A&P Lecture, exam 3
Aerobic metabolism normally provides ________ percent of the ATP demands of a resting muscle cell.
95%
motor unit function
A Motor Neuron branches to form axon, axon goes to the muscle fibers and attaches with the axon terminal.
motor unit
A motor neuron and all of the muscle fibers it innervates
Define motor unit.
A motor unit is a motor neuron and all the muscle fibers that it controls
The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?
A myosin head bound to actin
Define the term synergist as it relates to muscle action.
A synergist is a muscle that helps the agonist perform its actions more efficiently.
After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?
ATP binds to the myosin head
Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine?
Acetylcholine is degraded by acetylcholinesterase.
The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction?
Acetylcholine is released by axon terminals of the motor neuron.
Alfredo believes he is only exercising one muscle (the biceps brachii) when he performs the elbow flexion exercises Jessica told him about. What other muscle is a synergist that also participates in these exercises?
Brachialis
Think about the insertions of the muscles involved in elbow flexion and the positioning of the bones in the exercises described. Which of the elbow flexors does doing the "hammer curl" exercise probably emphasize?
Brachioradialis
How do calcium ions (Ca2+) in the sarcomere affect the contraction cycle?
By binding to troponin, Ca2+ causes it to shift position and move tropomyosin, exposing the binding sites on actin.
Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber?
Calcium ions are stored in the sarcoplasmic reticulum.
What event initiates the contraction cycle?
Calcium ions arrive within the zone of overlap.
What specific event triggers the uncovering of the myosin binding site on actin?
Calcium ions bind to troponin and change its shape.
When does cross bridge cycling end?
Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.
What structure is the functional unit of contraction in a skeletal muscle fiber?
The sarcomere
Muscle A abducts the humerus and muscle B adducts the humerus. What is the relationship between the two muscles.
The two muscles are antagonists to each other.
Tetanus is most likely to result from which condition?
a deep puncture wound, such as that from a nail
creatine phosphate
a high energy compound that can be broken down for energy and used to regenerate ATP
Polio
a viral disease that attacks motor neurons in the spinal cord and brain
The tensor fascia latae is involved in hip __________.
abduction
Excitability
ability to receive and respond to stimuli
elasticity of muscle tissue
ability to return to original shape after being stretched
Myosin molecules form cross-bridges when they attach to __________.
actin
Which of the following proteins contains the active site involved in cross-bridge formation?
actin
Which phase of the contraction cycle directly requires that calcium ions bind to troponin?
active-site exposure
Damage to the pectoralis major would interfere with a person's ability to
adduct the humerus.
Which process can, by itself, power the greatest number of twitches, based on the energy sources available in a typical muscle fiber?
aerobic metabolism of glycogen
The smallest of the posterior extensors of the elbow joint is the __________.
anconeus
Motor units are activated on a rotating basis to reduce fatigue. What is this mechanism called?
asynchronous motor unit summation
The muscle that generates the most power during elbow flexion is the __________.
brachialis
If you were contracting and relaxing your masseter, what would you probably be doing?
chewing or eating
The pectoralis major muscle can be divided into groups of fibers superior, or __________, and inferior, or __________.
clavicular; sternocostal
The names of the muscles can indicate all of the following except
collagen content of the muscle.
troponin
consists of 3 globular subunits; one binds to tropomyosin, one binds to the G-actin and a third subunit has a receptor that binds two calcium ions
Calcium ions are bound to troponin during which of the following steps.
contraction phase
The brachialis muscle is located __________ to the biceps brachii muscle.
deep
What is the type of chemical reaction used to rebuild ADP into ATP?
dehydration synthesis
Name the muscle that abducts the arm.
deltoid
ATP binding leads to which of the following actions?
detaching and resetting cross-bridges
Muscles of the shoulder can be divided into groups based on __________.
distribution and functional relationships
Individual muscle cells are surrounded by what connective tissue?
endomysium
Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________.
extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber
The extensor muscle that branches to form four tendons on the back of the hand is the __________.
extensor digitorum
Superficial muscles that position or stabilize an organ are called
extrinsic.
The brachioradialis is a strong forearm __________.
flexor
Which superficial flexor muscle of the forearm is the most lateral?
flexor carpi radialis
Which muscle is a superficial anterior flexor muscle?
flexor digitorum superficialis
Which muscle of the wrist and fingers is a deep anterior flexor?
flexor pollicis longus
The prime mover of hip extension is the __________.
gluteus maximus
Which muscle of the gluteal group acts in extension and lateral rotation at the hip?
gluteus maximus muscle
Which of the following processes produces molecules of ATP and has two pyruvic acid molecules as end products?
glycolysis
Mature skeletal muscle fibers:
individually contain hundreds of nuclei just internal to the plasma membrane.
The origin of the long head of the triceps brachii is on the __________.
infraglenoid tubercle of the scapula
The tensor fasciae latae stabilizes the hip joint and the __________ joint.
knee
Which of these would NOT lead to increased oxygen consumption?
lactic acidosis
Myofibrils are __________.
made of a series of sarcomeres
The Na+/K+ ion pump is responsible for
maintaining the sodium/potassium concentration gradients constant.
The key actions of the pectoralis major muscle are __________.
medial rotation and adduction
When acetylcholine binds to receptors at the motor end plate, the end plate membrane becomes
more permeable to sodium ions.
Neurons and ________ have electrically excitable membranes that propagate action potentials.
muscle cells
Interactions between actin and myosin filaments of the sarcomere are responsible for
muscle contraction
Contractibility
muscle fibers that are stimulated by nerves contract, or become short and thick, which causes movement
Synergist
muscle that helps larger agonist work efficiently -May provide additional pull or stabilize origin
Antagonist
muscle whose action opposes a particular agonist
Agonist or prime mover
muscle whose contraction is mostly responsible for producing the movement
Determine the correct structural hierarchy of skeletal muscles from microscopic to gross levels.
myofibril - fiber - fascicle - muscle
Which of the following is involved in the power stroke?
myosin
Name the proteins that make up a thick filament.
myosin and titin
Communication between axons and muscle fibers occurs at specialized synapses called
neuromuscular junctions.
People who are engaged in repetitive hand movements such as typing or playing the piano may suffer wrist pain, especially during palmar flexion. All of the following are true concerning this condition except that it
never causes muscle weakness.
Rigor mortis
occurs as the sarcoplasmic reticulum deteriorates, releasing calcium ions
The end of a muscle that remains stationary when the muscle contracts is called the
origin
inferior oblique
origin: maxillary bone at anterior portion of orbit insertion: inferior, lateral surface of eyeball action: eye rolls, looks superiorly and laterally
Occipitofrontalis (occipital belly)
origin: occipital and temporal bone insertion: epicranial aponeurosis action: tenses and retracts scalp
medial rectus
origin: sphenoid around optic canal insertion: medial surface of eyeball action: eye looks medially
Sternocleidomastoid
origin: sternum and clavicle insertion: mastoid process action: flexes neck
The palmaris longus inserts on the __________.
palmar aponeurosis
Sarcolemma
plasma membrane of a muscle cell
neuromuscular junction
point of contact between a motor neuron and a skeletal muscle cell
The muscles that extend the forearm are located __________.
posteriorly
Which of the following describes the action of the serratus anterior?
protracts the shoulder, abducts and medially rotates the scapula
All fibers of the triceps brachii are innervated by the __________.
radial nerve
The two heads of the biceps brachii combine to insert on the __________.
radial tuberosity
The interosseous membrane is located between the __________.
radius and ulna
The smooth but steady increase in muscular tension that is produced by increasing the number of active motor units is called __________.
recruitment
All of the following provides flexion of the knee except
rectus femoris.
The muscle that adducts and rotates the scapula downward is the
rhomboid
Muscles of the rotator cuff include all of the following except the
rhomboid.
The plasma membrane of skeletal muscle is called the
sarcolemma.
The repeating contractile unit of a skeletal muscle fiber is the
sarcomere.
Z lines define the edges of which of the following?
sarcomeres
The anterior muscles of the thigh that originate on the os coxae are __________.
sartorius; rectus femoris
Which of the following muscles are found in the cervical region and act in elevating the ribs?
scalenes
excitation-contraction coupling
sequence of events from motor neuron signaling to a skeletal muscle fiber to contraction of the fiber's sarcomeres
Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber
shortens
Which muscle types are voluntary, and which are involuntary?
skeletal muscle is voluntary, and cardiac and smooth muscles are involuntary
Tropomyosin
strands of tropomyosin cover the sites of G-actin and prevent actin-myosin interaction
The endomysium __________.
surrounds the individual muscle fiber
A muscle that assists the muscle that is primarily responsible for a given action is a(n)
synergist
Fixators
synergists that assist by preventing movement at another joint
Muscles that laterally rotate the thigh include all of the following except the
tensor fasciae latae.
Within a resting skeletal muscle fiber, where is the greatest concentration of Ca2+?
terminal cisternae of the sarcoplasmic reticulum
oxygen debt
the amount of oxygen required after physical exercise to convert accumulated lactic acid to glucose
Which of the following groups of muscles are not muscles of the shoulder?
the anterior flexor muscles
What has the greatest concentration of calcium?
the concentration of calcium ion in the sarcoplasmic reticulum of a resting muscle
In a first-class lever __________.
the fulcrum lies between the applied force and the load
Acetylcholine binds to its receptor in the sarcolemma and triggers __________.
the opening of ligand-gated cation channels
Which joint is considered the most flexible joint in the body?
the shoulder joint
Explain the function of sodium-potassium ion pumps.
the sodium-potassium ion pump maintains the resting membrane potential of a cell by exporting three sodium ions out in exchange for two potassium ions entering the cell
muscle fibers
they are sheathed in a delicate endomysium
Myosin molecules form what part of the sarcomere?
thick filament
actin
thin filaments
A muscle that dorsiflexes the foot is the
tibialis anterior
The prime mover of elbow extension is the __________.
triceps brachii
The muscle that extends the arm while doing push-ups is the
triceps brachii.
When the sarcomere is at rest, what is covering the active sites on actin?
tropomyosin
At rest, active sites on the actin are blocked by
tropomyosin molecules
When calcium is released inside a muscle cell, what does it bind to?
troponin
Which thin filament-associated protein binds two calcium ions?
troponin
Which of the following muscles of the thigh is located most anteriorly?
vastus medialis muscle
muscle metabolism
when muscle are in use, lots of ATP is needed. This ATP comes from three sources: Creatine phosophate, Anaerobic cellular respiration, and Aerobic cellular resperation.
When does a muscle contraction begin?
when stored calcium ions are released into the sarcoplasm through gated calcium channels
Origin
where fixed end of a skeletal muscle attaches -Most are bones -Some are connective tissue sheaths or bands -Typically proximal to insertion in anatomical position
Insertion
where the movable end of a skeletal muscle attaches
Which type of muscle fiber has a large quantity of glycogen and mainly uses glycolysis to synthesize ATP?
white fast twitch fibers
Which exercise below would be best at exercising the palmaris longus?
Holding a dumbbell in a supinated grip with arm horizontal and flexing the wrist
How would a torn calcaneal tendon affect movement at the ankle?
It would make extension difficult.
Occipitofrontalis (frontal belly)
Origin: Epicranial aponeurosis Insertion: Skin of eyebrow and bridge of nose Action: Raises eyebrows, wrinkles forehead
Orbicularis oris
Origin: Maxilla and mandible Insertion: Lips Action: Compresses, purses lips
Orbicularis oculi
Origin: Medial margin of orbit Insertion: Skin around eyelids Action: Closes eye
Inferior rectus
Origin: Sphenoid around optic canal Insertion: Inferior, medial surface of eyeball Action: Eye looks inferiorly
Buccinator
Origin: aveolar processes of the maxillae and mandible Insertion: corner of the mouth Action: compress cheeks
Platysma
Origin: fascia of chest Insertion: lower mandible Action: draws mouth downward
Lateral rectus
Origin: sphenoid around optic canal Insertion: lateral surface of eyeball Action: eye looks laterally
Superior rectus
Origin: sphenoid around optic canal Insertion: superior surface of eyeball Action: eye looks superiorly
superior oblique
Origin: sphenoid around optic canal Insertion: superior, lateral surface of eyeball Action: eye rolls, looks inferiorly and laterally
temporalis
Origin: temporal bone Insertion: mandible Action: closes jaw
Masseter
Origin: zygomatic arch Insertion: mandible Action: elevates mandible
Zygomaticus major
Origin: zygomatic bone Insertion: angle of mouth Action: retracts and elevates corner of mouth
The "rest and recovery" period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT __________.
Pyruvic acid is converted back to lactic acid.
Calcium entry into the axon terminal triggers which of the following events?
Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.
myosin
The contractile protein that makes up the thick filaments of muscle fibers
How does the myosin head obtain the energy required for activation?
The energy comes from the hydrolysis of ATP.
Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?
The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.
Which of the following is correct regarding muscle fatigue and recovery?
During the recovery period, lactate can be recycled back to pyruvate.
Which of the following processes produces 36 ATP?
Krebs cycle and oxidative phosphorylation
Myofibrils
Microscopic protein filaments that make up muscle cells.
What happens to the lactate produced by skeletal muscle during peak activity?
Most of the lactate diffuses into the bloodstream and enters the liver where it is converted to pyruvate.
Which of the following statements is true concerning motor units?
Movement of the eyeball requires fewer muscle fibers with less tension being produced.
Define muscle hypertrophy and muscle atrophy
Muscle hypertrophy is an increase in the size of the muscle cells and muscle atrophy is a decrease in the size of the muscle cells.
Name the three types of muscle tissue, identify where they are found, and list their functions.
Skeletal muscle is directly or indirectly attached to bones and enables movement of the body. Cardiac muscle forms the heart and propels blood. Smooth muscle is found throughout the body and moves substances through hollow tubes, such as in the digestive tract and regulates the diameter of blood vessels.
Which of the following events must happen for the movement of the thin filament toward the M line (the center of the sarcomere)?
The myosin head binds to the active site on actin and pivots toward the M line.
What happens immediately after the myosin head binds to the active site on actin?
The myosin head pivots, moving the actin strand.
The interaction between the contractile proteins repeats over and over during a single contraction of a muscle cell. Which of the following choices allows the repeated separation and reactivation of the myosin head?
The presence of ATP
Explain why the propagation of action potentials along electrically excitable membranes occurs in only one direction
The refractory period prevents it from propagating back in the direction from which it began.
