Endocrine System Overview

Endocrine System

System of ductless glands that secrete hormones

Hormones

"Messenger molecules" that circulate in the blood and act on distant target cells

Target Cells

Cells that respond to hormones for which they have receptors

Hormone Effects

Dependent on the programmed response of the target cells; hormones act as molecular triggers

Endocrine Organs

Organs that include purely endocrine organs like pituitary, pineal, thyroid, parathyroid glands, adrenal cortex, adrenal medulla, as well as endocrine cells in other organs like pancreas, thymus, gonads, and hypothalamus

Hormone Actions - Lock and Key

Describes the interaction between hormones and their specific receptors; protein hormones interact with cell membrane receptors, while steroid hormones bind to receptors in the cell's cytoplasm or nucleus

Steroid Hormones

Pass through the cell membrane, bind to specific receptors, enter the nucleus to bind with DNA, activate certain genes, and promote protein synthesis for various functions

Protein Hormones

React with specific receptors outside the cell, triggering enzyme reactions leading to the formation of second messengers like AMP, which produce specific intracellular functions

Pituitary Hormones

Include TSH, ACTH, GH, ADH, and Oxytocin, with TSH stimulating thyroid hormone production, ACTH stimulating corticosteroid production, GH stimulating growth, ADH stimulating water reclamation by kidneys, and Oxytocin prompting muscle contractions

TSH

Thyroid-stimulating hormone

ACTH

Adrenocorticotropic hormone

GH

Growth hormone

ADH

Antidiuretic hormone

Oxytocin

Hormone that prompts muscle contractions in reproductive tracts and initiates labor and milk ejection in females

Hypothalamus Hormone Control

Controls anterior pituitary hormone release through releasing hormones secreted into capillaries and veins, regulating the secretion of hormones by other endocrine glands

Thyroid Gland

Located in the anterior neck on the trachea just inferior to the larynx; produces thyroid hormone and calcitonin

Thyroid Hormone

Tyrosine-based hormone with 3 or 4 iodine molecules; includes T4 (thyroxine) and T3 (triiodothyronine)

Calcitonin

Hormone involved in calcium and phosphorus metabolism; secreted from thyroid parafollicular cells

Feedback Loop

A regulatory process where a change in a certain variable triggers responses that counteract the initial change; e.g., thyroid hormone feedback loop

TRH

Thyrotropin-releasing hormone released from the hypothalamus

Thyroxine

Thyroid hormone that regulates basal metabolic rate and affects protein synthesis, bone growth, and neuronal maturation

Exophthalmos

Eye bulging associated with Grave's disease, an autoimmune disorder affecting the thyroid

Calcium

Mineral essential for bone health and muscle function; regulated by hormones like calcitonin and parathyroid hormone

Parathyroid Hormone

Hormone produced by the parathyroid glands that increases blood calcium levels by various mechanisms

Adrenaline Rush

Physiological response to stress or danger, characterized by increased heart rate, blood flow to muscles, and heightened awareness

Adrenal Gland

Endocrine gland consisting of the adrenal cortex and adrenal medulla, secreting various hormones for stress response

Aldosterone

Main mineralocorticoid hormone that regulates sodium and water balance in response to blood volume or pressure changes

Cortisol

Primary glucocorticoid hormone involved in stress response, metabolism, and immune function

Autonomic System

Part of the nervous system controlling involuntary functions like heartbeat, respiration, and digestion; includes sympathetic and parasympathetic divisions

Sympathetic Nervous System

Division of the autonomic system responsible for the 'fight or flight' response, releasing adrenaline and increasing heart rate

Parasympathetic Nervous System

Division of the autonomic system that promotes rest and digestion, calming the body and lowering heart rate

Glucagon

Hormone secreted by pancreatic alpha cells that raises blood sugar levels by releasing stored glucose

Insulin

Hormone secreted by pancreatic beta cells that lowers blood sugar levels by facilitating glucose uptake

Diabetes

Metabolic disease characterized by high blood glucose levels due to insufficient insulin production or utilization