A 3-year-old boy is

brought to the pediatrician. The parents are worried that the boy has started

falling unexpectedly when walking. Physical examination reveals muscle weakness

especially in the lower extremities. As muscular dystrophy is suspected here

based on history and other investigations, a biopsy of his skeletal muscle is

taken and sent to a pathologist. However, the pathologist's report states that

the sample contains only healthy muscle tissue. Which of the following

characteristics can be used to describe the specimen?

An investigator is studying muscle contraction in tissue obtained from

the thigh muscle of an experimental animal. After injection

of radiolabeled ATP, the tissue is stimulated with electrical impulses.

ATP binds to myosin heads during contraction. In which part of the sarcomere

does this reaction occur?

An investigator is studying the microstructure

of skeletal muscle fibers to identify new targets for skeletal muscle

relaxation. He obtains a biopsy from the biceps muscle of a test subject and

observes it under a transmission electron microscope. A photomicrograph of the

structures seen during microscopy is shown. Which of the following parts

contains the greatest proportion of actin filaments? 

Cardiomyocytes, the

cardiac muscle cells, work throughout our lives. If we think about this

information, how will these cells differ from skeletal muscle fibers?

A 13-year-old boy is injured during a football

match and is taken to the hospital for stitches. During the game he fell and cut

himself on a piece of broken glass. The shard cut through the skin on the front

of his thigh and cut into the outer sheath surrounding the quadriceps femoris

muscle. What's this superficial covering of the muscle called?

A group of students is reviewing muscle

tissue before a test and come across a question on which they completely disagree. Can you help them sort out their disagreement? It is all about the

statement that cardiomyocytes, the cells of the heart muscle, have only the

classical ability to contract. Others claim that these cells have other

functions in addition to this one. Which of these four statements is closest to

the truth?

55-year-old wo

man

with a history of chronic kidney disease comes

to the physician for a 2-month history of easy

fatigability. Physical examination shows subconjunctival pallor. Her hemoglobin

concentration is 80 g/l. Treatment with erythropoietin has been administered. A

peripheral blood smear is obtained one week after treatment. A photomicrograph

of the smear after specialized staining is shown. The prominent color of the intracellular structure in

some of the cells is most likely the result of staining which of the following?

A 24-year-old female patient is brought to the hospital by ambulance

after being stung by bees for a severe allergic reaction. As part of an

allergic reaction, many mediators are released. Among the most abundant are

heparin and histamine. Their largest amount is stored and subsequently released

after contact with the allergen from the granules of two cell types - mast

cells and…. (fill in the second cell type).