C3.1 - action of hormones

Question 1

When is epinephrine secreted?

Answer 1

Epinephrine is secreted by the adrenal glands, in response to a threat perceived by the amygdala that sends impulses via the hypothalamus.

Question 2

How can epinephrine affect the body?

Answer 2

Epinephrine has widespread effects in the body, with effects that facilitate intense muscle contraction.

Question 3

What are examples of how epinephrine affects the body?

Answer 3

Dilated pupils - more light enters the eyes.

Dilated air passages - increase ventilation volumes, so more oxygen enters the blood.

Increased glycogen hydrolysis and glucose release from liver - more energy released through respiration.

Increased heart rate/heart contraction force - increase rate of transport of oxygen and glucose.

Increased blood flow to muscles - increase respiration rate, releasing energy for more intense muscle contraction.

Question 4

How is epinephrine secreted?

Answer 4

1) The amygdala perceives a threat, through processing of sensory input information.
2) The amygdala stimulates the hypothalamus.
3) The hypothalamus sends impulses to the adrenal gland.
4) The adrenal gland released epinephrine.

Question 5

How is melatonin released?

Answer 5

Melatonin is released by the pineal gland.

Question 6

When is melatonin released?

Answer 6

The pineal gland is inhibited by light, and so released melatonin just after sunset.

Question 7

How do melatonin levels change throughout the day?

Answer 7

Thus, for animals that are most active during the day, melatonin levels are low during the day and peak during the middle of the night.

Question 8

How does melatonin establish circadian rhythms within an organism?

Answer 8

• There is a diurnal (daily) pattern of melatonin secretion, which helps to establish an organism’s cycle of sleeping and waking.
• Over time, our bodies become aligned with this circadian rhythm, and the diurnal pattern anticipates the changes in light intensity.

Question 9

Why does jet lag occur?

Answer 9

When a person changes time zones, their natural diurnal pattern of melatonin secretion no longer matches the external light stimuli.

Question 10

How can jet lag be treated?

Answer 10

Talking a melatonin supplement about an hour before your target sleep time can help to reset a person’s circadian rhythm.