8 - Introduction to Endocrine System Flashcards
This type of signaling is when a cell releases a hormone that binds to that same cell, creating a change.
Autocrine
This type of signaling is when a cell releases a hormone and it binds to a different cell very nearby, creating a change.
Paracrine
This type of signaling is when a cell releases a hormone into the blood stream and it travels to a far away cell to bind, creating a change.
Endocrine
This type of signaling is when a neuron releases a hormone into the blood stream and it travels to a far away cell to bind, creating a change.
Neuroendocrine
Hormone glands are important for the regulation of multiple organs to meet _______ and _______ demands. They play a major role in homeostasis.
Growth
Reproduction
What are the classical endocrine glands?
Hypothalamus Anterior/Posterior Pituitary Thyroid Parathyroid Adrenal Cortex/Medulla Gonads Endocrine Pancreas Placenta (transitory organ)
Hormones are synthesized by endocrine cells within organs whose primary function is not endocrine. There are cells in…
Adipose Heart Liver Kidney GI tract
T/F. Hormones are modified by peripheral conversion (i.e., angiotensin II, Vitamin D).
True
What hormones are within the hypothalamus?
TRH (Thyrotropin-releasing hormone) CRH (Corticotropin-releasing hormone) GnRH (Gonadotrophin-releasing hormone) GHRH (Growth hormone releasing hormone) Somatostatin Dopamine
What hormones are within the anterior pituitary?
TSH (Thyroid-stimulating hormone) FSH (Follicle-stimulating hormone) LH (Luteinizing Hormone) ACTH (Adrenocorticotropic hormone) MSH (Melanocyte-stimulating hormone) Growth hormone Prolactin
What hormones are within the posterior pituitary?
Oxytocin
ADH (Antidiuretic hormone, or Vasopressin)
What hormones are within the thyroid?
T3
T4
Calcitonin
What hormones are within the parathyroid?
PTH (Parathyroid hormone)
What hormones are within the pancreas?
Insulin
Glucagon
What hormones are within the adrenal medulla?
Norepinephrine
Epinephrine
What hormones are within the kidney?
Renin
1,25-Dihydroxycholecalciferol (Calcitriol – Vitamin D)
What hormones are within the adrenal cortex?
Cortisol
Aldosterone
Adrenal androgens
What hormones are within the testes?
Testosterone
What hormones are within the ovaries?
Estradiol
Progesterone
What hormones are within the corpus luteum?
Estradiol
Progesterone
What hormones are within the placenta?
HCG
Estriol
Progesterone
hPL
What are the three general classes of hormones?
Protein/Peptide hormones
Steroid hormones
Amines
Protein/peptide hormones are stored in vesicles until needed. Polypeptides with greater than 100 AAs are called ________, while polypeptides with less than 100 AAs are called _______. They are water-soluble.
Proteins
Peptides
Steroid hormones are synthesized from _________. They are lipid-soluble and not stored in vesicles.
Cholesterol
Amine hormones are derived from…
Tyrosine
Protein/peptide hormones are synthesized in ribosomes as non-functional __________. They are then modified in the ER to _________. From there they go to the golgi where proteolytic enzymes cleave to form the functional hormone. It is then packaged into vesicles.
Preprohormones
Prohormones
An endocrine cell stimulus causes the release of the protein/peptide hormones from their secretory vesicles. What are examples of these stimuli?
Increased intracellular calcium
Increased cAMP and PKA activation
What are examples of steroid hormones?
Cortisol Aldosterone Estradiol Estriol Progesterone Testosterone 1,25-dihydroxycholecalciferol
Steroid hormones are derivatives of cholesterol. Modifications are made via addition or removal of side chains, __________ or aromatization of the steroid nucleus.
Hydroxylation
Where are steroid hormones synthesized and secreted from?
Adrenal cortex
Gonads
Corpus luteum
Placenta
What are the two groups of amine hormones?
Catecholamines
Thyroid hormones
These amine hormones are synthesized in the cytosol and secretory granules. They act through cell-membrane associated receptors.
Catecholamines
Thyroid hormones are synthesized by the thyroid gland and stored as __________ in follicles within the gland. They cross cell membranes and act through nuclear receptors.
Thyroglobulin
Which hormone groups have the greatest plasma half-life from longest to shortest?
Thyroid hormones
Steroid hormones
Protein/Peptide hormones
Neuronal input to an endocrine cell increases or decreases hormonal secretion. What is an example of this?
Sympathetic preganglionic innervation of the adrenal medulla – when stimulated it causes the release of catecholamines into the circulation
What are the two mechanisms for regulation of hormone secretion?
Neural Mechanism
Feedback Mechanisms
Feedback mechanisms are more common than neural mechanisms. Some element of the pathway feeds back, directly or indirectly, on the endocrine gland to change secretion rate. There is both ________ and ________ feedback.
Positive
Negative
Explain positive endocrine feedback, and give an example of it.
Some feature of hormone action causes additional secretion of the hormone. It is uncommon in biologic systems, and leads to an explosive event when it occurs.
Examples are ovulation (estradiol) and labor contractions.
Explain negative endocrine feedback.
Predominant mode of feedback loop among endocrine glands. Some feature of hormone action inhibits further secretion of the hormone. Confer stability by keeping a physiological parameter (i.e., blood glucose level) within a normal range.
This type of negative feedback occurs when a hormone is released from a 3rd tier (peripheral endocrine gland) and feeds back all the way to the 1st (hypothalamus) and 2nd (pituitary) tiers.
Long-Loop feedback
This type of negative feedback occurs when the hormone secreted from the 2nd tier (pituitary) feeds back to the 1st tier (hypothalamus).
Short-Loop feedback
This type of negative feedback occurs when the gland inhibits its own secretion.
Ultra Short-Loop feedback
Descending and ascending neuronal inputs modulate hormonal secretion from the hypothalamus. The major inputs are…
Suprachiasmatic nucleus (SCN)
Pineal Gland
Physiological stresses
This neuronal input to the hypothalamus imposes a circadian rhythm on the secretion of hypothalamic releasing hormones and endocrine axes.
Suprachiasmatic Nucleus (SCN)
This neuronal input to the hypothalamus releases melatonin which feedbacks to the SCN information about day-night.
Pineal Gland
What confers specificity to the hormone actions?
Receptors
Responsiveness of target tissue is expressed in dose-response relationship. The responsiveness can be changed in two ways, which are…
Changing the number of receptors
Changing the affinity of the receptors for the hormone
This is the term for the increase of number of receptors or sensitive of target tissue when hormone levels are low.
Up-regulation
What are the three ways up-regulation occurs?
Increase the synthesis of new receptors
Decrease the degradation of existing receptors
Activating receptors
This is the term for the reduction in receptor numbers or sensitivity of target tissue when hormone levels are high (chronic).
Down-regulation
What are the three ways down-regulation can occur?
Decrease in receptor synthesis
Increased degradation of existing receptors
Inactivating/desensitizing receptors
Describe the signal transduction pathway for the following 1st messenger hormones: ACTH, LH, FSH, TSH, and glucagon.
1st messenger hormone -- Receptor -- G-protein Activated -- Primary effector: Adenylyl Cyclase -- 2nd messenger: cAMP -- Secondary effector: Protein Kinase A (PKA) -- Phosphorylation of proteins -- Physiologic actions
Describe the signal transduction pathway for the following 1st messenger hormones: GnRH, TRH, oxytocin.
1st messenger hormone -- Receptor -- G-protein Activated -- Primary effector: Phospholipase C -- PIP2 divided into DAG and IP3 -- IP3 causes increased Calcium release from ER or SR -- Increased Calcium causes DAG to make increased PKC -- Secondary effector: PKC or Calmodulin -- Physiologic actions
Put the following steps in order for the steroid hormone mechanism of action:
A. Translation produces new proteins for cell processes.
B. The receptor-hormone complex binds to DNA and activates or represses one or more genes.
C. Some steroid hormones also bind to membrane receptors that use second messenger systems to create rapid cellular responses.
D. Most hydrophobic steroids are bound to plasma protein carriers. Only unbound hormones can diffuse into the target cell.
E. Activated genes create new mRNA that moves back to the cytoplasm.
F. Steroid hormone receptors are in the cytoplasm or nucleus.
1) D.
2) F.
3) B.
4) E.
5) A.
6) C.
Guanylyl cyclase activation converts _______ to _______.
GTP
cGMP
cGMP goes on to activate cGMP kinases (like ANP) and this results in the relaxation of vascular smooth muscle via ______ ______.
Nitric Oxide (NO)
***Remember Viagra!
There are two categories of tyrosine kinases, which are…
Receptor tyrosine kinases
Tyrosine kinase-associated receptors
T/F. Receptor tyrosine kinases have intrinsic tyrosine kinase activity. When activated, tyrosine kinase phosphorylated downstream proteins.
True
***The tyrosine kinase is part of the receptor!
Tyrosine kinase-associated receptors are non-covalently bound to proteins that have kinase activity. When activated, the kinase phosphorylates downstream proteins. What is an example of this type of receptor?
Receptors bound to JAK tyrosine kinase
Who is TRH?
Thyrotropin-Releasing Hormone
Peptide hormone from Hypothalamus
Stimulates secretion of TSH and prolactin
Who is CRH?
Corticotropin-Releasing Hormone
Peptide hormone from Hypothalamus
Stimulates secretion of ACTH
Who is GnRH?
Gonadotropin-Releasing Hormone
Peptide hormone from Hypothalamus
Stimulates secretion of LH and FSH
Who is SRIF?
Somatostatin or Somatotropin Release-Inhibiting Hormone
Peptide hormone from Hypothalamus
Inhibits secretion of growth hormone
Who is PIF?
Dopamine or Prolactin-Inhibiting Hormone
Amine hormone from Hypothalamus
Inhibits secretion of prolactin
Who is GHRH?
Growth Hormone-Releasing Hormone
Peptide hormone from Hypothalamus
Stimulates secretion of growth hormone
Who is TSH?
Thyroid-Stimulating Hormone
Peptide hormone from Anterior Pituitary
Stimulates synthesis and secretion of thyroid hormones
Who is FSH?
Follicle-Stimulating Hormone
Peptide hormone from Anterior Pituitary
- Stimulates sperm maturation in Sertoli cells of testes
- Stimulates follicular development and estrogen synthesis in ovaries.
Who is LH?
Luteinizing Hormone
Peptide hormone from Anterior Pituitary
- Stimulates testosterone synthesis in Leydig cells of testes
- Stimulates ovulation, formation of corpus luteum, estrogen and progesterone synthesis in ovaries
Who is Growth Hormone?
Peptide hormone from Anterior Pituitary
Stimulates protein synthesis and overall growth
Who is Prolactin?
Peptide hormone from Anterior Pituitary
Stimulates milk production and secretion in breast
Who is ACTH?
Adrenocorticotropic Hormone
Peptide hormone from Anterior Pituitary
Stimulates synthesis and secretion of adrenal cortical hormones (cortisol, androgens, and aldosterone)
Who is MSH?
Melanocyte-Stimulating Hormone
Peptide hormone from Anterior Pituitary
Stimulates melanin synthesis
Who is Oxytocin?
Peptide hormone from Posterior Pituitary
Stimulates milk ejection from breasts and uterine contractions
Who is Vasopressin or ADH?
Antidiuretic Hormone
Peptide hormone from Posterior Pituitary
Stimulates water reabsorption in principal cells of collecting ducts and constriction of arterioles
Who is T3 and T4?
Triiodothyronine and Thyroxine
Amine hormones from Thyroid
Stimulates --- Skeletal growth Oxygen consumption Heat production Protein, fat, and carb utilization Perinatal maturation of the CNS
Who is Calcitonin?
Peptide hormone from Thyroid
Decreases serum Calcium
Who is PTH?
Parathyroid Hormone
Peptide hormone from Parathyroid
Increases serum Calcium
Who is Cortisol?
Glucocorticoid
Steroid hormone from Adrenal Cortex
Stimulates gluconeogenesis
Inhibits inflammatory response
Suppresses immune response
Enhances vascular responsiveness to catecholamines
Who is Aldosterone?
Mineralocorticoid
Steroid hormone from Adrenal Cortex
Increases renal Na+ reabsorption, K+ secretion, and H+ secretion
Who is DHEA and Adrenal Androgens?
Dehydroepiandrosterone and Androstenedione
Steroid hormones from Adrenal Cortex
Stimulates spermatogenesis
Stimulates male secondary sex characteristics
Who is Testosterone?
Steroid hormone from Testes
Stimulates spermatogenesis
Stimulates male secondary sex characteristics
Who is Estradiol?
Steroid hormone from Ovaries and Corpus Luteum
- Stimulates growth and development of female reproductive system, follicular phase of menstrual cycle, development of breasts, and prolactin secretion
- Maintains pregnancy
Who is Progesterone?
Steroid hormone from Ovaries, Corpus Luteum, and Placenta
Stimulates luteal phase of menstrual cycle
Maintains pregnancy
Who is HCG?
Human Chorionic Gonadotropin
Peptide hormone from Placenta
Stimulates estrogen and progesterone synthesis in Corpus Luteum of early pregnancy
Who is hPL or Human Chorionic Somatomammotropin?
Human Placental Lactogen
Peptide hormone from Placenta
Has growth hormone-like and prolactin-like actions during pregnancy
Who is Estriol?
Steroid hormone from Placenta
- Stimulates growth and development of female reproductive system, follicular phase of menstrual cycle, developments of breasts, and prolactin secretion
- Maintains pregnancy
***Same actions as Estradiol
Who is Insulin?
Peptide hormone from Beta cells in Pancreas
Decreases blood glucose
Who is Glucagon?
Peptide hormone from Alpha cells in Pancreas
Increases blood glucose
Who is Renin?
Peptide hormone from Kidney
Catalyzes conversion of Angiotensinogen to Angiotensin I
Who is 1,25-Dihydroxycholecalciferol (Vitamin D)?
Steroid hormone from Kidney
Increases intestinal absorption of Calcium
Bone mineralization
Who is Norepinephrine and Epinephrine?
Amine hormones from Adrenal Medulla
Sympathetic nervous system actions
What hormones utilize the Tyrosine Kinase mechanism?
Insulin
IGF-1
Growth hormone
Prolactin
What hormones utilize the Phospholipase C mechanism (IP3/DAG)?
GnRH TRH GHRH Angiotensin II ADH (V1 receptor) Oxytocin Alpha-1 Receptors
What hormones utilize the Adenylyl Cyclase mechanism (cAMP)?
ACTH LH FSH TSH ADH (V2 receptor) HCG MSH CRH Calcitonin PTH Glucagon Beta-1 and Beta-2 receptors
What hormones utilize the steroid hormone mechanism?
Glucocorticoids Estrogen Progesterone Testosterone Aldosterone Thyroid hormones 1,25-Dihydroxycholecalciferol
