CH 9 & 10

what happens when the AP reaches the sarcoplasmic reticulum

"opens voltage gated Ca channels causing Ca to be released out into sarcomere" VOLTAGE GATED CHANNELS: activated by changes in electrical membrane potential near the channel. Critical in neurons but found in most cells Muscle AP triggers Ca 2+ release from SR Ca -> contraction

what is the relationship in whole muscles between their length and the amount of tension created at that length?

# Of pivoting cross-bridges: the fiber's resting length at the time of stimulation depends on freq. of stimulation and motor recruitment

what are the structural features of cardiac muscle tissue

-are small -have a single nucleus -have short, wide T tubulues -have SR -are aerobic -have interccalated discs

what processes in a skeletal muscle contraction req. ATP ( don't forget when the muscle is resting)?

1 dettach cross bridge and sending back myosin head 2 resting membrane potential because membrane permeability to na and k determines rmp

what are the 5 basic steps of excitation-contraction coupling?

1. AP moves down motor neuron 2. Neurotransmitter (Ach) released by motor neuron 3. Ach initiates AP in muscle fiber 4. Muscle AP triggers Ca 2+ release from SR 5. Ca 2+ initiates contraction

how long can creatine phosphate sustain a muscle contraction

15 SECONDS

how much ATP does anaerobic metabolism produce compared to aerobic metabolism (net gain)?

2 ATP/ glucose for ANAerobic

how much ATP does aerobic metabolism produce compared to anaerobic metabolism

36/glucose for aerobic

muscle performance can be considered in 2 ways: the amount of force a muscle can generate and the amount of time the muscle can function (endurance). In terms of fiber types, how are force and endurance at odds with each other???

?? Anaerobic Endurance Sustained powerful muscle contractions (e.g., weight lifting) Aerobic Endurance Continual contraction of muscle over time (e.g., jogging)

describe the process of what happens at a chemical synapse between a motor neuron and a muscle fiber

A neuromuscular junction (or myoneural junction) is a chemical synapse formed by the contact between a motor neuron and a muscle fiber. It is at the neuromuscular junction that a motor neuron is able to transmit a signal to the muscle fiber, causing muscle contraction.

A. Starting with the whole muscle, describe the internal organization and the connective tissue that surround the various levels of organization... B. Which CT is superficial and which one is deep? C. What does each CT wrap around ?

A....Whole muscle, fascilce, muscle fiber=muscle cell, myofibril, which are cylindrical structure containing contractible fibers. Sarcolemma= "flesh husk", cell membrane of muscle cells. Sarcoplasm= muscle cell cytoplasm 1. Whole Muscle surrounded by CT --> EPIMYSIUM 2. Fascicle surrounded by CT --> PERIMYSIUM 3. Muscle FIber (myofiber) surrounded by CT -->ENDOMYSIUM B. The EPIMYSIUM is superficial and the ENDOMYSIUM is deep C. answered with A. t-tubules : networks of passageways through muscle fiber -continuous with sarcolemma (transmits AP into and through cell)

in what ways can you improve force or endurance w/ training -how does this training improve force or endurance

ANA Training = frequent, brief, intense workouts Muscle Hypertrophy: enlargement of muscle by increasing myofibrils & myofilaments ae Training = sustained low levels of muscle activity High mitochondria; high capillaries

what causes Ca to flow out of the sarcoplasmic reticulum

AP opening voltage gated channels

what neurotransmitter is delivered into this space during skeletal muscle contraction? -where was it before it was released?

Acetylcholine (Ach: neurotransmitter) -was in the synaptic VESICLES IN THE AXON TERMINAL

what factors contribute to a muscle returning to its resting length?

Ach is removed by Ache (which is an enzyme). Calcium is actively transported in the SR. Calcium detaches from the tropinin Ach removed by AChE Active transport of Ca2+ into SR Ca2+ detaches from troponin Active sites are recovered by tropomyosin Sarcomeres remain contracted until a muscle fiber returns to resting length by: Elastic forces The pull of elastic elements (tendons and ligaments) Opposing muscle contractions Antagonists (biceps brachii vs. triceps brachii) Gravity can take the place of opposing muscle contraction to return a muscle to its resting state

Propagation of AP at skeletal muscle fiber

Ach released from axon terminal Ach binds to receptor on motor end plate AP conducted along sarcolemma

How does sustained sarcoplapsmic Ca and lack of ATP cause rigor mortis?

Actin and myosin can't be seperated Ca ions leak from the SR unable to recall ions back

what do we call the signal moving down the neuron?

Action Potential

when is the myosin in the high E state how did it become so???

After ATP has bound to it. Myosin breaks down harnessing E to put the myosin head back into the high E cocked position mysosin head contains ADP and Pi when relaxed brought about through the hydrolyzation of ATP when it detaches from the actin site

be sure to include the dens ebodies and the arrangement of actin and myosin

An action potential enters a neuron...by the T-tubules What structures do the Ca ions bind to when muscle contraction is initiated.... TROPONIN MOLECULE cross bridges form between... ACTIN FILAMENTS AND MYOSIN HEAD An AP introduced at the neuromuscular junction is propagated alon the sarcoplasmic reticulum FALSE In response to an action potential entering the neuron ca ions diffuse from the sarcolemma into the sarcoplasm

what makes up intercalate d disks??? what is their function? how do they contribute to the heart's ability to contract all at once??

Are specialized contact points between cardiocytes Join cell membranes of adjacent cardiocytes (gap junctions, desmosomes) link heart cells mechanically, chemically, and electrically, the heart functions as a functional syncytium Length - Tension Relationship

describe (in own words) the muscle contraction event from the AP generation in the sarcolemma through the contraction cycle ( to reactivation of mysosin). Be certain to include the 6 participants that were mentioned in lecture (Ca2+,ATP, actin, myosin, troponin, and tropomyosin.)

C o n t r a c t i o n C y c l e . . . Step 1: Ca 2+ binds to troponin -(exposure of active sites {myosin heads in "cocked position"}) Step 2: FORMATION OF CROSS-BRIDGES -(activated myosin head drawn to and attaches to active site on actin forming a cross-bridge) Step 3: PIVOTING OF MYOSIN HEADS -("Power Stroke" ) -pulls actin filament toward M line -Stored E released-ADP & Pi Step 4: CROSS BRIDGE DETACHMENT -(ATP binds to myosin heads causing detachment of cross-bridge) Step 5: COCKING OF MYOSIN HEAD -(Myosin is reactivated /"re-cocked" by hydrolyzing ATP into ADP and Pi)

in which stage do you get the most tensio in the muscle fiber

COMPLETE TETANUS

to which component of the thin filament does Ca 2+ bind?

Ca binds to troponin, troponin moves tropomyosin out of the way of actin. Myosin binds to actin

when Ca stores are depleted, what happens to the muscle contraction?

Ca stores cant be depleted. NEED Ca to move troponin to let active sites be visible. If Ca is depleted, then active site on actin is blocked, and muscle contraction cant occur

Where do you find capillary beds ( capillaries) and the ends of nerves (axon terminal/synaptic terminals)?

Capillary beds inside fasicle-bundles of muscle cells Axon Terminals/Synaptic Terminals: on individual muscle cells in the ENDOMYSIUM

what will be the effect of its binding in terms of Na ion entry into the skeletal muscle cell?

Chemical will bind and cause it to open. Then Na enters the muscle cell.

How do the CT's relate to one another- meaning, what is significant about the fact they are all connected to one another.

Components of the sarcomere are attached to connective tissues, EPIMYSIM, PERIMYSIUM, and ENDOMYSIUM are all attached to each other. They merge to form a tendon, which attaches to bone.

what is the relationship between a sarcomere's resting length and amount of tenstion that it can create at that length? RELATIONSHIP CALLED LENGTH-TENSION RELATIONSHIP draw a graph (or be familiar with a graph) of this relationship on the y axis and -what determines the amount of tension produced ?

Depends on the length of the sarcomere, intermediate sarcomere length has the most overlap of myosin heads w actin therefore more cross bridges formed

what are the 3 muscle fiber types b. how diff in terms of their contraction velocity, metabolic source of E, diameter and force production c. what features do the fast and slow fibers have that support their mechanism for ATP production (more or less of certain organelles or enzymes or blodd supply) ??

FAST FIBERS: -----------Contract in 0.01 sec or less (after stimulation) ---Large diameter (densely packed myofibrils) ---Powerful (high sarcomere # = high tension) ----Rely on anaerobic respiration ---Large glycogen reserves -->Fatigue rapidly SLOW FIBERS --3x slower contraction --½ diameter -Sustained contractions (high endurance) --Rely on aerobic metabolism --Extensive capillaries (high O2 supply) --Myoglobin: Binds O2 (high O2 storage) ---Large # mitochondria (high O2 usage) ---Lipid deposits INTERMEDIATE FIBERS Can convert to fast fibers or slow fibers depending on body's needs

how long can AErobic metabolism sustain a msucle contraction?

FOR LONG PERIODS OF TIME... (HOURS)

relatively speaking, how long can stored ATP sustain a muscle contraction?

FOR NO MORE THAN 5 SECONDS

how long can ANaerobic metabolism sustain a muscle contraction

FOR SHORT PERIODS OF TIME (1-2 MINUTES)

when you want a weak, sustainable whole muscle contraction, do you stimulate more motor units or less motor units??? when you want a strong whole muscle contraction do you stimulate more motor units or less motor units????

Few are needed for a weak muscle contraction. Many are need for a stronger muscle contraction.

where is smooth muscle tissue found

Forms sheets, bundles around other tissues blood vessels respiratory system digestive system urinary system reproductive system integumentary system iris of eye

how does a cell reproduce the e it needs for sustained muscle contractions once the reserves have been depleted ?

Glycogen stores, lipids and amino acids stores are used when ATP is used up essentially .... AEROBIC METABOLISM

some muscles contract faster than other s. THe ones that contract faster are called fast twitch. The ones that contract slower called slow twitch. HOw might the shap efo the fiber twitch graph change for the diff. fiber types???

Graph will PEAK quickly and DROP over a shorter time interval. Producing a fast response, such as needed in eye muscles. The graph would PEAK slowly and drop off slowly in a muscle utilizing a slower response such as posteral muscles.

if you want just a brief contraction, what stimulus freq. should you use for the recruited motor units? in whole muscle tetanus, how many motor units are recruited????

HIgh frequency stimulus. ALL OF THEM

of incomplete or complete tetanus, which can be stustained longer? which is a more fluid movement

INCOMPLETE TETANUS COMPLETE TETANUS

what kind of channels will it bind to?

ION channels chemically gated channels

when you pick an object up, shortening the muscle length, is this an isometric or an isotonic contraction? when you are generating force in the muscle, but not shortening the muscle length against a wall) is this an isometric or isotonic cotnraction? in what forms is this E stored in a muscle cell

ISOTONIC ISOMETRIC CREATINE PHOSPHATE ATP

what is going on in the muscle fiberr in terms of amount of Ca present in the sarcoplasm in wave summation, incomplete tetanus and complete tetanus

If stimulate a muscle and before can relax, stimmulate AGAIN next twitch builds on fist = producing more FORCE Force incr b/c there is more Ca available due to 2nd stimulus. SO...more stimuli=more Ca=more exposed active sites on actin =more cross-bridges form = MORE FORCE :D !!!

how does Ca become removed from the sarcoplasm?? is this an active process??

It become detached from actin, and active transports pump it back to the SR. yes conentration gradient

how can you vary the amount of tension that a single muscle fiber exerts (see following Q's)

It depends on the amount of cross bridges created, being influenced by the cross-sectional muscle fibers, and amount of neural stimulation.

what are the 3 phases of a msucle fiber twitch

LATENT PERIOD = period from the AP -> myosin binding to actin --> time between stimulus and tension dev. CONTRACTION PHASE: myosin and actin undergoing repeated pivoting cross bridges --> period where tension rises to peak level --> Ca++ release; cross-bridge formation RELAXATION PHASE: period where tension falls to resting level --> Ca++ uptake, cross-bridge dettachment

what is the delay between the time of stimulus and the time when tension incr. called? what is happening in the muscle fiber during this delay?

LATENT PERIOD LP Ach travels across synaptic cleft binds to chemically gated channels Na enters muscle cell and opens voltage gated channels causing AP on muscle cell AP travels across sarcolemma down T-tubules opening voltage gated channels on SR Ca exits SR, binds to tropinin moves tropomyosin out of way of active site on actin Myosin can now bind

changing the number of motor units utilized at a given moment is call motor unit recruitment. SO, in strong contractions, you recruit _____ motor units (more or less) than in weak contractions

MORE

Describe the internal anatomy of a skeletal muscle fiber ( know all the structures with pointers on pic)

MYOFIBRILS: contain myofilaments/or protein. ACTIN: thin filaments, MYOSIN: thick filaments. SARCOMERE: repeating units of myofilaments (-10,000 myofibrils) Contractible unit of muscle. SARCOLEMMA=cell membrane. T-TUBULES: networks of passageways through muscle fiber. Continuous with sarcolemma (transmits AP into and through cells). SARCOPLASMIC RETICULUM:specialized endoplasmic reticulum -overlies sarcomere -contains Ca 2+ ~[40,000] compared to cytoplasm TRIAD

smooth muscle maintains a background level of activity called tone. What can affect this? what is the effect of length changes on smooth muscle tension?

Maintains normal "background" levels of activity Modified by neural, hormonal, or chemical factors --------------------------------------- Thick and thin filaments are scattered Resting length not related to tension development Functions over a wide range of lengths (plasticity)

how might size of a motor unit ( number or fiberrs) affect the amount of control that you can have of a whole muscle would you want to have bigger motor units (more fibers/motor neuron) for activities that req. fine movements?

Motor units that affect involuntary movements (eyes) don't req. as many fibers. To have your back hold you up, NEED a high [muscle fibers/motor unit] chem symbol conc. NO it would be wasted E!!! >(

what are the myofilaments

Myofibrils : contain myofilaments, or protein. Actin are thin filaments, myosin are thick filaments. Sarcomere are repeating units of myofilaments (-10,000 myofibrils) Contractible unit of muscle. STRIATED MUSCLES are the filaments of myofibrils, constructed from proteins, principally myosin or actin. Types of muscle are striated muscle

How does a muscle get stimulated to contract (by another cell)

NEUROMUSCULAR JUNCTION: site of interaction between neuron & muscle cells- where neuron "meets" muscle fiber transmit signal from neuron -> muscle cell ONE connection/muscle fiber skeletal muscles are voluntary muscles ORRRRR neuron highly exitable cells:::: if adequately stimulated, will generate an electrical impules that will be conducted down length of axon

you cannot sustain whole muscle tetanus for long, but you can sustain a whole muscle contraction. are sustained whole muscle contractions as strong as whole muscle tetanic contractions?

NO , if they were, we couldnt sustain the E to do everday activities

do muscles have all the E they need for a sustained muscle cotnraction stored in the cell?

NO don't store ATP for more than 5 sec.

can you stimulate only one part of the muscle fiber, but not the other ( only some sarcomeres in an individual fiber but not others)?

NO, can only stimulate the muscle cell as a whole. Jot just a single myofibril or sarcomere

can aerobic metabolism occur if the O2 in the cell has been depleted

NOOOOO ?

what are the structural features of smooth muscle tissue?

Nonstriated tissue Different internal organization of actin and myosin Different functional characteristics

what is aerobic metabolism

O2 req. glucose (glycogen) ->pyruvate-> CO2 + H2O primary source of ATP during periods of rest (95% of ATP) efficient (36 ATP/glucose) -can use multiple E sources (carbohydrates, lipids, proteins)

what is anaerobic metabolism

PEAK ACTIVITY predominates -fuel: glycogen ATP req. for muscle contraction ATP acquired from CP (initially) is the creation of energy through the combustion of carbohydrates in the absence of oxygen. This occurs when your lungs cannot put enough oxygen into the bloodstream to keep up with the demands from your muscles for energy.

What is the function of those organelles?

SARCOPLASMIC RETICULUM: store Ca MYOFIBRILS: contractile proteins MITOCHONDRIA: -ATP

are there specific molecular mechanisms that "pull" sarcomeres apart?

Sarcomeres remain contracted until passive recoil of elastic components, gravity can assist returning muscle to resting length. Antagonistic (opposing) muscle groups contracting can return muscle to resting length.

What organelles are present and essential for skeletal muscle function?

Sarcoplasmic reticulum myofibrils: mitochondria. SARCOLEMA ?

how are smooth muscle cell anatomically similar to skeltal muscle cells how anatomically diff. what is the significance of these diff.'s

Spindle shaped cell Have a single nucleus Scattered myosin fibers Myosin - more heads Thin filaments & intermediate filaments attached to dense bodies

SLIDING FILAMENT THEORY:::

THIN filaments of sarcomere slide toward M line between THICK filaments Z lines move closer together

tensions in the amount of pull that a muscle fiber exerts on the CT in a muscle. What ultimately determines the amount of tension that a single muscle fiber can generate?

The amount of cross bridges formed between actin and myosin.

what are the proteins of interest in the myofilaments

The proteins of interest are myosin, thin filament is made of actin, troponin, tropomyosin, and titin.

once Na moves through chemically gated Na channels at the neuromuscular junction/synapse, what will happen to the sarcolemma on the muscle cell?

The sodium entry changes the voltage across the sarcolemma triggering voltage gated sodium channels to open. Sodium enters muscle cell causing depolarization. - to + charge

how are the myofibrils arranged?

These proteins are organized into thick and thin filaments called myofilaments, which repeat along the length of the myofibril in sections called sarcomeres. Muscles contract by sliding the thick (myosin) and thin (actin) filaments along each other.

to get the most force from a muslce, how many motor units shouuld you recruit??

To get the most force from a muscle, you would want to recruit more motor units.

Describe the organization of the skeletal muscle organ

WHOLE MUSCLE FASCICLE MUSCLE FIBER =muscle cell functional unit of muscle MYOFIBRIL cylindrical structures containing contractile fibers 100-1,000's/cell SARCOLEMMA="flesh husk" =cell membrane of muscle cells SARCOMPLASM: muscle cell cytoplasm sarco=flesh ; myo=muscle EPIMYSIUM --> muscle organ PERIMYSIUM: contains blood vessels and nutrients and regulates contraction -->Fascicle ENDOMYSIUM: surrounds individual muscle fibers/cells contain capillaries and neurons -->Muscle Fiber

Is there a space between the motor neuron and muscle cell? What do we call this space?

YES it is called SYNAPTIC CLEFT. or gap

how might motor unit cycling (turning on some motor units and off others) have to do with sustained muscle contraction?

YOU Recruit a motor unit, before it relaxes, recruit another one, and before that relaxes, recruit another one. By the time that last one is recruited, the first one is completely RELAXED, so now can recruit that one!!! :D and keep cycling them to sustain the contraction w/OUT fatigue! :o

where are the Z discs and M line?

Z discs are the outer boundaries of the sarcomere. M line is the midline of the sarcomere.

Passive channels Gated Channels

__also called LEAK CHANNELS -always OPEN -permeability changes w/ conditions -open and close in response to stimuli -at RP (resting potential), most gated channels are closed

in order to begin skeletal muscle contraction, a neuron must tell the muscle to contract. What is the name for a neuron that tells a muscle cell to contract?

a motor neuron

what factors are necessary for continuous muscle contraction (think back to the "participants" you described above.

a nervous system stimulus (AP), Ach release, AP on skeletal muscle cell, all contributing to Ca release Ca and ATP must be present so Active Site on ACTIN is exposed Ca and so that MYOSIN can detach from Actin (ATP)

what is a motor unit

a single neuron and ALL the muscle fiberrs innervated by it

what types of changes can you see in fiber type distribution with aerobic or anaerobic training does aerobic training stimulate muscle hypertrophy

aerobic : more white muscle fiber anaerobic: dark muscle fiber \ no anaerobic does

at LIGHT to MODERATE activity, do your cells primarily use aerobic or anaerobic metabolism? WHy what substrate/fuel are skeletal muscles most using for ATP sources at light to moderate activity?

aerobic metabolism fuel: Glycogen ATP req. for muscle contraction

at REST do your cells primarily use aerobic or anaerobic metabolism? -what subtrate/fuel are skeletal muscles most using for ATP sources at rest

aerobic metabolism fuel: fatty acids ATP surplus making glycogen reserves recharching creatine phosphates

is aerobic or anaerobic metabolism more efficient --meaning which one gains more ATP per gluscose molecule?

aerobic metabolism is more efficient gains more ATP 36 per glucose

can you explain the varying tension production with varying lengths in terms of the amount of overlap between the actin and myosin?

already did

which bichemical pathway is considered anaerobic

anaerobic metabolism glycolysis -no O2 req. acid buildup leads rapidly to muscle fatique

at PEAK activity do your cells primarily use aerobic or anaerobic metabolism -what substate/fuel are skeletal muscle most using for ATP sources at peak activity

anaerobic metabolism predominates fuel: glycogen ATP req. for muscle contraction ATP acquired from CP (initially)

what are the myofibrils

any of the elongated contractile threads found in striated muscle cells.

on a graph of a msucle twitch with time on teh x axis and muscle tension (or force) on the y axis with the stimulus occurs at time 0, when does the tension start to increase?

at latent period LP CHECK!!!!

Length tension relationship

at longer sarcomere lengths -> less overlap of myosin and actin = less cross bridges and less force at very short lengths there is interference between actin strands causing less force, at intermediate lengthss =ideal overlap between myosin and actin = more cross bridges=more force

where is cardiac tissue found

cardiac muscle heart

which biochemical pathways are considered aerobic

cell repiration (glycolysis + Krebs cycle + respiratory e- transport ) ????????

what happens at the end of the neuron when the signal arrives?

channels open

what is an action potential?

electrical signal traveling from brain/spinal cord along axons -> muscle fibers = contract

why cant you exercise at peak exertion for a long period of time why is body able to exercise lightly for very long time

fast fibers contract in 0.01 sec or less after stimulation large diameter (densely packed myofibrils) powerful (high sarcomere #= high tension) rely on anaerobic resp. --large glyccogen reserves -fatique rapidly slow fibers 3x slower contraction 1/2 diameter sustained contractions (high endurance) Rely on aerobic metabolism -capillaries High O2 supply large # mitochondria use O2

when we talk about the sarcomere shortening, what does this mean in terms of the thick and thin filaments

filaments of the sarcomere slide towards the M line in between the thick filaments

what happens to the distance between Z lines in relation to the M line

get closer together

what substances can be broken down to form ATP in aerobic metabolism

glucose (glycogen) ->pyruvate-> CO2 + H2O ??

what substances are broken down to form ATP in anaerobic metabolism? what type of molecule is a storage for for glucose

glycolysis the ana... pathway breaks glucose molecule into 2 pyruvate glycogen

once the acetylcholine is released from the motor neuron, where does it go? where will it bind?v

goes into SYNAPTIC CLEFT crosses and BINDS w/ a Ach chemically gated channel on the motor end plate of the SKELETAL MUSCLE cell

what must happen first in a neuron before it can communicate with the muscle cell

have the AP pass through

where is the Ca stored when the muscle is at rest

in the Sarcoplasmic reticulum

what happens once Ca flows into the sarcoplasm

it binds to troponin

what happens to the distance between Z lines during muscle contraction

it minimizes. They move closer together

when an action potential is generated in a muscle fiber sarcolemma, where does the action potential travel to (along which components of the muscle fiber does the action potential travel?)

it spreads down the entire sarcolemma down all the t-tubules which are in contact with sarcoplasmic reticulum. Causing them to release Ca

If Ca 2+ and ATP are present, is contraction cycle a single event or a repeated event

it's a repreated event, it stops when either or is depleted

what is a by-product of glycolysis that builds up when you can't use aerobic metabolism how does this by-product affect muscle cells

lactic acid pyruvate provides E to cells when O2 present by oxidizing to produce CO2 in ANAerobic =pyruvate ferments =lactic acid used by muscle cells to continue to the process of metabolism of glucose for E production

passive channels

leack channels always open permeability changes w conditions

what is happening in the muscle fiber as the tension decr

less Ca present =less active sites on actin exposed =less myosin binding =LESS FORCE

resting membrane potential (RMP)

membrane permeability to Na+ and K+ determines RMP

when ATP stores are depleted, what happens to the muscle contraction?

myosin and actin head cannot break, which leaves the muscle always contracted

what is happening in the muscle fiber as the tension incr

myosin binds to actin forming cross bridge myosin pivots moving actin toward M-line more active sites exposed on actin =more myosin canbind to actin more force produced

can anaerobic metabolism occur if the O2 in the cell has been depleted

no

does the motor neuron physically touch the muscle at the neuromuscular junction?

no

can a skeletal muscle contraction occur if one step is missing or if the steps are out of order? why? Why not??

no because each step is key in allowing the movement of Ca across the concentration gradient and against to activate the ATP and allow the myosin and actin to bind

when you exercise at peak exertion, can your cerculatory system deliver O2 to your muscle cells fast enough to sustain aerobic metabolism?

no it cannot

are all of the myosin heads in a sarcomere binding to actin, pivoting and then releasing from actin all at the same time?

no they are not

gated channels

open and close in response to stimuli at resting potential most gated channels are closed

what is a sarcomere

repeating units of myofilaments (~10,000/myofibril) --contractile unit of skeletal muscle The sarcomere is a contractile unit of skeletal muscle. Made of thick and thin filaments.

how are cardiac muscle cells anatomically similar to skeletal muscle cells ? how anatomically diff. ? what is the significance of these diff.'s ;

similar ...have sr and t tubules diff. single cell short wide t tubules are small have intercalated disccs

what is a muscle fiber twitch?

single stimulus=contraction and relaxxation sequence

when nervous system stimulation stops, what happens in the muscle cell?

the SR is constantly pumping Ca back into itself so once AP stops, no more Ca is released and Ca levels drop blocking the active site on ACTIN muscle contraction ENDS

what happens at the amount of tension in a muscle fiber as you vary the freq. of stimulation ?

the more frequently the muscle is stimulated= more force produced

what is a neuromuscular junction and where is it located

the site of interaction between motor neuron and muscle cells =where neuron meets muscle fiber motor neuron transmits a signal to the muscle fiber, causing muscle contraction

why are the mitochondria necesary in skeletal muscle cells?

they are necessary because they are what create ATP needed for muscle contraction to take place as well as muscle relaxation "POWER HOUSE OF THE CELL"

what kind of channels open, what goes into the axon terminal, and what does that cause to be released?

voltage gated Ca channels OPEN -Ca goes into AXON terminal = synaptic vesicles to releases Ach (neurotransmitter) vesicles containing neurotransmitter move towards synapse causing neurotransmitter to be released into -> synapse

what is a synapse and where is it located?

where the axon Teminal of the neuron meets the motor unit and plate of skeletal muscle between motor neuron and muscle cell (fiber) junction between 2 nerve cells { a minute gap across which impulses pass by diffusion of a neruotransmitter