Nucleus 2.Sarcolemma 3.Sarcoplasmic reticulum

Copyright © 2009 Pearson Education, Inc. a. T tubuleb. Sarcoplasmic reticulum c. myofibril d. Z line e. sarcomere f. sarcolemma

Copyright © 2009 Pearson Education, Inc. ATP  ATP is the currency. Like money in the bank.  The bonds between the phosphate groups are high energy bonds

Copyright © 2009 Pearson Education, Inc. The Energy Source  Muscle contractions take a lot of energy in the form of ATP.  Muscles get their ATP from three sources:  1. The breakdown of creatine phosphate  2. Cellular respiration  3. Fermentation

Copyright © 2009 Pearson Education, Inc. 1. Creatine Phosphate  Creatine phosphate regenerates ADP to make ATP  This gives quick energy for a few seconds (up to 30 sec)  Only 1 ATP is produced per creatine phosphate  Oxygen is not needed.  When a muscle is resting, the ATP in turn regenerates creatine phosphate.

Copyright © 2009 Pearson Education, Inc. Direct phosphorylation

Copyright © 2009 Pearson Education, Inc. 2. Cellular Respiration  In the mitochondria, glucose is broken down to produce ATP.  Remember that oxygen is needed on the electron transport chain to produce the ATP.  Carbon dioxide is produced as a waste product during the Krebs cycle step in cellular respiration  Can provide energy for hours.  Produces 36 ATP per glucose molecule  Can use glucose as well as fatty acids and amino acids for energy source

Copyright © 2009 Pearson Education, Inc. 3. Fermentation  This is when the cell only uses glycolysis, and glucose is broken down to lactic acid.  Since the Krebs cycle and the electron transport chain is skipped, no oxygen is required.  No CO 2 is produced as a waste produce but lactic acid is produced  Can provide energy for 30 – 60 sec  2 ATP produced per glucose molecule

Copyright © 2009 Pearson Education, Inc. ATP Comes from Many Sources Figure 6.10

Copyright © 2009 Pearson Education, Inc. ATP Comes from Many Sources Figure 6.10 (1 of 2) 6 seconds10 seconds30–40 seconds ATP stored in muscles ATP formed from creatine phosphate and ADP ATP generated from glycogen stored in muscles and broken down to form glucose Oxygen limited Glucose oxidized to lactic acid

Copyright © 2009 Pearson Education, Inc. ATP Comes from Many Sources Figure 6.10 (2 of 2) End of exerciseAfter prolonged exercise ATP generated from glycogen stored in muscles and broken down to form glucose Oxygen debt paid back Breathe heavily to deliver oxygen Lactic acid used to produce ATP Creatine phosphate restored Oxygen restored to myoglobin Glycogen reserves restored Oxygen present Heart beats faster to deliver oxygen more quickly Myoglobin releases oxygen

Copyright © 2009 Pearson Education, Inc. CP breakdown Cellular Respiration Fermentation Requires O 2 NoYesNo Produces CO 2 NoYesNo # ATP produced 1362 Duration30 secHours30-60 sec

Copyright © 2009 Pearson Education, Inc. Which energy source would a long distance runner mainly use on a run that lasted for hours? 1.Fermentation 2.Cellular respiration 3.Creatine Phosphate

Copyright © 2009 Pearson Education, Inc. Which energy source would a sprinter use in the first 5 seconds of the race? 1.Fermentation 2.Cellular respiration 3.Creatine Phosphate

Copyright © 2009 Pearson Education, Inc. Important Concepts  What are the three types of muscles, where are they found, are they under vol. or invol. control  What are the functions of skeletal, cardiac and smooth muscles  How do skeletal muscles work in pairs?  What is the structure and the components of a muscle, and of a muscle cell (muscle fiber) and the functions of the muscle cell components.

Copyright © 2009 Pearson Education, Inc. Important Concepts  What is the function of tendons?  What stimulates a muscle to contract  Be able to describe the steps of how the message is transmitted from the neuron to the myofilaments  What is the role of Ca 2+.  What happens when the message is received by the myofilaments?

Copyright © 2009 Pearson Education, Inc. Important Concepts  What are the components of the muscle fibers, their functions, be able to identify them in an illustration, including: myofibrils, sarcomeres, Z lines, the myofilaments - actin and myosin filaments, cross-bridges, sarcolemma, sarcoplasm, sarcoplasmic reticulum, T-tubules  What are the components and the function of the tropomyosin-troponin complex

Copyright © 2009 Pearson Education, Inc. Important Concepts  What are the three energy sources for muscle contraction, which require oxygen, which produce carbon dioxide, how many ATP are produced, how long can it provide energy

Copyright © 2009 Pearson Education, Inc. Definitions  muscle fibers, myoglobin, fascia, fascicles, myofibrils, sarcomere, involuntary, voluntary, origin, insertion