B3.3 - Maintaining internal environments

Question 1

Normal body temperature and the effects of change in temperature.

Answer 1

• Enzymes in the human body work best at 37 degrees Celsius.
• Regio of 40-42 degrees Celsius your enzymes may denature and body reactions stop so you may die.
• Below 37 degrees Celcius causes reactions to happer slower, cells don’t get enough energy and die. Risk of hypothermia.

Question 2

How is body temperature controlled?

Answer 2

• Thermoregulatory centre in your brain (hypothalamus) is responsible for controlling body temp.
• External temp. information from your skin receptors and internal temp. information from your blood receptors is sent via impulse, if there is a change in temperature a response will occur in the dermis (deep layer of skin).

Question 3

How does your body respond to being hot?

Answer 3

• Hairs flatten so insulating layer of air is not present
• Sweat glands release sweat, as sweat evaporates it transfers energy by heating from your body to the environment reducing your temperature.
• VASODILATION - blood vessels near the surface of skin widen (dilate) increasing blood flow through capillaries transferring heat to the surroundings by radiation cooling you down.

Question 4

How does your body respond to being too cold?

Answer 4

• Body hairs raise to trap an insulating layer of air to keep to you warm.
• Little sweat
• VASOCONSTRICTION - blood vessels near skin surface narrow (constrict), less blood flow near surface and less energy transferred.
• You shiver (muscles contract and relax), makes your cells respire quicker transferring extra energy keeping you warm.

Question 5

What is the importance of keeping blood sugar levels constant?

Answer 5

Eat > blood sugar levels increase > if maintained damages nerves and blood vessels as excess glucose is stored as fat.
Excercise > blood sugar levels drop > prevent cells from respiring effectively.

Question 6

What does insulin do?

Answer 6

• You eat, blood sugar levels are too high.
• Pancreas releases insulin to stimulate the liver to convert glucose into glycogen to be stored in the liver so the blood sugar levels drop.

Question 7

What does glucagon do?

Answer 7

• If you excercise and your blood sugar levels drop as you need the glucose for energy, the pancreas releases glucagon.
• Glucagon makes the liver change glycogen back into glucose to use and return the blood sugar levels to normal.

Question 8

What is Type 1 diabetes?

Answer 8

• Usually occurs in children, cannot produce insulin.
• Their immune system has destroyed the pancreatic cells that make insulin.
• Controlled by regular injections of insulin at meal times to stop the blood sugar levels from getting too high, limiting the amount of simple carbohydrates (high glycaemic index and taking regular excercise.

Question 9

What is Type 2 diabetes?

Answer 9

• Cannot effectively use insulin, body cells do not respond to insulin.
• Occurs later in life and is caused by obesity
• Controlled by drugs to improve how cells respond, healthy diet, excercise and weight loss.

Question 10

Why should water levels in blood plasma levels stay constant?

Answer 10

• If there is too much water they will enter your blood cells and they will swell and burst (lysis).
• Cells shrink as water diffuses out of your cell if there isn’t enough water.

Question 11

Explain the process of ultrafiltration in the kidney.

Answer 11

• Blood flows in at high pressure from the renal artery through the glomerulus (knot of capillaries) where ultrafiltration occurs.
• Water, salts, urea and glucose are forced out of the capillary wall and into the bowmans capsule.
• Proteins and blood cells are too big so remain in the blood stream.

Question 12

Explain the process of selective reabsorption.

Answer 12

Filtrate moves through the nephron tubule:

• All glucose is absorbed
• Appropriate amounts of water and salts are reasbsorbed.

Question 13

What happen at the loop of Henle and beyond?

Answer 13

The loop of Henle is where more salt and water regulation occurs.
- The rest of the filtrate (waste solution:urine) collects at the collecting duct and travels to the bladder.

Question 14

How does the body control the volume of urine produced? What happens if the blood water concentration is too high/low?

Answer 14

ADH: Makes the walls of the collecting duct more permeable to water so more water is reabsorbed into the blood.

• If blood water potential is too low: ADH is secreted from the pituitary gland. More water is reabsored to make the water levels back to normal.
• If blood water potential is too high: Less ADH is secreted so the water is lost and larger volume of urine.

Question 15

Define hypertonic, hypotonic and isotonic.

Answer 15

Hypertonic - high levels of glucose and salts
Hypotonic - low levels of glucose and salst
Isotonic - ion concentration equal to those in blood plasma.