Ch 12: Skeletal Muscles Flashcards
The bone that moves is attached at the muscle _________?
Insertion
What happens when a muscle contracts?
It shortens
The muscle is attached to a bone that does not move at the muscle _______?
Origin
________ muscles decrease the angle between two bones at a joint.
Flexor
________ muscles increase the angle between two bones at a joint.
Extensor
The prime mover of my skeletal movement is called the?
Agonist
Flexors and extensors that work together are?
Antagonists
Skeletal muscles are surrounded by a fibrous _____.
Epimysium
Each fascicle of a muscle is surrounded by the?
Perimysium
Connective tissues called perimysium subdivides the muscle into _______.
Fascicles
Each fascicle is subdivided into muscle fibers surrounded by ______.
Endomysium
Muscle fibers have a plasma membrane called what?
Sarcolemma
________ are multinucleated and striated.
Muscle fibers
The light band of a skeletal muscle is known as the?
I band
The dark band of a skeletal muscle is known as the
A band
The site where a motor neuron stimulates a muscle fiber is known as?
Neuromuscular junction
The area of the muscle fiber sarcolemma where a motor neuron stimulates it is?
Motor end plate
Somatic motor neurons release the neurotransmitter _______ at the neuromuscular junction.
Acetylcholine
Each somatic motor neuron with all the muscle fibers it innervates is a?
Motor unit
Subunits of skeletal muscle cells that are composed of sarcomeres are called?
Myofibrils
The thick filament is also called the?
A band
____ contain only thin filaments.
I bands
_____ are the center of the A band with no thin filament overlap.
H bands
______ are found in the center of each I band
Z lines
_______ are found in the center of each A band and help hold down thick filaments.
M lines
What is the area from one Z line to the next?
Sarcomere
The protein that anchors in the thick filaments and allows elastic to coil is known as?
Titin
When a muscle contracts, sarcomeres shorten and _______ do not shorten.
A bands
When a muscle contracts, sarcomeres shorten and ______ shorten, but thin filaments do not.
I bands
When a muscle contracts, sarcomeres shorten and thin filaments side toward the ______?
H zone
Thick myofilaments are composed of the protein ______.
Myosin
Myosin contains binding sites for ____and______ .
ATP, actin
Which molecule blocks the myosin head from binding to actin in a relaxed muscle?
Tropomyosin
Sliding is produced by several cross bridges that form between ______ and _______.
Myosin, actin
Release of Pi upon binding cocks the myosin head, producing a _________ that pulls the thin filament toward the center.
Power stroke
After the power stroke, ____ is released and a new ATP binds.
ADP
_____ inhibits binding of myosin.
Troponin I
_____ binds to tropomyosin.
Troponin T
____ binds to calcium.
Troponin C
When muscle cells are stimulated, _____ is released inside the muscle fiber.
Ca2+
_______ is modified endoplasmic reticulum that stores Ca2+ when muscle is at rest. Most is stored in terminal cisternae.
Sarcoplasmic Reticulum (SR)
When a muscle fiber is stimulated, Ca2+ diffuses out of ______.
Calcium release channels
What are narrow membranous tunnels formed from the sarcolemma, open to the extra cellular environment, able to conduct act own potentials, and closely situated next to terminal cisternae?
Transverse Tubules
When stimulating a muscle fiber, _______ is released from the motor neuron, and the end plate potentials are produced.
Acetylcholine
When stimulating a fiber, action potentials are generated and voltage gated calcium channels in transverse tubules change shape and cause calcium channels in the SR to open causing ____ to be released and bind to the Troponin C.
Calcium
____ is done in vitro where one end of the muscle is fixed and the other is movable.
Study
When studying ________, electrical simulations are applied and contractions are recorded and displayed as currents.
Muscle behavior
What is it called when a muscle quickly contracts and relaxes after a single electrical shock of sufficient voltage?
Twitch
What is it called when a second shock is applied immediately after the first, and giving a piggyback look?
Summation
What is it called when increasing the frequency of electrical shocks decreases the relaxation time between twitches?
Incomplete tetanus
What is it called when at a certain frequency there will be no relaxation?
Complete tetanus
The inability of muscle cells to relax due to high frequency stimulation is termed?
Tetanus
As the voltage is increased, the number of muscle fibers used in vitro increases. This will reach a maximum value when all Muscle fibers are stimulated. If a fresh muscle is stimulated with several shocks at maximum voltage, each twitch will be progressively stronger causing a staircase effect. This is known as what?
Treppe
Muscle fibers shorten when the tension produced is just greater than the load is known as what?
Isotonic contractions
Muscles can’t shorten because the load is too great is known as what? (can be voluntary)
Isometric contractions
A muscle fiber shortens when force is greater than the load is known as what?
Concentric contractions
A muscle may actually lengthen, despite contraction, if the load is too great is known as what?
Eccentric contraction
_____ parts of the muscle and tendons must be pulled tight when muscles contract.
Noncontractile
______ are elastic, resist distension, and snap back to resting length. They also absorb some of the tension as muscles contract.
Tendons
__________ is determined by the number of fibers recruited to contract, frequency of stimulation, thickness of each muscle fiber ( thicker is stronger), and the initial length of the fiber at rest.
Muscle strength
_____ is maximal when sarcomeres are at normal resting length.
Tension
Increasing or decreasing sarcomeres length will _______ the muscle tension.
Decrease
Where do muscles get their energy when they are at rest or mild exercise?
Fatty acids
Where do muscles get their energy for moderate exercise?
Glycogen stores
Where do muscles get their energy from for heavy exercise?
Blood glucose
Determines whether a given exercise is light, moderate, or heavy for a given person Is called?
Maximal oxygen uptake
________ is determined by a person’s age, sex, size, and athletic training.
Maximal oxygen uptake
________ is another way to determine exercise intensity for a given person.
Lactate threshold
When a person exercises, _______ is withdrawn from reserves in hemoglobin and myoglobin.
Oxygen
Breathing rate continues to be ______ after exercise to repay this debt.
Elevated
The first 1 to 2 minutes of moderate to heavy exercise relies on ____ for ATP production.
Anaerobic respiration of glucose
What twitch caused slower contraction speed, can sustain contraction for long periods without fatigue, rich capillary supply, more mitochondria, more respiratory enzymes, and more myoglobin(slow,red fibers)?
Slow (type I)
What twitch has high oxidative capacity?
Slow (type I)
What twitch has faster contraction speed, fatigue fast, fewer capillaries, mitochondria, respiratory enzymes, and less myoglobin?
Fast (type II)
Type I skeletal muscle fibers have _________.
Numerous mitochondria
What has a fast-twitch but with high oxidative capacity?
Intermediate (type IIA)
Which of the following is NOT a contributing factor to skeletal muscle fatigue?
Increased intracellular K+
Adaptation to endurance training decrease in type II and _______ in type IIA muscle fibers.
Increase
Type II muscle fibrils become thicker due to increased amount of actin and myosin (more sarcomeres) is known as what?
Hypertrophy
Skeletal muscles have stem cells called ______ located near muscle fibers.
Satellite cells
_____ is a paracrine regulator that inhibits satellite cells.
Myostatin
Muscle decline is due to what?
Aging
_______ is influenced by sensory feedback from muscles and tendons, and stimulation or inhibition from higher motor neurons from the brain.
Lower motor neurons
What responds to tension that a muscle puts on a tendon?
Golgi tendon organs
What responds to muscle length?
Muscle spindle apparatus
The muscle spindle apparatus is associated with _______ ?
Intrafusal fibers
What are the two types of muscle cells?
Nuclear bag fibers, nuclear chain fibers
What are two types of sensory cells wrap around the fibers?
Primary ( annulospiral)
Secondary ( flower-spray)
Innervate extrafusal (contracting) muscle fibers is called?
Alpha
Innervate Intrafusal (stretch) muscle fibers is called?
Gamma
The simplest reflex that only involves a sensory neuron synapsing on a motor neuron in the spinal cord is called?
Monosynaptic
What can be stimulated by striking the patellar ligament in the “knee jerk reflex”?
Monosynaptic stretch reflex
In the knee jerk reflex, interneurons are also stimulated in the spinal cord to inhibit antagonistic muscles on that limb is known as?
Reciprocal innervation
More complex reflexes require control of muscles on the contralateral limb is known as? (when you step on a tack)
Double reciprocal innervation
What sends neurons through the pyramidal tracts?
Precentral gyrus
What receives information from muscle spindles and golgi tendon organs as well as other senses?
Cerebellum
What also acts to inhibit motor activity through the rubrospinal tract?
Basal nuclei
______ and ______ muscles are involuntary and are regulated by the autonomic nervous system. The contraction is due to the myosin/actin cross bridges stimulated by calcium.
Cardiac, smooth
_______ muscles are striated, have myosin and actin filaments that form sarcomeres, and contraction occurs by means of sliding thin filaments.
Cardiac
Unlike skeletal muscle fibers (cells), these fibers are short, branched, and connected via gap junctions called _______.
Intercalated discs
A ________ is a mass of cardiac muscle cells connected to each other via gap junctions.
Myocardium
Action potentials that occur at any cell in a myocardium can stimulate all the cells in the _____.
Myocardium
The _____ of the heart compose one myocardium, and the ______ of the heart compose another myocardium.
Atria, ventricles
Cardiac muscle can produce action potentials automatically that begin in a region called _______.
Pacemaker
____ is influenced by autonomic innervation and hormones.
Heart rate
______ is found in blood vessel walls, bronchioles, digestive organs, urinary and reproductive tracts.
Smooth muscle
What muscle has no sarcomeres, long actin filaments attached to dense bodies, some myosin filaments, and allows contraction even when greatly stretched?
Smooth muscle
In smooth muscle cells, _______ functions in a manner analogous to Troponin.
Calmodulin
Multiple gap junctions that make neighboring cells behave as a unit is known as?
Single-unit
What require individual nerve innervation (no pacemaker activity)?
Multi-unit
_______ is released along the length of an autonomic neuron from varicosities.
Neurotransmitter
The more movable end of a Muscle is called the ______.
Insertion
The principle muscle responsible for a particular movement is called the _______.
Agonist
Each muscle fiber is surrounded by a connective tissue layer called the _____.
Endomysium
The structural and functional unit of muscle is the _____.
Sarcomere
Which of the following do not change in size during muscle contraction?
A band
Which of the following uses calmodulin part of the ECC process?
Smooth muscle
Calmodulin take the place of _____ in muscle contraction.
Troponin
The primary foodstuff for mild exercising muscle is_____.
Fatty acids
An increase in muscle cell size is called?
Hypertrophy
Which of the following does not add to the red color of muscle?
Mitochondria
