The Endocrine System Flashcards
Endocrine vs. Exocrine
Endocrine = secreted into circulatory system Exocrine = secreted into ducts
Exocrine glands
Sweat glands (sweat) Sebaceous gland (skin oil) Ceruminous glands (earwax) Mammary glands (breast milk) Salivary glands (saliva) Lacrimal glands (tears) Mucous glands (mucus)
Endocrine glands
Hypothalamus Pituitary gland Thyroid gland Parathyroid Adrenal cortex Medulla Pancreas Gonads
Both Exocrine and Endocrine
Pancreas
Liver
Pancreas
Exocrine –> Digestive enzymes through ducts
Endocrine –> hormones like insulin and glucagon
Liver
Exocrine –> secretes bile through bile duct
Endocrine –> secretes hormones like angiotensinogen
Paracrine signaling
Signaling molecule that acts on nearby cells
Involved in differentiation in embryonic development
Endocrine signaling
Long-distance effects
Juxtacrine signaling
More local than paracrine
Merocrine
secretion through exocytosis
Eccrine
Merocrine cells in sweat glands
Holocrine
Secretion from rupture of the plasma membrane destroying the cell and releasing its product from the cytoplasm into the lumen
Peptide hormones
Polypeptide chain
Chain of amino acids
Hydrophilic
Steroid hormones
Lipid cholesterol
4 ring structure
Peptide hormone characteristics
Rapid onset
Short-term
Hydrophilic
Diffuse freely in the blood
Cannot diffuse freely across the lipid bilayer membrane of their target cells
Receptors on outside of cell membrane –> conformational change –> effect on target (effector) through 2nd messenger (cAMP, cGMP, or IP3)
Steroid hormones characteristics
Slow onset
Long-term
Hydrophobic
Not soluble in the bloodstream
Require transport proteins
Diffuse directly through the lipid bilayer of the cell membrane
In cell, bind to nuclear receptors –> conformational change –> translocated into nucleus –> complex bind to DNA and affect gene transcription
Second messenger system
Hormone is the first messenger results in signal cascade –> rapid amplification within cell –> impact on cellular function
Peptide hormone production
- Translated into preprohoromones
- Processed in Golgi
- Cleaved by endopeptidases and modified by addition of carbs
- Final active form of hormone
- Packaged into vesicles
- Released through exocytosis
Peptide hormone precursor
Amino Acids
Steroid hormone precursor
Cholesterol (lipid)
Peptide hormone size
Large but variable
Steroid hormone size
Small
Peptide hormone polarity
Polar
Steroid hormone polarity
Nonpolar
Peptide hormone hydrophobic or hydrophilic?
Hydrophilic
Steroid hormone hydrophobic or hydrophilic?
Hydrophobic
Peptide hormone synthesis location
Rough ER –> Golgi –> Vesicles –> Exocytosis
Steroid hormone synthesis location
Smooth ER
Peptide hormone intermediate stages
Yes – Preprohormones, prohormones, hormones
Steroid hormone intermediate stages
No
Peptide hormone solubility in blood
Soluble
Freely diffuse
Steroid hormone solubility in blood
Insoluble
Require transport protein
Peptide hormone receptor type
Membrane-bound receptor
Steroid hormone receptor type
Nuclear receptor
Peptide hormone mechanism of effect
Second messenger system in Cytosol
Steroid hormone mechanism of effect
DNA transcription in nucleus
Peptide hormone physio effects
Fast onset
Short-term
Steroid hormone physio effects
Slow onset
Long-term
Peptide hormone typical functions
Regulation of other hormones
Short-term responses
Steroid hormone typical functions
The 3 S’s:
Sex
Sugar [glucocorticoids
Salt [mineralcorticoids]
Peptide hormone examples
Thyroid-stimulating hormone
Oxytocin
Insulin
Calcitonin
Steroid hormone examples
Estrogen
Testosterone
Cortisol
Aldosterone
Amino acid - derived hormones
Small hormones
Ex: Tyrosine derivatives; Catecholamines
T3 & T4
Tyrosine derivative Lipid-soluble Behave like steroid hormones T3 = triiodothyronine T4 = thyroxine
Catecholamines
Tyrosine derivative
Epi / Norepi
Water-soluble
Act similar to peptide hormones
Melatonin
Tryptophan derivative
Regulates wakefulness cycles
Lipid-soluble AND Water-soluble
Topic hormones
Hormones that affect the release of other hormones
Nontropic hormones
Target other cell types and directly induce physiological effects
Negative feeback
Most common regulatory mechanism in the ENDOcrine system
Maintains homeostasis
Downstream product inhibits the pathway
