SACE Stage 2 Biology – Homeostasis Video Notes

Vocabulary flashcards covering hormones, nervous vs endocrine control, thermoregulation, stress physiology and CO₂/pH regulation from the video lecture notes.

Erector Pili Muscles

Small muscles attached to hair follicles that contract to raise hairs, trapping insulating air (goosebumps).

Shivering

Rapid involuntary skeletal-muscle contractions that generate heat in response to low body temperature.

Sweating

Release of fluid from sweat glands; evaporation removes heat and cools the body.

Thyroxine

Thyroid hormone that raises metabolic rate and heat production; secretion increases in cold and decreases in heat.

Thermoregulatory Centre

Region of the hypothalamus that monitors blood temperature and coordinates heat-gain or heat-loss responses.

Pre-Capillary Sphincter

Ring of smooth muscle controlling blood entry into capillary beds; constricts in cold, relaxes in heat.

Bronchodilation

Adrenaline-induced widening of bronchial tubes, improving oxygen intake during stress.

Metabolic Rate

Overall rate of energy expenditure; elevated by adrenaline and thyroxine, lowered when cooling is needed.

Immunosuppression

Temporary reduction in immune activity caused by stress hormones such as cortisol and adrenaline.

Nervous Impulse

Rapid electro-chemical signal traveling along neurons, reaching effectors within milliseconds.

Electro-Chemical Messaging

Mode of neuronal transmission combining electrical impulses along axons with chemical neurotransmitters at synapses.

Endocrine System

Body system of ductless glands producing hormones for long-lasting, widespread regulation.

Specificity (Nervous vs Endocrine)

Nervous signals reach single tissues; hormones typically influence all cells bearing the appropriate receptor.

Duration of Response

Nervous actions are brief; hormonal effects persist minutes to hours or longer.

Respiratory Centre

Brainstem area that regulates breathing; stimulated by falling CSF pH to increase ventilation.

Evolutionary Advantage of Sweating

Whole-body sweat glands enabled humans to dissipate heat and sustain prolonged daytime hunting.

Motor Neuron

Neuron that carries impulses from CNS to effectors such as muscles or glands.

Insulin Inhibition by Adrenaline

Adrenaline suppresses insulin release, preventing glucose uptake and keeping blood sugar high for energy.

Goosebumps

Raised skin bumps resulting from erector pili contraction; vestigial heat-conservation response in humans.

Adrenaline (Epinephrine)

A fast-acting hormone released from the adrenal medulla during the fight-or-flight response that raises heart rate, blood pressure and blood glucose.

Fight-or-Flight Response

A sympathetic nervous system reaction to danger, stress or excitement that prepares the body for rapid action.

Hypothalamus

Brain region that detects internal changes and initiates nervous and hormonal pathways for homeostasis, including thermoregulation and stress responses.

Sympathetic Nervous System

The branch of the autonomic nervous system that stimulates effectors such as the heart and adrenal medulla during stress.

Adrenocorticotropic Hormone (ACTH)

Pituitary hormone that travels in blood to stimulate the adrenal cortex.

Glycogenolysis

Conversion of glycogen to glucose in liver cells, stimulated by adrenaline to elevate blood glucose.