Endocrine System Flashcards
Endocrinology
Study of structure and function of endocrine glands and the diagnosis and treatment of disorders of the endocrine system
Hormone
Chemical messenger secreted by cells of endocrine tissue/gland into interstitial fluid
- diffuses into blood capillaries
- transported into bloodstream
- distributed to specific target cells with specific receptors
- effects target cells physiology
Endocrine glands
Pituitary, thyroid, parathyroid, adrenal glands, pineal glands
Organs with endocrine tissues
Hypothalamus, thymus, pancreas, ovaries, testes, kidneys, digestive tract, heart, adipose tissue, placenta
Tropic hormone
Act on other endocrine glands/tissue
- most secreted by anterior pituitary
- those secreted by hypothalamus act on anterior pituitary are also tropic hormones
Functions of hormones
- chemical composition of the ECF (e.g., insulin, calcitonin, aldosterone)
- metabolism and energy balance (e.h., thyroid and growth hormone)
- biological clock (e.g., melatonin)
- contraction of smooth and cardiac muscle (e.g., epinephrine)
- some immune system functions (cortisol)
- growth and development (e.g., growth hormone)
- regulate productive organs (e.g., estrogen, progesterone, testosterone)
Nervous System
Mediator molecules: neurotransmitters
Site of action: close to release site (synapse)
Types of target cells: Few cell types Neurons, muscle, glands
Time to onset of action: milliseconds
Duration of action: shorter (milliseconds)
Endocrine System
Mediator Molecules: hormones
Site of action: far from release site (anywhere in body)
Types of target cells: any body cells
Time to onset of action: seconds-days
Duration of action: longer (sec-days)
Anterior pituitary is also known as _____
Adenohypophysis
Pituitary gland is also known as _______
Hypophysis
5 releasing hormones from hypothalamus:
GnRH
GHRH
TRH
CRH
PRH
2 inhibiting hormones: PIH and somatostatin
GnRH is
Gonadotropin-releasing hormone
GHRH is
Growth hormone releasing hormone
TRH is
Thyrotropin-releasing hormone
CRH is
Corticotropin-releasing hormone
PRH is
Prolactin releasing hormone
PIH is
Prolactin inhibiting hormone
Somatostatin
Growth hormone inhibiting hormone
7 hormones from anterior pituitary
FSH
LH
TSH
ACTH
Prolactin
GH
MSH
FSH is
Follicle stimulating hormone
LH is
luteinizing hormone
TSH is
Thyroid Stimulating Hormone
ACTH is
Adrenocorticotropic hormone
GH is
Growth hormone
MSH is
Melanocyte-stimulating hormone
PRH
Hypothalamic hormone
Hypophyseal portal system
The blood connection between hypothalamus and the anterior pituitary
What is under control of hypothalamic tropic hormones
Anterior pituitary gland
Where does the pituitary gland sit?
Within the sella turcica of sphenoid bone
Attached to hypothalamus by infundibulum (a stalk)
Which part of the pituitary is larger?
The anterior pituitary
Antidiuretic Hormone
Acts on kidney tubules; detecting level of hydration and how much water to release or maintain
Anterior pituitary histology
Grows upward from primitive pharynx during embyrological development
Larger lobe of pituitary
Histology of posterior pituitary
Grows downwards from brain; composed of nervous tissue
Stores hormones made by the neurons in hypothalamus
Control of pituitary secretion (thyroid hormone as example)
1) hypothalamus secretes TRH
2)TRH stimulates anterior pituitary to secrete TSH
3) TSH stimulates the thyroid gland to secrete thyroid hormone(TH)
4) TH stimulates metabolism of most cells in the body
5) TH also inhibits the release of TSH by the anterior pituitary
6) to a lesser extent, TH also inhibits the release of TRH by the hypothalamus
steps 5 and 6 are negative feedback
Lipid soluble hormones
- need transport protein
- thyroid hormones
- eicosanoids
- steroid hormones
Water soluble hormones
- no transport protein needed
- catecholamines
- peptide hormones (majority of hormones)
Tryptophan derivative
- melatonin (ampiphatic)
Amphipathic meaning
Both water and lipid soluble
Thyroid hormones
- lipid soluble
- need transport proteins
Catecholamines
- epinephrine
- norepinephrine
- dopamine
- water soluble
All peptide hormones are __________
Water soluble
Anemia
- not enough RBC means not enough oxygen being circulated
- lack of ertyhtopoietin derived from kidney
Steroid hormones are synthesize from _____
Cholesterol
All steroid hormones are ____
Lipid soluble
Hormone Synthesis
-Gene for hormone is transcribed to mRNA molecule
-Ribosomes translate mRNA and assemble amino acids to make the peptide
-Further modification occurs to make the mature hormone molecule
Thyroid Hormone (TH) Synthesis and Secretion
1)Cells of thyroid follicle absorb iodide ions from blood capillaries and oxidize I- to reactive form I*
2)Follicle cells synthesize thyroglobulin(Tg) and release it into the lumen for storage
3)Enzyme at cell surface adds iodine to a few tyrosines
4)When follicle cells receives TSH from ant. pituitary they absorb Tg and lysosomal enzyme hydrolyzes Tg chain
5)TH is released from basal side of cell into blood capillaries and it binds to transport proteins to go to target cells.
Up regulation
Cell produces more receptors (increased density) and increases its own sensitivity to a hormone
Down regulation
Cell produces less receptors (decreased density) and decreases its sensitivity to a hormone
Modulation of target cell activity
- up regulation
- down regulation
Peptide hormone (water soluble) receptors
Acts via a surface receptor on cell membrane and a second messenger system
Steroid hormone (lipid soluble) receptor
Acts by diffusing into the nucleus and binding to a nuclear receptor associated with a gene
CAMP as a second messenger (peptides and catecholamines)
1) hormone receptor binding activates a G protein
2) G protein activates Adenylate cyclase
3) Adenylate cyclase produces cAMP
4) cAMP activates protein kinases
5) protein kinases phosphorylate enzymes which activate some and deactivate others
6) activates a enzyme catalyze metabolic reaction with wide range of effects of target cell
Peptide hormones (water soluble)
- receptors on surface of target cell membrane
- relies on second messenger system
- 1st messenger = hormone
- 2nd messenger depends on the hormone
- some use cAMP pathway, some use IP3, DAG, Ca2+ (all = types of second messenger systems)
Activation of phospholipids in plasma membrane (water soluble hormones)
1) receptor activated by certain hormones
2) receptor activates a G protein linked to a nearby enzyme, phospholiopase, in the plasma membrane
3) Phospholipase splits a membrane phospholipid into two fragments, inositol triphosphate (IP3) and diacylglyerol (DAG).
4) IP3 and DAG are the second messengers that go on to activate a wide variety of metabolic changes in target cells
5) DAG activates protein kinase (PK), much like cAMP does on the previous slide and PK phosphorylates other enzymes.
6) IP3 works by increasing the calcium concentration in the target cell. Calcium then acts to change cell physiology.
metabolic effects of phospholipids
- smooth muscle contraction
- protein synthesis
- secretion
- mitosis
-etc.
Role of insulin
Acts to promote glucose uptake, glycogen storage, and lowing of blood glucose (BG) level
Role of glucagon
Acts to promote glycogen breakdown, glucose synthesis, glucose release into blood, increasing BG level
- Breakdown of glucose
Glycogenesis
Synthesis of glycogen
Glycogenolysis
Breakdown of glycogen via hydrolysis (addition of water)
Gluconeogenesis
Synthesis of glucose from non carbohydrates, especially fats and proteins (creation of new glucose)
Classic signs/symptoms of diabetes mellitus (DM)
- polyuria
- polydipsia
- polyphagia
DM signs based on blood/urine testing
- hyperglycaemia
- glucosuria
- ketonuria
- fruity smelling breath (ketones)
Potential complications of diabetes mellitus
- Retinopathy - damage to retina
- Nephropathy - damage to kidneys
- Peripheral neuropathy - damage to peripheral nerves
- Peripheral tissue damage and poor wound healing and diabetic ulcers
Forms of cell signaling
Auto ring
Juxtacrine
Paracrine
Endocrine
Autocrine (local hormones)
A cell targets itself
Juxtacrine
A cell targets a cell connected by a gap junction
Paracrine
A cell targets a nearby cell
Endocrine
A cell targets a distant cell through the blood stream
ALARM phase of stress
Aka fight or flight
Immediate short term response to crises
- increased mental alertness
- increased energy use by all cells
- mobilization of glycogen and lipid reserves
- changes in circulation
- reduction in digestive activity/urine production
- increased sweat gland secretion
- increased heart/respiratory rates
Resistance Phase of Stress
Long term metabolic adjustments
- mobilization of remaining energy reserves
- conservation of glucose
- elevation of blood glucose concentrations
Exhaustion Phase
Collapse of vital systems
Causes include:
- exhaustion of lipid reserves
- inability to produce gluccocorticoids
- failure of electrolyte balance
- cumulative damage to vital organs
