The Endocrine System - Part 1

Vocabulary practice flashcards covering the introductory physiology of the endocrine system, including hormone classifications, transport, mechanism of action, hormonal interactions, and endocrine disorders.

Exocrine Gland

A gland that secretes its products into a duct leading to an external surface or internal lumen, such as sweat glands or glands in the intestines.

Endocrine Gland

A ductless gland that synthesizes and releases hormones directly into the interstitial fluid and bloodstream to reach distant target cells.

Hormone

A chemical messenger secreted by endocrine cells (glands) into the blood that travels throughout the body to alter the function of specific target cells at very low concentrations.

Amine Hormones

A structural class of hormones that are derivatives of the amino acid tyrosine, including dopamine, catecholamines (epinephrine and norepinephrine) secreted by the adrenal medulla, and thyroid hormones.

Peptide and Protein Hormones

A major structural class representing the majority of hormones (e.g., insulin), which are typically synthesized as large, inactive precursors and cleaved into active fragments before secretion.

Steroid Hormones

A structural class of lipid-soluble hormones synthesized from cholesterol by the adrenal cortex and the gonads, including aldosterone, cortisol, testosterone, and estrogens.

Metabolic Inactivation (Biotransformation)

The biochemical alteration and degradation of circulating hormones primarily carried out by the liver to regulate blood hormone levels.

Permissive Effect

action of one hormone enhances the responsiveness or activity of another hormone (e.g., thyroid hormone upregulating beta-adrenergic receptors to permit epinephrine-stimulated lipolysis).

Synergistic Effect

the effect of two hormones acting together is greater or more extensive than the sum of their individual effects (e.g., follicle-stimulating hormone and estrogens).

Antagonistic Effect

one hormone opposes or reverses the action of another hormone (e.g., insulin lowering blood glucose while glucagon increases it).

Tropic Hormone

stimulate the secretion of another hormone from an endocrine gland (e.g., thyroid-stimulating hormone or follicle-stimulating hormone).

Hyposecretion

An endocrine disorder characterized by the release of an abnormally low quantity of a hormone into circulation, such as insulin deficiency in type 1 diabetes.

Hypersecretion

An endocrine disorder characterized by the secretion of an excessive amount of a hormone, such as oversecretion of growth hormone leading to gigantism or acromegaly.

Hyporesponsiveness

An endocrine disorder characterized by a decreased cellular responsiveness or sensitivity of target cells to a normal or elevated level of a hormone (e.g., target cell resistance to insulin in type 2 diabetes).

Hyperresponsiveness

An endocrine disorder characterized by an abnormally elevated or exaggerated target cell response to a hormone, such as an increased heart rate resulting from high circulating levels of thyroid hormones.

Pharmacological Effect

A physiological response resulting from administering a hormone for therapeutic purposes at supraphysiological concentrations, which may produce clinical side effects not observed at normal endogenous concentrations.

the risk of experiencing effects is based on: dose, length of treatment, age of patient (old and young more susceptible), type of steroid

what are the names of the 2 glands in the body?

exocrine and endocrine

the endocrine system

consists of glands and organs that secrete hormones, a single gland may secrete multiple hormones

what are the 4 functions of hormones?

established circadian rhythm, regulate operation of reproductive system, control growth and development, help regulate lots of things in the body

what are 3 main differences between the endocrine and nervous system?

• endocrine: chemical messengers + slower + often longer lasting effects

• nervous system: electrical conduit system + instantaneous + short lived

what does the structure of the hormone effect?

how they move/travel in the body

hormone transportation

• peptide and all catecholamine hormones are water soluble and so circulate dissolved in plasma (some peptide hormones bind to plasma proteins)

• steroid and thyroid hormones circulate mainly bound to plasma proteins

hormone excretion

• liver and kidneys are the major organs that remove the hormones from the plasma by metabolising or excreting them

• liver does metabolic inactivation

• kidney filters blood and removes waste products

• peptide and catechalomines are rapidly removed from the blood whilst steroid and thyroid hormones are removed more slowly

• after secretion some hormones are metabolised to make more active molecules in their target cells

where are the receptors for steroid/thyroid hormones and peptide/catecholamine hormones and what do they do?

• lipid soluble steroid and thyroid hormones - most receptors are found inside target cells and they affect cell function by altering gene expression

• water soluble peptide hormones and catecholamines - most receptors are on the plasma membrane and they both exert rapid (nongenomic) and slower (gene transcription) actions on the same target cell

what 3 things does the responsiveness of a target cell to a hormone depend on?

• the hormones concentration in the blood

• the abundance of the targets cell hormone receptors

• influences exerted by other hormones

what system regulates the secretion of hormones?

the negative feedback system

what are the 3 inputs that control hormone secretion?

• plasma conc of an ion or nutrient that the hormone regulates

• neural input to the endocrine cells

• other hormones (as the secretion is directly controlled by the blood conc of another hormone)