GCSE Biology, 4.5-Homeostasis and response.

What is meant by ‘homeostasis’. [2 marks]

Maintaining internal condition into optimum for function in response to internal and external exchange.

State 3 things that homeostasis control in the body. [3 marks]

Blood glucose concentration, body temperature, water level.

A person touch an hot object.

Explain how the person reflex. [5 marks]

• Receptor(skin) detect the stimulus.

• Electrical impulses from the receptor along a sensory neurone to the central nervous system.

• Chemical release by synapse and diffuse across to a relay neurone.

• Trigger electrical impulses in a motor neurones.

• Muscle(effector) contract and pull from the heat.

Explain why reflex action is important. [3 marks]

• Does not involve the conscious part of the brain.

• Automatic and rapid.

• Reflex help to protect us from the danger.

Identify the position of the brain structure. [3 mark]

a) Cerebral cortex.

b) Cerebellum.

c) Medulla.

State the function of the following:

i) Cerebral cortex.

ii) Cerebellum.

iii) Medulla.

i) Memory, language and consciousness.

ii) Control our balance and movement.

iii) Control heart rate and breathing rate.

Suggest three reason why studying the brain or treat brain damage is difficult. [2 marks]

• Protected by the skull.

• Extremely complex structure.

• Easy to damage.

Suggest three ways that scientist use to investigate the brain. [3 marks]

• Mapping the region of the brain to particular function by studying patients with brain damage.

• Use MRI scanning.

• Electrically stimulate different part of the brain.

Identify a, b, c, d. [4 marks]

a) Iris.

b) Cornea.

c) Suspensory ligament.

d) Retina.

Identify e, f, g, h. [4 marks]

e) Optic nerve.

f) Sclera.
g) Ciliary muscle.

h) Len.

State the function of the following:

a) Retina.

b) Cornea.

c) Iris.

a) Detect light intensity.

b) Focussing the light rays.

c) Control the size of the pupil.

State the function of the following:

a) Optic nerve.

b) Sclera.
c) Ciliary muscle.

a) Receive electrical impulses.

b) Protect the eye.

c) Work with suspensory ligament to focus on distant or near object.

What is meant by ‘accommodation’. [2 marks]

Changing the shape of the lens to focus on near or distant object.

Describe how the eyes can focus on a near object. [3 marks]

• Ciliary muscle contract.

• Suspensory ligament loosen.

• Lens thicker and refracts light rays more strongly.

Describe how the eyes can focus on a distant object. [3 marks]

• Ciliary muscle relax.

• Suspensory ligaments are pulled tight.

• Lens thinner and only sightly refracts light rays.

Describe how the brain monitors the temperature of the body. [3 marks]

• Skin contain temperature receptors.

• Send electrical impulses down neurone to the thermoregulatory centre.

• Thermoregulator centre contains receptors which are sensitive to the temperature of the blood.

Describe how the body responds if the body temperature is too high. [2 marks]

• Vasodilation (blood vessel wider)

• Sweat produced from sweat gland.

Describe how the body responds if the body temperature is too low. [2 marks]

• Vasoconstriction (blood vessels constrict)

• Shivering.

Identify the name of the endocrine gland of a, b, e.

[3 marks]

a) Master gland.

b) Thyroid gland.

e) Testes.

Identify the name of the endocrine gland of c, d, f.

[3 marks]

c) Adrenal gland.

d) Pancreas.

f) Ovaries.

A person eat a meal that is rich in carbohydrates.

Explain how homeostasis can let person back to regular glucose level. [4 marks]

• Glucose level in blood increase after meal.

• Pancreas detect it and produce insulin.

• Insulin travel around body and trigger body cell to take glucose from blood.

• Or trigger liver and muscle to store excess glucose as glycogen.

What is meant by ‘type 1 diabetes’. [1 mark]

Pancreas cannot produce enough insulin.

What is meant by ‘type 2 diabetes’. [1 mark]

Body cells does not responses to insulin.

A person does not have meal for long time.

Explain how homeostasis can let person back to regular glucose level. [4 marks]

• Glucose level is low after long time of not having meal.

• Pancreas produce glucagon into the blood.

• Glucagon trigger liver to convert glycogen stores back to glucose.

• Release glucose into the blood.

A person does not have meal for long time.

Explain the result of the graph. [3 marks]

• Glucagon produce which cause glucose level rise.

• Insulin produced when glucose level too high cause glucose level fall.

• Negative feedback cycle.

Explain how kidney remove waste product and adjust level of ions and water. [3 marks]

• Blood that contain urea enter through the artery.

• Kidney remove urea, excess ions and water as urine.

• Urine will store in the bladder.

What is meant by ‘selective reabsorption’. [1 mark]

Reabsorbing useful substance that needed for the body.

Explain how the kidney adjust the level of the molecule in the blood. [4 marks]

• Small molecules filtered out from the capillaries.

• Include urea, ions, water and glucose.

• Selective reabsorption happen.

Explain how excess protein remove from the body.

[3 marks]

• Amino acid produces and pass into the blood.

• Liver break down amino acid into ammonia. (Deamination)

• Liver convert ammonia into urea.

• Can be safely excreted by kidney.

A person has low level of water in the blood.

Explain how master gland can let the person back to normal water level in blood. [4 marks]

• ADH produced into the blood.

• Can cause the kidney tubules become more permeable to water.

• More water reabsorb back to the blood.

• Less urine produced.

A person have kidney failure.

Evaluate the use of kidney dialysis and kidney transplant. [6 maks]

• Limited resources of kidney, but not dialysis.

• Frequency treatment and control diet needed for kidney dialysis, but kidney transplant can lead to normal drug.

• Both treatment are expensive.

What is the function of follicle stimulating hormone (FSH). [1 mark]

Cause an egg to mature in ovary.

What is the function of luteinising hormone (LH).

[1 mark]

Cause an egg to be release.

Oestrogen and progesterone work together.

What are their function. [2 marks]

Maintaining the uterus lining, incase the egg is fertilised and implant.

Describe and explain the process of menstrual cycle. [6 marks]

Your answer should refer to hormones.

• Master gland release follicle stimulating hormone (FSH) which cause an egg to mature in ovaries.

• FSH trigger the ovaries to make oestrogen.

• Oestrogen can cause uterus lining thicker and stop FSH to be released.

• Master gland produce luteinising hormone (LH) and trigger ovulation.

• Progesterone produced to stop FSH and LH to be released to prevent more egg to be mature, and keeps uterus lining thick in case of fertilisation.

• If fertilisation does not take place, uterus lining and the eggs released due to low level of progesterone.

State 5 ways to prevent pregnancy. [5 marks]

Contraceptive pills, injection of progesterone hormone, use of condom, intrauterine device and sterilisation.

Describe how hormone are used to treat infertility.

[3 marks]

• Inject follicle stimulating hormone (FSH) and luteinising hormone.

• Cause woman ovulate more than usual.

• Increase chance of pregnant through sexual intercourse.

Suggest 3 possible problem of using IVF to treat infertility. [3 marks]

Low success rate, Stressful to parents and physically demanding on the mother.

Describe 2 effects of adrenaline in the body. [2 marks]

Increase the heart rate and respiration.

Describe 2 effects of thyroxine in the body. [2 marks]

Increase rate of metabolism and growth

Concentration of substance Q is controlled by negative feedback.

Explain how concentration of substance Q is control by negative feedback. [3 marks]

• if concentration of substance Q becomes too high, hormone is released to reduce it.

• if concentration of substance Q becomes too low, hormone is released to increase it.

• Hormones will bring substance Q to optimal level as constant as possible.

Describe how plant use hormone to response light. [3 marks]

• Auxin is produced at the shoot of the plant.

• Auxin concentrated at the darker side of the shoot and spread out.

• Cell on darker side grow faster and grow toward the light.

Describe how plant use hormone to response gravity. [3 marks]

• Auxin is produced in the root.

• Gravity cause auxin to concentrated the lower side.

• Lower side grow more slower than upper side and grow toward force of gravity.

Describe the function of gibberellin in plant.

[1 mark]

Germination of seeds.

Describe the function of ethene in plant.

[1 mark]

Control cell division.

Give 3 uses of auxin. [3 marks]

Weedkiller, rooting powders and tissue culture.

Give 3 uses of gibberellin. [3 marks]

Germinate earlier, encourage plant to flower and grow larger fruit.