Question

Given below are two statements.
Statement I - Defecation is an involuntary process that takes place through anal opening guarded by sphincter muscles.
Statement II - Distension, of rectum stimulates pressure sensitive receptors that initiate a neural reflex for egestion.
In light of above statements, select the correct answer from the option given below.

• A. Both statement I and statement II are correct.
• B. Both statement I and statement II are incorrect.
• C. Statement I is correct and statement II is incorrect.
• D. Statement I is incorrect and statement II is correct.

Hint:

Key idea: Defecation = Reflex (involuntary) + Control (voluntary via external sphincter). This dual control is a common exam concept.

Answer 1

The Correct Option is A

Concept: Defecation (egestion) is a reflex action controlled by both involuntary and voluntary mechanisms involving the nervous system and sphincter muscles.
• Internal anal sphincter: Involuntary control (smooth muscle)
• External anal sphincter: Voluntary control (skeletal muscle)
• Defecation reflex: Triggered by rectal distension

Step 1: Analyze Statement I.
Defecation is primarily an involuntary reflex initiated by the autonomic nervous system. However, it is regulated by sphincter muscles, allowing some voluntary control. Thus, Statement I is considered correct.

Step 2: Analyze Statement II.
When the rectum is filled with fecal matter, it stretches (distension), activating pressure-sensitive receptors. These receptors send signals to initiate a neural reflex leading to egestion. Thus, Statement II is correct.

Step 3: Conclusion.
Both statements correctly describe the physiology of defecation. Final Answer: Option (A)