Homeostasis (B9.3)

Question 1

How is homeostasis maintained?

Answer 1

a change in the internal condition triggers the detector (sensor), which sends information to the effector, which stimulates a response.

Question 2

what is negative feedback?

Answer 2

the response until the sensor detects levels have continued to normal. The sensor then sends information to the effector to switch it off and perhaps act in the opposite way

Question 3

describe how the body would respond to a rise in body temperature?

Answer 3

The rise in body temperature detected by the thermoregulatory centre causes it to send nerve impulses to the skin, which result in effectors (arterioles and sweat glands) responding. The arterioles dilate (a process called vasodilation) and the sweat glands secrete more sweat.

Question 4

describe how the body would respond to a decrease in body temperature? (negative feedback)

Answer 4

As the temperature drops below normal, the thermoregulatory centre detects this and sends nervous impulses to switch off the processes of vasodilation and sweating, as well as triggering other responses, e.g. vasoconstriction and shivering.

Question 5

how is the liver an example of an homeostatic organ?

Answer 5

it controls the levels of a number of components of the blood, including glucose.

Question 6

how does the body respond to an increase in blood glucose levels?

Answer 6

-After a meal, blood glucose concentrations rise
-excess blood glucose is removed by the liver and converted into the storage carbohydrate glycogen using insulin hormone

Question 7

how is insulin secreted?

Answer 7

-When blood glucose levels rise, the islet cells of the pancreas detect the change and secrete insulin in response.
-The insulin is transported to the liver in the blood plasma. Once at the liver, insulin stimulates liver cells to take up the glucose from the blood and convert it to glycogen.
-Insulin also stimulates other body cells to take up more glucose for use in respiration.

Question 8

how does the body respond to a decrease in blood glucose levels?

Answer 8

the islet cells in the pancreas are stimulated to release a different hormone – glucagon. Glucagon is transported by the blood plasma to the liver where it acts on the cells there, causing them to convert stored glycogen back to glucose to raise blood glucose levels.

Question 9

what is type 1 diabetes ?

Answer 9

inability of the pancreatic islet cells to secrete enough insulin to control blood glucose correctly. Type 1 diabetes is also known as ‘insulin-dependent’ diabetes.

Question 10

what is type 1 diabetes caused by?

Answer 10

it can be inherited or triggered by an event e.g viral infection which can cause body immune system to attack islet cells of pancreas, so they stop producing sufficient insulin (autoimmune disease)

Question 11

what are the symptoms of type 1 diabetes?

Answer 11

These include feeling tired, feeling very thirsty, frequent urination and weight loss.. Glucose maybe present in urine.Eating a meal high in carbohydrates can result in the diabetic falling into a coma. Similarly, a shortage of food can result in the diabetic falling into a coma.

Question 12

how can you control type 1 diabetes?

Answer 12

-regulate diet to stop fluctuating glucose levels
-regular blood tests
-regular insulin injections

Question 13

what is type 2 diabetes caused by?

Answer 13

a more common form of diabetes. It can be inherited or a result of lack of exercise and unhealthy diet. These factors can lead to insulin resistance, where the body doesn’t use insulin properly.

Question 14

what is the regulation of the amount of water in the body?

Answer 14

osmoregulation.

Question 15

how is the amount of water in the body regulated?

Answer 15

The brain signals to the pituitary gland to increase or decrease the amount of ADH (antidiuretic hormone) it secretes.

Question 16

what is ADH?

Answer 16

ADH is a hormone, carried in the blood, which signals to the kidneys how much water they should excrete or reabsorb.

Question 17

what does high levels of ADH cause?

Answer 17

High levels of ADH cause the kidneys to reabsorb more water, so less urine is excreted. The ADH binds to the collecting ducts of the nephrons making them more permeable to water. The water leaves the ducts and re-enters the blood.

Question 18

what does low levels of ADH cause?

Answer 18

Low levels of ADH cause the kidneys to reabsorb less water, so more urine is excreted. The water is reabsorbed from the filtrate in the renal tubules of the nephrons of the kidneys, back into the blood plasma of the capillaries, by osmosis.

Question 19

what is the regulation of body temperature called?

Answer 19

thermoregulation

Question 20

what happens to the body when the body temperature increases?

Answer 20

The arterioles dilate (a process called vasodilation) and the sweat glands secrete more sweat. Both of these processes result in the cooling of the skin, which brings down the elevated body core temperature.

Question 21

what happens when the body temperature decreases?

Answer 21

the thermoregulatory centre detects this and sends nervous impulses to switch off the processes of vasodilation and sweating, as well as triggering other responses, e.g. vasoconstriction, shivering and the erection of hairs on the surface of the skin to trap an insulating layer of air.

Question 22

what are effectors in the thermoregulatory response?

Answer 22

blood vessels in the skin. Arterioles not capillaries as capillaries don’t have muscles so cannot vasodilate or vasoconstrict.