IB BIOLOGY
TOPIC 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
1
C. *For a simple dissection:
http://www.practicalbiology.org/areas/advanced/cells-to-systems/supportand-movement/structure-of-synovial-joint-with-tendons-andligaments,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
2
E. The Human Elbow and How it Works
Figure 2. Anatomy of the human elbow (1).
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
3
Figure 4. The forearm flexed and extended.
http://hrsbstaff.ednet.ns.ca/sdosman/Higher%20level%20BIO/topic11.2notes.htm
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
4
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
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
Force
Fulcrum
Load
Elbow
Provided by biceps or triceps
Elbow joint
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
5
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.mcgrawhill.com/sites/0073532223/student_view0/chapter47/image_powerpoint_for_studen
ts.html
6
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_longitud
inal_section.php
7
A. General Characteristics
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
8
Figure 9. A muscle fibre and a sarcomere.
http://www.uoguelph.ca/zoology/devobio/210labs/sketchmuscle1.html
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
9
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
10
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#Fu
nctions%20of%20Muscles%20and%20Bones
11
Figure 15. Detail of myosin structure.
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
12
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.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::640::480::/sites/dl/free/00735322
23/811358/Sarcomere_Contraction.swf::Sarcomere%20Contraction
13
Animation of myofilament contraction (i.e. greater detail):
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::640::480::/sites/dl/free/00735322
23/811358/Myofilament_Contraction.swf::Myofilament%20Contraction
Animation of Role of Ca2+ ions and ATP in myofilament contraction:
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::640::480::/sites/dl/free/00735322
23/811358/Breakdown_of_ATP_and_Cross_Bridge_Movement_During_Muscle
_Contraction.swf::Breakdown%20of%20ATP%20and%20CrossBridge%20Movement%20During%20Muscle%20Contraction
Animation of role of action potential in release of Ca2+ ions:
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::640::480::/sites/dl/free/00735322
23/811358/Action_Potentials_and_Muscle_Contraction.swf::Action%20Potenti
als%20and%20Muscle%20Contraction
Figure 17. Mechanism of sliding filament model.
http://www.colorado.edu/intphys/Class/IPHY3430-200/image/12-9.jpg
14
15
1. The sliding filament model of muscle contraction
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/crossbridge 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
16
i. therefore, the sarcomere does not slide backward when the myosin
heads release the actin
2. Muscle relaxation
1. Acetylcholine is broken down by cholinesterase
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/Animat
ed%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
17
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
18
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.mcgrawhill.com/sites/0073525707/student_view0/chapter9/student_study_outline_an
swer_key.html
3. http://highered.mcgrawhill.com/sites/0073525707/student_view0/chapter8/student_study_outline_an
swer_key.html
19
4. 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
8. http://www.bbc.co.uk/science/humanbody/body/factfiles/joints/ball_and_sock
et_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.htm
11. http://www.biology-online.org/dictionary/Synovial_joint
12. http://wordnetweb.princeton.edu/perl/webwn?s=diarthrosis
13. http://click4biology.info/c4b/11/hum11.2.htm
14.
http://www2.estrellamountain.edu/faculty/farabee/biobk/BioBookMUSSKEL.html
#Functions%20of%20Muscles%20and%20Bones
15. 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
20
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
21
Hip and Knee joint
http://www.childrenshospital.org/az/Site569/mainpageS569P0.html
22
23