AQA Biology GCSE Topic 5: Homeostasis and Response Flashcards

Flashcards for AQA Biology GCSE Topic 5: Homeostasis and Response, covering key concepts and definitions from the lecture notes.

What is homeostasis?

The maintenance of a constant internal environment, needed for enzyme action and cell functions.

Name three things homeostasis controls in the human body.

Blood glucose concentration, body temperature, and water levels.

What are the three components of all control systems?

Receptors, coordination centers, and effectors.

What do receptors do?

Detect stimuli (changes in the environment).

Give three examples of coordination centers.

Brain, spinal cord, and pancreas.

What do effectors do?

Bring about responses to bring the conditions in the body back to optimum levels (e.g., muscles or glands).

What type of cells convert a stimulus into an electrical impulse?

Receptor cells

What type of neuron carries electrical impulses to the central nervous system (CNS)?

Sensory neurons

What type of neuron carries electrical impulses from the CNS to effectors?

Motor neurons

What are reflexes?

Automatic responses that take place before you have time to think. They prevent the individual from getting hurt.

What is a reflex arc?

The pathway information travels down for vital responses to take place quickly, without going through the conscious brain.

What happens at a synapse?

A chemical is released into the synapse that diffuses across to trigger an impulse in the next neuron.

What is the cerebral cortex responsible for?

Controls consciousness, intelligence, memory and language.

What is the cerebellum responsible for?

Controls fine movement of muscles.

What is the medulla responsible for?

Controls unconscious actions such as breathing and heart rate.

Name three methods neuroscientists use to map brain regions.

Studying patients with brain damage, electrically stimulating parts of the brain, and using MRI scanning techniques.

What is the function of the retina?

Layer of light sensitive cells that stimulate impulses to the brain to create an image.

What is the function of the optic nerve?

A nerve that carries impulses from the retina to the brain to create an image.

What is the function of the sclera?

White outer layer which supports the structures inside the eye.

What is the function of the cornea?

See through layer that allows light through and bends and focuses light onto the retina.

What is the function of the iris?

Muscles that surround the pupil and contract or relax to alter the size of the pupil.

What is the function of the ciliary muscles and suspensory ligaments?

Hold the lens in place and control its shape.

What happens to the ciliary muscles and suspensory ligaments when focusing on a near object?

Ciliary muscles contract and suspensory ligaments loosen.

What happens to the ciliary muscles and suspensory ligaments when focusing on a distant object?

Ciliary Muscles relax and suspensory ligaments tighten.

What is myopia?

Short sightedness, where the lens is too curved.

What is hyperopia?

Long sightedness, where the lens is too flat.

How can myopia and hyperopia be treated?

Spectacle lenses, contact lenses, laser eye surgery, and replacement lens.

Where is the thermoregulatory center found?

In the brain.

List three responses if body temperature becomes too high.

Sweat is produced, vasodilation occurs, and hairs lie flat.

List four responses if body temperature decreases too much.

Sweating stops, skeletal muscles shiver, hairs stand on end, and vasoconstriction occurs.

What are the main glands in the human endocrine system, and what hormones do they secrete?

Pituitary (various), Pancreas (insulin, glucagon), Thyroid (thyroxine), Adrenal (adrenaline), Ovary (oestrogen), Testes (testosterone).

How does the hormonal system compare to the nervous system?

The hormonal system is much slower but acts for longer.

What does insulin do when blood glucose levels are too high?

Binds to cells, causing glucose to move from the blood into muscle cells and excess glucose to be converted into glycogen.

What does glucagon do when glucose levels decrease?

Binds to liver cells, causing glycogen to be broken down into glucose which is released into the blood.

How does the body maintain constant blood glucose concentration?

Through using hormones like insulin and glucagon, in a negative feedback loop.

What is type 1 diabetes?

The pancreas cannot produce enough insulin.

How is type 1 diabetes treated?

With insulin injections at meal times, and limiting intake of simple carbohydrates.

What is type 2 diabetes?

The body cells no longer respond to insulin.

List three treatments for type 2 diabetes.

Reducing simple carbohydrates, losing weight, and increasing exercise.

What happens when the water concentration of the blood increases?

Cells in the body take up water via osmosis and expand.

What happens when the water concentration of the blood decreases?

Cells in the body lose water via osmosis and shrink.

Name three examples of waste products processed at the kidney.

Water, ions, and urea.

How does ADH affect water loss as urine?

Increased ADH increases the tubules' permeability to water, so more moves back into the bloodstream, resulting in less and more concentrated urine.

List three problems associated with dialysis.

Possibility of blood clots forming, the amount of time it takes, having to follow a strict diet, and the build up of waste products in between sessions.

Name a main problem associated with kidney transplants.

Kidneys could be rejected from the body as a result of the immune system recognizing antigens on the donor organ.

What is the main male reproductive hormone?

Testosterone, produced by the testes to stimulate sperm production.

What is the main female reproductive hormone?

Oestrogen, produced in the ovary.

Name the four hormones in the menstrual cycle.

Follicle stimulating hormone (FSH), Oestrogen, Luteinising hormone (LH), and Progesterone.

What does FSH do?

Causes the maturation of an egg in the ovary, within a structure called a follicle.

What does oestrogen do?

Causes the lining of the uterus to grow again. Stimulates LH and inhibits FSH.

What does LH do?

Its release results in ovulation.

What does progesterone do?

Maintains the lining of the uterus, and supports a pregnancy. Inhibits the release of both FSH and LH.

How does the mixed contraceptive pill work?

The oestrogen levels are constantly high, inhibiting FSH so no eggs mature, the lining also stops developing and the mucus in the cervix becomes thick so sperm cannot move through

What is the function of spermicides?

Chemicals that kill or disable sperm.

What is the purpose of fertility drugs?

To increase the chance of pregnancy by stimulating the maturation and release of the egg.

What does thyroxine regulate?

Metabolic rate (how quickly reactions occur). It is also important in growth and development.

Name three effects of adrenaline.

Increased heart rate and breathing rate, glycogen stored in liver is converted to glucose, pupils dilate, blood flow to muscles is increased, and blood flow to the digestive system is decreased.

What is phototropism?

The response to light.

What is gravitropism or geotropism?

The response to gravity.

What does auxin do in shoots?

Stimulates cells to grow more.

What do gibberellins do?

Important to stimulate seed germination.

What hormone is involved in cell division and the ripening of fruits?

Ethene