SB7 - Animal Coordianation, Control and Homeostasis

Question 1

What are the differences between a nervous response and a hormonal response?

Answer 1

Nervous responses are quicker and last for less time. They use electrical impulses which travel along nerves to carry the message. Hormonal responses are slower and they last for longer. They use hormones in the bloodstream to carry their message.

Question 2

What is the endocrine system?

Answer 2

The endocrine system consists of a series of glands which secrete hormones. It is a control system.

Question 3

Where is the pituitary gland?

Answer 3

At the base of the brain, near the hypothalamus.

Question 4

What hormones are secreted by the pituitary gland and what are their functions?

Answer 4

• ADH (TO kidneys) - controls blood water level by triggering uptake of water in the kidneys
• FSH (TO ovaries) - triggers egg maturation in the ovaries
• LH (TO ovaries) - triggers ovulation

Question 5

Where is the pancreas?

Answer 5

In the abdomen, below the stomach.

Question 6

What hormones are secreted by the pancreas and what do they do?

Answer 6

• insulin (TO liver) - allows glucose to be absorbed by body cells
• glucagon (TO liver) - converts glycogen into glucose, which is released into the bloodstream

Question 7

Where is the thyroid gland?

Answer 7

In the neck (on both sides of the trachea)

Question 8

What hormones are secreted by the thyroid gland and what do they do?

Answer 8

• thyroxine (TO most tissues) - controls the rate of metabolism

Question 9

Where are the adrenal glands?

Answer 9

There is one on top of each kidney.

Question 10

What hormones are secreted by the adrenal glands and what do they do?

Answer 10

• adrenaline (TO vital organs e.g. heart, liver) - prepared body for action by increasing heart rate and blood sugar level

Question 11

Where are the ovaries?

Answer 11

At the end of the oviduct in the woman’s reproductive system.

Question 12

What hormones are secreted by the ovaries and what do they do?

Answer 12

• oestrogen (TO uterus) - thickens uterus lining and inhibits FSH (only one egg is matured), stimulates LH (to cause ovulation)
• progesterone (TO uterus) - maintains the lining of the uterus and inhibits FSH and LH

Question 13

Where are the testes?

Answer 13

They are in the scrotum, external to the main body.

Question 14

What hormones are secreted by the testes and what do they do?

Answer 14

• testosterone (TO reproductive organs and the rest of the body) - triggers male secondary sexual characteristics, preparing for reproduction

Question 15

What is the metabolic rate?

Answer 15

The rate at which energy stored in your food is transferred by all the reactions that take place in your body to keep you alive.

Question 16

What is negative feedback?

Answer 16

A method of control in which an increase in one hormone causes its inhibition. For example, high levels of thyroxine cause TRH and TSH to be inhibited, which in turn inhibits thyroxine.

Question 17

How is metabolic rate controlled?

Answer 17

Thyroxine controls metabolic rate. If the levels of thyroxine are too low, metabolism will be too slow. The hypothalamus detects low levels of thyroxine and stimulates the release of TRH from the hypothalamus. Higher levels of TRH are detected by the pituitary, which stimulates the release of TSH from the pituitary. This stimulates the thyroid gland to release more thyroxine, increasing the levels of thyroxine in the blood and the metabolic rate. The opposite happens for too much thyroxine.

Question 18

When is adrenalin released?

Answer 18

Adrenalin is released from the adrenal glands in times of fear, stress or excitement. It causes the ‘fight or flight’ response which prepares the body to face the danger.

Question 19

What is the effect of adrenalin on the liver?

Answer 19

Liver cells break down glycogen into glucose, which is released into the bloodstream. This provides additional glucose for respiration.

Question 20

What is the effect of adrenalin on the heart?

Answer 20

Heart muscles contract:
- more rapidly, which increases the heart rate
- more strongly, which increases the blood pressure

Question 21

What is the effect of adrenalin on the blood vessels?

Answer 21

• diameter of blood vessels leading to muscles widens (vasodilation), which increases blood flow to the muscles
• diameter of blood vessels leading to other organs (e.g. stomach) decreases (vasoconstriction), which reduces blood flow to those organs and increases blood pressure

Question 22

Describe the menstrual cycle.

Answer 22

28 day cycle occurring in females. Days 1-5 = menstruation. Day 14 = ovulation. Uterus lining thickens from around day 6 to day 28.

Question 23

Explain how hormones control the menstrual cycle.

Answer 23

• FSH released by pituitary gland
• FSH stimulates the growth of a follicle (the egg matures). The follicle secretes oestrogen, which thickens the uterus lining. Low levels of oestrogen have a negative feedback effect on FSH to ensure that only one egg is matured per cycle.
• oestrogen levels rise as the follicle grows. High levels of oestrogen stimulate FSH to ensure the egg is fully ready before ovulation, and then LH, which is released by the pituitary gland to cause ovulation
• after ovulation, a sack called a corpus luteum is left, which secretes progesterone
• progesterone maintains the uterus lining and at high concentrations, it inhibits FSH and LH
• the corpus luteum degenerates over time, causing progesterone levels to drop
• this triggers menstruation (unless pregnancy occurs, which causes progesterone levels to remain high)

Question 24

What are some methods of contraception?

Answer 24

Hormonal:
- contraceptive implant
- contraceptive patch
- contraceptive injection
- combined pill
- progesterone only pill

Barrier:
- condom
- intrauterine device (IUD)
- diaphragm/cap
- sterilisation
- natural family planning

Question 25

How do barrier methods work?

Answer 25

Prevent sperm from reaching the egg so fertilisation cannot occur. They usually protect against pregnancy and STDs.

Question 26

How do hormonal methods work?

Answer 26

They alter the concentrations of just progesterone or progesterone and oestrogen to thicken the cervical mucus (prevents sperm entering the uterus) and inhibiting FSH and LH to ensure that no eggs are matured or released.

Question 27

What is Assisted Reproductive Technology (ART)?

Answer 27

The use of hormones and other techniques to increase the chance of pregnancy.

Question 28

What is clomifene therapy?

Answer 28

Clomifene is a drug that helps increase FSH and LH concentration. It is used in females who rarely or never release an egg during their menstrual cycles.

Question 29

When is IVF (in vitro fertilisation) used?

Answer 29

IVF overcomes problems such as blocked oviducts or if a man has few viable sperm cells. IVF can also be used to screen embryos for genetic diseases and only implant those that would be healthy.

Question 30

How does IVF work?

Answer 30

1. Women are given clomifene therapy (FSH first, then LH) so that many eggs mature and are released. A tube is fed up into the Fallopian tube to collect the eggs.
2. The man gives a sample of sperm into a Petri dish
3. The sperm and egg cells are placed into a Petri dish and they fertilise to become zygotes. The zygotes divide by mitosis and some (1-2) are implanted into the uterus.

Question 31

What happens if blood glucose levels are too high?

Answer 31

High blood glucose may be caused by eating lots of sugary food or food high in carbohydrates. The food is broken down in the small intestine and glucose is released into the bloodstream. High levels of glucose in the blood are bad because this can cause damage to organs. The pancreas detects the high blood glucose and secretes insulin. The insulin travels through the bloodstream to the liver, which allows cells to take in glucose from the blood and store it as glycogen. This reduces blood glucose levels.

Question 32

What happens if blood glucose levels are too low?

Answer 32

Low blood glucose may be caused by high intensity exercise or not eating for a long period of time. The pancreas detects the low blood glucose levels and secretes glucagon, which travels through the bloodstream to the liver. This causes stored glycogen to be broken down into glucose which is released into the bloodstream. This increases blood glucose levels.

Question 33

What are the symptoms of diabetes?

Answer 33

• having to pee a lot
• being very thirsty
• losing weight
• getting infections (particularly thrush)
• slow healing wounds

Question 34

Describe type 1 diabetes (cause, risk factors, treatment)

Answer 34

Cause - autoimmune response, body destroys cells in the pancreas that produce insulin
Risk factors - has genetic links
Treatment - injections of insulin before eating, limiting simple carbohydrates and having regular meal times

Question 35

Describe type 2 diabetes (cause, risk factors, treatment)

Answer 35

Cause - either the insulin produced has no effect on the target organs or the pancreas doesn’t make enough insulin
Risk factors - results from lifestyle, being obese, caused by poor diet and/or lack of exercise, often occurs at 35+
Treatments - eating healthily and having a balanced diet, exercise to remove excess glucose from the bloodstream, medications to reduce glucose concentration, medication to increase organ sensitivity to insulin

Question 36

What is homeostasis?

Answer 36

Maintaining constant internal conditions for the optimal conditions for cellular reactions.

Question 37

Why do humans need to thermoregulate?

Answer 37

We need to keep our body temperature constant because of our enzymes. If our body temperature gets too cold, the enzyme rate of reaction decreases quickly. If our body temperature gets too hot, the enzymes denature (active site changes shape - enzyme no longer works). Human body temperature is around 37 degrees Celsius.

Question 38

What part of the body detects temperature changes?

Answer 38

Hypothalamus in the brain

Question 39

What happens if you get too cold?

Answer 39

• shivering (muscles contract and relax rapidly), some energy released in respiration due to shivering warms you up
• contraction of the erector muscles in the dermis of the skin causes body hairs to stand upright (traps air next to the skin for insulation)
• reduction of blood flow near the skin (vasoconstriction) keeps warm blood deeper inside the body, which reduces the rate of transfer of energy to the air by heating

Question 40

What happens if you get too hot?

Answer 40

• sweating - the sweat spreads out as a thin layer over the skin epidermis, where it evaporates. As sweat evaporates it transfers energy to the surroundings by heating, so the skin cools down.
• increased blood flow near the surface of the skin (vasodilation), makes it easier for the blood to transfer energy to the air, so we cool down

Question 41

What is osmoregulation?

Answer 41

The control of the balance of water and mineral salts in the body.

Question 42

What is the function of the urinary system?

Answer 42

To remove excess amounts of some substances from the blood, including water and mineral salts. It also removes waste products like urea.

Question 43

How is urea produced and why does it need to be removed?

Answer 43

Urea is produced in the liver from the breakdown of amino acids that are in greater amounts than needed. Urea is toxic to the body, so it must be removed from the blood.

Question 44

What is the structure of the human urinary system and what does each organ do?

Answer 44

• renal arteries carry blood from the body to the kidneys
• renal veins carry blood with wastes removed back to the body
• kidneys remove substances from the blood and make urine
• ureters carry urine from the kidneys to the bladder
• the bladder stores urine
• urine flows through the urethra to the outside of the body.

Question 45

What causes kidney stones?

Answer 45

• high salt and minerals in your diet lead to stones precipitating out
• extremely painful
• have to be excreted from the body in the urine

Question 46

What are some possible form of renal damage/failure?

Answer 46

• the kidney is no longer able to filter the blood effectively
• plasma not properly reabsorbed
• proteins and cells pass through Bowman’s capsule

Question 47

How does dialysis work?

Answer 47

• blood is taken from the vein containing waste products
• the blood enters the dialysis machine
• dialysis fluid is pumped into the machine throughout treatment. It contains no urea as this causes the urea in the blood to diffuse into the dialysis fluid (across the semi-permeable membrane which separates them). The fluid contains glucose in the same concentration as in the blood, so glucose will not diffuse out of the blood as it is needed for respiration.
• the blood leaves the dialysis machine containing little or no waste
• blood is put back in the same vein you took it from

Question 48

Advantages of dialysis

Answer 48

• no need for immunosuppressant medications
• available to all patients (no shortage)

Question 49

Disadvantages of dialysis

Answer 49

• regular dialysis sessions (multiple lasting a few hours each week) - impacts on the patient’s lifestyle
• expensive for the NHS
• patients must limit their salt and protein intake in between sessions

Question 50

How does a kidney transplant work?

Answer 50

The patient undergoes an operation to replace their damaged kidney with another person’s working one.

Question 51

Kidney transplant advantages

Answer 51

• patients can lead a more normal life without having to watch what they eat and drink
• cheaper for the NHS overall

Question 52

Kidney transplant disadvantages

Answer 52

• shortage of organ donors
• new kidney only lasts 8-9 years on average
• operation carries risks (infection, surgical mistake)
• must take immune suppressant drugs to reduce the chance of rejection, which increase the chance of infections
• kidney cells have antigens, so cells in the immune system may recognise and attack the kidney (rejection)

Question 53

How is blood filtered in the kidney?

Answer 53

• blood flows through a network of capillaries called a glomerulus (sits inside the Bowman’s capsule of a nephron)
• the Bowman’s capsule and glomerulus are adapted to let very small molecules (e.g. water, urea, glucose) through but large molecules (e.g. patients, blood cells) stay in the blood (filtration)
• the filtrate flows along the nephron. Selective reabsorption of useful substances the body needs occurs here (glucose, mineral ions). These substances are pumped through the proteins in the cell membrane in the first convoluted tubule by active transport
• water is reabsorbed by osmosis, depending on how much the body needs (this occurs in the loop of Henle and in the collecting duct)
• the remaining fluid flows into the ureter (known as urine)

Question 54

How is the nephron adapted for the reabsorption of substances?

Answer 54

• large surface area between nephron and capillaries
• cell membrane of cells lining the first convoluted tubule have tiny fold called microvilli, which increase the surface area : volume ratio of the cells
• cells that have protein pumps in their cell membranes contain many mitochondria

Question 55

What does ADH do?

Answer 55

ADH (anti-diuretic hormone) increases the permeability of the collecting duct, allowing for more water to be selectively reabsorbed, making the urine more concentrated. ADH present = small volume of concentrated urine (brown colour). No ADH present = large volume of dilute urine (yellow/clear colour). When there is plenty of water in the blood, the pituitary gland stops releasing ADH.