hormones

Question 1

A hormone is…

Answer 1

A chemical substance produced in minute quantities by an endocrine gland.

Question 2

How are hormones transported? What are its functions?

Answer 2

It is transported by the blood to target organ(s)

• it influences the growth, development of an organism
• it alters the activity of one or more target organs

Question 3

Where are hormones destroyed?

Answer 3

After hormones have performed their functions, they are eventually destroyed by the liver.

Question 4

Endocrine glands are…

Answer 4

Endocrine glands are ductless glands that secrete hormones directly into the bloodstream, which then transports the hormone around the body.

Question 5

What are some examples of endocrine glands? What do they secrete?

Answer 5

Adrenal gland: adrenaline, pancreas (Islets of Langerhans): insulin and glucagon, pituitary gland.

Question 6

Respiration is a continuous process in all living cells, and _____ is the principal respiratory substrate for most tissues. The normal level of ____ _____ is about ___mM/L of blood, but it varies.

Answer 6

Respiration is a continuous process in all living cells, and glucose is the principal respiratory substrate for most tissues. The normal level of blood glucose is about 4mM/L of blood, but it varies.

Question 7

Most cells (including muscle cells) hold reserves in the form of _____. This _______ is quickly converted to ____ during prolonged physical activity.

Answer 7

Most cells (including muscle cells) hold reserves in the form of glycogen. This polysaccharide is quickly converted to glucose during prolonged physical activity.

Question 8

How are blood glucose levels monitored?

Answer 8

At the pancreas, blood glucose levels are monitored by patches of cells known as the islets of Langerhans.

Question 9

What are the 2 types of cells the islets of Langerhans contain?

Answer 9

Alpha (a) cells - secretes glucagon

Beta (b-ish) cells - secretes insulin

Question 10

What happens when an increase in blood glucose concentration above the norm is detected by receptors?

Answer 10

• Detected by receptors: islets of Langerhans of the pancreas
• Beta cells of islets of Langerhans are stimulated to secrete the hormone INSULIN into the capillary network

Question 11

What does insulin do?

Answer 11

• Insulin stimulates the uptake of glucose by cells, especially the by liver and muscle cells
• Insulin also triggers the conversion of glucose to glycogen and of glucose to fatty acids and fats in liver cells

Question 12

What happens when blood glucose concentration decreases back to normal?

Answer 12

This is detected in the islets of Langerhans, and the beta cells respond by reducing insulin secretion. Insulin is destroyed in the liver and excreted through the kidneys. Blood insulin level falls.

Question 13

What happens when a decrease in blood glucose concentration above the norm is detected by receptors?

Answer 13

• Detected by receptors: the islets of Langerhans of the pancreas
• Alpha cells of islets of Langerhans are stimulated to secrete the hormone glucagon into the capillary network

Question 14

What does glucagon do?

Answer 14

• Glucagon activates the enzymes that convert glycogen and amino acids to glucose
• Glucagon also reduces the rate of respiration of cells

Question 15

What happens when the glucose concentration increases back to normal?

Answer 15

This is detected in the islets of Langerhans, and the alpha cells respond by decreasing glucagon secretion. Glucagon is destroyed in the liver and excreted through the kidneys. Blood glucagon level falls.

Question 16

What is diabetes?

Answer 16

It is a group of diseases in which the body fails to regulate blood glucose levels.

Question 17

What are the signs of diabetes?

Answer 17

Persistently high glucose level, presence of glucose in urine after a meal and slow/difficult healing of wounds

Question 18

What is the treatment for type I diabetes?

Answer 18

Daily injection of insulin into the bloodstream, regular measurement of blood glucose level

Question 19

When is adrenaline secreted?

Answer 19

It is secreted when you are angry, afraid, anxious or stressed.

Question 20

What is adrenaline meant to prepare you for? Are the effects of adrenaline permanent?

Answer 20

Adrenaline prepares your body for “fight or flight” or for states of emergency. The responses that arise from the secretion of adrenaline are temporary as adrenaline is a short-lived hormone.

Question 21

What are the effects of adrenaline secretion? (IMPT)

Answer 21

• Stimulates the liver to convert glycogen to glucose so that more glucose is available for muscle contraction
• Increases the blood glucose level (e.g. when more glucose is released from the liver into the bloodstream)

Question 22

What are the effects of adrenaline secretion? (Continued: “increases…”)

Answer 22

• Increases metabolic rate, so that more energy is released from cellular respiration
• Increases rate of heartbeat and causes a rise in blood pressure so that oxygen and glucose are transported faster to the muscles
• Increases the rate of and depth of ventilation, increasing the rate of uptake of oxygen by the lungs
• Increases the rate of blood clotting to prevent excessive loss of blood

Question 23

What are the effects of adrenaline secretion? (Continued: Constricts/dilate/contracts)

Answer 23

• Constricts arterioles to the gut, thereby decreasing digestive activities
• Contstricts arterioles in the skin, causing paleness, thus channelling more blood to the muscles (e.g. the limbs)
• Dilate pupils to enhance vision
• Contracts hair erector muscles, producing “goosebumps” and causing hair to stand on ends