Endocrine system Flashcards
what system governs hormonal release?
the autonomic nervous system
4 structural groups of hormones
(a) peptides and proteins
(b) steroids
(c) amino acid derivatives (biogenic amines), (d) fatty acid derivatives (eicosanoids).
Peptide proteins are those such as
GH, IGF-1, and insulin
steroid hormone examples
testosterone, estradiol, and cortisol
Amino acid derivative hormones examples
epinephrine, norepinephrine, and dopamine.
Eicosanoid hormone examples
prostaglandins and leukotrienes.
function of hormones
-chemical messengers
-the effect of a hormone on a tissue is determined by the plasma concentration and the number of active receptors.
function of binding proteins
-carry hormones in the blood and/or some can remain unbound
-act as storage sites within the circulation where they fight hormonal degradation and extend the hormone’s half-life.
Most hormones are not active unless they are……….
separated from their specific binding protein.
testosterone is bound by both sex hormone binding ______________ and ___________.
globulin (SHBG), albumin
GH is bound by __________
GH binding protein
IGF-1 is bound by ________
IGF-1 binding protein
Until hormones are released from their respective binding proteins, they are not biologically active for ___________ and __________
-receptor binding
-cell signaling
What determines the plasma concentration of hormones?
a) rate of secretion from the endocrine gland
(b) magnitude of secretion,
(c) rate of metabolism or excretion of hormone,
(d) quantity of transport proteins,
(e) changes in plasma volume.
what is the magnitude of a hormone’s effect on its effector dependent on?
(a) hormone concentration,
(b) receptor density on the cell membrane or within the cytoplasm,
(c) receptor affinity for the hormone
Receptor downregulation
a decrease in receptor number in response to a consistently high concentration of hormone.
Receptor upregulation
an increase in receptor number in response to a consistently low concentration of hormone.
Cellular hormone production and blood hormone concentrations are maintained by ____________
feedback mechanisms
target gland examples
the thyroid gland, adrenal glands, and gonads
_______ hormones are released from their respective tissue/gland/organ into the bloodstream where they travel to their effector site (another tissue/organ/gland)
Endocrine hormone
Neuroendocrine hormones are released from _______________ and often serve as ___________
-nerve terminals
-neurotransmitters
Paracrine hormones act on cells ___________ to the ones from which they are released
adjacent
_____________ hormones act on cells from the same tissue, organ, or gland from which they are released
Autocrine hormones
____________ hormones act within the same cell that synthesizes them.
Intracrine hormones
Three Types of Hormone Release
-hormonal
-humoral
-neural
Hormonal release occurs when….
when hormones are released based on stimulation from other hormones
Humoral release occurs in response to….
to changing levels of ions or nutrients in the blood
example of humoral release
the stimulation of parathyroid hormone (PTH) from the parathyroid gland due to low calcium levels
example of hormonal release
the release of insulin from pancreatic beta cells, thereby regulating the release of glucagon from pancreatic alpha cells.
Neural release occurs when……
when hormone release is stimulated by nerves
example of neural release
the release of norepinephrine from sympathetic nerves
The release or secretion of hormones can occur by either a __________ or ___________ mechanism.
-constitutive
-regulated
___________ secretion involves the cell storing hormone in secretory vesicles and releasing them in bursts when stimulated
Regulated secretion
__________ secretion involves the cell not storing hormone, rather releasing it from secretory vesicles as it is synthesized.
constitutive secretion
function of regulated secretion
This pathway is highly prevalent in the body and allows cells to secrete a large amount of hormone over a short period of time
example of regulated secretion
-the release of insulin in response to the pancreatic beta cells detecting elevated levels of glucose in the blood.
-The amount of insulin release would be directly related to the glycemic load detected by the beta cells.
function of constitutive secretion
allows for the maintained concentration of hormones in the blood
example of constitutive secretion
testosterone, because the levels of this hormone typically remain constant on a routine basis and the clinically normal levels are typically not affected by other hormones or metabolites.
The pituitary gland (hypophysis) is composed of which two regions?
-the anterior lobe (adenohypophysis)
- the posterior lobe (neurohypophysis)
The pituitary gland is connected to the hypothalamus of the brain by the _____________
infundibulum.
Within the infundibulum is the _________________ system.
hypophyseal circulatory system
Axons from hypothalamic nuclei extend to the _____________, where hormones are stored until released into the systemic bloodstream.
posterior pituitary
Axons from hypothalamic nuclei induce the release of hormones into the _________________________ which carries them directly to the anterior pituitary.
hypophyseal portal circulation
function of the hypothalamus
-control of regulating energy homeostasis
-responsible for monitoring metabolic changes by sensing alterations in the plasma levels of various metabolic hormones and macronutrient oxidation rate.
the _____________________ is associated with hyperphagia and obesity
the ventromedial hypothalamus (VMH)
__________________________ is associated with aphagia and starvation
the lateral hypothalamus (LH)
Which hypothalamic sites are associated with regulating food intake and body weight regulation?
-the arcuate nucleus (ARC),
-the dorsomedial nuclei (DMN) -paraventricular (PVN) nuclei
Within these hypothalamic areas, an abundance of __________ and __________ peptides generate signals that constitute a major part of the neural circuitry regulating feeding/ body weight are produced.
orexigenic and anorectic
Some peptidergic signals involved in energy homeostasis by stimulating food intake are _______, ___________and ___________________
ghrelin, neuropeptide Y (NPY), and growth hormone–releasing hormone (GHRH),
some peptidergic signals that inhibit food intake are -_________, __________, and _______________
leptin, insulin, and glucagon-like peptide 1 (GLP-1)
The anterior pituitary gland is controlled by………?
releasing activating and inhibitory hormones secreted into the hypophyseal portal circulation.
How do hormones reach the anterior pituitary gland?
directly through the hypophyseal portal circulation without entering the systemic circulation.
what secretes the trophic hormones?
specific secretory cell types of the anterior pituitary
what are the 6 major trophic hormones?
-thyroid stimulating hormone [TSH], -adrenocorticotropic hormone [ACTH], -follicle stimulating hormone [FSH], -luteinizing hormone [LH],
-prolactin
-growth hormone
purpose of trophic hormones
act on distal endocrine glands, which together have feedback effects on these endocrine systems, designed to regulate blood levels of the hormone’s effector.
_______________ is a protein that stimulates the growth of bones, muscles, and other organs by increasing protein synthesis.
growth hormone
what controls the release of growth hormone?
The release of GH is controlled by growth hormone–releasing/inhibiting hormone, somatostatin (SS).
function of growth hormone
-has an important role in tissue growth and the regulation of metabolism.
-induces the release of insulin-like growth factor-1. Hepatically derived IGF-1 has the ability to induce muscle protein synthesis.
__________________ produces its own specific form of IGF-1 known as MGF that can also stimulate muscle protein synthesis.
skeletal muscle
The pineal gland
-located within the brain
-consists of portions of neurons and pinealocytes
pinealocytes
-specialized secretory cells that synthesize the hormone melatonin and secrete it directly into the cerebrospinal fluid.
The thyroid gland
-located in the anterior portion of the neck. - consists of two lobes, one on each side of the trachea.
The thyroid gland consists of ____ lobes, which are connected by the ____________
-2 lobes
- isthmus
what are two main types of thyroid hormones?
-thyroxine (T4, 80% of total) -triiodothyronine (T3, 20% of total)
(they differ by adding one iodine in T4)
The majority of circulating T4 and T3 are bound to a _________________.
thyroxine-binding protein.
Approximately 95% of T4 is converted to active T3 at target tissues by the enzyme, _________________.
5′-deiodinase action.
The T3 binds to ___________ receptors, initiating transcription of a variety of proteins and enzymes.
nuclear receptors
What regulates thryroid hormone secretion?
it is regulated by a negative feedback mechanism that involves the amount of circulating thyroid hormone, TSH, hypothalamus, and adenohypophysis.
the pancreas
-organ that lies in the upper abdomen between the stomach, duodenum of small intestine, and spleen.
-secretes digestive enzymes pancreatic lipase, amylase, and protease through by going through the pancreatic duct to the duodenum
amylase
enzyme for carbohydrates
protease
enzyme for protein
How does the pancreas respond to an elevated glycemic load?
the endocrine function of the pancreas involves the synthesis and secretion of insulin from the beta cells comprising the islets of Langerhans.
The alpha cells synthesize and secrete _________ in response to a low glycemic load,
glucagon
the delta cells release___________________ to assist with the negative feedback of GH as this hormone is involved in increasing the blood levels of glucose through liver glycogenolysis.
somatostatin (SS)
The gonads
-the primary reproductive organs with the body and include the testes and ovaries, respectively, in the male and female.
testosterone can also be produced in the _____________
adrenal cortex
What is testosterone regulated by?
regulated by the hypothalamo-pituitary-gonadal (HPG) axis, FSH and LH from the anterior pituitary that stimulate the testes to produce testosterone.
hypothalamo-pituitary-gonadal (HPG) axis
a negative feedback system that involves gonadotropin releasing hormone (GnRH) from the hypothalamus
Through the feedback loop of the HPG axis, high levels of circulating testosterone in men and estradiol in women can inhibit the activity of the hypothalamus to release __________ and the anterior pituitary to release ________ and ___________
-GnRH (Gonadotropin releasing hormone)
-LH and FSH.
LH stands for
Luteinizing hormone
FSH stands for
follicle stimulating hormone
The adrenal gland consists of two main regions: the ________ and the _____________
Cortex of the adrenal gland
-the outer region of the adrenal gland
-releases the steroid hormones, cortisol, and aldosterone.
Aldosterone
involved in regulating sodium reabsorption in the kidneys to maintain body water levels.
Cortisol
related to resistance training, it has the ability to increase muscle protein degradation which is inevitably used to increase blood glucose levels during periods of fasting (hypocalorism)
medulla of the adrenal gland
-inner portion of the adrenal gland
-secretes the catecholamines, epinephrine, and norepinephrine in a neuroendocrine manner
adrenal gland
the target source for the hypothalmo-pituitary-adrenal (HPA) axis
cortical and medullary hormones secretion invokes….
activation of the sympathetic nervous system
how do the cortical and medullary hormones affect exercise?
-the hormones cause an increase activity of the cardiovascular system, glycogenolysis (glycogen breakdown to glucose) in both liver and muscle, and lipolysis (triglycerides breakdown) in adipose tissue.
Hypothalamus
Hormones released by the posterior pituitary and hormones that regulate the anterior pituitary.
Oxytocin is..
-released by the pituitary gland/hypothalamus
-cued by chemical peptides
-Stimulates contraction of uterus and mammary gland cells
-regulated by the nervous system
Antidiuretic hormone (ADH)
-released by the pituitary gland/hypothalamus
-cued by chemical peptides
-Promotes retention of water by kidneys
-regulated by water salt balance
Growth Hormone (GH)
-released by the pituitary gland/hypothalamus
-cued by protein
-Stimulates growth (especially bones) and metabolic functions
-regulated by hypothalamic hormones
Prolaction (PRL)
-released by the pituitary gland/hypothalamus
-cued by protein
-stimulates milk production
-regulated by hypothalamic hormones
Follicle-stimulating hormone (FSH)
-released by the pituitary gland/hypothalamus
-cued by protein
-Stimulates production of ova and sperm
-regulated by hypothalamic hormones
Luteinizing hormone (LH)
-released by the pituitary gland/hypothalamus
-cued by protein
-Stimulates ovaries and testes
-regulated by hypothalamic hormones
Thyroid-stimulating hormone (TSH)
-released by the pituitary gland/hypothalamus
-cued by protein
-stimulated thyroid gland
-regulated by Thyroxine in blood; hypothalamic hormones
Adrenocorticotropic hormone (ACTH)
-released by the pituitary gland/hypothalamus
-cued by protein
-Stimulates adrenal cortex to secrete glucocorticoids
-regulated by glucocorticoids; hypothalamic hormones
Melatonin
-released by the pineal gland
-cued by amine
-Involved in rhythmic activities (daily and seasonal)
-regulated by light/dark cycles
Thyroxine (T4) and triiodothyronine (T3)
-released by the thyroid gland
-cued by amine
-Stimulates and maintain metabolic processes
-regulated by thyroid stimulating hormone (TSH)
Parathyroid hormone (PTH)
-released by the thyroid glands
-cued by peptide
-lowers blood calcium level
-regulated by calcium in blood
Epinephrine and norepinephrine
-released by the adrenal glands
-cued by amines
-Increase blood glucose increase metabolic activities; constrict certain blood vessels
-regulated by the nervous system
Glucocorticoids
-released by the adrenal glands
-cued by steroids
-increase blood glucose
-regulated adrenocorticotropic hormone (ACTH)
Insulin
-released by the pancreas
-cued by protein
-lowers blood glucose
-regulated by glucose in blood
Androgens
-released by the testes
-cued by steroids
-Support sperm formation; development and maintenance of male secondary sex characteristics
-regulated by luteinizing hormone (LH) and Follicle-stimulating hormone (FSH)
Estrogen
-released by the ovaries
-cued by steroids
-Stimulate uterine lining growth; development and maintenance of female secondary sex characteristics
regulated by luteinizing hormone (LH) and Follicle-stimulating hormone (FSH)
