Home / IB DP Biology- C3.1 Integration of body systems – IB Style Questions For SL Paper 1A

IB DP Biology- C3.1 Integration of body systems - IB Style Questions For SL Paper 1A -New Syllabus

IBDP Biology Paper 1 - All Chapters

Question

Which is the receptor in a pain reflex arc?

(A) Skeletal muscle
(B) Grey matter of spinal cord
(C) Pituitary gland
(D) Sensory nerve ending
▶️ Answer/Explanation

Correct Answer: \( \boxed{\mathbf{D}} \)

The receptor in a pain reflex arc is the sensory nerve ending (nociceptor), which detects harmful stimuli and initiates a nerve impulse. The impulse is then transmitted to the spinal cord, leading to a rapid reflex response.

Question

Which of the following structures functions as the effector in a pain reflex arc?

A. Grey matter
B. Skeletal muscle
C. Motor neuron
D. Pineal gland

▶️ Answer/Explanation
In a pain reflex arc, sensory neurons detect the stimulus and send signals to the spinal cord, where they connect with motor neurons. The motor neurons then stimulate skeletal muscles, which act as the effectors to produce a rapid response (e.g., withdrawing the hand from a hot surface).
✅ Answer: (B) Skeletal muscle

Question

What is a function of the pancreas?

A. To control the rate of metabolism by releasing thyroxine when metabolic rate is low
B. To release glucagon when blood glucose levels are low
C. To release insulin when blood glucose levels are low
D. To secrete an endopeptidase which lowers the blood glucose levels

▶️ Answer/Explanation

Pancreas function diagram Answer: (B) To release glucagon when blood glucose levels are low

Explanation:
The pancreas helps regulate blood glucose levels by releasing two main hormones:

• When blood glucose is low, the pancreas releases glucagon. Glucagon signals the liver to break down glycogen into glucose and release it into the bloodstream.

• When blood glucose is high, the pancreas releases insulin, which helps cells absorb glucose and reduces blood glucose levels.

Option Evaluation:
A. Incorrect — Thyroxine is produced by the thyroid gland, not the pancreas.
B. Correct — Glucagon is released when blood glucose is low.
C. Incorrect — Insulin is released when blood glucose is high, not low.
D. Incorrect — Endopeptidases digest proteins and do not regulate blood glucose.

✅ Answer: (B)

 
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