Flashcards in Module 4 Quiz Deck (136):
What are the 3 types of muscle tissue?
Function of muscle?
Contract and create a pulling force
What are the 2 types of tissue found in skeletal muscle?
Skeletal muscle tissue
Fibrous fascial connective tissue
What are the major structural and major functional units of a muscle?
Muscle cells (make up majority of muscle and they do the contracting)
What is the function of fascial connective tissue?
Structural framework for muscle and becomes tendon.
Transfers force of muscle contraction to bone
Why are there nerves in skeletal muscle?
Carry motor messages from CNS to muscle
Carry sensory messages from muscle to CNS
Why are there blood vessels in skeletal muscle?
Bring needed nutrients to the muscle tissue and drain away waste products of muscle metabolism
What are muscle fibers?
Length of muscle fibers (cells)?
0.5 inch to 20 inches
What is the classic appearance of muscle cells?
What is a fascicle?
Bundles of muscle fibers (up to 200)
What is muscular fascia made of?
Mostly collagen, some elastin
What is the fibrous fascia that surrounds each individual muscle fiber?
What is the fibrous fascia that surrounds a group of muscle fibers, dividing the muscle into fascicles?
What is the fibrous fascia that surrounds an entire muscle?
What is lateral force transmission?
Force of contraction of fiber A will transfer to fiber B even though it was not stimulated to contract.
Occurs through connections of endo-, peri-, and epimysia
What is a tendon?
Muscular fascia that attaches the muscle to a bone or soft tissue (round and cord-like)
What is an aponeurosis?
Muscular fascia that attaches the muscle to bone or soft tissue (broad and flat)
Because tendons and aponeuroses are an integral part of the muscle, muscles are referred to as...
What is intermuscular septa?
Thick muscular fascia that separates muscles of the body and provide a site of attachment for adjacent muscles
What are aponeurotic sheets?
Muscular fascia that expands over large groups of muscles
Where are the nerves and blood vessels located in skeletal muscle?
Within muscular fascia
What are the cellular microstructures in muscle cells?
Why are muscle cells multinucleate?
Muscle fibers developed from multiple stem cells grouping together
Why are muscles rich in mitochondria?
Mitocondria create adenosine triphosphate (ATP) molecules aerobically
What is myoglobin?
oxygen-binding molecule in muscle similar to hemoglobin but has greater ability to bind oxygen
What are myofibrils?
Cytoplasmic organelles that runs the length of the fiber - composed of sarcomeres (that lay side by side)
What is a Z-line?
boundary of a sarcomere
Each sarcomere contains protein filaments called
Where are the actin and myosin filaments within the sarcomere?
Actin filaments are attached to the Z-lines at both ends
Myosin filaments are located in the center of the sarcomere
What causes muscle striation?
Overlapping of actin and myosin filaments
What is the functional unit of skeletal muscle?
Sarcomere (performs the contraction)
What is the physiologic process of a sarcomere celled?
Sliding filament mechanism (also called ratchet theory)
Where does the energy that drives the sliding filament mechanism come from?
Adenosine triphosphate (ATP) molecules
What are the 2 steps of the sliding filament mechanism that require ATP?
1. Energy for myosin-actin cross-bridges to break
2. Reuptake of calcium into sarcoplasmic reticulum when contraction done
What are the 4 steps in which ATP molecules are supplied
1. Stored ATP
2. Regeneration of ATP from stored creatine phosphate
3. Regeneration of ATP from anaerobic breakdown of glucose
4. Regeneration of ATP from aerobic breakdown of glucose
Breakdown of glucose first occurs aerobically or anaerobically?
Where does anaerobic breakdown of glucose occur?
Within the sarcoplasm of muscle cell
Where does aerobic breakdown of glucose occur?
How does aerobic breakdown of glucose exercise the heart?
Requires oxygen which requires increased circulation which increases demand on heart
How does the lack of ATP account for rigor mortis?
ATP required to break myosin-actin cross-bridges.
1. Muscles in state of contraction at death
2. Calcium leaks into sarcoplasmic reticulum and triggers cross-bridges (continues until tissue breaks down)
How is ATP expenditure related to trigger points?
Trigger points squeeze blood vessels, diminish blood flow, and decrease delivery of glucose to muscle cells --> deficiency of ATP production
Decreased ability to break cross-bridges and reuptake calcium
What is the energy crisis hypothesis?
ATP deficiency leading to formation and persistence of trigger points
What is glycolysis?
Anaerobic breakdown of glucose
For each molecule of glucose broken down by glycolysis, what is formed?
2 ATP molecules
Lactic acid (waste)
What is the Kreb's cycle
Aerobic breakdown of glucose
For each molecule of glucose broken down by Kreb's cycle, what is formed?
What is oxygen's role in aerobic metabolism?
Bonds to the carbon atoms created when glucose molecule is broken down to create CO2 which can be easily carried away in the bloodstream and eliminated via the lungs
What is oxygen debt?
When anaerobic metabolism is relied on, lactic acid is a waste product; this is sent to the liver to be turned into glucose
Sending it to the liver requires oxygen - explains why person may continue to breathe deeply after exercise is completed
What is muscle innervation?
When peripheral nerve has ability to direct muscle to contract
What is the small space between muscle fiber and motor neuron?
Synaptic cleft; synaptic gap; synapse
What are neurotransmitters
Molecules released by motor neuron into synapse which transmit neural message for contraction to muscle fiber
What is the neurotransmitter released between motor neurons and muscle fibers?
What happens when neuron no longer secretes acetylcholine?
Neurotransmitter left in synapse is removed by acetylcholinesterase enzyme and muscle relaxes
What is the location where the motor neuron and muscle fiber meet?
What is the motor end plate?
Sarcolemma at neuromuscular junction that is specialized to receive and bind to acetylcholine
What happens when acetylcholine binds to the motor end plate?
An electrical impulse is initiated and travels along the sarcolemma of the entire muscle fiber and then transmitted into the interior of the fiber via T tubules
What are the T tubules?
Transverse tubules which transmit electrical impulse into the fiber from the sarcolemma
What happens when electrical impulse reaches the interior of the muscle fiber?
Triggers sliding filament mechanism by releasing stored calcium from sarcoplasmic reticulum into sarcoplasm
Does the CNS send messages for muscles to relax?
No, it just stops sending the contraction signal
When calcium is no longer present in the sarcoplasm, why can't myosin heads bind with actin?
Binding sites are no longer available
What is muscle memory?
Memory pattern of muscle contractions which resides in the nervous system
What is human resting muscle tone?
Muscle tissue has a low baseline resting muscle tone that is independent of the nervous system (1% of max contractile force of muscle)
How does human resting tone occur?
Small but constant presence of calcium ions in sarcoplasm which expose a small number of active sites on actin filaments, allowing cross-bridges
Why is human resting tone important?
How does human resting tone differ from resting tone?
Resting muscle tone refers to the tone of muscle when it is at rest, which is directed by the nervous system as a result of muscle memory of the gamma motor nervous system
What is a motor unit?
One motor neuron and all the muscle fibers it controls (ie, with which it synapses)
Why are motor units often spread throughout the muscle instead of restricted to fascicular organization?
Because skeletal muscle fibers cannot pass the message to contract from one to another
Where are small motor units typically and why?
Locations where very fine and precise body movements are needed (like extraocular muscles).
Smaller motor units = less fibers per neuron = smaller, finer, precise action
Where are large motor units typically and why?
Locations where large and less precise movement is needed (like gluteus maximus)
Larger motor units = more fibers per neuron = larger, grosser, more powerful action
What is the all-or-none-response law of muscle contraction?
When the nervous system sends message to contract, the muscle fiber contracts completely (100%)
If no message sent, fiber relaxes completely (0%)
Why does the all-or-none-response law not apply to an entire muscle?
Skeletal muscle can have partial contractions since the muscle is innervated by a number of different motor units - some say contract, some don't
Why is partial contraction of a muscle important?
Allows person to generate just the right amount of force for a particular situation
What are the 2 main bands of a sarcomere?
A-band and I-band
What is the A-band?
dark in color; defined by presence of myosin (center of sarcomere)
There is an area of just myosin (H-band) and an area of both actin and myosin
What is the I-band?
light in color; defined by only actin filaments
Partially in one sarcomere and partially in the adjacent sarcomere
What is the H-band?
Region of the A-band that contains only myosin.
What is the M-band (M-line)?
Center of myosin molecule
What is the Z-band (Z-line)
Center of I-band; border between 2 adjacent sarcomeres
What is the myosin filament made of?
Myosin tail (light meromyosin component)
What is the actin filament made of?
What blocks the binding site of actin during rest (prevents connection with myosin head)?
What makes the tropomyosin molecule move out of the way so actin can form a cross-bridge with myosin head?
Calcium ions attach to the troponin molecule which moves the tropomyosin molecules out of the way, which exposes the actin molecule binding site
What is the titin (connectin) protein?
Largest protein in human body; found in sarcomeres; forms cytoskeletal framework for sarcomere, connecting the myosin filament to the Z-line
How many titin molecules surround the myosin filament?
6 (same as actin)
How long is the titin molecule?
Half the length of the sarcomere; connects myosin filament at M-line to the Z-line
(titin is in both A-band and I-band regions)
What does PEVK stand for?
What is the PEVK section?
A portion of the titin molecule located in the I-band region
Function of the PEVK section?
Extremely elastic and extensible; responsible for elasticity and passive tension of extended muscle/myofascial tissue
Might also be responsible for chronic muscle stiffness (adhesions between titin and myosin filament or titin and actin filaments)
Muscle stiffness is considered to be caused by what 2 factors?
1. Active contraction via sliding filament mechanism
2. Fascial adhesions
What direction does the actin filament slide in the sarcomere?
Inward, toward the center of the sarcomere (Z-lines pulled toward M-line)
Can a myosin filament slide along the actin filament?
Yes - if actin filaments of 2 adjacent sarcomeres were to both shorten toward their respective centers, their common Z-line would rupture.
Muscles shorten in which direction?
Toward their center
What are red and white muscle fibers?
Red: slow-twitch fibers
White: fast-twitch fibers
Why are red fibers red? Why are they slow-twitch?
Rich blood supply = red
Slow-twitch because they are slow to contract from instant they receive impulse to contract
Rely on slower process of aerobic respiration
Why are fast-twitch fibers easily fatigued?
Rely on anaerobic metabolism (glycolysis) which only produces 2 ATP per glucose molecule
How long does it take a red and white fiber to reach max tension?
Red: 1/10 of a second
White: 1/20 of a second
Partially due to small red fibers having smaller-diameter motor neurons
Small motor units = red or white fibers?
Large motor units = red or white fibers?
Do intermediate fibers convert and attain characteristics of red or white fibers?
What determines the ratio of red and white fibers in our bodies?
Red slow-twitch fibers are also called (6):
Type I fibers
Slow oxidative fibers
White fast-twitch fibers are also called (6):
Type II fibers
Easily fatigued fibers
Fast glycolytic fibers
Deep postural stabilization muscles are often more red or white?
Red - contract slowly and do not create powerful contractions, but can hold for long periods of time
Superficial mobility muscles are often more red or white?
White - create fast powerful movements for short amount of time
What is myofascial meridian theory?
Muscles operate within continuous lines of fascia that span across the body
How many myofascial meridians are there?
Why is myofascial meridian theory important?
Provides understanding of synergistic patterns of contraction within the body
Explains how forces placed on body at one site can cause somewhat far-reaching effects in distant sites of the body
Based on the meridian theory, would a tight gastrocnemius muscle be felt in the galea aponeurotica of the head?
Only if all the tissues of that particular myofascial meridian are tight (otherwise force absorbed)
What is tensegrity?
Relates to structural integrity and support of the body
Proper posture and balancing of the bones are largely caused by the tensile forces created by muscles within myofascial meridians that act on the skeleton
How does tensegrity work?
A force applied to a bone at any specific point along the skeleton will be transmitted throughout the body along myofascial meridians, diminishing its effect at the local site of application
The structural integirty of the body is dependent on both tensile (myofascial) and ______ forces
compressive (bones stacked on each other)
What is a concentric contraction?
When muscle contracts and shortens
The muscle that is concentrically contracting is called a...
The force necessary to move a body part is usually the force necessary to....
move the weight of the body part (other forces may be involved)
Fully describe the joint action of the brachialis muscle pulling the forearm toward the arm.
Flexion of the forearm at the elbow joint.
Fully describe the joint action of the brachialis muscle pulling the arm toward the forearm
Flexion of the arm at the elbow joint.
If the CNS directs another muscle in the body contract, which may stop or "fix" one of the attachments of the mover muscle, the second muscle that contracts to fix a body part would be called a ...
fixator or stabilizer muscle
What is the most common determinant of which muscle attachment moves?
Typically weight of the body parts (ex: forearm more likely to move than arm since its lighter)
Other determinants: stabilizer muscle contraction or fixing one attachment (like holding an immovable bar)
What are the 3 questions to ask yourself to figure out a muscle action?
1. What joint does the muscle cross?
2. Where does the muscle cross the joint?
3. How does the muscle cross the joint (fiber orientation)?
A muscle with one line of pull in one cardinal plane will have how many actions?
1 (plus reverse)
A muscle with one line of pull in an oblique plane will have how many actions?
1 in the oblique plane, but 1+ in cardinal planes
Ex: Coracobrachilis has 1 action in an oblique plane, but also flexes in the sagittal plane and adducts in the frontal plane (2 actions)
Can a muscle choose which of its actions will occur?
No, unless there are multiple lines of pull - then the nervous system can send messages to contract only motor units that lie within specific lines of pull
If the muscles cross the joint anteriorly, they perform...
flexion (unless knee joint or below)
If the muscles cross the joint posteriorly, they perform...
extension (unless knee joint or below)
If the body part is axial, then muscles perform _____ to the same side
If the body part is appendicular, then muscles perform _____ to the same side
abduction (lateral side of joint) or adduction (medial side of joint)
If the body part is axial, then muscles perform _____ in the transverse plane
If the body part is appendicular, then muscles perform _____ in the transverse plane
Rotator muscles can be anterior or posterior, so trying to see the manner in which it wraps around a bone, try to visualize it from a ______ perspective
(ex: right splenius captius [posterior] and left sternocleidomastoid [anterior] both cause right rotation)
What is the off-axis attachment method
Another way to visualize if muscle causes rotation
If muscle attaches to bone on-axis, it has no possible rotation action
If it attaches on the bone off-axis (to either side of the long axis), it can create a rotation action
What is the long axis of a bone?
Straight line that runs from center of articular surface of bone at one end to the center of the articular surface of the bone at the other end
Important in determining rotation actions of muscles
How can the glute max cause feet to supinate/invert at the subtler tarsal joint if it doesn't cross that joint?
If person's feet are fixed to the ground, lateral rotation force of the glute max transfers down to the ankle
How is transferring muscle contraction to a joint a muscle doesn't cross not the same as "going along for the ride"?
Going along for the ride entails the body parts to maintain their relative position to each other; in transferring force, body parts change position even if the muscle doesn't cross that joint.
Can a muscle's action change?
Yes, if line of pull changes
Ex: pec major is an adductor, but when arm is abducted to >100 deg, the line of pull changes and it can abduct the arm (this helps when deltoid and supraspinatus become functionally weaker in higher range of abduction)