Chapter 10 Flashcards
Type of muscle tissues
- Skeletal muscle tissue
- Cardiac muscle tissue
- Smooth muscle tissue
Type of muscle that are attached to the skeletal system and allow us to move; they are voluntary muscles,
controlled by nerves of the central nervous system
Skeletal Muscles
Six Functions of Skeletal Muscle Tissue
- Produce skeletal movement
- Maintain posture and body position
- Support soft tissues
- Guard entrances and exits
- Maintain body temperature
- Store nutrient reserves
three layers of connective tissues of muscles
- Epimysium (Exterior collagen tissue)
- Perimysium (Surrounds muscle fiber bundle)
- Endomysium (Surrounds muscle cells
cells that are very long and develop through fusion of mesodermal cells
(myoblasts)
Skeletal Muscle Cells
The cell membrane of a muscle fiber (cell)
sarcolemma
Structure that Transmit action potential through cell and allow entire muscle fiber to contract simultaneously
Transverse tubules (T tubules)
Lengthwise subdivisions within muscle fiber
Myofibrils
Types of myofilaments
Thin and thick filaments
Filament made of the protein actin
Thin filaments
Filament made of the protein myosin
Thick filaments
A membranous structure surrounding each myofibril that helps transmit action potential to myofibril
Sarcoplasmic Reticulum (SR)
formed by one T tubule and two terminal
cisternae and is found in the SR
Triad
Chambers found in SR that concentrate Ca2+ (via ion pumps) and release Ca2+ into sarcomeres to begin muscle
contraction
Cisternae
The basic contractile units of muscle
Sarcomeres
The center of the A band and is at midline of sarcomere
M line
The area around the M line that has thick filaments but no thin filaments
H Band
The densest, darkest area on a light micrograph where thick and thin filaments overlap
Zone of overlap
The centers of the I bands found at two ends of sarcomere
Z lines
strands of protein that reach from tips of thick filaments to the Z line and functions to stabilize the filaments
Titin
two twisted rows of globular G-actin
F-actin (filamentous actin)
The active sites on G-actin strands bind to?
myosin
Holds F-actin strands together
Nebulin
double strand that prevents actin–myosin interaction
Tropomyosin
globular protein that binds tropomyosin to G-actin and is controlled by Ca2+
Troponin
Filaments that Contain about 300 twisted myosin subunits and titin strands that recoil after stretching
Thick Filaments
What does the myosin heads do during contraction?
- Interact with actin filaments, forming crossbridges
* Pivot, producing motion
Theory stating that thin filaments of sarcomere slide toward M line,
alongside thick filaments; The width of A zone stays the same and Z lines move closer together
Sliding filament theory
Special intercellular connection between the
nervous system and skeletal muscle fiber that controls calcium ion release into the sarcoplasm
neuromuscular junction (NMJ)
What happens during excitation-contraction coupling?
- Action potential reaches a triad
- Releasing Ca2+
- Triggering contraction
- Requires myosin heads to be in “cocked” position
- Loaded by ATP energy
6 steps of the Contraction Cycle
- Contraction Cycle Begins
- Active-Site Exposure
- Cross-Bridge Formation
- Myosin Head Pivoting
- Cross-Bridge Detachment
- Myosin Reactivation
What happens during muscle relaxation?
- Ca2+ concentrations fall
- Ca2+ detaches from troponin
- Active sites are re-covered by tropomyosin
A fixed muscular contraction after death caused when:
• Ion pumps cease to function; ran out of ATP
• Calcium builds up in the sarcoplasm
Rigor Mortis
A single contraction or twitch lasts about?
7–100 msec
Period during twitches where the action potential moves through sarcolemma ,causing Ca2+ release
Latent period
Phase during twitches where calcium ions bind and tension builds to peak
Contraction phase
Phase during twitches where Ca2+ levels fall, active sites are covered and tension falls to
resting levels
Relaxation phase
A stair-step increase in twitch tension in which repeated stimulations occur immediately after relaxation
phase; it causes a series of contractions with increasing
tension
Treppe
Increasing tension or summation of twitches in which repeated stimulations occur before the end of relaxation
phase; it causes increasing tension or summation of
twitches
Wave summation
Condition where twitches reach maximum tensios and if rapid stimulation continues and muscle is not
allowed to relax, twitches reach maximum level of
tension
Incomplete tetanus
Condition that occurs when stimulation frequency is high enough, causing muscle
never begins to relax, and is in continuous
contraction
Complete tetanus
Contain hundreds of muscle fibers that contract at the same time and are controlled by a single motor neuron
Motor units in a skeletal muscle
2 Patterns of tension production
- Isotonic contraction
* Isometric contraction
Type of contraction where skeletal muscle changes length resulting in motion;
Isotonic Contraction
type of contraction where muscle shortens if muscle tension > load (resistance)
concentric contraction
type of contraction where muscle lengthens if muscle tension < load (resistance)
eccentric contraction
type of contraction where skeletal muscle develops tension, but is
prevented from changing length
Isometric Contraction
Is the primary energy source of resting muscles:
• Breaks down fatty acids
• Produces 34 ATP molecules per glucose molecule
Aerobic Metabolism
Is the primary energy source for peak muscular activity; it produces two ATP molecules per molecule of glucose and breaks down glucose from glycogen stored in skeletal
muscles
Glycolysis
Results of muscle Fatigue
• Depletion of metabolic reserves • Damage to sarcolemma and sarcoplasmic reticulum • Low pH (lactic acid) • Muscle exhaustion and pain
Term used when muscles can no longer perform a required activity
fatigued
The time required after exertion for muscles to
return to normal
Recovery Period
The removal and recycling of lactic acid by the liver where the liver converts lactate to pyruvate and glucose is released to recharge muscle glycogen
reserves
Cori Cycle
Occurs after exercise or other exertion which results to the body needing more oxygen than usual to normalize metabolic activities, which then causes heavy breathing
Oxygen Debt/excess postexercise oxygen
consumption (EPOC)
Three Major Types of Skeletal Muscle Fibers
- Fast fibers
- Slow fibers
- Intermediate fibers
Fibers that contract very quickly and have large diameter, large glycogen reserves, and few mitochondria; they have strong contractions, but fatigue quickly
Fast Fibers
Fibers that slow to contract, slow to fatigue have small diameter, more mitochondria and have high oxygen supply due to myoglobin (red pigment, binds oxygen)
Slow Fibers
Fibers that are mid-sized, have low myoglobin
and more capillaries than fast fibers, and are slower to fatigue
Intermediate Fibers
Muscle growth from heavy training
Muscle Hypertrophy
Term used for lack of muscle activity leading to reduces muscle size, tone, and power
Muscle Atrophy
cells that • Are small • Have a single nucleus • Have short, wide T tubules • Have no triads • Have SR with no terminal cisternae • Are aerobic (high in myoglobin, mitochondria) • Have intercalated discs
cardiac muscle cells
cardiocytes
Are specialized contact points between
cardiocytes
Intercalated Discs
Functions of intercalated discs
- Maintain structure
- Enhance molecular and electrical connections
- Conduct action potentials
Contraction without neural stimulation that are controlled by pacemaker cells
Automaticity
Characteristics of Smooth Muscle Cells
• Long, slender, and spindle shaped
• Have a single, central nucleus
• Have no T tubules, myofibrils, or sarcomeres
• Have no tendons or aponeuroses
• Have scattered myosin fibers
• Myosin fibers have more heads per thick filament
• Have thin filaments attached to dense bodies
• Dense bodies transmit contractions from cell to
cell
Where Ca2+ binds with in the smooth muscle tissue, which results to activation of myosin light–chain kinase
calmodulin
