IB BIOLOGYTOPIC 11.2: MUSCLES AND MOVEMENT

I. Human Movement

A. Structures involved

1. Bones: function to support the body and provide levers for movement, protect internal organs from damage, store calcium and phosphate, and make blood cells

2. Ligament: connective tissue that connects two or more bones together at a movable joint, restrict movement at joints to help prevent dislocation

3. Muscle: tissue made of cells (referred to as fibres) that are able to contract

4. Tendon: connective tissue that connects muscle to bone

5. Nerves: provide electrical stimulation to signal muscles to contract

II. Joints and The Human Elbow Joint and How It Works

A. Joint: the place where 2 bones meet and are attached by ligaments or cartilage

1. May be fibrous/fixed (not allowing movement), cartilaginous/slightly movable, or diarthrotic/movable

B. Synovial Joints: movable joints containing a layer of cartilage on the opposing bone surfaces and a lubricating liquid known as synovial fluid found in the synovial cavity

Figure 1. A synovial joint.

http://intranet.canacad.ac.jp:3445/BiologyIBHL2/5017

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C. *For a simple dissection: http://www.practicalbiology.org/areas/advanced/cells-to-systems/support-and-movement/structure-of-synovial-joint-with-tendons-and-ligaments,61,EXP.html

1. Cartilage: reduces friction between bones because it provides a smooth surface, also acts as a shock absorber

2. Synovial fluid: lubricates joints and reduces friction, also provides nutrients and oxygen to the cells of the cartilage

3. Joint capsule: surrounds and seals the joint and contains the synovial fluid within the synovial cavity

D. Types of synovial joints: ball and socket, ellipsoidal joints, gliding joints, hinge joints, pivot joints, saddle joints (there are other categories possible depending on the reference)

*for a few diagrams and animations go here: http://faculty.stcc.edu/AandP/AP/AP1pages/Units5to9/joints/synovial.htm

E. The Human Elbow and How it Works

Figure 2. Anatomy of the human elbow (1).2

http://intranet.canacad.ac.jp:3445/BiologyIBHL2/5017

Figure 3. Anatomy of the human elbow (2).

http://hrsbstaff.ednet.ns.ca/sdosman/Higher%20level%20BIO/topic11.2notes.htm

Figure 4. The forearm flexed and extended.

http://hrsbstaff.ednet.ns.ca/sdosman/Higher%20level%20BIO/topic11.2notes.htm3

A. The triceps muscle attaches to the humerus bone (origin) and to the ulna bone (insertion)

B. Contraction of the triceps pulls the insertion towards the origin

1. Causes the arm to be straightened or extended at the elbow

2. Triceps are called an extensor (muscle)

C. The biceps muscle attaches near the shoulder joint (origin) and to the radius bone near the elbow (insertion)

D. Contraction of the biceps pulls the insertion towards the origin

1. Causes the arm to bend or flex at the elbow

2. Biceps are called a flexor (muscle)

E. Together, the triceps and biceps from an antagonistic pair of muscles

1. Antagonistic pairs are required because muscles can only contract to become shorter and relax to return to the original length; they cannot lengthen

2. Most movement in the human body requires antagonistic pairs of muscles

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F. The elbow as a lever system

1. Acts as a third class lever, multiplying distance rather than force

Table 1. A comparison of the elbow with the components of a lever system.

Components of a Lever System ElbowForce Provided by biceps or tricepsFulcrum Elbow jointLoad Provided by the hand

III. The hip joint versus the knee joint

Table 2. A comparison of the hip and knee joints.

http://click4biology.info/c4b/11/hum11.2.htm

Figure 5a and b. The knee joint, hinge joint.

http://click4biology.info/c4b/11/hum11.2.htm

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Figure 6a, b, and c. The hip joint, a ball and socket joint.

http://click4biology.info/c4b/11/hum11.2.htm

IV. Striated Muscle

Figure 7. Skeletal Muscle.

http://highered.mcgraw-hill.com/sites/0073532223/student_view0/chapter47/image_powerpoint_for_students.html

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Figure 8. Skeletal muscle, longitudinal section. (I could not copy it over but it is really nice.)

http://medcell.med.yale.edu/systems_cell_biology/muscle/skeletal_muscle_longitudinal_section.php

A. General Characteristics

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1. Striated, multinucleate

2. Voluntary

3. Groups of cells are surrounded by tissues to form bundles

B. Structure of striated muscle fibres

1. Each muscle cell is referred to as a muscle fibre

2. Sarcoplasm: cytoplasm of muscle cells/muscle fibres

a. Contain many glycosomes to store glycogen

b. Has a lot of myoglobin (red in colour)

c. Has many mitochondria for aerobic cellular respiration

i. called sarcosomes

3. Sarcolemma: the cell membrane of a muscle cell/muscle fibre

4. Sarcoplasmic reticulum: extensions of the smooth endoplasmic reticulum that surround the myofibrils

a. Function to store Ca2+ ions

5. T-tubules: (aka: transverse tubules) are tubules that extend from the sarcolemma throughout the cell and are next to (but not attached to) the sarcoplasmic reticulum

a. Spread action potentials throughout the cell

6. Have bundles of cytoskeleton referred to as myofibrils made of the proteins actin and myosin

a. These are the structures that allow the cells to contract/shorten (and then relax/return to the original length)

b. Made of repeating units called sarcomeres

C. Sarcomeres

Figure 9. A muscle fibre and a sarcomere.

http://www.uoguelph.ca/zoology/devobio/210labs/sketchmuscle1.html

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Figure 10. Detail of a sarcomere with labelled striations.

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Muscles.html

Figure 11. Detail of a sarcomere with direction of actin movement during contraction.

http://www.colorado.edu/intphys/Class/IPHY3730/image/figure9-8.gif

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Figure 12. Labelled electron micrograph of a sarcomere. (I could not copy it over but it is really nice.)

http://medcell.med.yale.edu/systems_cell_biology/muscle/sarcomere_em.php

Figure 13. Sarcomere diagram with detail of actin and myosin.

http://www.colorado.edu/intphys/Class/IPHY3430-200/image/12-3c.jpg

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1. The functional units of the muscle cell

2. Appear as light and dark bands

a. Z line/disk: separates the sarcomeres

b. I band: produced by the thin filaments (actin)

i. note that the actin filaments cross the Z line/disk and thus is part of 2 sarcomeres

c. A band: produced by the thick filaments (myosin) and in some places overlap between the myosin and actin

d. H zone: section in the A band where the thick and thin filaments do not overlap

e. M line: runs through the exact middle/centre of the sarcomere

Figure 14: The structure of actin and myosin filaments.

http://www2.estrellamountain.edu/faculty/farabee/biobk/BioBookMUSSKEL.html#Functions%20of%20Muscles%20and%20Bones

Figure 15. Detail of myosin structure.

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http://www.colorado.edu/intphys/Class/IPHY3430-200/image/12-3e.jpg

Figure 16. Detail of actin structure with troponin and tropomyosin.

http://www.colorado.edu/intphys/Class/IPHY3430-200/image/12-3f.jpg

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3. Has thick filaments made of myosin and thin filaments made of actin

a. An actin filament is made of 2 long, relatively thin chains of actin proteins strung together like beads then twisted together

i. also associated with troponin and tropomyosin (2 more proteins)

b. A myosin protein is made of one heavy chain and two light chains put together with a long “tail” region and a “head” region, then two proteins are put together to form one functional unit with two “heads”, many functional units together, with “heads” at either end, make up a thick filament

D. Mechanism of skeletal muscle contraction

Animation of sarcomere contraction: http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::640::480::/sites/dl/free/0073532223/811358/Sarcomere_Contraction.swf::Sarcomere%20Contraction

Animation of myofilament contraction (i.e. greater detail): http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::640::480::/

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sites/dl/free/0073532223/811358/Myofilament_Contraction.swf::Myofilament%20Contraction

Animation of Role of Ca2+ ions and ATP in myofilament contraction: http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::640::480::/sites/dl/free/0073532223/811358/Breakdown_of_ATP_and_Cross_Bridge_Movement_During_Muscle_Contraction.swf::Breakdown%20of%20ATP%20and%20Cross-Bridge%20Movement%20During%20Muscle%20Contraction

Animation of role of action potential in release of Ca2+ ions:http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::640::480::/sites/dl/free/0073532223/811358/Action_Potentials_and_Muscle_Contraction.swf::Action%20Potentials%20and%20Muscle%20Contraction

Figure 17. Mechanism of sliding filament model.

http://www.colorado.edu/intphys/Class/IPHY3430-200/image/12-9.jpg

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1. The sliding filament model of muscle contraction

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a. Action potential reaches the neuromuscular junction and the neurotransmitter acetylcholine is released

b. Acetylcholine causes the action potential to spread along the sarcolemma and into the sarcoplasm via the t-tubules

c. Voltage gated channels open an Ca2+ ions originally stored in the sarcoplasmic reticulum diffuse out

d. Ca2+ ions bind to troponin

e. Causes a change in the configuration of the molecules

f. Tropomyosin moves and reveals a binding site for myosin heads/cross-bridge binding sites

g. Myosin heads bind to the binding sites

i. myosin head has ADP and Pi attached to it

h. The Pi is released, initiating the “power stroke”

i. Myosin head rotates, pushing the actin filament past it

j. Moves the actin filaments a short distance toward the centre of the sarcomere

k. Myosin head releases the ADP

l. ATP bonds to the ATPase/ATP binding site

m. Causes the myosin heads to detach from the actin

n. ATP hydrolyzed to ADP and Pi

o. Cycle begins again as long as there continues to be acetylcholine and Ca2+

p. Notice that there are many myosin filaments that are positioned in a slightly staggered fashion and that they do not all work in complete unison

i. therefore, the sarcomere does not slide backward when the myosin heads release the actin

2. Muscle relaxation

1. Acetylcholine is broken down by cholinesterase16

2. Sarcolemma and t-tubules repolarized

3. Ca2+ returned to sarcoplasmic reticulum via pumps

4. Actin-myosin cross-bridge formation stops

5. Tropomyosin returns to cover myosin binding site on the actin

6. Passive sliding of actin

Animation that reviews sarcomere structure and function:

http://content.bfwpub.com/webroot_pubcontent/Content/BCS_3/Sadava_9e/Animated%20Tutorials/life9e_4801_muscle_contra.html

3. Rigor mortis

1. At death, production of ATP stops

2. Muscles become stiff because no ATP to cause myosin to detach from the actin

E. Identifying the state of contraction of muscles fibres using electron micrographs

Figure 18. How banding patterns change during contraction.

http://www.colorado.edu/intphys/Class/IPHY3430-200/image/12-8.jpg

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Figure 19. Electron micrographs of relaxed and contracted muscle.

http://hrsbstaff.ednet.ns.ca/sdosman/Higher%20level%20BIO/topic11.2notes.htm

1. note that the entire sarcomere shortens

2. the dark band (myosin only or myosin overlapping with actin) stays the same width

a. means that the myosin fibres are not shortening

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b. the sarcomere must be shortening because the filaments are sliding past each other

3. the light band/I band shortens

V. Cardiac Muscle

A. Makes up the walls of the heart

B. Cells are short and striated like skeletal muscle

C. Myofibrils are branched

D. Cells have only one nucleus

E. Richer supply of mitochondria than skeletal muscle

F. Has little glycogen and is very dependent on aerobic cellular respiration

G. involuntary

VI. Smooth Muscle

A. Found in walls of organs, reproductive tract and blood vessels

B. No striations visible

C. Contraction tends to be slower than in striated muscle

D. Involuntary

E. Cells are tapered at the ends

References:

1. http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Bone.html 2. http://highered.mcgraw-hill.com/sites/0073525707/student_view0/chapter9/

student_study_outline_answer_key.html3. http://highered.mcgraw-hill.com/sites/0073525707/student_view0/chapter8/

student_study_outline_answer_key.html4. http://www.daviddarling.info/encyclopedia/L/ligament.html 5. http://faculty.stcc.edu/AandP/AP/AP1pages/Units5to9/Unit7/unit7.htm (many pages that can be accessed from this one)6. http://www.as.wvu.edu/~sraylman/comparative/lectures/8muscles.pdf 7. http://intranet.canacad.ac.jp:3445/BiologyIBHL2/5017

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8. http://www.bbc.co.uk/science/humanbody/body/factfiles/joints/ ball_and_socket_joint.shtml

9. http://www.bcb.uwc.ac.za/Sci_Ed/grade10/manphys/joints.htm 10. http://faculty.stcc.edu/AandP/AP/AP1pages/Units5to9/joints/joint.htm11. http://www.biology-online.org/dictionary/Synovial_joint12. http://wordnetweb.princeton.edu/perl/webwn?s=diarthrosis13. http://click4biology.info/c4b/11/hum11.2.htm14. http://www2.estrellamountain.edu/faculty/farabee/biobk/BioBookMUSSKEL.html#Functions%20of%20Muscles%20and%20Bones15. http://meat.tamu.edu/muscontract.html

Practice:

1. Activities 48.1 (The Structure of a Sarcomere) and 48.2 (The Neuromuscular Junction): http://bcs.whfreeman.com/thelifewire9e/default.asp#542578__591142__

2. Try to label the following:

http://www.colorado.edu/intphys/Class/IPHY3430-200/010muscles.htm

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http://www.sciencephoto.com/images/download_lo_res.html?id=670056777

3. Try to label the following two diagrams of the elbow from: http://click4biology.info/c4b/11/11.2/elbow.gif

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Hip and Knee joint

http://www.childrenshospital.org/az/Site569/mainpageS569P0.html

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