GCSE Biology Unit 2: Animal Physiology

Comprehensive vocabulary flashcards covering gas exchange, human nutrition, digestive enzymes, circulation, blood components, nervous coordination, the eye, endocrinology, homeostatic kidney function, thermoregulation, and human reproduction.

Respiration

The chemical process taking place in cells that releases energy from glucose.

Ventilation

The physical movement of air into and out of the lungs.

Gas Exchange

The diffusion of oxygen and carbon dioxide across a surface between air and blood.

Aerobic Cellular Respiration Equation

$$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy (ATP and heat)}$$

Trachea

The windpipe supported by rings of cartilage that carries air from the throat towards the lungs.

Bronchi

The two main branches that divide from the trachea to carry air into each lung.

Bronchioles

Smaller branching airways inside the lungs that lead from the bronchi to the alveoli.

Alveoli

Tiny microscopic air sacs in the lungs where gas exchange occurs between air and blood.

Goblet Cells

Specialised epithelial cells in the airways that secrete sticky mucus to trap dust and microorganisms.

Cilia

Microscopic hair-like projections on epithelial cells that beat rhythmically to sweep mucus and trapped particles towards the throat.

Inhalation

An active process where external intercostal muscles and the diaphragm contract, flattening the diaphragm and raising ribs, which expands thorax volume and drops internal lung pressure below atmospheric pressure to draw air in.

Exhalation

A predominantly passive process where external intercostal muscles and the diaphragm relax, returning the diaphragm to a dome shape and moving the rib cage down and inward, reducing thorax volume and forcing air out.

Limewater Test

A chemical test for carbon dioxide gas in which a colourless solution of calcium hydroxide turns cloudy or milky.

Chronic Bronchitis

A condition caused by smoke chemicals irritating airway lining and damaging cilia, resulting in excessive mucus production, persistent coughing, and blocked airways.

Emphysema

A progressive disease where alveolar walls break down and air spaces merge, significantly decreasing surface area for gas exchange and causing breathlessness.

Carboxyhaemoglobin

A stable compound formed when carbon monoxide binds tightly to haemoglobin, reducing the blood's capacity to transport oxygen.

Balanced Diet

A diet that provides appropriate proportions of all seven essential nutritional components: carbohydrates, lipids, proteins, vitamins, minerals, water, and dietary fibre.

Glycogen

A large, insoluble branched polysaccharide that serves as the main carbohydrate storage molecule in animal liver and muscle tissues.

Lipids

Molecules composed of a glycerol molecule bonded to three fatty acids that function as long-term energy stores, thermal insulation, and components of cell membranes.

Kwashiorkor

A severe deficiency disease caused by inadequate dietary protein intake, characterised by stunted growth and muscle wasting.

Scurvy

A deficiency disease caused by a lack of vitamin C (ascorbic acid), resulting in impaired collagen synthesis, bleeding gums, and poor wound healing.

Rickets

A bone disease in growing children caused by deficiency of vitamin D or calcium, resulting in soft, poorly mineralised bones.

Dietary Fibre

Indigestible plant matter (cellulose) that adds bulk to food waste, promoting peristalsis and preventing constipation.

Iodine Test

A food test for starch where adding yellow-brown iodine solution produces a blue-black colour if starch is present.

Benedict’s Test

A food test for reducing sugars where heating a sample with blue Benedict's solution in a boiling water bath results in a green, yellow, orange, or brick-red precipitate depending on sugar concentration.

Biuret Test

A biochemical test for protein where adding Biuret reagent changes colour from blue to lilac or purple.

Emulsion Test

A test for lipids where a sample is dissolved in ethanol and mixed with water, forming a cloudy white emulsion if lipids are present.

Mechanical Digestion

The physical breakdown of food into smaller pieces by chewing and stomach churning, increasing the surface area for enzymes without altering chemical bonds.

Chemical Digestion

The enzymatic hydrolysis of large, insoluble food molecules into small, soluble molecules suitable for absorption into the bloodstream.

Amylase

A digestive enzyme secreted by salivary glands and the pancreas that catalyses the hydrolysis of starch into maltose.

Maltase

A brush-border enzyme located on the small intestine lining that breaks down maltose into glucose molecules.

Pepsin

A gastric protease enzyme secreted in the stomach that functions in acidic conditions to digest proteins into peptides.

Lipase

An enzyme produced by the pancreas and active in the small intestine that breaks down lipids into glycerol and fatty acids.

Peristalsis

Involuntary wave-like contractions and relaxations of circular and longitudinal muscles in the gut wall that propel a food bolus through the digestive tract.

Bile

An alkaline fluid produced by the liver and stored in the gall bladder that neutralises acidic stomach chyme and emulsifies fats.

Emulsification

The process by which bile salts break down large fat globules into tiny droplets, increasing the surface area for lipase action.

Intestinal Villus

A finger-like projection of the ileum lining containing a capillary network and a central lacteal that maximises nutrient absorption.

Lacteal

A specialised lymphatic capillary located within the core of an intestinal villus that absorbs digested lipids and fatty acids.

Egestion

The expulsion of undigested, unabsorbed food material from the body as faeces through the anus.

Excretion

The removal from the body of metabolic waste products, toxic substances, and substances in excess of requirements produced by cellular reactions.

Double Circulation

A circulatory system in which blood travels through the heart twice during each complete circuit of the body, split into the pulmonary and systemic circuits.

Atrium

An upper thin-walled chamber of the heart that receives blood returning from the veins.

Ventricle

A lower muscular chamber of the heart that pumps blood out through arteries to the lungs or systemic body tissues.

Aorta

The main artery carrying oxygenated blood under high pressure from the left ventricle to the rest of the body.

Vena Cava

The large vein that delivers deoxygenated blood returning from body tissues into the right atrium of the heart.

Pulmonary Artery

The blood vessel that transports deoxygenated blood away from the right ventricle towards the lungs.

Pulmonary Vein

The blood vessel that carries oxygenated blood from the lungs into the left atrium of the heart.

Coronary Arteries

Blood vessels branching from the base of the aorta that deliver oxygenated blood and nutrients directly to heart muscle tissue.

Coronary Heart Disease (CHD)

A condition in which fatty plaque deposits narrow the lumen of the coronary arteries, restricting blood flow and oxygen delivery to the cardiac muscle.

Artery

A blood vessel with thick muscular, elastic walls and a narrow lumen designed to transport blood away from the heart under high pressure.

Vein

A blood vessel with relatively thin muscular walls, a wide lumen, and internal valves designed to return low-pressure blood back toward the heart.

Capillary

A microscopic, single-cell-thick blood vessel that enables exchange of gases, nutrients, and metabolic wastes between blood and surrounding tissue cells.

Plasma

The pale-yellow liquid fraction of blood, composed mainly of water, that carries dissolved cells, nutrients, hormones, urea, carbon dioxide, and distributes heat.

Red Blood Cell (Erythrocyte)

A biconcave, anucleated blood cell packed with haemoglobin specialised for the transport of oxygen throughout the body.

Phagocyte

A type of white blood cell that defends the body by engulfing and enzymatically digesting foreign pathogens through phagocytosis.

Lymphocyte

A white blood cell that detects foreign antigens and produces specific antibody proteins to target pathogens for destruction.

Platelets

Small cell fragments circulating in blood that initiate blood clotting by producing an insoluble fibrin protein mesh to seal wounds.

Central Nervous System (CNS)

The main coordination centre consisting of the brain and spinal cord that integrates incoming sensory information and dictates responses.

Sensory Neurone

A nerve cell that conducts electrical impulses from sensory receptors towards the central nervous system.

Relay Neurone

A short interneurone situated completely within the central nervous system that links sensory neurones to motor neurones.

Motor Neurone

A neurone that conducts motor nerve impulses from the central nervous system out to effectors, such as muscles or glands.

Reflex Arc

The rapid, involuntary neural pathway mediating an automatic protective reflex: stimulus $\rightarrow$ receptor $\rightarrow$ sensory neurone $\rightarrow$ relay neurone $\rightarrow$ motor neurone $\rightarrow$ effector $\rightarrow$ response.

Synapse

A microscopic junction between two neurones across which chemical neurotransmitters diffuse to transmit an impulse unidirectionally.

Retina

The innermost light-sensitive layer of the eye containing rod and cone receptor cells that transduce light into electrical nerve impulses.

Cornea

The transparent, curved anterior portion of the sclera that refracts light entering the eye.

Iris Reflex

An involuntary protective reflex regulating pupil aperture; circular muscles contract to constrict the pupil in bright light, whereas radial muscles contract to dilate the pupil in dim light.

Accommodation

The physiological mechanism by which the ciliary muscles and suspensory ligaments alter the curvature of the crystalline lens to focus clearly on near or distant objects.

Blind Spot

The specific region of the retina where the optic nerve exits the eyeball, entirely lacking photoreceptors.

Endocrine Gland

A ductless organ that synthesises and secretes hormones directly into circulating bloodstream capillaries.

Hormone

A regulatory chemical messenger produced by an endocrine gland and transported by blood plasma to exert specific effects on target cells.

Adrenaline

A 'fight or flight' hormone released by the adrenal glands during stress or danger that elevates heart rate, breathing rate, and blood glucose availability.

Insulin

A hormone produced by beta cells of the pancreas in response to high blood glucose that stimulates cellular glucose uptake and glycogen synthesis in the liver.

Homeostasis

The maintenance of a relatively stable internal physiological environment within strict limits despite fluctuations in external conditions.

Negative Feedback

A corrective homeostatic control mechanism wherein a deviation from a set physiological level triggers a series of opposite corrective responses to restore the parameter back to its set point.

Nephron

The microscopic structural and functional filtering unit of the kidney responsible for filtering blood and producing urine.

Ultrafiltration

The process by which hydrostatic blood pressure forces water, urea, ions, and glucose from glomerular capillaries across a basement membrane into Bowman's capsule, retaining large proteins and blood cells.

Selective Reabsorption

The active and passive movement of essential filtered solutes, including all glucose, required mineral ions, and water, from the nephron tubule back into peritubular capillaries.

Antidiuretic Hormone (ADH)

A pituitary hormone that increases the water permeability of kidney collecting duct membranes, leading to increased water reabsorption and concentrated urine.

Vasodilation

The widening of arterioles supplying superficial skin capillaries to increase blood flow to the surface and enhance radiative heat loss in warm conditions.

Vasoconstriction

The narrowing of arterioles supplying superficial skin capillaries, diverting blood flow inward away from the skin surface to minimise heat loss in cold conditions.

Zygote

A single diploid cell produced by the fusion of the haploid nucleus of a sperm with that of an ovum during fertilisation.

Placenta

A temporary organ attached to the uterine wall providing exchange of oxygen, glucose, antibodies, and waste products between maternal and fetal blood while keeping circulations separate.

Follicle-Stimulating Hormone (FSH)

A pituitary hormone that stimulates follicle growth in the ovary and induces follicular cells to secrete oestrogen.

Luteinising Hormone (LH)

A pituitary hormone that triggers ovulation and stimulates the formation of the corpus luteum in the ovary.

Progesterone

A female steroid hormone secreted by the corpus luteum that maintains the thickened vascular lining of the uterus during the menstrual cycle and pregnancy.