B9.4 - Homeostasis

Question 1

what is homeostasis?

Answer 1

→ the process of maintaining a stable internal environment

Question 2

what is a simple process of homeostasis?

Answer 2

→ example of this: cells in our body require certain conditions to function properly. It can’t be too hot or too cold or acidic or alkaline. Needs a good supply of glucose and water.
→ the definition means that we are able to maintain a stable internal environment despite changes outside of our cells
→ our body uses automatic control systems that can recognise when there is a change from optimal conditions.
→ then sends a signal to reverse that change so the levels go back to normal.

Question 3

what is an automatic control system?

Answer 3

When there is a change from optimal condition → our body sends a signal → reverses the change and then goes back to normal, optimal conditions

Question 4

what are components of an automatic control system?

Answer 4

• Receptors- detect the changes (such as rises in temperature)
• Coordination centres - interpret the change (brain and spinal cord) and decides what needs to be done
• Effectors - carry out the change (such as; muscles contract, glands secrete hormones etc)

These components take place in different parts of the body and signals are needed for them to communicate

Question 5

what is the importance of homeostasis?

Answer 5

For our body to maintain a stable internal environment which keeps our body in the best conditions to operate

Question 6

what is blood glucose concentration?

Answer 6

→ blood glucose concentration describes the amount of sugar in the bloodstream
→ cells need a constant supply of glucose for the process of respiration

Question 7

what is the negative feedback for an increased concentration in blood glucose concentration?

Answer 7

→ big meal (consists of a lot of carbs)
→ the carbohydrates are broken down in the intestines to glucose molecules
→ the glucose molecules are then absorbed into our bloodstream
→ the blood glucose concentration increases.
→ this increase is detected in the pancreas
→ pancreas secretes a hormone known as insulin into the bloodstream
→ insulin travels around the bloodstream and binds to certain receptors on certain cells
→ it tells the cells to take in some of the glucose floating around in the blood
→ the liver and muscles take up a lot of the glucose molecules
→ all the glucose molecules combine to form glycogen which is a long term storage form of glucose
→ all the glucose is then removed from the bloodstream and the blood glucose concentration decreases.

Question 8

what is the hormone secreted when blood glucose concentration increases?

Answer 8

insulin

Question 9

what does insulin do?

Answer 9

→ insulin travels around the bloodstream and binds to certain receptors on certain cells
→ it tells the cells to take in some of the glucose floating around in the blood
→ the liver and muscles take up a lot of the glucose molecules

Question 10

where is insulin secreted from?

Answer 10

→ pancreas secretes a hormone known as insulin into the bloodstream

Question 11

what do glucose molecules combine to form?

Answer 11

glycogen which is a long term storage form of glucose

Question 12

where is the high concentration of blood glucose detected?

Answer 12

→ this increase is detected in the pancreas

Question 13

what is the negative feedback for a decreased concentration in blood glucose concentration?

Answer 13

→ when we skip a meal and blood glucose levels are low
→ the pancreas detects the low concentration of blood glucose
→ secretes glucagon into the bloodstream
→ glucagon travels around the body and binds to lots of different cells, mainly liver cells
→ liver cells take the glycogen and break it down into lots of glucose molecules
→ the liver release glucose molecules into the blood
→ brings blood glucose concentration back to normal
→ all cells have a good supply of glucose needed for respiration

Question 14

what is the hormone secreted when blood glucose concentration decreases?

Answer 14

glucagon

Question 15

what does glucagon do?

Answer 15

→ glucagon travels around the body and binds to lots of different cells, mainly liver cells
→ liver cells take the glycogen and break it down into lots of glucose molecules
→ the liver release glucose molecules into the blood
→ brings blood glucose concentration back to normal

Question 16

where is glucagon secreted from?

Answer 16

the pancreas

Question 17

what is thermoregulation?

Answer 17

is the control of our internal body temperature

Question 18

what is the thermoregulation centre?

Answer 18

A part of the hypothalamus in the brain

Acts as a thermostat for our body

Question 19

how is changes detected in our body temp?

Answer 19

To help it we have receptors around our body which detects changes in body temp. Most of the receptors are found in the skin or blood vessels.

Question 20

what are mechanisms our body uses to warm up?

Answer 20

→ conserve heat and generate more

• -> To conserve heat
  - Constrict our blood vessels that lie near the surface of our skin (vasoconstriction)
  
  • This means less blood flows near surface so less heat energy is lost to the cool environment
  • Contract erector muscles which makes our hairs stand on end
  • This traps a small layer of insulating air
  • Harder to lose heat from skin and helps keep ups warm
• -> To generate more heat
  - We shiver
  - Muscles contract automatically
  - Requires a lot of energy for respiration
  - Results in a lot of heat energy being released as waste
  - Warms the body up

Question 21

what are mechanisms our body uses to cool down?

Answer 21

• Erector muscles relax and allow hairs to fall flat
• Blood vessels expand (vasodilate)
  - More heat energy to be transferred to surroundings
  - Warm blood is passing close to skin surface
• Produce sweat
  - Mixture of water and salt released to surface of skin
  - As sweat evaporates, it takes heat energy from our body along with it
  - Because it requires a lot of energy to evaporate water
  - Heat is lost and leaves us cooler