Year 9 Science: Body Systems, Coordination, and Disease

Vocabulary practice flashcards providing comprehensive coverage of human nervous and endocrine coordination, sensory physiology, homeostatic regulation, and infectious versus non-infectious diseases from the Year 9 science curriculum.

Central Nervous System (CNS)

The control center of the body comprising the brain and spinal cord, responsible for processing sensory information and directing responses.

Peripheral Nervous System (PNS)

The network of sensory receptors and nerves outside the brain and spinal cord that detects stimuli and carries impulses between the CNS and the rest of the body.

Somatic Nervous System

The division of the peripheral nervous system that communicates with sense organs and coordinates voluntary skeletal muscle movements.

Autonomic Nervous System

The division of the peripheral nervous system that controls involuntary, automatic activities such as heart rate, digestion, respiration, salivation, and sweating.

Sympathetic Nervous System

The branch of the autonomic nervous system that triggers the arousing 'fight or flight' response, increasing heart rate, dilating pupils, and inhibiting digestion.

Parasympathetic Nervous System

The branch of the autonomic nervous system that initiates calming 'rest and digest' actions, slowing heart rate, constricting pupils, and stimulating digestion.

Neuron

The specialised basic cellular unit of the nervous system adapted to generate and transmit electrochemical nerve impulses.

Dendrite

A highly branched thread extending from a neuron's cell body that receives incoming information from other cells and conveys it toward the cell body.

Axon

A long, thin nerve fiber that carries electrical impulses away from the neuron cell body toward other neurons or effector cells.

Myelin Sheath

A white fatty insulating layer encasing an axon that prevents signal dissipation and accelerates nerve impulse conduction to speeds between $1\,m/s$ and $100\,m/s$.

Sensory Neuron

A type of afferent neuron located in the peripheral nervous system that detects internal or external stimuli and transmits sensory impulses toward the central nervous system.

Interneuron

A connector or relay neuron found exclusively within the central nervous system (brain and spinal cord) that processes incoming sensory data and relays impulses to motor neurons.

Motor Neuron

An efferent neuron located in the peripheral nervous system that transmits operational instructions from the central nervous system to effectors such as muscles or glands.

Synapse

The junction where a neuron communicates with another cell, consisting of a presynaptic terminal, a microscopic synaptic cleft ($20\text{--}40\,nm$ in chemical synapses), and a postsynaptic membrane.

Neurotransmitter

A chemical messenger released from vesicles at a presynaptic terminal that diffuses across the synaptic gap to bind specific receptors on the postsynaptic membrane.

Serotonin

A neurotransmitter primarily located in the digestive system that regulates mood, social behavior, appetite, and sleep.

Dopamine

A neurotransmitter that regulates movement and emotional responses and mediates the brain's reward pathways; a deficiency of dopamine-producing neurons causes Parkinson's disease.

Cerebrum

The largest portion of the brain, making up approximately $90\%$ of brain mass, responsible for conscious thought, sensory processing, memory, reasoning, and voluntary muscle control.

Cerebellum

The structure at the base of the brain (meaning 'little brain') responsible for balance, posture, and the coordination of complex muscular movements like walking and cycling.

Medulla

The lowest section of the brain stem, directly continuous with the spinal cord, controlling essential automatic functions such as respiration and heartbeat.

Hypothalamus

A small region of the brain that integrates the nervous and endocrine systems by regulating the pituitary gland and maintaining body temperature, heart rate, hunger, thirst, and sleep patterns.

Lobes of the Cerebrum

The four anatomical divisions of each cerebral hemisphere: the frontal lobe (reasoning, movement), parietal lobe (sensation, touch), temporal lobe (hearing, smell), and occipital lobe (vision).

Frontal Lobe

The anterior lobe of the cerebrum involved in planning, reasoning, problem-solving, morality, emotional control, and voluntary motor output, including Broca's motor speech area.

Parietal Lobe

The central lobe of the cerebrum responsible for processing spatial awareness and bodily sensations such as touch, pressure, temperature, and taste.

Temporal Lobe

The lateral lobe of the cerebrum situated near the ears that manages auditory perception, language interpretation (Wernicke's area), and memory.

Occipital Lobe

The posterior lobe of the cerebrum dedicated to receiving and processing visual information such as color, shape, and distance.

Reflex Arc

An automatic, rapid neural pathway that bypasses conscious processing in the brain by transmitting impulses directly through an interneuron in the spinal cord from a sensory neuron to a motor neuron.

Endocrine System

A body-wide communication system of ductless glands that produce and secrete chemical messengers called hormones directly into the bloodstream to regulate bodily processes.

Hormone

A chemical messenger secreted by endocrine glands into the circulatory system that targets specific organs or tissues to alter their activity.

Target Organ

A specific tissue or organ containing cells with distinct receptors whose three-dimensional shape matches a particular hormone like a lock and key.

Peptide Hormone

A water-soluble hormone composed of amino acid chains that cannot pass through lipid cell membranes and instead binds to cell-surface receptors (e.g., insulin, glucagon).

Steroid Hormone

A lipid-soluble hormone synthesized from cholesterol that diffuses directly across cell surface membranes to bind intracellular receptors in the cytoplasm or nucleus (e.g., testosterone, estrogen).

Negative Feedback Mechanism

A homeostatic control loop that maintains biological stability by detecting deviations from a predetermined set point and initiating an effector response that counteracts the initial change.

Pituitary Gland

The 'master gland' located at the base of the brain that secretes regulatory hormones (e.g., TSH, ACTH, GH, ADH) controlling the secretory activities of other endocrine glands.

Insulin

A peptide hormone produced by pancreatic beta cells in response to elevated blood glucose levels, prompting the liver and body cells to absorb glucose and store it as glycogen.

Glucagon

A peptide hormone produced by pancreatic alpha cells in response to declining blood glucose levels, stimulating the liver to convert stored glycogen back into glucose.

Adrenalin

A hormone produced by the adrenal glands that accelerates heartbeat, elevates blood pressure, and stimulates glycogen breakdown during acute 'fight or flight' emergency responses.

Homeostasis

The coordinated maintenance of a relatively stable internal environment (such as blood glucose, water volume, and temperature at $37^{\circ}\text{C}$) within narrow operational ranges.

Photoreceptor

A specialised light-sensitive sensory cell (rod or cone) located in the retina of the eye that converts electromagnetic light energy into electrochemical nerve signals.

Mechanoreceptor

A sensory receptor that detects mechanical forces such as touch, physical pressure, vibrations (sound in the cochlea), and muscular tension.

Chemoreceptor

A sensory neuron specialized to detect dissolved or airborne chemical molecules, found in the taste buds of the tongue and the olfactory epithelium of the nose.

Thermoreceptor

A sensory nerve ending located in the dermis and hypothalamus that monitors changes in internal and ambient temperatures.

Tropism

A directional plant growth response toward or away from an environmental stimulus, controlled by plant hormones such as auxin.

Phototropism

A growth response where plant stems bend toward a light source due to elongation of cells on the darker side stimulated by auxin accumulation.

Thigmotropism

A growth response in plants prompted by physical touch or surface contact, causing structures like vine tendrils to coil around solid supports.

Pathogen

Any disease-causing agent or biological microorganism, including bacteria, viruses, fungi, protozoa, prions, and macroparasites.

Virulence

A metric indicating the severity of disease an infectious agent inflicts on its host as well as the rapidity and ease with which it transmits.

Prion

A non-cellular infectious, misfolded protein molecule lacking nucleic acids that induces normal cellular proteins to misfold upon direct contact, causing fatal neurodegenerative diseases.

First Line of Defence

Non-specific physical and chemical barrier systems (including skin, mucus secretions, tears, cilia, stomach acid, and natural flora) that prevent pathogen entry into internal tissues.

Second Line of Defence

Non-specific innate physiological reactions engaged after barriers are breached, comprising blood clotting, inflammation, fever, and phagocytosis by white blood cells.

Phagocytosis

The mechanism whereby specialised phagocytic leukocytes engulf, ingest, and enzymatically break down foreign pathogens and cellular debris.

Third Line of Defence

A specific adaptive immune response involving B and T lymphocytes that recognize unique antigens, produce targeted antibodies, and generate long-lasting immunological memory.

Antigen

A unique structural molecular marker (usually a surface protein) on a pathogen or foreign substance that is identified by host immune cells as 'non-self'.

Antibody

A Y-shaped defensive protein synthesized by B lymphocytes that binds specifically to a matching antigen, neutralizing the pathogen or facilitating its engulfment by phagocytes.

Vaccine

A biological preparation of dead, attenuated, or fragmented pathogens or inactive toxins introduced to induce acquired active immunity by stimulating antibody and memory cell production without causing disease.

Antibiotic

A medication, such as penicillin, specifically developed to kill or inhibit bacteria (for instance, by degrading bacterial cell walls) without causing damage to host human cells.

Endemic Disease

A disease that is consistently present at a baseline level within a specific geographic area or restricted population group.

Epidemic Disease

A sudden, widespread surge in the occurrence of an infectious disease exceeding normal expectancy within a defined population or community.

Pandemic Disease

An infectious disease epidemic that crosses international boundaries and spreads across multiple countries, continents, or worldwide.

Rickets

A non-infectious nutritional disease in children caused by Vitamin D deficiency, which inhibits bone calcium absorption and leads to structural deformation of leg bones.

Cancer

A non-infectious disease characterized by uncontrolled, abnormal cell proliferation caused by DNA mutations within proto-oncogenes or tumour suppressor genes.

Devil Facial Tumour Disease (DFTD)

A rare, transmissible contagious cancer transmitted among Tasmanian devils through biting, resulting in fatal ulcerating facial tumors and severe population declines.

Phytophthora cinnamomi

An introduced water- and soil-borne fungal-like pathogen causing extensive root rot and dieback across susceptible Australian native plants, including Wollemi pines and waratahs.

CRAAP Framework

An evaluative research methodology used to assess the reliability of secondary sources based on five criteria: Currency, Relevance, Authority, Accuracy, and Purpose.