Muscles Lectures Flashcards
What causes the force of a contraction to be stronger than the one before it in wave summation?
The tautness of the elastic components and the partially contracted state of filaments
define tropomyosin
a component of thin filament; when skeletal muscle is relaxed, tropomyosin covers myosin-binding sites on actin molecules which prevents myosin from binding to actin
define isometric contractions
Muscle length does not change. Think of this as holding a position with a muscle.
What are the steps of contraction in smooth muscle
- Ca2+ enters the cell from the interstitial fluid or is released by the sarcoplasmic reticulum
- Ca2+ binds to calmodulin
- Calmodulin activates myosin light chain kinase
- MLCK uses ATP to add a phosphate group to a portion of the myosin head
- Once the phosphate group is attached the myosin head can attach to actin and contraction can occur
What are the two arrangements of smooth muscle?
single-unit and multi-unit
What is fascicular arrangement correlated with?
the amount of power a muscle can produce
the range of motion a muscle can produce
What are the two types of contractile proteins?
myosin and actin
Fibers can generate considerable ATP by aerobic cellular respiration, which gives them a moderately high resistance to fatigue are ———————–
fast oxidative glycolytic fibers
define H zone
narrow region in center of each A band that contains thick filaments and no thin filaments
what is the muscle version of cytoplasm
sarcoplasm
What partially accounts for the slow onset of contraction of smooth muscle?
The lack of transverse tubules makes it slower for Ca2+ to reach the filaments
Pair the connective tissue types (endomysium, perimysium, epimysium) with the type of muscle it goes with
Skeletal muscle: all three
cardiac muscle: no epimysium
smooth muscle: only endomysium
What is the location, function, appearance, and control of skeletal muscle?
location: skeletal
function: move bones
appearance: multinucleated and striated
control: voluntary
What is compartment syndrome?
pressure constricts structures within a compartment resulting in damage to blood vessels. If left untreated it can lead to nerve damage and muscle scar tissue and contracture
50% of muscle fibers in skeletal muscle are this type of fiber
slow oxidative
define z disc
narrow, plate shaped regions of dense material that separate one sarcomere from the next
What are the two muscles of mastication?
masseter and temporalis
The force of a muscle contraction depends on the ——— in a muscle prior to contraction
length of the sarcomeres
When does wave summation occur?
When a second action potential triggers muscle contraction before the first contraction has finished. It results in a stronger contraction.
Long cylindrical cell covered by endomysium and sarcolemma called
muscle cell
What makes stretching more effective?
increasing the temperature of the tissue
The basic functional units of myofibrils is
sarcomere
What is the location, function, appearance, and control of smooth muscle?
location: various organs
function: various including peristalsis
appearance: one nucleus and nonstriated
control: involuntary
Define fascia
a dense sheet or broad band of irregular connective tissue
The two types of cardiac enlargements are
physiological and pathological
Define epimysium
dense, irregular, connective tissue, encircling the entire muscle
What causes plantar fasciitis?
chronic irritation of the plantar aponeurosis at its origin on the calcaneus.
What is central fatigue?
A sudden feeling of tiredness and desire to cease activity caused by changes in the central nervous system. Thought to be protective.
What is hypertrophy caused by?
increased synthesis of thick and thin filaments
A nerve impulse (nerve action potential) elicits a muscle action potential in the following three ways
release acetylcholine
activation of acetylcholine receptors
production of muscle action potential
What can smooth muscle sustain?
long-term tone which maintains a steady pressure on the contents within the organ or vessel (blood pressure and arterioles)
Define myosin
Makes up the thick filament in the sarcomere. Consists of a tail and two myosin heads, which bind to myosin-binding sites on actin.
What are the structural proteins?
titin, alpha actinin, myomesin, nebulin, and dystrophin
What is tone?
A small amount of tension in the muscle even at rest. Established by alternating, involuntary activation of small groups of motor units in a muscle.
What do most running injuries involve?
the knee
A single somatic motor neuron makes contact with an average of 150 skeletal muscle fibers, and all of the muscle fibers in one motor unit contract in a term called
unison
What is the lever (bone) acted on by?
resistance and effort
Give a brief explanation of the creatine phosphate cycle
When contraction begins and the ADP level starts to rise, creatine kinase catalyzes the transfer of a high-energy phosphate group from creatine phosphate back to ADP. This direct phosphorylation reaction quickly generates new ATP molecules. Since the formation of ATP from creatine phosphate occurs very rapidly, creatine phosphate is the first source of energy when muscle contraction begins.
More:
While muscle fibers are relaxed, they produce more ATP than they need for resting metabolism. Most of the excess ATP is used to synthesize creatine phosphate (KRĒ-a-tēn), an energy-rich molecule that is found in muscle fibers (Figure 10.11a). The enzyme creatine kinase (CK) catalyzes the transfer of one of the high-energy phosphate groups from ATP to creatine, forming creatine phosphate and ADP. Creatine is a small, amino acid–like molecule that is synthesized in the liver, kidneys, and pancreas and then transported to muscle fibers. Creatine phosphate is three to six times more plentiful than ATP in the sarcoplasm of a relaxed muscle fiber. When contraction begins and the ADP level starts to rise, CK catalyzes the transfer of a high-energy phosphate group from creatine phosphate back to ADP. This direct phosphorylation reaction quickly generates new ATP molecules. Since the formation of ATP from creatine phosphate occurs very rapidly, creatine phosphate is the first source of energy when muscle contraction begins. The other energy-generating mechanisms in a muscle fiber (the pathways of anaerobic glycolysis and aerobic respiration) take a longer period of time to produce ATP compared to creatine phosphate. Together, stores of creatine phosphate and ATP provide enough energy for muscles to contract maximally for about 15 seconds.
What are anabolic steroids?
synthetic variations of testosterone that increase muscle size and strength
define M line
region in the center of the H zone that contains proteins that hold thick filaments together at center of sarcomere.
What are the two sources of oxygen for muscle tissue?
- oxygen that diffuses into muscle fibers from the blood
2. oxygen released by myoglobin within muscle fibers.
what are three factors that affect maximum tension?
amount of stretch before contraction and nutrient and oxygen availabilty
A narrow ——————- zone in the center of each A band contains thick but not thin filaments.
H
The ability of muscular tissue to contract forcefully when stimulated by an action potential is called
contractility
what is the latent period?
the action potential sweeps over the sarcolemma, and the calcium ions are released from the sarcoplasmic reticulum.
What are the unique structural features of smooth muscle?
no sarcomeres intermediate filaments no striations no transverse tubules caveolae cavus for extracellular Ca2+ dense bodies twists as it contracts
define nebulin
wraps around entire length of each thin filament, helps anchor thin filaments to Z discs and regulates length of thin filaments during development
An increase in the number of muscle fibers called
hyperplasia
define endomysium
Made of RETICULAR connective tissue, separates individual muscle fibers from one another.
What are the four phases of twitch contraction?
latent, contraction, relaxation, and refractory
What is unfused tetanus?
A skeletal fiber is stimulated at a rate of 20-30 times per second and can only partially relax between stimuli.
The functions of the fascia are
allows free movement of muscles
fills spaces between muscles
What will happen if two stimuli are applied immediately after the other?
the muscle will only respond to the first one
what is the primary function of slow oxidative fibers?
maintaining posture and aerobic endurance activities
how can running injuries be treated?
price, nsaids, steroid injections, and rehab
what is the primary function of fast glycolytic fibers?
rapid, intense movements of short duration
What influences the proportions of types of skeletal muscle fibers in a muscle?
- action of muscle
- person’s exercise routine
- genetics
There are small pouch-like invaginations of the plasma membrane in the smooth muscles called ———————————————– that contain extracellular calcium
caveolae
The neurons that stimulate a skeletal muscle to contract called
somatic motor neurons
Muscular tissue contributes to homeostasis by
body movements
moving substances
producing heat
define actin
The main component of thin filaments. Has a myosin-binding site where myosin head binds during muscle contraction
define titin
structural protein that connects Z discs to M line of sarcomere. Stabilizes thick filament position, and creates the elasticity and extensibility of myofibrils.
List the organizations of tissues in muscles starting from the largest and going to the smallest
skeletal muscle->fascicle->muscle fiber (cell)->myofibril->sarcomere->filaments
Supporting protein in the middle of the sarcomere forming the ——- line
M line
What is the total force/tension a single muscle fiber can produce dependent on?
the rate at which nerve impulses arrive at the NMJ
Explain the contraction cycle
Before step 1
calcium binds to troponin moving tropomyosin off the binding sites
What are the three muscle types in a muscle group and what are their definitions
- agonist/prime mover: a muscle that contracts to cause an action
- antagonist: stretches and yields to the prime mover and does the opposite action
- synergists: contract and stabilize intermediate joints when a prime mover crosses more than one joint. supports the movement of the prime mover
Describe how the muscle contraction spreads from the sarcomere to the bones
sarcomeres contract, which pulls on dystrophin which is connected to the sarcolemma, which causes the sarcolemma to move, which then causes the entire cell to contract, the more cells that contract the stronger contraction is in the muscle. That contraction of the muscle pulls on tendons which pull on bones and cause movement.
define concentric isotonic contraction
muscle shortening to produce movement
What is complete tetanus?
A skeletal muscle fiber is stimulated at a rate of 80-100 times per second, and the muscle does not relax at all. Individual twitches cannot be detected at all.
what is the contraction period?
Ca2+ binds to troponin, myosin-binding sites on actin are exposed, and cross bridges form
A narrow region in the center of A band that contains thick filaments only is
H zone
When a muscle contracts, what happens in relation to the insertion and origin positions?
the insertion point moves closer to the origin point
define perimysium
dense, irregular connective tissue that surrounds groups of 10-100 or more muscle fibers, separating them into bundles called fascicles.
Light area of sarcomere that contains remainder of thin filaments but no thick filaments is called
I band
define insertion
the attachment to the moveable bone
In a class 1 lever, what is in the middle? What is an example?
the fulcrum. the head on top of the vertebral column. Has mechanical advantages and disadvantages
Between 30–50 years of age, about 10% of our muscle tissue is replaced by
adipose tissue and fibrous connective tissue
What are the 9 steps of muscle contraction starting with the action potential
- a nerve action potential in a somatic motor neuron triggers the release of acetylcholine(ACh)
- ACh binds to receptors in the motor end plate triggering a muscle action potential
- Acetylcholinesterase destroys the ACh so another muscle action potential does not arise unless more ACh is released from the somatic motor neuron
- a muscle action potential traveling along a transverse tubule triggers a change in voltage-gated Ca2+ channels on the sarcoplasmic reticulum and the Ca2+ release channels to open, allowing the release of calcium ions into the sarcoplasm
- Ca2+ binds to troponin on the thin filament exposing myosin binding sites on the actin
- Myosin heads bind to actin, undergo power strokes, and release, thin filaments are pulled toward center of sarcomere.
- Ca2+ release channels close and CA2+-ATPase pumps use ATP to pump CA2+back into reticulum and restore low level of Ca2+ in sarcoplasm.
- tropomyosin slides back into place and covers myosin binding sites
- muscle releases
What are the four properties of muscular tissue?
- electrical excitability
- contractility
- extensibility
- elasticity
what is elasticity?
is the ability of muscular tissue to return to its original length and shape after contraction or extension
The darker middle part of the sarcomere is the
_____ band, which extends the entire length of the
____filaments.
A band
thick filaments
The contractile organelles of skeletal muscle. extend the entire length of a muscle fiber is called
myofibrils
What are the regulatory proteins?
tropomyosin
troponin
What effect does Ca2+ have on actin?
Ca2+ attaches to troponin which changes its shape, moving the tropomyosin and allowing myosin access to the myosin-binding sites.
In a class 2 lever, what is in the middle? What is an example?
The lever is in the middle. Standing on toes. They always produce a mechanical advantage. produces the most force but sacrifices speed and range of motion
Where are slow oxidative fibers abundant?
postural muscles such as those in the neck
where are fast glycolytic fibers abundant?
extraocular muscles and upper limbs
Where is Ca2+ stored?
the sarcoplasmic reticulum
What limits a relaxed muscle’s ability to lengthen?
connective tissue such as fasciae
What are the 7 ways that muscles are named?
location, size, number of origins, appearance, direction of fibers, origin and insertion, and muscle action.
Fibers contain large amounts of glycogen and generate ATP mainly by glycolysis contract strongly and quickly are
fast gylcolytic
how do skeletal muscles produce movement?
exerting force on tendons which pull bones
in a class 3 lever, what is in the middle? what is an example?
The effort. the arm and the elbow joint. Always a mechanical disadvantage favors speed and range of motion.
What are the four functions of fascia?
- lines the body wall and limbs
- supports and surrounds muscles and other organs of the body
- allows free movement of muscles
- fills spaces between muscles
The intercalated disc in the cardiac muscle contains two structures
desmosomes and gap junctions
Cardiac muscle cells contraction remains for a long time because it contains ————
large number of mitochondria
What is the location, function, appearance, and control of cardiac muscle?
location: heart
function: pump blood
appearance: one nucleus, striated, and intercalated
control: involuntary
define A band
dark, middle part of the sarcomere that extends the entire length of the thick filaments and includes those parts of thin filaments that overlap thick filaments.
What do intercalated discs contain?
desmosomes and gap junctions that allow muscle action potentials to spread from one muscle fiber to another
define eccentric contractions
muscle lengthens to produce movement
What does a motor unit consist of?
a somatic motor neuron and the muscle fibers it innervates
In comparison to skeletal and cardiac muscle, is smooth muscle more or less stretchable?
more stretchable
A dark band in the middle of sarcomere that entire length of thick filaments called
A band
What are the four steps at the neuromuscular junction that produce a muscle action potential
- Voltage-gated calcium channels in a neuron’s synaptic end bulb open, resulting in an influx of calcium. This causes exocytosis of a acetylcholine into the synaptic cleft
- acetylcholine binds to ligand-gated Na+ channels on the motor end plate, which causes an influx of Na+ into the muscle
- This depolarizes the muscle and results in Ca2+ release from the sarcoplasmic reticulum
- acetylcholine gets broken down by acetylcholinesterase
In comparison to skeletal and cardiac muscle, what are smooth muscle contractions like?
slower and last longer
define isotonic and what are the two types?
tension is constant while muscle length changes
concentric and eccentric
What does the strength of a muscle contraction rely on?
how many motor units are activated
what is extensibility?
is the ability of muscular tissue to stretch, within limits, without being damaged
The two major factors are thought to contribute in fatigue are
inadequate release of calcium ions from SR and depletion of creatine phosphate
A dense sheet or broadband of irregular connective tissue that lines the body wall and limbs and supports and surrounds muscles and other organs of the body is called
fascia
define alpha actinin
structural protein of Z discs that attaches to actin molecules of thin filaments and to titin molecules
what is the muscle version of the cell membrane?
sarcolemma
Inside the SR, molecules of a calcium-binding protein, appropriately called ——bind to the Ca2, enabling even more Ca2 to be sequestered or stored within the SR.
calsequestrin
Creatine is a small, amino acid–like molecule that is synthesized in the
liver, kidneys, pancreas
The ability of muscular tissue to return to its original length and shape after contraction or extension is called
elasticity
what is contractility?
the ability of muscular tissue to contract forcefully when stimulated by an action potential
What are the seven types of fascicle arrangments?
parallel, fusiform, circular, triangular, unipennate, bipennate, multipennate
Between 30-50 10% of our muscle tissue is replaced by what?
fibrous connective tissue and adipose
what is the primary function of fast oxidative-glycolytic fibers
walking or sprinting
For oxygen consumption after exercise; The extra oxygen is used to “pay back” or restore metabolic conditions to the resting level in three ways
convert lactic acid back into glycogen
resynthesize creatine phosphate and ATP
replace the oxygen removed from myoglobin.
what is the phrase for the number of impulses per second
frequency of stimulation
What is muscle fatigue?
the inability to maintain force of contraction after prolonged activity
The ability of muscular tissue to stretch, within limits, without being damaged is called
extensibility
what is the refractory period?
a period of loss of excitability
How many pairs of eye muscles are there?
3
superior and inferior recti
lateral and medial recti
superior and inferior obliques
Give a brief explanation of anaerobic glycolysis
2nd form of energy. Glucose from the bloodstream or glycogen is broken down via glycolysis to produce 2 net ATP and 2 pyruvic acids. Pyruvic acid is converted to lactic acid. Lactic acid goes out into the blood, and the liver converts it back to glucose. Can fuel 2 minutes of muscle activity
Three reasons for extra oxygen intake after exercise (recovery oxygen uptake)
- elevated body temp after exercise increases the rate of chemical reactions in the body which increases the need for ATP so more oxygen is needed
- heart and lungs are still working harder than at rest and are using more ATP
- tissue repair processes are occurring at an increased pace
Smooth muscle fibers connect to one another by
gap junctions
What is twitch contraction?
the brief contraction of all muscle fibers in a motor unit in response to a single action potential
What are the three types of muscular tissue?
skeletal, cardiac, and smooth
What are the consequences of aging on muscles?
- muscle strength and flexibility decreases
- reflexes slow
- slow oxidative fiber numbers increase
Q. In a neuromuscular junction, the effect of acetylcholine (ACh) binding to receptors on the motor end plate lasts only briefly due to
a) rapid uptake of the ACh into the myofiber.
b) endocytosis of the ACh receptor into the myofiber.
c) rapid destruction of ACh in the synaptic cleft by acetylcholinesterase.
d) rapid destruction of ACh in the synaptic cleft by monoamine oxidase.
e) diffusion of the ACh out of the synaptic cleft.
c)rapid destruction of ACh in the synaptic cleft by acetylcholinesterase.
What is the optimal sarcomere length?
2-2.4 micrometers
Which intercostals are associated with forced exhalation?
internal intercostals
What are the four functions of muscular tissue?
- producing body movements
- stabilizing body positions
- storing and mobilizing substances within the body
- generating heat
what is the stress-relaxation response?
In SINGLE UNIT smooth muscle tissue it allows the muscle to undergo great changes in length while retaining the ability to contract effectively.
Thousands of tiny invaginations of the sarcolemma called ————- tunnel in from the surface toward the center of each muscle fiber.
transverse tubule
What are the four causes of muscle fatigue?
- Inadequate release of Ca2+ from the sarcoplasmic reticulum
- Depletion of creatine phosphate, oxygen, and nutrients
- Build-up of lactic acid and ADP
- Insufficient release of ACh at NMJ
Which motor units are recruited first?
weakest motor units
What are the things that smooth muscle contract and relax in response to?
autonomic nervous system
stretching
hormones like epinephrine
local factors like changes in pH, O2, CO2, temp, and ion concentrations
What are the three types of skeletal muscle fibers?
slow oxidative, fast glycolytic, and fast oxidative-glycolytic
What does the oxygen taken in during heavy breathing after exercise go to?
replenishing creatine phosphate stores, converting lactate into pyruvate, and refilling O2 in myoglobin
When facial muscles move, what do they move?
the skin rather than a joint
Why is ATP hydrolyzed into ADP and a P?
to release the energy needed for the myosin to create the cross bridge
define myomesin
forms M line of sarcomere, binds to titin molecules and connects adjacent thick filaments to one another.
what is the relaxation period?
Ca2+ is transported back into the SR, myosin-binding sites are recovered, myosin detaches from actin, and tension in the muscle fiber decreses
what is the order that the types of skeletal muscle fibers are recruited from the weakest
slow oxidative -> fast oxidative glycolytic -> fast glycolytic
define I band
lighter, less dense area of sarcomere that contains remainder of the thin filaments but no thick filaments. A Z disc passes through the center of each I band
What are the three ways muscles derive the ATP needed for the contraction cycle?
- creatine phosphate
- anaerobic glycolysis
- cellular respiration
At the neuromuscular junction, _______must enter the synaptic end bulb to stimulate the release of ____________, which binds to ligand gates so ________can enter the muscle fiber.
a) calcium ions; ACh, sodium ions
b) Sodium ions, calcium ions, Ach
c) ACh, calcium ions, sodium ions
d) sodium ions, ACh, calcium ions
e) calcium ions, sodium ions, ACh
a)calcium ions; ACh, sodium ions
Define origin
the attachment to the stationary bones
Threadlike contractile elements within the sarcoplasm of muscle fibers that extend the entire length of the fiber, composed of filaments, are
myofibrils
Give a brief explanation of cellular(aerobic) respiration
If sufficient oxygen is present, the pyruvic acid created in glycolysis enters the mitochondria and undergoes cellular respiration through the Kreb’s cycle and electron transport chain. ATP, CO2, H2O, and heat are produced. 30-32 ATP is produced.
Suspended in the cytosol within each synaptic end bulb are hundreds of membrane-enclosed sacs called
neurotransmitters
The brief contraction of all the muscle fibers in a motor unit in response to a single action potential in its motor neuron is called:
twitch contraction
The elastic components of muscles include
titin
the connective tissue around muscle fibers
tendons that attach muscle to bone
What do cardiac muscles have more of than other muscle types?
mitochondria
What are the 5 intrinsic hand movements?
flexion, extension, abduction, adduction, and opposition
Where is multiunit smooth muscle tissue found?
large arteries, airways to the lungs, arrector pili muscles, muscles of the iris, and ciliary body that adjusts the focus of the lens in the eye
where are fast oxidative-glycolytic fibers abundant?
lower limb muscles
Can mature skeletal muscle fibers undergo mitosis?
no
define dystrophin
links thin filaments of sarcomere to integral membrane proteins in sarcolemma, which are in turn attached to proteins in connective tissue matrix that surrounds muscle fibers. Thought to help reinforce sarcolemma and help transmit tension generated by sarcomeres to tendons.
define troponin
a component of thin filament, when calcium ions bind to troponin it changes shape which moves tropomyosin from myosin-binding sites on actin molecules which allows muscle contraction because the myosin can bind to actin
what is electrical excitability?
ability to respond to certain stimuli by producing electrical signals called action potentials (impulses)
What are pericytes?
stem cells found in association with capillaries and veins that allow smooth muscle to create new muscle fibers.
Properties of Muscular Tissue are
electrical excitability
extensibility
contractility
elasticity
What are the three types of connective tissue important to muscles?
- epimysium
- perimysium
- endomysium
When the connective tissue elements extend as a broad, flat sheet, it is called an
aponeurosis
