Year 9 Science Revision: Homeostasis, Disease & Chemistry

Comprehensive vocabulary flashcards covering Homeostasis and Body Systems, Disease and Immunity, and Materials and Chemistry for Year 9 Science revision.

Homeostasis

The process of keeping the body's internal environment stable, even when external conditions change.

Stimulus

A change in the environment, such as touching something hot, that can trigger a response.

Receptor

A sensory structure that detects a change or stimulus.

Control centre

The central processing component, such as the central nervous system (CNS), that processes information and coordinates a response.

Effector

A muscle or gland that carries out the action in response to a stimulus.

Response

The body's reaction to a stimulus, such as pulling a hand away from heat.

Nervous system

A body system that sends fast electrical impulses in neurons to produce short-lived effects.

Endocrine system

A body system that releases hormones carried in the blood to produce generally slower, longer-lasting effects.

Central nervous system (CNS)

The brain and spinal cord, which process information and coordinate responses.

Peripheral nervous system (PNS)

The network of nerves outside the central nervous system that carries messages between the CNS and the rest of the body.

Autonomic nervous system

A division of the nervous system that controls involuntary actions such as heart rate, digestion, and breathing regulation.

Multiple sclerosis (MS)

A disease that damages the myelin sheath around nerve fibres in the central nervous system, slowing or disrupting nerve signals.

Myelin sheath

An insulating layer surrounding nerve fibres in the central nervous system that facilitates rapid nerve signal transmission.

Negative feedback

A feedback mechanism that reverses a change to help restore normal conditions, such as sweating to cool the body.

Positive feedback

A feedback mechanism that reinforces a change until a process is completed, such as blood clotting.

Infectious disease

A disease caused by pathogens that can spread through routes such as air, contact, food, or water.

Non-infectious disease

A disease that is not spread from person to person as an infection, such as many forms of cancer.

Pathogen

An organism or infectious agent that causes disease.

Virus

A non-living infectious agent that requires host cells to reproduce and cannot be treated with antibiotics.

Bacteria

Living, single-celled organisms that can be helpful or cause disease, some of which can be treated with antibiotics.

Phagocytosis

The process by which certain white blood cells engulf and digest pathogens.

Antibodies

Proteins produced by the immune system that recognise and bind to specific antigens.

Antigens

Specific structures that the immune system can recognise as targets.

Memory cells

Immune cells that help the body respond faster if the same pathogen returns.

Vaccine

A substance that exposes the immune system to a harmless form or part of a pathogen, or instructions to make an antigen, training it to fight future infections.

Proton

A subatomic particle located in the nucleus with a positive ($+$) charge.

Neutron

A subatomic particle located in the nucleus with a neutral ($0$) charge.

Electron

A subatomic particle located outside the nucleus in shells or energy levels with a negative ($-$) charge.

Atomic number

The total number of protons found in the nucleus of an atom.

Mass number

The combined total number of protons and neutrons in the nucleus of an atom.

Ion

An atom or group of atoms that has acquired an electrical charge by gaining or losing electrons.

Cation

A positively charged ion formed when an atom loses one or more electrons.

Anion

A negatively charged ion formed when an atom gains one or more electrons.

Ionic bond

A chemical bond formed by the transfer of electrons between atoms, resulting in electrostatic attraction between oppositely charged ions.

Covalent bond

A chemical bond formed when non-metal atoms share pairs of electrons.

Metallic bond

A chemical bond consisting of positive metal ions surrounded by a sea of delocalised electrons.

Organic chemistry

The branch of chemistry that studies carbon-containing compounds.

Hydrocarbon

A chemical compound composed entirely of carbon ($\text{C}$) and hydrogen ($\text{H}$) atoms.

Fractional distillation

A separation method that separates crude oil into fractions based on differing boiling points and condensation heights in a fractionating column.

Complete combustion

A reaction occurring in an abundant supply of oxygen, producing carbon dioxide and water ($\text{Fuel} + \text{oxygen} \rightarrow \text{carbon dioxide} + \text{water}$).

Incomplete combustion

A reaction occurring in limited oxygen that can produce poisonous carbon monoxide, soot (carbon), and water ($\text{Fuel} + \text{limited oxygen} \rightarrow \text{carbon monoxide and/or carbon} + \text{water}$).

Monomer

A small molecule that can chemically bond with other similar molecules to form a larger polymer chain.

Polymer

A large molecule composed of many repeating monomer units linked together.

HDPE (High-Density Polyethylene)

A polymer with relatively straight chains that pack closely together, resulting in higher density, rigidity, and strength.

LDPE (Low-Density Polyethylene)

A polymer with branched chains that prevent close packing, resulting in lower density and greater flexibility.