SB7 - Animal Coordination, Control and Homeostasis ✓

Question 1

SB7a - What are hormones?

Answer 1

• Hormones are chemical messengers (carried in the blood stream).
• They are used in the hormonal response system which is typically slow-acting and long-lasting compared to the nervous system

Question 2

SB7a - Where are hormones released? (Give examples)

Answer 2

Endocrine glands e.g:

• Pituitary gland
• Thyroid gland
• Adrenals
• Ovaries
• Testes
• Pancreas

Question 3

SB7a - Where do hormones go to? (Give examples)

Answer 3

Target organs e.g:

• Digestive system
• Kidneys
• Liver
• Endocrine glands for other hormones (e.g growth hormone)

Question 4

SB7b - Define homeostasis

Answer 4

Maintaining constant conditions in the body, typically through negative feedback

Question 5

SB7b - How do you measure resting metabolic rate?

Answer 5

• At a warm room
• Body at rest
• Long after the person has had a meal

Question 6

SB7b - How does your body’s fight or flight system work?

• Describe the target organs of adrenaline in your answer

Answer 6

• Adrenaline is released from adrenal glands and is always in the bloodstream at a low level
• A fight or flight situation will cause increased impulses from neurons which will trigger the release of large amounts of adrenaline into your blood
• Adrenaline has many target organs:
  
  • Causes the breakdown of glycogen to glucose in the liver so that there is more for cellular respiration (more energy)
  • Heart contracts more rapidly and strongly increasing the heart rate and blood pressure. This moves glucose around the body quicker
  • Diameter of blood vessels leading to muscles or target organs are widened to allow more blood through while the rest are narrowed to allow more to be sent to the widened vessels

Question 7

SB7b - How is thyroxine used as part of a negative feedback system?

Answer 7

• If the concentration of thyroxine in the blood is low, the hypothalamus may release TRH
• This will cause the pituitary gland to release TSH
• This stimulates the thyroid gland to release thyroxine, increasing the concentration of thyroxine

Question 8

SB7b - What is a negative feedback system?

Answer 8

A response to an increase in one condition by causing actions that will decrease it, or vice versa (e.g response to body being too hot is to sweat to cool it down)

Question 9

SB7b - What is thyroxine?

Answer 9

• Thyroxine is a hormone that is released by the thyroid gland.
• It’s target organs are many different types of cells of which it will increase the rate at which protein and carbohydrates are broken down.
• This affects your metabolic rate

Question 10

SB7b - What is your metabolic rate?

Answer 10

The overall rate at which chemical reactions occur within the body

Question 11

SB7c - Describe the stages of the menstrual cycle

Answer 11

• Days 1-5ish: Menstruation is when the lining of the uterus breaks down and is lost with an unfertilised egg
• Days 10-12ish: The uterus lining starts to thicken again
• Days 13-15: The new egg is released from the ovary
• Days 16-28: Uterus lining continues to thicken
• Day 23ish: The egg cell travels along the oviduct to the uterus

Question 12

SB7c - How do hormone based contraceptions work?

Answer 12

• Release progesterone and oestrogen-like hormones to inhibit the production of LH and FSH, therefore preventing an egg cell maturing / ovulation occuring.
• Thickens the mucus at the cervix making it harder for sperm to pass through

Question 13

SB7c - What is contraception?

Answer 13

The prevention of fertilisation. e.g:

• Condom
• Diaphragm or cap
• Hormonal pills / implants

Question 14

SB7c - What is the menstrual cycle?

Answer 14

• The cycle of changes that take place in a women’s reproductive system for about 28 days
• Starts with puberty (around 12) and ends with menopause (around 50)
• Prepares the body for the fertilisation of an egg and pregnancy

Question 15

SB7d - How can problems with conception be overcome?

Answer 15

Using ART (Assisted reproductive technology) (Inc. IVF)

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Question 16

SB7d - What are progesterone and oestrogen?

Answer 16

• Oestrogen: Causes the uterus lining to thicken and stimulates releases of LH
  
  • Highest around day 13
• Progesterone: Inhibits release of LH and FSH
• Both reduce in concentration after the menstruation but stay constant if the egg is fertilised

Question 17

SB7d - What is clomifene therapy?

Answer 17

Used on women who rarely or never release an egg, this uses a drug that increases levels of FSH and LH, this prepares the body for the egg by thickening the lining and stimulates the release of an egg

Question 18

SB7d - What is FSH?

Answer 18

• (Follicle stimulating hormone) is involved in the maturing and growth of the egg follicle
• It is released from the pituitary gland and is inhibited by higher level of progesterone (which is released after the follicle becomes a corpus luteum)
• Highest levels around day 4 and 12

Question 19

SB7d - What is IVF and how does it work?

Answer 19

In vitro fertilisation is when the egg is fertilised in a lab and the embryo is re-inserted into the women’s uterus:

• Egg follicle maturation is stimulated by hormones
• Eggs are released by many follicles and they are taken from the ovary
• Sperm cells are taken from the man
• The egg cells and sperm cells are allowed to combine in a petri dish for fertilisation
• One or two healthy embryos are re-inserted into the uterus

Question 20

SB7d - What is LH?

Answer 20

• (Luteinising hormone) is involved in causing the egg to be release
• It is released from the pituitary gland and is inhibited by higher levels of progesterone but stimulated by higher levels of oestrogen
• Highest levels around day 13 (with oestrogen)

Question 21

SB7e - Describe the travel of glucose through the bloodstream of a non-diabetic person?

Answer 21

• Glucose is released from the small intestine after digestion. As it flows into the bloodstream, the concentration rises
• The pancreas detects the high levels of blood glucose and releases insulin. Now the concentration of insulin also rises
• The insulin causes the liver, muscle and other cells to take up the glucose and store it as glycogen. Thus the glucose and insulin concentration reduces
• Once the glucose concentration is too low, the pancreas releases glucagon.
• This causes all the cell that contain glycogen to convert this back into glucose which is released into the blood
• This is a negative feedback system

Question 22

SB7e - What is type 1 diabetes and how can it be dealt with?

Answer 22

• Pancreatic cells don’t produce insulin as they have been destroyed by the body’s immune system
• This means they cannot control blood glucose levels naturally
• A type 1 diabetic would have to inject insulin into the fat layer below the skin to reduce blood glucose levels
• (Typically non-genetic)

Question 23

SB7f - How do you calculate BMI?

Answer 23

BMI = mass (kg) ÷ height (m²)

Question 24

SB7f - How do you calculate waist:hip ratio?

Answer 24

waist measurement ÷ hip measurement

Question 25

SB7f - What is type 2 diabetes?

Answer 25

• Insulin releasing cells don’t produce enough insulin or target organs don’t respond to insulin
• Can be genetic or due to lifestyle

Question 26

SB7f - Why can being physically active help with type 2 diabetes?

Answer 26

• Physical activity increases cellular respiration that takes place in your body
• This takes up glucose form your blood reducing the need for insulin
• this lowers your blood glucose level

Question 27

SB7f - Why is waist:hip ratio preferred to BMI sometimes?

Answer 27

While both have a correlation with risk of T2 diabetes, BMI doesn’t account for muscle mass.

Question 28

SB7g - How does the brain detect the temperature of the body?

Answer 28

• In the dermis of the skin, there are temperature receptors
• These feed information to the receptors in the hypothalamus in the brain

Question 29

SB7g - What is fever/hypothermia and why is it bad?

Answer 29

• Fever is when your body is above 38°C
• Hypothermia is when your body is below 36°C
• These are bad because the enzymes that enact most of the processes in our body that keep us alive have an optimum temperature of 37°C
• So straying too far from it will stop these processes from occurring (properly) as enzymes can become denatured/ineffective

Question 30

SB7g - What is thermoregulation?

Answer 30

The negative feedback system that ensures our body stays at around 37°C

Question 31

SB7g - When the body is too cold, what will happen?

Answer 31

• Shivering: Muscles rapidly contract and expand. Some of the energy released form cell respiration warms you up
• Vasoconstriction: Nerve signals from the hypothalamus tell the blood vessels near the surface of the skin (in the dermis) will narrow. This reduces thermal energy lost to surroundings as blood flows past
• Erector muscles contract: Erector muscles in the dermis of the skin contract causing hair to stand upright. While it may not work for humans, on other mammals it traps air next t the skin for insulation

Question 32

SB7g - When the body is too warm, what will happen?

Answer 32

• Sweating: Your body secretes a thin layer of sweat on the epidermis of your skin. When this evaporates, it transfers energy from the body to the surroundings
• Vasodilation: Nerve signals from the hypothalamus tell the blood vessels in the dermis widen. As more blood flows near the surface of the skin, more energy is transferred to the surroundings
• Erector muscles relax: Hair lies flat meaning no air can be trapped and reducing the insulation (again it doesn’t make a difference for humans)

Question 33

SB7h - Describe how to urinary system works

Answer 33

• The urinary system removes excess amounts of substances from the blood inc. water mineral salts and urea
• Renal arteries carry blood from the body to the kidney.
• Once it is ‘cleaned’ renal veins carry the blood to the rest of the body
• The kidneys remove excess substances from the blood to form urine
• Ureters carry urine to the bladder where it is stored
• Once the muscle keeping the bladder closed is released, the urine passes through the urethra to outside the body

Question 34

SB7h - How does dialysis work?

Answer 34

• Blood containing waste is taken form the vein and passed through a dialysis machine
• Dialysis machine contains fluid which has the same glucose concentration as blood plasma
• There is a semi-permeable membrane which allows the waste and excess substances to leave the blood through osmosis (due to conc. gradient)
• The same level of glucose on either side of the membrane means there won’t be a net loss/gain
• The ‘cleaned’ blood is sent back to the person’s veins

Question 35

SB7h - What is kidney failure and why is it dangerous?

Answer 35

• Kidney failure is when both of the kidneys stop working properly
• This means that there will be high concentration of waste products in their blood which will need to be removed by dialysis

Question 36

SB7h - What is organ donation and why doesn’t it always work?

Answer 36

Another person’s kidney is used to replace a faulty one. However:

• This takes a lot of surgery and may not be suitable for weaker patients
• Like all cells, the have antigens on them and the recipient’s immune system may attack it. This is called rejection
• Even with a successful organ donation, the patient needs to be on lifelong medication to weaken their immune system making them more susceptible to other infections

Question 37

SB7h - What is osmoregulation?

Answer 37

• The negative feedback system involving the balance of water and minerals in the body.
• The wrong balance will result in cells taking in the wrong amounts through osmosis and being damaged

Question 38

SB7h - What is urea?

Answer 38

Urea is produced from the breakdown of excess amino acids in the liver. This is passed into the blood

Question 39

SB7i - How is the nephron adapted for re-absorption of substances?

Answer 39

1. There is a large surface area of contact between the nephron and capillaries
2. The cell membrane of the cells lining the first convoluted tubule has tiny folds called microvilli. These increase the surface area:volume ratio of the cells.
3. Cells that have protein pumps in their cell membranes contain many mitochondria

Question 40

SB7i - What are nephrons?

Answer 40

Nephrons are tiny microscopic tubes in the kidney where urine is made

Question 41

SB7i - What happens at the collecting duct of the kidney?

Answer 41

• Selective re-absorption
• Some water is reabsorbed depending on how much is needed (ADH dependent)
• The collecting duct takes the filtered fluids from the second convoluted tube to the ureter
• Here it is urine and contains excess water, urea and other substances

Question 42

SB7i - What happens at the first convoluted tubule of the kidney?

Answer 42

• Selective re-absorption
• At the first convoluted tube, glucose and some mineral ions are reabsorbed
• However, if a person is diabetic, not all the glucose will be reabsorbed leaving some in the urine

Question 43

SB7i - What happens at the loop of henle in the kidney?

Answer 43

• Selective re-absorption
• Here, water is selectively reabsorbed depending on how much is needed in the bloodstream
• Some mineral ions are also reabsorbed

Question 44

SB7i - What is ADH and how does it do its job?

Answer 44

• Anti diuretic hormone is used to control the water concentration of urine as it leaves the kidney
• When the pituitary gland detects a low water concentration in the blood it releases ADH
• ADH makes the collecting duct’s walls more permeable allowing more osmosis of water out through it and making the urine more concentrated with urea
• A lack of ADH means the collecting duct’s walls are less permeable. Less water leaves through osmosis and so the urine is more dilute

Question 45

SB7i - What is filtration in the kidney?

Answer 45

• Blood flows through a network of capillaries (glomerulus) in the bowman’s capsule
• Here, the smaller molecules (water urea glucose) move into the nephron while larger particles (protein blood cells) stay
• This is filtration

Question 46

SB7i - What is selective re-absorption?

Answer 46

Using active transport to transfer substances back from the nephron into the bloodstream

Question 47

`SB7f - What is the relationship between T2 diabetes and average body mass?

Answer 47

• The higher your body mass, the higher the risk of T2 diabetes.
• These factors are correlated

Question 48

SB7c - What are the advantages / disadvantages of hormonal methods of contraception?

Answer 48

Advantages

1. 99% effective if used properly
2. Longer-lasting than normal hormonal methods

Disadvantages

1. Hormonal inbalance could cause side effects (mood swings etc)
2. Doesn’t protect against STIs

Question 49

SB7c - What are the advantages / disadvantages of barrier methods of contraception?

Answer 49

Advantages

• Protects against STIs
• Condoms have a high success rate (98%)
• No side effects

Disadvantages

• Potential to split/break
• Lower success rate for diagphragm/cap (92-96%)