Anatomy - Endocrine System
Besides the rate of release and the speed of inactivation/degradation/execretion, what are the other important factors that influence the hormone concentration in blood?
*Number of receptors* - can be up or down regulated *Strength of binding with receptor* (affinity) Different cells with same receptor Same hormone different receptor, different response
What are the characteristics of hormones?
*Specific* - bind to specific receptors to alter the cellular activity of targets *Long-distance* *Exert responses at low levels* *Signal must be terminated* by feedback loops
The endocrine systems regulates metabolic activity via...
*hormone release*
Types of steroid hormones
-Estradiol -Testosterone -Progesterone -Glucocorticoids
What are the hypothalamic releasing & inhibiting hormones that act upon the anterior pituitary?
-Growth hormone releasing hormone (GHRH) -Growth hormone inhibiting hormone (GHIH; somatostatin) -Thyrotropin releasing hormone -Corticotropin releasing hormone -Gonadotropin releasing hormone -Prolactin inhibiting hormone (Dopamine) -Prolactin releasing hormone???
What are the 6-7 types of Hypothalamic Releasing and Inhibiting Hormones that regulate the anterior pituitary?
-Prolactin Releasing Hormone (PRH) -Prolactin Inhibiting Hormone (dopamine; PIH) -Thyrotropin Releasing Hormone (TRH) -Corticotropin Releasing Hormone (CRH) -Growth Hormone Releasing Hormone (GHRH) -Growth Hormone Inhibiting Hormone/somatostatin (GHIH) -Gonadotropin Releasing Hormone (GnRH)
What are the 3 types of hormones?
1) Amino acids 2) Peptides/proteins 3) Steroids
Explain the steps of the second messenger cyclic AMP.
1) Hormone binds to its receptor 2) This activated receptor activates a G protein, which exchanges its GDP for GTP 3) G protein activates adenylate cyclase (effector enzyme) 4) Adenylate cyclic converts ATP to cAMP, the 2nd messenger 5) cAMP activates protein kinases which trigger responses of the target cell
Hormone concentration in blood is influenced by...
1) Rate of release 2) Speed of inactivation, degradation, and/or excretion
The pituitary gland secretes at least _____ major hormones.
8 (2 from posterior pituitary and 4 from anterior pituitary)
Hypophyseal portal system
A blood vessel system that directly connects the hypothalamus with the anterior pituitary Made of: Primary capillary plexus Hypophyseal portal veins Secondary capillary plexus
Corticotrophs (CRH) of the anterior pituitary secrete...
ACTH (adrenalcorticotrophic hormone)
How does ADH inhibit urine formation?
ADH binds to the basolateral membrane of the collecting duct cell It activates cAMP 2nd messenger system and aquaporins are inserted in the apical membrane. Water is absorbed into the cell and into the blood. This increases fluid volume, which increases blood pressure.
Endocrine gland that controls the stress response
Adrenal glands
"Strength" of the binding interaction between a hormone and receptor
Affinity
What are the water soluble hormones?
Amino acid based hormones, except thyroid hormone
Structure of endocrine glands
An ORGANIZED group of cells (glands that release hormones into the bloodstream)
Growth hormone is an ___________ hormone.
Anabolic (small molecules being built into large molecules)
Permissiveness
Another hormone needed for hormone to exert full effect
What is PIP2-calcium?
Another secondary messenger system used by water soluble hormones which bind to plasma membrane receptors. Phospholipase C is the enzyme that hydrolyzes its bond. Its second messengers are IP3 and DAG.
Which peptide hormone in the posterior pituitary gland is responsible for: Inhibits urine formation by acting upon the nephron of the kidney Increases blood pressure (vasopressin - vasoconstriction)
Antidurietic Hormone/ADH
What is the endocrine system's target of stimulation?
Any cell in the body with a receptor for the hormone
List the biological organization from smallest to largest.
Atom → Molecule → Cell → Tissue → Organ → Organ system → Organism
Chemicals that exert effects on the same cells that secrete them
Autocrines
Water soluble hormones ______ pass through the phospholipid bilayer.
CANNOT They have receptors on the outside of the cell instead.
Characteristics of lipid soluble hormones
Can enter cell. Have intracellular receptors in the cytoplasm. Regulate gene expression. Bind to DNA and initiate transcription of the gene to mRNA. Require transport to get to target cells. Bind to binding proteins in the blood. Have a longer-half life as a result.
What are neurohormones?
Chemical signals released into the blood by a neurosecretory cell
Autocrines
Chemicals that exert effects on the same cells that secrete them
Explain the posterior lobe of the pituitary gland.
Composed of neural tissue Connected to hypothalamus via neurons in the hypothalamic-hypophyseal tract Neurons and cell bodies in paraventricular and supraoptic nuclei in hypothalamus Secretes ADH and Oxytocin (peptides), which are stored in axon terminals in the posterior pituitary
Hypothalamic neurohormones
Controls secretion of nearly all anterior pituitary hormones Released in close proximity to capillaries Peptides & proteins stored in vesicles
Explain the structure of a neuron.
Dendrites that receive info Cell body Axon that is long and conducts the action potential away from the cell body Axon terminals that synapse with other areas
Explain the amino acid hormones.
Derivatives of amino acids include tyrosine or tryptophan. Tyrosine derivatives: catecholamines and thyroid hormones Tryptophan derivatives: melatonin and serotonin
An organized group of endocrine cells that secrete the same substance surrounded by fibrous connective tissue
Endocrine glands
Endocrine vs Exocrine
Endocrine glands release hormones directly into the *bloodstream* to go to tissues of the body. Exocrine glands release secretions through ducts to *outside the body* or onto another surface within the body.
The body's "slow" chemical communication system; a set of glands that secrete hormones into the bloodstream
Endocrine system
Explain the anterior lobe of the pituitary gland.
Epithelial tissue (and connective) No direct neural connection between hypothalamus and AP lobe Vascularly connected to hypothalamus via hypophyseal portal system (Primary capillary plexus, Hypophyseal portal veins, Secondary capillary plexus) Small quantities of hormones rapidly delivered to AP to prevent systemic dilution Hypothalamus secretes releasing and inhibitory neurohormones (6) that travel here to regulate hormone secretion
T/F: Endocrine glands have ducts.
FALSE Endocrine glands lose their ducts and secrete hormones into the bloodstream.
T/F: Hormones exert responses at high levels
FALSE Hormones exert responses at LOW levels
T/F: Thyroid hormone is an amine that is water-soluble.
FALSE. It is lipid-soluble.
T/F: Only one hormone can act on the same target cell.
FALSE. Many hormones may act on the same target cells.
T/F: The anterior pituitary lobe has a direct neural connection to the hypothalamus.
FALSE. No direct neural connection between hypothalamus and anterior pituitary lobe. It is vascularly connected to hypothalamus via hypophyseal portal system.
T/F: Lipid soluble hormones can be stored in vesicles.
FALSE. Only water soluble hormones can be stored in vesicles because they cannot pass through the vesicles' phospholipid bilayer.
T/F: Lipid soluble molecules go through signal transduction pathways.
FALSE. WATER soluble molecules go through signal transduction pathways. Lipid soluble molecules can go through the phospholipid bilayer and bind to receptors inside the cell.
Gonadotrophs (GnRH) of the anterior pituitary secrete...
FSH & LH (follicle stimulating hormone & luteinizing hormone)
Free vs Bound Hormones (to receptors)
Free hormones can pass through the endothelial membrane of the capillary (water soluble) Bound hormones cannot pass through the endothelial membrane of the capillary (lipid soluble)
Examples of endocrine cells
G cells - gastrin D cells - somatostatin
G proteins interact with the receptor protein to become a...
G protein coupled receptor.
Small intracellular proteins that link receptors with effector proteins
G proteins
Somatotrophs (GHRH/GHIH) of the anterior pituitary secrete...
GH (growth hormone)
What is an example of synergism?
Glucagon, cortisol, and epinephrine on hepatocytes. All increase blood glucose levels individually. Combined, leads to drastic increase in blood glucose.
Sex glands; secrete hormones that regulate sexual development and behavior as well as reproduction
Gonads (ovaries & testes)
Chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream, and affect other tissues
Hormones
Tropic hormones
Hormones that affect the release of another hormone Act upon other endocrine glands/cells
Trophic hormones
Hormones that cause growth (hypertrophy or hyperplasia)
Secretion of nearly all anterior pituitary hormones is regulated by...
Hypothalamic neurohormones
Supreme regulator of the endocrine system
Hypothalamus
What kind of secretions go to the anterior lobe of the pituitary gland?
Hypothalamus secretes releasing and inhibitory neurohormones (6) that travel here to regulate hormone secretion (tropic hormones)
What are the second messengers of PIP2-calcium?
IP3 and DAG
Where is the hypothalamus?
In the diencephalon of the forebrain. Below the thalamus. Connected to the pituitary gland.
What are G proteins?
Intracellular proteins (located in cytosol) that bind GDP and GTP. When the G protein is bound to GDP it is inactive. When the G protein is bound to GTP it is active. The hormone binding causes exchange. G proteins interact with the receptor protein to become a G protein coupled receptor.
Mechanism of action on target cells: Lipid soluble hormones vs Water soluble hormones
Lipid soluble hormones activate genes, causing synthesis of new proteins. Water soluble hormones act through second messenger systems.
Sources of lipid-soluble hormones vs sources of water soluble hormones
Lipid soluble hormones come from the adrenal cortex, gonads, and thyroid gland. Water soluble hormones come from all other endocrine glands.
Which has a longer half life, lipid soluble or water soluble hormones?
Lipid soluble hormones have a longer half life because they are bound to binding proteins in blood, which protects them from being degraded or excreted.
Locations of receptors: Lipid soluble hormones vs Water soluble hormones
Lipid soluble hormones have receptors that are usually inside the cell. Water soluble hormones have receptors that are on the plasma membrane (outside the cell).
Paracrines
Locally acting chemicals that affect cells other than those that secrete them
What are hormones?
Long-distance chemical signals produced by endocrine cells that travel in blood or lymph
Explain the hypothalamus.
Main regulator of the endocrine system. In the diencephalon of the forebrain. Connected to the pituitary gland.
Explain the pituitary gland.
Master gland Secretes at least 8 major hormones Made up of 2 lobes: anterior and posterior Connected to the hypothalamus
What are the tropic (affect release of another hormone) actions of growth hormone?
Mediated by insulin-like growth factors (IGFs) which are produced in response to GH Mainly related to growth (growth of bone & muscle mass)
What are the non-tropic actions of growth hormone?
Metabolic inducing role, providing fuel for growth to occur. GH directly causing effects that are independent of IGFs. -Increase fat breakdown (lipolysis) in adipocytes -Decrease glucose uptake and utilization -In liver, increased glycogenolysis which increases blood glucose for an anti-insulin or glucose sparing effect -Mitosis
What are the ways in which animals respond to their environments?
Nervous system & endocrine system
Long-distance chemical signals that travel in blood or lymph Produced by neurosecretory cells
Neurohormones
Another name for the posterior lobe of the pituitary gland, which stores and releases oxytocin and ADH/vasopressin produced in the hypothalamus.
Neurohypophysis
How is the anterior lobe of the pituitary gland connected to the hypothalamus?
No direct neural connection between hypothalamus and AP lobe Vascularly connected to hypothalamus via hypophyseal portal system (Primary capillary plexus, Hypophyseal portal veins, Secondary capillary plexus)
Characteristics of water soluble hormones
No transport proteins in the blood. Shorter half life, because enzymes in the plasma can degrade them and they can be excreted. Receptors on outside of the cell that activate second messengers (faster response).
Structure of endocrine cells
Not organized, diffuse (spread out)
Which peptide hormone in the posterior pituitary gland is responsible for: -Stimulates uterine contractions during childbirth by smooth muscle contractions of the uterine wall via PIP2-calcium second messenger system -Triggers milk ejection (letdown) by smooth muscle contraction -Involved in pair bonding (cuddle hormone)
Oxytocin
Hypothalamic neurohormones released from posterior pituitary
Oxytocin and ADH/vasopressin
Which hypothalamic hormones are released into the posterior pituitary?
Oxytocin and ADH/vasopressin
Explain oxytocin.
Oxytocin is a peptide of 9 amino acids that -Stimulates uterine contractions during childbirth by smooth muscle contractions of the uterine wall via PIP2-calcium second messenger system -Triggers milk ejection (letdown) by smooth muscle contraction -Involved in pair bonding (cuddle hormone)
Endocrine gland that controls blood glucose levels
Pancreas
Locally acting chemicals that affect cells other than those that secrete them
Paracrines
These 2 endocrine glands regulate Ca2+ homeostasis in blood
Parathyroid glands and thyroid gland
Antidurietic Hormone/ADH/vasopressin
Peptide of 9 amino acids Inhibits urine formation by acting upon the nephron of the kidney Increases blood pressure (vasoconstriction)
Short chains of amino acids
Peptides
Explain peptide hormones.
Peptides are short chains of amino acids. Types: -ADH -Oxytocin -Adrenocorticotropic hormone (ACTH)
In this type of interaction, a hormone MUST have an interaction with another hormone to exert its full effect.
Permissiveness
Endocrine gland that is located in the forebrain and secretes melatonin
Pineal gland
Lactotrophs or mammotrophs (PIH) of the anterior pituitary secrete...
Prolactin
Long polymers of amino acids
Proteins
Explain the protein hormones.
Proteins are long polymers of amino acids. Types: growth hormone, prolactin
What is growth hormone?
Secreted by somatotrophs of the anterior pituitary. It is a protein of 191 amino acids (also called somatotropin). It is regulated by GHRH and GHIH. GHRH stimulates somatotropic cells to secrete GH. GHIH (somatostatin) inhibits GH. Has tropic and non-tropic effects.
The posterior lobe of the pituitary gland secretes what?
Secretes ADH and Oxytocin (peptides), which are stored in axon terminals in the posterior pituitary
Communication method of the endocrine system
Secretes hormones into blood; hormones transported within the blood are distributed to target cells throughout body
A series of molecular changes that converts a signal on a target cell's surface to a specific response inside the cell.
Signal transduction
What are the 5 types of cells in the anterior pituitary, and what are the hormones they secrete?
Somatotrophs (GHRH/GHIH) - Secrete GH Lactotrophs or mammotrophs (PIH) - Secrete prolactin Gonadotrophs (GnRH) - Secrete FSH and LH Thyrotrophs (TRH) - Secrete TSH Corticotrophs (CRH) - Secrete ACTH
What are the lipid soluble hormones?
Steroids and thyroid hormones (type of amine)
Explain steroid hormones.
Steroids are made of 4 carbon rings that are fused together. Derived from cholesterol. Types: Estradiol, Testosterone, Progesterone, Glucocorticoids Their different functional groups allow for them to bind to different receptors.
In this type of interaction, more than 1 hormone produces the same effects on a target cell. When combined, the effects of these hormones are AMPLIFIED.
Synergism
Thyrotrophs (TRH) of the anterior pituitary secrete...
TSH (thyroid stimulating hormone)
The anterior pituitary gland is made of _____________________ while the posterior pituitary gland is made of _____________________.
The anterior pituitary gland is made of EPITHELIAL TISSUE & CONNECTIVE TISSUE while the posterior pituitary gland is made of NEURAL TISSUE.
Endocrine system vs nervous system in duration of response
The endocrine system has a long-lasting response that may continue after the stimulus is removed. The nervous system has a short-term response that terminates with the removal of the stimulus.
Endocrine system vs nervous system in response time
The endocrine system has a slow reaction time. The nervous system has a rapid reaction time.
What is the endocrine system's range of effect?
The endocrine system typically has widespread effects throughout the body.
How do animals respond to their environment using the endocrine system?
The endocrine systems regulates metabolic activity via hormone release. Hormones are transported around the body in blood.
Explain the 2 messengers of a signal transduction pathway.
The first messenger is the hormone that binds to the receptors on the plasma membrane. The second messenger is another molecule that is the transducing signal that causes a response.
Neurohypophysis
The posterior pituitary gland; secretes oxytocin and antidiuretic hormone (ADH)
Characteristics of Hypothalamic Releasing and Inhibiting Hormones regulating the Anterior Pituitary
They are *neurohormones* released into the portal system They are *tropic hormones* that act on other endocrine glands to promote or inhibit the release of hormones from the anterior pituitary
How do the hypothalamic releasing and inhibiting hormones go into the anterior pituitary?
They are produced and stored in neurosecretory cells in the hypothalamus. They are released into the primary capillary plexus. They travel through hypothalamic/hypophyseal portal veins. They act upon anterior pituitary cells whose secretions leave out of the secondary capillary plexus.
Endocrine gland for immune function and cell maturation
Thymus
Half-life
Time required for level of hormone in blood to decrease by half varies from <1 min to >1 week
Hormones that cause growth (hypertrophy or hyperplasia)
Trophic hormones
Hormones that affect the release of another hormone Act upon other endocrine glands/cells
Tropic hormones
Hormones that stimulate other glands to release their hormones Ex: the releasing and inhibitory neurohormones secreted by the hypothalamus, which regulates hormone secretion in the anterior pituitary lobe
Tropic hormones
T/F: Exocrine glands have ducts.
True
T/F: Hormones are long distance.
True
T/F: Hormones are transported around the body in the blood.
True
T/F: Hormones exert responses at low levels.
True
T/F: Lipid soluble hormones bind to intracellular receptors.
True
T/F: Lipid soluble hormones regulate gene expression.
True
T/F: Many hormones may act on the same target cells.
True
T/F: Thyroid hormone is an amine that is lipid-soluble.
True
T/F: Different cells may have the same receptor for a hormone.
True.
T/F: Steroid hormones cannot be stored in vesicles so they are made as needed.
True.
T/F: The signal generated by hormones must be terminated by feedback loops.
True.
T/F: The strength of binding with a receptor influences the hormone concentration.
True.
T/F: The posterior pituitary lobe has a direct neural connection to the hypothalamus.
True. It is connected to hypothalamus via neurons in the hypothalamic-hypophyseal tract.
T/F: The same hormone may have different receptors.
True. There is a different response.
Upregulation of receptors vs Downregulation of receptors
Upregulation - increasing number of receptors on target cells Downregulation - decreasing number of receptors on target cells
_________ soluble hormones have receptors on the outside of the cell that...
WATER soluble hormones have receptors on the outside of the cell that activate second messengers
Water soluble vs lipid soluble
Water soluble - hydrophilic, amino acid based hormones Lipid soluble - hydrophobic, steroids & thyroid hormone
Can water-soluble and lipid-soluble hormones be stored in secretory vesicles?
Water soluble hormones CAN be stored in secretory vesicles. Lipid soluble hormones CANNOT be stored in secretory vesicles.
Transport in blood: Water soluble hormones vs Lipid soluble hormones
Water soluble hormones are usually free in the plasma. Lipid soluble hormones are bound to plasma proteins.
What kind of hormones can be stored in vesicles and why?
Water soluble hormones can be stored in vesicles, which includes amine/peptide/protein hormones. Because vesicles are also made of a phospholipid bilayer, water soluble hormones cannot pass out of them.
Half life in blood: Water soluble hormones vs Lipid soluble hormones
Water soluble hormones have a SHORT half life because most can be removed by the kidneys. Lipid soluble hormones have a LONG half life because most need to be metabolized by the liver.
Which has a shorter half life, lipid soluble or water soluble hormones?
Water soluble hormones have a shorter half life because, since they are not bound to and protected by binding proteins in the blood, enzymes in the plasma can degrade them and they can be excreted
Synergism
When more than 1 hormone produces the same effects on a target cell. When combined, the effects of these hormones are amplified.
Antagonism
When one hormone opposes the action of another hormone. -Competition for receptors -Downregulation of receptors
The releasing and inhibitory neurohormones secreted by the hypothalamus go to the _____________ pituitary lobe in order to...
anterior regulate hormone secretion
A second messenger derived from ATP and triggers specific cellular changes in metabolic regulation
cyclic AMP
2 main second messengers
cyclic AMP PIP2-calcium
Hormones are secreted by...
endocrine cells or groups of cells (endocrine glands)
Binding of the ligand/hormone to the receptor on the plasma membrane allows for the G protein to...
exchange GDP for GTP and become its active form
The signal generated by hormones must be terminated by...
feedback loops
G proteins bind...
guanosine nucleotides (GDP & GTP)
The first messenger in a signal transduction pathway is the ___________________.
hormone, which binds to the receptor on the plasma membrane
The secretions of endocrine glands are called...
hormones
The endocrine system secretes ___________ that are transported within the ___________ and distributed to target cells throughout the body.
hormones blood
Example of antagonism
insulin vs glucagon
Autocrines and paracrines are...
local chemical messengers (the book considers these local hormones)
The posterior lobe of the pituitary gland is connected to the hypothalamus via...
neurons in the hypothalamic-hypophyseal tract
The Hypothalamic Releasing and Inhibiting Hormones that regulate the Anterior Pituitary are produced and stored in...
neurosecretory cells (neurons) in the hypothalamus
How does the body do chemical signaling?
neurotransmitters and hormones
Cuddle hormone
oxytocin
Name the endocrine glands of the body.
pineal gland hypothalamus pituitary gland thyroid gland parathyroid glands thymus adrenal glands pancreas gonads (ovaries & testes)
The hypothalamus is connected to the _____________ gland.
pituitary
The higher the affinity of a hormone, the _____________ the binding with the receptor.
stronger
There is a __________ effect of GH and IGFs
synergistic
All organisms respond to...
their environment
Signal transduction occurs with...
water soluble ligands, so most amine, peptide & protein hormones
