In human body, the hormone which is secreted into blood and which controls the rate of heart beat is
- A.Adrenaline
- B.Thyroxine
- C.Insulin
- D.Testosterone
Correct answer
Explanation
The correct answer is A, Adrenaline. Adrenaline, released by the adrenal glands into the blood, speeds up the heart beat when the body faces stress or danger.
The adrenal glands sit on top of the kidneys, and their inner part, the medulla, secretes adrenaline. In a 'fight or flight' moment, adrenaline makes the heart beat faster and stronger, widens the airways, raises blood sugar and sends more blood to the muscles. That is why it is called the emergency hormone, and doctors use it as an injection in severe allergic shock and cardiac arrest.
B is wrong: thyroxine from the thyroid sets the body's overall rate of metabolism; it is not the hormone that regulates moment-to-moment heart rate.
C is wrong: insulin from the pancreas lowers blood sugar by helping cells take in glucose.
D is wrong: testosterone from the testes controls male sexual characters and muscle growth.
Exam tip: adrenaline = adrenal medulla = fight or flight hormone.
Practice Questions
View allThe speed of the wind is measured by
- A.wind vane
- B.wind rose
- C.barometer
- D.anemometer
Show answer
An anemometer measures how fast the wind is blowing; its name comes from the Greek word anemos, meaning wind.
Read the full explanation →Brilliance of diamond is due to
- A.interference of light
- B.diffraction of light
- C.polarization of light
- D.total internal reflection of light
Show answer
Light that enters a cut diamond is reflected again and again inside it before it escapes, which makes the stone sparkle.
Read the full explanation →Which one of the following is NOT an electromagnetic wave ?
- A.Light wave
- B.Radio wave
- C.Sound wave
- D.Micro wave
Show answer
Sound is a mechanical wave that needs a medium to travel, while the other three are electromagnetic waves. Sound travels as a longitudinal wave of compressions and rarefactions in air, water or solids, which is why it cannot pass through a vacuum.
Read the full explanation →Which one of the following is NOT true for an electromagnetic wave ?
- A.Electromagnetic wave transports energy and momentum
- B.Electromagnetic wave can be polarized and reflected
- C.Electromagnetic wave is longitudinal
- D.Electromagnetic wave propagation is described by the varying electric and magnetic fields
Show answer
Electromagnetic waves are transverse, not longitudinal, so this statement is false. In an electromagnetic wave the electric field and the magnetic field oscillate at right angles to each other and both at right angles to the direction in which the wave travels.
Read the full explanation →Which one of the following frequency ranges is sensitive to human ears ?
- A.0-200 Hz
- B.20-20,000 Hz
- C.200-20,000 Hz only
- D.2,000-20,000 Hz only
Show answer
The normal human ear hears sound from about 20 hertz to 20,000 hertz, the audible range. Frequency, measured in hertz, is the number of vibrations per second, and it decides the pitch of a sound: the higher the frequency, the shriller the note.
Read the full explanation →