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Chapter 9
Muscles and Muscle Tissue
105
Anatomy
Undergraduate 2
11/02/2011

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Term
Three types of muscle tissue
Definition
Skeletal, cardiac, and smooth
Term
Differences between types of muscle tissue
Definition
Structure, location, function, means of activation
Term
Skeletal and smooth muscle cells are elongated and are called _____
Definition
Muscle fibers.
Term
Muscle contraction depends on two kind of myofilaments, _____
Definition
actin and myosin
Term
Sarcolemma
Definition
muscle plasma membrane
Term
Sarcoplasm
Definition
cytoplasm of a muscle cell
Term
prefixes
Definition
myo, mys, and sacro all refer to muscles
Term
Skeletal Muscle Tissue: Basics
Definition
Packaged in skeletal muscles that attach to and cover the bony skeleton. Has obvious stripes called striations. Controlled voluntarily. Contracts rapidly but tires easily. Response for overall body motility. Extremely adaptable and can exert forces ranging from a fraction of an ounce to over 70 lbs
Term
Cardiac Muscle Tissue: Basics
Definition
Occurs only in the heart. Striated like skeletal muscle but is not voluntary. Contracts at a fairly steady rate set by the heart's pacemaker. Neural controls allow the heart to respond to changes in bodily needs
Term
Smooth Muscle Tissue: Basics
Definition
Found in the walls of hollow visceral organs, such as the stomach, urinary bladder, and respiratory passages. Forces food and other substances through internal body channels. It is not striated and is involuntary
Term
Functional characteristics of Muscle Tissue
Definition
Excitability/Irritability, Contractility, Extensibility, Elasticity
Term
Functional Characteristics of Muscle Tissue: Excitability/Irritability
Definition
The ability to receive and respond to stimuli
Term
Functional Characteristics of Muscle Tissue: Contractility
Definition
The ability to shorten forcibly
Term
Functional Characteristics of Muscle Tissue: Extensibility
Definition
The ability to be stretched or extended
Term
Functional Characteristics of Muscle Tissue: Elasticity
Definition
The ability to recoil and resume the original resting length
Term
Skeletal muscle function
Definition
Responsible for all locomotion
Term
Cardiac muscle function
Definition
responsible for coursing the blood through the body
Term
Smooth muscle function
Definition
helps maintain blood pressure, and squeezes or propels substances (food,feces) through organs
Term
General muscle function
Definition
Maintain posture, stabilize joints, and generate heat
Term
Skeletal muscle composition
Definition
Muscle tissue, blood vessels, nerve fibers, and connective tissue
Term
Three connective tissue sheaths
Definition
Endomysium, Perimysium, Epimysium
Term
Endomysium
Definition
Fine sheath of connective tissue composed of reticular fibers surrounding each muscle fiber
Term
Perimysium
Definition
Fibrous connective tissue that surrounds groups of muscle fibers called fasicles
Term
Epimysium
Definition
an overcoat of dense regular connective tissue that surrounds the entire muscle
Term
Skeletal Muscle: Nerve and Blood Supply
Definition
Each muscle is served by one nerve, an artery , and one or more veins.
Each skeletal muscle fiber is supplied with a nerve ending that controls contraction
Contracting fibers require continuous delivery of oxygen and nutrients via arteries
Wastes must be removed via veins
Term
Skeletal Muscle: Attachments
Definition
Most skeletal muscles span joints and are attached to bone in at least two places
When muscles contract the movable bone, the muscle's insertion moves toward the immovable bone, the muscle's origin
Term
How muscles attach
Definition
Directly or Indirectly
Term
Direct Muscle Attachment
Definition
epimysium of the muscle is fused to the periosteum of the bone
Term
Indirectly
Definition
connective tissue wrappings extend beyond the muscle as a tendon or aponeurosis
Term
Microscopic Anatomy of a Skeletal Muscle Fiber
Definition
Each fiber is a long, cylindrical cell with multiple nuclei just beneath the sarcolemma.
Fibers are to 10 to 100 um in diameter, and up to hundreds of centimeters long
Sarcoplasm has a unique oxygen-binding protein called myoglobin
Fibers contain the usual organelles, myofibrils, sarcoplasmic reticulum, and T tubules
Term
Myofibrils
Definition
Densely packed, rodlike contractile elements. Make up most of the muscle volume. Arrangemet of myofibrils with a fiber is such that perfect aligned repeating series of dark A band and light I bands is evident
Term
Sarcomeres
Definition
Smallest contractile unit of a muscle. The region of a myofibril between two successive Z discs. Composed of myofialments made up of contractile proteins.
Term
Two types of myofilaments
Definition
Thick and thin
Term
A Band: What is it?
Definition
area of myosin/actin overlap
Term
A Band composed of what?
Definition
H-Zone. M-line
Term
I band: what is it?
Definition
area of actin filaments - no myosin
Term
I band: composed of what?
Definition
Z-Disc
Term
Myofilaments: Banding pattern
Definition
Thick (myosin) filaments - extend the entire length of an A band
Thin (actin) filaments - extend across the I band and partway into the A band
Z-disc: coin-shaped sheet of proteins (connectins) that anchors the thin filaments and connects myofibrils to one another
Term
Actin: Thick or thin filament?
Definition
Thin
Term
Myosin: Thick or thin filaments?
Definition
Thick filaments
Term
Do thin filaments overlap thick filaments in the lighter H zone?
Definition
No
Term
Ultrastructure of Myofilaments: Thick Filaments
Definition
Thick filaments are are composed of the protein myosin. Each myosin molecule has a rod-like tail and two globular heads.
Term
Myosin tails
Definition
two interwoven, heavy polypeptide chains
Term
Myosin Heads
Definition
Two, smaller, light polypeptide chains called cross bridges
Term
Ultrastructure of Myofilaments: Thin filaments
Definition
Thin filaments are chiefly composed of the protein actin. Each actin molecule is a helical polymer of globular subunits called G actin. The subunits contain the active sites to which myosin heads attach during contracting (actin/myosin cross bridge)
Tropmyosin and troponin are regulatory subunites bounds to actin
Term
Sarcoplasmic reticulum
Definition
An elaborate, smooth endoplasmic reticulum that most runs longitudinally and surrounds each myofibril
Paired terminal cisternae form perpendicular cross channels
Functions in the regulation of intracellular calcium levels
Term
Sarcoplasmic Reticulum
Definition
Elongated tubes called T tubules penetrate into the cell's interior at each A band-I band junction. T Tubules associate with the paired terminal cisternae (pools) to form triads
Term
T tubules
Definition
Continuous with the sarcolemma
Conduct impulses to the deepest regions of the muscle
These impulses signal for the release of Ca2+ from adjacent terminal cisternae (pools)
Term
Triad relationships
Definition
T tubules and SR provide tightly linked signals for muscle contraction. A double zipper of integral membrane proteins protrudes into the intermembrane space. T tubules proteins act as voltage sensors
SR foot proteins are receptros that regulate Ca2+ release from the SR cisternae
Term
Sliding Filament Model of Contraction - Short Story
Definition
Thin filaments slide past the thick ones so that the action and myosin filaments overlap to a greater degree.
In the relaxed state, thin and thick filaments overlap only slightly
Upon stimulation, myosin heads bind to actin and sliding begins.
Each myosin head binds and detaches several times during contraction, acting like a ratchet to generate tension and propel the thin filaments to the center of the sarcomere.
As this event occurs throughout the sarcomeres, the muscle shortens
Term
Skeletal Muscle Contraction: In order to contract a skeletal muscle must...
Definition
Be stiumalted by a nerve ending, propagate an electrical current, or action potential, along its sarcolemma, have a rise in intracellular Ca2+ levels, the final trigger for contraction.

Linking the electrical signal to the contraction is excitation-contraction coupling
Term
Nerve Stimulus of a Muscle Cell
Definition
Skeletal muscles are stimulated by motor neurons of the somatic nervous system. Axons of these neurons travel in nerves to muscle cells. Axons of motor neurons branch profusely as they enter muscles. Each axonal branch form a neuromuscular junction with a single muscle fiber
Term
Neuromuscular junction: Formation
Definition
Axonal endings which have small membranous sacs (synaptic vesicles) that contain the neurotransmitter acetylcholine (ACh). The motor end plate of a muscle, which is a specific part of the sarcolemma that contains ACh receptors and helps form the junction
Term
Synaptic cleft
Definition
Space between axonal ends and muscle fibers of the neuromuscular junction
Term
Synaptic cleft
Definition
Space between axonal ends and muscle fibers of the neuromuscular junction
Term
When a nerve impulse reaches the end of an axon at the the neuromuscular junction....: what happens?
Definition
Voltage-regulated calcium channels open and allow Ca2+ to enter the axon.
Ca2+ inside the axon terminal causes axonal vesicles to fuse with the axonal membrane
This fusion release ACh into the synaptic cleft via exocytosis
ACh diffuses across the synaptic cleft to ACh receptors on the sarcolemma
Binding of ACh to its receptors initiates an action potential in the muscle
Term
Role of ACh
Definition
Binds its receptors at the motor end plate
Binding opens chemically (ligand) gated channels
Na+ and K+ diffuse out and the interior of the sarcolemma becomes less negative
Term
Destruction of ACh
Definition
ACh bound to ACh receptors is quickly destroyed by the enzyme acetycholinesterase
This destruction prevents continued muscle contraction in the absence of additional stimuli
Term
Organizatonal level of muscle: Surface to Deep
Definition
Organ > Fasicle > Cell > Myofibril/Fibril > Sarcomere > Myofilament/Filament
Term
Muscle Organ: Description
Definition
Consists of hundreds to thousands of muscle cells, plus, connective tissue wrappings, blood vessels, and nerve fibers
Term
Muscle organ: Connective tissue wrappings
Definition
Covered externally by the epimysium
Term
Fascicle: Description
Definition
Discrete bundle of muscle cells, segregated from the rest of the muscle by a connective tissue sheath.
Term
Fascicle: Connective tissue wrappings
Definition
Surrounded by a perimysium
Term
Muscle fiber (Cell): Description
Definition
Elongated multinucleate cell; has a banded (striated) appearance
Term
Muscle fiber (Cell): Connective Tissue Wrappings
Definition
Surrounded by the endoysium
Term
Myofibril/fibirle: description
Definition
complex organelle composed of bundles of myofilaments. rodlike contractile elements; myofibrils occupy most of the muscle cell volume; composed of sarcomeres arranged end to end; appears banded, and bands of adjacent myofibrils are aligned
Term
Sarcomere
Definition
a segment of myofibril. The contractile unit, composed of myofilaments made up of contractile proteins
Term
Myofilament/Filament
Definition
Extended macromolecular structure. contractile myofilaments are of two types - thick and thin. The thick filaments contain bundled myosin molecules; the thin filaments contain actin molecules; the sliding of the thin filaments past the thick filaments produces muscle shortening. Elastic filaments maintain the organization of the A band and provide for elastic recoil when muscle contraction ends
Term
Action potential
Definition
A transient depolarization event that includes polarity reversal of a sarcolemma (or nerve cell membrane) and the propagation of an action potential along the membrane
Term
Depolarization
Definition
Initially, this is a local electrical event called end plate potential
Later, it ignites an action potential that spreads in all direction across the sarcolemma
Term
Excitation-Contraction Coupling: Once generated, the action potential...
Definition
Is propagated along the sarcolemma.
Travels down the T tubules
Triggers Ca2_ release from terminal cisternae
Term
Ca2+ release from terminal cisternae causes...
Definition
Ca2+ binds to troponin
Term
Ca2+ binding to troponin causes...
Definition
The clocking action of tropomyosin to cease
Actin active binding sites to be exposed
Term
Excitation-Contraction Coupling: Post Ca2+ binding...
Definition
Myosin cross bridges alternately attach and detach
Thin filaments move toward the center of the sarcomere
Hydrolysis of ATP powers this cycling process
Ca2+ is removed into the SR, tropomyosin blockage is restored, and the muscle fiber relaxes
Term
Excitation-Contraction Coupling Summary: Step 1
Definition
Action potential generated and propagated along sarcomere to T-tubules
Term
Excitation-Contraction Coupling Summary: Step 2
Definition
Action potential triggers Ca2+ release
Term
Excitation-Contraction Coupling Summary: Step 3
Definition
Ca2+ bind to troponin; blocking action of tropomyosin released
Term
Excitation-Contraction Coupling Summary: Step 4
Definition
Contraction via crossbrdige formation; ATP hydrolysis
Term
Excitation-Contraction Coupling Summary: Step 5
Definition
Removal of Ca2+ by active transport
Term
Excitation-Contraction Coupling Summary: Step 6
Definition
Tropomyosin blockage restored; contraction ends
Term
Sequential Events of Contraction
Definition
Cross bridge formation: myosin cross bridge attaches to actin filament
Working (power) stroke: myosin head pivots and pulls actin filament towards M line
Cross bridge detachment: ATP attaches to myosin head and the cross bridge detaches
"Cocking" of the myosin head - energy from hydrolysis of ATP cocks the myosin head into the high-energy state
Term
Contraction of Skeletal Muscle Fibers
Definition
Contraction - refers to the activation of myosin's cross bridges (Forge-generating sites)
Shortening occurs when the tension generated by the cross bridge exceeds forces opposing shortening
Contraction ends when cross bridges become inactive, the tension generated declines and relaxation is induced
Term
Contraction of Skeletal Muscle (organ level)
Definition
Similar to cell.
Term
Two types of muscle contractions
Definition
Isometric and Isotonic
Term
Isometric contraction
Definition
increasing muscle tension (muscle does not shorten during contraction)
Term
Isotonic contraction
Definition
decreasing muscle length (muscle shortend during contraction)
Term
Motor Unit: What is it?
Definition
The nerve-muscle functional unit. A motor neuron and all the muscle fibers it supplies
The number of fibers per motor unit can vary from four to several hundred
Term
Motor Unit: Small motor units
Definition
For muscles that control fine movements (fingers, eyes)
Term
Motor Unit: Large motor units
Definition
For large weight-bearing muscles (thighs, hips) have large motor units
Muscle fibers from a motor unit are spread throughout the muscle; therefore, contraction of a single motor unit causes weak contraction of the entire muscle
Term
Muscle Twitch: What is it?
Definition
the response of a muscle to a single, brief threshold stimulus
Term
Muscle Twitch: Three phases
Definition
Latent period, Period of contraction, Period of relaxation
Term
Muscle Twitch: Latent period
Definition
Events of excitation-contraction coupling
Term
Muscle Twitch: Period of contraction
Definition
cross bridge formation; tension increases
Term
Muscle Twitch: Period of relaxation
Definition
Ca2+ reentry into the SR; tension declines to zero
Term
Muscle Twitch phases: Timing
Definition
Shortest to Longest
Latent > Contraction > Relaxation
Term
Muscle fibers type
Definition
Type I, Type IIa, Type IIb
Term
Type I muscle fiber
Definition
Red muscle, slow, marathon
Term
Type IIa muscle fiber
Definition
Red muscle, fast, middle distance
Term
Type IIb muscle fiber
Definition
White muscle, fast, sprint
Term
Type I muscle fiber characteristics
Definition
Do not get fatigued, can be used for hours
High mitochondrial and myoglobin count
High capillary desnity
Major fuel - tryglycerides
Term
Type IIa muscle fibers characteristics
Definition
Can be fatigued but not to a great extent
Major fuel - creatine phosphate and glycogen
Term
Type IIb muscle fibers characteristics
Definition
Major fuel - creatine phosphate and glycogen
Opposite of Type I
Term
Muscle Fatigue: What is it?
Definition
Physiological inability to contract
Term
Muscle Fatigue: Occurs when?
Definition
Ionic imbalances (K+, Ca2+, P) interfere with E-C coupling
Prolonged exercise damages the SR and interferes with Ca2+ regulation and release
Total lack of ATP occurs rarely, during states of continous contractions, and causes contractures
Term
Oxygen deficit
Definition
Extra O2 needed after exercise for replenishment of oxygen reserves, glycogen stores, ATP and CP reserves. Conversion of lactic acid to pyruvic acid, glucose, and glycogen.
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