B9.4 : Homeostasis

Question 1

Homeostasis

Answer 1

1. Homeostasis is the maintenance of a constant internal environment
2. It is the term used to describe all processes that occur for the purpose of keeping the internal conditions of a cell or organism within set limits in response to internal and external environmental changes.

Question 2

Enzyme functioning

Answer 2

1. Because humans are organisms that live in a changing environment, we must regulate our body’s internal conditions to make sure our enzymes and cells function well.

Question 3

Denaturing

Answer 3

1. If conditions are not optimal, then our enzymes can denature (change shape).
2. This reduces their ability to catalyse (speed-up) metabolic reactions (chemical reactions in organisms). This can be fatal.

Question 4

Purpose of homeostasis

Answer 4

1. Enzyme functioning

2. Denaturing of enzymes

Question 5

Control systems

Answer 5

1. Control systems use both nervous and chemical responses.

2. Control systems are made up of three parts

Question 6

3 parts of control systems

Answer 6

1. coordination centres
2. Effectors (muscles or glands)
3. Receptors

Question 7

Coordination centres

Answer 7

Coordination centres receive and process information arriving from receptor cells.

Question 8

Effectors (muscles or glands)

Answer 8

Effectors (muscles or glands) carry out responses to stimuli (events or things) that help to restore optimum levels.

Question 9

Receptors

Answer 9

Receptor cells detect changes in the environment.

Question 10

The Body’s Negative Feedback Loop

Answer 10

1. When our internal conditions are optimal, the body does not need to respond.
2. If an internal condition changes and is no longer optimal, the body works to reverse the change and return conditions to the optimum.
3. This process is called negative feedback and needs all of the components of the nervous system to work together.
4. This response is given by muscles and glands

Question 11

Controlling Blood Glucose Levels

Answer 11

It’s important to keep blood glucose levels within a small range (for humans, between 6-8 mmol/dm3).

Question 12

What happens when theres too much glucose

Answer 12

1. This can have a negative impact on osmosis (movement of water between cells) by affecting concentration gradients.
2. When the concentration of blood glucose is too high, the pancreas will release the hormone insulin into the bloodstream

Question 13

What happens when theres too little glucose

Answer 13

1. Glucose is important for respiration - the process that releases the energy needed by every living cell.
2. Organisms can’t produce enough energy if they don’t have enough glucose.
3. If the concentration of blood glucose is too low, the pancreas releases the hormone glucagon into the bloodstream

Question 14

Why is it important to control blood glucose levels

Answer 14

1. Glucose is fuel for respiration. This is the chemical reaction that releases energy in many living cells.
2. Therefore, if blood glucose levels are too low, then an organism cannot meet its energy demands.
3. But if there is too much glucose in the blood, this has an impact on osmosis by affecting concentration gradients.

Question 15

How to detect blood glucose

Answer 15

1. As blood flows through the pancreas, the body can detect if the blood glucose concentration is too high or too low
2. The mechanisms that occur in response to abnormal levels of glucose in the blood are example of negative feedback

Question 16

Insulin

Answer 16

1. When the liver and muscle tissues detect the presence of insulin, they convert the excess glucose into glycogen
2. This process continues until the pancreas detects a normal blood glucose concentration

Question 17

Glucagon

Answer 17

1. When the liver detects the presence of glucagon, it converts stores of glycogen back into glucose so they can be released into the bloodstream
2. This process continues until the pancreas detects a normal blood glucose concentration

Question 18

Glycogen

Answer 18

1. a form of glucose
2. It is insoluble
3. It can be stored for later use

Question 19

Thermoregulation

Answer 19

1. Our body temperature needs to be kept as close to 37°C as possible.
2. Receptors detect temperature changes and relay the information to the central nervous system (CNS).
3. The CNS then allows effectors (muscles or glands) to respond

Question 20

Receptors in the brain

Answer 20

Receptors in the thermoregulatory centre of our brain (called the hypothalamus) monitor the internal body temperature as blood flows through the brain.

Question 21

receptors on the skin

Answer 21

1. Receptors on the surface of the skin monitor the temperature at the surface of the body.
2. Receptors on the skin detect temperatures outside the body and send messages to the nervous system via sensory neurones.
3. Body temperature is kept fairly constant by controlling the action of sweat glands, hair erector muscles (which move hairs in the skin) and blood vessels.

Question 22

Warming up and Cooling down

Answer 22

Receptors send information to the brain about how hot or cold the body is. A response is then coordinated which either warms or cools the body.

Question 23

Body’s response when it is too hot

Answer 23

1. Sweat is released from sweat glands under the skin.
2. Hairs lie flat.
3. Arteriole blood vessels dilate to allow more blood to enter capillaries that pass close to the skin surface (vasodilation).

Question 24

Body’s response when it is too cold

Answer 24

1. Muscle contractions increase, causing shivering.
2. Hairs stand on end.
3. Arteriole blood vessels constrict to reduce blood flow in capillaries (vasoconstriction).

Question 25

Vasodilation

Answer 25

1. Vaso means that something is related to blood vessels

2. Vasodilation is when blood vessels dilate to allow more blood to enter capillaries.

Question 26

vasoconstriction

Answer 26

1. Vaso means that something is related to blood vessels

2. Vasoconstriction is when blood vessels constrict to reduce blood flow in capillaries.

Question 27

Shivering

Answer 27

1. When we are too cold, muscles start to contract automatically. This makes us shiver.
2. This process needs energy, which is generated through respiration.
3. Respiration produces heat, which warms us up.

Question 28

Sweating

Answer 28

1. Sweat glands (in the middle layer of skin, called the dermis) release water, which covers the skin.
2. Heat energy from the body is transferred to this water and, when it has enough energy, it evaporates.
3. As it evaporates, it takes the heat energy with it. This lowers the average temperature of the body.

Question 29

Thermoregulation - Body Hairs

Answer 29

1. Each hair on the body is controlled by a hair erector muscle.

Question 30

Body hairs when its hot

Answer 30

When we are too hot, the hair erector muscle relaxes. This causes the hair to lie flat.

Question 31

Body hairs when its cold

Answer 31

1. When we are too cold, the hair erector muscle contracts. This causes the hair to stand on end (which pulls on the skin giving you goosebumps).
2. When all the hairs are standing on end, they trap an insulating layer of air around the body.

Question 32

Thermoregulation - Blood Vessels

Answer 32

1. Arterioles supplying the capillary networks of the skin have layers of smooth muscle tissue in their walls.
2. They respond differently when we are too hot or too cold.

Question 33

Blood vessels when its hot

Answer 33

1. If we are too hot, then the muscular walls relax.
2. This is called vasodilation.
3. This allows more blood to enter and flow through capillaries close to the skin surface. The excess heat energy is transferred to the surroundings.

Question 34

Blood vessels when its cold

Answer 34

1. If we are too cold, then the muscular walls contract.
2. This is called vasoconstriction.
3. This reduces the blood flow to the skin surface and heat energy is kept inside the body.

Question 35

Blood Flow in Ducks

Answer 35

1. If humans are too cold, the walls of our blood vessels contract and we reduce the amount of blood near to the skin.
2. Ducks lose heat from their feet when they are in cold water.
3. They have evolved to decrease the blood flow to their feet.
4. This blood is also cooled so that less heat is lost to (conducted away by) the cold water when it reaches the ducks’ feet.

Question 36

Body Temperature and Hair

Answer 36

1. The hairs on this man’s body are controlled by hair erector muscles.
2. Hairy men will have more hairs that stand on end when they are cold.
3. This will warm hairy men up a little bit faster than less hairy men.

Question 37

How the liver and pancreas works to reduce the blood glucose concentration if it gets too high

Answer 37

1. when blood passes through the pancreas, it can detect if the level of blood glucose levels are too high
2. The pancreas produces and releases insulin into the bloodstream
3. When the liver and muscle tissues detect the presence of insulin, they convert the excess glucose into glycogen.
4. The glycogen is stored in the liver
5. This process continues until the pancreas detects normal blood glucose concentration

Question 38

How the liver and pancreas works to reduce the blood glucose concentration if it gets too low

Answer 38

1. when blood passes through the pancreas, it can detect if the level of blood glucose levels are too low
2. The pancreas produces and releases glucagon into the bloodstream
3. When the liver and muscle tissues detect the presence of glucagon, it converts stores of glycogen stored in the liver back into glucose so they can be released into the bloodstream
4. This process continues until the pancreas detects normal blood glucose concentration