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69 Cards in this Set
- Front
- Back
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What are the three types of muscle tissue in the human body? |
- cardiac muscle tissue: located in the heart - smooth muscle tissue: located in the walls of hollow visceral organs and blood vessels - skeletal muscle tissue: located in skeletal muscles |
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Characteristics of skeletal muscle |
- makes up approx. 40-45% of total body weight - exhibits striated (banded) appearance: striated muscle - under voluntary control - attaches to 2 bones, crosses the joint located between them - typically has 2 attachments, ea. onto a bone - some skeletal muscles have more than 2 bony attachments - some attach into soft tissue instead of bone
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Describe the big picture of how skeletal muscles work |
- it can contract, attempting to shorten toward its center - the contraction creates a pulling force on the bony attachments of the muscle - if the pulling force is strong enough on or both of the bones to which the muscle is attached will be pulled toward the center of the muscle; the movement of the bones creates movement of a body part |
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Define Organ |
- made up of 2 or more different tissues, all acting together for one function.
- in the case of skeletal muscle that function is to contract and create a pulling force |
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Tissue components of a skeletal muscle |
- skeletal muscle is an organ of the muscular system - contains more than 1 type of tissue: 1. skeletal muscle tissue 2. fibrous fascial connective tissue
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Characteristics of skeletal muscle tissue |
- compose of skeletal muscle cells which are the major structural and functional units of a muscle - they are major structural units of a muscle in that the majority of a muscle is made up of muscle cells - they are the major functional units in that they do the work of a muscle (i.e the cells contract) |
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Characteristics of fibrous fascia |
- provides a structural framework for the muscle by enveloping the muscle tissue - fibrous fascia wraps around the entire muscle , groups of muscle cells w/in the muscle and ea. individual muscle cell -continues beyond the muscle @ both ends to create the tendons that attach the muscle to its bony attachment site. |
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What are the functions of the nerves and blood vessels contained in skeletal muscles? |
- nerves carry both motor message from the CNS to the muscle to instruct the muscle to contract and sensory messages from the muscle to the CNS that inform the spinal cord & brain as to the state of the muscle
- blood vessels bring nutrients to the muscle tissue and drain away waste products of the muscle's metabolism |
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Characteristics of skeletal muscle cells |
- has an elongated cylindric shape - is also called a muscle fiber - vary from approx. 1/2in to 20in in length - skeletal muscle is made up of many muscle fibers (or muscle cells) that run lengthwise w/in the muscle - the manner in which they run is called the architecture of the muscle fiber - it is rare for muscle fibers to run the entire length of a muscle; 1. they either run end to end in series 2. or lay parallel and overlap one another w/in the muscle. |
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What are fascicles? |
- bundles of muscle fibers - a fascicle can contain as many as 200 muscle fibers - skeletal muscle is composed of a number of fascicles |
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Describe muscular fascia (or deep fascia)? |
-tissue that creates the structural organization of a muscle - tough fibrous fascia connective tissue - major component of muscular fascia is collagen - a small component of elastin fibers also exist - it is uniform in composition - named according to its location |
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Greek roots |
Mys: refers to muscle epi: means upon peri: means around endo: means within |
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What are three types of muscular fascia? (pg 385) |
- endomysium: fibrous fascia that surrounds ea. individual muscle fiber - perimysium: fibrous fascia that surrounds a group of muscle fibers, dividing the muscle into the bundles called fascicles - epimysium: surrounds an entire muscle
**all 3 layers of fibrous fascia blend together and continue beyond the muscle to attach the muscle to a bone
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Functions of Muscular fascia (fibrous fascia) |
- the role of the fascial attachment is to xfer force of the muscle contraction to the bone - serve to bind fibers together laterally - creates a thick intermuscular septa that separate the muscles of the body and provide a site of attachment for adjacent muscles - provide pathways for the nerves and blood vessels that innervate and feed nutrients to the muscle fibers
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Describe lateral forces transmission |
- the endomysia of adjacent fibers create fascial connection that can serve to xmit the force of contraction laterally from one fiber to the adjacent fibers. - if fibers A and B are adjacent to ea. other and fiber A contracts and fiber B does not, the force of contraction of fiber A will be xferred to fiber B, causing a pulling force in fiber B, even though fiber B was not stimulated to contract.
- can also occur between adjacent fascicles of a muscle via their perimysia and has been shown to occur between adjacent muscles via their epimysia.
- can xmit more than 30% of contractile force from one muscle to the adjacent relaxed muscle |
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Describe a tendon |
- round and cordlike muscular fascia that attaches a muscle to a bone.
* regarding composition tendons and aponeurosis are identical; they only differ in shape |
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Describe aponeurosis |
- broad and flat muscular fascia - b/c of its shape it can spread out the force of a muscle's pull on its attachment site; can allow for the muscle to withstand the concentrated force of a tendon pulling on it.
* regarding composition tendons and aponeurosis are identical; they only differ in shape |
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what is another name for a muscle? (myofascial unit) |
myofascial unit: muscles and its fascial tissues are one unit that cannot really be structurally or functionally separated.
myo: referring to the muscular tissue component fascial: refers to the fibrous fascial component |
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What are the cytoplasmic organelle, or cellular structures of skeletal muscle fibers |
-sarcoplasm: the cytoplasm of a skeletal muscle fiber - sarcoplasmic reticulum: the endoplasmic reticulum - sarcolemma: the cell membrane
*sarco is the Greek word root denoting flesh (muscle tissue) |
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Describe the microanatomy of skeletal muscle fibers |
- they are multinucleate (contain many nucleai) b/c ea. muscle fiber (cell) developed from multiple stem cells grouping together - they are rich in mitochondria which creates adenosine triphosphate (ATP) molecules aerobically to furnish muscle with energy - approx. 1000 myofibrils; longitudinally oriented w/in the cytoplasm, running the entire length of the muscle fiber |
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what is myoglobin? |
- an oxygen binding molecule - similar to hemoglobin of the red blood cells, but has a greater ability to bind to oxygen |
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Describe sarcomeres |
- myofibrils are composed of units called sarcomeres - sarcomeres are laid end to end from one end of the myofibril to the other end (also lie side by side) - very short - approx. 10,000 sarcormeres found per linear inch of myofibrils - contain protein filaments called actin and myosin |
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What are Z-lines? |
- boundaries of ea. sarcomere |
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describe actin filaments |
- thin - attached to Z-lines at both ends of a sarcomere |
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describe myosin filaments |
- thick - not attached to Z-lines - located in the center of the sarcomere - have globular projections known as heads - ea. myosin head sticks out toward the actin filament |
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what causes striation in skeletal muscle tissue |
- the overlapping of the actin and myosin filaments |
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What is the actual functional unit of skeletal muscle tissue? |
-sarcomere (myofibrils of muscle fibers) - sarcomeres perform the essential physiologic function of contraction that makes muscle tissue unique |
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Describe the sliding filament mechanism (or theory)
- AKA: ratchet theory |
- rachet denotes the idea of how myosin's cross-bridges pull on the actin filament in a ratchetlike manner
- myosin cross-bridge pulls on the actin filament, exerting tension, then it relaxes by letting go, exerts tension once again, and then relaxes again. this cycle is repeated many times
- this is how sarcomeres shorten as actin and myosin filaments slide along ea. other |
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What are the steps of the sliding filament mechanism? |
1. message is sent from the nervous system that tell muscle fibers to contract. 2. this message causes the sarcoplasmic reticulum to release stored calcium into the sarcoplasm (cytoplasm) 3. Calcium ions attach onto the actin filaments, exposing actin filament binding sites (also called actin filament ACTIVE sites) 4. Myosin heads attach onto these exposed binding sites of the actin filaments, creating cross-bridges between the myosin and actin filaments
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Steps of the sliding filament mechanism cont'd. |
5. Ea. myosin cross-bridge bends, creating a pulling force that pulls the actin filament in towards the center of the sarcomere. 6. the cross-bridges break, myosin heads reattach onto the next binding site of actin filaments, forming new cross-bridges which then bend, further pulling the actin filaments in toward the center of the sarcomere.
(there are thousands of cross-bridges so when some break, others remain in attached so that the actin filament does not slip back) |
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Steps of the sliding filament mechanism cont'd. |
7. process repeats as long as the message to contract is given to the muscle by the nervous system 8. b/c actin filaments are attached to the z-line of the sarcomere, the z-lines are pulled in toward the center of the sarcomere 9. when z-lines are pulled in toward the center of the sarcomere, the sarcomere shortens 10. when all the sarcomere of a myofibril shorten, the myofibril also shortens -when all the myofibril shorten, the muscle fiber shortens -when enough muscle fibers shorten, the muscle shortens exerting force on the bon |
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What is the energy source that drives the sliding filament mechanism? |
-adenosine triphosphate (ATP) molecules |
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What 2 steps of the sliding filament mechanism require the expenditure of energy by ATP molecules? |
1. energy must be furnished by ATP molecules for the myosin-actin cross-bridges to break
2. the reuptake of calcium back into the sarcoplasmic reticulum when a muscle contraction is completed |
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What are the 4 steps in which ATP molecules are supplied to provide energy needed for the sliding filament mechanism? |
1. Stored ATP (the amount of stored ATP in the muscle fiber is very small and depletes quickly) 2. Regeneration of ATP from stored creatine phosphate molecules present & stored in the muscle fiber 3. Regeneration of ATP from anaerobic (w/o oxygen) breakdown of glucose also called respiration of glucose. (this happens after creatine phosphate molecules are depleted 4. Regeneration of ATP from aerobic breakdown of glucose |
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What are 2 ways glucose is broken down? |
-anaerobically (glycolysis): w/o oxygen; this happens first and occurs w/in the sarcoplasm of the cell. If a continuing supply of energy is still needed, the muscle fiber gradually xsitions to the breakdown of glucose aerobically w/in the mitochondria
- aerobic breakdown of glucose w/in mitochondria requires oxygen and therefore requires circulation of blood to deliver this oxygen; this increase circulation places a demand on the heart to pump more blood and thereby exercises the heart. |
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Describe ATP |
- an adenosine base molecule w/ 3 phosphate groups attached. -bonds between the groups are broken to produce energy for use by the sliding filament mechanism - once one bond is broken it becomes adenosine DIPHOSPHATE (2 phosphate groups) - ADP can be converted back to ATP so ATP is like a rechargeable battery. |
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What are the by-products of glycolysis? |
-2 ATP molecules - waste product: lactic acid |
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What is aerobic breakdown of glucose called? |
-Krebs cycle or the citric acid cycle - Krebs cycle creates approx. 36 molecules of ATP for ea. molecule of broken down glucose making it more efficient that glycolysis. - waste products are carbon dioxide and water |
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What is oxygen debt? |
- if a person exercises and overcomes the ability of the cardiovascular system to deliver oxygen for the aerobic breakdown of glucose, then muscle fibers must rely on anaerobic breakdown of glucose to a greater degree. -b/c the breakdown of glucose creates lactic acid as a waste product, lactic acid can build up in the muscles (lactic acid is usually xported to the liver where it can be converted back to glucose- this conversion requires oxygen) -the oxygen needed to convert lactic acid back to glucose can be looked at as a debt the body owes itself -oxygen debt explains why a person may continue to breath deeply even after exercise is completed. |
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what is a synaptic cleft? |
- the small space located between a motor neuron and muscle fiber (the motor neuron does not attach/connect directly to the muscle fiber)
Also known as a synaptic gap or synapse |
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What are neurotransmitters? |
- molecules released into the synapse by motor neuron which xmit the neural message for contraction to the muscle fiber. |
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What is acetylcholine? |
- the neurotransmitter that is released between motor neurons and skeletal muscle fibers |
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What is acetylcholinesterase? |
The enzyme that removes acetylcholine when a motor neuron is no longer stimulated to secrete acetylcholine
The acetylcholine that was secreted and is present w/in a synaptic cleft is removed by acetylcholinesterase |
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What is a neuromuscular junction? |
The location where the motor neuron and muscle fiber meet |
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What is a motor end plate? |
the sarcolemma (cell membrane) of the muscle fiber, located at the neuromuscular junction, that is specialized to receive the neurotransmitters of the motor neuron. |
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What is human resting muscle tone (HRMT) |
low baseline level of contraction believed to result from a small but constant presence of calcium ions in the sarcoplasm. |
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What is a motor unit? |
- one motor neuron and all the muscle fibers it controls (i.e. with which it synapses)
- motor neurons branch numerous times to synapse with a number of muscle fibers, so in this manner it controls a number of muscle fibers |
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Explain the all- or-none- response law |
- when a message for contraction is sent from the nervous system to a muscle fiber, that message instructs the muscle fiber to contract completely. If no message is sent then the muscle fiber relaxes completely. - Therefore the muscle fiber contraction is an all or nothing mechanism. -applies to the sarcomere, the myofibril, the muscle fiber, and the motor unit b/c all these structural levels of muscle tissue are innervated by a single motor neuron that either carries the message to contract or does not carry the message to contract. - this law DOES NOT apply to an entire skeletal muscle. A skeletal muscle CAN have partial contractions. |
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Describe the sarcomere structure |
- a myofibril is made up of many sarcomeres that are arranged both next to one another and also end to end along the length of the sarcomere. -ea. sarcomere is made up of actin and myosin filaments arranged in a hexangular fashion so that myosin filament is located in that center of the sarcomere and 6 actin filaments are located around ea. end of the myosin filament, partially overlapping it; this gives is a banded striated appearance. |
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What are the two main bands of a sarcomere? |
1. A-band: anisotropic - dark & is defined by the presence of myosin. B/c myosin is the center of a sarcomere, the A-band is also located in the center of a sarcomere (in the A-band there are regions that have only myosin and other regions that have both myosin and actin) 2. I-band: isotropic - light and defined by where only actin filaments are located. I-band is partially located w/in the adjacent sarcomeres |
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What are the smaller bands located w/in the A & I-bands? |
H-band: is the region of the A-band that contains only myosin M-band: AKA M-line, is w/in H-band (which in turn is located in the A-band) at the center of the myosin molecule Z-band: usually referred to as the Z-line, is at the center of the I-band; it is the border between two adjacent sarcomeres |
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Describe Myosin |
- myosin filament is actually made up of many myosin molecules - ea. indiv myosin molecules has a shape that resembles a golf club - arranged so that half of them have their heads sticking out at one end of the sarcomere and the other half of them have there heads sticking out the other end of the sarcomere. |
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What are the 2 parts of a myosin molecule? |
- myosin tail and the myosin head - the tail is the main length of the myosin molecule; it is called light meromyosin component -the head is that part that sticks out and attach onto the actin filament, forming the actin-myosin cross-bridge; this cross-bridge is called heavy meromysin component |
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What are the 2 parts of the heavy meromysin |
1. the head (also known as the S1 fragment) 2. the neck (also known as the S2 fragment) |
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Describe actin filament |
- made up of 3 separate protein molecules: 1. actin, 2. troponin, 3. tropomyosin - the bulk of the actin filament is composed of many small spheric actin molecules that are strung together like beads, forming 2 strands that twist around ea. other - when calcium ions attach to troponin molecules of the actin filament, the troponin molecules move the tropomyosin molecules out of the way so that binding (active) sites of actin are exposed. |
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What is Tintin? |
- a protein contained in sarcomere - the largest protein in the human body - contains approx. 27,000 amino acids - forms much of the cytoskeletal framework for the sarcomere, connecting the myosin filament to the Z-line. For this reason it is also called connectin. - 6 tintin molecules attach to ea. side of the myosin filament - ea. tintin molecule runs half the length of the sarcomere, connecting from the myosin filament at the M-Line in the center of the sarcomere to the Z-line @ the border of the sarcomere |
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More about Tintin |
- Tintin is found in both the A & I bands - Tintin enters the I-band and approximates the actin filament on the way to the Z-line - PEVK section, the portion of the tintin molecule that is located in the I-band region - PEVK stands for the amino acids: proline, glutamate, valine and lysine. - the PEVK region of tintin is said to be primarily responsible for the elasticity and passive tension of extended muscle/myofascial tissue - may also be responsible for chronic muscle stiffness caused by increased adhesions between tintin and the myosin filament or between tintin and actin filaments |
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What 2 factors cause muscle stiffness? |
- active contraction via the sliding filament mechanism - fascial adhesions |
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What are 2 types of muscle fibers?
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- red fibers (red slow-twitch fibers) - white fibers (white fast-twitch fibers) - W/in a muscle, motor units are homogenous so a motor unit is either all red slow-twitch or all white fast-twitch - Muscles have a MIX of red and white fibers - small motor units are comprised of red slow twitch fibers - large motor units are comprised of white slow twitch fibers
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Characteristics of Red slow-twitch fibers |
- are red because they have a rich blood supply - slow to contract from the instant that they receive the impulse to contract from the nervous system - take 1/10 sec to reach max tension - usually small in size |
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Characteristics of white fast-twitch fibers |
- white because they do not have a rich blood supply - they contract quickly when they are directed to contract by the nervous system - take approx. 1/20 sec to reach max tension - usually larger in size
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What accounts for the relative speed w/ which the different types of muscle fibers contract? |
- smaller motor units of red muscle fibers are innervated by smaller-diameter motor neurons that carry the direction to contract at a slower rate from the CNS than the larger diameter motor units that innervate the larger motor units, composed of white fibers |
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Which fibers contract slowly and do not create powerful contractions and are able to hold their contraction for long periods of time? Are more plentiful in muscles that exhibit endurance and hold contractions for long periods of time such as deeper postural stabilization muscles? |
Red slow-twitch fibers |
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Which fibers are able to generate faster, more powerful contractions, but they fatigue quickly/easily? - more plentiful in muscles that need to create fast powerful movements but don't have to hold the contraction for a long period of time such as superficial mobility muscles |
White fast-twitch fibers |
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What is the myofascial meridian theory? |
- the concept that muscles operate w/in continuous lines of fascia that span across the body - myofascial meridians are AKA anatomy train - Tom Myers defines anatomy train as a traceable continuum w/in the body of muscles embedded w/in fascial webbing |
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What are the 11 myofascial meridians? |
1. superficial back line 2. superficial front line 3. Lateral line 4. Spiral line 5. Superficial front arm line 6. Deep front arm line 7. Superficial back arm line 8. Deep back arm line 9. Back functional line 10. Front functional line 11. Deep front line |
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What is the importance of myofascial meridian theory? |
- places muscles into larger structural and functional patterns that help explain patterns of strain and movement w/in the body - helps w/ understanding the patterns of muscle contraction - creates a model that explains how forces placed on the body at one site can cause somewhat far-reaching effects in distant sites of the body - tensegrity |
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What is the concept of tensegrity? |
- relates to how the structural integrity and support of the body are created - structural integrity of the body is dependent on compression forces -however myofascial meridian theory views the musculoskeletal body as having continuous lines of pull created by muscles linked to one another in a web or network of fascia - looks at these lines of tension as being responsible for the structural integrity of the body - this concept of structural integrity is tensegrity |
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What is the advantage of a tensegrity structure compared to a compression structure? |
- tensegrity structures are more resilient b/c stresses/forces applied to them are more efficiently transmitted throughout the structure, spreading out and diminishing their effect. Thus no one region of the skeleton bears the entire load of a stress. |
