2 Muscle Tissue Functions Producing body movementsStabilizing body positionsRegulating organ volumesBands of smooth muscle called sphincters.Movement of substances within the bodyBlood, lymph, urine, air, food and fluids, sperm.Producing heatVoluntary and involuntary (shivering) contractions of skeletal muscle.
3 Properties of Muscle Tissue Electrical ExcitabilityAbility of skeletal muscles to respond to stimulus. Skeletal muscle contracts as a result of stimulation by nerves.ContractilityAbility to contract (shorten and generate force).ExtensibilityAbility to be stretched without damaging tissue.ElasticityAbility to return to original shape after being stretched.
4 Smooth Muscle TissueHistology- spindle-shaped, nonstriated fibers with one centrally located nucleus.Location- walls of hollow internal structures such as blood vessels, airways to lungs, stomach, intestines, uterus.Speed of Contraction- slowest.Function- motion.Nervous Control- involuntary; autorhythmic.
5 Cardiac Muscle TissueHistology- branched, striated fibers, with one or two centrally located nuclei and intercalated discs.Location- heart wall.Speed of Contraction- moderate.Function- pumps blood.Nervous Control- involuntary; autorhythmic.
7 Skeletal Muscle Tissue Histology- long, cylindrical, striated fibers with many peripherally located nuclei.Location- attached primarily to bones by tendons.Speed of Contraction- fastest.Function- motion, posture, heat production.Nervous Control- voluntary; no autorhythmicity.
8 Fascicle- a bundle of skeletal muscle fibers. Figure: 06-01Title:Some major muscles of the body.Caption:
9 Muscle Terminology Origin- stable attachment of muscle to skeleton. Insertion- moveable attachment of muscle to skeleton.Flexor- decreases joint angle.Extensor- increase joint angle.Adductor- moves bone closer to midline.Abductor- moves bone away from midline.Levator- raises a body part.Depressor- lowers a body part.Figure: 06-02Title:Action of the biceps and triceps.Caption:The antagonistic action of the triceps and biceps muscles during flexion and extension, showing origins and insertions of the muscles.
11 Connective Tissue and Skeletal Muscles Fascia- a sheet or broad band of fibrous connective tissue that supports and surrounds organs of the body.Superficial fascia- loose connective and adipose tissue that separates muscle from skin.Deep fascia- dense, irregular connective tissue that lines the body wall and limbs, it also holds muscles together.
12 Deep Fascia 3 Layers of deep fascia Epimysium- surrounds the whole muscle.Perimysium- surrounds bundles (fascicles) of muscle fibers.Endomysium- surrounds individual muscle fibers.Muscle Belly- the fleshy portion of the muscle between the tendons.Tendon- cord of dense, regular connective tissue that attaches a muscle to the periosteum of a bone.
14 Muscle Fiber- elongate shaped muscle cell. Myofibrils- contractile elements of skeletal muscle.Filaments- smaller structures inside the myofibrils.Thin (actin) filaments (8 nanometers in diameter).Thick (myosin) filaments (16 nanometers in diameter).Thin filamentsThick filamentsMyofibrilMyofibrilTerminal cisternsSarcoplasmic reticulum
15 Filaments and Sarcomeres Thick (myosin) and thin (actin) filaments overlap each other in a pattern that creates striations.SarcomeresContractile units in skeletal and cardiac muscle fibers.Extend from one Z disc to another Z disc.
20 Figure: 06-07Title:A neuromuscular junction.Caption:The connection between a motor neuron and a muscle cell is called a neuromuscular junction.
21 Rigor MortisRigor mortis is a state of muscular rigidity that begins 3-4 hours after death and lasts about 24 hours.After death, Ca2+ ions leak out of the sarcoplasmic reticulum and allow myosin heads to bind to actin.Since ATP synthesis has ceased, crossbridges cannot detach from actin until proteolytic enzymes begin to digest the decomposing cells.
22 Energy for Muscle Contraction ATP (Adenosine Triphosphate)- energy.Phosphate breakdown (anaerobic).Glycolysis and fermentation (anaerobic).Cellular respiration (aerobic).
23 Creatine PhosphateCreatine phosphate is 3-6X more plentiful than ATP within muscles.Its quick breakdown provides the P for creation of ATP.Sustains maximal contraction for 15 sec (used for 100 meter sprint).Creatine supplementationGain muscle mass but shut down bodies own synthesis.
24 Anaerobic Cellular Respiration ATP produced from the breakdown of glucose into pyruvic acid during glycolysis.If still anaerobic, pyruvic acid is converted to lactic acid.Glycolysis can continue anaerobically to provide ATP for 30 to 40 seconds of maximal activity (200 meter race).
25 Aerobic Cellular Respiration ATP for any activity lasting over 30 seconds.If sufficient oxygen is available, pyruvic acid enters the mitochondria to generate ATP, water, and heat.Fatty acids and amino acids can also be used by the mitochondria.Provides 90% of ATP energy if activity lasts more than 10 minutes.
26 Athletics and Muscle Contraction Hypertrophy- increase in muscle size.The result of forceful muscular activity over a prolonged period of time.Results in an increase in the number of myofibrils within a muscle fiber.
28 Atrophy Atrophy- decrease in muscle size. The result of muscles not being used or only being used in weak contractions.Causes muscle fibers to progressively shorten, leaving body parts contracted and in contorted positions.
29 Classification of Muscle Fibers Slow-twitch fibersDesigned for enduranceContract slowlyStrong, sustained contractionsRed in color (lots of mitochondria, myoglobin, & blood vessels)Muscles of abdomen and back (posture)Fast-twitch fibersDesigned for rapid, powerful responseContract rapidlyShort, powerful contractionsWhite in color (few mitochondria, myoglobin, & blood vessels)Muscles of the arms of legs
30 Aging and Muscle Tissue Skeletal muscle starts to be replaced by fibrous connective tissue and fat beginning at age 30.Slowing of reflexes, loss of flexibility, and decrease in strength.Change in fiber type from fast to slow.
31 Muscle DiseaseMuscular dystrophy- a broad term applied to a group of inherited muscular disorders characterized by progressive muscle degeneration and weakening.Frequency- 1 in 3,500 males.Genetics- males XY, females XX.Treatment- none.Mutation in DMD gene. DMD codes for dystrophin, a protein that protects muscle fibers.
32 Abnormal Contractions Spasm- involuntary contraction of a single muscle.Cramp- a painful spasm.Seizure- multiple spasms of a skeletal muscle.Tic- involuntary twitching of muscles normally under voluntary control.Tremor- rhythmic, involuntary contraction of opposing muscle groups.Fasciculation- involuntary, brief twitch of a motor unit visible under the skin.Fibrillation- spontaneous contraction of a single muscle fiber that is not visible under the skin.