What can transform chemical energy (ATP) into directed mechanical energy, which is capable of exerting force

1.Skeletal

2.Cardiac

3.Smooth

What cells are elongated and referred to as muscle fibers

What is packaged into skeletal muscles: organs that are attached to bones and skin

skeletal, striated and voluntary

What muscle fibers are longest of all muscle and have striations (stripes)

What is also called voluntary muscle; can be consciously controlled

Contract rapidly; tire easily; powerful

What muscle tissue is found only in the heart and makes up bulk of heart walls

Striated

Striated, involuntary

cannot be controlled consciously

What contracts at steady rate due to heart's own pacemaker, but nervous system can increase rate

What is found in the walls of hollow organs

Stomach, urinary bladder, and airways

not striated, involuntary

visceral, nonstraited, involuntary

What is this a characteristic of

Excitability, contractility, extensibility, elascity

(responsiveness): ability to receive and respond to stimuli

ability to shorten forcibly when stiumulated

ability to be stretched

ability to recoil to resting length

What these functions of

1. produce movement: responsible for all locomotion and manipulation

2. Example: walking, digesting, pumping blood

3. maintain posture and body position

4. stabilize joints

5. generate heat as they contact

What organ is made up of

Nerve and blood supply, connective tissue sheaths, and attachments

Each muscle receives a nerve, artery, and veins

Consciously controlled skeletal muscle has nerves supplying every fiber to control activity

Contracting muscle fibers require huge amounts of oxygen and nutrients

Also need waste products removed quickly

Each skeletal muscle, as well as each muscle fiber, is covered in connective tissue

Support cells and reinforce whole muscle

Sheaths from external to internal:

dense irregular connective tissue surrounding entire muscle; may blend with fascia

dense irregular connective tissue surrounding fascicles(groups of muscle fibers)

fine areolar connective tissue surrounding each muscle fiber

Muscles span joints and attach to bones

Muscles attach to bone in at least two places

Insertion

Origin

Attachments can be direct or indirect

attachment to moveable bone

attachment to immovable or less movable bone

epimysium fused to periosteum of bone or perichondrium of cartilage

connective tissue wrappings extend beyond muscle as roselike tendon or sheetlike aponeurosis

What are long, cylindrical cells that contain multiple nuclei

The plasma membrane of the muscle fiber

the cytoplasm of the muscle fiber

Contains many glycosomes for glycogen storage, as well as myoglobinfor O2 storage

myofibrils, sacroplasmic reticulum, t tubules

are densely packed, rodlike elements

Single muscle fiber can contain 1000s

Accounts for ~80% of muscle cell volume

What is striations, sarcomeres, myofilaments, molecular composition of myofilaments

stripes formed from repeating series of dark and light bands along length of each myofibril

In striation what is the A bands

What is the H zone in striations

What is the M line in striations

What is I bands in striations

What is z disc (line) in striations

Smallest contractile unit (functional unit) of muscle fiber

align end to end along myofibril, like boxcars of train

What is the H in sarcomere

What is the A in sarcomere

What is Z in sarcomere

What is the I in sarcomere

What is the M in sarcomere

orderly arrangement of actin and myosin myofilaments within sarcomere

thin filaments

extend across I band and partway in A band

Anchored to Z bands

thick filaments

Extend length of A band

Connected at M line

What is composed of the protein myosin that contains two heavy and four light polypeptide chains

what intertwine to form myosin tail

what form myosin globular head

when does heads link thick and thin filaments together forming cross bridges

What is offset from each other, resulting in staggered array of heads at different points along thick

What is composed of fibrous protein actin

What is a polypeptide made up of kidney-shaped G actin (globular) subunits

What are subunits that bears active sites for myosin head attachment during contraction

What subunits link together to form long, fibrous F actin (filamentous)

What strands twist together to form a thin filament

regulatory proteins bound to actin

is the most common and serious form of muscular dystrophies, muscle-destroying diseases that generally appear during childhood

Inherited as a sex-linked recessive disease, so almost exclusively in males (1 in 3600 births)

Appears between 2 and 7 years old when boy becomes clumsy and falls frequently

Disease progresses from extremities upward, finally affecting head, chest muscles, and cardiac muscle.

With supportive care, people can live into 30s and beyond

Caused by defective gene for dystrophin, a protein that links thin filaments to extracellular matrix and helps stabilize sarcolemma

What of DMD patients tear easily, allowing entry of excess calcium which damages contractile fibers

Inflammation follows and regenerative capacity is lost resulting in increased apoptosis of muscle cells and drop in muscle mass

What is a network of smooth endoplasmic reticulum tubules surrounding each myofibril

Most run longitudinally

Terminal cisterns form perpendicular cross channels at the A-I band junction

functions in regulation of intracellular Ca2+ levels

Stores and releases Ca2+

tube formed but he protrusion of sarcolemma deep into the cell interior

Increase muscle fiber’s surface area greatly

Lumen continuous with extracellular space

Allow electrical nerve transmissions to reach deep into interior of each muscle fiber

What penetrate the cell's interior at each A-I band junction between terminal cisterns

Triad

area formed from terminal cistern of one sarcomere, T tubule, and terminal cistern of neighboring sarcomere

What contains integral membrane proteins that protrude into intermembrane space (space between tubule and muscle fiber sarcolemma)

What proteins act as a voltage sensors that change shape in response to an electrical current

cistern membranes also have integral membrane proteins that protrude into intermembrane space

integral proteins control opening of calcium channels in SR cisterns

When does T tubule proteins change shape, causing SR proteins to change shape, causing release of calcium into cytoplasm what passes by for this to happen

the activation of cross bridges to generate force

Shortening occurs when tension generated by cross bridges on thin filaments exceeds forces opposing shortening

ends when cross bridges become inactive

In the relaxed state, thin and thick filaments overlap only slightly at ends of A band

states that during the contraction, thin filaments slide past thick filaments, causing actin and myosin to overlap more

Neither thick nor thin filaments change length, just overlap more

What happens when the nervous state stimulates a muscle fiber

What form and break several times, each time pulling thin filaments a little closer toward center of sarcomere in a ratcheting action

Causes shortening of muscle fiber

In cross bridge attachment z discs

In cross bridge attachment I bands

In cross bridge attachment Z disc

In cross bridge H zones

In cross bridge attachment A bands

Decision to move is activated by brain, signal is transmitted down spinal cord to motor neurons which then activate muscle fibers

Neurons and muscle cells are excitable cells capable of action potentials

Excitable cells can change resting membrane potential voltages

AP crosses from neuron to muscle cell via the neurotransmitter acetylcholine (ACh)

Play the major role in changing of membrane potentials

What are the two classes of ion channels

What is stimulated by somatic motor neurons

(long, threadlike extensions of motor neurons) travel from central nervous system to skeletal muscle

What divides into many branches as it enters muscl

What is separated by gel-filled spaced called synaptic cleft

Where are membrane-bound synaptic vesicles stored within

What does synaptic vesicles contain

Infoldings of sarcolemma called junctional folds contains millions of what

What consists of axon terminals, synaptic cleft, and junctional folds

How many steps must occur for skeletal muscle to contract

What are these steps of

1.Events at neuromuscular junction

2.Muscle fiber excitation

3.Excitation-contraction coupling

4.Cross bridge cycling

In neuromuscular junction where does AP arrive at

Which step of the big picture is this

Voltage-gated calcium channels open, and calcium enters the motor neuron

Which step of the big picture is this apart of

Calcium entry causes release of Ach neurotransmitter into the synaptic cleft

Which steps of the big picture is this

ACh diffuses across to ACh receptors (Na+ chemical gates) on sarcolemma

ACh binding to receptors, opens gates, allowing Na+ to enter resulting in end plate potential

Acetylcholinesterase degrades ACh

What can many toxins, drugs, and diseases interfere with

is an autoimmune disease characterized by drooping upper eyelids, difficulty swallowing and talking, and generalized muscle weakness

Resting sarcolemma is _____ meaning a voltage exists across membrane

The inside of cell is negative compared to outside

What is caused by changes in electrical changes

What are the three steps in the generation of an action potential across the sarcolemma

Where does this happen in

ACh released from the motor neuron binds to ACh receptors on sarcolemma

Where does this happen in

Causes chemically gated ion channels (ligands) on the sarcolemma to open

Where does this happen in

Na+ diffuses into the muscle fiber

Where does this happen in

Some K+ diffuses outward, but not much

Where does this happen in

Because Na+ diffuses in, the interior of the sarcolemma becomes less negative (more positive)

Where does this happen in

If the end plate potential causes enough change in membrane voltage to reach the critical level called threshold, the voltage-gated Na+ channels in membrane will open

Where does this happen in

A large influx of Na+ through channels into the cell triggers an AP that is unstoppable and will lead to muscle fiber contraction

Where does this happen in

The AP spreads across sarcolemma from one voltage-gated Na+ channel to next one in adjacent areas, causing that area to depolarize

Where does this happen in

Na+ voltage-gated channels close, and voltage-gated K+ channels open

Where does this happen in

K+ efflux out of cell rapidly brings cell back to initial resting membrane voltage

Where does this happen in

Refractory period: the muscle fiber cannot be stimulated for a specific amount of time, until repolarization is complete

Where does this happen in

Ionic conditions of the resting state are restored by Na+-K+ pump

Where does this happen in

Na+ that came into the cell is pumped back out, and K+that flowed outside is pumped back into the cell

Where does this happen in

Na+ that came into the cell is pumped back out, and K+that flowed outside is pumped back into the cell

Where does this happen in

AP is propagated along the sarcolemma and down into T tubules, where voltage-sensitive proteins in tubules stimulate Ca2+ release from the SR

the events that transmit AP along sarcolemma (excitation) are coupled to sliding of myofilaments (contraction)

Where does this happen in

Ca2+ release leads to contraction

The AP is brief and ends before contraction is seen

What happens at low intracellular Ca2+ concentration

What change, shape causing the sarcoplasmic reticulum to release Ca2+ to cytosol in T tubules

Ca2+ binds to troponin

Troponin changes shape and moves tropomyosin away from myosin-binding sites

Myosin heads are then allowed to bind to actin, forming cross bridge

Cycling is initiated, causing sarcomere shortening and muscle contraction

When nervous stimulation ceases, Ca2+is pumped back into SR, and contraction ends

What are these steps of

Cross bridge formation

Working (power) stroke

Cross bridge detachment

Cocking of the myosin head

the high-energy myosin head attaches to actin thin filament active sites

the myosin head pivots and pulls the thin filament toward M line

ATP attaches to the myosin head, causing the cross bridge to detach

energy from hydrolysis of ATP the myosin head into high-energy state

This energy will be used for power stroke in next cross bridge cycle

How long after death does muscles begin to stiffen

What increase because ATP is no longer being synthesized, so calcium cannot be pumped back into SR

Results in cross bridge formation

What is also needed for cross bridge detachment

Results in the myosin head staying bound to the actin, causing constant state of contraction

What stay contracted until the muscle proteins break down, causing myosin to release

What does the same muscle contraction principles apply to?

What produces muscle tension, the force exerted on load or object to be moved

may/ may not shorten muscle

the muscle shortens because muscle tension exceeds loads

there is no shortening as muscle tension increases but does not exceed the load

varies in response to stimuli of different frequencies and intensities

What is served by at least one motor nerve

Muscle fibers from what are spread throughout the whole muscle, so stimulation of a single motor unit causes only weak contraction of entire muscle

What is the simplest contraction resulting from a muscle fiber’s response to a single action potential from motor neuron

What contains axons of up to hundreds of motorneurons

What branch into terminals, each of which forms NMJ with single muscle fiber

What consists of the motor neuron and all muscle fibers (four to several hundred) it supplies

Which statement is true about the motor unit

Which statement is true in muscle twitch

What can a twitch be observed and recorded as

What is line recording contraction activity

What are these three phases of

Latent period, period of contraction, period of relaxation

events of excitation-contraction coupling

No muscle tension seen

cross bridge formation

tension increases

Ca2+ reentry into SR

Tension declines to zero

How fast does muscles contract

eye muscles contraction are rapid and brief, whereas larger, fleshy muscles (calf muscles) contract more slowly and hold it longer