Unit 2: Maintaining the Internal Environment Revision Sheet

Vocabulary flashcards covering Topic 1 (Homeostasis: thermoregulation and osmoregulation) and Topic 2 (Infectious disease and epidemiology) from the 11BIO Unit 2 revision sheet.

Motor Neuron

A specialized cell of the nervous system consisting of dendrites, a soma, a nucleus, an axon, myelin sheath, nodes of Ranvier, Schwann cells, and axon terminals.

Stimulus

A change in the internal or external environment, such as an increase in body temperature or blood glucose concentration.

Receptor

A sensory cell or structure that detects environmental changes, such as thermoreceptors in skin/hypothalamus or beta cells in the pancreas.

Control Centre

A body structure, such as the hypothalamus or pancreas, that processes sensory input and determines the appropriate response.

Effector

An organ, gland, or cell that carries out a physiological response, such as sweat glands or insulin-secreting beta cells.

Response

An action that counteracts the original stimulus, returning conditions back to their homeostatic set point.

Chemoreceptor

A sensory receptor that detects chemical changes.

Thermoreceptor

A sensory receptor that detects temperature changes.

Mechanoreceptor

A sensory receptor that responds to mechanical forces such as pressure, stretch, and vibration.

Photoreceptor

A sensory receptor that responds to light stimuli.

Nociceptor

A sensory receptor that detects painful stimuli.

Depolarisation

The initial phase of an action potential along an axon caused by sodium ions rushing into the cell.

Repolarisation

The phase of an action potential where potassium ions exit the cell to restore membrane potential.

Sodium–Potassium Pump

A transport mechanism that restores and maintains the resting potential of a neuron following an action potential.

Synaptic Transmission

The process where an action potential triggers vesicles to release neurotransmitters into the synaptic cleft, which diffuse across and bind to receptors on the postsynaptic membrane.

Kleptothermy

A behavioural thermoregulation strategy where organisms conserve body heat by huddling together.

Vasodilation

A physiological mechanism where blood vessels dilate to increase surface blood flow and promote heat loss.

Vasoconstriction

A physiological mechanism where blood vessels constrict to reduce surface blood flow and reduce heat loss.

ADH Osmoregulation Feedback Loop

A homeostatic feedback mechanism where low blood water content causes increased ADH release by the brain, leading to high water reabsorption in the kidneys and low, concentrated urine output.

Stomata

Microscopic structures on plant leaves that control water loss and facilitate gas exchange.

Vacuole

A plant cell organelle responsible for maintaining turgor pressure.

Cuticle

A waxy outer layer on plant leaves that reduces water evaporation.

Abscisic Acid (ABA)

A plant hormone that signals stomata to close during drought conditions to prevent water loss.

Stomatal Density

The concentration of stomata per unit area on a leaf, which is higher in rainforest plants (B) than in desert plants (A) to maximize gas exchange efficiency where water is abundant.

Prion

A pathogen consisting of misfolded protein that causes normal proteins to also misfold.

Virus

A non-cellular pathogen that requires a host cell to replicate.

Bacteria

Prokaryotic pathogens that reproduce rapidly and may cause disease by releasing toxins.

Fungi

Eukaryotic pathogens that spread via spores and can secrete digestive enzymes.

Protist

A single-celled eukaryotic pathogen, some of which are parasitic.

Parasite

An organism that lives in or on a host organism and derives nutrients at the host's expense.

Adherence Factors

Virulence factors that help pathogens attach to host tissue.

Invasion Factors

Virulence factors that allow pathogens to gain entry into host cells.

Capsules

Protective outer structures on pathogens that shield them from host immune attacks.

Toxins

Harmful substances produced by pathogens that cause damage to host cells.

MHC Markers

Antigens present on host cells that allow immune cells to distinguish self from non-self.

First Line of Defence

Non-specific external physical and chemical barriers, such as skin and mucous membranes, that prevent entry of pathogens.

Second Line of Defence

Non-specific internal immune responses, including phagocytes, inflammation, and fever.

Third Line of Defence

Specific adaptive immune responses involving B cells (producing antibodies) and T cells.

Histamines

Chemical compounds released during an immune response that cause vasodilation.

Phagocytes

Immune cells, such as macrophages and neutrophils, that engulf and digest pathogens.

Cytotoxic T Cells

Specialized immune cells that identify and destroy infected body cells.

Active, Naturally Acquired Immunity

Immunity acquired through natural infection with a pathogen followed by recovery.

Active, Artificially Acquired Immunity

Immunity stimulated through exposure to antigens via vaccination.

Passive, Naturally Acquired Immunity

Immunity acquired by receiving antibodies naturally from mother via placenta or breast milk.

Passive, Artificially Acquired Immunity

Immunity conferred by direct injection of pre-formed antibodies or antiserum.

Zone of Inhibition

The clear area surrounding an antimicrobial treatment disc on a bacterial agar plate, where larger zone size indicates higher effectiveness at inhibiting microbial growth.

Herd Immunity

A form of indirect protection from infectious disease that occurs when a sufficiently high proportion of the population (e.g., $80\%$) is immune.

Quarantine

A control strategy that isolates infected or exposed individuals, acting as the most effective method for completely stopping disease spread.

Contact Tracing

The process of identifying and isolating potential disease cases early to prevent further transmission.