Glossary

adipocytes

Lipid storage cells.

ATP

Coenzyme found in all lifeforms, that is important for metabolism as an energy molecule.

axon

Specialised extension of a neuron that conducts electrical impulses away from the neuron’s cell body towards other neurons or effector cells, such as other neurons, muscles or glands.

cell membrane

An antagonist is a molecule that blocks or inhibits the action of an agonist at a receptor, preventing a biological response.

circadian rhythm

Internal perception of the daily cycle of light and dark based on retinal activity related to sunlight.

chronic

Health condition or disease that persists over a long period of time.

chronotype

Behavioural manifestation of an individual’s internal body clock, or circadian rhythm. It essentially categorises a person’s natural inclination toward being more active and alert at certain times of the day.

control centre

Component of a feedback system that compares values to the normal range. Deviations cause the activation of an effector.

effector

Component of a feedback system that stimulates a change and returns feedback value to the normal range.

endocrine

System of glands and hormones that regulate many of the body’s key functions by releasing hormones directly into the bloodstream. The endocrine system is vital for maintaining homeostasis and orchestrating complex physiological processes throughout the body.

glucose

Simple sugar (monosaccharide) that is an important energy source in living organisms and is a component of many carbohydrates.

homeostasis

Steady state of body systems that living organisms maintain.

homeostatic

Steady state of body systems that living organisms maintain.

hormone

Secretion of an endocrine organ that travels via the bloodstream or lymphatics to induce a response in target cells or tissues in another part of the body.

jet lag

Mismatch between internal circadian cycles and the environment that result in several symptoms.

melatonin

Important hormone in the regulation of sleep-wake cycles.

negative feedback

Homeostatic mechanism that tends to stabilise an upset in the body’s physiological condition by preventing an excessive response to a stimulus, typically as the stimulus is removed.

photoreceptive

Ability to detect or respond to light.

positive feedback

Mechanism that intensifies a change in the body’s physiological condition in response to a stimulus.

receptor

Protein molecule that contains a binding site for another specific molecule (called a ligand).

rotating shift work

Work schedule with frequent changes from early to late on a daily or weekly basis.

SCN

Located in the anterior hypothalamus, regulates most circadian cycles in the body.

sensor

Biological structure that detects and responds to changes in the environment or within the organism itself.

set point

Ideal value for a physiological parameter; the level or small range within which a physiological parameter such as blood pressure is stable and optimally healthful, that is, within its parameters of homeostasis.

sleep debt

Insufficient sleep on a chronic basis accumulates a sleep debt which results in decreased levels of alertness and mental efficiency.

sleep regulation

The brain’s control of switching between sleep and wakefulness in coordination of this cycle with the outside world.

stimulus

An event in the external or internal environment that registers as activity in a sensory neuron.

suprachiasmatic nucleus (SCN)

Located in the anterior hypothalamus, regulates most circadian cycles in the body.