Hormones

Question 1

Define hormone

Answer 1

A chemical substance, produced by a gland, carried by the blood, which alters the activity of one or more specific target organs and is then destroyed by the liver.

Question 2

State the role of the hormone adrenaline in increasing the blood glucose concentration

Answer 2

Adrenaline stimulates cells in liver to convert glycogen to glucose , which diffuses into the blood - more available to the muscles as a source of energy for muscle contractions .

Question 3

Compare nervous and hormonal control systems

Answer 3

Forms of information: electrical impulses.hormones
Pathways: along neurones/in the blood
Target area: only the area at the end of a neurone/whole tissue or organ

Question 4

Define homeostasis

Answer 4

The maintenance of a constant internal environment - so that enzymes control metabolism efficently

Question 5

Define negative feedback

Answer 5

The mechanism used in homeostasis for maintaining near constant conditions in the body

Question 6

When the blood glucose concentration is high, what happen next?

Answer 6

Pancreas secretes hormone insulin which stimulates liver cells to convert glucose to glycogen - absorbs lots of glucose from the blood

Question 7

When you exercise, the muscle take up lots of glucose from the blood - blood glucose concentration decreases, what happens next?

Answer 7

Other cells in the pancreas secrete hormone glucagon which stimulates liver cells to break down glycogen to glucose, which diffuses into the blood

Question 8

In the heat, what does the brain does?

Answer 8

The brain detects an increase in blood temperature - sends impulses to the skin/increase the rate of sweating - more heat is lost by evaporation from the skin surface

Question 9

In the cold, what does the brain does?

Answer 9

The brain detects an decrease in blood temp - seat glands stop producing sweat and the hair erector muscles contract to raise the hairs. Body starts to shiver as body muscles contract which release heat from respiration. Blood flowed through the muscles and is warmed by this heat.

Question 10

Define vasodilation

Answer 10

Muscles in the walls of arterioles relax.
Vessels widen - increase in blood flow through the capillaries
More heat is now lost by convection and radiation.

Question 11

Define vasoconstriction

Answer 11

The muscles in the walls of arterioles contract so the vessels become narrower. This reduces the blood flow through the capillaries and the blood is diverted to stay beneath the fat layer in the skin.