Final Flashcards
The endocrine system:
The endocrine and nervous systems are the major controllers
of the flow of information between different cells and tissues.
Endocrine and neurotransmitter cells synthesize hormones and
release them by specialized secretory pathways.
The hormones act on the producer cell (autocrine) or on neighboring
target cells including neurotransmitter cells, without entering the circulation
(juxtacrine and paracrine).
They may go to the target cell through the circulation (hormonal).
Neurotransmitter cells release neurotransmitters from nerve terminals.
The same neurotransmitters can be released to act as hormones
through the synaptic junctions or directly by the cell.
The endocrine system:
The endocrine and nervous systems are the major controllers
of the flow of information between different cells and tissues.
Endocrine and neurotransmitter cells synthesize hormones and
release them by specialized secretory pathways.
The hormones act on the producer cell (autocrine) or on neighboring
target cells including neurotransmitter cells, without entering the circulation
(juxtacrine and paracrine).
They may go to the target cell through the circulation (hormonal).
Neurotransmitter cells release neurotransmitters from nerve terminals.
The same neurotransmitters can be released to act as hormones
through the synaptic junctions or directly by the cell.
Chemical classification of hormones
Hormone synthesis:
Protein hormone production often does not require special machinery.
Growth hormone, prolactin, and PTH are produced similarly to other secreted proteins.
Some Peptide hormones (insulin, ACTH, and glucagons) are produced by cleavage of a larger protein.
Other hormones with specific structures are generated by specialized enzymes.
Thyroid hormone is produced by iodination and coupling of tyrosine residues
of thymoglobulin,
Steroid hormones are produced from cholesterol.
Chemical classification of hormones
Hormone synthesis:
Protein hormone production often does not require special machinery.
Growth hormone, prolactin, and PTH are produced similarly to other secreted proteins.
Some Peptide hormones (insulin, ACTH, and glucagons) are produced by cleavage of a larger protein.
Other hormones with specific structures are generated by specialized enzymes.
Thyroid hormone is produced by iodination and coupling of tyrosine residues
of thymoglobulin,
Steroid hormones are produced from cholesterol.
Mechanisms of hormone secretion:
Hormones: are released by endocrine glands and transported through the
bloodstream to tissues where they bind to specific receptor molecules and
regulate target tissue function.
Endocrine: It is internal secretion of hormones into the circulation to convey
information to target cells.
Exocrine: It is secretion outside the circulation, e.g., sweat glands or ducts that lead into the gastrointestinal tract.
Paracrine: When hormones act on neighboring hormone-producing cells or non- hormone-producing cells, e.g.: actions of sex steroids in the ovary.
Autocrine: When hormone acts on receptors located on the same cell.
Autocrine actions may be important in promoting unregulated growth of cancer cells.
Intracrine: Hormones can also act inside the cell without being released, an
intracrine effect.
Example: insulin can inhibit its own release from pancreatic islet B cells
and somatostatin can inhibit its own release from pancreatic D cells.
Mechanisms of hormone secretion:
Hormones: are released by endocrine glands and transported through the
bloodstream to tissues where they bind to specific receptor molecules and
regulate target tissue function.
Endocrine: It is internal secretion of hormones into the circulation to convey
information to target cells.
Exocrine: It is secretion outside the circulation, e.g., sweat glands or ducts that lead into the gastrointestinal tract.
Paracrine: When hormones act on neighboring hormone-producing cells or non- hormone-producing cells, e.g.: actions of sex steroids in the ovary.
Autocrine: When hormone acts on receptors located on the same cell.
Autocrine actions may be important in promoting unregulated growth of cancer cells.
Intracrine: Hormones can also act inside the cell without being released, an
intracrine effect.
Example: insulin can inhibit its own release from pancreatic islet B cells
and somatostatin can inhibit its own release from pancreatic D cells.
Hormone interactions
Synergistic effects
When two or more hormones work together to produce a particular result, their effects are said to be synergistic.
Example: epinephrine and norepinephrine on the heart, each hormones separately produces an increase in cardiac rate.
Permissive effects
A hormone have a permissive effect on the action of a second hormone when it enhances the responsiveness of a target organ to the second hormone or when it increases the activity of the second hormone.
Example: Cortisol and catecholamines
Antagonistic effects
In some situations, the actions of one hormone antagonize the effects of another.
Example: insulin and glucagon.
Hormone interactions
Synergistic effects
When two or more hormones work together to produce a particular result, their effects are said to be synergistic.
Example: epinephrine and norepinephrine on the heart, each hormones separately produces an increase in cardiac rate.
Permissive effects
A hormone have a permissive effect on the action of a second hormone when it enhances the responsiveness of a target organ to the second hormone or when it increases the activity of the second hormone.
Example: Cortisol and catecholamines
Antagonistic effects
In some situations, the actions of one hormone antagonize the effects of another.
Example: insulin and glucagon.
Mechanism of action of hormones:
Hormones released by endocrine glands and transported through the
bloodstream to tissues by binding to specific receptor and regulate target
tissue function.
Some hormones bind cell surface receptors,
e.g., insulin, growth hormone, prolactin.
Some hormones bind to intracellular receptors that act in the nucleus,
e.g., steroids, thyroid hormone.
Mechanism of action of hormones:
Hormones released by endocrine glands and transported through the
bloodstream to tissues by binding to specific receptor and regulate target
tissue function.
Some hormones bind cell surface receptors,
e.g., insulin, growth hormone, prolactin.
Some hormones bind to intracellular receptors that act in the nucleus,
e.g., steroids, thyroid hormone.
1- G-protein coupled receptors ( Seven-transmembrane domain receptors)
G-proteins are guanosine triphosphate (GTP)-binding proteins that couple
receptors to adjacent effector molecules.
Are used in the adenylate cyclase, Ca2+_ Calmodulin, and inositol 1,4,5-triphosphate
(IP3) second messenger system.
*Binding of ligand to the receptor activates G proteins, which in turn act on effectors
such as adenylyl cyclase and phospholipase C and in that way initiate production of
second messengers with resultant influences on cell organization, or transcription.
They have intrinsic GTPase activity
they have 3 subunits: α, β, and γ
The α subunit can bind GDP or GTP. When GDP is bound to α subunit, the G protein
is inactive. When GTP is bound, the G protein is active.
G proteins are either stimulatory (Gs) or inhibitory (Gi). Stimulatory or inhibitory activity
resides in the α subunits, which are accordingly called (αs) and (αi).
*Mediate actions of catecholamines, prostaglandins, ACTH, glucagons, parathyroid hormone (PTH), thyroid-stimulating hormone (TSH), and others.
1- G-protein coupled receptors ( Seven-transmembrane domain receptors)
G-proteins are guanosine triphosphate (GTP)-binding proteins that couple
receptors to adjacent effector molecules.
Are used in the adenylate cyclase, Ca2+_ Calmodulin, and inositol 1,4,5-triphosphate
(IP3) second messenger system.
*Binding of ligand to the receptor activates G proteins, which in turn act on effectors
such as adenylyl cyclase and phospholipase C and in that way initiate production of
second messengers with resultant influences on cell organization, or transcription.
They have intrinsic GTPase activity
they have 3 subunits: α, β, and γ
The α subunit can bind GDP or GTP. When GDP is bound to α subunit, the G protein
is inactive. When GTP is bound, the G protein is active.
G proteins are either stimulatory (Gs) or inhibitory (Gi). Stimulatory or inhibitory activity
resides in the α subunits, which are accordingly called (αs) and (αi).
*Mediate actions of catecholamines, prostaglandins, ACTH, glucagons, parathyroid hormone (PTH), thyroid-stimulating hormone (TSH), and others.
G-protein coupled receptors ( Seven-transmembrane domain receptors)
They contain a surface-exposed amino-terminal domain followed by seven
transmembrane domains that span the lipid bilayer and a hydrophilic carboxyl
terminal domain that lies in the cytoplasm, these receptors are coupled to the
guanylyl nucleotide binding G proteins.
G-protein coupled receptors ( Seven-transmembrane domain receptors)
They contain a surface-exposed amino-terminal domain followed by seven
transmembrane domains that span the lipid bilayer and a hydrophilic carboxyl
terminal domain that lies in the cytoplasm, these receptors are coupled to the
guanylyl nucleotide binding G proteins.
2- Growth factor receptors:
contains an amino terminal surface exposed ligand-binding domain, a single
membrane-spanning domain, and a carboxyl terminal catalytic domain.
Growth factor receptors, including those for insulin, IGF and EGF, possess tyrosine kinase activity. Ligand binding results to activation of tyrosine kinase, and
autophosphorylation.
2- Growth factor receptors:
contains an amino terminal surface exposed ligand-binding domain, a single
membrane-spanning domain, and a carboxyl terminal catalytic domain.
Growth factor receptors, including those for insulin, IGF and EGF, possess tyrosine kinase activity. Ligand binding results to activation of tyrosine kinase, and
autophosphorylation.
3- Cytokine receptors: are part of a receptors that also mediate the actions of growth hormone (GH). This class contains a surface-exposed amino terminal domain that binds ligand, a single membrane-spanning domain, and a carboxyl terminal effector domain. GH receptors lack a tyrosine kinase domain, when GH bind to the receptor in the extracellular space (their mechanism of action is not perfectly understood ) but appears to involve the participation of signaling intermediates, like JAK2, a protein that possesses intrinsic tyrosine kinase activity. The association of JAK2 with the liganded GH receptor leads to change in JAK2 and activation of its tyrosine kinase catalytic activity. This, in turn, triggers downstream signaling events.
3- Cytokine receptors: are part of a receptors that also mediate the actions of growth hormone (GH). This class contains a surface-exposed amino terminal domain that binds ligand, a single membrane-spanning domain, and a carboxyl terminal effector domain. GH receptors lack a tyrosine kinase domain, when GH bind to the receptor in the extracellular space (their mechanism of action is not perfectly understood ) but appears to involve the participation of signaling intermediates, like JAK2, a protein that possesses intrinsic tyrosine kinase activity. The association of JAK2 with the liganded GH receptor leads to change in JAK2 and activation of its tyrosine kinase catalytic activity. This, in turn, triggers downstream signaling events.
4- Ligand-regulated transporters (Guanylyl cyclase receptor)
can bind ligands and respond by opening the channel for ion flow.
In this case, the ion flux acts the second messenger, it increases nitric oxide synthases (NOS) , it leads to stimulation of soluble guanylyl cyclase (GC) activity. Subsequent elevations in cGMP activate cGMP -dependent protein kinase (PKG) and promote vasorelaxation.
4- Ligand-regulated transporters (Guanylyl cyclase receptor)
can bind ligands and respond by opening the channel for ion flow.
In this case, the ion flux acts the second messenger, it increases nitric oxide synthases (NOS) , it leads to stimulation of soluble guanylyl cyclase (GC) activity. Subsequent elevations in cGMP activate cGMP -dependent protein kinase (PKG) and promote vasorelaxation.
Nuclear receptors
Nuclear receptors mediate actions of steroid hormones, vitamin D, thyroid hormones,
retinoids, fatty acids and bile acids.
Nuclear receptors control gene expression by binding to DNA response elements
in the promoters of target genes or to other transcription factors.
Nuclear receptor is composed of three domains: 1- The amino terminal domain is the most variable and mediates effects on transcription. 2- The DNA-binding domain 3-The carboxyl terminal domain is also well conserved and mediates ligand binding, dimerization, and effect on transcription.
Nuclear receptors
Nuclear receptors mediate actions of steroid hormones, vitamin D, thyroid hormones,
retinoids, fatty acids and bile acids.
Nuclear receptors control gene expression by binding to DNA response elements
in the promoters of target genes or to other transcription factors.
Nuclear receptor is composed of three domains: 1- The amino terminal domain is the most variable and mediates effects on transcription. 2- The DNA-binding domain 3-The carboxyl terminal domain is also well conserved and mediates ligand binding, dimerization, and effect on transcription.
Steroid hormone and thyroid hormone mechanism:
1- Steroid or thyroid hormones diffuse across
the cell membrane of target cells and bind to
a cytosolic receptor and then to a nuclear receptor.
Binding to the nuclear receptor causes a
conformational change in the receptor,
which exposes a DNA-binding domain.
2- In the nucleus, the DNA-binding domain on
the receptor interacts with the hormone
regulatory elements of specific DNA.
Transcription is initiated and results in the
production of new mRNA.
3- mRNA is translated in the cytoplasm and
results in the production of specific proteins
that have physiologic actions.
Steroid hormone and thyroid hormone mechanism:
1- Steroid or thyroid hormones diffuse across
the cell membrane of target cells and bind to
a cytosolic receptor and then to a nuclear receptor.
Binding to the nuclear receptor causes a
conformational change in the receptor,
which exposes a DNA-binding domain.
2- In the nucleus, the DNA-binding domain on
the receptor interacts with the hormone
regulatory elements of specific DNA.
Transcription is initiated and results in the
production of new mRNA.
3- mRNA is translated in the cytoplasm and
results in the production of specific proteins
that have physiologic actions.
Chemical substance which is secreted by endocrine gland which carries some signal to target cell.
Chemical substance which is secreted by endocrine gland which carries some signal to target cell.
Endocrine
Secreted into blood stream
Endocrine
Secreted into blood stream
Hormone requires specific receptor
The type of receptor depends on the type of hormone
When hormone binds to its receptor it leads to stimulation of intracellular molecules in target cell
After activation of molecules then that target cell shows physiologic reaction to the hormone
Hormone requires specific receptor
The type of receptor depends on the type of hormone
When hormone binds to its receptor it leads to stimulation of intracellular molecules in target cell
After activation of molecules then that target cell shows physiologic reaction to the hormone
In general there are two groups of hormones
Protein hormones(amino acid/poly peptide hormones) which binds to cell surface receptor
On cell membrane
Protein can not pass through cell membrane since the structure of cell membrane is
In general there are two groups of hormones
Protein hormones(amino acid/poly peptide hormones) which binds to cell surface receptor
On cell membrane
Protein can not pass through cell membrane since the structure of cell membrane is
lipid bilayer Hormones which bind to nuclear receptor Located inside the nucleus Steroid hormones Precursor is cholesterol Aldosterone and cortisol Sex hormones(testosterone, androgen, progesterone, estrogen) Vitamin D Precursor is cholesterol T3 and T4 Precursor is iodine These can easily pass through cell membrane and they bind into the nuclear receptor
lipid bilayer Hormones which bind to nuclear receptor Located inside the nucleus Steroid hormones Precursor is cholesterol Aldosterone and cortisol Sex hormones(testosterone, androgen, progesterone, estrogen) Vitamin D Precursor is cholesterol T3 and T4 Precursor is iodine These can easily pass through cell membrane and they bind into the nuclear receptor
Different types of hormones
Exocrine glands
Sweat glands, salivary glands
Anything with a duct that open into a cavity and the contents are released into it
Endocrine
Into blood stream
Paracrine hormones
First hormone controls/regulates neighboring cell hormone secretion
Somatostatin in GI tract inhibits other hormone gastric secretion
In hypothalamus inhibits growth hormone secretion
(clinical point) synthetic somatostatin is used for treatment of gigantism because it blocks the growth hormone
Autocrine hormones
Hormone controls its own secretion
Insulin gives itself feedback
Different types of hormones
Exocrine glands
Sweat glands, salivary glands
Anything with a duct that open into a cavity and the contents are released into it
Endocrine
Into blood stream
Paracrine hormones
First hormone controls/regulates neighboring cell hormone secretion
Somatostatin in GI tract inhibits other hormone gastric secretion
In hypothalamus inhibits growth hormone secretion
(clinical point) synthetic somatostatin is used for treatment of gigantism because it blocks the growth hormone
Autocrine hormones
Hormone controls its own secretion
Insulin gives itself feedback
(clinical point) synthetic somatostatin is used for treatment of gigantism because it blocks the growth hormone
(clinical point) synthetic somatostatin is used for treatment of gigantism because it blocks the growth hormone
(hormone interactions)
Sometimes two different hormones have similar functions
Glucagon and cortisol maintain the blood glucose level but different hormones
Sometimes some hormones can stimulate or inhibit other secretions
Prolactin suppresses the sex hormones to prevent menstruation during pregnancy
Antagonist
When hormone or synthetic hormone or drug recognizes natural hormone receptor then it binds to that receptor which blocks the natural hormone effect
Propranolol is beta 1 blocker
Antagonist to beta 1
(hormone interactions)
Sometimes two different hormones have similar functions
Glucagon and cortisol maintain the blood glucose level but different hormones
Sometimes some hormones can stimulate or inhibit other secretions
Prolactin suppresses the sex hormones to prevent menstruation during pregnancy
Antagonist
When hormone or synthetic hormone or drug recognizes natural hormone receptor then it binds to that receptor which blocks the natural hormone effect
Propranolol is beta 1 blocker
Antagonist to beta 1
Agonist
Synthetic hormone recognizes the natural hormone receptor and acts as the hormone
Synthetic growth hormone replacement for dwarfism
Replace the growth hormone to encourage growth
Agonist
Synthetic hormone recognizes the natural hormone receptor and acts as the hormone
Synthetic growth hormone replacement for dwarfism
Replace the growth hormone to encourage growth
Slide 6 mechanism of action
- When a ligand or hormone binds to its specific receptor
- Activates intracellular molecules
o Effector – first activated, mostly is g protein(alpha, beta and gamma subunits)
- After activation of effector then second messenger is activated
o Activation of some enzymes
o Phospholipids C
- Sometimes it leads to inhibition of second messenger
- This leads to activation of intracellular energy(CAMP – cyclic adenosine monophosphate)
- The target cell shows reaction to that hormone
- Intracellular and nuclear can be interchanged in wording
Slide 6 mechanism of action
- When a ligand or hormone binds to its specific receptor
- Activates intracellular molecules
o Effector – first activated, mostly is g protein(alpha, beta and gamma subunits)
- After activation of effector then second messenger is activated
o Activation of some enzymes
o Phospholipids C
- Sometimes it leads to inhibition of second messenger
- This leads to activation of intracellular energy(CAMP – cyclic adenosine monophosphate)
- The target cell shows reaction to that hormone
- Intracellular and nuclear can be interchanged in wording
Slide 7 - For test o Know the underlined o Adenylate cyclase to GTPase activity - The cell surface receptors have 4 types of receptors for proteins o G protein coupled receptors o Growth factor receptor o Cytokine receptors o Ligand-regulated transporters - For test o Know catecholamines Same as adrenaline and noradrenaline
Slide 7 - For test o Know the underlined o Adenylate cyclase to GTPase activity - The cell surface receptors have 4 types of receptors for proteins o G protein coupled receptors o Growth factor receptor o Cytokine receptors o Ligand-regulated transporters - For test o Know catecholamines Same as adrenaline and noradrenaline
Slide 9
- Insulin, IGF, and EGF
- The second messenger for growth factor is Tyrosine kinase
- Insulin can bind the growth factor receptor
Slide 9
- Insulin, IGF, and EGF
- The second messenger for growth factor is Tyrosine kinase
- Insulin can bind the growth factor receptor
Slide 11
- Cytokine receptors are for growth factors
- JAK2 and tyrosine kinase
Slide 11
- Cytokine receptors are for growth factors
- JAK2 and tyrosine kinase
Slide 12
- Nitric oxide and ANP(atrial natriotic peptide) bind
o ANP is vasorelaxator which decreases blood pressure and is active when blood pressure is high
Slide 12
- Nitric oxide and ANP(atrial natriotic peptide) bind
o ANP is vasorelaxator which decreases blood pressure and is active when blood pressure is high
Slide 13
Nuclear receptor is not part of the 4 above
- One side is for ligand binding site and the other part is for the DNA binding site
- Steroid hormones, vitamin D
Slide 13
Nuclear receptor is not part of the 4 above
- One side is for ligand binding site and the other part is for the DNA binding site
- Steroid hormones, vitamin D
o (clinical point) any deficiency or over production of precursor or hormone again leads to hormonal disorder
Deficiency of cholesterol leads to deficiency of sex hormones = infertility
Deficiency of testosterone leads to depression(controls mood)
o (clinical point) any deficiency or over production of precursor or hormone again leads to hormonal disorder
Deficiency of cholesterol leads to deficiency of sex hormones = infertility
Deficiency of testosterone leads to depression(controls mood)
o (clinical point) any modification or change/mutation to receptor structure leads to hormonal disorder such as
Type 2 diabetes
o (clinical point) any modification or change/mutation to receptor structure leads to hormonal disorder such as
Type 2 diabetes
The differences between cell surface receptor and nuclear receptor hormones
- Cell surface = protein
- Nuclear = steroid hormones
- Protein hormones should bind to cell membrane receptor but steroid hormone should bind to nuclear receptor hormone
- Steroid hormones need a carrier protein which transports the hormone to the nucleus but protein hormones freely circulate in blood stream and don’t need a carrier protein
- Duration of action for steroid hormone is longer than protein hormone because
o Needs to dissociate from its carrier protein which takes some time
- Protein hormones are hydrophilic(lipophobic) and can not pass through the cell membrane
o Steroid hormones are lipophilic and can pass through the cell membrane
- Precursors
o Protein hormone – amino acid
o Steroid – cholesterol
o (clinical point) any modification or change/mutation to receptor structure leads to hormonal disorder such as
Type 2 diabetes
o (clinical point) any deficiency or over production of precursor or hormone again leads to hormonal disorder
Deficiency of cholesterol leads to deficiency of sex hormones = infertility
Deficiency of testosterone leads to depression(controls mood)
The differences between cell surface receptor and nuclear receptor hormones
- Cell surface = protein
- Nuclear = steroid hormones
- Protein hormones should bind to cell membrane receptor but steroid hormone should bind to nuclear receptor hormone
- Steroid hormones need a carrier protein which transports the hormone to the nucleus but protein hormones freely circulate in blood stream and don’t need a carrier protein
- Duration of action for steroid hormone is longer than protein hormone because
o Needs to dissociate from its carrier protein which takes some time
- Protein hormones are hydrophilic(lipophobic) and can not pass through the cell membrane
o Steroid hormones are lipophilic and can pass through the cell membrane
- Precursors
o Protein hormone – amino acid
o Steroid – cholesterol
o (clinical point) any modification or change/mutation to receptor structure leads to hormonal disorder such as
Type 2 diabetes
o (clinical point) any deficiency or over production of precursor or hormone again leads to hormonal disorder
Deficiency of cholesterol leads to deficiency of sex hormones = infertility
Deficiency of testosterone leads to depression(controls mood)
First signal comes from hypothalamus
Second signal the hypophyseal gland
First signal comes from hypothalamus
Second signal the hypophyseal gland
The pituitary gland has 3 lobes
Anterior, posterior, and inter media lobe
Hypothalamal-pituitary portal system connects anterior and posterior
The pituitary gland has 3 lobes
Anterior, posterior, and inter media lobe
Hypothalamal-pituitary portal system connects anterior and posterior
Hypothalamus connects to posterior pituitary is by axon not blood vessel
The embryonic origin of posterior lobe is from the ectoderm which gives signals to CNS and PNS
This is why it is axon instead of blood vessel based like anterior pituitary
Hypothalamus connects to posterior pituitary is by axon not blood vessel
The embryonic origin of posterior lobe is from the ectoderm which gives signals to CNS and PNS
This is why it is axon instead of blood vessel based like anterior pituitary
Hypothalamus contains some nuclei These nuclei secrete type types of hormones - Releasing hormones and inhibit releasing hormone o RH and IRH o R from hypothalamus releasing o S from anterior pituitary lobe Stimulating
Hypothalamus contains some nuclei These nuclei secrete type types of hormones - Releasing hormones and inhibit releasing hormone o RH and IRH o R from hypothalamus releasing o S from anterior pituitary lobe Stimulating
Hypothalmus controls
- Endocrine system
- Appetite
- Memory
- Learning
- Emotional sexual behaviors
- Partially sympathetic and parasympathetic
- Body temperature
Hypothalmus controls
- Endocrine system
- Appetite
- Memory
- Learning
- Emotional sexual behaviors
- Partially sympathetic and parasympathetic
- Body temperature
(clinical point)
25 year old male has tumor in hypothalamic nuclei what signs/symptoms if the surgeon can not remove the tumor?
Obesity
Sleep disorder
(clinical point)
25 year old male has tumor in hypothalamic nuclei what signs/symptoms if the surgeon can not remove the tumor?
Obesity
Sleep disorder
Connections of the Hypothalamus with the Hypophysis cerebri:
The hypothalamus is connected to the hypophysis cerebri (pituitary gland) by two ways:
1- nerve fibers from the supraoptic and paraventricular nuclei to posterior pituitary lobe.
2- long and short portal blood vessels connecting sinusoids in the median eminence and
infundibulum with capillary plexus in the anterior lobe of the hypophysis.
These pathways enables the hypothalamus to influence the endocrine glands activities.
Connections of the Hypothalamus with the Hypophysis cerebri:
The hypothalamus is connected to the hypophysis cerebri (pituitary gland) by two ways:
1- nerve fibers from the supraoptic and paraventricular nuclei to posterior pituitary lobe.
2- long and short portal blood vessels connecting sinusoids in the median eminence and
infundibulum with capillary plexus in the anterior lobe of the hypophysis.
These pathways enables the hypothalamus to influence the endocrine glands activities.
Hormones of the anterior lobe of the pituitary
Growth hormone (GH) Adrenocorticotropic hormone (ACTH), Follicle- Stimulating hormone (FSH), Luteinizing hormone (LH), Thyroid- Stimulating hormone (TSH), Prolactin (PL)
Hormones of the
posterior lobe of the pituitary
1- Vasopressin or Antidiuretic hormone (ADH)
2- Oxytocin
Hormones of the anterior lobe of the pituitary
Growth hormone (GH) Adrenocorticotropic hormone (ACTH), Follicle- Stimulating hormone (FSH), Luteinizing hormone (LH), Thyroid- Stimulating hormone (TSH), Prolactin (PL)
Hormones of the
posterior lobe of the pituitary
1- Vasopressin or Antidiuretic hormone (ADH)
2- Oxytocin
Adrenal gland
It is located in the retroperitoneum above or medial to the upper poles of the kidneys.
It has two parts cortex (outer layer) and medulla , 90% is cortex and 10% is the inner medulla.
Adrenal gland
It is located in the retroperitoneum above or medial to the upper poles of the kidneys.
It has two parts cortex (outer layer) and medulla , 90% is cortex and 10% is the inner medulla.
Structure of the adrenal cortex
About 90% of the adrenal gland is composed of the cortex.
It consists of three layers (zones).
Structure of the adrenal cortex
About 90% of the adrenal gland is composed of the cortex.
It consists of three layers (zones).
1- Synthesis of adrenocortical hormones
The cortex has 3 layers: They produce steroid hormones from cholesterol
as a common precursor.
Zona glomerulosa: produces mineralocorticoids (aldosterone)
Zona fasciculata: produces mostly glucocorticoids (cortisol)
Zona reticulata: produces sex hormones (mostly androgens, dehydroepiandro-
-sterone and androstenedione).
*Adrenal cortex is regulated by pituitary hormone ACTH.
1- Synthesis of adrenocortical hormones
The cortex has 3 layers: They produce steroid hormones from cholesterol
as a common precursor.
Zona glomerulosa: produces mineralocorticoids (aldosterone)
Zona fasciculata: produces mostly glucocorticoids (cortisol)
Zona reticulata: produces sex hormones (mostly androgens, dehydroepiandro-
-sterone and androstenedione).
*Adrenal cortex is regulated by pituitary hormone ACTH.
Aldosterone secretion
Is under tonic control by ACTH, but is separately regulated by the
renin-angiotensin system and the potassium.
Renin- angiotensin- aldosterone system:
A- decreases in blood volume cause a decrease in renal perfusion pressure,
which in turn increases renin secretion.
-Renin, an enzyme, catalyzes the conversion of angiotensinogen to angiotensin I.
-Angiotensin I is converted to angiotensin II by angiotensin-converting
enzyme (ACE).
B- Angiotensin II acts on the zona glomerulosa of the adrenal cortex to increase
the conversion of corticosterone to aldosterone.
C- Aldosterone increases renal Na+ reabsorbtion, thereby restoring extracellular
fluid (CSF) volume and blood volume to normal.
D- Hyperkalemia increases aldosterone secretion. Aldosterone increases renal
K+ secretion, restoring blood [K+] to normal.
Aldosterone secretion
Is under tonic control by ACTH, but is separately regulated by the
renin-angiotensin system and the potassium.
Renin- angiotensin- aldosterone system:
A- decreases in blood volume cause a decrease in renal perfusion pressure,
which in turn increases renin secretion.
-Renin, an enzyme, catalyzes the conversion of angiotensinogen to angiotensin I.
-Angiotensin I is converted to angiotensin II by angiotensin-converting
enzyme (ACE).
B- Angiotensin II acts on the zona glomerulosa of the adrenal cortex to increase
the conversion of corticosterone to aldosterone.
C- Aldosterone increases renal Na+ reabsorbtion, thereby restoring extracellular
fluid (CSF) volume and blood volume to normal.
D- Hyperkalemia increases aldosterone secretion. Aldosterone increases renal
K+ secretion, restoring blood [K+] to normal.
Actions of mineralocorticoids (aldosterone)
1- increase renal Na+ reabsorption (action on the principal cells of the late
distal tubule and collecting duct).
2- increase renal K+ secretion (action on the principal cells of the late
distal tubule and collecting duct).
3- increase renal H+ secretion (action on the intercalated cells of the late
distal tubule and collecting duct).
Actions of mineralocorticoids (aldosterone)
1- increase renal Na+ reabsorption (action on the principal cells of the late
distal tubule and collecting duct).
2- increase renal K+ secretion (action on the principal cells of the late
distal tubule and collecting duct).
3- increase renal H+ secretion (action on the intercalated cells of the late
distal tubule and collecting duct).
Actions of Glucocorticoids (cortisol)
The name glucocorticoid derives from early observations that these hormones were involved in glucose metabolism. In the fasted state, cortisol stimulates several processes that collectively serve to increase and maintain normal concentrations of glucose in blood. These effects include:
1- Stimulation of gluconeogenesis, glucocorticoids increase gluconeogenesis by the following mechanisms:
A- increase in protein catabolizm
B- They decrease glucose utilization and insulin sensitivity of adipose tissue.
C- They increase lipolysis, which provides more glycerol to the liver for
gluconeogenesis. Also, the fatty acids released by lipolysis are used for production of energy in tissues like muscle.
2- Anti-inflammatory effects
Actions of Glucocorticoids (cortisol)
The name glucocorticoid derives from early observations that these hormones were involved in glucose metabolism. In the fasted state, cortisol stimulates several processes that collectively serve to increase and maintain normal concentrations of glucose in blood. These effects include:
1- Stimulation of gluconeogenesis, glucocorticoids increase gluconeogenesis by the following mechanisms:
A- increase in protein catabolizm
B- They decrease glucose utilization and insulin sensitivity of adipose tissue.
C- They increase lipolysis, which provides more glycerol to the liver for
gluconeogenesis. Also, the fatty acids released by lipolysis are used for production of energy in tissues like muscle.
2- Anti-inflammatory effects
Pathophysiology of the adrenal cortex
A- Adrenocortical insufficiency
1- primary adrenocortical insufficiency, Addison’s disease
2- secondary adrenocortical insufficiency
B- Adrenocortical excess: Cushing’s syndrome
C- Hyperaldosteronism: Conn’s syndrome
Pathophysiology of the adrenal cortex
A- Adrenocortical insufficiency
1- primary adrenocortical insufficiency, Addison’s disease
2- secondary adrenocortical insufficiency
B- Adrenocortical excess: Cushing’s syndrome
C- Hyperaldosteronism: Conn’s syndrome
Adrenal medulla
Hormones of the adrenal medulla
Epinephrine is synthesized mainly in the adrenal medulla, whereas Norepinephrine is found not only in the adrenal medulla but also in the central nervous system and in the peripheral sympathetic nerves. Dopamine, the precursor of norepinephrine, is found in the adrenal medulla and in noradrenergic neurons. Dopamine is also found in specialized mast cells.
Synthesis and Secretion of Catecholamines
Synthesis of catecholamines begins with the amino acid tyrosine, which is taken up by chromaffin cells in the medulla and converted to norepinephrine and epinephrine through the following steps:
Adrenal medulla
Hormones of the adrenal medulla
Epinephrine is synthesized mainly in the adrenal medulla, whereas Norepinephrine is found not only in the adrenal medulla but also in the central nervous system and in the peripheral sympathetic nerves. Dopamine, the precursor of norepinephrine, is found in the adrenal medulla and in noradrenergic neurons. Dopamine is also found in specialized mast cells.
Synthesis and Secretion of Catecholamines
Synthesis of catecholamines begins with the amino acid tyrosine, which is taken up by chromaffin cells in the medulla and converted to norepinephrine and epinephrine through the following steps:
