What types of cells are found in muscle tissue? How are these cells specialized to carry out their function? What does BMI measure?
FUNCTIONSCONTRACTILE CELLS Pumping blood throughout the body Moving the skeletal system Passing food through the digestive system Specialized cell membrane and cytoskeleton that permit them to change their shape Cytoskeleton allows shortening in one or more planes (contraction) Laid out as sheets of muscle tissue that produce coordinated contractions
Blood Supply High energy needs Oxygen Remove metabolic wastes Glucose Electrolytes calcium From bones
Compares the amount of muscle mass with the body fat composition. A certain degree of leanness is known to reduce heart disease and metabolic disorders.
Contractile proteins: Proteins of the cytoskeleton involved in contraction (shortening) of muscle cells Appearance Voluntary or Involuntary Location
Uniform arrangement of contractile proteins Can see microscopically Stronger Contractions Randomized pattern of contractile proteins Cannot see microscopically Weaker contractions
Large degree of control Some unconsciously (breathing) Some contractions are intentional Contract without conscious control Jobs that are automatic or in conjunction with other organ systems Voluntary Involuntary
CardiacSkeletalSmooth Spindle or teardrop cells Fibers not visible Weak contractions that last a long time Linings of BVs Tubular organs Most involuntary Large cells with distinct striations Strong directional contractions Attach to bones and joints that produces body movement Most are voluntary Make up the heart Striated Connected by intercalated disks Involuntary
Briefly describe myogenesis. Briefly characterize the three types of muscle cells How do contractile proteins contribute to skeletal function? Why is the “intrinsic beat” of cardiac muscle cells significant? Why is “peristalsis” significant? Describe the relationship between muscle cells and muscle fibers
Muscle develops in mesoderm cells: myogenesis Stem cells form myoblasts Myoblasts move to other developing tissues to form the 3 muscle types Growth factors (chemicals that act as signals to initiate cell division & differentiation) by tissues give direction as to what type of muscle needs to form.
Cardiac SkeletalSmooth Lining of BV, digestive organs, urinary system, respiratory system Nonstriated Weak involuntary contractions can last for a long time Dilation and constriction of BV and tubular structures in respiratory system Peristalsis: laid in sheets in digestive system. Moves food & wastes through Provides movement Large cells with distinct striations Powerful contractile capabilities One cell is composed of several myoblasts that fuse into a muscle fiber—why so many nuclei? Each fiber stimulated by a motor nerve cell that controls several muscle fibers at once Form around large BV and form heart Strong contractions Not conscious control Have 2 nuclei per cell Cells are branched Communicate thru intercalated disks Intrinsic beat: all cardiac cells act in unison, coordinated thru intercalated disks
Cardiac Muscle: Branching, striated cells fused at plasma membranes. Skeletal Muscle: Long, striated cells with multiple nuclei Smooth Muscle: Long, spindle- shaped cells each with a single nucleus
How do contractile proteins contribute to skeletal function? Why is the “intrinsic beat” of cardiac muscle cells significant? Why is “peristalsis” significant? Describe the relationship between muscle cells and muscle fibers
Describe the basic structure of skeletal muscle cells Briefly summarize the various types of fibers found in a muscle cell Describe the relationship between myofibrils, muscle fibers, and fasciculi Why is a sarcomere called the “contractile unit” of the muscle?
Skeletal muscle fibers located in muscles epimysium Entire muscle surrounded by epimysium, a CT layer fascicles Subdivided into fiber bundles called fascicles (fasciculi) perimysium Fascilcles surrounded by perimysium, also CT Skeletal muscle fibers located in muscles epimysium Entire muscle surrounded by epimysium, a CT layer fascicles Subdivided into fiber bundles called fascicles (fasciculi) perimysium Fascilcles surrounded by perimysium, also CT
endomysium Portions of perimysium extend into the endomysium Thin layer of CT that covers each muscle fiber Muscle fiber Muscle fiber (bundle)= multinucleate cell
Sarcomere Sarcomere = basic (functional) contractile unit Z lines/discs Separated by each other by dark Z lines/discs Actinmyosin Actin & myosin slide past each other as the muscle contracts Contraction requires Ca 2+ and ATP ActinMyosin Sarcomere
Z-line/disc Z-line/disc – vertical protein bands that hold sarcomere to sarcolemma. I Bands Lighter areas of non-overlap between actin and myosin Contain the Z-lines. A Bands Dark Bands = A Bands Areas where some overlap occurs Striations = “Striations” on the slide Coincide with the length of myosin myofilaments. H-zone H-zone – light area within A-band
Transverse tubules sarcoplasmic reticulum Each myofibril is surrounded by network of tubes and storage sacs (Transverse tubules and sarcoplasmic reticulum) Releases Ca 2+ ions when stimulated by motor neuron Triggers contraction (more on this later…)
fasciculi Muscle FIBERS: grouped into bundles (fasciculi) = 1 cell! myofibrils Fibers contain myofibrils with: ACTIN ACTIN: thin myofilaments Also contain: Tropomyosin Troponin MYOSIN MYOSIN: thick myofilaments, with “swiveling” arm and head TITIN TITIN: elastic fibers that hold myosin in place, controlling stretch of sarcomere
How would a muscle appear to change microscopically during a contraction? What are the three stages of muscle contraction? What is the role of neurotransmitters during muscle contraction? Describe the ion concentrations found inside and outside a resting muscle cell Briefly describe the events that occur during the muscle contraction phase. What is the role of ATP during this phase? What must occur for a muscle cell to “fully” recover after a contraction? What occurs during “rigor mortis”?
Sarcomeres shorten, distance between z-lines reduced Thick and thin myofilaments overlap more during contraction 3 stages: Neural stimulation Muscle cell contraction Muscle cell relaxation
nerve impulse Stimulation of a muscle by a nerve impulse (motor nerve) is required before a muscle can shorten Neuromuscular junction Neuromuscular junction: point of contact b/w nerve ending and the muscle fiber it innervates. Motor unit: motor neuron + muscle cell
neurotransmitters Motor neuron releases neurotransmitters to stimulate a contraction Acetylcholine Acetylcholine (Ach) binds to receptors located on sarcolemma Changes transport proteins found in sarcolemma Alters transport of ions Normally, more Sodium (Na+) ions outside muscle cell, while Potassium (K+) higher inside Sodium/Potassium pumps maintain this unequal concentration Excitable condition
When stimulated, ion channels open, depolarizing the cell Na+ flows in, K+ out sarcoplasmic reticulum releases stored calcium Ca2+ travels to sarcomere, initiating muscle contraction phase
In the absence of Calcium ions… Troponin Tropomyosin Troponin “hat” sits on Tropomyosin filament These blocks access to the myosin head’s binding site on actin. Troponin Tropomyosin Ca 2+
When Calcium is released by the Sarcoplasmic reticulum it diffuses into the muscles binds to the troponin “hat” shifting both the troponin and tropomyosin filament
Myosin splits ATP and undergoes a conformational change into a high-energy state. The head of myosin binds to actin Forms a cross-bridge between the thick and thin filaments.
The energy stored by myosin is released ADP and phosphate released from myosin. The myosin molecule relaxes Causes rotation of the globular head This leads to the sliding of the filaments. This cycle continues until Ca 2+ ions gone (and stimulus stops)
ATP binds to cross bridge, causing cross bridge to disconnect from actin. Splitting of ATP leads to re-energizing/ repositioning of the cross bridge.
Complete contraction of muscle cell requires several cycles of neural stimulation and contraction phases Ca 2+ ions transported back to sarcoplasmic reticulum (req. ATP) When the calcium level decreases troponin locks tropomyosin back into the blocking position thin filament (actin) slides back to the resting state (when ATP binds to myosin head)
Relaxation phase occurs when no more neural stimulations are exciting the sarcolemma Na+/K+ pump returns ions to resting state Muscle cell remains in contracted, but pliable state Must be “stretched” back into position
1. ATP transfers its energy to the myosin cross bridge, which in turn energizes the power stroke. 2. ATP disconnects the myosin cross bridge from the binding site on actin. 3. ATP fuels the pump that actively transports calcium ions back into the sarcoplasmic reticulum.
In death… Calcium leaks out of sarcoplasmic reticulum into sarcomere Causes muscle tension = rigor mortis Muscle cell structures start breaking down, causing muscle to loosen (unless body becomes dehydrated)
Stores energy in muscle cells Collects energy from ATP, stores for long periods of time Transfers back to ATP when needed
Stored form of glucose Energy reserve for muscle action Continuous supply needed to produce ATP
Red pigment that stores oxygen for muscle cells “Grabs” oxygen from hemoglobin in blood High affinity for oxygen Allows cells to produce large amounts of ATP
What determines a muscle’s morphology? Distinguish between a muscle’s origin and insertion
Review the location of the various gross skeletal muscle types listed on page. 231 List, and briefly describe, the various terms that describe the muscle structures, patterns, and shapes
Parallel general-purpose muscles Sheets of muscle cells that run in the same direction Contractions for moving light loads over a long distance Pinnate Feather-pattern Great strength for moving heavy loads over a short distance Strong movements for the arms and legs
Muscle groupShapeFunction DeltoidTriangularPulling power TrapeziusTrapezoidPulling power RhomboideusDiamondHolding power for scapulae SerratusSaw-toothedShort movements of the arms, rib cage, and shoulders Biceps2 headsUpper arms Triceps3 headsUpper arms Quadriceps4 headsUpper legs SizeDescription MaximusLargest muscle in the group MinimusSmallest muscle in the group LongusLongest muscle in the group (arms and legs) BrevisShortest muscle in the group (arms and legs)
In words, briefly review the basic structure of a skeletal muscle What occurs to a muscle during atrophy? Hypertrophy?
A (blue line) B (Red line) FE CCD E A (blue line) B (Red line) CC G G EF
Atrophy Lose sarcomere proteins Causes muscle shrinkage Loss of contraction strength & size Can happen with a lack of neural stimulation Hypertrophy Regular use causes increased blood flow Increase in muscle diameter and thus muscle strength Genetic differences / variation in blood flow may cause an increase in sarcomere density without increase in muscle size
How are “graded effects” accomplished during a muscle contraction? Differentiate between strength and endurance. What is an antagonistic effect? Why are these essential to normal muscle function? List and briefly describe the various categories of muscle action.
Origin Origin – point of attachment of a muscle that remains fixed during contraction Insertion Insertion – point of attachment of a muscle connected to movable component on other end Shortening/contraction = moves insertion closer to origin
All muscle fibers contract with a particular strength when threshold neural stimulation reached How are muscles able to perform at different “powers”? Graded effects Graded effects can be accomplished by: Contracting more fascicles = more strength Muscles working together Endurance Endurance = producing contracting and relaxing fascicle groups
Strength Strength = ability to do more work Endurance Endurance = longer period of work
One muscle opposes or resists the action of another Weakens muscle strength Gravity can have antagonistic effect Essential! Pulls relaxed muscles back to original strength Cartilage can do this (in ribcage during breathing) Synergism Synergism = muscles work together
Muscle Action MovementAntagonistic Toward…. AbductorAway from midlineAdductors AdductorToward the midlineAbductors DepressorDownward movementLevator ExtensorIncrease angle of jointFlexor Decrease angle of jointExtensor LevatorUpward movementDepressor PronatorTurn palm downSupinator RotatorTurn along longitudinal axisNone SphincterDecrease size of openingNone-attached to skin or connective tissue SupinatorTurn palm upPronator TensorPosture, make body part more rigid, tense Many
Another way to define muscle action Isotonic: muscle is actively shortening or lengthening. Lifting/lowering weights Isometric: muscle remains steady in length, undergoing indistinguishable pulses of shortening and lengthening Pushing against something too heavy to move
Differentiate between muscle strains and sprains Differentiate between spasms and cramps of muscles How are rigid and flaccid paralysis different? What causes tetanus? Review the various myopathies listed on p. 242. Make a chart/concept map to summarize the major characteristics of each.
Strain Overworking muscle Pain, swelling in: Fascia Joints Ligaments Tendons Due to tearing of muscle/tendon fibers Nerves stretched/swollen Sprain More severe Sudden/violent stress on joint/muscle Causes tearing: Ligament Muscle Tendon Damage to blood vessels
Spasm = involuntary, abnormal contractions of a muscle/group Many causes Often associated with pain Cramps = painful contraction of muscle Extreme exertion can cause May develop while working in cold Poisons, bacterial infections
Paralysis = complete failure of muscle function Caused by muscle stiffness? Rigid Lack of muscle contraction? Flaccid Many causes (infection, injury, degeneration)
Soil bacteria (Clostridium tetani)infect nervous system Produce poisons that block nerve signals at neuromuscular junction, cause rigid paralysis (severe muscle spasms). Can cause muscle tears/spinal fractures if severe Do you have your tetanus “shot”?
Reading “Aging of the Musculature” Bring textbook… Make concept map of pathology and aging sections (like the one I made for you last time) Try to think about “groupings” you could use to make a web “Overwork” “Trauma” “Abnormal muscle control” Etc…
What can cause cachexia? Why do muscles require a high protein turnover? What is the role of IGF-1 in muscle health?