Muscles

What type of proteins contribute to the alignment, stability, extensible of myofibrils? Examples.

Structural; Titin, myorresin, nebulin, dystrophin.

What is located superficial to the fascia?

SubQ or hypodermis which is made of areolar/adipose tissue.

What is suspended within the cytosol of each end bulb of the motor neuron axon?

Synaptic vesicles containing acetylcholine (ACh)

How is the sacroplasmic reticulum of skeletal fibers arranged?

Terminal cisterns butt against the tubules from both sides forming a triad (3)

What is extensibility?

The ability of muscle to stretch without being damaged.

What is the sarcomere of muscle?

The arrangement of filaments in myofibrils.

What is the Aerobic cellular respiration that muscles use to metabolize energy? Briefly describe process/product.

The citric acid or kreb's cycle and ETC in the mitochondria are utilized to turn pyruvic acid into ATP, CO2, H2O, and heat.

What is the A Band of the skeletal muscle fibers?

The dark middle portion of the sarcomere which consists of the H-zone and the M Line.

What is atrophy?

The deterioration of myofibrils from disuse. It is reversible.

What attaches the muscle to bone?

The fascia of the muscle help to attach the muscle to bone. Most specifically, the epimysium layer of fascia that attach to tendons/bones.

What is the I Band of the skeletal muscle fibers?

The lighter, less dense area that contains the rest of the thin filament and contains the z discs.

Where are the ACh receptors contained?

The motor end plate is the region of the sarcolemma adjacent to the synaptic end bulbs that contains millions of ACh receptors.

What part of the I band is the Z disc?

The part that passes through the center of the I band

What is the sarcolemma?

The plasma membrane of muscle fibers

What is the NMJ and what does it consist of?

The synapse between a somatic motor neuron and a skeletal muscle fiber, consisting of a synapse, synaptic cleft, and neurotransmitters.

Why are so many mitochondria present in the sarcoplasm?

There are a higher number of rows close in proximity to muscle in order for ATP to be readily available after being produced in the mitochondria during the Kreb's cycle/ETC.

Within a myogram, what happens when there are stimuli arriving at different times?

There is a summation of the wave of stimuli that causes even larger contractions with a slight dip where the second contraction occurred.

What type of metabolization do slow oxidative fibers use?

They are the least powerful of the three skeletal muscle fiber groups. They use aerobic respiration.

How do Fast Oxidative-Glycolytic fibers metabolize?

They generate ATP via aerobic respiration giving them a high resistance to fatigue. If glycogen level is high, they can make ATP via anaerobic glycolysis.

How do mature muscle fibers arrange themselves in relationship to one another? How thick are they?

They lie parallel to one another and range from 10-100 micrometers in diameter.

How are thick and thin filaments arranged in muscles?

Thick and thin filaments overlap depending on whether muscle is contracted, relaxed, or stretched.

What are two types of Regulatory proteins within the myofibril and what are their functions?

Tropomysin-covers Troponin-holds tropomysin in place

What is an isotonic contraction and what are two examples?

Used for body movements and moving external objects. Concentric-muscle shortens/pulls on a tendon to produce movement. Eccentric-Muscle lengthens while it continues to contract.

What are the two types of smooth muscle tissue?

Visceral Multiunit

What is the maximal muscle energy produced by creatine phosphate storage?

15 seconds or a 100 meter sprint.

How much of an average adult's body weight is made up of muscle?

40-50%

What is a twitch in the muscle?

A brief contraction of all muscle fibers in a motor unit in response to a single action potential in its motor neuron.

Within a myogram, what is an unfused tetanus?

A type of wave summation in which a contraction is stimulated at a low enough frequency (rate of 20-30 times per second) that a partial relax (dip) can be discerned in a myogram.

How do skeletal muscle cells form?

By the fusion of 100 or more small mesodermal cells which transform into myoblasts (an immature muscle cell) which makes them multinucleated.

What is the ion that starts/stops muscle contraction?

Ca2+

Cardiac muscle remains contracted ______ times longer than skeletal muscle and is stimulated by its own _________ fibers.

Cardiac muscle remains contracted 10-15 times longer than skeletal muscle and is stimulated by its own autorhythmic fibers.

What happens after the action potential is propagated into T-tubules?

Causes Calcium's release channels in sarcolemma to open which causes diffusion of Calcium ions across the sarcolemma membrane.

Myofibrils are built from three classes of proteins.

Contractile Regulatory Structural

What are the three sources for ATP production?

Creatine Phosphate (unique to muscles) Anaerobic Cellular respiration Aerobic Cellular respiration

What are the regions of overlap?

Where the A band and the I band overlap

What is the sarcoplasm?

Cytoplasm of muscle fibers.

Why are microscopic capillaries dispersed so widely throughout the muscle tissue?

Each muscle fiber is in close proximity to one or more microscopic capillaries so that diffusion or exchange of materials can occur.

What are the four special properties that enable muscle to function and contribute to homeostasis?

Electrical excitability Contractility Extensibility Elasticity

What is the microscopic anatomy of smooth muscle?

Endomysium surrounds smooth fibers. Sarcolemma contains both thick and thin filaments but they are not arranged in sarcomeres. Smooth muscles lack transverse tubules and have scanty Sarcoplasmic Reticulums.

After birth are muscle fibers able to grow anymore?

Enlargement of fibers take place after birth, but cells are no longer able to undergo cell division.

What are filaments and where are they found within the muscle?

Filaments are small structures within the myofibrils (1-2 um in length) Thin-8nm in diameter Thick-16nm in diameter

Within the a myogram, summarize the data and events taking place during the refractory period.

For maybe less than 10 milliseconds the line flattens out to where is was at the latent period, another stimulation period cannot be formed during this time.

Within the myogram of a twitch, summarize the data and events taking place during the latent period.

From 0-5 milliseconds, the line remains flat. At this time, the action potential is hitting the t-tubules and the influx of Ca is released

Within the myogram, summarize the data and events taking place during the relaxation period.

From 25-50 milliseconds, there is a steady decline in the force of the contraction. At this time, dissociation of myosin head from binding site occurs, binding site is covered, and tension is released lengthening the fiber.

Within the a myogram, summarize the data and events taking place during the Contraction period.

From 5-25milliseconds, there is an exponential increase in the force of contraction. During this time the calcium frees the binding site, myosin head binds, torts, and contraction occurs.

What are fast glycolytic fiber's function?

Generate the most powerful contraction for intense/fast anaerobic movements, like weightlifting, pitching a baseball, etc.

What is the Anaerobic Cellular respiration that muscles use to metabolize energy?

Glycolysis, which provides enough energy for 30-40 seconds or 400 meter dash.

What is the arrangement of cardiac muscle?

Has the same arrangement of actin and myosin. Connect to adjascent fibers by irregular transverse thickenings of the sarcolemma called intercalated discs. Discs contain desmosomes and gap junctions.

How are skeletal muscles well supplied with blood?

1 artery and 1-2 veins accompany each nerve that penetrates skeletal muscles.

What is contractility?

ability of muscles to contract forcefully when stimulated by an action potential.

What is electrical excitability and what organs are associated with carrying these electrical impulses?

ability to respond to certain stimuli by producing electrical signals. neurons and muscle fibers

What does nebulin do within the myofibril?

alignment of thin filaments

What is a T tubule?

an invagination from the surface of the muscle toward the center that contains extracellular fluid.

What does titin do within the myofibril?

anchor thick filament

Where is skeletal muscle located?

attached to bones

The number of skeletal fibers are set ____________

before birth

What is the term for food that has been chewed and swallowed?

bolus

Is skeletal muscle voluntary or involuntary?

both voluntary and involuntary

What happens after the Calcium ions are flooded from the sarcollemma and into the cytosol?

calcium binds to troponin, which causes a conformation change that moves the troponin- trypomyosin complex away from the myosin binding sites on actin. Myosin head binds to sites and contraction cycle begins.

What is the H zone?

center of the A band; containing thick filaments.

What is a neurotransmitter?

chemical that allows communication between cells (between gaps) Acetylcholine (ACh)

Define epimysium.

connective tissue that encircles the whole muscle

What is a skeletal muscle composed of?

connective tissue that surround fibers and whole muscles with blood vessels and nerves that penetrate into muscle.

What are myofibrils?

contractile elements of skeletal muscles, 2 micrometers in diameter, extending the entire length of the fiber, which is the reason skeletal muscles look striated.

How does motion of the body happen?

contraction and relaxation of muscles by changing chemical energy into mechanical energy to generate force, perform work and produce movement.

What does dystrophin do within the myofibril?

cytoskeletal protein that links thin to the membrane. Protein of sarcolemma structural integrity.

What are the 5 functions of the muscle tissue?

1. Producing movement 2. Stabilizing body positions (support joints) 3. Regulating organ volume (sphincter-smooth/skeletal) 4. Moving substances within the body 5. Producing heat

What are the 3 types of fascia?

epimysium perimysium endomysium

What is the term for the broad bands of fibrous connective tissue that surround muscle?

fascia

Slow fibers are resistant to ___________

fatigue

What is glycogen and what is it used for?

glucose (carbohydrates) stored in mammals. When ATP is needed glycosydic bonds are broken down and glucose begins glycolysis.

What is contained within the sarcoplasm?

glycogen myoglobin mitochondria

Muscle fibers differ in their amount of myoglobin. What do high and low myoglobin containing fibers look like?

high myoglobin- red fibers low myoglobin- white fibers

Why are intercalated discs useful?

In cardiac muscle, gap junctions and desmosomes allow impulses to move through cells. This enables synchronicity of muscle contraction.

What are some factors that seem to be the cause of muscle fatigue?

Inadequate release of Calcium ions from sarcolemma Depletion of creatine phosphate insufficient oxygen Depletion of gylcogen and other nutrients Build up of lactic acid and ADP failure of action potentials in the motor neuron to release enough ACh.

Summarize the contraction cycle.

Influx of Calcium must be present, then ATP hydrolysis takes place. The attachment of the myosin to actin to form cross bridges occurs as the energized head binds to myosin binding site. There is a release of phosphate which opens the ADP binding site and rotates the mysosin head. Last there is a detachment of myosin from actin. ATP once again binds to pocket on myosin head and causes dissociation.

What is the structure of Fast Oxidative-Glycolytic fibers?

Intermediate in diameter red, because they contain myoglobin and capillaries. glycogen level is high

What is myoglobin?

It binds oxygen in muscle for use in the creation of ATP

What is the Sarcoplasmic reticulum?

It is a fluid filled system of membranous sacs which encircles each myofibril.

Within a myogram, what is a fused tetanus?

It is a wave summation in which a stimulation occurs at a higher frequency (80-100 times per sec) and twitches can not be discerned.

What is the shape of myosin?

It is shaped like two golf clubs twisted together

If there is no O2 to begin Aerobic respiration, what is the product and what happens to it?

Lactic acid that uses facilitated diffusion (a passive process) in order to filter into the blood.

What is the structure of Fast glycolytic fibers?

Largest in diameter. Contain the highest number of myofibrils (pull sarcomeres) white- low myoglobin and few capillaries.

How do Fast glycolytic fibers make ATP?

Mainly via glycolysis, because they don't have mitochondria stores.

Is cardiac muscle voluntary or involuntary?

involuntary

Is smooth muscle voluntary or involuntary?

involuntary

Where does propagation of action potential take place in the microscopic anatomy of skeletal fibers?

Muscle action potential propagate along sarcolemma and through T tubules which quickly spread through the muscle fibers.

Once fusion occurs what do the muscle cells lose their ability to do?

Muscle cells lose their ability to undergo cell division.

How is creatine phosphate produced/used?

Muscle fibers produce an excess of ATP they need for resting metabolism which is used to synthesize creatine phosphate. Creatine kinase catalyzes transfer of phosphate to creatine. When contraction begins and ADP level rises, CK catalyzes the transfer of phosphate from creatine back to ADP to produce ATP.

The study of muscle structure/function

Myology

What are two types of contractile proteins?

Myosin Actin

What are oxygen binding proteins within the muscle tissue which bind to O2 when it is plentiful and release O2 when it is scarce?

myoglobin

Within the sliding filament mechanism, how does the muscle contraction process occur?

myosin heads attach and walk along the thin filaments at both ends of a sarcomere, pulling the thin filaments (z discs) toward the M line, meet at the center, and the sarcomere shortens.

What is an Isometric contraction?

no movement; stabilized

Is smooth muscle striated or non-striated?

non-striated

What is myosin and what does it do within the myofibril?

Myosin is a motor protein integral in the conversion of chemical energy to mechanical energy in the form of force during a contraction.

Each skeletal muscle is a seperate _________ composed of hundreds-thousands of cells called ______________

organ fibers

Do action potentials vary in strength to cause different sized contractions?

No, action potentials are all the same size. The tension depends on the amount of muscle fibers stimulated.

Define endomysium.

penetrates each fascicle and seperates individual muscle fibers.

What is the term for contraction of hollow organs that push substances through?

peristalsis

Slow Oxidative fibers are mostly used for _______ and _________

posture and endurance

How are skeletal muscles organized?

Skeletal muscle is organized in layers; epimysium being most superficial; perimysium being intermediate, and endomysium being the deepest.

Few myoblasts still persist after birth, which are called ________ and are used for __________

satellite cells regeneration functional muscle fibers (only for muscles with minor damage)

What is the synaptic cleft?

small gap

Why are are slow oxidative fibers referred to as slow?

Slow because ATPase hydrolyzes ATP slowly.

Based on metabolitic characteristics, we can divide skeletal muscle fibers into three groups.

Slow oxidative Fast oxidative fast glycolitic

What are motor units?

Somatic motor neuron plus all the skeletal fibers it stimulates.

Within the myogram of a twitch, summarize the data and events taking place right before the latent period.

Stimulation from the action potential is taking place. The force of contraction line stays flat until the time hits 0 milliseconds.

Describe the structure/appearance of slow oxidative fibers.

smallest in diameter, dark red due to high amounts of myoglobin

What is the difference in contraction between skeletal and smooth muscle?

smooth muscle contracts like a cork screw, unlike skeletal.

What is the term for neurons that stimulate skeletal muscle to contract?

somatic motor nerves

Is cardiac muscle striated or non-striated?

striated

Is skeletal muscle striated or non-striated?

striated

What does myorresin do within the myofibril?

structural integrity

Define Perimysium.

surrounds groups of 10-100 or more individual muscle fibers, separating them into bundles called fascicles.

What is the region where communication occurs between 2 neurons, or between a neuron and a target cell?

synapse of the NMJ

At the ends of the NMJ, the motor neuron axon divides into a cluster of _________________

synaptic end bulbs.

What is elasticity?

the ability of muscle to return to its original length and shape.

Skeletal muscles contract and relax with different _________ due to ____________

velocities composition of fibers, physical training, or genetics

Where is cardiac muscle located?

wall of heart

Where is smooth muscle located?

walls of hollow structures

What separates sarcomeres?

z-discs seperate sarcomeres from one sacrcomere from the other. Z-discs are plate like separations important in the contraction process.

What do patterns of overlap in thick and thin filaments of skeletal muscle fibers consist of?

zones and bands.

Describe the sequence that must happen as the nerve impulse elicits a muscle action potential.

1. Release of ACh across the cleft and bind to the receptors 2. Activation of ACh receptors causes ion channels to open and an influx of sodium ions. 3. Production of action potential caused by the change in charge. 4. Termination of ACh activity after it is broken into 2 groups A and Ch making it nonfunctional for binding.

Why do they call fast oxidative-glycolytic fibers "fast"?

ATPase hydrolyzes 3-5x faster than myosin ATPase in Slow Oxidative. It reaches peak tension faster, but for a brief duration, like sprint.

Which protein contains the myosin binding site where a myosin head can attach?

Actin

What is actin and what is does it do within the myofibril?

Actin is the major component of thin filament. Individual actin join to form actin filaments.

Which of the forms of muscle metabolism is used for endurance activities?

Aerobic, as long as nutrients and O2 are present.

What is denervation?

Affects the nerves and is irreversible.

Where in the muscle fiber does the action potential propagate?

Along the sarcolemma and into T-tubules

What are the two sources for oxygen for muscle tissue?

Oxygen that is acquired through diffusion from the blood. Oxygen released by myoglobin within the muscle fibers.

What is the M Line?

Proteins that hold filaments together at the center of the H Zone.

What does the sarcoplasmic reticulum of skeletal fibers store/release and why is this significant?

Relaxed it stores calcium ions. Upon release of these calcium ions, muscle contraction is triggered.

Skeletal fibers microscopic anatomy consists of what specific major constituents?

Sarcolemma T tubules Sarcoplasm Myofibrils Sarcoplasmic reticulum Filaments Sarcomere