Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

47. Muscle Systems

Musculoskeletal System

General Biology

47. Muscle Systems

Musculoskeletal System

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1:05 minutes

Problem 9

Textbook Question

Muscle A and muscle B have the same number of fibers, but muscle A is capable of more precise control than muscle B. Which of the following is likely to be true of muscle A? (Explain your answer.)
a. It is controlled by more neurons than muscle B
b. It contains fewer motor units than muscle B
c. It is controlled by fewer neurons than muscle B
d. It has larger sarcomeres than muscle B

Verified step by step guidance

Understand the concept of motor units: A motor unit consists of a single motor neuron and all the muscle fibers it controls. Precision in muscle control is achieved when each motor neuron controls fewer muscle fibers, allowing finer adjustments.

Analyze the relationship between motor units and precision: Muscles capable of more precise control typically have more motor units, meaning more neurons control smaller groups of muscle fibers. This allows for finer control of movement.

Evaluate the options: Option (a) suggests muscle A is controlled by more neurons, which aligns with the idea that more motor units lead to greater precision. Option (b) suggests fewer motor units, which would reduce precision. Option (c) suggests fewer neurons, which contradicts the need for more motor units for precision. Option (d) mentions larger sarcomeres, which are unrelated to precision control.

Eliminate incorrect options: Based on the explanation, options (b), (c), and (d) can be ruled out because they do not support the idea of increased precision in muscle control.

Conclude the correct answer: The most likely explanation is that muscle A is controlled by more neurons than muscle B, as this allows for more motor units and finer control.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Motor Units

A motor unit consists of a single motor neuron and all the muscle fibers it innervates. Muscles that require precise control, such as those involved in fine motor skills, typically have smaller motor units, allowing for more refined movements. In contrast, muscles that perform gross movements have larger motor units, which can control more fibers but with less precision.

Neuron Control

The number of neurons controlling a muscle affects its precision of movement. More neurons can lead to more motor units, which allows for finer control over muscle contractions. This is particularly important in muscles that perform delicate tasks, where precise adjustments are necessary for effective function.

Sarcomere Structure

Sarcomeres are the basic contractile units of muscle fibers, composed of actin and myosin filaments. While the size of sarcomeres can influence muscle contraction strength, it does not directly relate to the precision of control. Therefore, larger sarcomeres are not necessarily indicative of a muscle's ability to perform precise movements.

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Are their muscles somehow different from those of less successful athletes and non-athletes?

Compare and contrast the structure and function of the three types of skeletal muscle fibers.

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