Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

1. Introduction to Anatomy & Physiology

Feedback Loops: Positive Feedback

Anatomy & Physiology

1. Introduction to Anatomy & Physiology

Feedback Loops: Positive Feedback

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Multiple Choice

Which of the following best describes the two positive-feedback loops involved in the defecation reflex?

Release of bile from the gallbladder and increased gastric motility.

Inhibition of the internal anal sphincter and relaxation of the external anal sphincter.

Stretching of the rectal wall increases peristalsis, and voluntary contraction of abdominal muscles increases rectal pressure.

Activation of the sympathetic nervous system and decreased intestinal motility.

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Verified step by step guidance

Understand the concept of positive-feedback loops: Positive-feedback loops amplify a physiological response rather than stabilizing it. In the context of the defecation reflex, these loops enhance the process of expelling feces from the body.

Identify the key components of the defecation reflex: The defecation reflex involves the rectum, anal sphincters, and abdominal muscles. Stretching of the rectal wall triggers peristalsis, which is a series of wave-like muscle contractions that move feces toward the anus.

Analyze the first positive-feedback loop: Stretching of the rectal wall by feces stimulates sensory neurons, which send signals to the spinal cord. This leads to increased peristalsis in the rectum, further pushing feces toward the anus and amplifying the reflex.

Examine the second positive-feedback loop: Voluntary contraction of abdominal muscles increases intra-abdominal pressure, which compresses the rectum and enhances rectal pressure. This action further facilitates the expulsion of feces.

Connect the loops to the correct answer: The two positive-feedback loops involved in the defecation reflex are stretching of the rectal wall increasing peristalsis and voluntary contraction of abdominal muscles increasing rectal pressure. These processes work together to ensure effective defecation.