Hormones
64 flashcards covering Hormones for the MCAT Biology & Biochemistry section.
Hormones are chemical messengers produced by glands in the endocrine system, such as the pituitary or thyroid. They travel through the bloodstream to target specific organs and tissues, influencing processes like growth, metabolism, reproduction, and stress responses. This system helps maintain balance in the body, ensuring functions like blood sugar regulation or immune activity work smoothly. Understanding hormones is essential because they coordinate many interconnected bodily systems, making them a foundation for studying human physiology.
On the MCAT, hormones frequently appear in biology and biochemistry questions, often testing knowledge of their production, mechanisms, and effects through multiple-choice scenarios or passage-based analysis. Common traps include confusing similar hormones, like cortisol and aldosterone, or misunderstanding feedback loops such as negative inhibition. Focus on key areas like the hypothalamic-pituitary axis, hormone classes (e.g., steroids vs. peptides), and disorders like hypothyroidism to excel. A solid grasp here can help tackle integrated questions linking hormones to other systems.
Practice drawing hormone pathways to visualize connections.
Terms (64)
- 01
Hormone
A signaling molecule produced by endocrine glands and released into the bloodstream to affect distant target cells, regulating processes like metabolism and growth.
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Endocrine gland
A ductless gland that secretes hormones directly into the bloodstream, such as the pituitary or thyroid, to coordinate body functions.
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Exocrine gland
A gland that secretes substances through ducts to a specific site, like sweat glands releasing sweat onto the skin, unlike endocrine glands.
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Steroid hormone
A lipid-soluble hormone derived from cholesterol, such as cortisol, that crosses cell membranes and binds to intracellular receptors to alter gene expression.
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Peptide hormone
A water-soluble hormone made of amino acids, like insulin, that binds to cell surface receptors and often triggers second messenger systems.
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Amine hormone
A hormone derived from amino acids, such as epinephrine, which can be water-soluble and act quickly via membrane receptors.
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Second messenger
An intracellular signaling molecule, like cAMP, activated by hormone binding to a receptor, amplifying the signal inside the cell.
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G protein-coupled receptor
A cell surface receptor that, when bound by hormones like epinephrine, activates G proteins to initiate signaling cascades such as those involving second messengers.
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Nuclear receptor
An intracellular receptor for steroid hormones, like estrogen receptors, that directly influence DNA transcription upon hormone binding.
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Hypothalamus
A brain region that produces releasing and inhibiting hormones to regulate the pituitary gland, controlling functions like thirst and body temperature.
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Pituitary gland
A small gland at the base of the brain that secretes hormones like growth hormone, regulated by the hypothalamus, affecting growth and reproduction.
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Anterior pituitary
The front lobe of the pituitary gland that produces tropic hormones, such as TSH, which stimulate other endocrine glands.
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Posterior pituitary
The back lobe of the pituitary gland that stores and releases hormones like oxytocin, produced by the hypothalamus.
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Thyroid gland
A neck gland that produces thyroid hormones like T3 and T4, which regulate metabolism, growth, and development.
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Parathyroid gland
Small glands near the thyroid that secrete parathyroid hormone to maintain blood calcium levels by acting on bones and kidneys.
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Adrenal gland
A gland atop each kidney with two parts: the cortex producing steroid hormones and the medulla producing catecholamines like epinephrine.
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Adrenal cortex
The outer layer of the adrenal gland that synthesizes steroid hormones such as cortisol and aldosterone for stress response and electrolyte balance.
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Adrenal medulla
The inner part of the adrenal gland that releases epinephrine and norepinephrine in response to stress, preparing the body for fight-or-flight.
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Pancreas
An organ that functions as both an exocrine and endocrine gland, with islet cells producing insulin and glucagon to regulate blood glucose levels.
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Insulin
A peptide hormone from pancreatic beta cells that lowers blood glucose by promoting its uptake into cells and storage as glycogen.
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Glucagon
A peptide hormone from pancreatic alpha cells that raises blood glucose by stimulating glycogen breakdown in the liver.
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Epinephrine
An amine hormone from the adrenal medulla that increases heart rate and blood sugar during stress as part of the fight-or-flight response.
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Norepinephrine
An amine hormone similar to epinephrine, released by the adrenal medulla and neurons, that helps regulate blood pressure and alertness.
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Cortisol
A steroid hormone from the adrenal cortex that promotes gluconeogenesis and suppresses inflammation during prolonged stress.
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Aldosterone
A steroid hormone from the adrenal cortex that increases sodium reabsorption in the kidneys, maintaining blood volume and pressure.
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Thyroid-stimulating hormone
A hormone from the anterior pituitary that stimulates the thyroid gland to produce and release T3 and T4 hormones.
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Thyroxine
Also known as T4, a thyroid hormone that is converted to T3 in tissues and increases metabolic rate by affecting cellular respiration.
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Triiodothyronine
Also known as T3, the active form of thyroid hormone that binds to nuclear receptors to regulate gene expression for metabolism.
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Growth hormone
A hormone from the anterior pituitary that promotes growth and cell division in children and helps maintain muscle and bone in adults.
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Follicle-stimulating hormone
A gonadotropin from the anterior pituitary that stimulates ovarian follicle development in females and sperm production in males.
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Luteinizing hormone
A hormone from the anterior pituitary that triggers ovulation in females and testosterone production in males.
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Prolactin
A hormone from the anterior pituitary that stimulates milk production in mammary glands after childbirth.
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Oxytocin
A peptide hormone from the posterior pituitary that promotes uterine contractions during labor and milk ejection during nursing.
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Vasopressin
Also known as ADH, a hormone from the posterior pituitary that conserves water by increasing kidney reabsorption, regulating blood osmolarity.
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Negative feedback
A regulatory mechanism where an increase in a hormone level inhibits its own production, such as cortisol suppressing ACTH release.
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Positive feedback
A less common mechanism where a hormone's action amplifies its own production, like oxytocin during childbirth contractions.
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Hypothalamic-pituitary axis
The interconnected system where the hypothalamus releases hormones to control the pituitary, which in turn regulates other endocrine glands.
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Renin-angiotensin-aldosterone system
A hormonal pathway where renin triggers angiotensin production, leading to aldosterone release to maintain blood pressure and fluid balance.
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Diabetes mellitus
A condition of insufficient insulin action, leading to high blood glucose, which can result from autoimmune destruction or insulin resistance.
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Type 1 diabetes
An autoimmune disorder where the pancreas produces little insulin, requiring external insulin for glucose regulation.
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Type 2 diabetes
A condition where cells become resistant to insulin, leading to elevated blood glucose, often linked to obesity and lifestyle factors.
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Goiter
An enlargement of the thyroid gland, often due to iodine deficiency, which impairs thyroid hormone production.
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Addison's disease
A disorder from adrenal cortex insufficiency, resulting in low cortisol and aldosterone, causing fatigue and electrolyte imbalances.
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Cushing's syndrome
A condition of excess cortisol, often from adrenal tumors, leading to symptoms like weight gain and high blood pressure.
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Hormone half-life
The time required for half of a hormone in the bloodstream to be metabolized or excreted, which is shorter for peptide hormones than for steroids.
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Hormone clearance
The process by which hormones are removed from circulation via liver metabolism or kidney excretion, maintaining hormonal balance.
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Hormonal permissiveness
A situation where one hormone must be present for another to exert its full effect, such as thyroid hormone enhancing catecholamine action.
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Hormonal synergism
When two hormones together produce a greater effect than each alone, like estrogen and progesterone in the menstrual cycle.
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Hormonal antagonism
When one hormone opposes the action of another, such as insulin lowering blood glucose while glucagon raises it.
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Tropic hormone
A hormone that stimulates another endocrine gland, like TSH stimulating the thyroid, as opposed to directly affecting target tissues.
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Non-tropic hormone
A hormone that acts directly on target tissues without stimulating another gland, such as growth hormone on bone and muscle.
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Melatonin
A hormone from the pineal gland that regulates sleep-wake cycles by responding to light-dark signals from the environment.
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Pineal gland
A small brain gland that secretes melatonin to influence circadian rhythms and reproductive functions in some animals.
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Calcitonin
A hormone from the thyroid's C cells that lowers blood calcium by inhibiting bone resorption and promoting kidney excretion.
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Parathyroid hormone
A hormone from the parathyroid glands that raises blood calcium by stimulating bone breakdown and kidney reabsorption.
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Estrogen
A steroid hormone from the ovaries that promotes female secondary sex characteristics and regulates the menstrual cycle.
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Progesterone
A steroid hormone from the corpus luteum that prepares the uterus for pregnancy and maintains the endometrial lining.
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Testosterone
A steroid hormone from the testes that develops male secondary sex characteristics and supports muscle growth.
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How insulin lowers blood glucose
Insulin binds to receptors on cells, facilitating glucose uptake and promoting its conversion to glycogen in the liver and muscles.
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Feedback loop for cortisol
Cortisol release is regulated by ACTH from the pituitary; rising cortisol levels inhibit both ACTH and CRH from the hypothalamus via negative feedback.
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Hormone receptor downregulation
A process where prolonged hormone exposure reduces the number of receptors on target cells, decreasing sensitivity, as seen with insulin in obesity.
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Up-regulation of receptors
An increase in receptor numbers on cells in response to low hormone levels, enhancing sensitivity, such as with thyroid hormones.
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Pulsatile hormone secretion
The intermittent release of hormones like gonadotropin-releasing hormone, which prevents receptor desensitization and maintains effective signaling.
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Hormonal transport proteins
Proteins in the blood, like albumin, that bind and transport lipid-soluble hormones, extending their half-life and regulating availability.