Muscles, Ch 10 Flashcards
Muscle tissue consists of what?
Muscle cells, called myocytes
The surrounding ECM, called the endomysium
What are the three types of muscle tissue?
Striated skeletal and cardiac muscle
Smooth muscle
Which muscle tissue is made up of long, multinucleated cells that are arranged parallel to one another. Some are quite long, extending nearly the entire length of the muscle.
Skeletal muscle tissue (muscle fibers)
Mostly found attached by conn tissue to the skeleton, where their contraction produces movement
Voluntary tissue
Muscle tissue with cells that are shorter and wider, are branched, and generally have only one or two nuclei.
Cardiac muscle tissue
Involuntary type of tissue
Explain intercalated disks.
Found in cardiac tissue. Contain gap junctions and modified tight junctions that unite muscle cells and permit them to coordinate contraction.
Muscle tissue with cells that are long and flattened with two pointed ends (spindle-shaped) and with a centrally located, oval nucleus. Line nearly every hollow organ, found in eyes, skin, ducts of some glands.
Smooth muscle cells
Linked by gap junctions in their plasma membranes.
Involuntary tissue
What are the five properties of muscle cells?
Contractility Excitability Conductivity Extensibility Elasticity
The ability of proteins within muscle cells to draw together.
Contractility
Responsiveness in the presence of various stimuli, which might include chemical signals from various nervous or endocrine systems, mechanic stretch signals, and local electrical signals.
Excitability
The ability of a muscle cell to let the electrical charges move across the entire length of the plasma membrane.
Conductivity
The ability of muscle cells to be stretched up to three times their resting length without damage.
Extensibility
The ability of muscle cells to return to their original shape when stretched.
Elasticity
Contains cytosol and all of the organelles in a muscle cell, including cylindrical myofibrils.
Sarcoplasm
Part of a muscle cell composed of a phospholipid bilayer with multiple specialized integral and peripheral proteins.
Sarcolemma
Essentially bundles of specialized proteins, especially those involved in muscle contraction. Most abundant organelle in the sarcoplasm. Make up 50-80% of a muscle cell’s volume.
Myofibrils
A modified smooth endoplasmic reticulum that forms weblike structure surrounding each myofibril. Primary function is storage and release of calcium ions, activities vital to muscle contraction and relaxation.
Sarcoplasmic reticulum
Varies in the three types of muscle tissue.
Form a tunnel-like network within the skeletal muscle fiber and are continuous with the exterior of the cell, making them full of ECF.
Transverse (T)-tubules
Sarcolemma of skeletal muscle fiber
Enlarged portions of the SR that flank each side of a T-tubule. The combination of these and a T-tubule is known as a triad.
Terminal cisternae
A myofibril is composed of hundreds to thousands of protein bundles called?
Myofilaments
What three types of proteins make up myofilaments?
Contractile
Regulatory
Structural
What do contractile proteins in myofilaments do?
Produce tension
What do regulatory proteins in myofilaments do?
Control when the muscle fiber can contract
What do structural proteins in the myofilaments do?
Hold the myofilaments in their proper places and ensure the structural stability of the myofibril and the muscle fiber.
Filaments with the largest diameter, composed of many molecules of myosin. Clusters of myosin heads are at each end, with tails in the middle. Titin runs through them for strength.
Thick filaments
Contractile protein, with globular heads and two intertwining polypeptide chains making a tail. Neck is flexible where it meets the tail at the hinge.
Myosin
A filament that is made up of both contractile and regulatory proteins. What are they?
Thin filaments
Actin
Tropomyosin
Troponin
Contractile protein that helps to make up the thin filament. Bead-shaped with an active site that can bind to a myosin head. Appears as two intertwining strands in the functional thin filament.
Actin
The long, roselike regulatory protein that helps make up the thin filament. Spirals around the two actin strands so that at rest, it covers the active sites on actin.
Tropomyosin
Regulatory protein that is smaller and globular. it helps to hold the tropomyosin in place.
Troponin
The thinnest type of filament, composed of a single massive structural protein called titin. Holds the thick filaments in place, resists excessive stretching, and provides elasticity.
Elastic filament
Multiple skeletal muscle fibers together with the surrounding endomysium. Bundles of these together make up a skeletal muscle.
Fascicle
A layer of connective tissue that surrounds the fascicle.
Layer of connective tissue that surrounds the entire muscle.
Perimysium
Epimysium
The zone where tension is generated during a muscle contraction. The alternating light and dark bands that are produced by the repeating arrangement of think and thick filaments.
Zone of overlap.
The light region of a striation that contains only thin filaments, which allows more light to pass through them.
I band
The dark region of a striation which contains thick filaments. These block more light, making the band appear darker.
A band
Region of the striation with both thick and thin filaments in the outer portion, and only thick filaments in the middle. What is the middle area?
H zone
Consists of structural proteins that hold the thick filaments in place and serve as an anchoring point for the elastic filaments.
M line
Dark line in the I bands. Composed of structural proteins that anchor the thin filaments in place and to one another, act as an attachment point for elastic filaments, and attach myofibrils to one another across the muscle fiber.
Z-disc
The functional unit of contraction, where muscle tension is produced. The section of a myofibril that extends from one Z-disc to the next disc. Each includes a full A band and half of two I bands.
Sarcomere
The interaction of the thin and thick filaments during muscle contraction and relaxation.
Sliding-filament mechanism
Which zones narrow and which remain unchanged during contraction?
The I bands and H zone narrow while the A band remains unchanged.
The electrical gradient of a cell’s membrane is called this, because when the barrier is removed the ions follow their gradients, creating a flow of electrical charges, with the potential energy becoming kinetic energy.
Electrical potential
A difference in electrical potential between two points. The size indicates the size of the potential.
Voltage
The electrical potential across a cell’s plasma membrane.
The electrical potential across a sarcolemma in a muscle fiber at rest.
Membrane potential
Resting membrane potential
The pump that maintains the concentration gradients of sodium and potassium ions across the sarcolemma, using energy from ATP hydrolysis, or splitting.
Na+/K+ ATPase pump
How does the Na+/K+ ATPase pump work?
It moves 3 Na ions out of the cell, making the concentration Na low in the cytosol and high in the ECF. It also moves 2 K ions into the cell, making the concentration of K ions high in the cytosol and low in the ECF.
A quick, temporary change in the membrane potential in a single region of the plasma membrane. During this, the membrane potential goes from its negative resting value to a more positive one and back again.
Action potential
They are generated by the opening and closing of protein channels in the membrane that control the Na/K pump.
A single motor neuron communicates with many muscle fibers; each connection is a synapse. The synapse of a motor neuron with a muscle fiber and what its three parts are?
Neuromuscular junction, NMJ.
Axon terminal
Synaptic cleft
Motor end plate
A long cytoplasmic extension that is extended from the motor neuron to the muscle fiber. The end swells to form what?
Axon
Axon terminal/synaptic bulb that contains vesicles.
The narrow space between the axon terminal and the muscle fiber into which ACh is released. It’s filled with collagen fibers and an extra-cellular gel that anchors the neuron in place, as well as enzymes that break down ACh.
Synaptic cleft
A specialized region of the sarcolemma, whose folded surface contains many receptors, ligand-gated ion channels, for ACh, the ligand.
Motor end plate
Phase that involves the transmission of a signal from the motor neuron to the sarcolemma of a muscle fiber. Occurs at the neuromuscular junction.
Excitation phase
Almost immediately degrades and inactivates the ACh that is released from the synaptic vesicles in the cleft.
Acetylcholinesterase
Phase in which the end-plate potential leads to an action potential in the sarcolemma, which in turn triggers events that result in contraction.
Excitation-contraction coupling
Phase in which the myofilaments slide past one another.
Contraction phase
A myosin head bound to an actin molecule. When this occurs a cycle is initiated that leads to the sliding of myofilaments.
Crossbridge
ACh release stops and the remaining ACh in the synaptic cleft is broken down. The calcium ion concentration in the cytosol returns to resting level.
Muscle relaxation
How does rigor mortis occur after death?
Pumps that drive Ca ions back into the SR no longer have ATP. Ca ions remain the cytosol, where they bind with troponin and initiate a muscle contraction. The fibers can’t relax w/o ATP, and myosin can’t detach from actin. Remain spasm until proteins break down, 48-72 hrs.
Creatine phosphate with the help of the enzyme creatine kinase donates a phosphate group to ADP, producing ATP. Additional 10 secs of max muscle activity.
Creatine phosphate reaction
A series of reactions that take place in the cytosol, wherein glucose is broken down to produce two ATP per molecule of glucose. 30-40 secs of sustained muscle contraction.
Glycolysis
Glycolytic or anaerobic catabolism
In glycolysis, if oxygen is abundant this compound enters the mitochondria for oxidative catabolism. If oxygen is not available, the compound is converted into two molecules of this other compound.
Pyruvate
Lactic acid
Electrons are removed from carbon-based molecules, and then the energy is used to fuel synthesis of ATP. Produces more ATP than glycolysis. Is the predominant energy source after 1 min of activity
Oxidative or aerobic catabolism
Protein found in the cytosol that binds to oxygen that has diffused into the muscle fiber from the ECF and releases it as the available oxygen is depleted by mitochondria performing oxidative catabolism.
Myoglobin
The principle that says the number of cross bridges depends on the length of the sarcomere prior to contraction. The optimal length is that at which the most crossbridges can form.
Length-tension relationship
Muscle fibers with high myosin ATPase activity that proceed rapidly through contraction cycles.
Fast-twitch fibers
Fibers with low myosin ATPase activity that proceed through contraction cycles more slowly.
Slow-twitch fibers
Slow-twitch fibers that contract more slowly and less forcefully, maintaining periods of contraction. Continual oxidative generation of large quantities of ATP. High myoglobin content makes them red.
Type I fibers
Fast-twitch fibers that are often larger in diameter and contract more quickly, but fatigue quickly. Rely primarily on glycolytic energy sources, and have less myoglobin. Three subtypes?
Type II fibers
Fast oxidative glycolytic
Fast oxidative
Fast glycolytic
A single motor neuron with the muscle fibers it innervates. When the neuron fires an action potential all of the fibers within this respond and produce about the same amount of tension.
Motor unit
As greater force is needed, more motor units are activated. Slow motor units are activated first, and then fast motor units if additional tension is needed. This is called?
Recruitment
The small degree of tension a muscle produces even at rest, due to the involuntary activation of motor units by the rain and spinal chord. Maintains erect posture, stabilizes joints, generates heat, keeps muscle ready
Muscle tone
The same muscle tension but changing length.
The same length but changing tension.
Isotonic
Isometric
The force generated by the muscle is greater than that of the external load.
Isotonic concentric contraction
Miometric
The force generated by the muscle is less than that of the external load. The muscle lengthens as tension is produced. Requires the greatest amount of tension and produces the greatest amount of force.
Isotonic eccentric contraction
Pliometric
The length of the muscle doesn’t change in this contraction.
Isometric contractions
Training with a large increase in the frequency of motor unit activation and a moderate increase in force production. More repetitions with lighter weight.
Endurance training
Muscle fiber has increased amounts of oxidative enzymes, more mitochondria, and more blood vessels. Increased resistance to fatigue.
Training with a moderate increase in the frequency of motor unit activation and a large increase in force production. Fewer repetitions with heavier weight.
Resistance training
Hypertrophy, fewer mitochondiral proteins and less blood supply to the muscle.
What happens from disuse and atrophy of the muscles?
The diameter of the muscle fiber decreases due to the loss go myofibrils. The amount of oxidative enzymes decreases and the fiber has a lower capacity for oxidative catabolism.
The inability to maintain a given level of intensity of a particular exercise. Consists of what?
Muscular fatigue Depletion of key metabolites Decreased availability of oxygen to muscle fibers Accumulation of certain chemicals Environmental conditions
The persisting increased rate of breathing when the body goes through the recovery period after exercise. To return to homeostasis the body needs to do what?
Excess postexercise oxygen consumption.
Heat dissipation
Restoration of intracellular and extracellular ion contraptions.
Correction of blood pH.
Proteins in smooth muscle that the obliquely arranged actin filaments are anchored to. From each of these radiates several thin filaments surrounding one thick filament.
Dense bodies
What does smooth muscle lack? What do they have?
Lack striations, sarcomeres, troponin, motor end plates, T-tubules, less SR.
Have opposite facing myosin heads, which are along the whole length of the thick filament.
Cells with unstable membrane potentials that cause them to spontaneously depolarize in a rhythmic fashion. Responsible for the waves of contraction in the stomach and intestines.
Pacemaker cells.
The state of smooth muscle wherein the cell maintains tension while consuming very little ATP. Important to maintain energy-effiecieny in things like sphincters that have to stay closed.
Latch state
The predominant type of smooth muscle found in nearly all hollow organs. Contracts in a coordinated wave as a single unit, as the cells are linked electrically via gap junctions.
Single-unit smooth muscle
Responds to multiple types of stimulation
Smooth muscle found in locations such as the uterus, eye, and goosebumps. Individual muscle cells not joined by gap junctions, which allows each cell to contract independently, permitting precise control.
Multi-unit smooth muscle
Responds primarily to nerve stimulation
