Biology GCSE OCR Notes – Topic 3: Organism Level Systems (Vocabulary Flashcards)

Vocabulary flashcards covering nervous system structure and function, the eye, brain components, hormones and the endocrine system, reproductive hormones and the menstrual cycle, contraception and fertility, plant hormones and tropisms, homeostasis and temperature regulation, blood glucose control and diabetes, and kidney/osmoregulation concepts.

Central nervous system (CNS)

The brain and spinal cord; coordinates responses to stimuli and processes information from receptors.

Receptor cells

Cells that detect a stimulus and convert it into an electrical impulse.

Sensory neuron

Nerve cell that carries impulses from receptors to the CNS.

Relay neuron

Neuron in the CNS that connects sensory and motor neurons.

Motor neuron

Nerve cell that carries impulses from the CNS to effectors.

Effector

Muscle or gland that carries out a response.

Reflex arc

A rapid, subconscious pathway of response to a stimulus that often bypasses conscious brain processing.

Thermoreceptors

Receptors that detect temperature changes (e.g., in the skin).

Cornea

Transparent outer part of the eye that refracts light toward the retina.

Iris

Coloured part of the eye that controls light entry by altering pupil size.

Conjunctiva

Membrane that covers the front of the eye and lines the eyelids.

Pupil

Opening in the centre of the iris; size controlled by circular and radial muscles to regulate light entry.

Lens

Transparent, biconvex disc that focuses light onto the retina; attached to ciliary muscles by suspensory ligaments.

Retina

Layer containing light receptors (rods and cones) that detects light.

Rods

Light receptors that respond to dim light, enabling night vision.

Cones

Light receptors that respond to colour and enable day vision.

Optic nerve

Carries impulses from the retina to the brain.

Fovea

Part of the retina with the highest visual acuity.

Colour blindness

Inherited inability to distinguish certain colours, most commonly red-green.

Myopia (short-sightedness)

Difficulties seeing distant objects because the lens focuses light in front of the retina; corrected with concave lenses.

Hyperopia (long-sightedness)

Difficulties seeing near objects because the lens focuses light behind the retina; corrected with convex lenses.

Cerebrum

Largest brain region; responsible for intelligence, memory, personality; two hemispheres; grey outside, white inside.

Cerebellum

Brain region that coordinates voluntary movements and balance.

Medulla

Brain region that controls heart rate, blood pressure and breathing rate.

Hypothalamus

Brain region that regulates temperature and water balance via the hormonal system.

Pituitary gland

Master gland that releases hormones (e.g., growth hormone) into the blood.

Grey matter

Outer brain layer composed mainly of nerve cell bodies.

White matter

Inner brain tissue composed mainly of myelinated nerve fibres.

Endocrine system

Glands and hormones that coordinate body processes via the bloodstream.

Hormones

Chemical messengers secreted by endocrine glands into the bloodstream to act on target organs.

Adrenaline

Hormone from adrenal glands; prepares body for 'fight or flight' (increases heart rate, dilates pupils, speeds breathing).

Thyroxine

Hormone from the thyroid; controls metabolic rate and growth.

Negative feedback

Regulatory mechanism where a change is reversed to maintain homeostasis (e.g., thyroxine levels regulated via TRH and TSH).

Testosterone

Male sex hormone produced by the testes; involved in sperm development and secondary sexual characteristics.

Oestrogen (estrogen)

Female sex hormone produced by the ovaries; involved in secondary sexual characteristics and the menstrual cycle.

Menstrual cycle

Approximately 28-day cycle with hormonal changes; ovulation around day 14; preparation of the uterus for possible implantation.

FSH (follicle-stimulating hormone)

Hormone that stimulates egg maturation in the ovary and promotes estrogen production.

LH (luteinising hormone)

Hormone that triggers ovulation and formation of the corpus luteum.

Progesterone

Hormone that maintains the uterine lining after ovulation and inhibits LH/FSH.

Menopause

End of a woman's regular menstrual cycles, typically around ages 50–55.

Oral contraceptive pill

Hormonal contraception—contains oestrogen and progesterone; inhibits FSH to prevent egg maturation; >99% effective with correct use.

Contraceptive implants

Slow-release progesterone implants; thickens cervical mucus and may prevent ovulation; long-lasting and highly effective.

Condoms

Barrier contraception; protects against STIs; effectiveness varies with correct use.

Vasectomy

Surgical removal or sealing of sperm-carrying ducts; highly effective and usually permanent.

Copper IUD (coil)

Intrauterine device containing copper; prevents implantation; up to 10 years; >99% effective; possible ectopic pregnancy risk.

Abstinence

Choosing not to have sexual intercourse as a method of contraception.

IVF (in vitro fertilisation)

Fertilisation of eggs with sperm in a laboratory; embryos implanted into uterus; often assisted by FSH/LH for egg maturation.

Auxins

Plant hormones that promote growth; move to shaded side to cause bending toward light; influence tropisms.

Gibberellins

Plant hormones that stimulate seed germination, flowering, and fruit size; can end seed dormancy.

Ethene (ethylene)

Plant hormone involved in fruit ripening and certain growth processes; used in the food industry to control ripening.

Phototropism

Growth response of a plant toward light (often mediated by auxins).

Gravitropism (geotropism)

Growth response of a plant to gravity (roots grow toward gravity; shoots away from gravity).

Auxin uses in horticulture

Used as weed killers, rooting powders, and in tissue culture to promote growth or rooting.

Maintaining internal environments (homeostasis)

Keeping a constant internal environment for optimal enzyme function and cell processes.

Thermoregulatory centre

Brain region that monitors body temperature via receptors in the blood and skin.

Normal body temperature

Approximately 37.5°C as stated in the notes.

Sweating

Evaporation of sweat from skin increases energy transfer from body to environment, cooling the body.

Vasodilation

Wider blood vessels near the skin surface to increase heat loss.

Vasoconstriction

Narrowing of blood vessels to reduce heat loss.

Shivering

Rapid muscle contractions to generate heat when body temperature falls.

Blood glucose regulation

Maintenance of blood glucose levels by the pancreas through insulin and glucagon.

Insulin

Hormone that promotes glucose uptake into muscle and liver cells and glycogen formation; lowers blood glucose.

Glucagon

Hormone that stimulates glycogen breakdown to glucose in the liver; raises blood glucose.

Diabetes Type 1

Pancreas cannot produce enough insulin; high blood glucose; glucose in urine; treated with insulin.

Diabetes Type 2

Body cells no longer respond well to insulin; linked to obesity; managed with diet, exercise and sometimes medication.

Osmoregulation

Maintenance of water balance and solute concentrations in the body.

ADH (antidiuretic hormone)

Hormone from the pituitary that increases kidney tubule permeability to water, promoting water reabsorption and concentrated urine.

Kidneys (functional role)

Filter blood to remove waste; reabsorb useful substances like glucose, ions and water; produce urine.

Nephron

Functional unit of the kidney where filtration, reabsorption and urine formation occur.

Glomerulus

A knot of capillaries inside the nephron where filtration occurs.

Distal convoluted tubule and collecting duct

Parts of the nephron where selective reabsorption and water reabsorption (via ADH) occur.

Cortex and Medulla of kidney

Outer (cortex) and inner (medulla) regions of the kidney; contain nephron structures.

Ureter

Tube carrying urine from the kidneys to the bladder.

Renal artery and renal vein

Blood supply to and from the kidney.

Water potential

Measure of the potential energy of water in a system; drives osmosis across membranes.