Chapter 6- Muscular System
Endomysium covers ____.
A. sarcolemma
During skeletal muscle contraction, myosin heads attach to binding sites associated with ____.
A. sarcomere
A motor neuron and all of the skeletal muscle fibers it stimulates are termed a ____.
E. motor unit
Which of the following does not form part of the thin filaments of a muscle cell? A. tropomyosin B. actin C. troponin D. calcium-binding site E. myosin
E. myosin
Which section consists only of myosin filaments in a relaxed state?
H zone
The epimysium is represented by ____.
Label A
The myofilament composed of actin is indicated by ____.
Label C
The H zone, located within the A band, lacks thin filaments and is represented by ____.
Label D
Anaerobic glycolysis occurs without ____.
Oxygen
What does Label A represent?
The A Band
What does Label B Represent?
The I band
Why are calcium ions necessary for skeletal muscle contraction?
B. calcium triggers the binding of myosin to actin
What is the role of calcium in muscle contractions?
bind to the troponin complex, which leads to the exposure of the myosin-binding sites
The sarcoplasmic reticulum stores this chemical
calcium ions
Muscle tissue composed of branching cells and intercalated discs
cardiac muscle tissue
muscle tissue found only in heart
cardiac muscle tissue
The condition of skeletal muscle fatigue can be best explained by ____.
insufficient intracellular quantities of ATP due to excessive consumption
Muscle cells are stimulated by neurotransmitters released from the synaptic terminal of
motor neuron axons.
The plasma membrane of a skeletal muscle cell is called the ____. sarcolemma
sarcolemma
Which of the following can actually shorten during a muscle contraction?
sarcomere
Voluntary muscle tissue
skeletal muscle
Muscle tissue that is multinucleate
skeletal muscle tissue
Muscle tissue that maintains posture, body position, and stabilizes joints
skeletal muscle tissue
Muscle tissue that activates arrector pili muscles to stand hairs on end
smooth muscle tissue
Performs very slow, sometimes rhythmic, contractions
smooth muscle tissue
muscle tissue that is found lining internal body openings
smooth muscle tissue
Chemical that enters a muscle cell upon excitation
sodium ions
Creatine phosphate (CP) functions within the muscle cells by ____.
storing energy that will be transferred to ADP to resynthesize ATP as needed
Gap between the axon terminals and the plasma membrane of a neighboring muscle cell
synaptic cleft
A sustained muscle contraction due to a lack of relaxation between successive stimuli is called
tetanus
Neurotransmitters are released upon stimulation from a nerve impulse by the ____.
C. axon terminals of the motor neuron
A sarcomere is ____.
C. the contractile unit between two Z discs
Give a detailed account of the biochemcial events that occur from a motor neuron to a muscle cell in order to produce muscle contratction.
Correct Action potential travels the length of the axon to the axon terminal. The axon terminal becomes permeable to Ca. Ca signals the tranpsort vesicles to release ACh into the synaptic space. Acetylcholine is released, which diffuses through the synaptic cleft and attaches to receptors on the sarcolemma. The sarcolemma permeability to sodium ions increases briefly, causing sodium ions to rush into the muscle cell, which changes the electrical conditions of the resting sarcolemma. An action potential is initiated and sweeps over the entire sarcolemma. Calcium ions are released from storage areas inside the sarcoplasmic reticulum of the muscle cell. They attach to the myofilaments, which triggers the sliding of the myofilaments and causes a muscle cell contraction.
Specific neurotransmitter that stimulates skeletal muscle cells
acetylcholine
Which of these events must occur first to trigger the skeletal muscle to generate an action potential and contract?
acetylcholine (ACh) causes temporary permeability to sodium
Enzyme that breaks down acetylcholine (ACh)
acetylcholinesterase
Electrical current that travels the length of the muscle
action potential
