Review Questions begin on page 198 Muscular System Read Ch 6 Review Questions begin on page 198 S/A #2, 7, 10, 12, 18, 20, 21 At the Clinic #2, 5, 6

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

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.

Categorizing muscles Microscopically Nonstriated (no lines) http://phelafel.technion.ac.il/~tamarh/website/images/different-kinds-of-muscles-2.jpg Microscopically Nonstriated (no lines) Striated (lines running through) micro.magnet.fsu.edu/

Categorizing muscles Controllability Involuntary (no control) Voluntary (control)

Categorizing muscles Location Cardiac: Involuntary, only found in heart Smooth: Involuntary, lines digestive organs Skeletal: voluntary muscles found attached to bones

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

Physiology of muscle Contraction is achieved by the simultaneous shortening of all the sarcomeres within a cell. Three stages: Neural stimulation Contraction Relaxation.

Neural Stimulation Takes 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

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 sarcolemma www.cells.de/.../Neuromuscular-junction.jpg

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/...

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

Muscle Contraction www.cvphysiology.com 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.

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.

Myosin crossbridges at work…

http://www.patrickcarlberg.dk/images/thinfilament.jpg

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).

Squinting Stimulus Receptor Light reduced Effectors Regulator Sensory Nerves Light reduced Motor Nerves Effectors Regulator

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

Animations http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP2904 http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter42/animations.html#

Review Nerve impulse arrives at muscle cell Ca+2 released from SR into sarcoplasm Ca+2 combines with troponin molecules in the thick filaments of myofibrils (Myosin) Troponin without Ca+2 doesn’t interact like this Myosin interacts with Actin and pulls toward center Contraction of muscle Animation of entire process…

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.

Muscle Attachment Fibers Tendons—connect muscle to bone (cordlike) Aponeuroses—connect muscles to muscles (sheetlike)

Musculature terms Origin—fixed end (proximal end of bone) Insertion—moveable end (distal end of bone) www.scielo.cl/.../ijmorphol/v25n4/fig37-01.jpg

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.

Skeletal Muscle Action Antagonistic effects occur when one muscle opposes or resists the action of another muscle.—if nothing else, your muscles are acting against the antagonistic force of gravity The antagonistic actions are essential for pulling the relaxed muscle cells back to their original length.

Skeletal Muscle Action Synergistic effects occur when muscles work together to produce a common end result…the muscles of the forearm work synergistically with the muscles of the fingers to produce a fist. http://www.dkimages.com/discover/previews/779/76289.JPG

5 golden rules of skeletal muscle http://www.omnism.com/om/images/golden-rule.jpg All muscles cross at least one joint Typically the bulk of the muscle lies proximal to the joint crossed All muscles have at least two attachments, the origin and the insertion Muscles can only pull; they never push During contraction, the muscle insertion moves toward the origin

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

Body Movements Rotator—movement around an axis (partway around) Tensor—important posture/positioning muscles that make a body part more rigid or tense.

Body Movements Abduction—moving away from the midline Adduction—moving toward the midline

Body Movements Depressor—produce a downward movement Levatator—provide an upward movement Sphincter—decreases the size of an opening www.mda.org www.cescg.org

Special Movements Pronator—motion of palm downward Supinator—palm moves upward

Special Movements Inversion—turning the sole of your foot medially Eversion—turning the sole of your foot laterally

Special Movements Dorsiflexion—pointing your toes up toward your shin Plantar Flexion—pointing your toes downward

Muscular System Pathologies

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.

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.gov http://www.fairview.org

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

Contusion Bruising of the muscle www.bruisepatch.com

Muscle Spasms Involuntary, abnormal contractions of a muscle or muscle group Caused by a wide range of medical conditions www.cure-back-pain.org

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

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

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

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

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!

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 www.aids-images.ch

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

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.

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