Chapter 10
Skeletal Muscle Tissue and the Muscular System
▪3 types of muscle; cardiac, smooth, skeletal
▪Functions of skeletal muscles:
Anatomy of skeletal muscle
▪Organization of Connective Tissues (from outer to inner)
▫Epimysium
▫Perimysium
▫Fascicle
http://training.seer.cancer.gov/anatomy/muscular/structure.html
▫Edomysium
-Myosatellite cells▫all “–mysium” join together to form tendons and aponeuroses
▪Blood Vessels and Nerves
▫Connective tissues of the epimysium and perimysium contain the blood
and nerves that supply the muscle fibers.
1
▪Skeletal Muscle Fibers
▫Sarcolemma
▫Sarcoplasm
▫Transverse Tubules (T tubules)
▫Myofibrils
▫Sarcoplasmic reticulum
-Terminal cisternae
-Triad
▫Sarcomere
-A band- dArk band
-M line
http://biophysicsandyourbody.wordpress.com/lesson-4/
-H zone
-Zone of Overlap
-I band- lIght band
-Z line (disc)-Actinins-Titin-
2
-two transverse tubules encircle each sarcomere, triads are found on
either side of the M line. Allows Ca2+ to enter where thin and thick
filaments can interact.
-Thin Filaments- contains 4 proteins
-F actin
-G actin contains an active site that binds to a myosin
head
-Nebulin
-Tropomyosin-Troponin-Thick Filaments- has a head end and a tail end
-Tail is two myosin subunits twisted together
-Head projects toward nearest thin filament.
-Cross-bridges▪Sliding Filament Theory- The explanation of muscle contraction.
▫Describes that the thin filaments move along the thick filaments toward
the center of the sarcomere.
The Contraction of Skeletal Muscle
▪Control of Skeletal Muscle Activity
▫Neuromuscular junction
▫Acetyelcholine (ACh)
3
▫Synaptic cleft
▫Motor end plate
▫Acetylcholinesterase (AChE)
*Use figure 10-9 to work through the steps of a neuron stimulating a muscle fiber*
▪Excitable Membranes
▫Membrane potential
▫Depolarization
▫Repolarization
▫Hyperpolarization
▫Graded potential
▫Action potential
▪Excitation-contraction coupling
▫When the action potential reaches the triad, it triggers the release of Ca2+ from
the cisternae of SR.
▫This release lasts only 0.03 seconds, yet increases the Ca2+ levels around the
sarcomere a hundred fold.
▫Since the terminal cisternae are located at the zone of overlap, the Ca2+
reaches the myofilaments almost instantly.
▫troponin binds with Ca2+, causing tropomyosin to move aside revealing the
active sites for myosin head binding.
▫This action is the beginning of the contraction cycle.
4
*Use figure 10-11 to work through the 5 steps of the contraction cycle*
▪Relaxation
▫Outside forces must act on the contracted muscle fiber to return it to its
original length.
Tension Production
▪Tension Production by Muscle Fibers
▫Muscle fibers contract in an all-or-none mechanism
▫Tension production by muscle fibers can vary, depending on two things:
1.
2.
▫Length-Tension Relationships
▫Frequency of stimulation
-Twitch
-Treppe-Wave summation-Incomplete tetanus-Complete tetanus▫The amount of tension produced by a whole muscle is determined by the
1.
2.
5
▫Motor Units
-Recruitment
▫Muscle Tone
▫Isotonic Contractions
-Concentric contraction
-Eccentric contraction
▫Isometric Contractions
Energy Use and Muscular Activity
▪ATP and CP Reserves- ATP and CP are both high energy compounds
▫ATP phosphorylates creatine to produce creatine phosphate
▫When muscle contraction occurs, dephosphorylated ATP (ADP) is then
rephophorylated by CP.
▫ATP reserves last about _____ seconds
▫CP reserves last about _____ seconds
▪ATP Generation
▫Aerobic metabolism
6
▫Glycolysis
▪Energy Use and the Level of Muscle Activity
▫Rest
▫Moderate Activity
▫Peak Activity
*Use figure 10-20 to see the relationship between energy use and muscle activity.*
▪Muscle Fatigue-
▫Muscle fatigue is cumulative
▪The Recovery Period- conditions in muscle fibers return to normal, pre-exertion levels.
▫Cori Cycle
▫Oxygen Debt
▫Heat Loss
7
▪Hormones and Muscle Metabolism
▫Growth hormone and testosterone stimulate the synthesis of contractile
proteins and the enlargement of skeletal muscles.
▫Thyroid hormones elevate the rate of energy consumption by resting and
active skeletal muscles.
▫Epinephrine stimulates muscle metabolism during a sudden crisis.
Muscle Performance
▪Types of Skeletal Muscle Fibers
▫Fast Fibers (majority of skeletal muscles)
-Large in diameter
-Densely packed myofibrils
-Large glycogen reserves
-Relatively few mitochondria
-Fatigue rapidly, build up of lactic acid
-Also called: white muscle fibers, fast-twitch glycolytic fibers, type
II-A.
▫Slow Fibers
-Half diameter of fast fibers
-Extensive capillary network, high oxygen supply
-Abundant myoglobin
-Smaller glycogen reserves
-Many mitochondria
-Continued contraction without fatigue.
-Also called: red muscle fibers, slow-twitch oxidative fibers, type I.
▫Intermediate Fibers- characteristics between fast and slow.
▪Muscle Performance and the Distribution of Muscle Fibers
8
▫Percentage of fast and slow fibers is genetically determined, presence of
intermediate fibers can changed resulting in athletic training.
▪Muscle Hypertrophy and Atrophy
▪Physical Conditioning
▫Anaerobic endurance-
▫Aerobic endurance-
Cardiac Muscle
▪Structural Characteristics of Cardiac Muscle Tissue
▪Functional Characteristics of Cardiac Muscle Tissue
Smooth Muscle
▪Structural Characteristics of Smooth Muscle
▪Functional Characteristics of Smooth Muscle Tissue:
▫Excitation-Contraction coupling
9
▫Length-Tension Relationships
-Plasticity
▫Control of Contraction
-multiunit smooth muscle cells-
-visceral smooth muscle cells-
10