Bone Anatomy
What is the primary function of tendons?
Attach muscle to bone
Calcitonin is secreted by the thyroid gland when blood calcium levels are too high. It lowers blood calcium concentration by:
Inhibiting osteoclasts and stimulating osteoblasts
What is the specialized plasma membrane of a muscle fiber called?
Sarcolemma
During muscle shortening, do the thick and thin filaments shorten in length?
No, they do not change length just overlap
Small motor units like those in the eye and hand muscles typically have three to six muscle fibers per neuron, which allows for:
A fine degree of motor control
Which type of bone is thin, curved, and primarily serves to protect soft organs?
Flat bones
Parathyroid hormone (PTH) is released when blood calcium is...
Low
The alternating light and dark transverse bands that give skeletal muscle its appearance are called:
Striations
The process where the inside of the plasma membrane becomes positive due to Na+ flowing into the cell is called:
Depolarization
The resting membrane potential (RMP) in a muscle fiber is approximately −90mV. This negative charge on the inside of the sarcolemma is maintained primarily by:
Na + and –K + pump and presence of intracellular anions
The dense outer shell of bone is referred to as:
Compact bone
Which hormone is the most active form of Vitamin D and primarily raises blood calcium levels by increasing calcium absorption by the small intestine?
Calcitriol
The specialized smooth ER that forms a network around each myofibril and acts as a calcium reservoir is the:
Sarcoplasmic reticulum
What is the fundamental mechanism of muscle contraction according to the sliding filament theory?
Thick and thin filaments slide past each other, pulling the Z discs closer.
What substance is contained within the synaptic vesicles of the axon terminal?
Acetylcholine (ACh)
In adults, red bone marrow is primarily found in which locations?
Skull, vertebrae, ribs, sternum, part of pelvic girdle
Which hormone stimulates osteoblasts to secrete RANKL?
Parathyroid hormone (PTH)
The functional contractile unit of a muscle fiber, defined as the segment from Z disc to Z disc, is the:
Sarcomere
What event directly causes the regulatory protein tropomyosin to move off the active sites on actin, allowing contraction to occur?
(_____ binding to ______)
Calcium binding to troponin
One function of the skeleton is acid-base balance. How does it buffer blood against large pH changes?
By altering phosphate and carbonate salt levels
Which cell type originates from the same bone marrow stem cells that give rise to blood cells, unlike other bone cells?
Osteoclasts
Why are postmenopausal white women at the greatest risk for osteoporosis?
Ovaries cease to secrete estrogen, which normally inhibits bone resorption
The gap between the axon terminal and the sarcolemma at the neuromuscular junction is the:
Synaptic cleft
What event immediately follows the depolarization phase of an action potential in a muscle fiber?
The Na+ gates close and K+ gates open, leading to repolarization.
The Length–Tension Relationship states that the greatest force is produced when a muscle contracts at its:
Optimum resting length