Question

A person entering an empty room suddenly finds a snake right in front of the door opening. Which one of the following is likely to happen in his neuro-hormonal control system?
A. Sympathetic nervous system is activated releasing epinephrine and norepinephrine from adrenal medulla
B. Neurotransmitters diffuse rapidly across the cleft and transmit a nerve impulse
C. Hypothalamus activates the parasympathetic division of brain
D. Sympathetic nervous system is activated releasing epinephrine and norepinephrine from adrenal cortex

Answer 1

Hint: Adrenals are paired glands placed on the top of the kidneys. They have a dual origin, mesoderm and ectoderm. These are conical and yellowish bodies in structure with two differentiated regions- adrenal cortex and medulla.

Complete answer: Adrenal cortex is an external firm, pale yellowish pink tissue formed from mesoderm. It further shows three concentric regions outer, middle and inner and each of these regions produce their own hormones. It is essential for life as it releases mineralocorticoids, glucocorticoids and sexcorticoids.
The adrenal medulla is an internal soft, dark and reddish brown tissue derived from the ectoderm. It enables the animal to face the physical and emotional stress. At the time of stress or danger the central nervous system stimulates the adrenal medulla to release epinephrine and norepinephrine. In addition, the sympathetic nervous system is also activated to release more norepinephrine.
These hormones help prepare the animals to face special conditions created by physical stress such as fall in blood pressure or blood sugar.
The hormones increase blood pressure, sugar level of blood, blood supply of heart, and skeletal muscles and brain through dilation of their small arteries and oxidative metabolism. The hormones also cause contraction of spleen to squeeze out of the reserve supply of blood, dilation of pupil and contraction of arrector pili muscles of the skin to cause gooseflesh.
So, the correct answer is “Option A”.

Note: The above role of adrenaline and noradrenaline is often called fight or flight reaction. It prepares the body for stress conditions. Because of this function, adrenals are also known as glands of emergency.