Homeostasis and Physiology: Adapting to Challenges

Vocabulary-style flashcards covering the definitions of homeostasis, regulatory feedback mechanisms, glucose regulation, and the physiological responses to stress as presented in the lecture notes.

Physiology

The study of functions and mechanisms in living systems, derived from the Ancient Greek words for origin (physis) and study (logia).

Homeostasis

The maintenance of a stable internal environment despite changes to external conditions, as defined by Claude Bernard (1865) and Walter B Cannon (1932).

Milieu interieur

The concept of maintaining a stable internal environment, introduced by Claude Bernard in 1865.

Set point

The 'normal' condition or value that a self-regulating system attempts to maintain through coordinated responses.

Adaptation

A shift from the set point where function is maintained, allowing the organism to adjust to changes.

Pathology

A sustained upset in the physiological balance that results in dysfunction.

Homeostatic Sensor

The component of a regulatory system that detects changes in a variable and sends information to an integrator.

Normal Blood Glucose Level

The homeostatic level of glucose in the blood, which is approximately $90\,mg/100\,ml$.

Insulin

A hormone from the pancreas that stimulates glucose uptake by cells and the formation of glycogen in the liver when blood glucose levels rise.

Glucagon

A hormone from the pancreas that stimulates the breakdown of glycogen into glucose when blood glucose levels decline.

Stress (Selye's definition)

The nonspecific response of the body to any demand or stimulus, as defined by Hans Selye.

Stressor

The specific stimulus that triggers a physiological stress response.

Eustress

The optimal level of stress that leads to positive outcomes and high performance.

Neural Axis

A rapid, short-term stress response involving the autonomic and somatic nervous systems that is not sustained.

Autonomic Response

An involuntary response that occurs without conscious control and cannot be consciously adjusted.

Automatic Response

A response done out of habit or without conscious thought where control is still possible.

Neuroendocrine Axis

The 'fight-or-flight' response involving the sympathetic-adrenal axes, leading to the release of catecholamines.

Adrenal Medulla Secretion

The release of adrenaline ($\sim 80\%$) and noradrenaline following a $20-30\,s$ delay during a stress response.

Endocrine Axis (HPA)

A slower, long-lasting stress response involving the Hypothalamic-Pituitary-Adrenal axis and the release of cortisol or corticosterone.

CRH

Corticotrophin releasing hormone, a factor released by the hypothalamus to activate the anterior pituitary.

ACTH

Adrenocorticotropic hormone, released by the anterior pituitary to stimulate the adrenal cortex.

Adaptive Homeostasis

The transient expansion or contraction of the homeostatic range in response to exposure to signaling molecules or stressors.

Corticosterone-induced Immunosuppression

The reduction in immune system function caused by the release of corticosterone during stress.