Ch.9: Endocrine (2/17) Flashcards
Electrical signals
-fast quick & short lives reponses (sec,msec - depends on type of hormone or AP) (eg. muscle movement
-generated by changes in cell membrane potential that triggers response
characteristics of chemical signals
-called hormones
-generated slowly, slower action, effects are long lasting (min,hrs,days)
-produced by endocrine glands
endocrine (word breakdown)
endo=internal
krinein=distinguish bw 2 things
hormones travel via
blood
neurotransmitters
chemical signals that allow for neutron to neutron communication
What ions are present inside the cell at rest?
Potassium (K+), phosphate, proteins, amino acids (all negatively charged)
What ions are present outside the cell at rest?
Sodium (Na+), Calcium (Ca2+), Chloride (Cl-) (positively charged).
What is the resting membrane potential of a cell?
-70 mV (cell is polarized, inside is negative).
What happens during depolarization of a cell?
-Sodium (Na+) enters the cell (ca2+ also)
-making the inside more positive (potential difference shifts from -70 mV to a more positive value).
What does the sign of the membrane potential represent?
The sign indicates the condition inside the cell (e.g., -70 mV means the inside is negative).
What is an action potential (AP)?
-Complete reversal of polarity; inside becomes positive relative to outside,
-self-propagating (once an action potential starts, it continues without needing additional stimulation)
-travels long distances without fading (signal stays strong as it moves along the neuron, without decreasing in strength)
What causes depolarization and the generation of an action potential?
Sodium (Na+) and/or Calcium (Ca2+) entering the cell.
How is repolarization achieved after depolarization?
Potassium (K+) exits the cell to return the membrane potential back to -70 mV.
What is hyperpolarization?
When the cell becomes more negative than the resting membrane potential (e.g., after excessive K+ exit or chloride (Cl-) entry).
graded potential
A change in membrane potential that does not fully depolarize the cell, can be depolarizing or hyperpolarizing, and fades with time and space.
difference between depolarizing and hyperpolarizing graded potentials?
Depolarizing: Makes the cell less negative (e.g., from -70 to -50 or -20 mV).
Hyperpolarizing: Makes the cell more negative (e.g., from -70 to -90 mV).
EPSPs (Excitatory Postsynaptic Potentials)?
Depolarizing signals that excite the cell, leading to muscle contraction or neuron activation.
IPSPs (Inhibitory Postsynaptic Potentials)?
Hyperpolarizing signals, preventing muscle contraction or neuron activation.
What is the role of glycine in the cell?
Glycine binds to chloride channels, causing chloride (Cl-) entry (hyperpolarizing) and inhibiting the cell.
role of GABA (Gamma-Aminobutyric Acid) in the cell?
GABA is an inhibitory neurotransmitter that helps hyperpolarize the cell by binding with chloride (Cl-) channels, opening them to allow chloride ions (Cl-) to enter the cell. This influx of Cl- makes the inside of the cell more negative, inhibiting further action.
GABA a not GABA b
function & type of hormones?
-Chemical signals released from ductless glands
-Bind to specific receptors on or inside target cells
-Trigger a cellular response
Growth hormone, insulin, calcitonin, parathyroid hormone, androgens, estrogens.
neurohormones
-chemicals secreted by neurons synthesized by hypothalamus, GI tract, or nerves
-Released into the bloodstream in pituitary gland
-Travel to target organs
role of Antidiuretic Hormone (ADH)?
-neurohormone
-Regulates water balance and reabsorption in kidneys
-Prevents DIURESIS (water loss through urine)
ADH Present: Concentrated urine, less volume
ADH Absent: Diluted urine, large volume (Diabetes Insipidus)
What is the role of Oxytocin?
-neurohormone
-Stimulates uterine contractions (when giving labor)
-Stimulates milk letdown/ejection during breastfeeding
2 types of neurohormones
ADH (Antidiuretic Hormone) & Oxytocin
How do neurohormones from the hypothalamus regulate pituitary functions? (release & inhibiting factors)
-Neurohormones from the hypothalamus regulate pituitary functions by releasing factors.
-Releasing Factors:
-TRH (Thyrotropin-releasing hormone) (smallest w 3 aa)
-CRH (Corticotropin-releasing hormone)
-GnRH (Gonadotropin-releasing hormone)
-GHRH (Growth hormone-releasing hormone)
-Inhibiting Factors:
-SRIF (Somatostatin) = Inhibits release of growth hormone (GH) from the pituitary
-PIH (Prolactin Inhibiting Hormone) = Inhibits secretion of prolactin from the pituitary
What neurohormones are secreted by the GI tract?
-Ghrelin
-Secretin (1st hormone)
-Cholecystokinin (CCK)
-Motilin
-Glucagon-like Peptide 1 (GLP-1)
-Gastrin Inhibiting Peptide (GIP)
-Somatostatin (SST)
catecholamines and their role as neurotransmitters?
-chemicals include epinephrine, norepinephrine, and dopamine (bind to adrenic receptors; alpha/beta receptors)
-Involved in communication between neurons
chemicals in neurotransmitters
-Acetylcholine
-Serotonin
-Histamine
-Glutamic acid
-Glycine
-GABA (Gamma-Aminobutyric Acid)
-ATP
-Adenosine
-Nitric oxide
-Carbon monoxide (CO)
functions of the endocrine system?
-Osmoregulation
-Metabolism
-Reproduction
-Growth and development
-Digestive physiology
-Homeostasis
-Feedback mechanisms
osmoregulation?
-Water and electrolyte balance in the body
-ADH (Vasopressin) regulates water retention in the kidneys
-Aldosterone (Na+ reabsorption)
-300 mosmols in cells and plasma is balanced
-280 mosmols in the cell (dilute): water leaves the cell, causing it to shrink
-320 mosmols in the cell (concentrated): water enters the cell, causing it to swell
Aldosterone
hormone that regulates Na+ reabsorption, leading to water reabsorption
How does ADH regulate water balance?
-ADH is released when the body is dehydrated
-It promotes water reabsorption in the kidneys
-Prevents water loss through urine
What are the key hormones involved in metabolism ( & BMR)?
bmr=amount of energy (calories) your body needs to perform basic functions while at rest
-T3/T4 (Thyroid hormones) regulate metabolic rate
-Insulin: lowers blood sugar when it’s high (hyperglycemia)
-Glucagon: raises blood sugar when it’s low (hypoglycemia)
Basal Metabolic Rate (BMR)?
Metabolism:
39 kcal/hr per square meter is the energy needed to maintain basic body functions at rest
hyperglycemia
negative feedback (works to reverse a change)
-euglycemia is normal blood sugar level
-High blood sugar levels
-Can occur after eating (post-prandial) or due to insulin resistance
-Insulin is used to lower blood sugar and bring it back to normal levels
What is hypoglycemia?
-Low blood sugar levels
-Can occur when you haven’t eaten for a long time
-Glucagon is used to raise blood sugar to normal levels (euglycemia)
Diabetes Insipidus
Condition where body loses too much water leading to excessive unrination & thirst (ADH present)
first hormone to be named & by whom
Secretin & by Bayiss & Starling (1902-05)
smallest hormone
TRH Thyroptopin relase hormone (3 amino acids)
Somatotropin release-inhibiting factor
A growth hormone inhibitor
GIP-1 (Glucagon-like peptide-1)
Inhibits appetite
Cholecystokinin (CCK)
CCK helps you feel full after eating. It tells your brain to stop eating, which helps control your appetite.
If CCK isn’t working properly, you may not feel full after eating, leading to binge eating (eating a lot at once) like in bulimia.
helps release bile from the gallbladder, which is needed to break down fats in food.
Motilin
Helps peristalsis (movement of food); in vomiting, peristalsis reverses.
Gastrin
Stimulates hydrochloric acid (HCl) production in the stomach.
Osmolarity
concentration of dissolved particles (like ions, molecules, or salts) in a solution.
Aquaporins
Water channels inserted by ADH in kidney tubules to allow water reabsorption.
ENaC (Epithelial sodium channels)
channels that help retain sodium in the body.
BMR (Basal Metabolic Rate)
39 kcal/hr/m²; adult body surface area ~2m².
Nephron
Kidney’s filtering unit, containing tiny tubules called kidney tubules.
T3/T4 (Thyroid hormones)
Control metabolism and physical growth.
Hyperthyroidism
high T3/T4 levels, leading to a high BMR, excess energy, feeling warm.
Hypothyroidism
Caused by low T3/T4 levels, leading to low BMR (Basal Metabolic Rate).
feeling cold, stunted growth (cretinism)
Negative feedback
works to reverse a change and bring things back to normal
Glucagon
(secreted by Alpha cells): Raises blood sugar when too low.
Insulin
(secreted by Beta cells): Lowers blood sugar through negative feedback.
insulin shock
-Occurs in hypoglycemia (low blood sugar).
-Caused by too much insulin, leading to dangerously low blood sugar.
Reproductive Hormones
Involved in embryonic development, fertilization, gametogenesis (egg/sperm production), reproductive cycle, sex differentiation, and pregnancy.
Hormones invloved in reproduction
Embryonic development
Fertilization
Gamogenesis (production of sperm/egg)
Reproductive cycle
Sex differentiation - makes m/f during embriotic dev us under hormonal control (dihydrotestosterone (DHT)
Dihydrotestosterone (DHT)
aids in sex differentation: Shapes male genitalia during embryonic development (7-8 weeks)
lack of DHT leads to absence of male genitalia despite having a Y chromosome.
Testosterone
Produced by the Leydig cells in the testes that convert to DHT using 5 alpha reductase to shape male genitalia
5-alpha Reductase
-enzyme that converts testosterone into dihydrotestosterone (DHT).
-5-alpha reductase absence leads to no DHT production, so the individual will not develop male genitalia even with a Y chromosome.
GnRH (Gonadotropin-releasing Hormone)
Released by the hypothalamus to trigger the pituitary gland to secrete FSH and LH (gonadotropins)
FSH (Follicle-Stimulating Hormone)
Stimulates ovarian follicle growth and maturation in females, sperm production in males.
LH (Luteinizing Hormone)
Triggers ovulation in females and stimulates testosterone production in males.
Primary Follicles
-The earliest stage of ovarian follicles.
-Produce the hormone estradiol-17B
-Use FSH (Follicle Stimulating Hormone) to mature into Graafian follicles (the mature form).
Graafian Follicle and discharges what
Mature follicle that discharges an oocyte during ovulation under the influence of LH.
Corpus Luteum
After ovulation, the Graafian follicle ruptures and releases a secondary oocyte.
The remaining follicle transforms into the corpus luteum under the influence of LH (luteinizing hormone).——————————————————————————————Forms after ovulation and uses LH to secrete progesterone, which helps maintain pregnancy. (during in 3 months if preg occurs or 2 weeks if preg not occur)
Human Chorionic Gonadotropin (hCG)
Secreted by the placenta if pregnancy occurs to signal corpus luteum to keep producing progesteron.
- used to detected in urine for pregnancy tests.
Sertoli Cells
Located in the testes, produce anti-Müllerian hormone (AMH) to prevent the development of female reproductive structures in male embryos.
Spermatogenesis
The process of sperm production in the testes, stimulated by FSH.
Leydig Cells
Located in the testes, produce testosterone, which is converted to DHT.
AMH (Anti-Müllerian Hormone)
Secreted by Sertoli cells in males to prevent the formation of female reproductive structures during embryonic development.
FSH and LH in males
FSH stimulates sperm production and LH does Testosterone production
FSH and LH in females
FSH does folicular maturation ( helps ovarian follicles grow and develop) and LH does ovulation (causes the mature follicle to release an egg)
Growth Hormone
(GH aka somatotropin) – Stimulates an increase in height.
GH Pathway for gwroth & development
GH from the pituitary -> liver -> liver produces somatomedins (IGF-1 & IGF-2) -> stimulates bone elongation.
Epiphysis
The site where bone growth occurs, leading to increased height.
Somatomedins (IGF-1 & IGF-2)
Insulin-like growth factors that promote bone and tissue growth that are made by liver
Growth Factors
GF, FGF, PDGF, NGF, and TGF-β
Hormones of GI tract
Ghrelin, Gastrin, VIP, Cholecystokinin (CCK), Motilin, Glucagon-like peptide, seretin, Gastrine Inhibitory Peptide (GIP)
Ghrelin
Hormone from the stomach that stimulates appetite (pepsin) and hunger
Gastrin
Hormone from the stomach that stimulates gastric secretion but does not affect appetite to promote gastric motility (the movement of food through the stomach).
Vasoactive Intestinal Polypeptide (VIP)
Relaxes sphincters (circular muscles that regulate food passage in the GI tract).
Achalasia (lack of vip): condition where sphincter doesnt open and hard for food to pass into stomach
Achalasia
Condition caused by a lack of VIP where the lower esophageal sphincter does not open, making it hard for food to pass into the stomach
eg. baby when they burb bc vip not yet mature
bulimia nervosa
CCK Deficiency
Motilin
Hormone that stimulates peristalsis (wave-like contractions that move food down the digestive tract).
Glucagon-like Peptide-1 (GLP-1)
appetite regulation (reduce)
Secretin
Hormone released by the duodenum that stimulates the pancreas to release bicarbonate-rich juice, neutralizing HCl to protect the intestines.
Gastric Inhibitory Peptide (GIP)
Stimulates insulin release and inhibits gastric secretions (substances produced and released by the cells of the stomach to aid in digestion).
Homeostasis
Maintains balance between internal and external environments, cells, and the body.
Proposed the concept of homeostasis.
Claude Bernard (18th century)
Walter Cannon (1930)
Coined the term “homeostasis.”
Sensors
involved in homeostatsis, Detect changes from a set point (e.g., glucoreceptors, osmoreceptors, chemoreceptors, baroreceptors).
Effectors
Respond to changes and restore normal conditions.
Negative Feedback
Used to regulate and control homeostasis; constantly monitors a physiological variable and restores normalcy.
Positive Feedback
Used only when needed; amplifies an initial reaction.
example: when a baby suckles
How does suckling trigger milk letdown?
-When a baby suckles, nervous signals are sent to the hypothalamus.
-The hypothalamus secretes oxytocin, which travels to the mammary glands.
-Oxytocin causes milk letdown/ejection.
How does oxytocin help during labor and delivery?
-During parturition (birth process), the baby’s head stretches the cervix.
-This sends neural signals to the hypothalamus, which releases oxytocin.
-Oxytocin stimulates uterine contractions, helping to progress labor.
Why doesn’t a non-pregnant person experience contractions?
-A non-pregnant person has receptors for oxytocin, but no oxytocin is released.
-Without oxytocin release, uterine contractions do not occur.
What are examples of protein-based hormones derived from amino acids?
-Kidneys (secretes erythropoietin)
-Heart (secretes atrial natriuretic peptide, ANP)
-Pituitary
-Pancreas
-Hypothalamus
-Parathyroids (PTH)
-Thymus
What steroid hormones are produced by the adrenal cortex?
-Aldosterone
-Cortisol
What steroid hormones are produced by the testes and ovaries?
-Testes: Androgens
-Ovaries: Estrogens, Progesterone
What hormone is produced by the skin, and what is its role?
-Vitamin D3
-1,25-Dihydroxy-cholecalciferol (Calcitriol aka active vitamin D)
What is rickets, and what causes it?
-Rickets is caused by a deficiency in Vitamin D.
-It leads to weak and bent legs because the bones cannot hold the weight of the body.
role of bile in hormone regulation?
emulsification of fats
What hormones can be made from tyrosine and why is it important?
-Tyrosine is important because it can be converted to make catecholamines (epinephrine, norepinephrine, dopamine).
-Tyrosine also makes:
-T3/T4 (thyroid hormones)
-Melanin
-Histamine
-Serotonin
-Melatonin (produced by the pineal gland, sleep-inducing)
What are eicosanoids and how are they formed?
-Eicosanoids are long-chain fatty acids made from arachidonic acid (20 carbon atoms) that gives rise to prostaglandins, including:
-PGE1: Vasodilation and affects blood pressure
-PGF2 Alpha: Dissolves corpus luteum
-PGI2 (Prostacyclin): Vasodilation and prevents blood clotting
-TXA2 (Thromboxane A2): Vasoconstriction and promotes blood clotting
How are peptide hormones synthesized?
-Peptide hormones are made up of amino acids.
-Example: Insulin synthesis in the Golgi complex:
-Pre-pro-insulin → Pro-insulin → Insulin (released into the blood)
What are examples of hormones circulating in free (unbound) form?
sugar regulation:
-Insulin - lowers
-Glucagon - increases
calcium reulation:
-PTH (Parathyroid hormone) - increases
-Calcitonin - lowers
What are examples of hormones bound to proteins in the blood?
-T3/T4 (bound to transthyretin)
-Cortisol (bound to transcortin)
-Testosterone/DHT (bound to androgen binding protein)
How are hormones degraded and removed from the body?
-Hormones are degraded and removed by:
-Kidneys
-Conjugation to sulfate or glucuronic acid (makes hormones water-soluble for removal by kidneys)
-Enzymes such as insulinase and vasopressinase
How is insulin degraded in the body?
degraded by an enzyme called insulinase. in kidneys
How is vasopressin (ADH) degraded, and what condition can affect this process?
-Vasopressin is degraded by vasopressinase.
-During pregnancy, the placenta produces too much vasopressinase, which affects vasopressin levels and can lead to excessive water loss in urine (diuresis).
What is the role of enzymes in hormone degradation?
-Enzymes are proteins that are NOT destroyed after the reaction and can be reused.
-Hormones, however, are destroyed after they elicit a response, requiring the body to produce new hormones.
What is the half-life of a hormone?
The time it takes for 50% of a hormone’s concentration to be reduced or removed from the body.
How does the half-life of hormones vary?
-Fast-acting hormones have shorter half-lives.
-Slow-acting hormones have longer half-lives.
ex:-TSH (Thyrotropin) = 60 minutes.
-Testosterone = 1–3 hours (slow-acting).
How do hormones act on target cells?
-Hormones leave the source, travel via blood, and bind to receptors on target cells.
-Binding triggers a response in the target cell.
-Receptors are proteins that bind neurotransmitters or hormones to trigger responses.
What are the types of receptors, and how are they regulated?
-Cells can have up to 100,000 receptors.
-Up-regulation: Increases receptor numbers.
-Down-regulation: Decreases receptor numbers (e.g., Type 2 Diabetes).
Which hormones use surface receptors and examples?
-Protein/peptide hormones act via enzyme cascades (one enzyme activates the next enzyme in a sequence. ) and bind to receptors on the cell surface.
-Examples: Insulin, Glucagon, PTH, Epinephrine, FSH, LH, TSH, ACTH, ADH, Oxytocin.
Which hormones use intracellular receptors (receptors inside the cell), and why?
-Used by steroids & T3/T4 (cs lipophilic, hydrophobic).
-Hormones cross the membrane and bind receptors inside the cell.
-Examples: Testosterone, Estradiol-17β (form of estrogen), Cortisol, Aldosterone, T3/T4.
-Triggers gene expression → protein production.
How do peptide/protein hormones trigger a response?
-Bind to surface receptors.
-Activate/trigger a enzyme cascade (usually via second messengers).
-Triggers enzyme activation and cellular response.
What are examples of ion channel receptors?
-Acetylcholine receptor (ligand-gated sodium channel) → depolarizes cell.
-Glycine & GABA receptors → chloride channels.
-IP3 receptors on SR (sarcoplasmic reticulim= ER inside cell) → calcium channels.
What are the types of g proteins and their functions?
-G-protein: Three subunits (α, β, γ).
-Gαs (stimulatory) → activates cAMP.
-Gαi (inhibitory) → prevents cAMP formation.
Gi reduces relaxation (vasoconstriction by inhibiting PKA, which would normally stop MLCK.
-Gαq → activates enzyme called phospholipase C and breaks it into 2 second messangers (IP3 & DAG pathways). Gq directly triggers contraction via Ca²⁺ release.
What does monoamine oxidase (MAO) do?
-MAO breaks down epinephrine and norepinephrine.
-These hormones help keep a person awake, conscious, and active.
-If there is less epinephrine/norepinephrine, a person may feel less active or depressed.
-MAO inhibitors (MAOIs) are used as antidepressants because they prevent the breakdown of these neurotransmitters, increasing their levels.
2 types of Acetycholine receptor (ligand gated na+ channels
surface receptor
-Nicotinic type: ion channels
-Muscarinic type: G protein coupled receptor
What happens when epinephrine binds to its receptor keading to vasodilation
Epinephrine (ligand) binds to the B2 receptor coupled with a Gs protein(!)
Alpha subunit of the G protein binds GTP → Active state
When GTP is hydrolyzed (broken down using water) to GDP, the G protein becomes inactive
Binding of the ligand activates the G protein, triggering the signal transduction process
How does the G protein activation lead to the formation of cAMP in vasodilation
Active G protein (Alpha-GTP) activates adenylate cyclase
Adenylate cyclase converts ATP into cyclic AMP (cAMP), which is the second messenger
cAMP then activates Protein Kinase A (PKA)
What does Protein Kinase A (PKA) do after activation in vasodilation
PKA inactivates Myosin Light Chain Kinase (MLCK)
When MLCK is not activated, Myosin Light Chain (MLC) is not activated
This results in smooth muscle relaxation and vasodilation (if in blood vessels)
How does epinephrine binding lead to vasoconstriction?
Epinephrine (ligand) binds to a Gi protein coupled receptor and alpha 1 receptor
The alpha subunit of the G protein binds GDP → Inactive state
Ligand binding causes GDP to be replaced with GTP, activating the G protein
The active G protein inhibits adenylate cyclase, preventing cAMP formation
What happens when adenylate cyclase is not activated?
No cAMP is produced
MLCK (Myosin Light Chain Kinase) is not inactivated
MLCK activation leads to MLC (Myosin Light Chain) activation
MLC activation causes smooth muscle contraction, resulting in vasoconstriction
How do different types of receptors affect vasoconstriction and vasodilation?
Beta-2 receptors (B2) are coupled to Gs (stimulatory protein), which causes vasodilation
Alpha-1 receptors (α1) are coupled to Gi (inhibitory protein), which causes vasoconstriction
How is the response terminated to prevent prolonged muscle relaxation or contraction?
Phosphodiesterase (PDE) enzyme is used to convert cAMP into non-cyclic AMP
This prevents cAMP from continuously activating the pathway
Some hormones can also stimulate the formation of cGMP, which can be converted into GMP by PDE
What happens when a hormone binds to its receptor on the cell membrane?
The Ligand (can be hormone, neurotransmitter, or toxin) binds to the receptor on the cell membrane (first messenger)
This binding activates the G protein (Gq type) inside the cell
How does the Gq protein become active and what does it do?
Gq-alpha is initially bound to GDP (inactive form)
When the ligand binds to the receptor, it causes GDP to be replaced with GTP, activating the Gq protein (Gq-alpha-GTP)
Gq-alpha-GTP activates phospholipase C
How does the activation of IP3 lead to smooth muscle contraction?
IP3 binds to receptors on the sarco/endoplasmic reticulum (SR)
This binding causes Ca2+ to be released into the cytoplasm
Ca2+ activates calmodulin, a calcium-binding protein
Calmodulin then activates MLCK (Myosin Light Chain Kinase)
MLCK activates MLC (Myosin Light Chain), causing cross-bridge formation and smooth muscle contraction
What does phospholipase C do after being activated by Gq-alpha-GTP?
Phospholipase C breaks down phospholipids into second messengers: IP3 (Inositol-1,4,5-triphosphate) and DAG (Diacylglycerol)
Diacylglycerol activate PKC (Protein Kinase C) and open calcium channels
IP3 (Inositol triphosphate) → Releases Ca²⁺ from the endoplasmic reticulum. n ca2+ binds to protein (calmodulin) w activates it that will then activate MLCK
VASOCONTRICTION aka smooth muscle contracts
What are some examples of G protein-coupled receptors (GPCRs)?
Olfactory receptors (nose)
Rod and cone receptors (eyes)
Gustatory receptors (taste receptors on the tongue)
Adrenergic receptors (bind epinephrine or norepinephrine)
What are the effects of adrenergic receptors?
Beta 1 (B1): Increases heart rate
Beta 2 (B2): Causes vasodilation
Alpha 1 (A1): Causes vasoconstriction
Alpha 2 (A2): wasnt on there
What hormones are secreted by the pineal gland?
Melatonin
What hormones are secreted by the hypothalamus?
Inhibiting and releasing factors like TRH, CRH, GH-RH, SRIF
ADH (Antidiuretic hormone)
Oxytocin (OT)
helps remin homeostasis
What hormones are secreted by the anterior pituitary?
Prolactin and the -tropins: DOES THIS HOLD TRUE?
Somatotropin (Growth hormone)
Corticotropin (ACTH)
Thyrotropin (TSH)
Gonadotropins (FSH, LH)
Melanotropin (MSH, involved in melanin production)
What hormones are secreted by the posterior pituitary?
ADH (Antidiuretic hormone)
Oxytocin (OT)
(Both are made in the hypothalamus and released into the blood by the posterior pituitary.)
What hormones are secreted by the parathyroid glands?
PTH (Parathyroid hormone), which increases calcium levels in the blood (causing hypercalcemia)
What hormones are secreted by the pancreas?
Insulin
Glucagon
Somatostatin
What hormones are secreted by the gonads (ovaries/testes)?
Androgens
Estrogens
What hormones are secreted by the thyroid gland?
T3 (Triiodothyronine)
T4 (Thyroxine)
Calcitonin (lowers calcium levels in blood, hypocalcemia)
What hormone is secreted by the thymus gland?
Thymosin (important for maturation of T cells)
What hormones are secreted by the adrenal glands?
Medulla: Catecholamines (epinephrine, norepinephrine, dopamine)
Cortex: Cortisol, Aldosterone (important for sodium retention)
What hormone is secreted by the kidneys?
Erythropoietin (stimulates red blood cell production)
What hormone is secreted by the heart?
Atrial natriuretic peptide (ANP), which lowers blood pressure
What are the two portions of the pituitary gland and their functions?
Adenohypophysis (anterior pituitary): Secretes hormones like GH, ACTH, TSH, FSH, LH, MSH, and prolactin
Neurohypophysis (posterior pituitary): Releases ADH and oxytocin (produced by the hypothalamus)
What hormones are produced by the specific cells in the adenohypophysis aka anterior pituitary?
Somatotropes: Somatotropin (GH)
Corticotropes: Corticotropin (ACTH)
Gonadotropes: FSH and LH
Thyrotropes: Thyrotropin (TSH)
Melanotropes: Melanotropin (MSH)
Lactotropes: Prolactin
What are the two main divisions of the pituitary gland?
Adenohypophysis (anterior lobe)
Neurohypophysis (posterior lobe)
What is the structure of the pituitary gland?
Located at the base of the brain, below the hypothalamus.
Infundibular stalk connects the hypothalamus to the pituitary.
Adenohypophysis (anterior lobe): Develops from the mouth via Rathke’s pouch.
Neurohypophysis (posterior lobe): Derived from the nervous tissue, contains pars nervosa.
Pars intermedia: The middle lobe, usually small or absent in adults.
What are the three lobes of the pituitary gland?
Pars distalis (anterior lobe): Secretes most hormones.
Pars intermedia (middle lobe): Small or absent in adults, produces MSH.
Pars nervosa (posterior lobe)
What hormones are produced in the anterior pituitary (pars distalis)?
Prolactin
Growth Hormone (GH)
Thyroid-Stimulating Hormone (TSH)
Adrenocorticotropic Hormone (ACTH)
Follicle-Stimulating Hormone (FSH)
Luteinizing Hormone (LH)
What hormones are produced in the posterior pituitary (pars nervosa)?
Antidiuretic Hormone (ADH)
Oxytocin (OT)
What is Rathke’s pouch, and what role does it play in the pituitary gland development?
Rathke’s pouch is an outpouching from the mouth during fetal development.
It gives rise to the adenohypophysis (anterior pituitary).
How do the hormones ADH and oxytocin reach the posterior pituitary (pars nervosa)?
Hormones are produced by neurosecretory cells in the hypothalamus.
These hormones travel along axons (nerve fibers) and are stored and released in the pars nervosa into the bloodstream.
What is the function of the infundibular stalk?
It connects the hypothalamus to the pituitary gland, allowing communication between the two.
What happens when there is a tumor in the pituitary gland? How is a pituitary tumor treated?
The tumor may grow upward, pressing against the optic chiasma, causing vision problems bc of sella turcia enclosing the pituitary allowing nowhere else to go but up
Surgery (hypophysectomy) can be done through the nose to remove the tumor, as it is difficult to approach from the sides or top due to surrounding structures.
What is the role of the pituitary gland (anterior and posterior) in hormone release?
The anterior pituitary (pars distalis) secretes hormones that regulate growth, metabolism, reproduction, and stress response.
The posterior pituitary releases hormones like ADH and oxytocin, which are important for water balance and uterine contractions during childbirth.
What is the function of somatotropin (growth hormone)?
Somatotropin (GH) stimulates the liver to produce somatomedins (IGF-1 & IGF-2).
IGF-1 stimulates bone elongation at the epiphyseal plate, leading to increased height.
How does estrogen affect bone growth during puberty?
Estrogen inhibits osteoclasts, cells that break down bone.
This results in reduced bone resorption, allowing bones to grow and increasing height, which is why females grow faster than males during puberty.
What is the condition caused by the excess of growth hormone (GH) in children?
Gigantism: Excess GH in children leads to abnormal growth and large size.
Acromegaly: In adults, excess GH leads to progressive enlargement of hands and jaw, but height cannot increase because growth plates are closed after puberty.
What happens in the case of a pituitary gland removal and what is it called:
(hypophysectomy)
Removal of the pituitary gland can result in the absence of GH, leading to dwarfism.
also can remove tumor by nose
What is the role of Thyroid-Stimulating Hormone (TSH)?
TSH (Thyrotropin) stimulates the thyroid gland to secrete T3 and T4, which regulate basal metabolic rate (BMR).
Negative feedback: High levels of T3/T4 inhibit the secretion of TSH.
What is the role of Adrenocorticotropic Hormone (ACTH)?
ACTH stimulates the adrenal cortex to secrete cortisol and DHEA (Dehydroepiandrosterone).
DHEA is converted to testosterone and then into Dihydrotestosterone (DHT).
What is the function of Gonadotropins (FSH and LH)?
FSH (Follicle-Stimulating Hormone): In females, stimulates follicular maturation and the release of the Graafian follicle during the menstrual cycle.
LH (Luteinizing Hormone): Triggers ovulation and the release of the secondary oocyte, which becomes the ovum after fertilization.
In males, FSH promotes spermatogenesis, while LH stimulates testosterone secretion from Leydig cells.
What was the condition of Robert Pershing Wadlow, the tallest man ever recorded?
He was 8’11” tall and suffered from gigantism due to an overproduction of growth hormone (GH).
He died at age 22, weighing 520 pounds.
What hormones are secreted by the hypothalamus
mostly release hormones, somatostatin and PIF:
TRH (Thyrotropin-Releasing Hormone)
CRH (Corticotropin-Releasing Hormone)
GnRH (Gonadotropin-Releasing Hormone)
GH-RH (Growth Hormone-Releasing Hormone)
Somatostatin (SRIF)
PIF (Prolactin-Inhibiting Factor/Dopamine)
What hormones are secreted by the hypothalamus and their respective functions?
TRH (Thyrotropin-Releasing Hormone): Stimulates the pituitary to release TSH (Thyroid-Stimulating Hormone), which then stimulates the thyroid to release T3 and T4.
CRH (Corticotropin-Releasing Hormone): Stimulates the pituitary to release ACTH (Adrenocorticotropic Hormone), which then stimulates the adrenal cortex to release cortisol and DHEA.
GnRH (Gonadotropin-Releasing Hormone): Stimulates the pituitary to release FSH and LH, which act on the ovaries (follicular maturation and secondary oocyte release) and testes (spermatogenesis and testosterone production).
GH-RH (Growth Hormone-Releasing Hormone): Stimulates the pituitary to release growth hormone (somatotropin), which acts on the liver and other tissues.
Somatostatin (SRIF): Inhibits the release of growth hormone.
PIF (Prolactin-Inhibiting Factor/Dopamine): Inhibits the release of prolactin.
What is the role of tyrosine in thyroid hormone synthesis?
Tyrosine is the amino acid that serves as the backbone for thyroid hormone production.
What is the process of iodination (organification)?
Iodine attaches to the carbon #3 on tyrosine, forming monoiodotyrosine (MIT). A second iodine attaches to carbon #5, forming diiodotyrosine (DIT) these combine ot make t3/t4
What is coupling in thyroid hormone synthesis?
MIT + DIT = T3 (Triiodothyronine, the most potent form)
DIT + DIT = T4 (Thyroxine, the most abundant form in circulation)
Which thyroid hormone is most potent?
T3 (Triiodothyronine) is the most potent.
Which thyroid hormone is most abundant?
T4 (Thyroxine) is the most abundant in circulation.
Do MIT and DIT leave the cell?
No, only T3 and T4 are secreted into circulation.
How is thyroid hormone (T3/T4) regulated?
The hypothalamus releases TRH (Thyrotropin-Releasing Hormone).
TRH stimulates the pituitary to release TSH (Thyroid-Stimulating Hormone).
TSH stimulates the thyroid to produce T3 (Triiodothyronine) and T4 (Thyroxine).
Negative feedback: High T3/T4 levels inhibit TRH and TSH release.
What causes Graves’ disease and what are its symptoms?
(Hyperthyroidism)
Autoimmune antibodies (Ig) mimic TSH, stimulating excessive T3/T4 production.
Symptoms:
Toxic goiter (thyroid enlargement).
Exophthalmos (bulging eyes).
High BMR, sweating, warm skin, rapid heart rate.
What are the effects of hypothyroidism?
Cretinism (infants): Stunted growth, neurological & gonadal defects.
Myxedema (adults): Puffy face, lethargy, cold intolerance, low cardiac output.
Hashimoto’s Thyroiditis: Autoimmune thyroid destruction, causing low T3/T4.(very common)
Endemic Goiter: Iodine deficiency leads to a non-toxic thyroid enlargement.
How does the body regulate blood calcium levels?
PTH (Parathyroid Hormone):
Increases blood calcium by stimulating osteoclasts to break down bone (bone reabsortion) which release calcium into bloodstream Regulates calcium for muscle contraction, heart function, nerve signaling.
Calcitonin (from thyroid C cells):
Lowers blood calcium by stimulating osteoblasts to deposit calcium into bones, remcing calcium from blood stream
What happens with too much PTH
Hyperparathyroidism (too much PTH):
Causes osteoporosis (soft, weak bones) due to excessive bone resorption.
What happens with too little PTH?
Hypoparathyroidism (too little PTH):
Leads to muscle twitching, convulsions
How do Vitamin D3 and estrogen affect bone health?
Vitamin D3: Helps absorb calcium in intestines; deficiency causes Rickets.
Estrogen: Inhibits osteoclasts, preventing bone resorption.
Menopause: No estrogen → Increased osteoclast activity → Osteoporosis.
What are the two main portions of the adrenal gland
Adrenal Medulla (inner) and Adrenal Cortex (outer part)
What happens when females produce too much DHEA?
Excess DHEA → Increased testosterone levels.
Symptoms:
Hirsutism (male-pattern hair growth).
Virilization (deep voice, masculinized features & behaviors).
What causes Cushing’s syndrome, and what are the symptoms?
Cause: Overactive adrenal cortex → Excess cortisol, aldosterone, or DHEA.
Symptoms:
Buffalo hump (fat buildup on upper back).
Striae (stretch marks) → Skin thinning due to collagen breakdown.
What happens when the adrenal cortex is underactive?
Low cortisol & aldosterone → Sodium & water loss → Low blood volume & BP.
Symptoms:
Hypotension (low BP), salt cravings.
Hyperpigmentation (dark skin spots from excess melanin).
What are the two main portions of the pancreas?
Exocrine pancreas: Produces digestive enzymes.
Endocrine pancreas: Regulates blood glucose.
What does the exocrine pancreas do?
Contains acinar cells.
Produces digestive enzymes:
Trypsin & chymotrypsin (protein digestion).
Lipase (fat digestion).
Bicarbonate (neutralizes stomach acid).
What is the endocrine pancreas responsible for?
Contains Islets of Langerhans.
Regulates blood glucose levels.
What are the three types of cells in the Islets of Langerhans?
Alpha cells (glucagon).
Beta cells (insulin).
Delta cells (somatostatin).
What does glucagon do?
Increases blood glucose (prevents hypoglycemia).
Stimulates glycogen breakdown (glycogenolysis).
Promotes glucose production from proteins (gluconeogenesis).
What does insulin do?
Lowers blood glucose.
Promotes glycogen storage (glycogenesis).
Stimulates fat storage (lipogenesis).
Facilitates glucose oxidation for ATP production.
What is the function of somatostatin?
Inhibits glucagon & insulin release.
Regulates growth hormone (GH) secretion.
What are the three main carbohydrate metabolic processes?
Glycolysis: Glucose → ATP.
Glycogenesis: Glucose → Glycogen (storage).
Glycogenolysis: Glycogen → Glucose (energy release).
What is gluconeogenesis?
Formation of glucose from non-carbohydrates (proteins).
Helps maintain blood glucose levels.
How are lipids processed for energy?
Lipogenesis: Glucose → Fat storage (triglycerides).
Beta-oxidation: Fatty acids → Acetyl-CoA → ATP.
How are proteins broken down for energy?
Deamination: Amino acids → Alpha-keto acids + NH₃.
NH₃ is toxic and converted to urea for excretion.
What is transamination?
Amino acid is converted into a different amino acid via alpha-keto acids.
Helps with protein metabolism & energy production.
What happens when Acetyl-CoA accumulates?
Converts into ketone bodies (used as an alternative energy source).
What regulates glycogenesis and glycogenolysis?
Glycogenesis (glucose → glycogen) → Under insulin.
Glycogenolysis (glycogen → glucose) → Under glucagon & epinephrine.
How do lipids break down and store energy?
Lipogenesis: Glucose → Fats (Under insulin).
Lipolysis: Breakdown of fats into free fatty acids (Under glucagon).
What is the main goal of intermediary metabolism?
To generate ATP for sustaining life.
How much ATP is produced in glucose oxidation?
Complete oxidation → 36–38 ATP.
Glycolysis (pyruvic acid stage) → 2 ATP.
What are the two main types of diabetes mellitus?
Type 1 (Juvenile, Insulin-Dependent) & Type 2 (Adult-Onset, Insulin Resistance)
Type 1 (Juvenile, Insulin-Dependent)
No beta cells → No insulin.
Requires lifelong insulin therapy.
Causes hyperglycemia, ketosis, ketonemia, acidosis.
Type 2 (Adult-Onset, Insulin Resistance)
Insulin is present but receptors don’t respond.
Causes hyperglycemia, polydipsia (excess thirst), polyuria (frequent urination).
ways to fix it? = Reduce sugar intake or get drug called Sulfonylureas → Helps beta cells release insulin.
What is gestational diabetes and when does it occur?
Occurs during pregnancy (24–26 weeks).
Caused by placental hormones (estrogen, cortisol, placental lactogen) being less responsive to insulin
Resolves after childbirth.
What does the thymus gland do?
Matures T-cells → Develops immunological memory (recognizes self vs. foreign).
What does the pineal gland produce and its functions?
Produces melatonin → Secreted in darkness.
Functions:
Regulates sleep.
Anti-aging.
Antioxidant.
Anti-gonadal effects.
What is the role of hCG?
Stimulates the placenta to produce progesterone.
Detected in pregnancy tests (only present during pregnancy). the stip has anti bodies against hCG to show whether preg or not
What are the key hormones of the GI tract?
i didnt add the functions
Ghrelin → Stimulates hunger.
VIP (Vasoactive Intestinal Peptide) → Relaxes smooth muscles, increases secretion.
Somatostatin → Inhibits gastric secretions & motility.
GIP (Gastric Inhibitory Peptide) → Stimulates insulin release.
GLP-1 (Glucagon-Like Peptide-1) → Increases insulin, decreases appetite.
Motilin → Stimulates gastric & intestinal motility.
Secretin → Increases bicarbonate secretion from the pancreas.
CCK (Cholecystokinin) → Stimulates bile & pancreatic enzyme secretion.
What hormone does the kidney produce and its function?
Erythropoietin (EPO) → Stimulates red blood cell (RBC) production in the bone marrow.
What does the skin produce that is important for calcium metabolism?
Vitamin D3 (Cholecalciferol) → Helps in calcium absorption and bone health.
What does the liver produce in response to growth hormone?
Somatomedins (IGF-1, IGF-2) → Stimulated by growth hormone (GH) from the pituitary gland.
Function: Bone elongation & height increase.
cretinism
caused by low t3/t4 (hypothryoidism aka low thyroid hormone levels)
-PGI2 (Prostacyclin):
type of progostalandins :
-PGI2 (Prostacyclin): Vasodilation and prevents blood clotting
-TXA2 (Thromboxane A2):
Vasoconstriction and promotes blood clotting
how to peptide/protein hormones produce their effects on cells.
eg. insulin
Receptors are located on the cell surface.
Bind to receptors, triggering a second messenger system inside the cell (e.g., cAMP, calcium).
This pathway activates cellular processes and responses.
how do steroid hormones
eg estrogen, cortisol
Receptors are found inside the cell (cytoplasm or nucleus).
Bind to the receptor, which then interacts with DNA to regulate gene expression.
This leads to the synthesis of specific proteins that bring about the cell’s response.
2 types of surface receptors
- ion channels: Acetylochine receptors
Adenylate Cyclase
Adenylate Cyclase (AC) is an enzyme that converts ATP → cAMP (cyclic AMP).
peristalsis
movement of food; wave-like contractions that move food down the digestive tract
in vomiting, peristalsis reverses.
Rathke’s pouch
makes up main part of pituary gland and gives rise to andeohyphysis (anterior lobe)
- small pocket in an embryo that turns into the front part of the pituitary gland.
Optic chiasma:
in hypothalumus where the optic nerves cross.
sella turcia
pituary enclosed in boney capsule
Osteoclasts
cells responsible for bone resorption, which is the process of breaking down bone tissue to release minerals (like calcium) into the bloodstream.
Calcitriol
(increases Ca²⁺ absorption in the intestine). Works with parathyroid hormone (PTH) to prevent hypocalcemia (low calcium levels).
Beta-Oxidation
fatty acids are broken down into acetyl-CoA, which can then enter the citric acid cycle (Krebs cycle) to produce ATP (energy).
Gi, Gs,Gq
gi= alpha1 = vasocontriction
gs & b2=vasodiliation = - camp inhibits mlck so muscle dont contract
gq=vascoconstriction
