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Edexcel GCSE Biology > SB7 - Animal Coordination, Control and Homeostasis ✓ > Flashcards

SB7 - Animal Coordination, Control and Homeostasis ✓ Flashcards

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1
Q

SB7a - What are hormones?

A
  • 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
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2
Q

SB7a - Where are hormones released? (Give examples)

A

Endocrine glands e.g:

  • Pituitary gland
  • Thyroid gland
  • Adrenals
  • Ovaries
  • Testes
  • Pancreas
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3
Q

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

A

Target organs e.g:

  • Digestive system
  • Kidneys
  • Liver
  • Endocrine glands for other hormones (e.g growth hormone)
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4
Q

SB7b - What is your metabolic rate?

A

The rate at which energy stored as food is transferred by all of the reactions that take place in your body

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5
Q

SB7b - How do you measure resting metabolic rate?

A
  • At a warm room
  • Body at rest
  • Long after the person has had a meal
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6
Q

SB7b - What is a negative feedback system?

A

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)

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7
Q

SB7b - Define homeostasis

A

Maintaining constant conditions in the body, typically through negative feedback

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8
Q

SB7b - What is thyroxine?

A
  • 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
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9
Q

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

A
  • 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
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10
Q

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

A
  • 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
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11
Q

SB7g - What is thermoregulation?

A

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

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12
Q

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

A
  • 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
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13
Q

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

A
  • In the dermis of the skin, there are temperature receptors
  • These feed information to the receptors in the hypothalamus in the brain
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14
Q

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

A
  • 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
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15
Q

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

A
  • 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)
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16
Q

SB7h - What is osmoregulation?

A
  • 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
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17
Q

SB7h - Describe how to urinary system works

A
  • 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
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18
Q

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

A
  • 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
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19
Q

SB7h - What is urea?

A

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

20
Q

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

A
  • 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
21
Q

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

A
  • 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)
22
Q

SB7f - What is type 2 diabetes?

A
  • Insulin releasing cells don’t produce enough insulin or target organs don’t respond to insulin
  • Can be genetic or due to lifestyle
23
Q

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

A
  • 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
24
Q

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

A
  • The higher your body mass, the higher the risk of T2 diabetes.
  • These factors are correlated
25
Q

SB7f - How do you calculate BMI?

A

BMI = mass (kg) ÷ height (m²)

26
Q

SB7f - How do you calculate waist:hip ratio?

A

waist measurement ÷ hip measurement

27
Q

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

A

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

28
Q

SB7c - What is the menstrual cycle?

A
  • 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
29
Q

SB7c - Describe the stages of the menstrual cycle

A
  • 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
30
Q

SB7d - What is FSH?

A
  • (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
31
Q

SB7d - What is LH?

A
  • (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)
32
Q

SB7d - What are progesterone and oestrogen?

A
  • 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
33
Q

SB7c - How do hormone based contraceptions work?

A
  • Release progesterone and oestrogen-like hormones to ‘trick’ the body into thinking the egg is fertilised (due to no drop in concentration after day 28) and stops ovulation
  • Thickens the mucus at the cervix making it harder for sperm to pass through
34
Q

SB7c - What is contraception?

A

The prevention of fertilisation. e.g:

  • Condom
  • Diaphragm or cap
  • Hormonal pills / implants
35
Q

SB7d - How can problems with conception be overcome?

A

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

Friggin art students, this is what they’re doing

36
Q

SB7d - What is clomifene therapy?

A

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

37
Q

SB7d - What is IVF and how does it work?

A

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
38
Q

SB7h - How does dialysis work?

A
  • 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
39
Q

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

A

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
40
Q

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

A
  • 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
41
Q

SB7i - What are nephrons?

A

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

42
Q

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

A
  • Protein pumps containing mitochondria providing energy for active transport
  • large surface area of contact between nephron and capillaries (convoluted tubes) and…
  • micorvilli on the first convoluted tube. These increase surface area:volume ratio increasing rate of osmosis
43
Q

SB7i - What is filtration in the kidney?

A
  • 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
44
Q

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

A
  • 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
45
Q

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

A
  • Selective re-absorption
  • Here, water is selectively reabsorbed depending on how much is needed in the bloodstream
  • Some mineral ions are also reabsorbed
46
Q

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

A
  • Selective re-absorption
  • Some water is reabsorbed depending on how much is needed (ADH dependent)
  • The collecting duct takes the filtered fluids along from the filtered fluids from the second convoluted tube to the ureter
  • Here it is urine and contains excess water, urea and other substances
47
Q

SB7i - What is selective re-absorption?

A

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

Edexcel GCSE Biology (11 decks)

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