Endocrine: Module I Flashcards
What are the primary organs of the endocrine system?
Hypothalamus Pituitary gland (hypophysis) Thyroid gland Parathyroid glands Adrenal glands Pancreas Gonads Placenta *Hormones also secreted from other organs such as heart, kidney, GI...
What are the 4 functions of the Endocrine system?
- Homeostasis
- Control of the storage and utilization of energy substrates
- Regulation of growth, development, and reproduction
- Regulates the body’s response to environmental stimuli
Compare/contrast the actions of the endocrine system with the actions of the nervous system
Actions of endocrine system are:
- -> slower in response
- -> have a prolonged response
- -> more “diffuse”
What are the 3 components of the endocrine system?
- Endocrine Glands
- Target Organs
- Hormones
Endocrine glands are….
ductless glands that secrete hormones into the blood stream
Target organs…
contain cells with receptors that have hormone specific receptors
Define hormones
Chemical messengers released by one cell and exert a biological action on a target cell
Describe how hormones work at different target tissues to mediate function
- A single hormone can facilitate multiple effects
2. A single physiological function can be regulated by multiple hormones
Name an example of a hormone that elicits different effects on different target tissue
Epinephrine
At alpha receptors in intestine: constriction
At beta receptors in skeletel muscle: dilation
At beta receptors in liver: glycolysis
Blood pressure is influenced by …
ADH, aldosterone, epinephrine, and more.
Name the 4 types of hormone signaling
- Endocrine
- Paracrine
- Autocrine
- Intracrine
Endocrine signaling
Classically referred toa s the endocrine system
Target tissue = distance
hormones travel through the blood stream to reach target tissue
Example of endocrine signaling
Insulin
Thyroid hormones
Paracrine signaling
Target tissue = “local” or immediate nearby cells
A hormone that travels through the blood stream to reach its target tissue is the definition of ______ _______.
Endocrine signaling
A hormone that is released by one cell and acts locally on a nearby cell is an example of _____ ______.
Paracrine signaling
List 5 examples of paracrine signaling
- Nitric oxide
- Bradykinin
- Neurotransmitters
- Cytokines
- Prostaglandins
What does nitric oxide promote?
BV Vasodilation
Describe the actions of bradykinin
Promote BV vasodilation
Describe cytokines function
Immunoregulating and growth function
Contain interleukins, TNF (tumor necrosis factor), interferon, growth factors, TGF (transforming growth factors, etc
____ are fatty acids produced in most organs
Prostaglandins
What are the 6 main functions of prostaglandins?
- Smooth muscle - contraction/relaxation depending on receptor type/tissue
- Inflammatory response throughout tissues in the body
- Pain
- Kidney: mesangial cells contract and alter GFR
- Hypothalamus: termoregulatory nuclei produce fever
- Mediate platelet aggregation/disaggregation
______ decrease inflammation via prostaglandins.
NSAIDs
Autocrine signaling
Target tissue = same cell
Hormone is released by a cell and then acts on the same cell that released it
Intracrine signaling
Hormone produced in a cell that acts WITHIN the cell itself
Example of intacrine signaling
- Steroid action
2. Malignant pathways
Describe negative feedback using the example of insulin secretion.
When insulin is released, blood glucose is decreased.
The decreased blood glucose inhibits further insulin release
What are the two variations of negative feedback loops
- Inc. levels of hormone inhibit the hormone’s releasing factor
- Inc. levels of hormone inhibit the hormone’s releasing factor AND stimulate hormone’s inhibiting factor
Positive feedback is rare. Describe a popular example of positive feedback
LH (luteinizing hormone)
Increased estrogen stimulates release of LH….LH in turn stimulates release of estrogen from ovaries
Hormones are classified by _______ or ________.
Derivative content
Solubility
What are the 4 types of derivative content hormones?
- Amino acid derivatives
- Peptide/protein derivatives
- Steroid derivatives
- Fatty acid derivatives - eicosanoids
What are the two types of solubility hormones?
- Lipid soluble (lipophilic)
2. Water soluble (hydrophilic)
What are two type of lipid soluble (lipophilic) hormones?
Steroid hormones and thyroid hormones
_____ is a precursor for all of the steroid hormones
Cholesterol
Describe the half life of lipid soluble hormones
They circulate in plasma via binding to plasma proteins thus having a longer half life (hours to days) because they don’t break down as easily
*This hormone/protein carrier disassociate at target tissues
Describe the half life of water soluble hormones
They circulate “freely” in plasma so they are easily broken down and thus have a shorter half life (1-30 mins)
Are hormone receptors fixed or changing?
CHANGING!!
Up-regulation: what is it and what is the net result?
When low concentrations of a hormone will increase the number of receptors on target tissue
Net result = increased sensitivity to hormone
Down-regulation: what is it and what is the net result?
High concentrations of hormone will decrease number of receptors on the target tissue
Net result: decreased sensitivity to hormone
Where are hormone receptors located?
On cell membrane or within cell itself (either in cytosol or nucleus)
In response to regular exercise when cells become more sensitive to insulin is an example of ______ regulation
Up regulation
In response to a sedentary lifestyle and obesity when cells become less sensitive to insulin is an example of ___ regulation
Down regulation
The process by which extracellular signals (hormones) are communicated into a cell
Signal Transduction
What are the two types of signal transduction?
- Primary messenger “First messenger”
2. Secondary messenger
Where are target tissue receptors located for primary messengers?
Located within the cell itself
What type of hormones use primary messengers?
Fat soluble
–> they can easily diffuse across cell membranes to communicate to receptors within the cell
What is a secondary messenger?
It is the “link” between primary messenger (hormone) and inside of the cell
How do secondary messengers work?
Hormone attaches to receptor on cell membrane which produces SECONDARY MESSENGERS to communicate to structures inside the cell
What type of hormones require secondary messengers? Why?
Water soluble
They can’t diffuse across membrane
What are some examples (3) of secondary messengers?
- cAMP
- calcium
- cGMP
What is the hypophyseal portal system?
Capillaries in hypothalamus communicate with pituitary capillaries before entering venous system
Describe the general schematic of the anterior pituitary
Hypothalamus releases “pituitary releasing hormones” that descend through hypophyseal portal system. Most hormones from hypothalamus stimulate or inhibit release of pituitary hormones
Describe the general schematic of the posterior pituitary
Hypothalamic nuclei synthesize pituitary hormones that descend to pituitary via direct neural connection to posterior pituitary
What are the 2 hormones produced in the posterior pituitary?
ADH
Oxytocin
The hypothalamus “links” ____ to _____ _______.
CNS
Endocrine system
Where is the hypothalamus located?
Diencephalon of CNS
Name the 8 hormones released from hypothalamus that control anterior pituitary gland
- TRH
- GnRH
- Somatostatin
- GHRH
- CRH
- Substance-P
- Dopamine
- PRF
Thyrotropin releasing hormone (____) __________ the release of: _________.
TRH
Stimulates
TSH (thyroid stimulating hormone
GnRH (_______) ______ the release of _______ and _______.
Gonadotropin releasing hormone
Stimulates
- LU (luteinizing hormone)
- FSH (follicle stimulating hormone)
Somatostatin ______ the release of _____ and ______.
GH (somatotropin)
TSH (thyroid stimulating hormone)
GHRH (_______) ______ the release of ______.
Growth hormone releasing hormones
GH (growth hormones)
CRH (________) ______ the release of _____ and _____.
Corticotropin releasing hormone
ACTH (adrenocorticoptropic hormone)
Beta-endorphin
Substance-P _______ synthesis/release of _____ and ____ release of ____, ____, ____, and ____.
Inhibits ACTH (adrenocroticotropic hormone) Stimulates GH FSH LH Prolactin
Dopamine ____ release of _____.
Inhibits
Prolactin
PRF (_______) _____ release of _____.
Prolactin releasing factor
stimulates
Prolactin
What are the hormones synthesized in nuclei of hypothalamus and descend to posterior pituitary gland?
ADH and Oxytocin
The other name for the pituitary gland is _____.
Hypophysis
The anterior pituitary is also known as ______.
adenohypohysis
What are the 3 regions of the anterior pituitary
- Pars distalis
- Pars tuberalis
- Pars intermedia
Posterior pituitary is also known as ______.
Neurohypophysis
What is the pituitary’s function (both anterior and posterior)
Regulates the activity of endocrine glands in the body
–> regulates growth, metabolism, reproduction, lactation, fluid balance, and response to stress
Anatomy of posterior pituitary gland: 3 regions
- Median eminence
- Infundibular stem or pituitary stem
- Infundibular process (aka pars nervosa, neural lobe, posterior lobe)
Median eminence (location)
located at base of hypothalamus
Infundibular stem or pituitary stem
Neural connection between hypothalamus
What does the infundibular stem contain?
Neural axons that originate in hypothalamus
Infundibular process
Axons that originate in hypothalamus terminate in posterior lobe
Site of hormone release!!
What is the female function of oxytocin?
Stimulates milk ejection and uterine contraction
synthetic versions induce labor
What is the male function of oxytocin?
May have a role in sperm motility
Target tissue of oxytocin
Mammary gland
Uterus
3 stimuli for oxytocin release
- Distension of cervix at end of pregnancy
- Breast stimulation
- Positive emotional responses
Oxytocin utilizes ____ feedback system.
Positive
What can cause inhibition of oxytocin release
- External stimulus stopping
2. Negative emotional factors
3 Clinical applications of oxytocin
- Induce labor –> Pitocin, Misoprostol
- Diseases of excess oxytocin are UNCOMMON
- Oxytocin deficiency will impair nursing
- -> true or stress initiated?
Function of ADH
Control osmolality/osmolarity of plasma
Increase blood volume
Target tissue of ADH
Collecting ducts in kidney (DCT and collecting duct)
–> increases water reabsorption by increasing permeability of collecting duct
Difference between osmolality and osmolarity
Osmolality - amount of solute (electrolytes) per kg of solvent (plasma)
Osmolarity - amount of solute (electrolytes) per liter of solvent (plasma)
ADH promotes blood vessel ______.
Contraction (elevates BP)
5 stimuli for release of ADH
- Increased plasma osmolarity
- Decreased blood volume
- Angiotensin II (indirectly)
- Stress, trauma, exercise, heat
- Various drugs (nicotine, morphine, etc)
ADH is also termed as ______ or ______.
Vasopressin Arginine Vasopressin (AVP)
Which of the stimuli for release of ADH is the most sensitive?
Plasma osmolarity
1% change in osmolality will stimulate release of ADH
What senses plasma changes?
Osmoreceptors in hypothalamus
What senses blood volume change and how effective are these receptors in stimulating ADH release.
Mechanoreceptors (baroreceptors) in atria, aortic arch and carotid sinus
Not as effective as osmoreceptors in hypothalamus. 10% drop in blood pressure to stimulate release of ADH
How does angiotensin II stimulate ADH release?
Angiotensin II increases sensitivity of osmoreceptors in hypothalamus
Also stimulates thirst centers in hypothalamus
3 ways to inhibit ADH release
- Decreased plasma osmolality
- Increased blood volume/pressure
- Alcohol and caffeine
Clinical: too little or ineffective ADH is _____ _____.
Diabetes Insipidus
Two types of diabetes insipidus
Central DI
Nephrogenic DI
Central Diabetes Insipidus
Most common form of DI
Decreased release of ADH from posterior pituitary
Nephrogenic DI
Less common form of DI
Inability of kidneys to respond to ADH
Signs/Symptoms of DI
Polyuria (excessive urine)
Polydipsia (excessive thirst)
Medications for Diabetes Insipidous (central)
Desmopressin
Clinical: too much ADH is _____________.
Syndrome of inappropriate ADH secretion
SIADH
What does excessive ADH release cause?
Water reabsorption in DCT/collecting duct –> hypervolemia
Hyponatremia
decreased sodium values in blood stream
Hypervolemia facilitates what 2 things?
- Hyponatremia
2. Natriuresis
Natriuresis
Excessive sodium excretion
The expansion of extracellular fluid volume reduces sodium resorption in kidney –>
Baroreceptors in atria/aorta release ANP which reduces sodium resorption –>
Decreased aldosterone release which reduces sodium resorption in kidney
3 Etiologies of SIADH
- Tumors (they secrete ADH themselves)
- Head injuries or meningitis
- Bronchiogenic tumors and diabetes mellitus
Pars distalis
Forms most of the anterior pituitary gland itself
Anterior pituitary hormones synthesized and secreted
Pars tubularis
Thin layer of cells that wraps around anterior/lateral infundibular stem
Pars intermedia
Small layer of cells located between pars distalis and pars nervosa
“disappears” in adult
3 Functions of Prolactin
- Breast development during puberty and pregnancy
- Stimulates milk production after birth (lactogenesis)
- Inhibits ovulation
Prolactin target tissue
Mammary glands during puberty, pregnancy and while lactating newborn
5 stimuli of prolactin release
- Puberty
- Pregnancy
- Lactation
- Sleep
- Dopamine antagonist
Inhibition of prolactin release (3)
- Constant tonic release of dopamine
- Dopamine agonists –> bromocriptine
- Discontinuation of stimuli
When is growth hormone (GH) released and how is it released?
Released in pulsing/cyclic pattern
Peaks during adolescence
Functions of growth hormone
- Stimulates all tissue growth and maturation
2. Also plays role in aging, sleep, reproductive hormone function
Target tissue of growth hormone
- Direct effect on tissues via GH receptors (liver, muscle, adipose)
- Indirect effect on tissue via the IGF-1 pathway
Target tissue of IGF-1
Bone, cartilage, visceral organs
Actions of Growth Hormone
- Liver
- Adipose tissue
- Muscle
Actions of IGF-1
Mediate cell growth in most tissues of the body. It also has inhibitory (antagonistic) effect on tissue growth
