AQA GCSE Biology (Triple) - Homeostasis and Response

These flashcards cover key concepts related to homeostasis and response in AQA GCSE Biology, including the nervous and endocrine systems, reflex actions, hormonal regulation, and kidney function.

What is homeostasis?

The regulation of internal conditions to maintain a stable internal environment.

Give three examples of internal conditions controlled by homeostasis.

Body temperature, blood glucose concentration, and water/ion levels.

What are the three main components of a control system?

Receptors detect stimuli, coordination centres process information.

What is the role of the nervous system?

It enables rapid electrical communication between different parts of the body.

Describe the structure of the nervous system.

It consists of the central nervous system (CNS — brain and spinal cord) and the peripheral nervous system.

What is a reflex action?

A rapid, automatic response to a stimulus that does not involve conscious thought.

Describe the pathway of a reflex arc.

Stimulus → receptor → sensory neurone → relay neurone in the spinal cord → motor neurone.

How is information transmitted across a synapse?

Neurotransmitters diffuse across the synaptic gap, binding to receptors on the next neurone.

What is the function of the endocrine system?

A collection of glands that secrete hormones directly into the bloodstream to regulate bodily functions.

Compare the nervous and endocrine systems.

Nervous system: fast, short-lived, electrical impulses, specific. Endocrine: slower, long-lasting, hormonal effects.

How is blood glucose concentration controlled?

If too high, pancreas releases insulin, glucose moves into cells, converted to glycogen.

Explain the difference between Type 1 and Type 2 diabetes.

Type 1: immune system destroys insulin-producing cells, no insulin made. Type 2: body becomes resistant to insulin.

How is body temperature monitored and controlled?

Thermoregulatory centre in the hypothalamus detects blood temperature and receives input from temperature receptors.

What is negative feedback?

A process that detects a change away from the optimum and triggers a response to return to it.

What is the role of the pituitary gland?

It secretes multiple hormones that control other glands, known as the 'master gland'.

How are hormones involved in the menstrual cycle?

FSH stimulates follicle maturation and oestrogen release; oestrogen rebuilds the uterus lining.

How can hormones be used to treat infertility?

Fertility drugs containing FSH and LH stimulate ovulation; IVF uses these hormones as well.

What are disadvantages of IVF?

Emotionally and physically stressful, low success rates, risk of multiple births, and ethical concerns.

What is adrenaline and what is its function?

A hormone from the adrenal glands that prepares the body for 'fight or flight' by increasing heart rate.

What is thyroxine and how is it regulated?

A hormone from the thyroid gland controlling metabolic rate, growth, and development.

What are the main parts of the brain and their functions?

Cerebral cortex — consciousness, memory, intelligence. Cerebellum — muscle coordination, balance.

How do scientists study the brain?

By observing patients with brain damage, electrically stimulating brain areas, and using imaging techniques.

Describe the structure of the eye.

Key parts: cornea (refracts light), iris (controls pupil size), lens (focuses light), retina (detects light).

How does the eye focus on near and distant objects?

Near: ciliary muscles contract, suspensory ligaments loosen, lens thickens. Distant: ciliary muscles relax.

How does the eye respond to bright and dim light?

Bright light: circular muscles contract, pupil constricts. Dim light: radial muscles contract, pupil dilates.

What is hyperopia and myopia?

Hyperopia (long-sightedness): cannot focus on near objects, corrected with convex lenses. Myopia (short-sightedness): cannot focus on distant objects, corrected with concave lenses.

How does the kidney maintain homeostasis?

By filtering blood, reabsorbing needed substances (e.g., glucose, ions, water), and excreting waste.

How is water balance controlled in the body?

Monitored by the hypothalamus; if blood too concentrated, ADH is released to increase water reabsorption by kidneys.

What treatments exist for kidney failure?

Dialysis (filters blood artificially) or kidney transplant (requires immunosuppressant drugs).