Endocrine System Quiz

The endocrine system is a network of glands and tissues that release hormones into the bloodstream.
Hormones act as chemical messengers, controlling various bodily functions.
Endocrine glands are ductless; they secrete hormones directly into the bloodstream.
Other organs, like the pancreas, also secrete hormones alongside their primary functions.
Primary endocrine organs include the pituitary, pineal, thyroid, parathyroid, and adrenal glands.
Secondary endocrine organs contain endocrine cells scattered within other organs such as the pancreas, thymus. gonads, and hypothalamus.
Hormones circulate in the bloodstream, traveling long distances to reach their target cells.
Target cells contain specific receptors for particular hormones.
Activation of receptors initiates a physiological/biological response.
Some hormones act locally rather than through the bloodstream, influencing neighboring cells as paracrine regulators or affecting the cell that produced them as autocrine (self-regulating) regulators.
The effects of hormones depend on the programmed response of the target cells. Not all cell types respond similarly to the same hormone.
Hormone effects can involve activating or repressing one or more genes, leading to specific cellular responses.

Receptors are located on the surface, within the cytoplasm, or in the nucleus of target cells.
Receptors are activated only by specific hormones.
Hormone action depends on binding to specific receptors.
If a hormone does not bind to a receptor, there is no physiological effect.

Hormones are classified as peptides, amino acid derivatives, or steroids.
Peptide hormones are chains of amino acids.
They are water-soluble, stored in vesicles, and their receptors are on the surface of target cells.
Amino acid derivatives are derived from amino acids tyrosine or tryptophan.
Primarily water-soluble, with receptors typically on the cell surface.
Steroid hormones are derived from cholesterol.
They are lipid-soluble, not stored in vesicles, and their receptors are intracellular.
Lipophilic hormones readily pass through cell membranes.
Hydrophilic hormones typically do not readily pass through cell membranes.

Hormonal actions are crucial for many bodily functions.
Actions include fetal development, cell growth, metabolism, cardiovascular function, renal function, skeletal function, reproductive function, immune function, and central nervous system function.

Homeostasis refers to maintaining a constant/stable internal environment of organisms.
It involves maintaining a healthy balance in body temperature, blood pH, blood pressure, and so forth.
Hormones play a key role in regulating these systems.

The hypothalamus and pituitary glands work together in hormone regulation.
Releasing hormones (RH) from the hypothalamus stimulate the anterior pituitary’s hormone production.
Inhibiting hormones (IH) from the hypothalamus suppress the production of anterior pituitary hormones.
The hypophyseal portal system connects the hypothalamus and anterior pituitary, allowing for rapid hormonal exchange.
The posterior pituitary releases hormones made in the hypothalamus.

The pituitary gland is critically important for endocrine regulation.
It is often called the "master gland", controlling the secretion of numerous other hormones.
The structure includes an anterior and posterior pituitary.
The anterior pituitary releases tropic hormones that act on other glands to promote their hormone release.
The posterior pituitary stores and releases hormones (oxytocin & ADH) made by the hypothalamus.

Several important hormones are released from anterior and posterior pituitary glands.
Anterior pituitary hormones include TSH (thyroid-stimulating hormone), ACTH (adrenocorticotropic hormone), FSH (follicle-stimulating hormone), LH (luteinizing hormone), PRL (prolactin), and growth hormone (GH).
Posterior pituitary hormones include ADH (antidiuretic hormone) and oxytocin.

The adrenal glands are located on top of the kidneys and have two parts: cortex and medulla.
The adrenal cortex releases steroid hormones such as corticosteroids (e.g., cortisol), and mineralocorticoids (e.g., aldosterone).
Cortisol regulates metabolism during stressful situations.
Aldosterone promotes water and sodium retention.
The adrenal medulla releases catecholamines (e.g., epinephrine, norepinephrine) responsible for "fight-or-flight" responses.

Parathyroid glands are small structures located on the posterior surface of the thyroid.
They produce parathyroid hormone (PTH) which regulates blood calcium levels.
PTH increases blood calcium levels by stimulating bone resorption and increasing calcium absorption in the intestines.
PTH and calcitonin (released by the thyroid) maintain calcium balance.

Neurohormones are hormones released directly by neurons into the bloodstream.
They come in three types: (1) neurotransmitters released into the blood, (2) hormones produced by neurons but released from axon terminals, and (3) releasing hormones that stimulate release at another gland.
Examples include epinephrine, norepinephrine, dopamine, oxytocin & vasopressin.

Hormone secretion is often regulated through feedback loops.
Negative feedback mechanisms keep hormone levels within a desired range.
Positive feedback mechanisms amplify a signal, often associated with processes like childbirth.

Relevant pathologies include diabetes insipidus, acromegaly, gigantism, goiter, hypothyroidism, hyperthyroidism, Graves' disease, Addison's disease, and Cushing's syndrome.
These involve malfunctions/dysregulation of hormone production or action.