BSI II L4
What are the three types of fiber are found in the body:
- Type I slow oxidative fibers - Type IIx fast glycolytic fibers - Type IIa fast oxidative fibers
Define Type IIa fast oxidative fibers
- Type IIa fast oxidative fibers are intermediate in characteristics between types I and IIx in that they have ↑ATP'ase activity, (↑velocity), and ↑oxidative capacity, (↑no. mitochondria plus ↑myoglobin), so relying primarily on the Krebs cycle for ATP production plus ↑capillary density for O2 supply: these fibers contract rapidly and are resistant to fatigue as long as the O2 supply is adequate and are intermediate in size between I and IIx fibers so are intermediate in the force they can generate, (examples of muscles composed primarily of this type of fiber include the muscles of the lower limbs which must move the body for long periods during locomotion).
Define Type Iix fast glycolytic fibers
- Type IIx fast glycolytic fibers have ↑ATP'ase activity, (↑velocity), and ↓oxidative capacity, (↓no. mitochondriaplus ↓myoglobin), so relying primarily on glycolysis for ATP production: these fibers contract rapidly, fatigue rapidly and are generally quite thick so can generate much more force than say a type I fiber plus they contain much glycogen as an immediate fuel source, (examples of muscles composed primarily of this type of fiber include the muscles of the upper limbs which often briefly lift very heavy objects).
Which muscle type has the presence of GAP junctions?
-Cardiac at intercalated discs -Smooth in single-unit muscle
Perimysium (middle)
-Connective tissue surrounding a fascicle -individual muscle fibers are grouped into fascicles surrounded by perimysium.
intercalated discs of cardiac muscle
-Represent specialized cell junctions between cardiac muscle cells. -Interdigitating folds of sarcolemma at the end of adjacent cells, linking them structurally and functionally. -Little bridges in between cells and they have Gap junctions. so if the cell is funny ions flow to the adjacent cell and get that cell funky
Which muscle type has elaborated Sarcoplasmic Reticulum?
-Skeletal -Cardiac (less than skeletal muscle; scant terminal cisternae -smooth muscle (as well developed as in cardiac muscle)
Which muscle type has cells that exhibit individual neuromuscular junctions?
-Skeletal (At A-I junctions) -Smooth in multiunit muscle only (NOT is single muscle unit)
Which muscle type has sources of Ca++ for Calcium pulse?
-Skeletal (SR) -Cardiac (SR and from extracellular fluid) -Smooth (SR and from extracellular fluid)
Epimysium (outer)
-surrounds entire muscle -is composed of dense irregular connective tissue, (randomly arranged collagen fibers: see previously); sometimes this "blends" with the deep fascia that divides neighboring muscles.
What are the 4 main functions of skeletal muscle?
1. Movement: attached to skeleton to articulate it. 2. Posture: some skeletal muscles contract continuously to maintain posture so one can sit or stand for long periods of time. 3. Joint stabilization: muscle tone is maintained to stabilize joints. 4. Heat generation: skeletal muscles, (significant part of body mass: ~ 50%), contract constantly to produce heat to help maintain body temperature, (also shivering: no energy conversion is 100% efficient so some of energy from ATP hydrolysis is "wasted" as heat).
MULTIunit smooth muscle characteristics: 1. Thick and thin filaments: (yes/no) 2. Sarcomeres-banding pattern: (yes/no) 3. Transverse tubules: (yes/no) 4.Sarcoplasmic reticulum: (+,++,++++) 5.Gap junctions b/w cells: (Yes/no/few) 6. Source of activating calcium: (Sr/extracellular) 7.Site of Ca++ regulation: (Troponin/myosin) 8.Speed of Contraction: (Fast/slow) 9.Spontaneous production of AP by pacemakers: (Yes/No) 10. Tone (low levels of maintained tension in the absence of external stimuli): (Yes/no) 11.Effect of nerve stimulation: (excitation or inhibition) 12. Physiological effects of hormones on excitability and contraction: (Yes/No)
1. Yes 2. No 3. No 4. + 5. Few 6.SR and extracellular 7. Myosin 8. Very Slow 9. No 10. No 11. Excitation or inhibition 12.Yes
Cardiac Muscle characteristics: 1. Thick and thin filaments: (yes/no) 2. Sarcomeres-banding pattern: (yes/no) 3. Transverse tubules: (yes/no) 4.Sarcoplasmic reticulum: (+,++,++++) 5.Gap junctions b/w cells: (Yes/no/few) 6. Source of activating calcium: (Sr/extracellular) 7.Site of Ca++ regulation: (Troponin/myosin) 8.Speed of Contraction: (Fast/slow) 9.Spontaneous production of AP by pacemakers: (Yes/No) 10. Tone (low levels of maintained tension in the absence of external stimuli): (Yes/no) 11.Effect of nerve stimulation: (excitation or inhibition) 12. Physiological effects of hormones on excitability and contraction: (Yes/No)
1. Yes 2. Yes 3. Yes 4. ++ 5. Yes 6.SR and extracellular 7. Troponin 8. Slow 9. Yes in certain fibers, but most not spontaneously active 10. no 11. Excitation or inhibition 12. Yes
Skeletal muscle characteristics: 1. Thick and thin filaments: (yes/no) 2. Sarcomeres-banding pattern: (yes/no) 3. Transverse tubules: (yes/no) 4.Sarcoplasmic reticulum: (+,++,++++) 5.Gap junctions b/w cells: (Yes/no/few) 6. Source of activating calcium: (Sr/extracellular) 7.Site of Ca++ regulation: (Troponin/myosin) 8.Speed of Contraction: (Fast/slow) 9.Spontaneous production of AP by pacemakers: (Yes/No) 10. Tone (low levels of maintained tension in the absence of external stimuli): (Yes/no) 11.Effect of nerve stimulation: (excitation or inhibition) 12. Physiological effects of hormones on excitability and contraction: (Yes/No)
1. Yes 2. Yes 3. Yes 4. ++++ 5. No 6.SR 7. Troponin 8. Fast-Slow 9. No 10. No 11. Excitation 12.No
SINGLE-unit Smooth muscle characteristics: 1. Thick and thin filaments: (yes/no) 2. Sarcomeres-banding pattern: (yes/no) 3. Transverse tubules: (yes/no) 4.Sarcoplasmic reticulum: (+,++,++++) 5.Gap junctions b/w cells: (Yes/no/few) 6. Source of activating calcium: (Sr/extracellular) 7.Site of Ca++ regulation: (Troponin/myosin) 8.Speed of Contraction: (Fast/slow) 9.Spontaneous production of AP by pacemakers: (Yes/No) 10. Tone (low levels of maintained tension in the absence of external stimuli): (Yes/no) 11.Effect of nerve stimulation: (excitation or inhibition) 12. Physiological effects of hormones on excitability and contraction: (Yes/No)
1. yes 2. No 3. No 4. + 5. Yes 6.SR and Extracellular 7. Myosin 8. Very slow 9. Yes 10. Yes 11. Excitation or inhibition 12.Yes
How does smooth muscle contract?
3-D and therefore it changes volume
Which direction do smooth muscles contract in?
3D to change volume
Which of these does not change when skeletal muscle contracts? A. I-Band B. H-Zone C. Sacromere length D. A-Band
A-Band Lovely! Only the A-Band does not change as it represents the absolute length of the thick filaments, not an overlap.
Smooth muscle is not under conscious control, it is controlled by the ___ (__________ ________ _________) and is only sparsely innervated often the initiating depolarization/contraction spreads across the muscle similarly to cardiac muscle via gap junctions.
ANS (Visceral motor system)
What is termed the thin filament? A. Actin B. Myosin C. Troponin D. Tropomyosin
Actin Well done! Note than the double stranded actin polymer (F-actin) is composed of G-actin monomers that each have a binding site for ADP/crossbridge formation site (normally obscured by tropomyosin).
Aerobic training, (marathon runners!), increases _________ density to ↑fuel supply and O2 delivery/↑metabolite and CO2 removal: this gives _________ not power.
Aerobic training, (marathon runners!), increases capillary density to ↑fuel supply and O2 delivery/↑metabolite and CO2 removal: this gives endurance not power.
All 3 types of muscle tissue work by the interaction of _______________ composed of the proteins _______ and ____________ which hydrolyze ___ to generate force by contracting, (↑overlap: "___________ filament theory").
All 3 types work by the interaction of myofilaments composed of the proteins actin and myosin which hydrolyze ATP to generate force by contracting, (↑overlap: "sliding filament theory").
Which of these mechanisms are utilized by skeletal muscle to maintain adequate ATP for contraction? A. Glycolysis (anaerobic) B. Kreb cycle (aerobic) C. Transfere from creatine D. All of the above
All of the above Correct! Remember skeletal muscle can store glucose as glycogen and utilize fatty acids via beta-oxidation and the Kreb cycle.
Although obviously striated suggesting contraction in 1-D like skeletal muscle, there are several layers of _______ muscle arranged at different orientations so overall the contraction is in ___ -D and __________ a volume
Although obviously striated suggesting contraction in 1-D like skeletal muscle, there are several layers of cardiac muscle arranged at different orientations so overall the contraction is in 3-D and decreases a volume,
Myoglobin
An oxygen-storing, pigmented protein in muscle cells that carries oxygen
Sacromere
Basic contracting unit of muscle cell consits of actin and myosin filaments between z-lines in a muscle cell
Because each muscle normally contains a mix of these fiber types, each muscle can perform different tasks at different times: calf muscles for example use __________ fibers, (IIx), for short sprints, _____ __________ for long distance running, (IIa), and ____ _______, (I), to maintain the standing position.
Because each muscle normally contains a mix of these fiber types, each muscle can perform different tasks at different times: calf muscles for example use glycolytic fibers, (IIx), for short sprints, fast oxidative for long distance running, (IIa), and slow oxidative, (I), to maintain the standing position.
What are sites of attachment for tendons?
Bone "features" or protuberances such as tubercles, trochanters and crests are sites of attachment for tendons
Why does cardiac muscle have gap junctions?
CARDIAC HAS GAP JUNCTIONS BECAUSE THAT'S HOW THE HEART WORKS. YOU START EXCITING IT AT THE PACEMAKER CELL AND THE EXCITATION TRAVELS FROM CELL TO CELL IN THE CORRECT WAY IN ORGANIZED PATTERN IN THE HEART. THE HEART CONTRACTS IN A CYCLE. WHEN YOU HAVE A HEART ATTACK YOUR VENTRICLES CAN BE CONTRACTING 300 TIMES A MINUTE. CARDIAC OUTPUT IS ZERO BECAUSE ITS NOT CYCLING PROPERLY. THE HEART HAS TO FILL AND THEN EMPTY.
What triggers contraction?
Ca2+ acting as a 2o messenger (from both internal and external sources).
What is the key mediator of all muscle mechanism of contraction?
Calcium
What is the calcium sensor in smooth muscle? A. Calmodulin B. Myosin light chain kinase C. Troponin D. Ca2+- ATP'ase
Calmodulin Unlike skeletal and cardiac (similar muscles), smooth does not use ionic calcium but calcium complexed to the calcium sensor calmodulin which in turn activates myosin light chain kinase. Further evidence that smooth was the earlier, primitive, slow muscle.
Unlike other types of muscle these cells are branched and join together at complex junctions calledintercalated discs through which adjacent cells communicate via gap junctions, (allowing ions to flow between cells).
Cardiac muscle cells
Cardiac muscle is ________ and contracts by a similar mechanism to that of ________.
Cardiac muscle is striated and contracts by a similar mechanism to that of skeletal.
Cardiac muscle tissue is only found in the wall of the heart which contracts to propel blood through the cardiovascular system: shows obvious ______________- like skeletal muscle and is ____-_____________, ("myogenic:" see later), but is modulated subconsciously by the ANS, (visceral motor system).
Cardiac muscle tissue is only found in the wall of the heart which contracts to propel blood through the cardiovascular system: shows obvious striations like skeletal muscle and is self-excitatory, ("myogenic:" see later), but is modulated subconsciously by the ANS, (visceral motor system).
______ or "______" attachments are very short so it appears that the muscle tissue itself is connected to the bone
Direct or Fleshy
These connective tissue attachments are linked directly to the contractile filaments via structural proteins so ensuring a transfer of the force generated.
Direct/indirect muscle attachments of the skeletal muscle
Fascicle (portion of the muscle)
Discrete bundle of muscle cells, segregated from the rest of the muscle by a connective tissue sheath
muscle fiber is surrounded by ______________
ENDomysium
Muscle (organ) is covered externally by __________
EPImysium
Each skeletal muscle also contains ___________ tissue, (division and attachment), ______ _______ and ___________ ______ (NMJ).
Each skeletal muscle also contains connective tissue, (division and attachment), blood vessels and innervating nerves (NMJ).
Each skeletal muscle fiber has its own nerve supply, which causes it to contract via the specialized ___, there are no "failures" unlike at most central synapses where there is only a certain probability of NT release, (increased by facilitation, augmentation and PTP of course), and no guarantee that this will generate an __ in the postsynaptic neuron; here there is a 100% probability of release and a muscle AP is _________ generated.
Each skeletal muscle fiber has its own nerve supply, which causes it to contract via the specialized NMJ, there are no "failures" unlike at most central synapses where there is only a certain probability of NT release, (increased by facilitation, augmentation and PTP of course), and no guarantee that this will generate an AP in the postsynaptic neuron; here there is a 100% probability of release and a muscle AP is always generated.
muscle fiber (Cell)
Elongated multinucleate cell; has a banded (striated) appearance. Surrounded by the endomysium.
Which connective tissue layer surrounds the entire skeletal muscle? A. Endomysium B. Perimysium C. Epimysium
Epimysium
Even under abnormal/"fight or flight" conditions skeletal muscle requires insulin to be able to use glucose? TRUE OR FALSE
FALSE Logically adrenaline ("fight or flight") has to supersede everything to ensure survival and therefor does allow skeletal muscle to use glucose even in the absence of insulin.
TRUE or FALSE: Skeletal muscle fibers are all the same
FALSE. Not all skeletal muscle fibers are the same: they can be categorized according to how they obtain their ATP,(anaerobically via glycolysis vs. aerobically via the Krebs cycle), and by how rapidly, (velocity), they can contract, (dependent on ATP'ase activity).
The cardiocyte (heart muscle cell) action potential is similar to that of a neuron or skeletal muscle fiber? TRUE OR FALSE
False It am not! It is significantly different as it contains a large calcium component which DOES change the membrane potential.
A high ration of muscle fibers to motorneurons gives greater control than a low ratio? True or False
False It is the opposite; low ratio gives greater control.
"I pity the fool that gets this sucka wrong!" The T-system conducts the decremental action potential deep within the muscle so all the sarcoplasmic reticulum releases calcium simultaneously? TRUE OR FALSE
False It's totally correct EXCEPT for the word decremental- action potentials are regenerated fully and are NOT decremental!
Which skeletal muscle fiber type would suit a sprinter? A. Slow-oxidative B. Slow-glycolytic C. Fast-oxidative D.Fast-glycolytic
Fast-glycolytic Very fast so very powerful but anaerobic so no endurance- oxygen debt rapidly develops as metabolic acidosis occurs.
Fibers are in fact _________________ cells produced by ______________ several cells and have multiple nuclei (↑______________________)
Fibers are in fact specialized cells produced by merging several cells and have multiple nuclei (↑differentiated)
intercalated discs contain ___ _________ which allows the passive spread of excitation
Gap Junctions
Generally each skeletal muscle is supplied by one _____, one ______ and one or more _____ all entering together mid-muscle: all branch extensively in order to supply individual fibers.
Generally each skeletal muscle is supplied by one nerve, one artery and one or more veins all entering together mid-muscle: all branch extensively in order to supply individual fibers.
Which of these mechanisms utilized by skeletal muscle to maintain adequate ATP for contraction is severely limited/very short term? A. Glycolysis (anaerobic) B. Kreb cycle (aerobic) C. Transfere from creatine
Glycolysis (anaerobic) Good job! Yes anaerobic metabolism (glycolysis alone) cannot be tolerated for long as lactate accumulates and the pH plummets (metabolic acidosis).
Smooth muscle regulation of contraction
INvoluntary
"_______" attachments have a long connective tissue tendon, (composed of dense regular connective tissue which has great strength in one direction [1-D again!]), or a flat sheet of connective tissue called an aponeurosis.
Indirect
Cardiac muscle regulation of contraction
Involuntary
Smooth muscle body location
Mostly in walls of hollow organs, such as the stomach, respiratory tubes, bladder, blood vessels, and uterus
What is termed the thick filament? A. Actin B. Myosin C. Troponin D. Tropomyosin
Myosin Remember, myosin is composed of 2 heavy and 4 light chains.
Do skeletal muscles have Gap junctions?
NO, there is no presence of Gap junctions in skeletal muscles. Fibers have to be individually told what to do (nicotinic receptors, mechanism 1, cation channel)
What is Starling's Law?
Normally cardiac muscle cells are not stretched but during ↑cardiac output, (as during SNS stimulation),venous return increases greatly so stretching the cardiac muscle cells, (also called myocytes) which in turn results in ↑generation of force and ventricular emptying, (Starling's Law).
How is smooth muscle arranged?
Often found in multiple layers perpendicular to each other to produce a "wave" of contraction as occurs duringperistalsis in the GI tract.
Fascicle is surrounded by ________
PERImysium
Which type of fiber is not found in the human body?
SLOW GLYCOLYTIC
Which muscle types have striations?
Skeletal and cardiac
Out of the 3 muscle types, which one is the most evolved?
Skeletal is most evolved and specialized cardiac is like skeletal but less evolved and less specialized
This connective tissue works together to bind the muscle fibers together, ensure parallel alignment, ("1-D" contraction), and are continuous with tendons that attach the skeletal muscles to the skeleton: also responsible for muscle elasticity.
Skeletal muscle
Which of these muscle types has no gap junctions? A. Multi-unit smooth muscle B. Cardiac muscle C. Single-unit smooth muscle D. Skeletal muscle
Skeletal muscle Yes sir! Multi-unit smooth muscle has some but only skeletal has none.
Skeletal muscle tissue is packaged into ........
Skeletal muscle tissue is packaged into discrete skeletal muscles that are attached to and move the skeleton: shows obvious striations, (contracts in one direction only ["1-D"]), and is subject to voluntary control.
Skeletal muscles invariably cross at least one moveable joint: usually causes one bone to move relative to another and the connection to this bone is called the _________ whereas the connection to the bone that does not move, (or moves less relatively), is termed the ______; in the appendicular skeleton, (= limbs), the origin is usually more ________ to the insertion, (and visa versa).
Skeletal muscles invariably cross at least one moveable joint: usually causes one bone to move relative to another and the connection to this bone is called the insertion whereas the connection to the bone that does not move, (or moves less relatively), is termed the origin; in the appendicular skeleton, (= limbs), the origin is usually more proximal to the insertion, (and visa versa).
Skeletal muscles vary widely in _____ to suit ________
Skeletal muscles vary widely in shape to suit function
Which skeletal muscle fiber type would suit a marathon runner? A. Slow-oxidative B. Slow-glycolytic C. Fast-oxidative D.Fast-glycolytic
Slow-oxidative Not very fast so not very powerful but provide enough oxygen and these puppies will contract all day long.
Why doesn't smooth muscle have striations?
Smooth muscle has no visible striations due to the more "random"/oblique arrangement of the contractile filaments, (3-D!).
Where is smooth muscle found?
Smooth muscle is found in the walls of visceral organs such as the bladder, uterus, blood vessels and GI tract.
Smooth muscle tissue is found in the walls of ___________ ____________ such as the stomach, bladder, airways, blood vessels, etc. where it changes volume: has no obvious _________________, (contracts in all directions ["3-D"]), and is subject to _________________ control by the ANS, (visceral motor system).
Smooth muscle tissue is found in the walls of hollow organs such as the stomach, bladder, airways, blood vessels, etc. where it changes volume: has no obvious striations, (contracts in all directions ["3-D"]), and is subject to subconscious control by the ANS, (visceral motor system).
Which muscle can contract purely by stretching?
Smooth muscle. like the skeletal muscle monosynaptic SC refle), or via hormones.
Describe glycolytic fibers
Some fibers, ("glycolytic"), have ↓number of mitochondria but ↑levels of the glycolytic enzymes plus large stores of glycogen that can be broken down to release glucose very quickly: they have fewer capillaries and contain little myoglobin so are pale in color.
Describe oxidative fibers
Some fibers, ("oxidative"), have ↑number of mitochondria and rely principally on the Krebs cycle for ATP production: accordingly these have a ↑capillary density for adequate blood flow, (= O2 delivery), and contain a pigment similar to a single hemoglobin subunit called myoglobin which binds O2 reversibly and aids in O2diffusion and even acts as a short-term O2 store, (gives fibers their red color).
Some muscles however, attach to ____ or _________ depending on function.
Some muscles however, attach to skin or cartilage depending on function.
Each skeletal muscle fiber has its own nerve supply (True or False)?
TRUE
Virtually all skeletal muscle contractions are tetanic in nature? TRUE OR FALSE
TRUE -Gives a smooth continuous contraction; only your eyelid twitches/blinks.
Which direction do skeletal muscles and cardiac muscles contract in?
The contract in one direction (1D)
What are GAP junctions for?
The presence of GAP junctions in cardiac muscle is to allow ions to flow between adjacent cells.
The rich blood supply reflects the ↑metabolic demand of the process of ___________: capillaries are able to stretch with the muscle
The rich blood supply reflects the ↑metabolic demand of the process of contraction: capillaries are able tostretch with the muscle
There are 3 types of muscle in the body: these include __________, _________ and ____________ muscle and together they can make up virtually 50% of total body mass, (variable!).
There are 3 types of muscle in the body: these include skeletal, cardiac and smooth muscle and together they can make up virtually 50% of total body mass, (variable!).
Training _ _____________ of skeletal muscles by ↑no. of contractile filaments not the number of "cells:" however this process requires more nuclei, (remember these are extremely differentiated/specialized multinucleated cells), which so-called satellite cells that are scattered between the muscle fibers provide.
Training ↑diameter of skeletal muscles by ↑no. of contractile filaments not the number of "cells:" however this process requires more nuclei, (remember these are extremely differentiated/specialized multinucleated cells), which so-called satellite cells that are scattered between the muscle fibers provide.
What is the calcium sensor in skeletal and cardiac muscle? A. Actin B. Myosin C. Troponin D. Tropomyosin
Troponin Troponin has 3 subunits; troponin I has a strong affinity for actin, troponin T for tropomyosin and troponin C for Ca2+.
Under normal conditions skeletal muscle requires insulin to use glucose? TRUE OR FALSE
True Exactly- only allowed to use when glucose is in excess/saving primarily for the CNS!
In skeletal muscle the contraction is ended by primary active transport of calcium back into the sarcoplasmic reticulum? TRUE OR FALSE
True It certainly is! This only occurs after acetylcholine is no longer activating the nicotinic receptors at the NMJ.
In smooth muscle myosin light chain kinase phosphorylates the myosin heads so energizing them? TRUE OR FALSE
True Unlike skeletal and cardiac muscles, phosphorylation/energizing of the myosine requires a separate kinase (less evolved).
Unlike skeletal and cardiac muscle, smooth muscle uses a phosphatase to dephosphorylate activated (phosphorylated) myosin heads and stop contraction? TRUE OR FALSE
True Yes it does! Again, different mechanism to the later muscle types and smooth muscle is typically far slower than other types.
Define - Type I slow oxidative fibers that is found in the body
Type I slow oxidative fibers have ↓ATP'ase activity, (↓velocity), and ↑oxidative capacity, (↑no. mitochondria plus ↑myoglobin), so relying primarily on the Krebs cycle for ATP production: these fibers contract slowly, are extremely resistant to fatigue as long as enough O2 is available but are usually thin and therefore do not generate much force; good for prolonged contractions, (examples of muscles composed primarily of this type of fiber include the postural muscles of the lower back).
What is the function of skeletal muscle?
Voluntary movement; locomotion; manipulation of the environment; facial expression; voluntary control
Cardiac muscle body location
Walls of the heart
a ______ unit is the __________ and all the individual skeletal muscle fibers that it innervates, (branching axon). Recruiting more _____ units increases the overall contraction/force generated: a low ratio of _____________ to fibers gives greater control and visa versa.
a motor unit is the motoneurone and all the individual skeletal muscle fibers that it innervates, (branching axon). Recruiting more motor units increases the overall contraction/force generated: a low ratio of motoneurons to fibers gives greater control and visa versa.
What is the function of cardiac cells?
as it contracts. it propels blood into the circulation; involuntary control
Skeletal muscle Body location
attached to bones or (some facial muscle) to skin
Many skeletal muscles span 2 or more joints and are termed
biarticular, (2 joints), or "multijoint" (> 2).
Cardiac muscle cell shape and appearance
branching chains of cells; uni- or binucleate, striations; intercalated discs
Describe a cardiac cell
branching, striated, generally uninucleate cell that interdigitates at specialized junctions (intercalated discs)
Cardiac muscle is the muscle tissue in the walls of the heart: it is arranged in ____________________________________________: contractions of cardiac muscle propel the blood through the circulatory system.
bundles to form the myocardium
Which muscle cell is isolated cells that will contract spontaneously, ("myogenic").
cardiac muscle cells
________ ______ ____ contain ↑no. of mitochondria for aerobic ATP production, (Krebs cycle), and luckily are highly resistant to fatigue!
cardiac muscle cells
Define muscle (organ)
consists of hundreds to thousands of muscle cells, plus connective tissue wrappings, blood vessels, and nerve fibers
Like cardiac muscle smooth muscle is only surrounded by ____________.
endomysium
Smooth muscle connective tissue components
endomysium
cardiac muscle only has the inner connective tissue capsule, (__________), which directly attaches to the fibrous skeleton of the heart.
endomysium
Cardiac muscle connective tissue components
endomysium attached to fibrous skeleton of heart
Skeletal muscle connective tissue components
epimysium, perimysium, and endomysium
What is the concept of the "motor unit"?
for skeletal muscles only requiring relatively "coarse" control, one motor neuron may innervate many fibers whereas if "fine" control is required, (fingers and facial muscles for example), the ratio of motor neurons to fiber innervation is far less.
What is the basis of contraction?
interaction between the contractile proteins actin and myosin.
Fiber types can be ___________________ however by an appropriate training regime: they revert though if the training stops.
interconverted
myogenic
isolated cells that will contract spontaneously
What is structure and organizational level of a skeletal muscle?
muscle (organic) --> fascicle (portion of the muscle) --> muscle fiber (cell) --> myofibril (organelle containing myofilaments)
what is the function of smooth muscle cell?
propel substances or objects along internal passageways; involuntary control
myofibril
rodlike contractile element; myofibrils occupy most of the muscle cell volume; appear banded and bands of adjacent myofibrils are aligned; composed if sarcomeres, end to end
Smooth muscle tissue is composed of
separate cells with one nucleus
unlike skeletal muscle, Cardiac muscles appear to be
single cells but they do typically have 1 or 2 central nuclei.
Smooth muscle cell shape and appearance
single, fusiform, uninucleate; no striations
Skeletal muscle cell shape and appearance
single, very long, cylindrical, multinucleate cells with obvious striations
How are they controlled/activated?
skeletal muscle is consciously controlled by the somatic motor system (motor cortex) or spinal reflexes via the ventral horn or CN motorneurons at the NMJ (ACh on nicotinic receptors). Smooth muscle is controlled by the visceral motor system (ANS) subconsciously: unlike skeletal they can be actively contracted and relaxed by both the ANS transmitters (NA or ACh acting on adrenergics or muscarinics), modulators and humoral agents. Cardiac muscle is myogenic (spontaneously active/depolarizing pacemaker cells) but is modified (rate and force) by the visceral motor system (ANS) and humoral agents.
What are the 3 types of muscle?
skeletal, smooth and cardiac
Contraction of smooth muscle is usually ____, _________ and highly resistant to ______ as required by its function
slow, sustained and highly resistant to fatigue
Which muscle has relatively low energy requirement means cells have few mitochondria.
smooth muscle
Describe smooth muscle cell
spindle-shaped cells with central uncle; no striations; cells arranged closely to form sheets.
Skeletal muscles are attached to bones via
strong fibrous connective tissue that extends into the periosteum, (outer connective tissue covering of bones).
Skeletal muscle regulation of contraction
voluntary
Endomysium (inner)
within fascicles each skeletal muscle fiber is surrounded by a layer of fine connective tissue principally composed of reticular fibers.
Muscular tissue has features that distinguish it from other tissue types: -Contractility -Excitability -Extensibility -Elasticity
● Muscular tissue has features that distinguish it from other tissue types: - Contractility: muscle tissue contracts and generates force. - Excitability: nerve signaling, (via NTs), or other factors excite muscle cells which in turn generate electrical signals, (muscle "AP": see later), which ↑intracellular Ca2+, (2o messenger), which in turn triggers contraction. - Extensibility: muscle tissue can be stretched, (skeletal muscle in particular), by an opposing, antagonisticmuscle. - Elasticity: after stretching muscle tissue can recoil passively to its resting length, (not the monosynapticSC-mediated stretch reflex: a stretch receptor was stimulated there).
