Biology - Homeostasis (Aqa) - Triple

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What is homeostasis?

The regulation of internal conditions to maintain optimum conditions for function in response to internal and external changes.

Why is homeostasis important?

It maintains optimal conditions for enzyme action and all cell functions.

What does homeostasis control in the human body?

Blood glucose concentration, body temperature, and water levels.

What do automatic control systems involve?

Nervous responses or chemical (hormonal) responses.

What are the three parts of a control system?

Receptors, coordination centres, effectors.

What is the function of receptors?

Detect stimuli (changes in the environment).

What is the role of coordination centres?

Process information from receptors (e.g. brain, spinal cord, pancreas).

What is the role of effectors?

Bring about responses to restore optimum conditions (muscles or glands).

What is the nervous system responsible for?

Reacting to surroundings and coordinating behaviour.

What are neurones?

Cells that carry electrical impulses.

What makes up the central nervous system (CNS)?

The brain and spinal cord.

What is the pathway of nervous responses?

Stimulus → Receptor → Coordinator → Effector → Response

What is a reflex action?

An automatic and rapid response that does not involve the conscious brain.

Why are reflex actions important?

They help protect the body from harm.

Name the three types of neurones involved in a reflex arc.

Sensory neurone, relay neurone, motor neurone.

What happens at a synapse?

Electrical impulses trigger chemicals to diffuse across the gap between neurones.

What is the brain made of?

Billions of interconnected neurones.

What are the three main regions of the brain?

Cerebral cortex, cerebellum, medulla.

What is the function of the cerebral cortex?

Controls consciousness, memory, and language.

What is the function of the cerebellum?

Controls balance and coordination.

What is the function of the medulla?

Controls heart rate and breathing rate.

Why is investigating the brain difficult? (HT)

The brain is delicate, complex, and easily damaged.

How can neuroscientists study the brain? (HT)

Studying patients with brain damage, electrical stimulation, MRI scans.

What type of receptors does the eye contain?

Light receptors (sensitive to light intensity and colour).

What is accommodation?

The process of changing the lens shape to focus on near or distant objects.

How does the eye focus on near objects?

Ciliary muscles contract, suspensory ligaments loosen, lens becomes thicker.

How does the eye focus on distant objects?

Ciliary muscles relax, suspensory ligaments tighten, lens becomes thinner.

What is myopia?

Short-sightedness (distant objects appear blurry).

What is hyperopia?

Long-sightedness (near objects appear blurry).

How is myopia corrected?

Concave lenses.

How is hyperopia corrected?

Convex lenses.

What are two new treatments for eye defects?

Laser surgery and replacement lenses.

What controls body temperature?

The thermoregulatory centre in the brain.

What happens if body temperature is too high?

Vasodilation and sweating.

What happens if body temperature is too low?

Vasoconstriction, shivering, and stopping sweat production.

What is the endocrine system?

A system of glands that secrete hormones into the bloodstream.

How does the endocrine system compare to the nervous system?

Slower but lasts longer.

What is the master gland?

The pituitary gland.

What does the pancreas do?

Controls blood glucose levels by releasing insulin and glucagon.

What happens when blood glucose is too high?

The pancreas releases insulin, which converts glucose into glycogen.

What is Type 1 diabetes?

When the pancreas doesn't produce insulin (treated with insulin injections).

What is Type 2 diabetes?

When body cells don't respond to insulin (treated with diet, exercise, and sometimes medication).

What happens when blood glucose is too low?

The pancreas releases glucagon, which converts glycogen back into glucose.

What is the role of the kidneys?

Remove waste substances and maintain water balance.

How do the kidneys produce urine?

Filtration of blood + selective reabsorption of glucose, ions, and water.

What hormone controls water levels in the body?

ADH from the pituitary gland.

How does ADH work?

It makes the kidney tubules more permeable to water.

What are two treatments for kidney failure?

Dialysis or kidney transplant.

What is the main female reproductive hormone?

Oestrogen.

What is the main male reproductive hormone?

Testosterone.

What hormone causes egg maturation?

FSH (Follicle Stimulating Hormone).

What hormone causes egg release?

LH (Luteinising Hormone).

Which hormones maintain the uterus lining?

Oestrogen and progesterone.

What are the main hormonal contraceptives?

Pills, injections, implants, skin patches.

What are the main non-hormonal contraceptives?

Condoms, diaphragms, IUDs, sterilisation.

What is IVF?

Fertility treatment involving egg collection, fertilisation in the lab, and embryo transfer to the uterus.

What are the problems with IVF?

Emotionally and physically stressful, expensive, low success rates, multiple births.

What hormone controls the fight-or-flight response?

Adrenaline from the adrenal glands.

What hormone controls metabolic rate?

Thyroxine from the thyroid gland.

What is negative feedback?

A process where changes are reversed to maintain a steady state.

What plant hormone controls growth responses to light and gravity?

Auxin.

What plant hormone triggers seed germination?

Gibberellins.

What plant hormone controls fruit ripening?

Ethene.

How are auxins used by farmers?

Weed killers, rooting powders, tissue culture.

How is ethene used in the food industry?

To control fruit ripening during storage and transport.