pack Flashcards
What are the principal endocrine glands?
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid gland
Islets of pancreas
Adrenal gland
Gonads-testis and ovaries
What are other organs with endocrine functions?
Heart- ANP
Kidney- 1,25 dihydrocholecalciferol, erythropoietin
Live- 25 hydrocholecalciferol & somatomedins
Pineal gland- melatonin
Skin- calciferol
GIT-ghrelin gastrin, secretin, vasoactive intestinal peptide
What are the 4 trophic hormones of the anterior pituitary?
The four anterior pituitary tropic hormones are
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Thyroid-stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
What is the structure where hormones of the pancreas are released?
Median eminence
What are the two general classifications of hormones?
Local hormone- which have specific local effect e.g., secretin and cholecystokinin
General hormone- which affect almost all tissues of the body e.g., thyroid hormone, growth hormone
What are the chemical classification of hormones?
Classified into 3 groups:
- Steroid hormone (Derived from cholestrol) Ex: Progestrone and teststorone
- Polypeptide/Protein hormone: Polypeptides- Hypothalamic hormones, posterior pituitary hormones, parathyroid hormone, calcitonin, insulin etc.
- Derivatives amino acid Tyrosine e.g., Thyroid hormone, adrenal medullary hormones
What are the 3 locations where hormone receptors can be found?
- Membrane receptors: Protein, peptide, catecholamine
- In the cell cytoplasm: Steroid hormones
- In the cell nucleus: Thyroid hormone
What are the steps of a protein/peptide/catecholemine hormones to elicit an action inside the cell.
Summary: protein/peptide/catecholemine hormones cannot freely pass through the plasma membrane and therefore need a plasma membrane receptor which has a secondary messenger inside the cell.
Mechanisim:
The hormone binds to the membrane receptor. The membrane receptor then changes shape and binds to G protein which activates it.
The G protein then binds to GTP and releases GDP to get activated
The activated G protein then binds to adenylate cyclase in the membrane which converts ATP to cAMP
cAMP is the second messenger
cAMP can elicit actions on different protein kinases inside the cell
What are the steps of elicting a response using calcium?
- Hormone binds to membrane receptor
- Membrane receptor binds to G protein
- G protein binds to GTP and releases GDP
- G protein then binds to phospholipase C in the membrane (key difference)
- Phospholipase C then splits PIP2 into IP3 and DAG
- DAG activates various kinases on the membrane while IP3 releases calcium from the ER
- The released calcium alters the activity of specific enzymes and ion channels or binds to calmodulin
- Calmodulin also activates specific enzymes to amplify the cellular response
What are two ways in which receptors can be down regulated?
- Downregulation-Exposing cells to an excess of hormone for a sustained period typically results in a decreased number of receptors for that hormone per cell.
2.** Redistribution of receptors** from the cell surface to intracellular sites usually occurs as part of the process of downregulation.
What is a way in which receptors can e upregulated?
Upregulation may occur when an** increase in receptor** number compared with normal
What are the three ways in which hormone levels can be controlled?
Rate of secretion of hormone is controlled by one of the following mechanisms:
Negative feedback mechanism-
It is the main mechanism controlling hormonal level
It prevents overactivity of hormone secretion
It ensures a proper level of hormone activity at the target tissue
Feedback regulation occurs at all levels, including gene transcription, translation, synthesis and releasing of hormones
Positive feedback mechanism-
In a few instances when the biological action of the hormone causes additional secretion of the hormone e.g., release of oxytocin at the time of delivery
Direct control
In a few instances hormone secretion is regulated by blood concentration of substances which is controlled by the hormone e.g., secretion of insulin is promoted by serum glucose level
Explain the concept of cyclic variations in growth hormone release
Growth Hormone secretes in a pulsatile pattern
Factors related to a person’s state of nutrition or stress are known to stimulate secretion:
Starvation
Hypoglycemia or low concentration of fatty acids in the blood
Exercise
Excitement
Trauma
Ghrelin (hunger hormone) secreted by the stomach before meals
What are the two methods of transport of hormones in the blood?
Water-soluble hormones (peptides and catecholamines): Dissolved in the plasma
Steroid and thyroid hormones
Circulate in the blood mainly bound with plasma proteins
Less than 10 percent in the plasma exist free in solution
Biologically inactive until dissociated from plasma proteins and slows their clearance from the plasma
Serves as a reservoir
What is the formula for the Metabolic Clearance Rate (MCR)?
MCR= Rate of disappearance from the plasma (mg per minute)/Plasma Concentration (mg per ml)
What are the different types of assays and how are they done?
Biological assay: You expose the living system to the drug or substance and observe the effect. (Like injecting a rat with an unknown substance and observing whether it dies or not)
Chemical assay:You use chemical reactions to detect and quantify molecules. (Like the ph strip for water)
Immunological assay: it uses the principle of antigen-antibody binding. You design an antibody that specifically recognizes your target (like a virus protein), and then you use that to detect or measure it.
What are the two types of chemical assays?
Qualitative-extraction, distillation precipitation and other methods that determine physicochemical properties
Quantitative-volume or weight of a substance
