muscular system read ch 6 review questions begin on page 198 s/a #2, 7, 10, 12, 18, 20, 21 at the...
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Muscular System
Read Ch 6 Review Questions begin on page 198
S/A #2, 7, 10, 12, 18, 20, 21At the Clinic #2, 5, 6
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Overview
Over ½ of body’s mass is muscle—90% of that is skeletal muscle
These contractile cells have high energy needs, so it’s common to see an ample blood supply associated with muscles
http://www.edukshun.info/wp-content/uploads/2008/04/big-muscles.jpg
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Overview con’t: Blood provides glucose and oxygen while removing
metabolic waste products Muscles (and nervous tissue) consume almost 70%
of the food energy taken into your body daily Muscle is as intensive a consumer of calcium as is
the skeletal system—much of the Ca stored in bones is made available for the muscles’ needs.
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Categorizing muscles
Microscopically
Nonstriated (no lines)
Striated (lines running through)
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Categorizing muscles
ControllabilityInvoluntary (no control)Voluntary (control)
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Categorizing muscles
Location Cardiac: Involuntary, only found in
heart Smooth: Involuntary, lines digestive
organs Skeletal: voluntary muscles found
attached to bones
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Functions of the Muscular System
Movement of body parts—by pulling on bones. Bones act as levers, joints as the fulcrum.
Guard entrances and exits
Posture Stabilizing joints Create heat
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Physiology of muscleContraction is achieved by
the simultaneous shortening of all the sarcomeres within a cell.
Three stages: Neural stimulationContractionRelaxation.
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Neural StimulationTakes place at
the neuromuscular junction.
The nerve cell releases a neurotransmitter
neurotransmitter—a chemical used for cell to cell communication.
http://www.freewebs.com/soaring_sphincter_travel_agency/nerve%20impulse2.bmp
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Neural Stimulation Muscles respond to
the neurotransmitter acetylcholine (Ach).
Ach binds to receptors on the sarcolemma.
The binding of Ach affects the transport of ions across the sarcolemmawww.cells.de/.../Neuromuscular-
junction.jpg
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Neural Stimulation In a resting muscle, the concentration of
sodium ions is normally higher in the fluid outside the muscle cell while the concentration of potassium ions is higher inside the cell.
Sodium/potassium pumps maintain these unequal ion concentrations.
upload.wikimedia.org/wikipedia/commons/thumb/...
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Neural Stimulation This imbalance produces an unstable
condition. When stimulated by Ach the membrane loses its ability to maintain the imbalance.
Once the membrane is stimulated, it opens the ion channels permitting the free flow of sodium into the muscle cell and potassium out of the cell.
In turn, calcium stored in the sarcoplasmic reticulum is released to begin the contraction phase
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Muscle Contraction When calcium
(released by the sarcoplasmic reticulum) binds to the troponin, contraction begins.
Troponin sits on tropomyosin on the same region where actin binds to myosin.
www.cvphysiology.com
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Muscle Contraction Ca bumps troponin off the binding
site, permitting myosin to attach to actin.
Troponin also transmits info that activates ATP synthesis around the myosin. The ATP provides energy for the myosin head to swivel and pull the myosin toward the actin.
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Myosin crossbridges at work…
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http://www.patrickcarlberg.dk/images/thinfilament.jpg
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Muscle Relaxation Relaxation occurs when there are no
more neural stimulations exciting the sarcolemma. The sodium and potassium ion levels are completely recovered
The sarcoplasmic reticulum has retrieved most of the Ca, causing the release of the myosin heads from the actin.
There is no mechanism for the muscle cell to lengthen (so we’ll discuss how that happens later in the lecture).
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SquintingStimulus
Receptor
Regulator
Sensory Nerves
Motor Nerves
Effectors
Light reduced
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Video links
http://www.hippocampus.org/Biology
search for Biology for AP/Skeletal Muscle contraction
Crash course—Muscles http://www.youtube.com/watch?v=jqy0i1KXUO4
Bozeman Science—Muscles http://www.youtube.com/watch?v=mejCXr7p37U&list=PLCC2DB523BA8BCB53&index=17
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Neural Stimulation Videos
https://www.youtube.com/watch?v=0mhAN4-8uWo
https://www.youtube.com/watch?v=uJTdx1GbEqU&noredirect=1
http://www.youtube.com/watch?v=hzXVe4RS8-A
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Muscular Contraction videos
http://www.youtube.com/watch?v=BMT4PtXRCVA
https://www.youtube.com/watch?v=zopoN2i7ALQ
https://www.youtube.com/watch?v=f0mDFP7qn1Y
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Animations
http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP2904
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter42/animations.html#
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Contraction in Action
Planning your skit…
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http://3dotstudio.com/contract.gif
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http://media-2.web.britannica.com/eb-media/36/2836-004-C63246A5.gif
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Contraction in Action--Skit
Links to put on website http://www.youtube.com/watch?v=
EdHzKYDxrKc http://www.youtube.com/watch?
v=mWPmUqRZYls http://www.youtube.com/watch?v=e3Nq-
P1ww5E
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Muscle cell structure
Animation of entire process…
Video of sarcomere shortening
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Other factors found in muscle fibers ensuring adequate muscle contractions: Creatine Phosphate: stores energy in
muscle cells. It collects this energy from ATP and is capable of storing it for long periods of time.
Glycogen (stored form of glucose) can supply glucose when muscles cells need it to produce ATP
Myoglobin is a chemical that stores oxygen for certain muscle cells. This O2 permits muscle cells to provide large amounts of ATP during continuous or heavy work.
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Skeletal Muscle Action Muscle cells either contract or don’t…so
we get graded effects based on contraction of more individual fibers at the same time.
Strength is achieved by stimulating more individual fibers to fire
Endurance is achieved by producing contraction and relaxation groups working together.
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Body Movements Flexor—decreases
the angle of the joint by bringing the bones closer together
Extensor—extends a joint by increasing the angle between the bones
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Body MovementsRotator—
movement around an axis (partway around)
Tensor—important posture/positioning muscles that make a body part more rigid or tense.
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Body MovementsAbduction—
moving away from the midline
Adduction—moving toward the midline
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Body Movements Depressor—
produce a downward movement
Levatator—provide an upward movement
Sphincter—decreases the size of an opening
www.cescg.org
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Special MovementsPronator—
motion of palm downward
Supinator—palm moves upward
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Special Movements
Inversion—turning the sole of your foot medially
Eversion—turning the sole of your foot laterally
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Special MovementsDorsiflexion—
pointing your toes up toward your shin
Plantar Flexion—pointing your toes downward
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Muscular System
Pathologies
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Rigor Mortis Calcium leakage out of the sarcoplasmic
reticulum into the sarcomere. Common after death. Eventually, the muscle cells structures start to decay, causing the muscles to become soft and loose.
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Strain Most common
muscle ailment An injury due to
overworking the muscle’s force on the joints.
Injury to the tendon or muscle tissue
http://www.nlm.nih.govhttp://www.fairview.org
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Sprain A sprain is an injury
to a ligament. (A ligament is a thick, tough, fibrous tissue that connects bones together.)
Ligaments prevent abnormal movements. When too much force is applied to a ligament they can be stretched or torn. www.eorthopod.com
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Contusion Bruising of
the muscle
www.bruisepatch.com
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Muscle Spasms Involuntary,
abnormal contractions of a muscle or muscle group
Caused by a wide range of medical conditions
www.cure-back-pain.org
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Muscle Cramp Painful contraction of
a muscle Extreme muscle
exertion is the most common cause of cramps, although certain poisons and bacterial infections can also cause muscle cramping
www.answers.com
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Paralysis
Complete failure of a muscle function Rigid paralysis—excessive muscle
stiffness Flaccid paralysis—complete lack of
muscle contraction Many causes…including spinal injury
and poisoning Eg: Tetanus--Caused by soil bacteria
that produces poisons that cause rigid paralysis
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Dermatomyositis
Inflammation of the muscle and overlying skin.
Cause: unknown, but it can be treated with drugs (to reduce inflammation) and sun avoidance www.nytimes.com
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Muscular dystrophies Group of conditions
that involve progressive weakness in the voluntary muscles.
Usually due to the inability of the nervous system to stimulate muscle action
Eventually results in muscle atrophy and wasting.
esciencenews.com
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Tetany Calcium imbalance disease that causes extended periods of spasms in the arm and leg muscles.
Do NOT confuse this with the bacterial disease tetanus!
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Cachexia Type of muscle loss associated with
diseases such as AIDS and cancer.
Also found in starvation and a common consequence of anorexia and bulimia
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Cachexia A slower form is a normal consequence
of aging b/c the body reduces its ability to rebuild muscle structure as you age. Brought about by sedentary lifestyles—
resulting from other age related illnesses Neural stimulation also is lessened as
you age; important for muscle upkeep
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Nutritional issues with muscle loss
Protein turnover: muscles need lots of protein to maintain their integrity Malnutrition and undernutrition as we age
greatly affects protein turnover. Can be caused by poor diets or income levels Lack of appetite as we age is another
contributing factor As we age, our digestive system can’t absorb
some of the impt amino acids needed for muscle cell growth/maintenance.
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Muscle atrophy—other causes
Decline in sex hormones and other chemical messages needed for muscle cell growth, maintenance and repair. Insulin-like growth factor-1: known
to lessen with maturity Cytokines cause muscle atrophy
and are known to increase with age