Concept explainers
Videos
If you compare electron micrographs of a relaxed skeletal muscle fiber and a fully contracted muscle fiber, which would you see only in the relaxed fiber?
a. Z discs
b. Sarcomeres
c. I bands
d. A bands
e. H zones
Introduction:
The skeletal muscle fibers are made of striated muscle tissues, which consists of alternating light (I) and dark bands (A). I-band consists of a dark region known as Z disc. On the other hand, A band consists of a light region known as H-zone. I-band consists only of thin actin filaments, while the A-band consists of both actin and myosin filaments. All these units of a muscle fiber makes sarcomere. The micrograph of a sarcomere is shown as below:
Answer to Problem 1MC
Correct answer:
I bands and the H zones of the skeletal muscle fiber will be visible only in the micrograph of the relaxed fiber.
Explanation of Solution
Explanation for the correct answer:
Option (c) and option (e) are given as I bands, and H zones, respectively. A sarcomere is basically a unit of the striated muscle tissue. Repeating units of Z lines are present in this and the actin molecules are bounded to these lines forming a border in the sarcomere. Alternating I which are light and A which are dark bands are present. When looking closer, I band comprises of a midline interruption which is known as Z disc while in the A band there is a lighter middle section known as H zone. During the muscle contraction, the actin filaments move over the myosin filaments according to the sliding filament theory. I-band and the H zone tends to overlap when a muscle is contracted. When they overlap it becomes difficult to observe I and H bands. Therefore, these will only be visible in the relaxed position. Hence, option (c) and option (e) are correct.
Explanation for the incorrect answers:
Option (a) is given as Z discs. The Z discs are dark stripes, which marks the ending of a sarcomere. These dark zones can be clearly seen in both the contracted and relaxed electron micrographs of the skeletal muscles. So, it is an incorrect option.
Option (b) is given as sarcomere. This is the part of the muscle composing of the thin and thick filaments. These thick and thin filaments forming the sarcomere are the basic unit of the muscle tissue present between the two Z discs. Therefore, sarcomere will be visible in both the contracted as well as a relaxed muscle fiber. So, it is an incorrect option.
Option (d) is given as A bands. These are the darker areas of the sarcomere. These bands do not shrink, when the muscle contracts, and hence, can be seen both in relaxed and contracted position. So, it is an incorrect option.
Hence, options (a), (b), and (d) are incorrect.
Thus, in a relaxed state, I-band and H-zone will be visible, which will disappear during contraction of the muscle.
Want to see more full solutions like this?
Chapter 6 Solutions
EBK ESSENTIALS OF HUMAN ANATOMY & PHYSI
- Older adults have unique challenges in terms of their nutrient needs and physiological changes. Some changes may make it difficult to consume a healthful diet, so it is important to identify strategies to help overcome these obstacles. From the list below, choose all the correct statements about changes in older adults. Select all that apply. Poor vision can make it difficult for older adults to get to a supermarket, and to prepare meals. With age, taste and visual perception decline. As people age, salivary production increases. In older adults with dysphagia, foods like creamy soups, applesauce, and yogurt are usually well tolerated. Lean body mass increases in older adults.arrow_forwardWhen physical activity increases, energy requirements increase also. Depending on the type, intensity, and duration of physical activity, the body’s requirements for certain macronutrients may change as well. From the list below, choose all the correct statements about the effects of increased physical activity or athletic training. Select all that apply. An athlete who weighs 70 kg (154 lb) should consume 420 to 700 g of carbohydrate per day. How much additional energy an athlete needs depends on the specific activity the athlete engages in and the frequency of the activity. Those participating in vigorous exercise should restrict their fat intake to less than 15%% of total energy intake. Athletes who are following energy-restricted diets are at risk for consuming insufficient protein. The recommendation to limit saturated fat intake to less than 10%% of total energy intake does not apply to athletes or those who regularly engage in vigorous physical activity.arrow_forwardWhen taking vitamins and vitamin-mineral supplements, how can one be sure they are getting what they are taking?arrow_forward
- How many milligrams of zinc did you consume on average per day over the 3 days? (See the Actual Intakes vs. Recommended Intakes Report with all days checked.) Enter the number of milligrams of zinc rounded to the first decimal place in the box below. ______ mg ?arrow_forwardthe direct output from molecular replacement is a coordinate file showing the orientation of the unknown target protein in the unit cell. true or false?arrow_forwardthe direct output from molecular replacement is a coordinate file showing the orientation of the unknown target protein in the unit cell. true or false?arrow_forward
- Did your intake of vitamin C meet or come very close to the recommended amount? yes noarrow_forwardWhich of the following statements about hydration is true? Absence of thirst is a reliable indication that an individual is adequately hydrated. All of these statements are true. Although a popular way to monitor hydration status, weighing yourself before and after intensive physical activity is not a reliable method to monitor hydration. Urine that is the color of apple juice indicates dehydration. I don't know yetarrow_forwardThree of the many recessive mutations in Drosophila melanogaster that affect body color, wing shape, or bristle morphology are black (b) body versus grey in wild type, dumpy (dp), obliquely truncated wings versus long wings in the male, and hooked (hk) bristles versus not hooked in the wild type. From a cross of a dumpy female with a black and hooked male, all of the F1 were wild type for all three of the characters. The testcross of an F1 female with a dumpy, black, hooked male gave the following results: Trait Number of individuals Wild type 169 Black 19 Black, hooked 301 Dumpy, hooked 21 Hooked, dumpy, black 172 Dumpy, black 6 Dumpy 305 Hooked 8 Determine the order of the genes and the mapping distance between genes. Determine the coefficient of confidence for the portion of the chromosome involved in the cross. How much interference takes place in the cross?arrow_forward
- What happens to a microbes membrane at colder temperature?arrow_forwardGenes at loci f, m, and w are linked, but their order is unknown. The F1 heterozygotes from a cross of FFMMWW x ffmmww are test crossed. The most frequent phenotypes in the test cross progeny will be FMW and fmw regardless of what the gene order turns out to be. What classes of testcross progeny (phenotypes) would be least frequent if locus m is in the middle? What classes would be least frequent if locus f is in the middle? What classes would be least frequent if locus w is in the middle?arrow_forward1. In the following illustration of a phospholipid... (Chemistry Primer and Video 2-2, 2-3 and 2-5) a. Label which chains contain saturated fatty acids and non-saturated fatty acids. b. Label all the areas where the following bonds could form with other molecules which are not shown. i. Hydrogen bonds ii. Ionic Bonds iii. Hydrophobic Interactions 12-6 HICIH HICIH HICHH HICHH HICIH OHHHHHHHHHHHHHHHHH C-C-C-C-C-c-c-c-c-c-c-c-c-c-c-c-C-C-H HH H H H H H H H H H H H H H H H H H HO H-C-O H-C-O- O O-P-O-C-H H T HICIH HICIH HICIH HICIH HHHHHHH HICIH HICIH HICIH 0=C HIC -C-C-C-C-C-C-C-C-CC-C-C-C-C-C-C-C-C-H HHHHHHHHH IIIIIIII HHHHHHHH (e-osbiv)arrow_forward
Comprehensive Medical Assisting: Administrative a...NursingISBN:9781305964792Author:Wilburta Q. Lindh, Carol D. Tamparo, Barbara M. Dahl, Julie Morris, Cindy CorreaPublisher:Cengage Learning
Human Physiology: From Cells to Systems (MindTap ...BiologyISBN:9781285866932Author:Lauralee SherwoodPublisher:Cengage Learning
Concepts of BiologyBiologyISBN:9781938168116Author:Samantha Fowler, Rebecca Roush, James WisePublisher:OpenStax College
Human Biology (MindTap Course List)BiologyISBN:9781305112100Author:Cecie Starr, Beverly McMillanPublisher:Cengage Learning