D3.3 Homeostasis, Blood-Glucose Control & Thermoregulation

40 vocabulary flashcards summarise key terms and definitions on homeostasis, negative feedback, glucose regulation, diabetes, thermoregulation and hormonal control in humans.

Homeostasis

The ability of an organism to maintain a constant internal environment at preset values despite external fluctuations.

Homeostatic Variable

A physiological factor, such as body temperature, blood pH, blood glucose or blood osmotic concentration, kept within narrow limits.

Set Point

The preset or target value around which a homeostatic variable is regulated.

Negative Feedback

A control mechanism that counteracts deviations of a variable from its set point, returning it to normal values.

Positive Feedback

A control mechanism that amplifies the initial change, moving the system further from its starting state; rare in homeostasis.

Feedback Loop

A biological circuit that uses information about the outcome of a process to adjust the process itself.

Blood Glucose Concentration

The amount of glucose in the blood, normally ~90 mg per 100 mL in humans.

Hyperglycaemia

Condition of abnormally high blood glucose levels; can raise blood pressure and damage tissues.

Hypoglycaemia

Condition of abnormally low blood glucose levels, impairing cellular energy supply.

Pancreas

A gland with both exocrine and endocrine functions; its islets of Langerhans regulate blood glucose via insulin and glucagon.

Islets of Langerhans

Clusters of endocrine cells in the pancreas that secrete insulin (β cells) and glucagon (α cells).

Insulin

Hormone released by pancreatic β cells that lowers blood glucose by promoting uptake into cells and glycogen synthesis.

Glucagon

Hormone released by pancreatic α cells that raises blood glucose by stimulating glycogen breakdown and gluconeogenesis in the liver.

Endocrine Gland

A gland that secretes its products (hormones) directly into the bloodstream.

Exocrine Gland

A gland that releases its products via ducts to specific sites, e.g., digestive enzymes or sweat.

Type 1 Diabetes

Early-onset autoimmune disorder destroying β cells, leading to little or no insulin production.

Type 2 Diabetes

Late-onset disorder involving reduced insulin sensitivity or receptor deficiency, often linked to obesity and inactivity.

Glucose Tolerance Test

Diagnostic test measuring how quickly ingested glucose is cleared from the blood, revealing diabetic conditions.

Peripheral Thermoreceptors

Temperature-sensitive nerve endings in the skin that detect external temperature changes.

Central Thermoreceptors

Receptors in the core and hypothalamus that monitor internal body temperature.

Hypothalamus

Brain region that integrates thermal information and initiates responses to maintain core temperature.

Thermoregulatory Centre

Portion of the hypothalamus that sets the body’s temperature set point and coordinates effectors.

Thyrotropin-Releasing Hormone (TRH)

Hormone from the hypothalamus that stimulates the pituitary to release TSH.

Thyroid-Stimulating Hormone (TSH)

Pituitary hormone that triggers the thyroid gland to secrete thyroxin.

Thyroxin (T4)

Thyroid hormone that increases metabolic rate and heat production in target tissues.

Vasodilation

Widening of blood vessels near the skin surface to increase heat loss by radiation and convection.

Vasoconstriction

Narrowing of superficial blood vessels to reduce heat loss by keeping warm blood deeper in the body.

Sweating

Evaporative cooling mechanism in which sweat absorbs heat as it changes from liquid to vapour.

Shivering

Involuntary skeletal-muscle contractions that generate metabolic heat when body temperature falls.

Brown Adipose Tissue

Fat tissue rich in mitochondria that produces heat via uncoupled respiration, especially in infants.

Uncoupled Respiration

Metabolic process in brown fat where proton motive force generates heat instead of ATP.

Effectors (in Homeostasis)

Organs or tissues (e.g., muscles, glands) that carry out responses restoring a variable to its set point.

Receptors (in Homeostasis)

Cells or proteins that detect changes in homeostatic variables and send signals to control centres.

Hormone

Chemical messenger secreted into the blood that affects the physiology of distant target cells.

Blood Osmotic Concentration

Total solute concentration in blood plasma that influences water balance.

Blood pH

Measure of acidity/alkalinity of blood; maintained close to 7.4 by buffering systems and ventilation.

Blood Pressure (Arterial)

Force exerted by circulating blood on arterial walls; regulated to ensure tissue perfusion.

Muscle Tissue (as Effector)

Target tissue that can generate heat through shivering or increase metabolic heat production.

Adipose Tissue (as Effector)

Insulating tissue that reduces heat loss; brown fat additionally produces heat.

Behavioural Thermoregulation

Voluntary actions (e.g., seeking shade, removing clothing) that aid in maintaining body temperature.

Metabolic Rate

Overall speed of chemical reactions in the body; modulation influences heat output.