Chapter 12- Endocrinology Flashcards
What do endocrine glands do?
How are exocrine glands different
Secrete chemical substances called hormones directly into the circulatory system.
Exocrine= secretion not direct, has to be transported by ducts.
Glands and organs that synthesize or secrete hormones are:
pituitary, hypothalamus, thyroid, parathyroids, adrenals, pancreas, testes, ovaries, pineal, kidneys, gastrointestinal glands, heart, and thymus.
What is the specificity of hormonal action determined by?
The presence of specific receptors on or in the target cells.
Where are the adrenal glands situation what what do they consist of?
They are situated on the top of the kidneys and consist of the adrenal cortex and the adrenal medulla
ACTH
adrenocorticotropic hormone- produced by adrenal pituitary. Stimulates the production of adrenocortical steroids (collective name for more than two dozen hormones, also known as corticosteroids).
Transcortins
What corticosteroids bind to in the bloodstream.
How do corticosteroids exert their mechanism?
They determine which genes are transcribed in the nuclei of their target cells and at which particular rate. Then they change the nature and given concentration of the enzyme, which will affect cellular metabolism.
Glucocorticoids
Cortisol and cortisone– involved in glucose regulation and protein metabolism.
Increase plasma glucose levels and are antagonist to the effect of insulin
How do glucocorticoids raise blood glucose levels?
They promote protein breakdown and gluconeogenesis and decrease protein synthesis.
What do glucocorticoids release?
Amino acids from skeletal muscles and lipids from adipose tissue.
Also promote peripheral use of lipids and have anti-inflammatory effects
Mineralocorticoids
Aldosterone
Regulate plasma levels of sodium and potassium, and the total extracellular water volume.
What does aldosterone cause?
Active reabsorption of sodium and passive reabsorption of water in the nephron of the kindey.
What do the affects of aldosterone result in?
An increase in blood volume and blood pressure.
What does excess production of aldosterone cause?
Excess retention of water- hypertension
What are mineralocorticoids stimulated by?
Angiotensin II
What are mineralocorticoids stimulated by?
ANT (atrial natriuretic peptide)
Cortical sex hormones secreted by adrenal cortex
Secretes small quantities of androgens in both men and women
Effect not great in men
In women, can lead to masculinizing effects
What does the adrenal medulla produce?
Epinephrine (adrenaline) and norepinephrine (noradrenaline).
Catecholamines
Amino-acid derived compounds to which both epinephrine and norepinephrine belong to.
Epinephrine
Increases conversion of glycogen to glucose in liver and muscle tissue, causing an increase in blood glucose levels.
INCREASE in the basal metabolic rate.
Both epinephrine and norepinephrine cause:
Increase the rate and strength of the heartbeat
Constrict and dilate blood vessel in increase supply to:
skeletal muscles
heart
brain
decrease supply to:
kidneys
skin
digestive tract
Also promotes the release of lipids by adipose tissue.
Effects of epinephrine and norepinephrine are known as the :
flight or fight response
Effects of epinephrine and norepinephrine are elicited by:
the sympathetic nervous stimulation to stress
True or false: both epinephrine and norepinephrine are neurotransmitters
True
they are both proteins used by neurons to transmit signals- stimulated by sympathetic preganglionic fibers.
What is the pituitary and where is it located?
Small trilobed gland lying at the base of the brain. Hangs below the hypothalamus and is connected by a slender cord known as the infundibulum.
What are the two main lobes of the pituitary? Are they functionally distinct?
Anterior and Posterior.
Yes they are functionally distinct.
Anterior pituitary synthesizes (2):
Direct hormones
Directly stimulate their target organs
Tropic hormones
Stimulate other endocrine glands to rlease hormones
What are hormone secretions of the anterior pituitary regulated by?
Hypothalamic secretions called releasing/ inhibiting hormones or factors.
What are examples of direct hormones?
Growth hormone (GH, somatotropin) Prolactin
Growth hormone
Promotes bone and muscle growth. Also promotes protein synthesis and lipid mobilization and catabolism.
What can GH deficiency in children cause? What does over production cause.
Dwarfism (growth stunt)
Gigantism
What can GH over production in adults cause?
Acromegaly: a disorder characterized by disproportionate overgrowth of bone, localized especially in the skull, jaw, feet and hands.
Prolactin
Stimulates milk production and secretion in female mammary glands
What are examples of tropic hormones?
Adrenocorticotropic hormone (ACTH) Thyroid-stimulating hormone (TSH) Luteinizing hormone (LH) Follicle-stimulating hormone (FSH) Malanocyte-stimulating hormone (MSH) Endorphins
ACTH
Adrenocorticotropic hormone. Stimulates the adrenal cortex to synthesize and secrete glucocorticoids and is regulated by corticotrophin-releasing factor (CRF)
TSH
Thyroid-stimulating hormone. Stimualtes the thyroid gland to synthesize and release thyroid hormones, including thyroxin.
LH
Luteinizing hormone.
Women: stimulates ovulation and formation of corpus luteum.
Regulates progesterone secretion.
Men: Stimulates interstitial cells of the testes to synthesize testosterone.
FSH
Follicle stimulating hormone.
Women: causes maturation of ovarian follicles that begin secreting estrogen
Men: FSH stimulates maturation of the seminiferous tubules and sperm production.
MSH
Melanocyte-stimulating hormone. Secreted by the intermediate lobe of the pituitary. Function unclear in humans, in frogs, causes darkening of skin.
Endorphins
Neurotransmitters that have pain-relieving properties
Posterior pituitary (neurohypophysis)
Does not synthesize hormones- stores and releases peptide hormones oxytocin and ADH
Oxytocin and ADH are stimulated and produced by?
Stimulated by action potentials descending from the hypothalamus and produced by the neurosecretory cells of the hypothalamus
Oxytocin
Secreted during childbirth- increases muscle contraction
-Also induced by suckling, stimulates milk secretion
ADH
Antidiuretic hormone (vasopressin) Increases permeability of nephron's collecting duct to water
promotes water reabsorption, increases BO.
When is ADH secreted?
When plasma osmolarity increases as sensed by osmoreceptors in the hypothalamus or when blood volume decreases, as sensed by baroreceptors in the circulatory system.
What is hypothalamus and where is it located?
Part of the forebrain and is located directly above the pituitary gland.
What does the hypothalamus receive?
Neural transmissions from other parts of the brain and from peripheral nerves that trigger specific responses from its neurosecretory cells.
Neurosecretory cells.
regulate pituitary gland secretions via negative feedback mechanisms and through the actions of inhibiting and releasing hormones.
Hypothalamic-releasing hormones
Stimulate or inhibit the secretions of the anterior pituitary.
GnRH
Stimulates the anterior pituitary to secrete FSH or LH
Where are releasing hormones secreted into?
The hypothalamic-hypophyseal portal system
hypothalamic-hypophyseal portal system
Circulatory pathway, blood from capillary bed in the hypothalamus flows through a portal vein and into the anterior pituitary, where it diverges into a 2nd capillary network
When plasma levels of adrenal cortical hormones drop, hypothalamic cells release?
ACTH-releasing factor via negative feedback into the portal vein. When the plasma concentration of corticosteroids exceeds the normal plasma level, the steroids themselves exert an inhibitory effect on the hypothalamus