PhysioNotes3S25

Endocrine System

A system of cells, tissues, and organs that secrete hormones into the blood for regulating homeostasis.

Hormones

Chemicals secreted by endocrine glands that regulate various functions in the body.

Homeostasis

The maintenance of a stable internal environment in the body.

Comparison to Nervous System: Similarities

Both systems are regulatory, transmit messages, and activate target cells via specific receptors.

Comparison to Nervous System: Differences

The endocrine system uses chemical hormones and has a slower effect compared to the nervous system's impulses.

Up-regulation

The increase in the number of receptors in response to prolonged exposure to low concentrations of hormones.

Down-regulation

The decrease in the number of receptors in response to prolonged exposure to high concentrations of hormones.

Synergistic Interaction

An interaction where multiple hormones work together to produce a greater combined effect.

Antagonistic Interaction

An interaction where one hormone counteracts the effects of another.

Permissive Effects

When one hormone enhances the effects of another hormone on a target organ.

Lipophilic Hormones

Hormones that are nonpolar and can pass through the cell membrane of target cells.

Polar Hormones

Hormones that cannot pass through the cell membrane and bind to cell membrane receptors.

Adenylyl cyclase

A second messenger mechanism activated by polar hormones, resulting in cyclic AMP.

Thyroid Stimulating Hormone (TSH)

Stimulates production and secretion of T4 by the thyroid.

Adrenocorticotropic Hormone (ACTH)

Stimulates the adrenal cortex to secrete glucocorticoids.

Insulin

A hormone secreted by the beta cells of the pancreas that promotes cellular uptake of glucose.

Glucagon

A hormone secreted by the alpha cells of the pancreas that promotes glycogenolysis and increases blood glucose levels.

Metabolic Rate

The total amount of energy used by the body per day, including BMR and physical activity.

Body Mass Index (BMI)

A measurement used to assess obesity based on height and weight.

General Adaptation Syndrome (GAS)

A pattern of hormonal and nervous responses to stressors that aims to maintain homeostasis.

Metabolism

The sum of anabolic and catabolic reactions that manage energy in the body.

Caloric Energy Expenditures

The total energy expended when at rest (BMR), during physical activity, and in thermogenesis.

Basal Metabolic Rate (BMR)

The amount of energy expended by a human at rest.

Adaptive Thermogenesis

Heat energy produced to maintain body temperature in response to environmental changes.

Excitation-Contraction Coupling

The series of events linking muscle action potential to muscle contraction.