Chapter 5: The Endocrine System Flashcards
The endocrine system consists of organs, known as ___________, that secrete hormones.
Glands
____________ are signalling molecules that are secreted directly into the bloodstream to distant target tissues.
Hormones
______________ are made up of amino acids, ranging in size from quite small (such as anti-diuretic hormone, ADH) to relatively large (such as insulin).
Peptide hormones
Peptide hormones are released by ____________ after being packaged into vesicles in the Golgi apparatus
exocytosis
Because peptide hormones are charged and cannot pass through the plasma membrane, they must bind to an extracellular receptor. The peptide hormone is considered the _______ messenger; it binds to the receptor and triggers the transmission of a second signal, known as the ________ messenger.
First messenger, second messenger
The connection between the hormone at the surface and the effect brought about by second messengers within the cell is known as a _____________
Signalling cascade
In the activation of G protein-coupled receptor system, the binding of a peptide hormone triggers the receptor to either activate or inhibit an enzyme called _____________, raising or lowering the levels of cAMP accordingly.
Adenylate cyclase
cAMP can bind to intracellular targets, such as ____________, which phosphorylates transcription factors like cAMP response element-binding protein (CREB) to exert the hormone’s ultimate effect.
Protein kinase A
Peptide hormones are _________-soluble, as they can travel freely in the bloodstream and usually do not require carriers.
Water-soluble
____________ hormones are derived from cholesterol and are produced primarily by the gonads and adrenal cortex.
Steroid hormones
One common form of conformational changes of steroid hormone-receptor complexes upon binding is ___________, or pairing of two receptor-hormone complexes.
Dimerization
Steroid hormones are _________-soluble, so they must be carried by proteins in the bloodstream to travel around the body.
Lipid-soluble
_____________ hormones are derived from one or two amino acids, usually with a few additional modifications.
Amino acid-derivative hormones
The ____________ (epinephrine and norepinephrine) bind to the G protein-coupled receptors, while thyroid hormones bind intracellularly.
Catecholamines
_____________ are secreted and act directly on a target tissue. For example, insulin released by the pancreas causes increased uptake of glucose by muscles.
Direct hormones
_______________ require an intermediary to act. For example, gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) do not cause direct changes in the physiology of muscle, bone, and hair follicles; they stimulate the production of another hormone by another endocrine gland that acts on these target tissues.
Tropic hormones
By regulating the pituitary gland through tropic hormones, the ____________ is capable of having organism-wide effects.
Hypothalamus
The release of hormones by the hypothalamus is regulated by _____________. ____________ occurs when a hormone (a product) later in the pathway inhibits hormone (or enzymes) earlier in the pathway.
Negative feedback
The hypothalamus secretes compounds into the ____________, which is a blood vessel system that directly connects the hypothalamus with the anterior pituitary.
Hypophyseal portal system
___________ is a alternative term for the pituitary.
Hypophysis
Hypothalamus: Gonadotropin-releasing hormone (GnRH) -> Anterior pituitary: ____________ and ____________
Follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
Hypothalamus: Growth hormone-releasing hormone (GHRH) -> Anterior pituitary: ___________
Growth hormone (GH)
Hypothalamus: Thyroid-releasing hormone (TRH) -> Anterior pituitary: ______________
Thyroid-stimulating hormone (TSH)
Hypothalamus: Corticotropin-releasing factor (CRF) -> Anterior pituitary: ___________
Adrenocorticotropic hormone (ACTH)
As long as the hypothalamus releases ____________, which is actually dopamine, no prolactin will be released.
Prolactin-inhibiting factor (PIF)
The release of corticotropin-releasing factor (CRF) from the hypothalamus will stimulate the anterior pituitary to secrete adrenocorticotropic hormone (ACTH). ACTH will then cause the adrenal cortex to increase the level of ___________ being secreted into the blood.
Cortisol
Three-organ systems, such as the hypothalamic-pituitary-adrenal (HPA) _______, are commonly referred to as _______.
Axis, axes
__________ stimulates uterine contractions during labor, as well as milk letdown during lactation. It is released from the posterior pituitary.
Oxytocin
___________ (also called vasopressin) increases reabsorption of water in the collecting ducts of the kidneys. It is secreted (in posterior pituitary) in response to increased plasma osmolarity, or increased concentration of solutes within the blood.
Antidiuretic hormone (ADH)
The ____________ synthesizes and secretes 7 different products. Four of these are tropic hormones, while the other three are direct hormones.
Anterior pituitary
Products of the anterior pituitary:
FLAT PEG
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Adrenocorticotropic hormone (ACTH)
- Thyroid-stimulating hormone (TSH)
- Prolactin
- Endorphins
- Growth hormone (GH)
____________ is more important in females than I males; it stimulates milk production in the mammary glands.
Prolactin
When estrogen, progesterone, and __________ levels drop, that the block on milk production is removed and lactation usually begins.
Dopamine
___________, a direct hormone that decrease the perception of pain.
Endorphins
___________ promotes the growth of bone and muscle. It prevents glucose uptake in tissues that are not growing and stimulates the breakdown of fatty acids.
Growth hormone (GH)
Bone growth originates in special regions of the bone known as ______________, which seal shut during puberty.
Epiphyseal plates
An excess of growth hormone (GH) released in childhood (before epiphyseal plates closure) can cause ___________
Gigantism
A deficit of growth hormone (GH) in childhood (before epiphyseal plates closure) results in __________
Dwarfism
In adults, __________ is a medical condition that growth hormones has an effect on smaller bones (usually in hands, feet, and head).
Acromegaly
_____________ is secreted in response to low blood volume (as sensed by baroreceptors) or increased blood osmolarity (as sensed by osmoreceptors).
Antidiuretic hormone (ADH)
Oxytocin is unusual in the it has a ___________ feedback loop: the release of oxytocin promotes uterine contraction, which promotes more oxytocin release, which promotes stronger uterine contractions, and so on.
Positive feedback
The __________ is controlled by thyroid-stimulating hormone from the anterior pituitary.
Thyroid
One of the major functions of thyroid is releasing ____________ (T3) and ___________ (T4) to set the basal metabolic rate.
Triiodothyronine (T3), thyroxine (T4)
One of the major functions of thyroid is releasing ____________ to promote calcium homeostasis.
Calcitonin
Triiodothyronine (T3) and thyroxine (T4) are both produced by the iodination of the amino acid ___________ in the follicular cells of the thyroid.
Tyrosine
High plasma levels of thyroid hormones will lead to decreased ____________ and ___________ synthesis; negative feedback prevents excessive secretion of T3 and T4.
Thyroid-stimulating hormone (TSH), thyroid-releasing hormone (TRH)
A deficiency of iodine or inflammation of the thyroid may result in ____________.
Hypothyroidism
___________ is caused by thyroid hormones deficiency that result in intellectual disability and developmental delay.
Cretinism
An excess of thyroid hormone, which may result from a tumour or thyroid over-stimulation, is called _____________.
Hyperthyroidism
___________ cells within the thyroid gland produce thyroid hormones.
Follicular cells
___________ cells (also called ______________ cells) produce calcitonin.
C-cells, parafollicular cells
Calcitonin decreases plasma calcium levels in 3 ways: by ____________ calcium excretion from the kidneys, by ___________ calcium absorption from the gut, and by ____________ storage of calcium in the bone.
increasing, decreasing, increasing
The __________ are 4 small pea-sized structures that sit on he posterior surface of the thyroid.
Parathyroids
_______________ serves as an antagonist hormone to calcitonin, raising blood calcium levels; specifically, it decreases excretion of calcium by the kidneys, increases absorption of calcium in the gut (via vitamin D), and increases bone resorption, thereby freeing up calcium.
Parathyroid hormone (PTH)
As levels of plasma calcium rise, ___________ hormone secretion is decreased.
Parathyroid
Parathyroid hormone activates ____________, which is required for the absorption of calcium and phosphate in the gut.
Vitamin D
The ___________ secretes corticosteroids.
Adrenal cortex
Corticosteroids are steroid hormones that can be divided into 3 functional classes: ___________, ___________, ___________.
Glucocorticoids, mineralocorticoids, and cortical sex hormones
____________ are steroid hormones that regulate glucose levels.
Glucocorticoids
The 2 most common glucocorticoids are ___________ and ___________.
Cortisol, cortisone
___________ is known as a stress hormone because it is released in times of physical or emotional stress. This increases blood sugar and provides a ready source of fuel for the body.
Cortisol
_____________ from the hypothalamus promotes release of ____________ hormone from the anterior pituitary, which promotes release of glucocorticoids from the adrenal cortex.
Corticotropin-releasing factor (CRF)
Adrenocorticotropic hormone (ACTH)
____________ are used in salt and water homeostasis; their most profound effects are on the kidneys.
Mineralocorticoids
The most noteworthy mineralocorticoid is ___________, which increases sodium reabsorption in the distal convoluted tubule and collecting duct of the nephron (increasing blood volume + pressure).
Aldosterone
Unlike antidiuretic hormone (ADH) that increasing the water reabsorption in the kidney leads to decreasing plasma osmolarity, ___________ allows water and sodium ion to flow together and the plasma osmolarity remains unchanged.
Aldosterone
___________ deceases the reabsorption of potassium and hydrogen ions in the distal convoluted tubule and collecting duct of the nephron, promoting their excretion in the urine.
Aldosterone
Unlike the glucocorticoids, aldosterone is primarily under the control of the ________________ system.
Renin-angiotensin-aldosterone system
Decreased blood pressure causes the _______________ of the kidney to secrete renin, which cleaves an inactive plasma protein, angiotensinogen, to its active form, angiotensin I.
Juxtglomerular cells
The active form angiotensin I is converted to angiotensin II by ______________ in the lungs.
Angiotensin-converting enzyme (ACE)
______________ stimulates the adrenal cortex to secrete aldosterone.
Angiotensin II
Once blood pressure is restored, there is a decreased drive to stimulate ________ release, thus serving as the negative feedback for the renin-angiotensin-aldosterone system.
Renin
The adrenal glands make cortical sex hormones (including __________ and ___________)
Androgen
Estrogen
___________ is responsible for the production of epinephrine and norepinephrine.
Adrenal medulla
__________ is understood to mediate long-term (slow) stress response. It also increases the synthesis of catecholamines as well, resulting in an increase in catecholamine release.
Cortisol
From the endocrine standpoint, small clusters of hormone-producing cells are grouped together into ____________ throughout the pancreas.
Islets of Langerhans
Islets contain distinct types of cells: __________, _________, and __________ cells.
Alpha
Beta
Delta
From the exocrine standpoint, acinar cells secrete digestive enzymes into pancreatic _________.
Duct
Alpha cells of the islets of Langerhans secrete __________ (hormone).
Glucagon
Beta cells of the islets of Langerhans secrete ___________ (hormone).
Insulin
Delta cells of the islets of Langerhans secrete ____________ (hormone).
Somatostatin
___________ is secreted during times of fasting. When glucose levels are low, it increases glucose production by triggering glycogenolysis, gluconeogenesis, and the degradation of protein and fat.
Glucagon
____________ is antagonistic to glucagon and is therefore secreted when blood glucose levels are high.
Insulin
In excess, insulin will cause _____________, which is characterized by low blood glucose concentration.
Hypoglycemia
Underproduction, inefficient secretion, or insensitivity to insulin can result in _____________, which is clinically characterized by hyperglycaemia (excess glucose in the blood).
Diabetes mellitus
Diabetes often report ___________ (increased frequency of urination) and __________ (increased thirst).
Polyuria
Polydipsia
___________ (insulin-dependent) diabetes mellitus is caused by autoimmune destruction of the beta cells of the pancreas, resulting in low or absent insulin production. It requires regular injections of insulin to prevent hyperglycaemia and to permit uptake of glucose into cells.
Type I
___________ (non-insulin-dependent) diabetes mellitus is the result of receptor-level resistance to the effects of insulin. It is partially inherited and partially due to environmental factors, such as high carbohydrate diets and obesity.
Type II
_______________ hormones can raise blood glucose levels. Examples are growth hormone, glucocorticoids, and epinephrine.
Counterregulatory hormones
____________ is an inhibitor of both insulin and glucagon secretion. High blood glucose and amino acid concentrations stimulate its secretion.
Somatostatin
____________ is produced by the hypothalamus, where it decreases growth hormone secretion in addition to its effects on insulin and glucagon.
Somatostatin
The ___________ secrete testosterone in response to stimulation by gonadotropins (luteinizing hormone and follicle-stimulating hormone).
Testes
_____________ causes sexual differentiation of the male during gestation and also promotes the development and maintenance of secondary sex characteristics in males, such as axillary and pubic hair, deepening of the voice, and muscle growth.
Testosterone
The ___________ secrete estrogen and progesterone in response to gonadotropins.
Ovaries
___________ is involved in development of the female reproductive system during gestation and also promotes the development and maintenance of secondary sex characteristics in females, such as axillary and pubic hair, breast growth, and body fat redistribution.
Estrogen
The _________ gland is located deep within the brain, where it secretes the hormone melatonin.
Pineal gland
It is hypothesized that the pineal gland responds to decreases in light intensity by releasing ____________.
Melatonin
The kidneys produce _____________, which stimulates bone marrow to increase production of erythrocytes (red blood cells). It is secreted in response to low oxygen levels in the blood.
Erythropoietin
The heart releases ____________ peptide to help regulate salt and water balance. It is released when cells in the atria are stretched from excess blood volume.
Atrial natriuretic peptide (ANP)
The thymus, located directly behind the sternum, releases ____________, which is important for proper T-cell development and differentiation.
Thymosin
